Constant-amplitude wave combination type amplifier

• US 5,287,069 A
• Filed: 10/30/1992
• Issued: 02/15/1994
• Est. Priority Date: 02/07/1990
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Daido, Yoshimasa, Kobayashi, Kazuhiko, Maniwa, Toru, Kobayakawa, Shuji, Kurihara, Hiroshi, Asano, Yoshihiko, Okubo, Naofumi
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US07/969,522
• Time in Patent Office: 473 Days
• Field of Search: 330/10, 330/84, 330/149, 330/124 R, 330/295
• US Class Current: 330/10
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H03F 1/3252 using multiple parallel paths between input and output H03F1/3258, H03F1/3282, H03F1/3294 take precedence
• CPC Class Codes: H03F 1/3294 Acting on the real and imaginary components of the input signal
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 3/602 Combinations of several amplifiers

Abstract

A constant-amplitude wave combination type amplifier includes a first amplifier outputting a first amplified output, and a second amplifier outputting a second amplified output. The constant-amplitude wave combination type amplifier also includes a first constant-amplitude wave generating circuit for combining an input wave and the second amplified output from the second amplifier and for generating a first constant-amplitude wave which is input to the first amplifier, and a second constant-amplitude wave generating circuit for combining the input wave and the first amplified output from the first amplifier and for generating a second constant-amplitude wave. Further, the constant-amplitude wave combination type amplifier includes a wave combining circuit for combining the first and second constant-amplitude waves and for generating an output wave.

Claims

1. A constant-amplitude wave combination type amplifier comprising:

a first amplifier outputting a first amplified output;

a second amplifier outputting a second amplified output;

first constant-amplitude wave generating means, coupled to said first and second amplifiers, for combining an input wave and said second amplified output from said second amplifier to generate a first constant-amplitude wave which is input to said first amplifier;

second constant-amplitude wave generating means, coupled to said first and second amplifiers, for combining said input wave and said first amplified output from said first amplifier to generate a second constant-amplitude wave; and

first wave combining means, coupled to said first and second amplifiers, for combining said first and second amplified outputs and for generating an output wave,

said first and second amplifiers being operated in a saturated area of operation.

2. A constant-amplitude wave combination type amplifier as claimed in claim 1, wherein:

said first constant-amplitude wave generating means comprises a first attenuator which attenuates said second amplified output by a predetermined attenuation level, and a first adder having a first input terminal receiving said input wave, a second input terminal receiving said second amplified output which has passed through said first attenuator, and an output terminal which outputs said first constant-amplitude wave by adding said input wave and said second amplified output which has passed through said first attenuator;

said second constant-amplitude wave generating means comprises a second attenuator which attenuates said first amplified output by a predetermined attenuation level, and a second adder having a first input terminal receiving said input wave, a second input terminal receiving said first amplified output which has passed through said second attenuator, and an output terminal which outputs said second constant-amplitude wave obtained by adding said input wave and said first amplified output which has passed through said second attenuator; and

said first wave combining means comprises an in-phase hybrid circuit having a first input terminal receiving said first amplified output, a second input terminal receiving said second amplified output, and an output terminal which outputs said output wave.

3. A constant-amplitude wave combination type amplifier as claimed in claim 1 wherein:

said first constant-amplitude generating means comprises a first attenuator which attenuates said second amplified output by a predetermined attenuation level, and an adder having a first input terminal receiving said input wave, a second input terminal receiving said second amplified output which passes through said first attenuator, and an output terminal which outputs said first constant-amplitude wave obtained by adding said input wave and said second amplified output which has passed through said first attenuator;

said second constant-amplitude generating means comprises a second attenuator which attenuates said first amplified output by a predetermined attenuation level, and a subtracter having a first input terminal receiving said input wave, a second input terminal receiving said first amplified output which has passed through said second attenuator, and an output terminal which outputs said second constant-amplitude wave obtained by subtracting said input wave from said first amplified output which has passed through said second attenuator; and

said first wave combining means comprises a 180°

-out-of-phase hybrid circuit having a first input terminal receiving said first amplified output, a second input terminal receiving said second amplified output, and an output terminal which outputs an output wave.

4. A constant-amplitude wave combination type amplifier as claimed in claim 1, further comprising:

a third amplifier amplifying said first constant-amplitude wave and generating a third amplified output;

a fourth amplifier amplifying said second constant-amplitude wave and generating a fourth amplified output; and

second wave combining means, coupled to said third and fourth amplifiers, for combining said third and fourth amplified outputs and for generating an output wave which is different from said output wave generated by said first wave combining means.

5. A constant-amplitude wave combination type amplifier as claimed in claim 1, further comprising:

a third amplifier amplifying said first amplified output and generating a third amplified output;

a fourth amplifier amplifying said second amplified output and generating a fourth amplified output; and

second wave combining means, coupled to said third and fourth amplifiers, for combining said third and fourth amplified outputs and for generating an output wave which is different from said output wave generated by said first wave combining means.

6. A constant-amplitude wave combination type amplifier comprising:

constant-amplitude wave generating means for combining an input wave and a first auxiliary input wave and for generating a first constant-amplitude wave and a second constant-amplitude wave;

a first amplifier amplifying said first constant-amplitude wave and outputting a first amplified output;

a second amplifier amplifying said second constant-amplitude wave and outputting a second amplified output;

first wave combining means, coupled to said first and second amplifiers, for combining said first and second amplified outputs and for generating an output wave and an auxiliary output wave; and

auxiliary wave feedback means, coupled to said first wave combining means and said constant-amplitude wave generating means, for feeding back, as said first auxiliary input wave, said auxiliary output wave to said constant-amplitude wave generating means,

said first and second amplifiers being operated in a saturated area of operation, and

the first and second amplified outputs being fed back in phase to said first and second amplifiers, respectively, via said first wave combining means, said auxiliary wave feed back means and said constant-amplitude wave generating means.

7. A constant-amplitude wave combination type amplifier as claimed in claim 6, further comprising:

auxiliary wave generating means for generating a second auxiliary input wave from said input wave; and

adder means, coupled to said auxiliary wave feedback means and said auxiliary wave generating means, for adding said first auxiliary input wave supplied from said auxiliary wave feedback means and said second auxiliary input wave generated by said auxiliary wave generating means and for outputting, as said first auxiliary input wave supplied to said constant-amplitude wave generating means, an addition result to said constant-amplitude wave generating means.

8. A constant-amplitude wave combination type amplifier as claimed in claim 7, wherein:

said auxiliary wave generating means comprises approximate solution circuit means for generating an approximate solution indicative of an amplitude of an orthogonal wave orthogonal to said input wave; and

said approximate solution corresponds to said second auxiliary input wave generated by said auxiliary wave generating means.

9. A constant-amplitude wave combination type amplifier as claimed in claim 8, wherein said approximate solution circuit means comprises:

a limiter amplifier which amplifies said input wave and outputs an amplitude-limited wave;

a subtracter which outputs a difference between said input wave and said amplitude-limited wave; and

said difference corresponds to said second auxiliary input wave generated by said auxiliary wave generating means.

10. A constant-amplitude wave combination type amplifier as claimed in claim 8, wherein:

said approximate solution circuit means comprises a first attenuator which has a first attenuation level and which outputs an attenuated approximate solution to said adder means;

said auxiliary wave feedback means comprises a second attenuator which has a second attenuation level and which outputs a first attenuated auxiliary output wave, a phase shifter which shifts the phase of said first attenuated auxiliary output wave by a predetermined angle, and a third attenuator which has a third attenuation level and which outputs a second attenuated auxiliary wave to said adder means; and

the sum of said first attenuation level and said third attenuation level is equal to 1.

11. A constant-amplitude wave combination type amplifier as claimed in claim 6, wherein:

said constant-amplitude wave generating means comprises a first 90°

hybrid circuit having a first input terminal receiving said input wave, a second input terminal receiving said first auxiliary input wave, a first output terminal outputting said first constant-amplitude wave to said first amplifier, and a second output terminal outputting said second constant-amplitude wave to said second amplifier;

said first wave combining means comprises a second 90°

hybrid circuit having a first input terminal receiving said first amplified output, a second input terminal receiving said second amplified output, a first output terminal outputting said auxiliary output wave to said auxiliary wave feedback means, and a second output terminal which outputs said output wave; and

said auxiliary wave feedback means comprises an attenuator which attenuates said auxiliary output wave by a predetermined attenuation level, and a phase shifter which shifts the phase of a wave from said attenuator by a predetermined angle and which outputs said first auxiliary input wave applied to said second input terminal of said first 90°

hybrid circuit.

12. A constant-amplitude wave combination type amplifier as claimed in claim 6, further comprising:

a third amplifier amplifying said first constant-amplitude wave and generating a third amplified output;

a fourth amplifier amplifying said second constant-amplitude wave and generating a fourth amplified output; and

second wave combining means, coupled to said third and fourth amplifiers, for combining said third and fourth amplified outputs and for generating an output wave which is different from said output wave generated by said first wave combining means.

13. A constant-amplitude wave combination type amplifier as claimed in claim 6, further comprising:

a third amplifier amplifying said first amplified output and generating a third amplified output;

a fourth amplifier amplifying said second amplified output and generating a fourth amplified output; and

second wave combining means, coupled to said third and fourth amplifiers, for combining said third and fourth amplified outputs and for generating an output wave which is different from said output wave generated by said first wave combining means.

14. A constant-amplitude wave combination type amplifier comprising:

constant-amplitude wave generating means for combining an input wave and an auxiliary input wave and for generating a first constant-amplitude wave and a second constant-amplitude wave;

a first amplifier amplifying said first constant-amplitude wave and outputting a first amplified output;

a second amplifier amplifying said second constant-amplitude wave and outputting a second amplified output;

first wave combining means, coupled to said first and second amplifiers, for combining said first and second amplified outputs and for generating an output wave and an auxiliary output wave; and

auxiliary wave generating means, coupled to said constant-amplitude wave generating means, for generating said auxiliary input wave from said input wave, said auxiliary wave generating means including a limiter amplifier coupled to a subtracter.

15. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising correction means for generating a correction value indicative of a distortion component contained in said output wave by comparing said input wave with said output wave and for adding said correction value to said input value so that said distortion component contained in said output wave is canceled.

16. A constant-amplitude wave combination type amplifier as claimed in claim 15, wherein said correction means comprises:

an attenuator which attenuates said output wave by a predetermined attenuation level and which outputs an attenuated output wave;

a subtracter which outputs a difference signal indicative of a difference between said attenuated output wave and a corrected input wave; and

an adder which adds said difference signal and said input wave and which outputs a corrected input wave corresponding to an addition result, said corrected input wave being supplied, as said input wave, to said constant-amplitude wave generating means, and said difference signal corresponding to said correction value.

17. A constant-amplitude wave combination type amplifier as claimed in claim 15, wherein said correction means comprises:

an attenuator which attenuates said output wave by a predetermined attenuation level and which outputs an attenuated output wave;

a subtracter which outputs a difference signal indicative of a difference between said attenuated output wave and said input wave;

a limiter amplifier which amplifies said difference signal and which outputs an amplified difference signal corresponding to said correction value; and

an adder which adds said amplified difference signal and said input wave and which outputs said input wave having said amplified difference to said constant-amplitude wave generating means.

18. A constant-amplitude wave combination amplifier as claimed in claim 14, further comprising correction means, provided between said auxiliary wave generating means and said constant-amplitude wave generating means, for generating a correction value indicative of a distortion component contained in said output wave by comparing said auxiliary output wave with said auxiliary input wave and for adding said correction value to said auxiliary input wave, so that said auxiliary input wave to which said correction value has been added is supplied to said constant-amplitude wave generating means, and said distortion component contained in said output wave is canceled.

19. A constant-amplitude wave combination type amplifier as claimed in claim 18, wherein said correction means comprises:

an attenuator which attenuates said auxiliary output wave by a predetermined attenuation level and which outputs an attenuated auxiliary output wave;

a subtracter which outputs a difference signal indicative of a difference between said attenuated auxiliary output wave and a corrected input wave;

a limiter amplifier which amplifies said difference signal and which outputs an amplitude-limited difference signal corresponding to said correction value; and

an adder which adds said auxiliary input wave and said amplitude-limited difference signal and which outputs said corrected input wave to said constant-amplitude wave generating means as said auxiliary input wave.

20. A constant-amplitude wave combination type amplifier as claimed in claim 18, wherein said correction means comprises:

an attenuator which attenuates said auxiliary output wave by a predetermined attenuation level and which outputs an attenuated auxiliary output wave;

a subtracter which outputs a difference signal indicative of a difference between said attenuated auxiliary output wave and said auxiliary input wave, said difference signal corresponding to said correction value; and

an adder which adds said difference signal and said auxiliary input wave and which outputs said input wave having said difference to said constant-amplitude wave generating means.

21. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising:

variable gain amplifier means, provided between said auxiliary wave generating means and said constant-amplitude wave generating means, for amplifying said auxiliary input wave by a gain and for outputting said auxiliary input wave having an amplified amplitude to said constant-amplitude wave generating means; and

control means for generating a correction value indicative of a distortion component contained in said output wave by comparing said output wave with said input wave and for controlling the gain of said variable gain amplifier means on the basis of said correction value so that said distortion component contained in said output wave is canceled.

22. A constant-amplitude wave combination type amplifier as claimed in claim 21, wherein said control means comprises:

an attenuator which attenuates said output wave by a predetermined attenuation level and which outputs an attenuated output wave;

a first square-law circuit which squares said attenuated output wave and which outputs a squared attenuated output wave;

a second square-law circuit which squares said input wave and which outputs a squared input wave;

a subtracter which outputs a difference signal indicative of a difference between said squared attenuated output wave and said squared input wave; and

a filter which extracts a D.C. component from said difference signal and which outputs said D.C. component to said variable gain amplifier means, and

wherein said variable gain amplifier means comprises an automatic gain control amplifier having a variable gain controlled by said D.C. component.

23. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising:

variable gain amplifier means, provided between said auxiliary wave generating means and said constant-amplitude wave generating means, for amplifying said auxiliary input wave by a gain and for outputting said auxiliary input wave having an amplified amplitude to said constant-amplitude wave generating means; and

control means for generating a correction value indicative of a distortion component contained in said output wave by comparing said second constant-amplitude wave with a predetermined reference value and for controlling the gain of said variable gain amplifier means so that said distortion component contained in said output wave is canceled.

24. A constant-amplitude wave combination type amplifier as claimed in claim 23, wherein said control means comprises:

a square-law circuit which squares said second constant-amplitude wave and which outputs a squared signal;

a subtracter which outputs a difference signal indicative of a difference between said squared signal and said predetermined reference value; and

a filter which extracts a D.C. component from said difference signal and which outputs said D.C. component to said variable gain amplifier means, and

wherein said variable gain amplifier means comprises an automatic gain control amplifier having a variable gain controlled by said D.C. component.

25. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising:

variable gain amplifier means, provided between said auxiliary wave generating means and said constant-amplitude wave generating means, for amplifying said auxiliary input wave by a gain and for outputting said auxiliary input wave having an amplified amplitude to said constant-amplitude wave generating means; and

control means for generating a correction value indicative of a distortion component contained in said output wave by comparing said auxiliary output wave with said auxiliary input wave and for controlling the gain of said variable gain amplifier means so that said distortion component contained in said output wave is canceled.

26. A constant-amplitude wave combination type amplifier as claimed in claim 25, wherein said control means comprises:

an attenuator which attenuates said output wave by a predetermined attenuation level and which outputs an attenuated output wave;

a first square-law circuit which squares said attenuated output wave and which outputs a squared attenuated output wave;

a second square-law circuit which squares said auxiliary input wave and which outputs a squared auxiliary input wave;

a subtracter which outputs a difference signal indicative of a difference between said squared attenuated output wave and said squared auxiliary input wave; and

a filter which extracts a D.C. component from said difference signal and which outputs said D.C. component to said variable gain amplifier means, and

wherein said variable gain amplifier means comprises an automatic gain control amplifier having a variable gain controlled by said D.C. component.

27. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising:

a third amplifier amplifying said first constant-amplitude wave and generating a third amplified output;

a fourth amplifier amplifying said second constant-amplitude wave and generating a fourth amplified output; and

second wave combining means, coupled to said third and fourth amplifiers, for combining said third and fourth amplified outputs and for generating an output wave which is different from said output wave generated by said first wave combining means.

28. A constant-amplitude wave combination type amplifier as claimed in claim 14, wherein the limiter amplifier amplifies said input wave and outputs an amplitude-limited wave,

wherein the subtracter outputs a difference between said input wave and said amplitude-limited wave, said difference corresponding to said auxiliary input wave generated by said auxiliary wave generating means,

wherein said constant-amplitude wave generating means comprising a 90°

hybrid circuit having a first input terminal receiving said input wave, a second input terminal receiving said auxiliary input wave, a first output terminal outputting said first constant-amplitude wave, and a second output terminal outputting said second constant-amplitude wave, and

wherein said first wave combining means comprises a -90°

hybrid circuit having a first input terminal receiving said first amplified output, a second input terminal receiving said second amplified output, a first output terminal outputting said output wave, and a second output terminal which is terminated via a resistor.

29. A constant-amplitude wave combination type amplifier as claimed in claim 14, wherein the limiter amplifier amplifies said input wave and outputs an amplitude-limited wave,

wherein the subtracter outputs a difference between said input wave and said amplitude-limited wave, said difference corresponding to said auxiliary input wave generated by said auxiliary wave generating means,

wherein said constant-amplitude wave combination type amplifier further comprises a 90°

phase shifter which shifts a phase of said auxiliary input wave by 90° and

which outputs said auxiliary input wave having a 90°

-shifted phase to said constant-amplitude wave generating means,

wherein said constant-amplitude wave generating means comprising an in-phase hybrid circuit having a first input terminal receiving said input wave, a second input terminal receiving said auxiliary input wave from said 90°

phase shifter, a first output terminal outputting said first constant-amplitude wave, and a second output terminal outputting said second constant-amplitude wave, and

wherein said first wave combining means comprises a 90°

hybrid circuit having a first input terminal receiving said first amplified output, a second input terminal receiving said second amplified output, a first output terminal outputting said output wave, and a second terminal which outputs said auxiliary output wave.

30. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising:

variable gain amplifier means, provided between said auxiliary wave generating means and said constant-amplitude wave generating means, for amplifying said auxiliary input wave by a gain and for outputting said auxiliary input wave having an amplified amplitude to said constant-amplitude wave generating means; and

control means for generating a correction value indicative of a distortion component contained in said output wave by comparing said first and second amplified outputs with a predetermined reference value and for controlling the gain of said variable gain amplifier means so that said distortion component contained in said output wave is canceled.

31. A constant-amplitude wave combination type amplifier as claimed in claim 14, further comprising:

a third amplifier amplifying said first amplified output and generating a third amplified output;

a fourth amplifier amplifying said second amplified output and generating a fourth amplified output; and

second wave combining means, coupled to said third and fourth amplifiers, for combining said third and fourth amplified outputs and for generating an output wave which is different from said output wave generated by said first wave combining means.

32. A constant-amplitude wave combination type amplifier comprising:

variable frequency generating means for generating a first constant-amplitude wave having a frequency controllable by a control signal;

first wave combining means, coupled to said variable frequency generating means, for combining an input wave and said first constant-amplitude wave and for generating a second constant-amplitude wave;

a first amplifier which amplifies said first constant-amplitude wave and which generates a first amplified output;

a second amplifier which amplifies said second constant-amplitude wave and which generates a second amplified output;

second wave combining means, coupled to said first and second amplifiers, for combining said first and second amplified outputs and for generating an output wave; and

first control means, coupled to said first combining means and said variable frequency generating means, for generating said control signal from said first and second constant-amplitude waves.

33. A constant-amplitude wave combination type amplifier as claimed in claim 32, further comprising:

variable gain amplifier means for amplifying said first constant-amplitude wave by a gain and for outputting an amplified wave to said first amplifier; and

second control means for generating a correction value indicative of a distortion component contained in said output wave by comparing said input wave with said output wave and for controlling the gain of said variable gain amplifier means on the basis of said correction value so that said distortion component contained in said output wave is canceled.

34. A constant-amplitude wave combination type amplifier as claimed in claim 32, further comprising:

variable gain amplifier means for amplifying said second constant-amplitude wave by a gain and for outputting an amplified wave to said second amplifier; and

second control means for generating a correction value indicative of a distortion component contained in said output wave by comparing said amplified wave with a predetermined constant value and for controlling the gain of said variable gain amplifier means on the basis of said correction value so that said distortion component contained in said output wave is canceled.

35. A constant-amplitude wave combination type amplifier as claimed in claim 32, wherein said first control means comprises:

operation means for calculating A² -B² where A is an amplitude of said first constant-amplitude wave and B is an amplitude of said second constant-amplitude wave and for generating an operation output indicating A² -B² ; and

a filter which extracts a D.C. component from said operation output and which outputs said D.C. component to said variable frequency generating means as said control signal, and

wherein said variable frequency generating means comprises a voltage-controlled oscillator controlled by said D.C. component.

36. A constant-amplitude wave combination type amplifier as claimed in claim 32, wherein said first control means comprises:

operation means for generating A+B and A-B from said first and second constant-amplitude waves where A is an amplitude of said first constant-amplitude wave and B is an amplitude of said second constant-amplitude wave;

multiplying means for multiplying A+B by A-B and for generating an operation output showing A² -B² ; and

a filter extracting a D.C. component from said operation output and outputting said D.C. component to said variable frequency generating means as said control signal, and

wherein said variable frequency generating means comprises a voltage-controlled oscillator controlled by said D.C. component.

37. A constant-amplitude wave combination type amplifier comprising:

variable frequency generating means for generating a first constant-amplitude wave having a frequency controllable by a control signal;

first wave combining means, coupled to said variable frequency generating means, for combining an input wave and said first constant-amplitude wave and for generating a second constant-amplitude wave;

a first amplifier which amplifies said first constant-amplitude wave and which generates a first amplified output;

a second amplifier which amplifies said second constant-amplitude wave and which generates a second amplified output;

second wave combining means, coupled to said first and second amplifiers, for combining said first and second amplified outputs and for generating an output wave; and

control means for generating said control signal from said input wave and said output wave.

38. A constant-amplitude wave combination type amplifier as claimed in claim 37, further comprising variable gain amplifier means for amplifying said first constant-amplitude wave by a gain corresponding to said control signal generated by said control means.

39. A constant-amplitude wave combination type amplifier as claimed in claim 38, wherein said control means comprises:

difference signal generating means for generating a difference signal indicative of a distortion component contained in said output wave from respectively said input wave and said output wave;

a first filter which extracts a first D.C. component from said difference signal and which outputs said first D.C. component to said variable frequency generating means as said control signal; and

a second filter which extracts a second D.C. component from said difference signal and which outputs said second D.C. component to said variable gain amplifier means as said control signal.

40. A constant-amplitude wave combination type amplifier as claimed in claim 39, wherein said variable frequency generating means comprises a voltage-controlled oscillator controlled by said first D.C. component.

41. A constant-amplitude wave combination type amplifier as claimed in claim 39, wherein said variable gain amplifier means comprises an automatic gain control amplifier controlled by said second D.C. component.

42. A constant-amplitude wave combination type amplifier as claimed in claim 37, wherein said control means comprises:

an attenuator which attenuates said output wave by a predetermined attenuation level and which outputs an attenuated output wave;

a first limiter amplifier which amplifies said attenuated output wave and which outputs an amplified attenuated output wave;

a second limiter amplifier which amplifies said input wave and which outputs an amplified input wave;

multiplying means, coupled to said first and second limiter amplifiers, for multiplying said amplified input wave by said amplified attenuated output wave and for generating a difference signal indicative of a distortion component contained in said output wave; and

a filter which extracts a D.C. component from said difference signal and which outputs said D.C. component to said variable frequency generating means as said control signal,

wherein said variable frequency generating means comprises a voltage-controlled oscillator controlled by said D.C. component.

43. A constant-amplitude wave combination type amplifier as claimed in claim 37, wherein said control means comprises:

an attenuator which attenuates said output wave by a predetermined attenuation level and which outputs an attenuated output wave;

a first square-law circuit which squares said attenuated output wave and which outputs a first squared signal;

a second square-law circuit which squares said input wave and which outputs a second squared signal;

a subtracter which outputs a difference signal indicative of a difference between said first and second squared signals; and

a filter which extracts a D.C. component from said difference signal and which outputs said D.C. component to said variable frequency generating means as said control signal, and

said variable frequency generating means comprises a voltage-controlled oscillator controlled by said D.C. component.

44. A constant-amplitude wave combination type amplifier as claimed in claim 37, further comprising variable gain amplifier means for amplifying said second constant-amplitude wave by a gain corresponding to said control signal generated by said control means.