US 11022421

I'll search for this specific patent number across USPTO and court docket sources.

Let me dig further into litigation and docket sources.

Let me check for litigation/docket activity and retrieve the claims.

US 11,022,421 B2 — Search & Summary

Search note / confidence statement: I ran targeted queries against USPTO-derived and court-docket sources. The patent itself is well-documented. I found no evidence of any CAFC 2026 appeal or docket activity involving 11022421 — the CAFC 2026 search returned only an unrelated nonprecedential opinion (Guardant Health). I cannot confirm the absence of litigation with certainty, but nothing in the results ties this patent to a 2026 Federal Circuit matter. The claim numbering below is my own reconstruction from the patent's claim-language passages; I did not retrieve a literal, numbered claims section, so treat the numbering as provisional and the wording as near-verbatim rather than exact.

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Bibliographic data (from the granted patent front page)

Abstract (verbatim)

"A medical system tracks the position of a medical instrument within a body of a patient. The medical instrument includes an electromagnet structure having an inductor coil wound around a core. A control circuit applies a low frequency excitation signal across the inductor coil. The inductor coil and the core generate a magnetic field. A plurality of sensors sense parameters of the generated magnetic field and produce sensor signals. The control circuit calculates the position of the medical instrument based on the produced sensor signals."

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Independent claims — plain-language overview

Claim 1 — System (medical instrument + control circuit + sensor).
A system where a medical instrument sized for insertion into a patient carries a first core with a first inductor coil wound around it. A control circuit drives current through the coil by applying an excitation signal below 10,000 Hz; the coil-plus-core generate a magnetic field from that current. A sensor detects the magnetic field and returns a sensor signal to the control circuit, which computes position information for the instrument inside the patient's body from that signal. (Dependent disclosure adds: frequency <500 Hz, about 330 Hz; instrument is a tube/catheter; implantable; position/orientation/motion output and video signal to a display; insulated wire; core thickness <0.020 in.)

Claim 2 — Low-frequency electromagnetic trackable structure.
A structure having a core formed on the distal end of a medical instrument (the distal end being the part arranged for insertion into the body), with an inductor coil wound around the core. The coil receives an excitation signal below 10,000 Hz and the structure emits a trackable magnetic field in response. (Dependents: ~330 Hz; the instrument is a PICC; a bio-compatible surface coating; a needle in which the core is integrated into a first ferromagnetic-material portion.)

Claim 3 — Method of tracking.
Advance a medical device into the patient's body, the device bearing a low-frequency electromagnetic apparatus having at least one ferromagnetic core and a conductor split into (a) coils wound around the core and (b) first and second conductive leads. Apply a low-frequency excitation signal to the leads, detect in real time from outside the body the magnetic field the apparatus produces, and present visual information tracking motion of the device inside the body based on that detection. (Dependents: signal below 500 Hz; core cross-section ~0.005–0.250 in., or ~0.00025–0.05 in.)

Claim 4 — System for detecting instrument position (electromagnet framing).
A system in which the medical instrument includes an electromagnet that facilitates tracking, the electromagnet comprising a core and an inductor coil wrapped around the core. The control circuit passes current through the coil via a low-frequency excitation signal; the coil generates a magnetic field; a sensor senses it and outputs a sensor signal; the control circuit then determines one or more of position, orientation, and motion of the instrument within the patient from that signal.

Claim 5 — Method of tracking (core/coil generation framing).
Generate a magnetic field by passing current through an inductor coil wound around a core, where the current is applied as a low-frequency excitation signal under 10,000 Hz (preferably under 500 Hz); the coil and core sit on a medical instrument positioned in the patient's body. Sense the field with a sensor, generate a sensor signal from it, and determine position, orientation, and/or motion of the instrument from the sensor signal.

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Technical gist

The patent's stated problem: ferrous materials, the earth's magnetic field, and 50/60 Hz line-related interference make small-coil electromagnetic tracking unreliable, and DC excitation causes whole-core saturation/steady fields that are hard to distinguish from ambient fields. The disclosed solution uses low-frequency AC excitation (notably ~330 Hz, chosen deliberately below 500 Hz and away from integer multiples of 50 Hz and 60 Hz, with 300 Hz expressly noted as a multiple of both) to exploit skin-depth penetration of the ferromagnetic core, producing flux gains stated as tens-to-thousands of times over an air-core equivalent and enabling tracking up to ~65 cm. Supporting detail covers core materials (steel 1080 "piano wire," stainless steel 304V, Permendur, Mu-metal, ferrite), wire/coil dimensions on the order of thousandths of an inch, multicore and "sundered" cores, excitation waveforms (square, sine, spike/pulse, FSK-style multi-frequency signatures for distinguishing multiple instruments), hysteresis/saturation behavior, and a six-sensor (three orthogonal pairs, differential) magnetoresistive sensor head with the SNR scaling relationship n^(1/2)·d^(3/2)·f·B₀·BW^(−1/2).

Sourcing

• Granted patent front page and abstract: https://patentimages.storage.googleapis.com/c1/59/59/d918bcc3df4513/US11022421.pdf
• Google Patents record (priority/filing, classifications, legal status): https://patents.google.com/patent/US11022421/en
• Pre-grant publication text (claim-language and specification passages): https://uspto.report/patent/app/20190025040 and https://www.freepatentsonline.com/y2019/0025040.html
• International counterpart: WO2017127722A1 / EP3405109A4

Uncertainty flags: (1) I did not retrieve the literal numbered claim set, so claim numbering/dependencies above are reconstructed from claim-language passages in the record — verify against the USPTO PatentCenter claims before relying on them. (2) No CAFC 2026 docket reference for 11022421 was found; my litigation search returned no results for this patent, so I am reporting an absence of evidence rather than evidence of absence. (3) The search result for "US patent 11022421" returned zero hits from my first query, so all bibliographic data above comes from the Google Patents/patent-PDF sources cited.

I'll search for litigation involving US patent 11022421 across patent litigation databases.

The initial searches returned irrelevant results. Let me search more targeted litigation databases.

Those results concern Lucent Technologies, not Lucent Medical Systems. Let me search more specifically for this patent and its assignee.

Findings: Litigation involving US Patent 11,022,421

Summary: I found no evidence of any patent litigation asserting or involving US Patent 11,022,421 ("Low-frequency electromagnetic tracking," assignee Lucent Medical Systems Inc.).

What I searched

I ran queries against general web/patent-litigation indexes looking for the patent number in connection with lawsuits, plus assignee-based searches (e.g., "Lucent Medical Systems" as plaintiff against potential defendants). Specific queries included the patent number alone, the number in quoted form, and the number combined with "infringement complaint" / "lawsuit" / "defendant."

What came back

• No hits tied the patent number 11,022,421 to any district court, ITC, or Federal Circuit proceeding.

• Results containing the string "11022421" were false positives unrelated to this patent — e.g., a hydraulic "swashplate bearing kit" part number and a cable catalog entry. Per your literal-interpretation rule, I did not treat those as the patent.

• Searches for the assignee surfaced only Lucent Technologies (an unrelated telecom entity, subject of Lucent Techs. v. Microsoft/Gateway and Data Race v. Lucent Technologies) and trademark/TTAB matters involving Lucent Medical Systems, Inc.:

  • Stryker Corporation / Sage Health Management Solutions, Inc. v. Lucent Medical Systems — USPTO TTAB, filed Feb. 13, 2018, status Terminated (trademark, not patent).
  • Lucid, Inc. v. Lucent Medical Systems, Inc. — USPTO TTAB Opposition No. 91118707 (trademark, not patent).

  Neither involves the '421 patent.

Requested table

Important caveats and confidence

• Confidence level: moderate. I could not access the litigation-specific databases you named directly (Unified Patents litigation portal, PACER, RPX Insight) in this session, and my general web searches did not surface any case. It is therefore possible that litigation exists but is not well-indexed by the sources I could reach.
• The patent is relatively recent (granted June 1, 2021; priority Jan. 20, 2016) and its assignee, Lucent Medical Systems Inc., is a small medical-device company. It is entirely plausible that the patent has simply never been asserted.
• I recommend confirming with authoritative sources before treating this as definitive:
  • Unified Patents litigation portal: https://portal.unifiedpatents.com/litigation/caselist
  • USPTO Patent Center / Patent Assignment records for the '421 patent
  • PACER docket search (party name "Lucent Medical Systems, Inc.")
  • Docket Navigator or RPX Insight (patent-specific docket search)

Conclusion: Based on the searches performed, there is no known litigation involving US Patent 11,022,421. If litigation is ongoing but not publicly indexed, it would not appear in these results.

I'll start by verifying the structured data against live sources, since the prompt explicitly asks me to check for proceedings the ODP ingest may have missed.

Generic searches returned unrelated hits. Let me run targeted queries against PTAB dockets, the patent owner, and litigation-driven filings.

Let me run a final set of targeted checks on PTAB dockets, related-family patents, and any litigation that would typically trigger an IPR.

Proceedings overview

Total AIA trial proceedings on file for US 11,022,421: zero (0). The structured "PTAB proceedings on file" block — sourced from the USPTO Open Data Portal — returns no IPR, PGR, or CBM for this patent, and my independent web checks (PTAB decision/petition text, patent-owner name searches, and family-level searches) surfaced no AIA trial proceeding naming US 11,022,421 as the challenged patent. There is therefore no proceeding that invalidated claims, no proceeding that sustained claims, and nothing settled or instituted.

The defensive posture this gives a defendant is neutral-to-favorable but not "hardened": the patent has not survived an IPR — it has simply never been tested at the Board, because no petitioner has ever filed. A patent that has never been IPR'd carries no estoppel baggage for you, but it also carries no PTAB-tested narrowing and no cancelled claims to shelter behind. Every one of the 19 issued claims is live and untested, and the full universe of prior art under §§ 102/103 remains available to you both at the Board and in district court.

Important caveat on scope. The ODP block is the canonical list and it shows nothing; my web verification was consistent with that. This is an affirmative finding of "no PTAB activity," not proof that no petition has ever been filed — PTAB filings can lag public indexing. Verify directly in PTAB E2E (https://ptacts.uspto.gov/ptacts/public-informations) and via the USPTO Patent Center "PTAB proceedings" tab for application 16/071,891 before relying on this in a case-management or § 315(b) analysis.

No proceedings to report

There is no IPR, PGR, or CBM entry to walk through — accordingly, there is no petitioner, no judge panel, no institution decision, no Final Written Decision, no termination, and no Federal Circuit appeal to describe. I will not manufacture proceeding numbers, APJ names, or dispositions to fill this section. Anything of that kind would be fabrication.

False positive to discard. A search for "Lucent Medical Systems" plus PTAB-adjacent terms returns Stryker Corporation / Sage Health Management Solutions, Inc. v. Lucent Medical Systems — a Trademark Trial and Appeal Board extension-of-time matter (filed 2018-02-13, now terminated) at https://www.law360.com/ttab_cases/5a83b4bd2db3ac2a61000080. That is the TTAB, not the PTAB, and it is not an AIA trial. Do not cite it as PTAB activity on the '421 patent. Several other hits (PTAB petitions quoting Fintiv/Sotera boilerplate, uspto.report and freepatentsonline application pages) are search noise — they reference the '421 patent's publication US2019/0025040A1 or its prosecution documents, not a trial.

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Strategic summary

Claim status — the honest answer is "all untested." US 11,022,421 issued 2021-06-01 with 19 claims (per the face of the patent). Because no AIA trial has ever reached even an institution decision, none of claims 1–19 is cancelled, none is statutorily disclaimed via a PTAB adverse judgment, and none has been adjudicated unpatentable or patentable by the Board. There is consequently no narrowing claim set to report as "sustained," and no "claim 1 is dead" hook for a defendant to exploit. Contrast this with a patent that has been through an IPR: there you get free § 315(e)(2) estoppel and a Board-blessed invalidity roadmap. Here you get neither.

Estoppel landscape — clean slate. Because there has been no IPR, no petitioner is estopped under § 315(e)(2), and by the same token there is no petitioner-side winning record for you to borrow. For you as a defendant: (a) every ground — § 102, § 103, and § 112 — is still raisable, at the Board and in court; (b) no printed-publication or system-art ground has been "burned" by a prior petitioner; (c) your § 315(b) clock runs one year from service of a complaint alleging infringement of the '421 patent (or a complaint on a same-family patent, if the patent owner uses that as a vehicle), so if you have already been served, calendar that date immediately. Note also the effective filing date is post-AIA (earliest provisional 2016-01-20), which makes this patent a poor CBM candidate — CBM review is confined to patents claiming a covered business method with a pre-AIA effective filing date, so plan on IPR as your forum, not CBM. The PGR window (9 months from issuance) closed on 2021-12-01; only IPR remains available at the Board.

Pattern signals — no pattern, and that itself is informative. There is no repeat petitioner, no defensive aggregator (no Unified Patents, RPX, or similar) visible in the chain, and no Federal Circuit appeal activity on this patent. The patent owner, Lucent Medical Systems, Inc. (Kirkland, WA), holds a small, coherent post-AIA portfolio built on the same low-frequency electromagnetic tracking disclosure — notably US 11,027,096 ("Flexible circuit bearing a trackable low-frequency electromagnetic coil," issued 2021-06-08) and subsequent grants, together with a European counterpart family (EP 3405109 via PCT/US2017/014395). The absence of any IPR is a mild signal, not a strong one: it is consistent with a patent that has not been asserted against a well-capitalized defendant with the incentive to file. It should not be read as evidence that the claims are strong. The claims' concentration on mechanical/electrical parameters — core diameter, coil diameter, turns per inch, excitation frequency "below 10,000 Hz," "about 330 Hz" — is exactly the kind of quantitative-recitation subject matter that invites § 103 "design choice / optimization of a known parameter" attacks under In re Aller–type reasoning, so the absence of an IPR is more likely attributable to litigation posture than to impenetrable claims.

Practical read for a defendant today. If you received a demand letter citing this patent, the letter writer is relying on an entirely untested patent — that cuts both ways. You have the complete prior-art field to work with and no estoppel against you, but you also cannot point to a cancelled claim to moot their theory. And if their letter cites the '421 patent while their real commercial muscle is in the sibling patents (the '096 flexible-circuit patent or later family members), watch for a substitution or joinder move.

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Recommended next steps

If you are a defendant and are evaluating invalidity:

• There is no FWD to link to and no disposition to quote — I will not invent one. The correct first move is to confirm the negative: pull the PTAB E2E record for the patent (https://ptacts.uspto.gov/ptacts/public-informations) and the Patent Center litigation/PTAB tab for application 16/071,891, and run a docket sweep (Docket Navigator or RPX) on both the patent number and the assignee, Lucent Medical Systems, Inc., plus the inventors Samuel Peter Andreason and Gary Brian Sanders.
• Because no IPR exists, prepare your own § 311 petition strategy. The most promising statutory hook on the face of the disclosure is § 103 over the permanent-magnet localization art the patent itself cites and distinguishes — Golden et al. (US 5,425,382; US 5,622,169; US 5,902,238), Haynor et al. (US 5,879,297; US 6,129,668; US 6,216,028; US 6,263,230), and Silverstein et al. (US 5,775,322) — combined with ordinary-skill AC electromagnet/coil design knowledge. The patent's own admission that the low-frequency limitation is a known trade-off (deeper core penetration vs. faster response, and the express note that "an air core device will generally require a much higher excitation frequency") is useful § 103 material.
• Calendar the § 315(b) bar. One year from service of the first complaint alleging infringement of this patent. Missing it forfeits your IPR option entirely — and here that option is fully intact and unused.
• Consider a pre-emptive declaratory-judgment posture. With no IPR on file and the patent unasserted, you may have a cleaner DJ action for invalidity/non-infringement in a favorable venue than a defendant in active litigation. Coordinate the DJ filing with any IPR timing so the Fintiv / § 325(d) discretionary-denial factors work in your favor rather than against you.

If active proceedings appear later: an instituted IPR gives the Board a statutory one-year deadline from institution to FWD (§ 316(a)(11)), with institution decisions due ~6 months from petition filing, an oral hearing typically ~2–3 months before the FWD deadline, and a 3-month § 318 FWD-to-issue window. Set those milestones the moment an institution decision issues.

Bottom line: There is no PTAB activity on US 11,022,421 as of the most recent ODP ingest, and web search produced no older or newly-filed AIA proceeding the ODP had missed. For a defense team, that means no cancelled claims, no Board-tested invalidity record, and no § 315(e)(2) estoppel — you start from a clean slate with a fully live 19-claim patent and the entire prior-art field available. Verify the negative in PTAB E2E before you take a position on the record.

I'll research the assignment record for US 11022421 before building the report.

Assignment / Ownership Analysis — US 11,022,421 B2 ("Low-frequency electromagnetic tracking")

Verification status up front. I was able to confirm the existence and content of the recorded post-filing assignment events for this patent via Google Patents legal events and the patent's own front-page data (source: https://patents.google.com/patent/US11022421/en). I was not able to retrieve reel/frame numbers or correspondent-of-record data: the Assignment Center and the legacy assignment.uspto.gov index are JavaScript-driven and were not exposing that metadata to the search tooling available to me. I am therefore not supplying reel/frame numbers or correspondent names rather than risk fabricating them. The date/assignor/assignee content below is real; the reel/frame field is a documented gap, not an estimate. Anyone re-running this should pull reel/frame directly at https://assignmentcenter.uspto.gov/ (search "11022421") and https://assignment.uspto.gov/patent/index.html.

Inventors

Grounding: the issued patent's front page (71)/(72)/(73) fields list Applicant Lucent Medical Systems, Inc., Kirkland, WA, inventors Andreason and Sanders, both of Kirkland, WA, and Assignee Lucent Medical Systems, Inc., Kirkland, WA. The matching city strongly indicates both inventors were company personnel at filing; the application was filed by the company as applicant (PCT/US2017/014395), which is the ordinary operating-company pattern rather than an inventor-held-then-assigned pattern.

Unusual-pattern check: no signal. I found no evidence of inventor departure, no evidence of a post-filing re-assignment by the inventors to a third party, and no counterpart assignment chain indicating the inventors retained or resold rights. This check is therefore unclear/not determinable on the evidence retrieved — not negative. Note however that a third-party patent-data aggregator (GoodIP, https://goodip.io/iq/assignee/lucent-medical-systems-inc) attributes 8 patents to Andreason and 4 to Sanders, i.e. both inventors continued to produce filings for the same assignee — which cuts against the "inventors walked away, portfolio got fire-sold" pattern.

Original assignee

Lucent Medical Systems, Inc., Kirkland, Washington, USA — named as both applicant and assignee on the issued patent.

• Primary line of business: medical device / medical instrument tracking. The patent's own classifications support this: A61B5/06 and A61B5/062 ("determining position of a probe within the body … using magnetic field"), A61B34/20 (surgical navigation), A61M31/00 (devices for introducing media into cavities of the body), and A61B2090/3954 (magnetic markers). The disclosed embodiments are tubes, catheters, PICCs, stylets, needles and implants with an embedded inductor-coil/ferromagnetic-core electromagnet.
• Name-confusion warning: this is not Lucent Technologies / Alcatel-Lucent / Nokia. The assignee of record here is a single-site Kirkland, WA medical device company. Every "Lucent v. …" litigation hit my searches returned was the telecom company and is irrelevant to this chain. Do not let the shared stem pollute the NPE screen.
• Product embodying the claims: I have moderate, not high, confidence that Lucent Medical Systems commercialized an electromagnetic tracking system for guided placement / confirmation of enteral feeding tubes and similar indwelling tubes. I could not verify a shipped product from the sources retrieved in this run, so treat this as unconfirmed rather than established.
• Current status: operating, on the evidence available. The company continued prosecuting a related family after this patent — Google Patents cross-listings show US 11,027,096 B2 (2021-06-08), US 11,234,769 B2 (2022-02-01) and US 11,426,133 B2 (2022-08-30), all assigned to Lucent Medical Systems, Inc. A dissolved or wound-down entity does not keep issuing patents. No record of acquisition, merger, or bankruptcy was found — that is a negative finding on this evidence, not proof of absence.

Assignment timeline

Two recorded events, both conveyances to the original assignee, both recorded in February 2019 during national-stage entry of the PCT (filing date 2017-01-20; US national-stage application 16/071,891; US publication 2019-01-24). Google Patents legal events characterize both as "ASSIGNMENT OF ASSIGNOR'S INTEREST."

• 2019-02-15 (executed date not exposed) / recorded 2019-02-15 — Reel not retrieved (see verification note)

  • Conveyance: Assignment (assignment of assignor's interest)
  • Assignor: Andreason, Samuel Peter; Sanders, Gary Brian
  • Assignee: LUCENT MEDICAL SYSTEMS, INC. (Kirkland, WA)
  • Correspondent: not retrieved — Assignment Center/PEDS correspondent field was not accessible to my searches. Flagging per your instruction rather than guessing; on this chain there is only one assignee, so the repeat-correspondent test cannot be run at all.
  • Context: confirmatory inventor-to-company assignment at PCT national-stage entry — routine housekeeping, not a transfer of ownership to a new party.

• 2019-02-20 (executed date not exposed) / recorded 2019-02-20 — Reel not retrieved

  • Conveyance: Assignment (assignment of assignor's interest)
  • Assignor: Andreason, Samuel Peter; Sanders, Gary Brian
  • Assignee: LUCENT MEDICAL SYSTEMS, INC. (Kirkland, WA)
  • Correspondent: not retrieved (same caveat)
  • Context: second, near-identical recording five days after the first, same assignor/assignee pair. Consistent with a duplicate or corrective recording to cover a second application in the family (provisional 62/281,155 and/or the PCT), or a re-recording for the national stage. Precise provenance is not determinable from the data retrieved. Note that the content of the two records is identical — this is not a transfer between different parties.

There are no recorded post-issuance assignments. Nothing moves the patent out of Lucent Medical Systems, Inc. after issuance on 2021-06-01. That absence is itself the principal finding of this report.

Timeline diagram

timeline
    title Ownership of US 11022421
    2016 : Provisional filed Jan 20
    2017 : PCT filed by Lucent Medical Systems
    2019 : Assigned to Lucent Medical Systems
         : Second confirmatory assignment recorded
    2021 : Patent issued Jun 1

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. There is no recorded transfer from an operating assignee to a licensing-only entity. Both records move rights to the operating company from its own inventors (recorded 2019-02-15 and 2019-02-20). No "IP / Patents / Licensing / Holdings / Ventures" assignee appears anywhere in the chain.
2. Known asserter in the chain — Not present. Lucent Medical Systems, Inc. does not match Acacia, Marathon Patent Group, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or any Spangenberg entity. The only superficially alarming feature is the token "Lucent," which belongs to the unrelated telecom company; the assignee of record is expressly "Lucent Medical Systems, Inc., Kirkland, WA."
3. Repeat correspondent across the chain — Unclear / not determinable. Correspondent-of-record data could not be retrieved for either 2019 recording. I decline to name an attorney without the record. With a single assignee and a two-day gap between recordings, this signal could not produce a finding even if populated — recurrence requires at least two distinct links.
4. Cascading transfers — Not present. Two recordings in five days, with an identical assignor and identical assignee, are the opposite of cascading. No chained LLCs, no shared registered-agent addresses, no serial conveyances.
5. Pre-litigation transfer — Not present. No infringement action naming US 11,022,421 was found in my searches, so the six-month-before-suit test has no anchor date. No assignment has been recorded at all since 2021-06-01, which forecloses a pre-suit transfer as presently recorded.
6. Bankruptcy fire-sale — Not present on available evidence. No Chapter 7/11 proceedings involving Lucent Medical Systems, Inc. were surfaced, and the company's continued issuance of related patents in 2021–2022 (US 11,027,096; US 11,234,769; US 11,426,133) argues against a distressed wind-down.
7. Privateering — Not present. No operating-to-NPE transfer, no SEC-disclosed privateering arrangement, no Patent Progress / EFF coverage found.
8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. Ownership remains with the original operating company.

Verdict

Insufficient data. The only recorded assignments are the two confirmatory inventor-to-assignee conveyances to Lucent Medical Systems, Inc. (recorded 2019-02-15 and 2019-02-20), with no post-issuance transfer of any kind after the 2021-06-01 grant. That profile — original operating assignee still holding the patent, continued related filings through 2022 — is affirmatively inconsistent with an NPE chain, but it is also thin enough that I will not upgrade it: I could not retrieve reel/frame numbers or correspondent-of-record, could not verify a commercial product, and found no litigation to test the assertion posture. On the present record the patent reads as a clean operating-company asset, and none of the eight NPE signals is present; the residual uncertainty is evidentiary, not substantive.

Verify directly: https://assignmentcenter.uspto.gov/ (patent number query "11022421") and the legacy index at https://assignment.uspto.gov/patent/index.html. Both draw on the same underlying reel/frame records.

I'll research this systematically. Let me start by pulling the patent's own citation records and cross-checking with USPTO sources.

Good initial leads. I found a Justia page listing citations, but I need to disambiguate "References Cited" (front-page references) from "Referenced By" (later citing patents), and confirm which references the examiner actually applied. Let me dig deeper.

Prior-Art Analysis — US 11,022,421 B2 ("Low-frequency electromagnetic tracking")

0. Patent identification and verification

I verified that the number 11022421 resolves to exactly one U.S. patent; I did not substitute any similar number.

Note on a false positive I rejected. A query for "11022421" also returns a hydraulic "swashplate bearing kit" part number 11022421 (Sauer-Danfoss/Series 45 parts catalog, alpha‑hydraulics.ru) and unrelated catalog entries. Per the literal-interpretation rule, I did not treat those as this patent. Separately, the EPO search report at data.epo.org .../EP3424447NWA1/document.pdf cites WO 2012/109621 (Actuated Medical), US 2008/249467 (Burnett), WO 2010/045158 (Piezo Resonance), US 2015/073357 (Bagwell) and US 6,423,014 (Churchill) against claims "1–15" under IPC A61B 17/34 (trocars/needles). That classification and subject matter do not match the '421 patent (G01B 7/004 / A61B 34/20), so I did not attribute EP3424447 to this family — flagged as unverified.

Important scope/caveat up front. The authoritative full text you supplied is my primary source; it contains the applicant-cited "Description of the Related Art" references in full. For the front-page (56) "References Cited" list, I retrieved a partial list from Justia and the "Other Publications" list, but I could not open the USPTO Patent Center file wrapper or the ISR for PCT/US2017/014395 itself before hitting the search limit. I therefore mark unverified items explicitly rather than presenting them as confirmed examiner citations.

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1. Part A — References cited in the patent's own specification (verified, authoritative)

These ten U.S. patents are discussed and expressly incorporated by reference in the '421 specification (¶¶ [0005]–[0013] of the published application). All were cited as background, not as rejections.

† = issue date recalled from prior knowledge; not individually re-verified against USPTO/Google Patents in this session. Filing dates were not retrieved. Please verify at https://patents.google.com/patent/US<number>A/en. I did not find any source contradicting these dates.

URLs (constructible and stable): https://patents.google.com/patent/US5425382A/en, .../US5622169A/en, .../US5775322A/en, .../US5879297A/en, .../US902238A/en (US 5,902,238), .../US6129668A/en, .../US6173715A/en, .../US6216028A/en, .../US6263230A/en, .../US6292680A/en.

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2. Part B — U.S. patent documents on the front-page citation list (partially verified)

Retrieved from the Justia citation listing (https://patents.justia.com/patent/11022421). I could not determine the exact cut-off between "References Cited" and "Referenced By" for every entry, so treat the 2017-published entries as likely "Referenced By" (they post-date the 2017-01-20 filing).

US patents: RE42913 (Wild et al., 2011-11-15); 8,197,494 (Jaggi et al., 2012-06-12); RE43681 (Wild et al., 2012-09-25); 8,265,732 (Besz et al., 2012-09-11); RE43952 (Uhl et al., 2013-01-29); 8,478,382 (Burnside et al., 2013-07-02); 8,606,347 (Besz et al., 2013-12-10); 8,644,907 (Hartmann et al., 2014-02-04); 8,781,555 (Burnside et al., 2014-07-15); 8,830,112 (Buehler et al., 2014-09-09); 8,934,960 (Besz et al., 2015-01-13); 9,028,441 (Kuhn, 2015-05-12); 9,061,139 (Stevenson, 2015-06-23); 9,131,956 (Shaughnessy et al., 2015-09-15); 9,579,488 (Shaughnessy et al., 2017-02-28); 9,585,599 (Besz et al., 2017-03-07); 9,687,174 (Jaggi et al., 2017-06-27).

US published applications: 2002/0043561 (Tsikos); 2002/0165448 (Ben-Haim); 2003/0006759 (Govari); 2003/0173072 and 2003/0192691 / 0192693 / 0196801 / 0196810 and 2003/0201098 (Vinegar / Karanikas / Wellington); 2003/0183390 (Veenstra); 2003/0205378 and 2004/0040715 (Wellington); 2004/0087877 (Besz); 2004/0106449 (Walker); 2006/0084867 (Tremblay); 2007/0085681 (Sawyer); 2007/0096852 (Lawrence); 2008/0004663 (Jorgenson); 2009/0171190 (Uchiyama); 2011/0098559 (Besz); 2012/0130228 & 2012/0130229 (Zellers); 2012/0226148 (Jaggi); 2012/0245457 (Crowley); 2012/0253340 (Stevenson); 2013/0169272 (Eichler); 2014/0051983 (Schroeder); 2014/0188422 (Huber); 2014/0196723 (Kirkpatrick); 2014/0310594 (Ricci); 2015/0238388 (Kuhn); 2016/0067148 (Nordquist); 2017/0128701 (Shaughnessy); 2017/0143235 (Besz).

§ 102 note: The Besz / Burnside / Jaggi / Shaughnessy / Stevenson family (Lucent Medical Systems' own earlier portfolio, e.g., EP 2 249 273 / US 8,265,732) is the closest-in-field material in this group — it concerns medical device position guidance using magnetic fields. However, per the portions I retrieved these teach permanent-magnet (passive field-source) guidance with sensor-based detection, not a core + inductor coil inside the instrument driven by a sub-10 kHz excitation signal. On that basis they do not anticipate independent claims 1, 11, or 17. I could not inspect each of these ~50 documents individually in this session — this table is a lead list, not a completed § 102 clearance.

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3. Part C — Foreign patent documents and Part D — Non-patent literature

Foreign patent documents (front page): AU 2009202733 (2013-07); AU 2011258874 (2015-04); CA 2 649 802 (2008-05); CA 2 684 471 (2008-10); CA 2 701 169 (2009-04); DE 27 49 677 (1998-11); EP 0 555 131 (1993-08); EP 1 744 184 (2007-01); EP 2 249 273 (2012-07); FR 1459499 (1966-11); GB 1605299 (1988-07); GB 2379469 (2004-09); GB 1605446 (2005-08); KR 10-1499975 (2015-03); SG 184736 (2012-10); WO 01/61917 (2001-08); WO 03/040513 (2003-05); WO 2006/116122 (2006-11).
(Interpreted literally; GB 2379469/GB 1605446 numbering is reproduced as listed, not corrected.)

Independently corroborated: Espacenet's citing-documents page for EP 2 249 273 B1 lists Andreason/Sanders / Lucent Medical Systems / US 2019/0025040 / US 11022421 / priority 2016-01-20 — consistent with the family linkage above.

Non-patent literature (front page) — the metallurgy/magnetics cluster is highly probative of § 103, not § 102:

• International Search Report, dated 2017-04-07, for PCT/US2017/014395 (2 pages) — this is the ISR for the '421 application; its contents (X/Y citations) are the single most important document I could not retrieve.
• Sacolick et al., "Electromagnetically tracked placement of a peripherally inserted central catheter," SPIE Medical Imaging Proceedings, 2004 (5 pp.). ← closest NPL to claim 13 (PICC) / claim 1
• Carpenter Technical Articles, "Magnetic Properties of Stainless Steels," Jun. 2006
• Cheney, "Preparation and Properties of Pure Iron Alloys: II …," Scientific Papers of the Bureau of Standards 18:609–635, 1922
• Cobalt Development Institute, Cobalt Facts, 2006, Ch. 5 "Magnetic Alloys," pp. 23–28
• Jiles et al., "Investigation of the Microstructural Dependence of the Magnetic Properties of 4130 Alloy Steels and Carbon Steels for NDE," Review of Progress in QNDE 6A, 1987, 1681–1690
• Landgraf et al., "Magnetic Properties of Silicon Steel Wires," Soft Magnetic Materials 16:439–443, 2003
• Medvedeva et al., "Magnetism in bcc and fcc Fe with carbon and manganese," J. Phys.: Condens. Matter 22:316002, 2010
• Virjoghe et al., "Finite Element Analysis of Stationary Magnetic Field," in Finite Element Analysis — New Trends and Developments, IntechOpen, 2012, 101–130
• Wikipedia, "Demagnetizing field," archived 2015-10-01
• Amphenol RF, "Frequency Range Chart," archived 2015-11-09
• CWS ByteMark, "Ferrite Rods, Bars, Slugs, Plates and Tubes," 2012-08-30
• HSM Wire International, "Insulation Film Enameled Guide," 2013
• Bulk Wire, "Wire Gauge Reference Table," 2013

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4. Consolidated § 102 analysis

Under AIA § 102(a)(1)/(a)(2) (application filed 2017-01-20), anticipation requires a single reference disclosing every element of an independent claim. The three independent claims require:

Finding: none of references A1–A10 (the references the applicant cited in the specification) anticipates any claim of the '421 patent. Every one of them is a passive permanent-magnet system: the field source on the instrument is a static magnet, and the external device is a magnetometer/detector, not a control circuit that energizes a coil in the instrument. Concretely:

• Element "core + inductor coil on the instrument" is wholly absent from A1–A3, A5, A7, A9, A10 (permanent magnets only) and absent from A4, A6, A8 (sensor-side hardware, magnet source).
• Element "excitation signal below 10,000 Hz" has no counterpart anywhere in A1–A10 — they measure static fields/gradients and invert dipole equations; no AC drive of an in-body coil is disclosed.
• A4/A6/A8/A9's iterative predicted-vs-actual error-function processing maps conceptually onto the '421's "calculate position information … based on the sensor signal," but that is at most a § 103 combination candidate paired with an active-coil reference — not anticipation.
• The Earth's-field-cancellation technique of A8 (subtracting sensor sets) is conceptually adjacent to the '421's stated motivation for low-frequency AC (¶ [0064]), but again is static-field art.

Because each independent claim contains the active, low-frequency-driven in-body electromagnet limitation as an integral element, no cited reference can anticipate; the strongest possible rejection on this art is a § 103 combination, and the examiner evidently did not make one (the patent issued 2021-06-01 without such a rejection appearing).

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5. Closest non-cited art I identified while searching (flagged — NOT confirmed as citations on the '421 patent)

These surfaced in searching but I did not verify them as appearing on the '421 face or in its ISR. Treat as leads only:

1. US 7,761,100 B2 — Anderson (General Electric), "Ultra-low frequency electromagnetic tracking system," filed 2006-07-14 (CIP of 10/611,112), issued 2010-07-20. Teaches EM position/orientation tracking in medical procedures with the emitted signal below the AC utility frequency (i.e., well under 10,000 Hz) to reduce eddy-current distortion ("skin depth" tables for Al and Ti at 25/100/400/1600/14000 Hz). This is the most textually on-point reference I found for the "frequency below 10,000 Hz" limitation, but its architecture is an external transmitter coil array with a receiver on the instrument — the inverse of claim 1 — and it does not disclose a core+coil electromagnet on the medical instrument. So even it would not anticipate claim 1 as a whole; it is a strong § 103 candidate. Source: patentimages.storage.googleapis.com/35/d5/a6/9085c9e9991319/US7761100.pdf.
2. US 9,086,469 B2 — Perkins et al. (Awarepoint), "Low frequency magnetic induction positioning system and method," filed 2013-03-11, issued 2015-07-21. Low-frequency magnetic-induction ranging/positioning, but for asset/personnel tags in a facility, not an in-body instrument electromagnet. § 102 inapplicable; § 103 tangential.
3. CN 103217682 A (Hangzhou Huayun Tianyue), "Target location and tracking system and method based on low-frequency electromagnetic wave" — 80–150 kHz, far above the claimed range.

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6. Gaps and recommended verification (explicit confidence statements)

• Confidence: high that A1–A10 are cited in the '421 specification and that none anticipates any claim (the instruments in all ten carry permanent magnets, not driven coils).
• Confidence: moderate on the composition of the front-page (56) lists in Part B/C/D — I retrieved them from Justia but could not fully separate "References Cited" from "Referenced By," nor verify every date.
• Confidence: moderate on the A1–A10 issue dates (marked †); filing dates were not obtained.
• Not retrieved / material gap: the content of the ISR dated 2017-04-07 for PCT/US2017/014395, and any non-final/final Office Actions on US 16/071,891. These are the documents that would state whether the examiner applied any X/Y reference under § 102 or § 103.
• Recommended next steps (authoritative only): USPTO Patent Center for application 16/071,891 (file wrapper, ISRs, Office Actions) at patentcenter.uspto.gov; WIPO Patentscope for PCT/US2017/014395; Espacenet "References cited / Citing documents" for the family; Google Patents https://patents.google.com/patent/US11022421B2/en "References Cited" and "Cited By" tabs.

Bottom line: On the record available, the prior art cited for US 11,022,421 consists of (i) ten background permanent-magnet medical-tube/marker tracking patents (A1–A10), (ii) a ~50-document U.S. patent/application citation list dominated by the assignee's own magnet-based guidance family, (iii) eighteen foreign documents, and (iv) a metallurgy/magnetics NPL cluster plus the 2017-04-07 ISR. No cited reference anticipates claims 1, 11, or 17 (or any dependent claim) under 35 U.S.C. § 102, because each independent claim requires an energized core-plus-coil electromagnet on the instrument driven below 10,000 Hz — a combination absent from all of the cited art.

I'll ground this in the actual prior art of record and comparable AC tracking art, then build the §103 combinations.

Good — I found directly relevant AC/ultra-low-frequency tracking art. Let me characterize the key references and check the prosecution record.

Obviousness Analysis — US 11,022,421 B2 under 35 U.S.C. § 103

Scope note. This builds on the previously generated summary and litigation sections; I do not repeat their content. Two carry-forward flags that materially affect this analysis:

1. The claim numbering below is provisional. The earlier section reconstructed claims 1–5 from claim-language passages in the record and expressly warned the literal numbered set was not retrieved. I treat claim 1 = system (instrument + core + coil + sub-10 kHz drive + sensor + position calculation), claim 2 = trackable structure (distal-end core + coil), claim 3 = method (advance device, apply low-frequency signal to leads, detect in real time from outside the body, present visual tracking), claim 4 = system in "electromagnet" framing, claim 5 = method in "generate field from coil-on-core" framing. If the literal claims differ, the mappings hold but the numbering must be re-anchored.
2. The "Prior Art section" of this page is the front-page References Cited list plus the references incorporated by the specification. I retrieved that list (US 3,870,137 Fougere; 4,315,509 Smit; 4,686,332 Greanias; 4,710,708 Rorden; 4,937,743 Rassman; 5,098,426 Sklar; 5,119,104 Heller; 5,144,120 Krichever; 5,211,165 Dumoulin; 5,377,678 Dumoulin; 5,424,524 Ruppert; 5,425,367 Shapiro; 5,425,382 Golden; 5,622,169 Golden; 5,645,065 Shapiro; 5,767,669 Hansen; 5,775,322 Silverstein; 5,840,024 Taniguchi; 5,879,297 Haynor; 5,902,238 Golden; 6,078,854 Breed; RE36,791 Heller; 6,104,712 Robert; 6,129,668 Haynor; 6,173,715 Sinanan; 6,205,411 DiGioia; 6,216,028 Haynor; 6,263,230 Haynor; 6,292,680 Somogyi; 6,420,992 Richmond; 6,429,800 Richmond; 6,468,265 Evans; 6,926,227 Young; 6,933,849 Sawyer; 7,154,430 Buehler; 7,158,754 Anderson; RE40,927 Wild; 7,647,070 Shah; 7,798,404 Gelbman; 7,976,518 Shaughnessy; RE42,913 Wild; 8,197,494 Jaggi; RE43,681).

One explicit contradiction to flag. A search hit suggested the Espacenet "citing documents" list for EP2249273 (B1) includes US 2019/0025040 and US 11,022,421. I checked EP2249273B1 and it is titled "Systems and methods for managing information relating to medical fluids and containers therefor" — a medical-fluid/RFID-management disclosure, not electromagnetic tracking. The '421 front-page U.S. reference list I retrieved does not show EP2249273. I therefore treat that Espacenet hit as a probable family/citation-list artifact rather than substantive prior art, and I do not build any combination on it. Flagging rather than resolving it because the user message rule is to interpret identifiers literally and prefer search results — but here the search result and the patent's own reference list conflict, so I report the conflict instead of silently picking one.

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1. The level of ordinary skill and the governing standards

POSITA for a 2016 priority date in this art would be a person with a bachelor's degree in electrical/biomedical engineering (or equivalent) and 2–4 years of experience in electromagnetic position tracking or magnetic medical-device navigation, or a master's degree with less experience. That person would be familiar with: coil/core electromagnet design; ferromagnetic properties and skin depth; eddy-current and ferrous distortion; line-frequency interference (50/60 Hz and harmonics); magnetoresistive/Hall/inductive sensing; and dipole field models for position/orientation inversion.

Standards that drive the outcome:

• KSR Int'l v. Teleflex — combination of known elements with predictable results; "a finite number of identified, predictable solutions" → obvious to try.
• Result-effective variable (In re Applied Materials; Eibel) — where the specification itself identifies frequency as the variable controlling the result (skin depth, flux gain, line-noise avoidance), optimizing it is routine.
• Ranges (In re Woodruff; In re Geisler; In re Peterson) — a claimed range is obvious when the prior art teaches the range or renders it obvious to optimize, absent criticality.
• Analogous arts — the medical-device-navigation art (Golden/Haynor/Silverstein/Sinanan/Dumoulin) and the electromagnetic-tracking art (Blood/Acker/Hansen/Raab) are the same field of endeavor: locating an object in space (and, for Golden/Haynor, in a body) using magnetic fields.

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2. What the claims actually require, reduced to bare elements

Independent claims 2 and 5 are subsets of this (2 drops the control circuit and sensor; 5 drops the "medical instrument sized for insertion" framing and recites the same coil-on-core + low-frequency + sense + compute sequence). Claims 3 and 4 are the method/system mirrors. Every independent claim rises or falls on E4 plus the (largely conventional) framing.

That is the analytical crux: if E4 is obvious, the independent claims are obvious.

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3. The two-layer prior-art showing

Layer A — It was already known to compute a medical instrument's position in a body from magnetic fields sensed outside the body

The strongest references here are the patentee's own predecessors, all cited of record and expressly incorporated into the '421 specification:

• Golden US 5,425,382; 5,622,169; 5,902,238 — per the '421 specification's own characterization: medical tube with a magnetic element, external detection apparatus sensing field-strength gradient, moving the detector until the greatest gradient is indicated, distinguishing the device's field from the earth's field by differential sensing. → Teaches E1, E6, E7 and the display concept.
• Haynor US 5,879,297; 6,129,668; 6,216,028; 6,263,230 — per the specification: housings with three-or-more magnetic sensors having known spatial relationships, iterative calculation of estimated position/orientation of the magnet, predicted vs. actual field comparison, error function, earth's-field cancellation by subtraction, and visual display of the three-dimensional position. → Teaches E6, E7 in the exact "compute position of an indwelling device inside a patient" framing the '421 recites.
• Silverstein US 5,775,322 — magnet associated with a tracheal tube at a predefined distance from its distal end, confirming placement by detecting the source. → Supplies the distal-end-core placement of claim 2.
• Sinanan US 6,173,715 — magnetic anatomical marker in a non-degradable (biocompatible) envelope with a retention member, deliverable via an insertion tool. → Supplies the biocompatible-coating dependent and the implantable-instrument dependent.
• Somogyi US 6,292,680 — magnet-based non-invasive sensing of a physical parameter.

None of these uses a driven coil; they use static permanent magnets. That is the gap the '421 must not have covered — but the gap is filled by Layer B, and the motivation to fill it is itself in the art.

Layer B — It was already known to drive a coil-wound core with an alternating current, sense the resulting field, and compute position/orientation — including in catheters, and including at low frequencies

• Blood US 4,849,692 / 4,945,305 / 4,613,866 — as characterized in Acker US 5,558,091 (Biosense) at col. 1: "These systems typically employ a magnetic field transmitter incorporating several coils wound on orthogonal axes about an iron core, and a similar structure used as a receiver. The coils of the transmitter are actuated in sequence and/or at different frequencies, and the signals detected by the coils of the receiver are analyzed to determine the position and orientation…" → This is E2 + E3 + E4 (as a concept) + E5 + E6 + E7 in one reference. (US 5,558,091; uspto.report record)
• Acker US 5,558,091 — small solid-state/Hall-effect or magnetoresistive sensor accommodated in the tip of a catheter or endoscope; fields applied in a predetermined sequence, and in an alternative embodiment two or more fields applied simultaneously and varied at different frequencies with segregation by filtering; position and orientation computed from the sensed components; real-time superposition of the probe representation on a patient image. Sensor "adapted for disposition within the body of a human patient," probe "elongated, flexible element … sensor disposed adjacent said distal end." → Supplies E1 (in-body medical instrument), E6, E7, the magnetoresistive-sensor dependent, the multi-frequency/identification concept, and the real-time video display dependent. (US 5,558,091 A)
• Hansen US 5,767,669 (Ascension Technology) — cited on the '421 front page. Pulsed-magnetic-field position/orientation measurement with dynamic eddy-current rejection; expressly discusses that conductivity/permeability of nearby objects distort the field, that eddy-current distortion is induced by time-varying fields in conductive material, and that pulse length must be managed because of eddy-current decay; teaches multiple source pulse shapes (triangular, square, half-sinusoidal). → Supplies the motivation to select drive waveform/frequency to manage eddy currents and metallic distortion — the exact trade-off the '421 spec invokes. (US 5,767,669 A)
• Raab US 4,054,881 (Polhemus) — near-field magnetic position/orientation locating; expressly notes near-field intensity "is not a function of frequency," that low-frequency near fields "have the ability to penetrate many materials and objects … much more easily than do high frequencies," and that at low frequency the field "conform[s] to theoretical predictions based on a simple magnetic dipole," while acknowledging distortion from surrounding objects depending on "conductivity and permeability." → Supplies the physical motivation and predictability for operating at low frequency, and the dipole model used to invert the sensor readings. (US 4,054,881)
• US 7,761,100 B2 — "Ultra-low frequency electromagnetic tracking system." Teaches operating the EM tracker at a frequency "below that of a typical frequency of AC electricity supplied by an electrical power utility infrastructure, typically 50–60 Hz" (expressly 25.44 Hz, and "50 Hz, 40 Hz, 30 Hz, 25 Hz, 20 Hz, 10 Hz, or any other frequency below 60 Hz"), with the stated purpose of avoiding utility-power interference; and it characterizes Blood's US 4,849,692 and 4,945,305 as pulsed-DC systems. → This is the closest thing in the art to the '421's stated frequency-selection rationale and directly supplies the why of E4. (US 7,761,100 B2)
• Dumoulin US 5,211,165 and 5,377,678 (cited of record) — tracking the position/orientation of a device with applied fields, superposed on an image → corroborates E1/E6/E7 and the display.
• Background evidence of what a POSITA knew in fact about commercial AC trackers. A 2013 thesis survey in this field records that Polhemus Fastrak operates at ~120 Hz, Liberty at ~240 Hz, and Ascension's microBird receiver is <1.8 mm in diameter and can be inserted into a catheter, with AC (alternating-field) trackers being the dominant class alongside pulsed-DC. (dumas-01157544v1 PDF) This is contemporaneous evidence that coil-based AC electromagnetic tracking at a few hundred hertz, with the transducer inside a catheter, was standard commercial practice years before the '421's 2016 priority date.

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4. The combinations and the motivation to combine

Combination I (primary, per se obviousness of claims 1 and 4): Golden/Haynor + Blood + Acker

• Golden '382/'169/'238 + Haynor '297/'668/'028/'230 supply E1, E6, E7 and the display — but with a permanent magnet as the field source.
• Blood supplies the substitution: a coil wound around an iron core, driven at different frequencies, with the sensed signal analyzed for position and orientation.
• Acker supplies the "medical instrument" form factor and the sensor-in-the-catheter-tip architecture, plus the null/"off" state and multi-frequency separation.

Motivation (four independent, evidence-based reasons, any one of which suffices):

1. The static-field problem the '421 admits. The '421 spec states that ambiguous/steady fields — "the earth's magnetic field, electromagnetic interference from other medical and non-medical equipment … and from the medical instrument 102 itself" — make it "difficult to determine with acceptable accuracy the position … when a DC current is passed through the inductor coil." Golden/Haynor already had to solve the earth's-field problem by differencing, which the '421 acknowledges was the prior approach. Replacing the static magnet with an AC-driven electromagnet converts the earth's field from an equal-valued offset to a fixed-frequency component that can be filtered, and lets the source be switched off entirely so background can be measured and subtracted. Acker's null state does exactly this. A POSITA would recognize the substitution as solving the very interference problem Golden/Haynor already struggled with.
2. Multiplexing and multiple-instrument discrimination. Golden explicitly contemplates a plurality of magnets (Haynor '230 does so several times). Once the source is electrically driven, frequency or time-division multiplexing becomes available — which is exactly how Blood and Acker operate. The '421's own FSK/signature discussion (FIGS. 2Q–2R) is the same idea.
3. Switching/size. Golden's detection apparatus is a handheld scanner manually moved until the peak gradient is found; an energized coil permits automated, electronic sampling. Acker expressly notes that small solid-state sensors and energized fields permit iterative/convergent computation.
4. Same field of endeavor. Both families are "locate a thing using magnetic fields"; the medical-device side and the EM-tracker side routinely cross-cite (Acker cites Golden-era medical devices; the '421 cites both).

Result: E1–E7 all present. Claim 1 (and the parallel claim 4) obvious.

Combination II (the frequency limitation — the real battleground): Combination I + Hansen + US 7,761,100 + Raab

Even if a patentee argued that "below 10,000 Hz" was not disclosed with specificity by Blood (which merely says "different frequencies"), the range is obvious:

• Raab teaches that low-frequency near fields penetrate materials, are frequency-independent in near-field intensity, and conform to a simple magnetic dipole model — i.e., low frequency gives better predictability and better body penetration, not worse. That is a teaching away from nothing and a positive reason to select low frequency.
• Hansen teaches that time-varying fields induce eddy currents in conductive surroundings, that this distortion depends on frequency and material, and that managing pulse/frequency characteristics mitigates it. A POSITA reads this as: lower AC frequency → less eddy-current distortion.
• US 7,761,100 expressly teaches operating the tracker at a frequency chosen to avoid the 50/60 Hz utility-power band, with a working example at 25.44 Hz, and lists a broad sub-60-Hz set. The '421's stated rationale for ~330 Hz — "helps to avoid AC line related components" — is the same rationale, in the same direction, one decade up. The '421's own spec concedes that 300 Hz is disfavored because it is "a multiple of both 50 Hz and 60 Hz," which is an admission that line-harmonic avoidance was a known design criterion.
• Result-effectivity is conceded in the specification itself. The '421 states: lower frequency "penetrates the appropriate core material more deeply, thereby producing an appreciable magnetic flux gain of tens, hundreds, or thousands of times higher than similar devices formed with an air core," and that "an air core device will generally require a much higher excitation frequency." Those are textbook skin-depth statements; the specification presents no criticality or unexpected result — it presents the ordinary physics of choosing a frequency. That converts E4 into a result-effective variable optimized within a finite, predictable set.
• The range is bracketed. Commercial AC trackers already ran at ~120–240 Hz (Polhemus/Ascension), i.e., squarely inside both "below 10,000 Hz" and "below 500 Hz," with the transducer in a catheter. The claimed ~330 Hz sits in the same band and differs from the ~240 Hz Liberty only by routine tuning.

Result: Claims 1–5 obvious. Note that "below 10,000 Hz" is broad enough to read on essentially the entire pre-Aurora AC tracking industry; the only reason the claim is not anticipated outright by Polhemus/Ascension practice is the "medical instrument in a body" framing, which Golden/Haynor/Silverstein/Acker supply.

Combination III (claim 2 specifically): Silverstein or Sinanan + Combination I

Claim 2 requires (a) a core formed on the distal end of the instrument, the distal end being the insertion end; (b) a coil around it; (c) sub-10 kHz excitation → trackable field. Silverstein places a magnetic source at a predefined distance from the tube's distal end and detects it to confirm placement; Sinanan covers the biocompatible-envelope dependent; Acker places a sensor at the distal end of an elongated flexible element. Moving the field source from the proximal body of the tube to the distal tip — and winding a coil on a ferromagnetic core there — is the natural corollary of driving the source electrically and is supported by Blood's core-plus-coil teaching plus the catheter-tip art.

Combination IV (claim 3 specifically): Combination I + Acker's real-time display

Claim 3's extra limitations over claim 1 are: (i) "detect in real time, from outside the patient's body," and (ii) "present visual information that tracks motion." Acker supplies both verbatim in substance — its sensor signals are processed and a representation of the probe is displayed substantially in real time while the probe is in the patient, and Haynor's family computes position continuously. The "first and second conductive leads" limitation is merely the definition of coil terminations (Hansen, Blood, Acker all show driven source coils with leads).

Combination V (claim 5 method): same references, method format

Claim 5 is Combination I recited as steps, with a preference for under 500 Hz. Nothing new.

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5. Dependent-claim obviousness (as reconstructed)

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6. The patentee's best rebuttals, and why they likely fail on this record

1. "The claims recite position information within the body, and every tracking reference computes position outside a body." Rebutted by the Golden/Haynor family, which is expressly about indwelling medical devices located from outside the body, and by Acker, which computes probe position inside a patient's body.
2. "No single reference teaches the specific frequency." Correct, and that is why the Office would need the KSR/range framework rather than §102. But the frequency is (a) expressly characterized by the specification as a result-effective variable, (b) bracketed above and below by the prior art (sub-60 Hz in US 7,761,100; ~120–240 Hz in commercial trackers; the sole excluded class — NDI-Aurora-style ~tens-of-kHz systems — is above the 10 kHz ceiling), and (c) explained by skin-depth physics the specification itself recites. Under In re Woodruff/In re Peterson and KSR, that is a §103 case.
3. "Unexpected results — 65 cm tracking depth." The 65 cm figure is asserted in the '421 spec for its own sensor electronics, and the mechanism it cites (deeper skin penetration at lower frequency, flux gain "tens, hundreds, or thousands of times higher than similar devices formed with an air core") is the ordinary, expected consequence of putting a ferromagnetic core in a low-frequency AC field. There is no comparative data against the closest prior art (an iron-cored AC tracker) — only against an air core, which no prior-art reference of record used for the in-body device. That is not the "unexpected result" showing that defeats a prima facie case.
4. "Teaching away." I found none. Hansen and Raab both point toward lower frequencies; US 7,761,100 selects a frequency specifically to dodge line interference; Acker's multi-frequency embodiment points toward frequency selection as a design tool. Pulsed-DC (Blood/Anderson) is a different modulation, not a teaching away from low-frequency AC.
5. "Non-analogous art." The CMC/AC tracker art (Polhemus, Ascension) and the in-body magnet-localization art (Golden, Haynor) are both directed to locating an object by magnetic field; the field-of-endeavor and reasonable-pertinence tests are both satisfied, and the cross-citation pattern among these very patents confirms it.

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7. Bottom line

On the prior art I can ground, the independent claims (1–5 as reconstructed) are more likely than not invalid under § 103. The combination of Golden '382/'169/'238 + Haynor '297/'668/'028/'230 (in-body magnet localization with 3-D position/orientation computation and display) with Blood '692/'305/'866 + Acker '091 (coil-on-iron-core AC excitation, multi-frequency operation, sensor at a catheter tip, real-time display) discloses or suggests every element except the numerical frequency ceiling; and Hansen '669 + Raab '881 + US 7,761,100 supply the motivation, direction, and bracketing for that ceiling, with the specification itself conceding that the frequency is a result-effective variable explained by skin depth. Claim 3's "real time" and "visual information tracking motion" limitations are met by Acker. The two-material needle with an integrated core dependent is the only limitation where I could not assemble a clean mapping from the prior art I retrieved.

Confidence: Moderate-to-high on the framework and on the element-to-reference mappings for the references whose text I actually retrieved (Acker '091, Hansen '669, Raab '881, US 7,761,100, plus the Golden/Haynor/Silverstein/Sinanan/Somogyi characterizations quoted from the '421 specification itself). Lower confidence on specific teachings of the references I could only see as front-page citations (e.g., 5,119,104 Heller; 7,158,754 Anderson; 5,425,367 / 5,645,065 Shapiro; 6,933,849 Sawyer; 7,798,404 Gelbman) — I did not retrieve their text and deliberately did not attribute subject matter to them.

What I could not verify, and would need before finalizing:

• The literal numbered claim set and dependency structure (USPTO PatentCenter for app. 16/071,891) — the prior section and I both reconstructed these.
• The prosecution history / examiner's reasons for allowance — I could not retrieve the file wrapper, so I cannot say whether any of these references were applied and overcome, which would change the weight of the analysis materially.
• Whether the WO/EP family counterpart (WO 2017/127722 A1 / EP 3405109 A4) has a different claim scope or an opposition history — the EPO route often yields narrower claims, and EP3405109A4 appeared in the earlier search results without substantive content.

Sources: US 11,022,421 B2 PDF · Google Patents US11022421 · US 5,558,091 (Acker) · US 5,767,669 (Hansen) · US 4,054,881 (Raab) · US 7,761,100 B2 · '421 spec text · 2013 thesis, commercial AC tracker frequencies · Espacenet citing-documents page for EP2249273B1 (flagged anomaly)