Patent US3465852A successfully refreshed from Google Patents.
EP0441580A2
Expired / Lapsed
EP
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Circuit for reducing distortion produced by an r.f. power amplifier
Assignee: BAE Systems Electronics Ltd
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Filing: 1991-02-04
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Granted: —
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Expires: 2011-02-04
Abstract
Abstract A high frequency SSB radio transmitter has an envelope amplitude modulator 3 for varying the envelope of an r.f. signal source based on an error signal from envelope detectors 5, 6 detecting the envelope of the input and output waveform. It also has a phase modulator 4 for varying the phase of the input waveform based on differences detected in phase detector 10 between the instantaneous phase of the input and output r.f. signal. A signal derived from the error signal controls an amplitude modulator 10 in a subsidiary feedback loop to maintain the size of the envelopes detected by detectors 5 and 6 the same, in order that difference amplifier 7 may operate effectively. Rapid discrepancies between the detected envelopes 5 and 6 occurring within an envelope can then be corrected by amplitude modulator 3. <IMAGE>
Inventors
- 👤 Melvyn Mcgann
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 18:23
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3036; H03G3/3042; H03C; H03C1/00; H03C1/02; H03C1/06; H03F; H03F1/00; H03F1/32; H03F1/3241; H03F1/3247; H03F1/3282; H03F1/3288; H03F1/34; H03F3/00; H03F3/20; H03F3/24; H03F2200/00; H03F2200/102; H04; H04B; H04B1/00; H04B1/02; H04B1/04; H04B2001/0408; H04B2001/0433
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
143 words
A circuit for reducing envelope amplitude distortion produced by an r.f. power amplifier for an r.f. signal source, comprising a main feedback loop for reducing envelope amplitude errors between the output of the power amplifier and the r.f. signal source, the main feedback loop including envelope detector means for generating an error signal, dependent on the envelope amplitude of a signal derived from the power amplifier output relative to that of a signal derived from the r.f. signal source, a signal derived from the error signal being used to modulate the envelope amplitude of the power amplifier input, and a subsidiary feedback loop by means of which a signal derived from the error signal is used to modulate the envelope amplitude of an input to the envelope detector so as to tend to hold the inputs to the envelope detector means the same.
Claim 2
Dependent Claim
64 words
A circuit as claimed in claim 1, including a steering network to which the error signal is fed, for steering a.c. components within a given amplitude along the main feedback loop for modulation of the envelope amplitude of the power amplifier input and for steering d.c. components along the subsidiary feedback loop for modulating the envelope amplitude of the input to the envelope detector.
Claim 3
Dependent Claim
28 words
A circuit as claimed in claim 2, in which the steering network is such that a.c. components above the said given amplitude pass along the subsidiary feedback loop.
Claim 4
Dependent Claim
22 words
A circuit as claimed in claim 2 or claim 3, in which the steering network includes a pair of diodes in opposition.
Claim 5
Dependent Claim
36 words
A circuit as claimed in any one of claims 1 - 4, including means for varying the amount of signal derived from the error signal that is used to be fed along the main feedback loop.
Claim 6
Dependent Claim
33 words
A circuit as claimed in any one of claims 1 - 5, including a clamping circuit for clamping the signal which is used to modulate the envelope amplitude of the power amplifier input.
Claim 7
Dependent Claim
34 words
A circuit as claimed in claim 6, in which the clamping circuit is arranged to clamp the signal at a fixed voltage at the times corresponding to the peaks of the r.f. signal source.
Claim 8
Dependent Claim
41 words
A circuit as claimed in any one of claims 1 to 7, in which the envelope detector means comprises a pair of detectors comprising diodes switched by a signal of constant amplitude of carrier frequency derived from the r.f. signal source.
Claim 9
Dependent Claim
24 words
A circuit as claimed in any one of claims 1 to 8, in which the power amplifier is suitable for use in a transmitter.
Claim 10
Dependent Claim
20 words
A circuit as claimed in claim 9, in which the power amplifier is suitable for use in an SSB transmitter.
Claim 11
Dependent Claim
21 words
An r.f. transmitter including a circuit for reducing envelope amplitude distortion as claimed in any one of claims 1 - 10.
References Cited (Backward Citations)
No citation records indexed.
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