High frequency power amplifier with high efficiency and low distortion

• US 5,264,807 A
• Filed: 08/13/1991
• Issued: 11/23/1993
• Est. Priority Date: 08/13/1990
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kobayashi, Kazuhiko, Maniwa, Toru, Kobayakawa, Shuji, Kurihara, Hiroshi, Asano, Yoshihiko, Okubo, Naofumi, Daido, Yoshimasa
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US07/744,435
• Time in Patent Office: 833 Days
• Field of Search: 330/10, 330/84, 330/122, 330/124 R, 330/149, 330/262, 330/264, 330/295, 330/269
• US Class Current: 330/295
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H03F 1/3223 using feed-forward H03F1/3211 takes precedence
• CPC Class Codes: H03F 3/604 using FET's

Abstract

A high frequency amplifier containing: a constant envelope signal generation circuit for transforming an input signal to form two constant envelope signals where phases of the constant envelope signals correspond to an amplitude of an envelope of the input signal; two amplifying circuits for separately amplifying two constant envelope signals; and a power synthesizing circuit for synthesizing the first and second amplified signals to generate an amplified signal of the input electric signal, and reflecting remaining components of the first and second amplified signals which remaining components remain in the above synthesizing operation, toward the first and second amplifying circuits. Further, an input impedance of the power synthesizing circuit may be controlled by shifting phases of the above reflected components by respectively predetermined amounts, or by adaptively shifting phases of the above reflected components responding to an input level, so that a total efficiency of the high frequency amplifier is maximized. The high frequency amplifier may contain, instead of the above two amplifying circuits and the power synthesizing circuit, a circuit for inverting a phase of one of the two constant envelope signals; and a single-ended push-pull amplifier circuit for receiving the other of the two constant envelope signals, and an output of the phase inversion circuit, and synthesizing the received signals to generate an amplified signal of the input electric signal.

Claims

1. A high frequency amplifier, comprising:

a constant envelope signal generation circuit for receiving an input electric signal and transforming the electric signal to form first and second constant envelope signals having constant envelope amplitudes and having phases corresponding to an amplitude of an envelope of the input electric signal;

phase shift means for shifting a phase of said first constant envelope signal by 90 degrees;

a first amplifying circuit, operatively connected to said phase shift means, for receiving and amplifying said first constant envelope signal after the phase of the first constant envelope signal has been shifted by 90 degrees, to generate a first amplified signal;

a second amplifying circuit, operatively connected to said constant envelope signal generation circuit, for receiving and amplifying said second constant envelope signal, to generate a second amplified signal; and

a 90°

hybrid circuit, having first, second, third, and fourth terminals, for receiving said first and second amplified signals from said first and second amplifying circuits, at said first and second terminals, respectively, and for synthesizing said first and second amplified signals to generate an amplified signal of said input electric signal, a propagation length of a first signal path from said second terminal to said third terminal and a propagation length of a second signal path from said second terminal to said third terminals producing a sum of said phase shift caused by said phase shift means and the first signal path from said first terminal to said third terminal equal to a phase shift caused by the second signal path from said second terminal to said third terminal, said amplified signal of said input electric signal being output from said third terminal, and said fourth terminal being made electrically open.

2. A high frequency amplifier according to claim 1, wherein each of said first and second amplifying circuits is one of a class "AB" amplifier, a class "B" amplifier, a class "C" amplifier, and a class "F" amplifier, having a current which flows therethrough varying in dependence upon an output power thereof.

3. A high frequency amplifier, comprising:

a constant envelope signal generation circuit for receiving an input electric signal and transforming the electric signal to form first and second constant envelope signals having constant envelope amplitudes and having phases corresponding to an amplitude of an envelope of the input electric signal;

phase shift means for shifting a phase of said first constant envelope signal by 180 degrees;

a first amplifying circuit, operatively connected to said phase shift means, for receiving and amplifying said first constant envelope signal after the phase of the first constant envelope signal after the phase of the first constant envelope signal has been shifted by 180 degrees, to generate a first amplified signal;

a second amplifying circuit, operatively connected to said constant signal generation circuit, for receiving and amplifying said second constant envelope signal, to generate a second amplified signal; and

a 180°

hybrid circuit, having first, second, third, and fourth terminals, for receiving said first and second amplified signals from said first and second amplifying circuits at said first and second terminals, respectively, and for synthesizing said first and second amplified signals to generate an amplified signal of said input electric signal, a propagation length of a first signal path from said second terminal to said third terminal and a propagation length of a second signal path from said first terminal to said third terminal producing a sum of said phase shift caused by said phase shift means and the first signal path from said first terminal equal to a phase shift caused by the second signal path from said second terminal to said third terminal, said amplified signal of said input electric signal being output from said third terminal, and said fourth terminal being made electrically open.

4. A high frequency amplifier according to claim 3, wherein each of said first and second amplifying circuits is one of a class "AB" amplifier, a class "B" amplifier, a class "C" amplifier, and a class "F" amplifier, having a current which flows therethrough varying in dependence upon an output power thereof.

5. A high frequency amplifier, comprising:

a constant envelope signal generation circuit for receiving an input electric signal and transforming the input electric signal to form two constant envelope signals having constant envelope amplitudes and having phases corresponding to an amplitude of an envelope of the input electric signal;

first and second amplifying circuits for respectively receiving the constant envelope signals and separately amplifying the constant envelope signal to respectively generate first and second amplified signals at output terminals thereof;

a first circulator having first, second, and third terminals, said first terminal operatively connected to the output terminal of said first amplifying circuit;

a second circulator having first, second, and third terminals, said first terminal operatively connected to the output terminal of said second amplifying circuit, in each of said first and second circulators, an input signal from said first terminal being output from said second terminal, an input signal from said second terminal being output from said third terminal, and an input signal from said third terminal being output from said first material;

power synthesizing circuit means for receiving said first and second amplified signals from said second terminals of said first and second circulators, for synthesizing the first and second amplified signals to generate a third amplified signal corresponding to said input electric signal, and reflecting remaining components of said first and second amplified signals toward said second terminal of each of said first and second circulators, a propagation length of an electric signal from the terminals of each of said first and second circulators to said output terminal of said power synthesizing circuit means being equal to (2n-1)λ

/4, where n=1, 2, . . . , and 2π

/λ

is an amplification frequency;

first phase shift means operatively connected to said third terminal of said first circulator, for receiving an electric signal output from the third terminal of said first circulator, shifting a phase of the received electric signal, and for outputting a first phase-shifted signal to the third terminal of said first circulator; and

second phase shift means, operatively connected to said third terminal of said second circulator, for receiving an electric signal output from the third terminal of said second circulator, for shifting a phase of the electric signal, and for outputting a second phase-shifted signal to the third terminal of said second circulator.

6. A high frequency amplifier according to claim 5, wherein the phase shifts in said first and second phase shift means have equal absolute values and the polarities of the phase shifts in said first and second phase shift means are opposite to one another.

7. A high frequency amplifier, comprising:

a constant envelope signal generation circuit for receiving an input electric signal and transforming the input electric signal to form two constant envelope signals having constant envelope amplitudes and having phases corresponding to an amplitude of an envelope of the input electric signal;

first and second amplifying circuits for respectively receiving the constant envelope signals and separately amplifying the constant envelope signals to respectively generate first and second amplified signals at output terminals thereof; and

power synthesizing circuit means for receiving said first and second amplified signals and for synthesizing the first and second amplified signals to generate a third amplified signal corresponding to the input electric signal, said power synthesizing circuit means comprising means for adaptively varying a real part of an input impedance of said power synthesizing circuit means in dependence upon an amplitude of an envelope of said input electric signal so that the real part of the input impedance of the power synthesizing circuit means becomes large when an output power of the power synthesizing circuit means is small, and the real part of the input impedance of the power synthesizing circuit means becomes small when an output power is large.

8. A high frequency amplifier according to claim 7, wherein said power synthesizing circuit means comprises:

input power level detecting means for detecting a power level of said input electric signal;

a first circulator having first, second, and third terminals, said first terminal operatively connected to the output terminal of said first amplifying circuit;

a second circulator having first, second, and third terminals, said first terminal operatively connected to the output terminal of said second amplifying circuit, in each of said first and second circulators, an input signal from said first terminal being output from said second terminals, an input signal from said second terminal being output from said third terminal, and an input signal from said third terminal being output from said first terminal;

a branch circuit, having an output terminal, for receiving said first and second amplified signals from said second terminals of said first and second circulators, for synthesizing the first and second amplified signals to generate a third amplified signal corresponding said input electric signal, and for reflecting remaining components of said first and second amplified signals after said synthesizing operation toward said second terminals of said first and second circulators, a propagation length of an electric signal from the terminals of each of said first and second circulators to said output terminal of said branch circuit being equal to (2n-1)λ

/4, where n=1, 2, . . . , and 2π

/λ

is an amplification frequency;

first phase shift means operatively connected to said third terminal of said first circulator, for receiving an electric signal output from the third terminal of said first circulator, for shifting a phase of the received electric signal, and for outputting a first phase-shifted signal to the third terminal of said first circulator; and

second phase shift means operatively connected to said third terminal of said second circulator, for receiving an electric signal output from the third terminal, for shifting a phase of the electric signal, and for outputting a second phase-shifted signal to the third terminal;

said branch circuit comprising means for adaptively varying a real part of an input impedance of said power synthesizing circuit in dependence upon the power level detected by said input power level detecting means to maintain the real part of the input impedance of the power synthesizing circuit means equal to zero.

9. A high frequency amplifier, comprising:

a constant envelope signal generation circuit for receiving an input electric signal and transforming the electric signal to form two constant envelope signals having constant envelope amplitudes and having phases of the constant envelope signals corresponding to an amplitude of an envelope of the input electric signal;

phase inversion means for inverting a phase of one of said two constant envelope signals; and

a single-ended push-pull amplifier circuit for receiving the other of said two constant envelope signals and an output of said phase inversion means, and synthesizing the received signals to generate an amplified signal of said input electric signal.

10. A high frequency amplifier according to claim 9, wherein said single-ended push-pull amplifier circuit comprises serially connected first and second amplifying devices, and wherein each of said first and second amplifying devices is one of a class "AB'"'"' amplifier, a class "B" amplifier, and a class "C" amplifier, wherein a current which flow therethrough varying in dependence upon an input power thereof.