US 6081237

I'll search for this patent number across the requested sources.

Let me specifically check for any 2026 CAFC docket activity and confirm the litigation posture.

US Patent 6,081,237 — "Antenna/Mirror Combination Apparatus"

Sourcing note: I do not have direct credentialed access to USPTO PatentCenter, PACER, or the CAFC docket system in this session. The following is drawn from the authoritative full patent text supplied to me (Google Patents, US6081237A, fetched 2026-09-28) plus corroborating public mirrors (EveryPatent, Justia, FreePatentsOnline, Google Patents). I flag uncertainty explicitly where it exists.

Bibliographic Data

Abstract

An antenna/mirror combination apparatus reduces the space occupied by a low-profile antenna so that the mirror case's internal space can be used for other purposes, and can be made inexpensively and compactly without impairing design freedom, by integrally combining an antenna array with a mirror. The apparatus includes a mirror (3) with an electrically conductive reflecting mirror surface (10) and a low-profile antenna (8) with an electrically conductive antenna element, in which the low-profile antenna (8) is disposed and combined integrally with the mirror (3) such that at least a part of the antenna element functions as a part of the reflecting mirror surface (10).

Overview of the Claims

Only claim 1 is independent. Claims 2–17 all depend (directly or indirectly) from claim 1. (Note per the "no auto-correction" rule: the patent's own claim text labels claim 13 as "according to claim 1," so despite its added subject matter it is formally dependent.)

• Claim 1 (independent — the core invention): An antenna/mirror combination apparatus comprising (a) a mirror with an electrically conductive reflecting mirror surface and (b) a low-profile antenna having an electrically conductive antenna element that includes a radiating portion. The low-profile antenna is combined integrally with the mirror, and at least a part of the antenna element functions as a part of the reflecting mirror surface. Plain language: the antenna and the mirror share structure — part of the antenna's conductive element is part of the mirror's reflective surface, so the assembly doesn't need separate real estate for a standalone antenna.

• Claim 2: The shared antenna element is specifically the radiating portion of the low-profile antenna.

• Claim 3: The radiating portion is printed onto the rear surface of the mirror's front glass plate, with the antenna superimposed on that rear surface.

• Claims 4–5: The antenna is a slot antenna array (slot array = radiating portion) with a waveguide; the front glass plate is superimposed on the waveguide's radiating (slot) surface.

• Claims 6–10: The antenna is a microstrip antenna array (radiating element + opposed ground conductor layer + interposed dielectric). Variations cover: radiating element on the dielectric's top surface (cl. 7); array only in a lateral region of the mirror with multiple radiating elements (cl. 8); dielectric and ground layer only behind the radiating portion (cl. 9); or spanning substantially the whole rear mirror surface to avoid an offset (cl. 10).

• Claims 11–12: Microstrip antenna variant in which the shared element is the ground conductor layer; the array is confined to a lateral region, with the ground layer serving as the reflective surface there.

• Claims 13–15 (phase-shifting theme): The radiating portion is split into multiple radiating sub-portions fed by feeder means, with multiple variable phase shifters setting different excitation phases per sub-portion (cl. 13). The mirror is rotatable; the sub-portions are juxtaposed along the rotational-axis direction; the phase shifters set phases to electrically cancel the physical displacement caused by mirror rotation (cl. 14). Each phase shifter comprises a feed line and a movable probe whose position shifts with the mirror's rotation angle (cl. 15).

• Claims 16–17: Structural implementations of the movable-probe phase shifter — either a microstrip feed line contacted by the probe under slidable pressure (cl. 16), or a waveguide feed line with a slot along which the probe is inserted and moves (cl. 17).

Practical/Commercial Context (from the specification)

The patent targets vehicle radar applications (door/fender mirrors) and frames the invention against two Japanese prior-art documents: JP-A-54-45040 (feed horn + light-transmissive reflector inside a fender mirror) and JP-U 3-52015 (thin microstrip antenna mounted behind the mirror glass). The stated problems with the prior art were added bulk, lost internal space for the mirror-drive mechanism, degraded design freedom, and the mirror blocking radiation in the viewing direction. The claims' phase-shifter family addresses a further problem — keeping the radar beam direction constant when the driver adjusts the mirror angle.

CAFC 2026 Docket Check — Negative Result

My searches for CAFC 2026 docket activity tied to 6081237/"6,081,237" returned no results (empty result sets for the docket/appeal queries). Consistent with this, the patent record shows it as "Expired – Lifetime" with an anticipated expiration of 2018-09-08 (20 years from the 1998-09-08 filing), so the patent has been expired for roughly eight years as of April 2026 — making live 2026 infringement litigation or a CAFC appeal on this patent unlikely.

Uncertainty caveat: This is a negative finding from surface web search, not a verified docket query against PACER/CAFC's own system, which I cannot access here. A definitive "no 2026 CAFC case exists" statement would require a direct CM/ECF or PACER search under the patent number and assignee names (Mitsubishi Denki Kabushiki Kaisha / Mitsubishi Electric Corp.). Separately, note that one search result (an RPX litigation document) mentioned patents numbered '375, '486, and '007 asserted by "Signal IP" against Mitsubishi vehicles — none of those are 6,081,237, so that matter is not relevant here and should not be conflated with this patent.

I'll search for litigation involving US patent 6081237.

Let me dig deeper with more targeted searches.

Let me try litigation-specific databases.

Litigation Search: US Patent 6,081,237

Patent identification (confirmed)

• Patent number: US 6,081,237 B1 (interpreted literally as "6081237")
• Title: Antenna/mirror combination apparatus
• Assignee: Mitsubishi Electric Corp (original and current)
• Inventors: Shinichi Sato; Shinichi Honma
• Application: US 09/148,946, filed 1998-09-08
• Grant date: 2000-06-27
• Status: Expired – Lifetime; anticipated expiration 2018-09-08

Litigation findings

No litigation involving US Patent 6,081,237 was found.

I searched for the specific number 6081237 across patent-litigation-oriented sources (including Unified Patents' litigation/PTAB portal materials surfaced via search, Docket Alarm/PTAB records, and general district-court references). The searches did not return any district-court case, ITC investigation, or CAFC appeal in which US 6,081,237 is asserted or at issue.

What the searches did return — none of which is litigation against this patent:

1. A USPTO PTAB document (ptacts.uspto.gov) that merely lists a long sequence of patent numbers — including "6081237" — as part of a string of patent identifiers. This is a list of numbers (apparently a related-patents/prior-art-style table), not a case involving this patent.
2. A Google Patents / searchlight.law page reproducing the patent's own text and claims.
3. Numerous Unified Patents filings and PTAB documents that matched on generic terms ("6081237", "litigation", "Mitsubishi Electric"). Every substantive hit concerned other patents (e.g., US 7,454,002; US 9,253,239; US 10,013,158; US 8,605,794; US 11,481,433) and unrelated parties. None references US 6,081,237.

Conclusion

Based on the sources searched and retrieved, there is no known litigation involving US Patent 6,081,237. The patent is expired (anticipated expiration 2018-09-08) and its prosecution/assignment history shows only the original grant to Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corp).

Caveats on completeness

• This conclusion is limited to results retrieved from the searches run; I could not directly query PACER, the CAFC docket, or the full Unified Patents case list because live paginated access to those databases was not available through the search results returned.
• Under the operating rules, I will not fabricate case details. I have no plaintiff, defendant, jurisdiction, case number, filing date, or outcome to report for this patent, because none was found.
• If you need a definitive negative, the authoritative checks would be: (a) PACER/RECAP full-text search on "6,081,237"; (b) the CAFC docket; and (c) the USPTO patent's "Litigation" / Patent Examination Data tabs on the Google Patents page, which list any asserted cases. A direct query on those databases (rather than via web search) is recommended to confirm the negative with certainty.

Proceedings overview

Total PTAB proceedings on file: 0. The structured USPTO Open Data Portal block returns no AIA trial proceedings (no IPR, PGR, or CBM) for US 6081237, and independent web searching surfaced no institution decisions, FWDs, or CAFC appeals naming this patent. There is therefore nothing in the "claims invalidated / claims sustained / settled / institution denied" buckets to break out — the patent has never been challenged at the PTAB. The bottom-line defensive posture is not "hardened by surviving IPRs"; it is "the patent is expired (anticipated expiration 2018-09-08, status: Expired - Lifetime), so the practical defense is temporal — no PTAB petition was ever needed, and any damages theory is limited to the pre-expiration damages window."

For each proceeding: none exist. No proceeding number is listed, and I will not invent one.

(No proceedings to enumerate)

• Type: N/A
• Filed: N/A
• Status: N/A — the ODP structured data contains an empty proceedings list; no IPR/PGR/CBM was ever instituted against US 6081237.
• Judge panel: N/A
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: N/A
• Settlement / termination: N/A
• Appeal: No PTAB appeal to the Federal Circuit exists because there was no PTAB trial to appeal. No IPR/PGR/CBM-derived CAFC docket could be located.
• Defensive value: The absence of PTAB activity is explained by the patent's age and term, not by invulnerability. US 6081237 issued 2000-06-27 from an application filed 1998-09-08 (priority 1998-03-05) and expired 2018-09-08. A defendant today cannot be liable for ongoing infringement of an expired claim; exposure, if any, is confined to the six-year pre-suit lookback under 35 U.S.C. § 286 and to conduct occurring before expiration.

Strategic summary

Claim status. Claims 1–17 were granted and, per the ODP data, none were ever challenged or canceled — so all 17 claims are technically UNTESTED at the PTAB, not "canceled" and not "sustained." That distinction matters: there is no FWD to cite and no claim-level holding to quote, because no trial was ever instituted. The patent's operative limitation today is term, not adjudicated validity: it lapsed on 2018-09-08 (the "Expired - Lifetime" legal status in the structured data).

Estoppel landscape. Because no petitioner ever filed, § 315(e)(2) estoppel is entirely absent — no party is barred from raising any § 102/§ 103/§ 112 ground in district court or at the ITC. Any invalidity defense is unencumbered by prior PTAB findings. The flip side: for a defendant, an IPR is now largely moot as a strategic tool. The PTAB will still institute on an expired patent in principle, but the patent owner cannot amend claims in an expired patent, and — critically — an expired patent cannot support prospective injunctive relief, so the usual reason to seek an IPR (knocking out live claims before/alongside litigation) is gone. The real defense is the calendar and § 286.

Pattern signals. There is no petitioner pattern to report — no repeat filer, no defensive aggregator (no Unified Patents or similar) in the chain, and no PTAB-to-CAFC appeal history. The only post-grant activity appearing in the record is administrative: a certificate of correction and maintenance-fee payments (FPAY events) reflected in the Google Patents legal-events table. Note also that assignment records mentioning "SMR PATENTS S.A.R.L." appear in the family/legal-events listings for related mirror-antenna patents (e.g., US 6380902, assignment reel/frame 030839/0133, inventors Duroux), not as an assignment of US 6081237 — do not attribute that ownership transfer to this patent without confirming the reel/frame against the 6081237 file.

Recommended next steps

• No PTAB activity exists — say so plainly. Do not build any argument, chart, or client memo that assumes an IPR or FWD on US 6081237. There is no institution decision, no final written decision, and no Federal Circuit appeal to link. Any citation purporting to be an "IPR on 6081237" should be treated as a fabrication until an E2E docket number is produced.
• Verify the expiration and the maintenance-fee record at the USPTO Patent Center / Google Patents legal-events table (https://patents.google.com/patent/US6081237/en) before responding to any demand. If the patent lapsed 2018-09-08 with all fees paid to term, pre-suit damages are capped by 35 U.S.C. § 286's six-year lookback and cannot extend to post-expiration conduct.
• If a demand letter is received, demand the asserted claim numbers and the accused-product date range. For any accused conduct occurring on or after 2018-09-08, the expired claim cannot be infringed. For earlier conduct, the invalidity defense is fully open (no § 315(e)(2) estoppel) — run the § 102/§ 103 analysis against the 1998 priority date using the very prior art discussed in the specification (JP-A-54-45040 and Japanese Utility Model Publication 52015/1991).
• Monitor for late-filed proceedings. Your instructions note ODP ingest can lag; a recently-filed petition would be the one scenario that changes this picture. If one appears, it would be captioned before the PTAB and reachable via PTAB E2E / the PTAB Decisions portal. As of 2026-09-28, none was found on the web, and the ODP structured list is empty.

Caveat on sourcing: this analysis rests on (1) the structured "PTAB proceedings on file" block (empty for this patent) and (2) the patent's own Google Patents record (https://patents.google.com/patent/US6081237/en), which shows status "Expired - Lifetime" and an anticipated expiration of 2018-09-08. I could not locate any PTAB E2E or CourtListener document for an AIA trial on this patent, and I have not fabricated a proceeding number to fill the gap.

I'll research the assignment record for US 6081237. Let me run several targeted searches.

Let me look for the assignment center record and any post-issuance transfers.

Let me try to pin down the assignment reel/frame and confirm whether any post-issuance transfers exist.

Inventors

Both inventors are listed with Tokyo, JP addresses on the face of the patent, and both are named as assignors in the original assignment to Mitsubishi Denki Kabushiki Kaisha (per the "Assigned to" legal event of 1998-09-08 on the Google Patents record). Their affiliation is corroborated by a contemporaneous Mitsubishi Electric publication — Offset Paraboloidal Reflector Antenna for Vehicular Collision Avoidance Radar (SAE 1999-01-1237), authored by Shinichi Honma, Toshiyuki Takahara, Masahira Akasu and Shinichi Sato, Mitsubishi Electric Corp. — the same technical field (vehicular radar antennas) as the patent.

Unusual patterns: None detected. I found no evidence that either inventor departed Mitsubishi Electric within 12 months of filing, and no re-assignment of inventor rights to any third party. There is no "all inventors left the assignee" signature that would precede a fire-sale.

Original assignee

• Entity on the issued patent: Mitsubishi Denki Kabushiki Kaisha (English: Mitsubishi Electric Corporation), Tokyo, JP. Now styled "Mitsubishi Electric Corporation" (7-3, Marunouchi 2-chome, Chiyoda-ku, Tokyo 100-8310).
• Primary line of business: Large diversified electrical/electronic equipment manufacturer (energy & electric systems, industrial automation, information & communication, electronic devices, and automotive equipment). The patent's car-radar antenna subject matter sits squarely in Mitsubishi Electric's automotive-equipment line.
• Current status: Operating. It is a publicly listed Japanese corporation (Tokyo Stock Exchange) and remains an active operating company. There is no bankruptcy, dissolution, or acquisition event affecting the assignee.
• Product embodiment: I could not confirm with high confidence that a specific commercial product reading on the claims was shipped under this patent number. The claims (a low-profile radar antenna whose conductive element doubles as part of the mirror's reflecting surface) align with Mitsubishi Electric's millimeter-wave vehicular radar work of the late 1990s, but a product-level mapping was not verified. Stated as a gap rather than a finding.

Assignment timeline

Record located: The USPTO Assignment Center / Google Patents legal-events record for US 6,081,237 shows only the original assignment executed at filing. There is no recorded post-issuance assignment — no transfer to an LLC, no security agreement, no merger, no change of name. Ownership has never left the original assignee.

• 1998-09-08 (executed on/around filing) / recorded 1998-09-08 — Reel/Frame not retrievable via the search tools available for this analysis (see caveat below)
  • Conveyance: Assignment of assignors' interest ("ASSIGNMENT OF ASSIGNORS INTEREST — SEE DOCUMENT FOR DETAILS")
  • Assignor: Shinichi Honma; Shinichi Sato
  • Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corp.)
  • Correspondent: Not retrieved from the Assignment Center record. The prosecution attorney/agent of record on the face of the patent is Sughrue, Mion, Zinn, Macpeak & Seas, PLLC (per the patent's "Attorney, Agent, or Firm" field). Note this is the prosecution correspondent, which is a different role from the attorney who files the assignment recording; I did not confirm that Sughrue, Mion filed the reel/frame recording, so I do not treat it as the assignment correspondent. No repeat-correspondent pattern is present in any event, because there is only one recorded assignment.
  • Context: Internal — employee invention assignment to employer. No consideration-based sale, no securitization, no fire-sale.

Caveat on precision (stated per the operating rules): I could not retrieve the specific 6-digit reel / 4-digit frame number, the exact execution date, or the assignment-recordation correspondent name/address through the web searches run. The Assignment Center is a POST-form database that my search tools surfaced only indirectly; a direct query at the source is required to read the reel/frame and correspondent fields. I will not invent those values. The existence and nature of the single assignment (inventors → Mitsubishi Denki K.K., recorded at filing) is corroborated by the patent's legal-events entry.

Timeline diagram

timeline
    title Ownership of US 6081237
    1998 : Filed by Mitsubishi Denki
         : Inventors assign rights to employer
    2000 : Patent granted
    2018 : Patent expired

NPE / troll-pattern signals

Verdict

Insufficient data (only the original assignment).

The sole recorded conveyance is the inventors' assignment of their rights to Mitsubishi Denki Kabushiki Kaisha, recorded 1998-09-08 at filing, with no post-issuance assignment of any kind — the record ends there until the patent's anticipated expiration on 2018-09-08. Under the prescribed rubric, a chain consisting only of the original assignment maps to "Insufficient data," and that is the honest call here. Substantively, every NPE signal is affirmatively absent: ownership never left a large operating company, there is no shell LLC, no known asserter, no cascading transfer, and no bankruptcy or privateering event. The one unresolved gap is the literal reel/frame number and assignment correspondent, which my tools could not read from the Assignment Center; a direct query is needed to complete the citation.

Verification link: USPTO Patent Assignment Search — https://assignmentcenter.uspto.gov/ (search by patent number 6081237, application 09/148,946) and the patent's legal-events/assignments tab at https://patents.google.com/patent/[US6081237A](/patent/US6081237A)/en.

Cross-reference note (no contradiction)

This reconstruction is consistent with the earlier litigation section (no litigation found) and with the "Expired – Lifetime" status. One wording wrinkle worth flagging: Google Patents renders the assignee as "MITSUBISHI DENKI KABUSHIKI KAISHA" in the assignment event and "Mitsubishi Electric Corp" in the "Current Assignee" field. These are the same entity (Denki = Electric; K.K. = Corp.) — a translation/labeling difference, not a change of name assignment, and no "Change of Name" conveyance is recorded. I have not treated it as a transfer.

I'll research the prior art cited for US 6,081,237, including its face-of-patent references and the prior-art documents discussed in its specification.

Let me gather detailed bibliographic and technical information on each cited reference.

Prior Art Analysis — US Patent 6,081,237

Source verification (USPTO database)

I retrieved the USPTO/Google Patents grant record for the literal number 6081237 (US 6,081,237 B1, "Antenna/mirror combination apparatus"). Its citation-of-record set is small and is reproduced below. I did not substitute any similar number.

Patent bibliographic data (confirmed from the record):

• Patent No.: US 6,081,237 B1 (recorded "$6081237")
• Application: US 09/148,946; filed 1998-09-08
• Priority date: 1998-03-05 (JP 10-053710)
• Granted: 2000-06-27
• Inventors: Shinichi Sato; Shinichi Honma
• Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corp)
• Status: Expired – Lifetime (anticipated expiration 2018-09-08)
• Critical date for prior art: 1998-03-05 (foreign priority) / 1998-09-08 (actual U.S. filing)

All references cited on the face of US 6,081,237 (there are exactly four):

Source: https://patents.google.com/patent/US6081237 (Citations table).

Claim 1 — the only independent claim (the § 102 touchstone)

All other claims (2–17) depend from claim 1. Claim 1 requires, in combination:
(a) a mirror having an electrically conductive reflecting mirror surface;
(b) a low-profile antenna having an electrically conductive antenna element that includes a radiating portion;
(c) the low-profile antenna combined integrally with the mirror; and
(d) at least a part of the antenna element functions as a part of the reflecting mirror surface.

Element (d) is the point of novelty. Any § 102 analysis therefore turns on whether a single reference discloses an antenna element that doubles as the visible-light reflecting mirror surface.

Reference-by-reference analysis

1. JPS5445040A — Nissan Motor Co Ltd, "Rear warning radar device"

• Full citation: Japanese Unexamined Patent Application Publication No. 54-45040 (JP-A-54-45040 / JPS5445040A), published 1979-04-10; priority 1977-09-16.
• Family: GB 2,004,418 B; DE 2,839,848 C3; US 4,210,357 A ("Vehicle having side-rear surveillance radar with antenna reflector assembled with rearview mirror").
• Brief description: A radar antenna is built into a vehicle fender mirror. A microwave unit (Gunn diode/modulator) sits in the mirror support; a light-transmissive (visible-light transparent) parabolic reflector is mounted in the mirror case, and a feeder horn radiates toward the reflector focus "so that the reflector may not come into the view of the mirror." The reflector reflects microwaves but transmits visible light; the separate mirror surface reflects the visible light to the driver. This is precisely the FIG. 21 prior art discussed in the specification (col. 1).
• § 102 assessment: Does not anticipate any claim. The reference combines an antenna with a mirror (relevant to claim 1's "integrally combined" element), but its antenna element (the parabolic reflector, 26) is expressly light-transmissive and is not part of the reflecting mirror surface — the opposite of claim 1 element (d). If anything, JPS5445040 teaches away from using the antenna element as the mirror surface. Relevant only as § 103 background analogous art.

2. JPH0352015A — Fujitsu General Ltd

• Full citation: Japanese publication JPH0352015A, published 1991-03-06. This corresponds to the document the specification calls "Japanese Utility Model Publication 52015/1991" (see FIG. 22 discussion).
• ⚠ Discrepancy flagged: Google Patents indexes JPH0352015A with the title "Detecting and recovery circuit for power supply break" — a power-supply circuit title that does not match the specification's citation of a thin low-profile antenna housed in a mirror case. The specification (and FIG. 22) treats 52015/1991 as the second known antenna/mirror combination. The number-to-subject mismatch appears to be a database indexing artifact (the Heisei-3 utility-model publication series vs. a same-numbered unexamined patent application publication). Per the operating rules I am not silently correcting it; I flag that the title indexed by the database conflicts with the description in the patent. The substantive reference — the thin antenna in a mirror case of FIG. 22 — is described in the specification itself.
• Brief description (as characterized by the patent, FIG. 22): a low-profile (microstrip) antenna is disposed between the mirror case and the mirror. The antenna cannot radiate/receive in the direction the mirror faces and radiates only in the opposite direction; it also consumes internal mirror-case volume and constrains design freedom.
• § 102 assessment: Does not anticipate any claim. It discloses a low-profile antenna placed in the mirror, but no antenna element serves as the reflecting mirror surface; the mirror is an obstacle to radiation. This is the very deficiency the '237 patent was designed to overcome. § 103 background only.

3. US 5,649,316 A — Elden, Inc., "In-vehicle antenna"

• Full citation: U.S. Patent 5,649,316, filed 1995-03-17, granted 1997-07-15, Elden, Inc.
• Brief description: A cellular-telephone antenna/system for vehicles. It discusses mounting tradeoffs for external (roof, trunk, glass-mounted) and in-vehicle antennas (interior rear-window antennas, etc.) and a cellular telephone system.
• § 102 assessment: Does not anticipate any claim. It concerns antenna mounting inside a vehicle generally; it discloses no mirror, no conductive mirror reflecting surface functioning as an antenna element, and no integral antenna/mirror combination as recited in claim 1. Relevant only as remote background analogous art.

4. US 5,798,688 A — Donnelly Corporation, "Interior vehicle mirror assembly having communication module"

• Full citation: U.S. Patent 5,798,688, filed 1997-02-07, granted 1998-08-25, Donnelly Corporation.
• Brief description: A vehicle interior rearview mirror assembly houses an electromagnetic communication module (e.g., keyless-entry receiver, GPS receiver, garage-door opener). The module is a PCB mounted in a cavity of the mirror's manual actuator. The antenna is either a discrete coil-wound antenna on the board or metallic traces integral with the circuit board. The mirror reflective element (20) and the antenna are separate structures; the antenna is behind/inside the mirror casing and does not form the reflective surface.
• § 102 assessment: Does not anticipate any claim. It shows placing an antenna within a vehicle mirror assembly, but the antenna element is not part of the reflecting mirror surface, and no radiating portion is integrated into the mirror surface. § 103 background art.

Conclusion on § 102

None of the four references cited on the face of US 6,081,237 anticipates any of claims 1–17 under 35 U.S.C. § 102. Every reference discloses an antenna in or near a mirror, but none discloses the claim-1 requirement (d) that "at least a part of said antenna element functions as a part of said reflecting mirror surface." That single limitation is what distinguishes the '237 patent from all cited art:

• JPS5445040 / US 4,210,357 — antenna element is light-transmissive, deliberately not the mirror surface.
• JPH0352015 (per the spec / FIG. 22) — antenna sits behind the mirror; the mirror obstructs radiation.
• US 5,649,316 — no mirror at all.
• US 5,798,688 — antenna inside the mirror housing, physically separate from the reflective element.

From an examination standpoint, the cited set functions as § 103 analogous art establishing the general idea of combining an antenna with a vehicle mirror; the patent's contribution over that art is the dual-use antenna-element-as-mirror-surface architecture (slot array in a waveguide top wall, microstrip radiating element/ground layer formed with the reflecting layer, etc.) recited across claims 2–17 (slot-array embodiment, claims 4–5; microstrip embodiments, claims 6–12; variable-phase-shifter rotation-compensation embodiments, claims 13–17).

Caveats

• The face-of-patent citation set is limited to the four references above (source: https://patents.google.com/patent/US6081237). The two Japanese documents are the only prior art discussed substantively in the specification (JP-A-54-45040 and Japanese Utility Model Publication 52015/1991); JPS5445040A is the counterpart of the formal citation, and JPH0352015A is the database entry matching 52015/1991 — with the title discrepancy flagged above.
• The lists returned by ptacts.uspto.gov (petition documents) that contain the string "6081237" are prior-art/related-number tables, not citations to this patent, and are not litigation or prosecution citations of record.
• Because the patent is expired (2018-09-08) and no litigation was found in the prior analysis, this prior-art set is derived from the granted record; I could not retrieve a separate USPTO "References Cited" examiner/IDS artifact beyond what Google Patents reproduces. A direct USPTO PatentCenter / Global Dossier pull of the file wrapper would be the authoritative confirmation, and I did not have paginated PatentCenter access here.

I'll research the prior art cited on the patent's page before building the § 103 analysis.

Let me get the actual cited prior-art table from the patent's Google Patents page.

Let me pull the full citation list from the patent page and related databases.

Obviousness Analysis — US 6,081,237 under 35 U.S.C. § 103

0. Evidentiary basis and a necessary caveat

This analysis builds on the earlier sections (identification and the negative litigation finding) without repeating them. Before the merits, one limitation must be stated plainly, per the operating rules:

• The authoritative full text of US 6,081,237 supplied in this workspace identifies only two prior-art references, both in the "Description of Related Art" section: Japanese Unexamined Patent Application Publication No. 45040/1979 (JP-A-54-45040) and Japanese Utility Model Publication 52015/1991 (discussed as the mirror-case microstrip antenna of FIG. 22). These are the applicant's own acknowledged prior art.
• The Google Patents page also carries a "Prior art keywords" field (mirror; antenna; radiating; combination apparatus; low) and a patent-citation table. Search snippets confirm that table is labeled "Patent Citations (34)" (e.g., the citation table surfaced at https://patents.google.com/patent/US7498970). I was unable to retrieve the full 34-entry list for US 6,081,237 before the research step limit was reached. I therefore will not invent citation numbers or dates. Where the analysis must reach beyond the two verified references, I identify the category of art by its Google Patents classification slot rather than asserting a specific unverified document.
• Two identifiers that appeared in citation results — JPH11266120A (pub. 1999-09-28) and JPH11220325A (pub. 1999-08-10), both Mitsumi Electric — and US6259412B1 ("Vehicle exterior mirror with antenna," 2001) — post-date the 1998-03-05 priority date and therefore are not prior art to this patent. They appear in "Cited By" / citation tables of other patents, not as § 102/§ 103 art here.
• US6081237A's own Japanese family member (JP 5371098 → JPH11251830A, filed 1998-03-05, published 1999-09-17, Mitsubishi, Sato/Honma) is a counterpart, not prior art. Correctly stated, per the literal-identifier rule: the JP application is 5371098 and its publication is JPH11251830A; either may appear in databases, but neither is prior art against the US patent.

The result is that the analysis below is strongest for claims 1–2 (where the two verified references do real work) and progressively more dependent on general knowledge / unverified art for the dependent claims. I flag the dependent-claim analysis as provisional.

1. Governing law and the level of ordinary skill

Legal framework. Obviousness is judged under the Graham v. John Deere factors — (1) scope and content of the prior art, (2) differences between the prior art and the claims, (3) level of ordinary skill, and (4) secondary considerations — applied through the KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) lens: a combination is obvious if a PHOSITA would have had a reason to combine the references with a reasonable expectation of success, including where the combination is "the mere application of a known technique to a known device ready for improvement," or a predictable use of prior-art elements according to their established functions.

PHOSITA (as of 1998-03-05). A person of ordinary skill in this art would hold at least a B.S. in electrical engineering (M.S. typical) and roughly 2–5 years of experience in RF/antenna design, with familiarity in: (i) planar low-profile antennas — microstrip/patch arrays and slotted-waveguide arrays; (ii) automotive radar front-ends and antenna packaging; (iii) microwave feed networks and phase shifters; and (iv) vehicle mirror packaging (mirror glass, reflective coatings, power-fold/positioning mechanisms). The patent's own "Landscapes" fields — Remote Sensing, Waveguide Aerials, Variable-Direction Aerials and Aerial Arrays, Details of Aerials, Fittings on Vehicle Exteriors — define exactly this skill set.

2. Scope and content of the prior art on the record

A. JP-A-54-45040 (the FIG. 21 apparatus). As summarized in the patent text, this reference teaches an automotive radar antenna integrated with a vehicle fender mirror. Its material teachings are:

1. Antenna/mirror co-location — the radar antenna is "implemented by making use of a fender mirror of a motor vehicle (i.e., in integral combination with the mirror)."
2. Radiating through the mirror's field of view — a feed horn radiates at a light-transmissive (visible-light-transparent) electrically conductive reflector, producing "a radio wave beam of high directivity in the visual field direction of the mirror."
3. Preservation of mirror function — the reflector "reflect[s] only the radio waves … without impairing the inherent function of the mirror."
4. It places a conductive element (the reflector 5) in the optical path of the mirror, establishing that a conductive structure can be located at the mirror without destroying the mirror's visual function.

B. Japanese Utility Model Publication 52015/1991 (the FIG. 22 apparatus). This reference teaches:

1. A low-profile (thin-plate) antenna housed within a mirror case of a fender/door mirror.
2. Microstrip antenna on a substrate as the specific low-profile implementation — i.e., the dielectric/radiating-element/ground-plane architecture.
3. The blocking problem — the low-profile antenna "is incapable of transmitting/receiving radio waves in the direction in which the mirror 3 is oriented … only in the direction opposite to that covered by the mirror 3." The reference thus expressly recognizes the mirror as an RF obstruction.
4. Packaging constraint — accommodating the antenna in the case limits the space available for the mirror drive mechanism and degrades design freedom.

C. Classification-defined analogous art (structure, not document-specific). The patent's own classification set identifies the fields a PHOSITA would consult:

• H01Q9/0407 — "Substantially flat resonant element parallel to ground plane, e.g. patch antenna" — the entire corpus of patch-antenna art.
• H01Q21/065 — "Patch antenna array"; H01Q21/064 — "Two dimensional planar arrays using horn or slot aerials" — slotted-waveguide and planar-array art.
• H01Q1/3266 — "…characterised by the location of the antenna on the vehicle using the mirror of the vehicle" — confirming a dedicated body of art on mirrors-as-antenna-locations.

These are fields, not citations; a formal § 103 rejection would populate them with specific documents. I treat them as the art a PHOSITA is presumed to know.

3. The differences between the prior art and the claims

The whole point of novelty sits in claim 1's final limitation:

"at least a part of said antenna element functions as a part of said reflecting mirror surface."

Prior art A colocates a conductive element with the mirror but uses it only as an RF reflector (a separate element in front of the mirror, not the mirror surface itself). Prior art B colocates a low-profile antenna with the mirror but neither radiates through the mirror nor dual-uses a conductive element. The claimed insight is functional dual-use of one conductive surface: it reflects visible light (mirror) and radiates/receives RF (antenna). The dependent claims then elaborate which conductive element performs the dual role — the slot-array face (claims 2, 4–5), the radiating element (claims 2–3, 6–10), or the ground conductor layer (claims 11–12) — and add beam-stabilization hardware (claims 13–17).

4. Claim-by-claim analysis

Claim 1 (independent) — combination A + B, plus the known dual-use principle

Proposed combination: JP-A-54-45040 + Japanese Utility Model Publication 52015/1991. Both are in the same field of endeavor (automotive antenna/mirror combinations), both are admittedly known to the applicant, and both diagnose the same problems (mirror-case bulk; degraded design freedom; radiation blocked by the mirror).

• A supplies the motivation and the pattern of radiating through the mirror's viewing direction via a conductive element placed at the mirror, while B supplies the low-profile (microstrip) antenna implemented directly behind the mirror surface.
• Combining them: a PHOSITA seeking to (i) shrink the mirror case, (ii) free space for the mirror drive, and (iii) radiate into the mirror's field of view rather than away from it, would place B's low-profile antenna so it radiates through the mirror region rather than behind an opaque mirror — the very direction B identifies as blocked.
• The remaining limitation (the antenna element is part of the reflecting surface) would have been obvious because (a) the mirror reflective layer is, by definition, an electrically conductive coating, and (b) using a shared conductive surface as both a radiator/ground and a reflective plate is a known expedient in planar-antenna practice. Making the reflective layer serve as the antenna's conductive element is the application of a known technique (integrating conducting layers) to a known device (a mirror-housed low-profile antenna) to yield the predictable result of reduced parts, reduced depth and unobstructed radiation. This is precisely the KSR "known technique to a known device ready for improvement" rationale.

Assessment: Claim 1 is reasonably argued obvious over A + B in view of the dual-use principle — but note the combination's soft spot in § 6 below.

Claim 2 (radiating portion constitutes the dual-purpose element)

Slot-array art (classification H01Q21/064) teaches a radiating face that is itself a conductive plate perforated by narrow slots. Such a face inherently reflects (it is a solid conductive wall) while radiating (through its slots). A PHOSITA applying claim 1's dual-use idea to a planar antenna would naturally land on exactly this: the slot face is simultaneously the mirror reflector and the radiating portion. Strong obviousness case, particularly combined with claim 1's motivation to minimize visual obstruction.

Claims 3 (printing on rear of front glass plate)

Printing/etching conductive patterns on automotive glazing (window antennas and printed antenna elements on glass) is a mature, well-known technique — indeed the patent itself repeats that "the reflecting mirror surface layer 10 and the slot array 13 can be formed by resorting to an etching process suited for a mass production." A PHOSITA would adopt printing/etching on the glass rear surface for cost and manufacturing simplicity. Likely obvious as a routine manufacturing choice; but support here rests on unverified glass-antenna art (I could not retrieve the citation list).

Claims 4–5 (slot antenna array with waveguide; slot array in radiating surface; glass plate superposed)

Slotted-waveguide arrays for automotive radar were a well-established planar-array architecture (classification H01Q21/064). Superposing the mirror glass on the waveguide's radiating face is the straightforward mechanical realization of claim 1's dual-use idea. Likely obvious.

Claims 6–7 (microstrip antenna array: radiating element / ground plane / dielectric; element on top of dielectric)

This is the textbook patch antenna (classification H01Q9/0407; H01Q21/065 for the array). Prior art B already discloses a microstrip antenna at the mirror. Claim 6 is essentially B's antenna + claim 1's dual-use limitation; claim 7 (element on the dielectric top surface) is the conventional patch construction. Likely obvious.

Claims 8–10 (lateral-region placement; dielectric/ground only behind the radiating portion, or over the whole rear surface)

These are design choices / obvious optimization: confining the antenna to a peripheral region to preserve the viewing area; trimming the dielectric/ground to the minimum needed (to save cost/bulk) versus extending it over the whole rear surface (to avoid an offset). The patent itself frames claim 10 as the fix for an offset appearing in the rear surface — a packaging trade-off, not an inventive contribution. Likely obvious under KSR's "predictable variations."

Claims 11–12 (ground conductor layer as the reflective mirror surface; antenna formed only in a lateral region)

Claim 11 relocates the dual-use role to the ground plane. Given claims 1 and 2 and the well-known notion that a patch antenna's ground plane is a large conductive plate, using that plate as the mirror's reflective layer is the same dual-use insight applied to a different element — likely obvious once claim 1 falls. Claim 12 (lateral region, radiating elements in front of the mirror through the dielectric, mirror surface realized by the ground layer) is a specific geometric arrangement that follows from the lateral-region choice of claim 8; likely obvious.

Claims 13–14 (divided radiating sub-portions; feeder + variable phase shifters; rotatable mirror; phase compensation)

If the antenna is on the mirror, rotating the mirror (to change field of view) rotates the radiating aperture and steers the beam — a problem the patent itself identifies. Electronic beam steering / phase compensation of a mechanically displaced aperture via variable phase shifters is a cornerstone of phased-array art (classification H01Q21/00, Variable-Direction Aerials). Dividing the aperture into sub-portions fed through independent phase shifters to cancel a mechanical displacement is the canonical phased-array solution with a reasonable expectation of success. Likely obvious over the antenna/mirror combination plus phased-array art.

Claims 15–17 (probe-type variable phase shifter; sliding contact on microstrip line; probe in a waveguide slot)

A movable probe along a feed line is the classic sliding-probe/slotted-line phase shifter and standing-wave detector — an old and well-understood microwave component. Claim 15 (feed line + movable probe), claim 16 (sliding pressure contact on a microstrip line), and claim 17 (probe inserted in a waveguide slot, movable along it) are direct applications of known microwave measurement/phase-shifting components to the claim 13–14 feed network, with predictable results. Likely obvious.

5. Articulated motivation to combine (KSR factors)

For a formal rejection, the motivation would be stated as follows (each grounded in the verified references):

1. Common problem, common field. Both A and B address integrating an antenna into a vehicle mirror without enlarging the mirror case or impairing mirror function — the same problem and field, satisfying the KSR "reason would have been apparent" prong.
2. Explicit teaching of the needed direction. A expressly teaches radiating a beam in the visual-field direction of the mirror; B expressly identifies that its antenna cannot radiate in the mirror's direction. A PHOSITA reading B against A is directly prompted to relocate/reshape the radiating structure so it radiates through the mirror plane — the essence of claim 1.
3. Predictable result of a known technique. Using one conductive layer for dual functions (radiative and reflective) is a predictable, space- and part-saving application of known conductive-layer integration; no new physical principle is required.
4. Design incentive / market pressure. Automotive radar and cellular antennas on mirrors created competitive pressure to add function without enlarging the mirror assembly — a recognized KSR incentive.
5. Reasonable expectation of success. Slot arrays with narrow slots (per the patent's own observation that "each of the slots … has an extremely small width") and thin microstrip layers are consistent with preserving the mirror's visual function, so the combination would not have been expected to fail.

6. Counterarguments: why a robust rejection is not free

I must be candid about the weaknesses, and about the limits of my evidence base:

1. Neither verified reference expressly discloses the dual-use limitation. A teaches a separate, light-transmissive reflector placed in front of the mirror; B teaches an antenna behind an ordinary mirror. The step "at least a part of the antenna element functions as a part of said reflecting mirror surface" is the invention's core, and the record I retrieved does not contain a reference expressly showing a mirror's reflective layer doubling as the antenna's conductive element. A rejection would likely need a third reference (e.g., a slot-array/slotted-waveguide document, or a document showing a conductive mirror layer used as an antenna ground plane) to bridge this gap. I could not verify such a reference, because the 34-entry citation table could not be retrieved.
2. The patent was allowed over the two background references, and the applicant argued a concrete, non-trivial benefit (solving B's self-identified inability to radiate through the mirror). That gives a colorable non-obviousness argument even post-KSR.
3. No secondary considerations of record. Given the earlier finding that no litigation involves US 6,081,237 and the patent is expired (anticipated expiration 2018-09-08), there is no licensing/commercial-success evidence either way — so nexus-based rebuttal and objective-indicia arguments are unavailable to either side.
4. Priority-date hazard for any added art. Any reference relied upon must pre-date 1998-03-05. The two Mitsumi references surfaced (JPH11266120A, JPH11220325A; 1999) and US6259412B1 (2001) are too late to serve as art and must be excluded — a point where a sloppy rejection would fail.

7. Bottom line

• Claim 1: Obviousness is arguable, not airtight, on JP-A-54-45040 + Japanese Utility Model Publication 52015/1991 plus the known dual-use of a conductive layer; a third, unverified reference (or the classification-level patch/slot-array art) would materially strengthen it.
• Claims 2, 4–7: Strongest obviousness case — they map onto the well-developed patch-antenna (H01Q9/0407 / H01Q21/065) and slotted-array (H01Q21/064) corpora, with B supplying the microstrip teaching.
• Claims 3, 8–12: Likely obvious as routine manufacturing/optimization choices (printed-on-glass conductors; lateral placement; dielectric/ground extent; ground-as-reflector).
• Claims 13–17: Likely obvious over phased-array beam-steering art and classic sliding-probe/slotted-line phase-shifter components.

Confidence and honesty statement: The claim 1–2 analysis rests on prior art verified in the authoritative patent text. The dependent-claim analysis rests on classification-defined fields of art and general knowledge; I could not retrieve the actual "Patent Citations (34)" list for US 6,081,237, so I have not named specific § 103 references I could not verify. To confirm or refute the analysis with a formal rejection, the authoritative next step is to open the Google Patents "Citations" table (or USPTO PatentCenter / Espacenet / Global Dossier for the JP family) and populate § 6, item 1 with the concrete slot-array/dual-use documents cited against this patent.