US 5239545

I'll run targeted searches for this exact patent number across patent and litigation sources.

Let me check specifically for litigation and the reissue/assignment history.

US 5,239,545 — Verified Record

Direct answer to the lookup request: I found no CAFC (Federal Circuit) docket activity for this patent, and I want to be explicit about the limits of that finding rather than imply a clean bill of health. Searches combining "5239545" with CAFC/Federal Circuit/litigation returned no case involving this patent; the only prominent hit on that numeric string in a court database was courtlistener.com/api/rest/v4/investments/5239545/, which is a financial-disclosure investment row ID for a Lord Abbett mutual fund — a coincidental number collision, not a patent case. I could not query PACER or CourtListener's RECAP docket search directly through the tools available, so my litigation finding is a "not found" rather than a verified "no litigation exists." That distinction matters here, and I flag it as the main uncertainty in this report.

Bibliographic data (from the patent text itself)

Abstract (verbatim)

"A CM (105) receives requests for data transfer from a series of UMs (101-103) and from an EM (104). The requests contain the UM (101-103) or EM (104) address and the size of the data packet to be transferred. The CM (105) processes the requests on a FIFO basis, stores the requests in a queue and assigns either a small data channel or a large data channel, depending on the packet size to be transferred, and also the corresponding number of required timeslots. The CM (105) picks the first request off the queue and sends a grant to the particular UM (101-103) or EM (104) which receive the grant and immediately access either the assigned small or large data channels in the required number of timeslots."

Plain-language overview of the independent claims

Claim 1 — Control module (apparatus). A control module that manages access to data channels in an RF TDMA system serving several user modules. Two or more user modules have each sent an access request. The control module: (a) provides repeating TDM frames with a data channel in each frame; (b) generates an access grant command; (c) receives at least both the first and second access requests within the same first TDM frame; (d) determines which of those requests arrived first; (e) awards channel access based on that determination; and (f) sends the grant in that same first TDM frame to the winner. In short: centralized, first-come-first-served arbitration where competing requests are collected in one frame and the winner is granted inside that frame.

Claim 5 — RF TDMA communication system. The system-level counterpart, adding the user-module side. A user module sends its access request during the first TDM frame; the control module receives it, assigns the channel in response, and sends the grant back to that user module during the first TDM frame; the user module then receives the grant and accesses the data channel in TDM frames following the first frame. This is the claim that captures the request-then-access-across-frames timing cycle.

Claim 12 — Method at the control module. The method-claim analogue of claim 1: provide repetitive TDM frames and a data channel, generate a grant command, receive first and second access requests in the first frame, determine which arrived first, assign access, and send the grant in the first frame to the winning module.

Claim 13 — Method, system-wide. The method analogue of claim 5, including the user module sending a request in the first TDM frame, the control module receiving/assigning/granting within that frame, and the user module accessing the channel in subsequent frames.

Notable claim-drafting quirks worth flagging (I am reading the text literally, per instruction, and not correcting it):

• Claim 1 contains a duplicated word: "assigning access to said said data channel." Compare claim 12, which reads "assigning access … to said at least one data channel." The claims are not verbatim parallel.
• Claim 1 recites "repetitive TDM frames," whereas the Summary of the Invention and the specification's workflow describe "repetitive TDMA timeslots." The apparatus claims and the descriptive sections use different terminology for the same construct.
• Claim 19 (method claim depending from method claim 18) recites "means for processing the first access request" — apparatus language inside a method claim.

Dependent-claim map

• Claims 2–4 (from claim 1): linking the control module to external modules; Ethernet-type LAN linking; external modules permitted to send their own access requests.
• Claims 6–11 (from claim 5): request specifies how many subsequent frames are needed; FIFO queueing of requests; processing the first-queued request; granting to the first-queued requester; multiple data channels per frame; 256-byte channel size.
• Claims 14–15 (from claim 13): Ethernet LAN linking; external-module requests.
• Claims 17–20 (from claim 16): same functional family as 6–10, expressed as method steps.

The independent claims contain no explicit "FIFO" limitation on their face — FIFO is the disclosed and claimed (claims 7–9/18–20) mechanism, but independent claims 1/12 use the broader "determining which … was received first."

Related family / co-pending application

The specification cross-references U.S. patent application Ser. No. 07/608,867, "Scheduling in a Communication System," in behalf of Buchholz et al., filed on the same date herewith, assigned to the same assignee. Google Patents' "Similar Documents" list shows US 5,307,348 "Scheduling in a communication system" (1994-04-26), consistent with that sibling application. This patent has no family members listed (Family ID 24438777 shows only the single US application).

Prior art cited on the face of the patent (11 references)

US RE32,789 (Motorola, transmission trunk multichannel dispatch with priority queuing); US 4,517,669 (Motorola); US 4,581,736 (Communications Satellite Corp.); US 4,665,519 (Electronic Systems Technology); US 4,688,212 (Harris); US 4,819,229 (University of Strathclyde, LAN priority control); US 4,831,373 and US 4,870,408 (both Motorola, dynamic data channel allocation on a trunked system); EP 0,299,538 A2 (NEC); US 5,008,883 (U.S. Philips); US 5,012,469 (Sardana, adaptive hybrid multiple access protocols). Non-patent citation: The Bell System Technical Journal, "Advanced Mobile Phone Service," Jan. 1979, vol. 58, No. 1, Part 3, pp. 43–69.

Downstream use of this patent as prior art

US 5,239,545 was cited against later applications, including as an "[YA]" reference in EP 0 986 212 A3 (Tachyon, "Method and apparatus for multiple access in a communication system," 2001-01-10) and as a category "A" reference in WO 1998/010540 A3 (Nokia, "Data transmission method, and radio system"). Google Patents reports 114 citing publications overall.

Number-collision warnings (do not conflate)

Two unrelated records share the digits "5239545" and should not be merged with this patent:

1. JP Patent No. 5239545 (特許第5239545号) — a glucose-concentration measuring device with ring-shaped light-beam forming means, filed 2008-06-20 in Japan. Different jurisdiction, different subject matter, different owner.
2. CourtListener investment ID 5239545 — a Lord Abbett Short Duration Income Fund holding in a judicial financial-disclosure filing.

Timeline note relevant to your CAFC-2026 request

This patent's term ran from the 1990-11-05 filing to the anticipated expiration of 2010-11-05, and Google Patents records a final 12-year maintenance fee payment on 2004-12-03 with no later payment. A patent that expired in 2010 cannot be the basis of an infringement action filed in 2026 (any § 286 damages window would require infringing activity after roughly 2020). So the absence of 2026 CAFC activity is consistent with the patent's expired status — but that consistency is an inference from the expiration date, not a substitute for an actual docket check. If you need a litigation answer you can rely on, it should be confirmed against PACER or a docket service (CourtListener/RECAP, Docket Alarm, RPX) queried by patent number; I was unable to do so with the tools available here.

I'll run targeted litigation searches for this exact patent number.

Let me check patent-litigation-specific sources directly.

Let me run a few more targeted checks before concluding.

Litigation Search — US Patent 5,239,545

Direct answer: I found no litigation involving US Patent 5,239,545. No district court, ITC §337, CAFC, PTAB, or UPC proceeding naming this patent appeared in any of the searches I ran. I want to be precise about what that finding is and is not, because a negative result from web search is weaker than a docket-confirmed clearance.

What I searched

Because the last query did not execute, my search was not exhaustive. That matters for the confidence level I claim.

Explicitly excluded — number collisions that are not this patent

The number string "5239545" is heavily contaminated by unrelated records. Per the strict no-auto-correction rule, these are separate identifiers and I am not merging them with the patent:

1. CourtListener investment ID 5239545 — a Lord Abbett Short Duration Income Fund (LALDX) holding row in a judicial financial-disclosure filing (courtlistener.com/api/rest/v4/investments/5239545/). This is a database primary key, not a case. It is the single most common false hit on this string.
2. JP Patent No. 5239545 (特許第5239545号) — a glucose-concentration measurement device using "ring-shaped light beam forming means," filed 2008-06-20 (J-GLOBAL ID 201303022400245535). Different jurisdiction, subject matter, and owner.
3. Brazilian appeal No. 5239545-61.2020.4.03.9999 — TRF-3 social-security (auxílio-reclusão) case involving the INSS. Unrelated to patents.
4. Various administrative identifiers — a US FWS property-owner list entry ("5239545 Pat McVie"), a Lithuanian registry notice number, an Argentine Boletín Oficial publication number, and an Iowa copyright/likeness case (Griner v. King) that only coincidentally contains the dollar figure "$531.45."

Why the absence of litigation is consistent — but not proof

From the record already established for this patent:

• Term ran 1990-11-05 → 2010-11-05 (anticipated expiration). Google Patents records the final maintenance fee at the 12-year interval on 2004-12-03, with no further payment. Status: Expired – Lifetime.
• A patent that expired in 2010 cannot support a damages claim for conduct in or after 2026 (35 U.S.C. §286's six-year lookback would require infringement since roughly 2020). So the absence of current litigation is expected.
• The most plausible assertion window would have been the mid-1990s, when Motorola was actively enforcing data-communications patents. I found no record of such a case either — but this is a "not found," not a verified "never happened," and pre-PACER-era filings are exactly the kind of thing that is thinly indexed on the open web.

Note the inherent asymmetry: the presence of this patent as prior art is well documented (cited as category "[YA]" in EP 0 986 212 A3 / Tachyon, and as category "A" in WO 1998/010540 A3 / Nokia). That kind of citation activity is a frequent byproduct of litigation-driven invalidity work, but it is also routine prosecution practice, so I do not treat it as evidence that this patent was ever asserted.

Confidence and recommended verification

For a litigation answer you can rely on for a legal purpose, this needs docket-service confirmation. Since the patent issued in 1993 and expired in 2010, the relevant venues span the pre-CM/ECF era:

• PACER — District Courts (D.C., N.D. Ill., E.D. Tex., and Motorola's home venues are good starting points), and the Federal Circuit docket for any appeal.
• CourtListener / RECAP — docket search by patent number (courtlistener.com/?q="5,239,545" type=RECAP), which would catch anything post-2009.
• Docket Alarm, RPX Insight, Lex Machina, Darts-IP — the paid services that actually index pre-2000 filings and ITC §337 investigations by patent number.
• USITC EDIS — for any Section 337 investigation; the 1990s saw several Motorola §337 actions, though I found none naming this patent.

I'd also flag the possibility that the patent was asserted together with its sibling — US 5,307,348, "Scheduling in a communication system" (Ser. No. 07/608,867, filed the same day, Buchholz et al.). If a case exists, it may be indexed under the sibling's number rather than '545. That is a hypothesis worth checking, not a finding.

Bottom line: no known litigation involving US 5,239,545. I found zero cases — no plaintiff, defendant, jurisdiction, case number, filing date, or outcome to report — and the string is dominated by unrelated collisions that should not be mistaken for a docket. One search query did not execute, and pre-2000 filings are poorly indexed on the open web, so I recommend confirming against PACER and a commercial docket service before treating this as a definitive no-litigation opinion.

PTAB / AIA Trial Proceedings — US 5,239,545 ("Channel access control in a communication system")

Proceedings overview

Total AIA trial proceedings on file: 0. The structured USPTO Open Data Portal block included with this prompt returns no inter partes review, post-grant review, or covered business method review for US 5,239,545 — zero active, zero with claims invalidated, zero with claims sustained, zero settled, zero institution denials. My independent web searches for the patent number combined with "IPR," "PGR," "CBM," "PTAB," "petition," and the patent title surfaced no petition, institution decision, final written decision, or Board appeal for this patent; the only numeric hits on the string "5239545" in that corpus were coincidental (see the collision note below). The defensive posture this gives a defendant is not "hardened patent" and not "claims canceled" — it is "no live patent at all." US 5,239,545 expired on 2010-11-05 (anticipated expiration per Google Patents), fifteen years before today's date of 2026-09-22, so there is nothing for the Board to have invalidated and nothing left for anyone to assert. Any demand letter citing this patent is defective on its face for reasons that have nothing to do with AIA trials.

Because the count is zero, the per-proceeding template below is populated for no proceeding; instead I document why the zero is credible, and what the statutory landscape would have permitted.

(No proceedings) — no petitioner, no patent owner party

• Type: N/A — no IPR, no PGR, no CBM on file.
• Filed: N/A.
• Status: No AIA trial proceedings on file (USPTO Open Data Portal, per the structured block supplied with this prompt). Plain-English gloss: no petition was ever filed, or none was indexed; no trial was ever instituted.
• Judge panel: None. No APJ panel has ever been assigned to this patent.
• Petition grounds: None of record — no § 102 or § 103 grounds were ever pleaded at the Board, and no § 112 ground, which in any event is not an IPR-eligible basis absent an IPR-PGR hybrid petition under § 311(b).
• Institution decision: None — no Director or panel decision to institute or deny exists for this patent.
• Final Written Decision: None. No claim of US 5,239,545 has ever been canceled, disclaimed, or held unpatentable by the PTAB. Equally, no claim has ever been held patentable by the PTAB — the claims are simply untested at the Board. Given the § 282 presumption never mattered and the patent is expired, "untested and unenforceable" is the accurate description, not "upheld."
• Settlement / termination: N/A. There were no parties to settle.
• Appeal: No PTAB final written decision exists, so there is no § 6 / § 141 appeal to the Federal Circuit from this patent. (This is consistent with, and independent of, the earlier section's "no CAFC docket activity found" finding — that finding was already flagged there as a "not found" rather than a verified negative.)
• Defensive value: None is conferred by PTAB, because there was no PTAB. The defensive value here comes entirely from expiration: the patent's term ran to 2010-11-05 and its final maintenance fee was paid 2004-12-03 for the 12-year interval, with no later payment recorded. Under the pre-URAA transition rules a patent filed 1990-11-05 takes the greater of 17 years from issue (1993-08-24 → 2010-08-24) or 20 years from filing, so the operative expiration is 2010-11-05. Accused conduct occurring in 2026 cannot infringe this patent at all.

Why the zero is credible rather than an indexing gap

Three structural reasons the absence of proceedings should be read as real, not as an ODP lag artifact:

1. Statutory availability window. IPR became available on 2012-09-16 (AIA § 6(c)(2)(A)), roughly 22 years after this patent's 1990-11-05 filing date. By then the patent's remaining term was only about two months — to 2010-11-05 has already passed, i.e., the patent was already expired before the first IPR could be filed. PGR was never available: it requires an effective filing date on or after 2013-03-16, and this application was filed 1990-11-05. CBM likewise never fit — the claims are directed to TDMA channel arbitration, not a "financial product or service," and the CBM program has in any event been unavailable for new petitions since 2020-09-16.
2. No economic incentive. IPR is not free; a petitioner pays USPTO fees plus counsel. No rational petitioner spends that on an issued patent that has already lapsed.
3. Assertion history. The patent was never asserted in a way that generated counter-petitions (see the earlier CAFC/litigation section, which found no case involving this patent). Well-asserted patents attract IPRs; unasserted, expired patents do not.

⚠️ Number-collision warning (extended)

The earlier section flagged two collisions on "5239545." My searches surfaced a third, in the PTAB/legal database context specifically:

This is exactly the failure mode that produces fabricated proceeding numbers in AIA reports, so I am stating plainly: I did not find, and I am not supplying, any IPR/PGR/CBM number for this patent.

Strategic summary

Claim status. All 20 claims — independent claims 1, 5, 12, and 16 and the dependent claims mapped in the earlier section — are untested at the PTAB and expired. None is CANCELED, none is SUSTAINED (a Board "sustain" requires a trial that never happened), and all are now in the public domain as of 2010-11-05. The practical consequence is one a litigator should not overcomplicate: the correct answer to a 2026 assertion of US 5,239,545 is a Rule 11 / § 285 letter pointing to the expiration date, not an IPR petition. There is no live claim to invalidate.

Estoppel landscape. § 315(e)(2) and § 325(e)(2) estoppel attach to a petitioner after a final written decision, and § 315(e)(1) attaches after institution. With no petition ever filed, no party is estopped with respect to this patent, and conversely no party has a free pass — because there is no controversy in which estoppel could matter. If you encounter a demand letter, your prior-art defenses are entirely unconstrained (no § 315(b) one-year bar clock has ever started, since no civil action was served on a petitioner here), but they are also largely academic given expiration. Note one nuance if anyone ever tries to resurrect the family: an IPR can be filed against an expired patent (the Board can still decide patentability, typically with no claim-amendment path for the owner), so "it's expired" is a reason nobody bothers, not a jurisdictional bar the Board would apply.

Pattern signals. No repeat-petitioner pattern (no petitioner at all). No defensive aggregator — Unified Patents does not appear anywhere in the record for this patent; Unified's business model targets asserted patents, and this one was never asserted. Patent owner Motorola Solutions (originally Motorola, Inc.) has not pursued any PTAB appeal concerning this patent. The sibling application cross-referenced on the face of the specification — US 07/608,867, "Scheduling in a Communication System" (Buchholz et al., filed the same day), which issued as US 5,307,348 — is a separate patent requiring its own separate PTAB check; I did not verify its trial history and you should not assume it mirrors this one.

Recommended next steps

1. If you receive a demand letter citing US 5,239,545: do not budget for an IPR. Respond with the expiration date. The controlling facts are the 1990-11-05 filing, the 1993-08-24 issue date, and the 2010-11-05 anticipated expiration — all documented in the patent record and reproduced above. Because the patent expired more than 15 years ago, the § 286 six-year damages lookback (which would reach back only to roughly 2020-09-22) captures zero potentially infringing activity. Any infringement theory is therefore baseless, and continued assertion after notice may support fees under § 285.
2. Do not cite a PTAB decision for this patent — there is none. If a colleague or a vendor report hands you an "IPR number" for US 5,239,545, treat it as a hallucination or a number collision until independently confirmed in PTAB E2E (https://ptab.uspto.gov) or the PTAB API.
3. If you need a belt-and-suspenders verification (this report relied on the USPTO ODP structured block plus web search, and I could not query PTAB E2E or the PTAB API directly with the tools available): run the patent number through the USPTO PTAB API (https://developer.uspto.gov/api/patents/patent-trials) and PTAB E2E, and separately check the ex parte reexamination path (the "90/" series control numbers) — my searches found no reexamination certificate or request for this patent, but I am flagging that as not independently verified rather than as a confirmed negative. Reexamination, unlike IPR, has been available since 1981 and is the one route that could theoretically have touched a patent this old.
4. If your real interest is the patent family, run the same check on US 5,307,348 and any continuations, since a live family member would matter far more than this expired parent. That check is outside the scope of what I was able to complete here.

I'll verify the assignment chain against live sources before writing up.

Ownership Analysis — US 5,239,545 "Channel access control in a communication system"

Verification basis and its limits (read first). I could not run a live fielded query against the USPTO Assignment Center (assignmentcenter.uspto.gov) with the tools available here — that is a form-based database, not a searchable index page, and targeted URL/text searches for this patent number returned no assignment-center record view. My chain below is therefore built from the authoritative patent text supplied in this analysis (Google Patents legal events, "Legal Events" section for US 5,239,545), corroborated by uspto.report/patent/grant/5239545, Justia Patents, and Florida Sunbiz corporate records. Two follow-up searches — "005508/0922" and a query aimed at uspto.report's assignment panel — returned zero results, so the correspondent-of-record field remains unverified. I state that plainly rather than filling the gap.

Inventors

Pattern check — no anomaly. The classic fire-sale precursor (all inventors departing the assignee within 12 months of filing) is not present and not even testable here: there is a single inventor, and he assigned to Motorola six days before the 1990-11-05 filing date, which is the standard "assign-before-file" practice at a large corporate filer, not a distress signal. There is no second-named inventor who could have decamped.

Related-party note: the specification cross-references co-pending Ser. No. 07/608,867, "Scheduling in a Communication System," Buchholz et al., filed the same day, same assignee. That sibling issued as US 5,307,348 (1994-04-26). Its ownership chain is separate from this one and is not asserted in this report — I have not verified its assignment records, so do not assume it mirrors the chain below.

Original assignee

Motorola, Inc. (Schaumburg, IL), as named on the issued patent's front page (Justia: "Assignee: Motorola, Inc. (Schaumburg, IL)") and as assignee of record on Reel 005508 / Frame 0922.

• Primary line of business: at the 1990 filing, Motorola was a diversified public electronics manufacturer — the dominant supplier of land-mobile radio, trunked dispatch, and public-safety communications systems, and by the early 1990s also a cellular and semiconductor player. This patent sits squarely in that core business: RF TDMA channel-access control for a wireless LAN / data-over-radio product line (the specification's user modules, control module, and Ethernet-LAN backhaul to data terminals).
• Did they ship a product embodying the claims? The patent describes a specific, buildable system — 2 ms half-duplex RF TDM frames, a 660-byte request timeslot of 12 × 55-byte slots, 256-byte fragments, a Motorola 68000 processor, a Seeq FLASH NQ48F512K-300 EPROM, an AMD LANCE chip set with a National coaxial transceiver on the Ethernet side, and an internal "network interface 245" fast packet switch. That is an engineering bill of materials for a Motorola product program, not a paper design. I can state with high confidence that the disclosed architecture was an internal Motorola development; I cannot confirm from the sources retrieved that a commercial SKU shipped with these claim elements, so I mark product-shipping as "strongly indicated but unverified." Do not cite this as a confirmed product-shipping finding.
• Current status: Operating. Motorola, Inc. changed its legal entity name to Motorola Solutions, Inc. effective 2011-01-04, immediately following the Motorola Mobility separation. This is documented in Motorola's own separation FAQ and in the Florida Division of Corporations record for document number 830046 ("NAME CHANGE AMENDMENT | 01/05/2011 | OLD NAME WAS: MOTOROLA, INC."). Motorola Solutions remains an active NYSE-listed company (MSI). No bankruptcy, dissolution, or asset-sale event touches this patent.

⚠️ FLAG — contradiction to carry forward. The previously generated summary lists "Current Assignee (as listed): Motorola Solutions Inc." from Google Patents, flagged by Google as possibly inaccurate. No recorded assignment in the patent's legal events supports that entry. Google's assignee string for this patent is best explained by entity-name mapping (Motorola, Inc. → Motorola Solutions, Inc., 2011 name change), not by a recorded USPTO assignment. Treat "current assignee" as Motorola Solutions, Inc. by corporate name change, with the caveat that I found no reel/frame for a change-of-name recording for this patent. If Motorola never recorded a Rule 3.21-style change-of-name for its legacy portfolio — which is common and permissible when no assignment occurred — that is why no such record appears, and it does not create an ownership gap.

Assignment timeline

There is exactly one recorded assignment in this patent's legal events. There is no post-issuance assignment chain — no NPE transfer, no security interest, no merger, no license recordation, no correction.

• 1990-10-30 (executed) / recorded 1990-11-05 — Reel 005508 / Frame 0922
  • Conveyance: Assignment — recorded under code AS, caption "ASSIGNMENT OF ASSIGNORS INTEREST" (free-format text: "ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BUCHHOLZ, DALE R.;REEL/FRAME:005508/0922")
  • Assignor: Dale R. Buchholz (individual inventor)
  • Assignee: Motorola, Inc. (Illinois)
  • Correspondent: NOT RETRIEVED. This is the specific field the task asks me to capture, and I could not obtain it — the Google Patents legal-events record does not expose a correspondent, and the Assignment Center record view was not reachable. What the patent front page does disclose is the prosecution attorney group, which is a different field and must not be conflated with the assignment correspondent: Richard A. Sonnentag, Raymond A. Jenski, and Raymond J. Warren (Justia "Attorneys" field). If you need the true correspondent of record for reel 005508/0922, pull the assignment image directly from the Assignment Center — the reel/frame is known and the record is a single-page 1990-era Motorola cover assignment, almost certainly a Motorola Patent Department in-house filing. I flag that as an inference, not a finding.
  • Context: Routine pre-filing assignment of employee invention to employer. Executed six days before the 1990-11-05 filing date — standard corporate practice, not a transfer driven by litigation, financing, or distress.

Subsequent legal events (not assignments, listed for completeness of the ownership record):

• 1993-08-11 — STCF, Patent granted (issue date 1993-08-24).
• 1996-11-20 — 4-year maintenance fee paid.
• 2001-02-02 — 8-year maintenance fee paid.
• 2004-12-03 — 12-year maintenance fee paid.
• 2010-11-05 — Anticipated expiration; status now Expired – Lifetime. No later fee payment is recorded.

How the timeline ends. The chain terminates at the original assignee because the patent expired 2010-11-05 while still held by Motorola/Motorola Solutions. There is a structural reason no asserter ever touched it: the patent died two months before the January 2011 name change completed, and roughly fifteen years before the 2026 assertion wave this analysis series is tracking. Any 2020s-era NPE acquisition of this asset would have purchased a fully expired patent — no enforceable term, therefore no rational acquisition. That is a strong, date-based explanation for the empty chain, not merely an absence of searching.

Timeline diagram

timeline
    title Ownership of US 5239545
    1990 : Assignment executed by inventor Buchholz
         : Recorded to Motorola Inc reel 005508 frame 0922
   1990 : Application filed 1990-11-05
    1993 : Patent issued 1993-08-24
    2004 : Final maintenance fee paid
    2010 : Patent expires 2010-11-05
    2011 : Motorola Inc renamed Motorola Solutions Inc

NPE / patent-troll pattern signals

Net signal count: zero. There is not one weak signal, let alone a strong one. Notably, the most common way a 1990s Motorola patent ends up in an NPE chain — a bulk assignment of a legacy portfolio to a licensing vehicle — did not happen to this patent, and the 2010 expiration date makes it economically inert.

Verdict

Insufficient data (only the original assignment).

The ownership record for US 5,239,545 consists of a single recorded assignment — reel 005508/0922, executed 1990-10-30 by inventor Dale R. Buchholz in favor of Motorola, Inc., recorded 1990-11-05 — followed by maintenance-fee payments in 1996, 2001, and 2004, and expiration on 2010-11-05. There is no post-issuance chain, no LLC, no security interest, and no asserter, so no NPE verdict can be substantiated on this record; the only reason this is "insufficient data" rather than a clean negative is that the sole correspondent-of-record field requested was not retrievable with the tools available to me. The practical ownership conclusion is nonetheless firm: this was a captive Motorola industrial patent that expired in 2010 in the hands of Motorola Solutions, Inc. (by the 2011-01-04 name change), and it was never asserted or transferred.

Verify at:

• USPTO Assignment Center — search by patent number 5239545: https://assignmentcenter.uspto.gov/
• USPTO Patent Assignment Search (legacy interface, same underlying records): https://assignment.uspto.gov/patent/index.html
• Legal-events source relied on: https://patents.google.com/patent/US5239545/en#legal-events
• Front-page assignee/attorney data corroboration: https://patents.justia.com/patent/5239545
• Name-change corroboration (Florida Sunbiz, entity 830046, amendment 01/05/2011): https://search.sunbiz.org/Inquiry/CorporationSearch/NameHistory?aggregateId=forp-830046-bf766eb1-d628-47d4-92b4-14d07673ca86

Recommended single follow-up if this matters to a filing or opinion: retrieve the assignment image for reel 005508, frame 0922 directly in the Assignment Center and read the correspondent block off the document itself. Everything else in this chain is settled.