Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
149 words
A circuit for reducing phase distortion produced by an r.f. power amplifier for an r.f. signal source, comprising a main feedback loop for reducing phase errors between the output of the power amplifier and the r.f. signal source, the main feedback loop including a phase detector for generating an error signal, dependent on the phase 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 phase of the power amplifier input, and a subsidiary feedback loop by means of which a signal derived from the error signal is used to so modulate the phase of an input of the phase detector that small dynamic variations only of the phase detector output take place about a value which corresponds to a phase detector input of zero amplitude.
Claim 2
Dependent Claim
57 words
A circuit as claimed in claim 1, including a steering network in the error signal path, for steering a.c. components within a given amplitude along the main feedback loop for modulating the phase of the power amplifier input and d.c. components along the subsidiary feedback loop for modulating the phase of the input of the phase 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
23 words
A circuit as claimed in claim 2 or claim 3, in which the steering network includes a pair of diodes arranged in opposition.
Claim 5
Dependent Claim
30 words
A circuit as claimed in any one of claims 1 to 4, which includes means for varying the amount of error signal to be fed along the main feedback loop.
Claim 6
Dependent Claim
44 words
A circuit as claimed in any one of claims 1 to 5, including a phase shifting circuit operative in response to a signal derived from the error signal reaching a value corresponding to an end of the range of a phase modulator it controls.
Claim 7
Dependent Claim
43 words
A circuit as claimed in claim 6, including a comparator with upper and lower threshold values, the phase shifting circuit being so controlled that it varies the phase shift in response to a signal derived from the error signal crossing a threshold value.
Claim 8
Dependent Claim
37 words
A circuit as claimed in claim 6 or claim 7 in which the phase shifting circuit is capable of producing a phase shift of any angle between 0° and 360°, without a discontinuity between 360° and 0°.
Claim 9
Dependent Claim
22 words
A circuit as claimed in any one of claims 6 to 8, including a digital circuit for controlling the phase shifting circuit.
Claim 10
Dependent Claim
29 words
A circuit as claimed in any one of claims 6 to 9, in which the phase shifting circuit is in the path of the input of the power amplifier.
Claim 11
Dependent Claim
61 words
A circuit as claimed in any one of claims 6 to 10, in which the phase shifting circuit comprises a broadband phase shifter for producing outputs with quadrature phase shift relative to each other, and means for multiplying each output with respective cyclic functions, which are also in quadrature, and for combining the multiplied signals to produce a given phase shift.
Claim 12
Dependent Claim
24 words
A circuit as claimed in any one of claims 1 to 11, in which the power amplifier is suitable for use in a transmitter.
Claim 13
Dependent Claim
20 words
A circuit as claimed in claim 12, in which the power amplifier is suitable for use in an SSB transmitter.
Claim 14
Dependent Claim
18 words
An r.f. transmitter including a circuit for reducing distortion as claimed in any of claims 1 to 14.