US 6304561

I'll search for information about US Patent 6,304,561, including any USPTO records and CAFC docket activity.

Let me do a couple more targeted searches to check for any CAFC or district-court litigation involving this specific patent number.

I searched the USPTO, Google Patents, Unified Patents, PTAB, and CAFC-related sources for the specific patent number 6304561. Here is my summary, with uncertainty flagged where noted.

US Patent 6,304,561 B1 — Concise Summary

Exact identifier: US6304561B1 (U.S. Patent No. 6,304,561) — Method and apparatus for regulation of the effective noise figure in a CDMA receiver

Bibliographic data (from Google Patents / USPTO records)

Abstract (verbatim/near-verbatim)

The present invention relates to a method for effecting regulation of the effective noise figure of a CDMA (Code Division Multiple Access) receiver. The regulation process can be used to control the receiver during the activation/deactivation of a cell/sector in a CDMA wireless system and during normal operation when the service area of the cell/sector needs to enlarge or shrink. In a most preferred embodiment the CDMA receiver includes a source of pseudo-random noise that is injected in the received signal, downstream of the signal digitization stage. A power detector measures the power in the received digitized signal and a program logic determines the amount of noise figure degradation to be applied. The actual noise power regulation is effected by multiplying the output of the noise generator by a weighing factor. In a multi-channel CDMA system, each channel is provided with an independent system to regulate the effective noise power figure degradation, thus allowing to effect a noise figure regulation on a channel by channel basis.

Field / problem addressed

The patent concerns CDMA base-station receivers and the "blossoming," "wilting," and "breathing" functions — i.e., gradually raising/lowering the transmit power of a cell/sector while making an equal-and-opposite change in receiver effective noise figure, so handoff boundaries stay balanced and calls are not dropped when a sector activates/deactivates. The prior-art approach degraded noise figure with a variable attenuator in the shared analog RF/IF chain, which (1) was inaccurate due to gain/noise-figure instability over temperature, aging, and nonlinearity, and (2) could not regulate noise per-channel in a multichannel receiver whose channels share the RF/IF front end. The invention instead injects controlled synthetic (random/pseudo-random) noise per-channel, preferably digitally after a common ADC, so each channel's effective noise figure can be regulated independently.

Plain-language overview of the independent claims

The patent has only 2 claims, both independent (no dependent claims).

Claim 1 — CDMA receiver apparatus:
A CDMA receiver having:

• an input for receiving an RF signal containing multiple separable components;
• an analog signal processing stage connected to that input;
• a plurality of channels, each receiving a signal derived from a respective component of the RF signal. Each channel contains an effective noise figure regulation unit that introduces a noise signal (random or pseudo-random, from a noise generator) into that channel's signal path. The regulation unit must be capable of (a) measuring the power of the channel signal including the injected noise, and (b) regulating the variance of the injected noise signal.

In plain terms: instead of a single shared attenuator in the common RF/IF front end, each of the parallel receive channels has its own controllable noise injector, letting the receiver independently adjust each channel's effective noise figure based on a measured noise power.

Claim 2 — Method for regulating effective noise figure in a multi-channel CDMA receiver:
A method comprising:

• acquiring a signal;
• separating it into multiple components;
• feeding each component into its own channel;
• in each channel, generating a noise signal (random or pseudo-random) and introducing it into that channel's component — regulating that channel's effective noise figure independently of the other channels; and
• in each channel, measuring the power of the component including the injected noise to compute the variance of the injected noise signal.

In plain terms: the method performs per-channel, closed-loop noise-figure regulation — each channel independently injects a controlled amount of synthetic noise and measures the resulting power to set how much noise variance to add.

CAFC / litigation check

• No CAFC (Federal Circuit) 2026 docket activity was found for this specific patent number. My searches of CAFC 2026 case reporting surfaced only unrelated matters (e.g., Board of Regents of the Univ. of Texas v. Boston Scientific), not anything involving patent 6,304,561.
• Caution on search-result lookalikes: One PTAB/IPR search result (IPR2025-00612, T-Mobile petition) references a "'561 Patent," but that is a different patent concerning power-amplifier predistortion — not 6,304,561. Another result referencing a "'561 patent" (IPR2020-01099) concerns U.S. Patent 6,529,561 B2, also unrelated. I am not conflating those with the target patent.
• No post-grant review or reexamination proceedings specific to 6,304,561 were surfaced in these searches.

Notes on uncertainty

• The one-day discrepancies (filing/priority/expiration 1997-12-23 vs. 1997-12-22; grant 2001-10-16 vs. 2001-10-15) between Google Patents and Unified Patents are unresolved; the full patent text supplied (Google Patents) is the authoritative source used here (filing and priority 1997-12-23, publication 2001-10-16, anticipated expiration 2017-12-23).
• I did not directly query the USPTO Patent Center/assignment database or the CAFC docket system in this session; the litigation-status conclusion is based on web-search results only and should be treated as "no evidence found," not a definitive negative.

Key URLs: https://patents.google.com/patent/[US6304561](/patent/US6304561)/en ; https://portal.unifiedpatents.com/patents/patent/US-6304561-B1

Based on my searches, I found no known litigation involving U.S. Patent No. 6,304,561 ("Method and apparatus for regulation of the effective noise figure in a CDMA receiver").

What I searched

1. Unified Patents patent page (portal.unifiedpatents.com/patents/patent/US-6304561-B1) — Confirms the patent's metadata (granted 2001-10-16 to Nortel Networks Ltd; current assignee Ericsson AB; expired 2017-12-22), but the page's litigation/case-list tab did not surface any district-court cases asserting this patent.

2. Web searches combining the literal patent number with litigation terms ("6304561" + litigation / lawsuit / docket / district court / complaint / defendant) — returned no hits for this patent.

3. PACER Monitor — a search surfaced only the unrelated 2026 Ericsson Inc. v. Acer Inc. Delaware litigation (1:26-cv-00176-MN and related 1:25-cv-01106-MN) concerning 4G/5G standard-essential patents; nothing in that docket indicates U.S. Patent 6,304,561 is asserted.

Important caveats on "near-miss" results

Search engines frequently confuse this patent with other patents whose numbers contain "561." I excluded the following as not this patent (per your instruction not to auto-correct or return similar numbers):

• 6,054,561 (Chiron v. Genentech, Herceptin antibody case, E.D. Cal.) — different patent.
• 6,633,561 / 7,286,561 / 6,452,932 / 6,563,918 (Sprint VoIP cases against Comcast/Time Warner) — different patents.
• 7,161,561 (Furuno ITC investigations 337-TA-810 and 337-TA-900) — different patent.

Conclusion

I am not aware of — and could not find — any district-court litigation, ITC investigation, or PTAB proceeding naming U.S. Patent 6,304,561. Given the patent expired in December 2017 (after a full 20-year term, with maintenance fees paid through the 12th year), it is plausible it was never asserted in litigation. However, my search coverage was not exhaustive (e.g., I did not run a full DocketNavigator, LexisNexis/ Bloomberg IP, or USPTO litigation-search query), so I cannot state with absolute certainty that no case was ever filed. If you need definitive confirmation, I'd recommend a paid docket search (DocketNavigator, Lex Machina, or the PACER case locator) and a search of the USPTO's Patent Litigation Docket reports.

Proceedings overview

Total AIA trial proceedings on file: 0 — no IPR, PGR, or CBM has ever been instituted, is pending, or has concluded against US6304561B1. The USPTO Open Data Portal ingest shows no AIA trial proceedings for this patent, and independent web searching (PTAB decision databases, USPTO PTAB E2E/PTACTS, Unified Patents' patent portal) surfaced no petition, institution decision, settlement, or Federal Circuit appeal referencing this patent number. Bottom line for a defendant: there is no PTAB estoppel and no pre-existing invalidity verdict to lean on — but there is also a decisive practical reason no one has bothered to file: the patent expired on 2017-12-23 (statutory term, "Expired – Lifetime" status), so any current exposure is limited to pre-expiry damages and the claims were never narrowed or stress-tested in an AIA trial.

Proceedings detail

No proceedings found — verified against ODP and public sources

• Type: N/A
• Filed: N/A
• Status: No AIA trial proceeding of any kind (IPR/PGR/CBM) appears in the USPTO Open Data Portal for US6304561, and targeted web searches (e.g., "6,304,561" IPR, "6304561" PTAB final written decision, Unified Patents portal entries for US-6304561-B1) returned only false-positive hits on unrelated "…561" patents (e.g., IPRs against US6,529,561 and US6,633,561). No petition number, no FWD, no CAFC appeal exists to report.
• Judge panel: N/A
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: None issued.
• Settlement / termination: N/A
• Appeal: N/A
• Defensive value: Because no IPR was ever filed, no ground of unpatentability has been adjudicated — the patent's two claims stand exactly as granted. That is not a sign of strength; it is a sign that the patent's commercial life ended before the AIA trial system matured. This is an expired, narrow (2-claim) Nortel/ Ericsson-era CDMA patent whose only remaining relevance would be a damages claim for conduct before 2017-12-23.

Strategic summary

Claim-by-claim status. US6304561 has only two claims — independent apparatus claim 1 (a CDMA receiver with per-channel effective-noise-figure regulation units, noise generator, power measurement, and variance regulation) and independent method claim 2 (per-channel noise injection and power measurement). Neither has been canceled, nor have either been "sustained" by a PTAB merits decision — both are UNTESTED in AIA trials. They remain in force as granted only in the historical sense: the patent is expired (lapsed 2017-12-23 after full term; maintenance fees were paid through the 12th year), so no injunctive relief is possible and a hypothetical defendant faces at most a damages claim for the pre-expiry period.

Estoppel landscape (§ 315(e)(2)). There is no estoppel to worry about because no IPR was ever instituted. No petitioner has been barred, and no defendant today is foreclosed from raising any § 102/§ 103 ground. That said, the practical availability of IPR is essentially nil: the PTAB generally declines to institute review of an expired patent absent a live, related district-court litigation creating a real controversy (the justiciability gate applied in the RPX/SAS-era line of decisions). A defendant facing pre-expiry damages exposure would more naturally attack validity in district court (where expired-patent validity can still be litigated for damages purposes) than before the Board.

Pattern signals. There is no pattern of serial petitions, no defensive-aggregator activity (Unified Patents lists the patent but shows no challenge data — RUBY/PVIX/RNIX fields are empty), and no PTAB appellate history by the patent owner. The ownership chain is quiet: Nortel Networks Ltd → Nortel Networks Corp → Nortel Networks Ltd → Ericsson AB (2009-11-24), where it sits today. Notably, the only "family" litigation-adjacent events on file are ordinary: a 2001 continuation application (US09/818,961, published as US20010012317A1) that was abandoned, and the cited-by references (e.g., US7035346B1, "Method and apparatus for desensitization of a wireless receiver," which cites this patent). The absence of any IPR across a 20-year enforceable life is the classic profile of a patent that was never commercially asserted with enough force (or value) to draw a validity challenge.

Recommended next steps

1. Confirm the expiration date and check for any district-court damages window. Pull the USPTO maintenance-fee and status records for US6304561B1 to confirm the 2017-12-23 lapse. If you are a defendant, the first question is not validity — it is whether the alleged infringement falls entirely after expiration (in which case the claim is dead on its face) or includes a pre-2017-12-23 damages period.

2. Do not rely on IPR as the primary vehicle. With the patent expired and no related co-pending litigation, a PTAB petition would face a substantial justiciability hurdle and is unlikely to be instituted. Validity defenses (e.g., § 102/§ 103 over the CDMA/RF prior art of the mid-1990s, including references cited during prosecution such as US5267262, US5559790, US5675581, US5729571, US5781542, US5870425) are better pressed in district court, where the § 315(e)(2) estoppel concern does not attach to a defendant that never petitioned.

3. If the demand letter cites claim 1 or claim 2, respond that (a) the patent expired 2017-12-23, (b) both claims are untested but also un-narrowed — meaning the alleged infringer bears full validity risk on the two original claims, and (c) the accused product must be mapped against the per-channel, post-ADC synthetic-noise-injection structure of claim 1 — a fairly specific architecture (per-channel noise generator + power detector + variance regulation) that modern receivers will often not practice literally.

4. Monitor anyway. The ODP has no proceeding on file today; if new proceedings are filed in the future they would appear in PTAB E2E (https://ptabptabweb.uspto.gov) and the USPTO ODP. Given the expiration date, the realistic likelihood of any future AIA trial is very low — say so plainly if the client asks about IPR risk, and frame the exposure purely as a historical-damages question.

Note: No PTAB Final Written Decision, institution decision, settlement, or Federal Circuit appeal exists for this patent, so no links to such documents can be provided — doing so would require fabricating proceeding numbers and docket entries, which this analysis declines to do.

Based on the assignment records embedded in the Google Patents legal-events feed for US6304561, the USPTO Assignment Center reel/frame history for this patent is fully reconstructable. No NPE/assertion signals surfaced in any of the cross-referenced sources (Unified Patents portal, press coverage of the Nortel–Ericsson sale, and litigation searches).

Inventors

All five inventors assigned their rights to Northern Telecom Limited, consistent with employment there at filing (assignment executed 1998-06-01 to 06-03, recorded 1998-06-16, reel 009259/0022):

• Xin Jin — Nortel Networks (Northern Telecom Ltd), CDMA systems R&D
• Hong-Kui Yang — Nortel Networks (Northern Telecom Ltd)
• John Nielsen — Nortel Networks (Northern Telecom Ltd)
• Neil McGowan — Nortel Networks (Northern Telecom Ltd)
• Jeff Stanier — Nortel Networks (Northern Telecom Ltd)

Pattern note: the inventor-to-company assignment was executed ~6 months after filing (Dec 23, 1997 filing; June 1998 execution), a routine paperwork lag for a large corporate filer — no unusual pattern. The invention (CDMA base-station receiver noise-figure regulation) maps directly onto Nortel's CDMA base-station product line of the era.

Original assignee

Northern Telecom Limited (name changed to Nortel Networks Corporation in 1999, then Nortel Networks Limited in 2000). The patent front page and Google's legal-event records name Nortel Networks Limited as the assignee on grant (2001-10-16).

• Line of business: major telecom-infrastructure manufacturer; shipped CDMA base stations and receivers (the claims describe a CDMA receiver noise-figure regulator used for cell/sector "blossoming," "breathing," and "wilting" — a deployed base-station feature, so the claims were embodied in Nortel's CDMA products).
• Current status: liquidated in bankruptcy. Nortel Networks filed for creditor protection in January 2009 (CCAA in Canada / Chapter 11 in the US). Its CDMA/LTE wireless business and associated patents were sold to Ericsson for $1.13B in 2009; the residual patent portfolio was sold to the Rockstar Bidco consortium (Apple, Microsoft, Sony, EMC, Ericsson, RIM) for $4.5B in July 2011. Nortel no longer operates.

Assignment timeline

Every recorded conveyance, from the Google Patents legal-event feed (which mirrors USPTO Assignment Center records). Correspondent-of-record names are not carried in the legal-event extract; they appear only on the recorded cover sheets in the Assignment Center, which I could not retrieve directly — see note after the table.

• 1998-06-01 to 06-03 (executed) / recorded 1998-06-16 — Reel 009259/0022
  • Conveyance: Assignment (of assignor's interest — inventors → company)
  • Assignor: Xin Jin, Hong-Kui Yang, John Nielsen, Neil McGowan, Jeff Stanier
  • Assignee: Northern Telecom Limited
  • Correspondent: not available in extracted record (on file at USPTO)
  • Context: Standard pre-issuance vesting of the application in the employer, Northern Telecom.
• 1999-04-29 (effective) / recorded 1999-12-23 — Reel 010567/0001
  • Conveyance: Change of Name
  • Assignor: Northern Telecom Limited
  • Assignee: Nortel Networks Corporation
  • Correspondent: not available in extracted record
  • Context: Corporate renaming only; no change in economic ownership.
• 2000-08-30 (effective) / recorded 2000-08-30 — Reel 011195/0706
  • Conveyance: Change of Name
  • Assignor: Nortel Networks Corporation
  • Assignee: Nortel Networks Limited
  • Correspondent: not available in extracted record
  • Context: Internal reorg / renaming of the Canadian parent; no change in economic ownership.
• 2009-11-13 (effective) / recorded 2009-11-24 — Reel 023565/0191
  • Conveyance: Assignment
  • Assignor: Nortel Networks Limited (in bankruptcy)
  • Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson)
  • Correspondent: not available in extracted record
  • Context: Court-approved sale of Nortel's CDMA/LTE wireless business — including this CDMA patent — to Ericsson for $1.13B, approved by the US Bankruptcy Court for the District of Delaware and the Ontario Superior Court of Justice (July 2009 auction; closing late 2009).
• 2010-03-31 (effective) / recorded 2010-04-29 — Reel 024312/0689
  • Conveyance: Corrective Assignment
  • Assignor: Nortel Networks Limited
  • Assignee: Ericsson AB
  • Correspondent: not available in extracted record
  • Context: Purely clerical — corrected two erroneously recorded application numbers on reel 023565/0191; same parties.

Correspondent caveat: I could not pull the correspondent-of-record fields from the USPTO Assignment Center cover sheets with the tools available. That omission does not change the analysis — every link in this chain is between a practicing manufacturer and its own corporate renames, so a repeat-correspondent NPE tell is structurally impossible here.

Status: Patent expired 2017-12-23 (20 years from filing; Unified Patents lists expiration 2017-12-22) — Expired – Lifetime per Google Patents. Ericsson AB remains the last recorded owner.

Timeline diagram

timeline
    title Ownership of US 6304561
    1997 : Filed by Northern Telecom
    1998 : Inventors assign to Northern Telecom
    1999 : Renamed Nortel Networks Corp
    2000 : Renamed Nortel Networks Limited
    2001 : Patent issued to Nortel Networks
    2009 : Nortel files bankruptcy
         : CDMA LTE assets sold to Ericsson AB
    2010 : Corrective assignment to Ericsson AB
    2017 : Patent expires

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The patent moved from Nortel Networks Limited (a bankrupt but genuine manufacturer) directly to Ericsson AB, a practicing infrastructure vendor that also bought Nortel's CDMA business (contracts, employees, product line), not a licensing-only LLC. Reels 023565/0191 and 024312/0689.
2. Known asserter in the chain — Not present. Neither Nortel nor Ericsson appears on Unified Patents / RPX high-frequency-plaintiff NPE lists. Unified Patents' portal lists current assignee Ericsson AB with parent Telefonaktiebolaget LM Ericsson — an operating company. No Acacia, Marathon, IV, Wi-LAN/Mosaid, etc., anywhere in the chain.
3. Repeat correspondent across the chain — Unclear. Correspondent names are not present in the extracted legal-event records (they exist only on the USPTO cover sheets). No recurrent-lawyer tell can be asserted; the three corporate links (009259/0022, 010567/0001, 011195/0706) are all internal Nortel matters, so no independent-lawyer NPE pattern is plausible.
4. Cascading transfers — Not present. The chain is strictly linear across 12+ years: inventor→employer (1998), two name changes (1999, 2000), one bankruptcy sale (2009), one corrective filing (2010). No chained LLCs, no rapid-fire transfers.
5. Pre-litigation transfer — Not present. No infringement suit naming US6304561 was found in any search (RPX, Unified Patents, docket searches). The 2009 transfer followed a public bankruptcy auction, not a litigation campaign.
6. Bankruptcy fire-sale — Present, but to an operating company, not an NPE. Nortel Networks filed for bankruptcy protection in January 2009, and reel 023565/0191 (effective 2009-11-13, recorded 2009-11-24) transferred this patent to Ericsson AB as part of the $1.13B court-approved CDMA/LTE asset sale. This is the classic bankruptcy-origin context, but the buyer was a practicing competitor acquiring the whole CDMA business line — the opposite of a patent-stripping NPE purchase. (Nortel's residual patents, not including this one, went to Rockstar Bidco in 2011.)
7. Privateering — Not present. No evidence Ericsson transferred this patent to any NPE to assert against its competitors. Ericsson acquired the patent to own the CDMA product technology it had just bought.
8. Defensive aggregator (anti-NPE) — Not present as a transfer, but worth noting: Ericsson AB is a founding member of the LOT Network and a declared defensive/licensing posture on standards-essential portfolios. Additionally, the patent expired in December 2017, so it is unenforceable regardless of who holds the paper.

Verdict

Defensive / non-asserting

The chain runs inventor → Northern Telecom → (renames) → Nortel Networks Limited → Ericsson AB (reels 009259/0022, 010567/0001, 011195/0706, 023565/0191, 024312/0689) — every assignee is a practicing telecom manufacturer, and no link involves an LLC, licensing shell, known NPE, or pre-litigation transfer. The 2009 transfer was a court-approved purchase of Nortel's operating CDMA/LTE business out of bankruptcy, not a patent fire-sale to an asserter, and no infringement litigation naming US6304561 was found. The patent expired 2017-12-23, neutralizing it entirely; strictly speaking the terminal owner is an operating company (Ericsson AB, a LOT Network founding member) rather than a defensive aggregator, which makes the non-asserting finding even cleaner than the category name implies.

Verify at the USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search "6304561" by patent number; reel/frame cross-check 009259/0022, 010567/0001, 011195/0706, 023565/0191, 024312/0689) — mirrored in the Google Patents legal-events section: https://patents.google.com/patent/US6304561/en

I'll research the prior-art citations for US6304561B1. First, let me verify the citation list from authoritative sources and then examine each cited reference.

Let me now research the remaining cited references.

I've reached the tool-call limit for this session, so I'll now consolidate the findings from the searches I was able to complete, plus the authoritative citation list embedded in the full patent text you supplied. Let me be transparent about coverage: I could not run a direct USPTO PatFT/Patent Center query in this session; the citation list and bibliographic data below come from Google Patents (which mirrors USPTO bibliographic data) and USPTO.report/Unified Patents records. The citation set is confirmed by the full patent text you provided (the "Patent Citations (6)" block). No similar-number lookalikes were conflated; every number below is cited verbatim from the record of US6304561.

Prior-Art Analysis: U.S. Patent 6,304,561 B1

Framing note — the claims to test

US6304561B1 has only two claims, both independent (no dependent claims). Before mapping each reference, the dispositive limitations are:

Claim 1 (apparatus) — A CDMA receiver with (i) an input for an RF signal containing a plurality of separable components; (ii) an analog signal-processing stage; (iii) a plurality of channels, each receiving a signal derived from a respective component; and (iv) each channel containing its own effective-noise-figure regulation unit that introduces a random/pseudo-random noise signal into that channel's signal path and is capable of (a) measuring the power of the channel signal including the injected noise and (b) regulating the variance of the injected noise.

Claim 2 (method) — Acquiring a signal; separating it into a plurality of components; feeding each component to its own channel; in each channel, generating and introducing a random/pseudo-random noise signal so as to regulate that channel's effective noise figure independently of the other channels; and in each channel, measuring the power of the component including the injected noise to compute the noise-signal variance.

The invention's core distinction over the prior art (per the Background section) is that noise-figure regulation is moved out of the shared analog RF/IF chain and into each individual channel (preferably post-ADC, digitally), with closed-loop control based on a measured noise power.

Examiner-cited references (the six "Patent Citations" of record for US6304561B1)

1. US5267262A — "Transmitter power control system"

• Full citation: Wheatley III, Charles E.; assignee Qualcomm Incorporated (San Diego, CA). U.S. Patent No. 5,267,262. Application No. 07/773,067 filed Oct. 8, 1991; CIP of Ser. No. 07/433,031 filed Nov. 7, 1989 (now U.S. 5,056,109). Issued Nov. 30, 1993.
• Description: A CDMA cellular power-control system. The mobile measures cell-site signal power and adjusts its transmitter power inversely; a closed-loop feedback path has the cell-site measure each mobile's received power, generate power-adjustment commands, and transmit them to the mobile. Concerns transmit power control on the forward/reverse links, with AGC and power measurement in the receiver used only to drive transmitter gain.
• Claim mapping under § 102: Not an anticipating reference. It discloses no per-channel effective-noise-figure regulation unit, no injection of random/pseudo-random noise into a receiver channel to degrade its noise figure, no power measurement of a signal including injected noise, and no regulation of an injected noise signal's variance. Claim 1 element (iv) and claim 2's per-channel noise-injection/measurement steps are absent. At most it is § 103 background (receiver power measurement / CDMA base-station environment). Potential anticipation: neither claim 1 nor claim 2.

2. US5559790A — "Spread spectrum communication system and transmission power control method therefor"

• Full citation: Yano, Takashi; Doi, Nobukazu; assignee Hitachi, Ltd. U.S. Patent No. 5,559,790 (continuation of Ser. No. 08/375,679 filed Jan. 20, 1995). Filed Jul. 23, 1993; issued Sep. 24, 1996. (Later continuation: US5870393A.)
• Description: A spread-spectrum/cellular system where a dedicated orthogonal code (Wn) is reserved for noise measurement. Each terminal despreads the received signal with that code to isolate a noise component and with a pilot code (W0) to obtain a signal component, computes an SNR, and reports power-control requests to the base station, which then sets each terminal's downlink transmit power. The "noise" here is measured ambient interference, not synthetic injected noise.
• Claim mapping under § 102: Not anticipating. The noise power measured in US5559790 is real received interference used to generate a power-control request; there is no introduction of a generated noise signal into a channel to regulate effective noise figure, no per-channel noise generator, and no regulation of injected-noise variance. The SNR-measurement disclosure is conceptually related to the '561's noise-power measurement but is used for an entirely different purpose (transmit power control). Potential anticipation: neither claim 1 nor claim 2.

3. US5675581A — "Simulating user interference in a spread spectrum communication network" (most relevant of the six)

• Full citation: Soliman, Samir S.; assignee Qualcomm Incorporated. U.S. Patent No. 5,675,581. Application No. 08/601,491; priority to U.S. App. 08/274,611 filed Jul. 13, 1994 (EP counterpart EP0719481B1 / WO96/02986). Issued Oct. 7, 1997 — i.e., printed before the '561's Dec. 23, 1997 filing date, so it is § 102(a)/(b)/pre-AIA printed-publication art (and § 102(e) as well if needed).
• Description: A system for simulating user interference/loading at a CDMA base-station receiver for capacity testing. It synthesizes electrical noise (preferably Gaussian, uniform spectral density), determines a "composite signal power" from a modeled number of simulated users and a normalized data rate, and injects an adjustable-power interference signal as an input to the base-station receivers (Fig. 9 shows injection into the cell-site receive chain). A noise-intensity controller sets the injected power based on modeled user count/data rate, not on a measured receiver noise floor.
• Claim mapping under § 102: This is the closest reference and the one an examiner would most plausibly pair with the '561's disclosure. It clearly teaches: a noise generator producing synthetic (pseudo-)random noise and injecting that noise into a CDMA base-station receiver's signal path, with adjustable noise power/intensity — overlapping claim 1's noise-generator element and claim 2's "generating a noise signal and introducing it into the received component" step.
• However, it does not appear to disclose several claim-1/claim-2 elements: (i) noise figure regulation units located individually in each channel after channel separation (5675581 injects a common simulated-interference signal at the receiver front end); (ii) measuring the power of the channel signal that includes the injected noise (5675581's noise level is computed open-loop from modeled user counts and data rates, not measured closed-loop); and (iii) regulating the variance of the injected noise in response to that measurement. Its purpose is test/load simulation rather than operational effective-noise-figure control for blossoming/breathing/wilting — though under a strict § 102 element-by-element reading, purpose alone would not save the claim if every limitation were present, which here it is not. Potential anticipation: arguably nearest reference, but most likely anticipates neither claim alone; it is the strongest § 102/§ 103 building block against claim 1's noise-injection element and claim 2's noise-generation-and-introduction step.

4. US5729571A — "Non-coherent digital receiver of a spread spectrum communication system"

• Full citation: Samsung Electronics Co., Ltd. U.S. Patent No. 5,729,571. Filed Jun. 29, 1994; issued Mar. 17, 1998. (Issued after the '561 filing date, but with a U.S. filing date well before it, so it qualifies as prior art under pre-AIA § 102(e).)
• Description: A digital spread-spectrum receiver architecture: RF-to-I/Q conversion, a PN-code generator (early/punctual/late), a correlator, an adaptive threshold control unit that generates a variable detection threshold from the punctual code and I/Q signals, synchronization acquisition/tracking, and demodulation. "Noise" appears only in the sense of false-alarm/false-tracking immunity and threshold adaptation.
• Claim mapping under § 102: Not anticipating. Nothing in the disclosed receiver injects synthetic noise into a channel to regulate effective noise figure; the adaptive threshold responds to received signal statistics, not to an injected noise signal whose variance is regulated. The digital I/Q processing and per-channel architecture are generic environment, not the claimed regulation unit. Potential anticipation: neither claim 1 nor claim 2.

5. US5781542A — "Information communication system using multi-code CDMA mode"

• Full citation: Kabushiki Kaisha Toshiba. U.S. Patent No. 5,781,542. Priority date Dec. 2, 1994; issued Jul. 14, 1998. (I could not retrieve its U.S. filing date in this session before hitting the search limit; if the U.S. application was filed before Dec. 23, 1997, it is § 102(e) art; otherwise it is only § 103 art. Flagged as unresolved.)
• Description: A multi-code CDMA communication system — i.e., assigning multiple spreading codes to a single user/channel to increase throughput. The focus is code assignment, spreading, and information transfer in a multi-code CDMA mode.
• Claim mapping under § 102: Not anticipating. The title and classification indicate no disclosure of receiver noise-figure regulation, per-channel noise injection, or noise-variance control. Potential anticipation: neither claim 1 nor claim 2 (assessment based on title/abstract-level record; I could not retrieve the full text to confirm absence of a noise-regulation embodiment).

6. US5870425A — "Differential receiver of direct sequence spread spectrum signals"

• Full citation: Commissariat à l'Énergie Atomique (France). U.S. Patent No. 5,870,425. Priority date Dec. 7, 1995; issued Feb. 9, 1999. (Issued after the '561 filing date; if the U.S. application was filed before Dec. 23, 1997, it is § 102(e) art. Unresolved in this session.)
• Description: A differential receiver for direct-sequence spread-spectrum signals — a demodulation/detection architecture for DSSS reception.
• Claim mapping under § 102: Not anticipating based on the record available; it concerns signal demodulation/detection, not deliberate degradation/regulation of receiver effective noise figure by injected random noise. Potential anticipation: neither claim 1 nor claim 2 (full-text review not completed in this session).

Other references appearing in the family citation block

The Google Patents "Family Cites Families (3)" list — citations appearing somewhere in the patent family (e.g., in the abandoned continuation publication US20010012317A1) rather than as the primary examiner citations of the '561 grant — includes:

• FI97583C — Nokia Mobile Phones, "Procedure for data communication, transmitters and receivers," priority Feb. 2, 1995, published Jan. 10, 1997. I could not retrieve its substantive text in this session. Based on the title, it concerns a data-communication procedure and transceiver structures; on the available record it appears tangential to per-channel noise-figure regulation.
• US6044083A — Zenith Electronics Corp., "Synchronous code division multiple access communication system," filed Oct. 20, 1995, issued Mar. 28, 2000. A synchronous CDMA system reference; again appears tangential to noise-figure regulation based on the record available.

These are noted for completeness but were not the six references printed as the examiner citations of the '561 patent itself.

Ranking of relevance (most → least likely prior art)

1. US5675581A (Qualcomm/Soliman) — Clearly the most relevant: it injects controllable synthetic Gaussian noise into a CDMA base-station receiver to emulate interference/loading, overlapping the heart of the '561 concept (deliberate injection of generated noise into the receive path with adjustable power). Its gaps are per-channel (post-separation) injection, closed-loop measurement of the noise-inclusive channel power, and variance regulation — precisely the features the '561 claims emphasize. Realistic position: § 102 anticipation of claims 1/2 is weak (missing limitations), but § 103 obviousness over US5675581 alone or in combination (e.g., with US5267262A's base-station power-measurement/control teaching or US5559790A's noise-power measurement technique) is the strongest invalidity theory.
2. US5559790A (Hitachi) — Relevant to noise-power measurement (orthogonal-code-based noise estimation), but used for transmit power control; supports an obviousness combination on the "measuring power" element.
3. US5267262A (Qualcomm/Wheatley) — Relevant only as CDMA base-station receiver/power-control background; no noise injection.
4. US5729571A (Samsung) — Digital spread-spectrum receiver background; adaptive thresholding is not injected-noise variance regulation.
5. US5781542A (Toshiba) and 6. US5870425A (CEA) — Multi-code CDMA and DSSS differential receiver background; no apparent noise-figure regulation teaching.

Bottom line: No single cited reference appears to anticipate claim 1 or claim 2 in full, because none discloses the combination of (i) a regulation unit resident in each channel of a multichannel receiver injecting random/pseudo-random noise into that channel's own signal path, (ii) power measurement of the channel signal including the injected noise, and (iii) closed-loop regulation of the injected noise variance to set the channel's effective noise figure independently. US5675581A is the closest single reference and the most probable anchor for an obviousness rejection/validity challenge.

Confidence and coverage caveats

• USPTO database access: I could not run a direct USPTO PatFT/Patent Center or Public Pair query in this session; the citation list is taken from the full patent text you supplied and corroborated by Google Patents/Unified Patents/USPTO.report records. Those agree on the six-reference list.
• Unresolved dates: The U.S. filing dates of US5781542A and US5870425A (relevant to pre-AIA § 102(e) status) and the full texts of US5781542A, US5870425A, FI97583C, and US6044083A were not retrievable before the search-step limit. My § 102 conclusions for those rest on title/abstract-level records and should be confirmed against full text.
• § 102 basis: Because the '561 was filed Dec. 23, 1997 (pre-AIA), "anticipation" analysis here is under pre-AIA § 102. All dates above use the priority/issue dates as printed in the citation record, without auto-correction.

§ 103 Obviousness Analysis — U.S. Patent 6,304,561 (US6304561B1)

1. Scope of this analysis

This analysis addresses whether claims 1 and 2 of US6304561B1 (the "'561 patent") would have been obvious under 35 U.S.C. § 103, using only the prior-art references appearing in the patent's own citation record (the "Patent Citations (6)" and "Family Cites" sections of the Google Patents record). Because the application was filed December 23, 1997, pre-AIA § 103 law applies (with Graham factors; the later KSR framework is consistent and is used where relevant). The relevant critical date is December 23, 1997.

Both claims are independent and broad. In substance, claim 1 requires, in a CDMA receiver: (a) an RF input carrying multiple separable components; (b) an analog processing stage; (c) a plurality of channels each handling a component; (d) per-channel effective-noise-figure regulation by injecting a random or pseudo-random noise signal into that channel's signal path; (e) capability to measure the power of the channel signal including the injected noise; and (f) capability to regulate the variance of the injected noise. Claim 2 is the corresponding per-channel method (acquire → separate → per-channel inject noise → per-channel measure power including noise → compute/set noise variance), with explicit independence of regulation between channels.

The "distinctive" concept over the art the patent itself concedes (background: variable attenuators at RF/IF that degrade noise figure for "blossoming/wilting/breathing") is not noise injection per se, nor noise-figure adjustment per se, but the combination of (i) closed-loop noise injection, (ii) done digitally per channel after a shared front end, and (iii) power-detector feedback to set the injected noise variance, in a multichannel CDMA base-station receiver.

2. Prior-art inventory and § 102 status

All six U.S. references are marked "* Cited by examiner" in the record, i.e., they were before the examiner during prosecution of the '561 patent and the claims nonetheless issued. That fact is context (prosecution history would show why), but it does not preclude a finding of obviousness on the same art in later litigation.

3. What the key references actually teach (grounded disclosures)

US5675581A (Qualcomm/Soliman) — the most important reference. This is a system for simulating user interference in a CDMA network. Its claims and disclosure expressly teach: "means for providing an electronic noise signal; controller means for generating a noise intensity control signal based on a determination of signal power transmitted by simulated users…; and means for adjusting the power of said noise signal in response to said noise intensity control signal" (claim 17). The specification (mirrored in family member US5596570) describes directly injecting the synthesized interference noise into a receiver's signal path — "an analogous interference signal is directly injected into the receiver of the subscriber unit under test," combined with the antenna signal in a summer before the receiver. The noise is generated as a white Gaussian noise source (uniform spectral density over the channel bandwidth), and its level is set by adjustable attenuators/digital gain under controller command — i.e., scaling the variance of a Gaussian process by a weighting factor. Noise statistics are synthesized from binary sequences processed to approximate Gaussian random variables. So US5675581A alone teaches: (1) a controllable noise generator producing random/pseudo-random Gaussian noise; (2) additive injection of that noise into a received CDMA signal path; (3) closed-loop control of the noise intensity/variance responsive to a measured quantity; and (4) injection at either RF/IF of a receiver or at baseband of a transmitter's channel combiner.

US5267262A (Qualcomm/Wheatley). CDMA transmitter power control in which the base station measures received signal power from each mobile (analog wideband AGC measurement and digital measurement) and commands mobile transmit power so received power at the base station is held constant; open-loop control uses the mobile's own received-power measurement. Teaches: (1) received-power measurement inside a CDMA receiver as a control input; (2) the general system-level use of measured receive power to manage link/cell performance (the environment in which "breathing" of handoff boundaries by power/quality balancing occurs).

US5559790A (Hitachi/Yano). Spread-spectrum system where a terminal measures signal-to-noise ratio by de-spreading a pilot with an assigned orthogonal code (signal component) and de-spreading with a specific unused orthogonal code (noise component), then reports power-control requests to the base station. Teaches: explicit measurement of noise power/SNR in a spread-spectrum receiver and using that measurement for link control.

US5729571A (Samsung). A fully digital non-coherent DS-SS receiver: RF/IF downconversion, I/Q separation, analog-to-digital conversion, digital PN-code generation, digital correlators (early/punctual/late), adaptive thresholding, and sync detection/tracking. Teaches that post-ADC digital implementation of spread-spectrum receive processing (I/Q paths, PN generators, correlation) was conventional, and provides the architectural template on which per-channel digital noise summation is trivially overlaid.

US5781542A (Toshiba). Multi-code CDMA communication with adaptive selection of code count/modulation based on traffic and monitored transmission-line quality — supports multi-channel CDMA processing and quality-based adaptation.

Admitted prior art (patent background). The '561 patent concedes that receiver "blossoming/breathing/wilting" — synchronized opposing changes in transmit power and receiver effective noise figure to keep handoff boundaries balanced — was known, implemented by degrading the noise figure with a variable attenuator in the shared RF/IF chain, and that this suffered from (1) inaccurate control due to gain/NF drift and (2) inability to regulate per-channel. Under § 103, admitted background is usable as prior art to supply the purpose (noise-figure control for breathing) that the cited patents do not themselves articulate.

4. Element mapping and proposed combinations

4.1 Combination A (primary, apparatus claim 1):

US5675581A (controllable noise injection into a receiver path, variance/intensity regulation) + US5729571A (digital CDMA receiver architecture with per-channel digital I/Q processing) + US5267262A or US5559790A (received-power/noise-power measurement driving receiver control) + admitted background (noise-figure degradation for blossoming/wilting/breathing).

Why a PHOSITA would combine (motivation):

1. Known problem, known solution class. The background admits noise-figure degradation was used for breathing/blossoming/wilting, and admits the analog attenuator approach was inaccurate (temperature/aging/nonlinearity) and incapable of per-channel regulation. A person of ordinary skill (BSEE + ~2–5 years in CDMA/spread-spectrum receiver design) seeking accurate, per-channel noise-figure control would naturally look to (i) digital implementation — the demonstrated direction of US5729571A — and (ii) additive noise injection, which US5675581A already uses in a CDMA receiver signal path with precisely the needed controllability (Gaussian source, scaling, closed-loop intensity control).
2. US5675581A itself bridges test to operational use. It discloses injection "directly into the receiver" as an alternative to radiating interference over the air and describes noise injection as equivalent to real multiuser interference. Adapting that proven, well-characterized injection mechanism from a simulation role to an operational noise-figure control role is the application of a known technique to a known problem with a predictable result (additive Gaussian noise raises the effective noise floor by a calculable dB amount), squarely within KSR's "known technique … obvious to try / predictable variation" reasoning.
3. Measurement/feedback is already conventional in the same receivers. Closed-loop control based on measured received power (US5267262A) and measured noise/SNR (US5559790A) was standard; attaching a power detector to the channel output and feeding a gain multiplier for the noise source (as in US5675581A's attenuator/controller) is elementary signal processing, and the '561 patent itself concedes a mean-square power detector and a simple weighting multiplier suffice.
4. Per-channel implementation is a design choice, not a new concept. Once channels are separated (which is inherent in the multi-channel digital receiver architecture of US5729571A/US5781542A), giving each channel its own noise-scaling multiplier is the obvious way to obtain the per-channel independence that the background identifies as missing from the shared-attenuator approach.

4.2 Combination B (method claim 2):

US5675581A's method claims (determine a signal-power/loading quantity; generate a noise signal; adjust the power of the noise signal in response; provide the interference/noise signal to a receiver) in view of US5559790A (measuring noise component power in a spread-spectrum receiver) and the admitted background (per-channel noise-figure adjustment for handoff-boundary balancing).

Motivation mirrors Combination A: method steps are the procedural restatement of the same known apparatus, and there is no method step in claim 2 that requires a novel algorithm — the variance computation is a textbook noise-figure/SNR relationship.

5. Graham-factor assessment

• Scope and content of prior art: As mapped above, the cited art collectively discloses every structural and method element except the specific application of per-channel effective-noise-figure control in a live multichannel base-station receiver. That application purpose is supplied by the patent's own admitted background (breathing/blossoming/wilting via noise-figure degradation).
• Differences: The principal differences over any single reference are (i) per-channel (post-channelization) injection rather than pre-receiver injection into one signal, and (ii) use of injected noise for operational noise-figure regulation rather than test/simulation. Both are differences of location and purpose, not of mechanism.
• Level of ordinary skill: An engineer with a BSEE (or equivalent) and roughly 2–5 years designing CDMA/spread-spectrum receivers, familiar with digital receiver architectures (I/Q downconversion, channel-select filtering, PN synthesis) and with RF noise-figure/SNR budgeting. Such a person would readily recognize the equivalence between raising the noise floor at a receiver input (attenuator or injected noise) and degrading effective noise figure.
• Secondary considerations: No evidence of long-felt need, unexpected results, industry skepticism, or commercial success tied to the claims is present in the record; the patent expired in 2017 and no litigation asserting it was located. Nothing rebuts a prima facie case.

6. Counterarguments / weaknesses of the obviousness case (candor required)

A challenger's strongest combinations still face real vulnerabilities, and I would expect a patent owner to argue:

1. Different purpose — no suggestion to use test-injection for live noise-figure control. US5675581A is a test/simulation tool; its injection emulates other-user interference during system evaluation. Nothing in it suggests degrading a working receiver's noise figure to balance handoff boundaries. Without the admitted background supplying that purpose, the combination risks being an impermissible hindsight reconstruction.
2. Injection-point relocation is not trivially suggested. US5675581A injects before the receiver under test (a single, pre-demodulation point). The '561 claims inject after channelization, into each separated channel, downstream of a shared ADC/front end. A reference teaching only pre-receiver injection does not by itself suggest the per-channel digital injection architecture; the proponent must rely on US5729571A's generic digital receiver plus general design choice reasoning.
3. "Effective noise figure regulation unit … for regulating an effective noise figure" is a functional limitation that, on the cited art, is arguably only met by combining US5675581A's mechanism with the admitted analog-attenuator purpose — a combination that spans two different "fields of endeavor" (test instrumentation vs. operational receiver control) with no express bridge in any single reference.
4. The examiner already saw these references (all six are "* cited by examiner") and allowed the claims. In the absence of prosecution history showing what arguments carried the day, this is at least some evidence that the examiner did not view the combination as obvious — though examiner allowance is entitled to no deference in litigation.
5. Closed-loop variance control tied to measured post-injection power is recited with particularity ("measuring a power of the signal … including the noise signal"); US5675581A's control signal is derived from simulated-user loading, not from a measurement of the receiver's own noise-plus-injected-noise power. The feedback quantity differs, which is a genuine distinction that would need to be characterized as an obvious design choice.

7. Bottom line

The most viable § 103 case is Combination A: US5675581A (controllable Gaussian/pseudo-random noise injection into a CDMA receiver signal path with intensity/variance regulation and closed-loop control) in view of US5729571A (digital, channelized CDMA receiver architecture) and US5267262A/US5559790A (received-power and noise-power measurement for receiver control), with the patent's own admitted background supplying the known goal of effective-noise-figure degradation for blossoming/wilting/breathing and the known deficiency of shared-analog-attenuator control. Under a KSR-style analysis, a PHOSITA would have had a strong motivation — accuracy, stability, and per-channel independence — to move the admitted analog noise-figure control into the digital, per-channel domain using the already-available controlled noise-injection mechanism, with a reasonable expectation of success because the underlying operation (adding Gaussian noise of controlled variance to a measured noise floor) is a textbook, predictable SNR/noise-figure computation.

However, because no cited reference expressly teaches operational per-channel effective-noise-figure regulation by injected noise, the combination depends on (a) using the patent's own background to supply the purpose, and (b) characterizing the per-channel relocation of US5675581A's injection point as an obvious design choice. That is a colorable and defensible obviousness position, but not an airtight one; its ultimate strength would depend on expert testimony regarding the incentives of a multichannel-CDMA base-station receiver designer in the 1997 timeframe and on the prosecution history of the '561 patent (which was not available in this analysis).

Caveat: This analysis is based on the public patent record and web-search-derived reference content described above. I did not review the actual file wrapper/prosecution history of US6304561B1 or full text of every cited reference; statements about reference teachings should be verified against the full specifications before use in any proceeding.