Method and device for measuring the distortion of a high-frequency power amplifier and method and means for automatically equalizing a high-frequency power amplifier

• US 6,239,657 B1
• Filed: 10/06/1999
• Issued: 05/29/2001
• Est. Priority Date: 03/27/1998
• Status: Expired due to Term

• Current Assignee: Rohde & Schwarz GmbH & Company KG
• Original Assignee: Rohde & Schwarz GmbH & Company KG
• Inventors: Bauer, Helmut
• Primary Examiner(s): Lee, Benny
• Assistant Examiner(s): NGUYEN, KHANH V
• Application Number:
  US09/413,308
• Time in Patent Office: 601 Days
• Field of Search: 330/149, 375/297, 455/126
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3276 using the nonlinearity inherent to components, e.g. a diode
• CPC Class Codes: H03F 1/3282 Acting on the phase and the amplitude of the input signal

Abstract

An equalizer for automatically equalizing a high-frequency power amplifier having a reference carrier generator which generates a reference carrier from a measured input signal of the high-frequency power amplifier, and a first synchronous demodulator while generating an input envelope curve from the measured input signal and from the reference carrier. A second synchronous demodulator which generates an in-phase component of an output envelope curve from the measured output signal of the high-frequency power amplifier and from the reference carrier, as well as a phase shifter which shifts the phase of the reference carrier 90° are also provided. A third synchronous demodulator generates a quadrature component of the output envelope curve from the measured output signal of the high-frequency power amplifier and from the reference carrier that has been shifted 90° in phase. A controller generates an amplitude correction control signal and/or a phase correction control signal from the input envelope curve, the in-phase component of the output envelope curve and/or the quadrature component of the output envelope curve. The control characteristic and/or phase characteristic of a predistorter is adjusted inversely to the control characteristic and/or phase characteristic of the high-frequency power amplifier by the amplitude correction factor and the phase correction factor.

Claims

1. A method of measuring the distortion of a high-frequency power amplifier comprising the following steps:

a) measuring an input signal and an appertaining output signal of the high-frequency power amplifier;

b) separating the input signal of the high-frequency power amplifier into an input envelope curve and a reference carrier;

c) generating an output envelope curve of the output signal of the high-frequency amplifier with the aid of the reference carrier that is generated from the input signal; and

d) displaying a control characteristic of the high-frequency power amplifier in the form of the amplitude or the power of the output envelope curve as a function of the amplitude or power of the input envelope curve.

2. The method according to claim 1, wherein in that the step of generating the output envelope curve includes synchronously demodulating the output signal.

3. The method according to claim 1, wherein in that the step of separating the input signal into the input envelope curve includes synchronously demodulating the input signal.

4. The method according to claim 1, wherein in that both an in-phase component and a quadrature component are generated by the output envelope curve in that the reference carrier is shifted 90°

in phase for the generation of the quadrature component, and that the phase angle of the output envelope curve is obtained from the in-phase component and the quadrature component, and is displayed.

5. The method according to claim 4, wherein in that a phase characteristic is displayed in the form of the phase angle of the output signal as a function of the amplitude or power of the input envelope curve, or as a function of the amplitude or power of the output envelope curve.

6. The method according to claim 4, wherein in that the generation of the in-phase component and of the quadrature component occurs by separate synchronous demodulation.

7. The method according to claim 5, wherein in that the generation of the in-phase component and of the quadrature component occurs by separate synchronous demodulation.

8. The method according to claim 1, wherein in that prior to the generation of the output envelope curve, the reference carrier is shifted by a phase angle which corresponds to the signal transit-time delay caused by the high-frequency power amplifier.

9. A method for automatically equalizing a high-frequency power amplifier comprising the following steps:

a) measuring a balancing input signal and an appertaining balancing output signal of the high-frequency power amplifier in a balancing mode;

b) dividing the balancing input signal into an input envelope curve and a reference carrier,

c) generating an output envelope curve from the balancing output signal of the high-frequency power amplifier with the aid of the reference carrier that is generated from the balancing input signal;

d) generating an amplitude correction factor as a function of the amplitude of the input signal and dependent on the ratio of the amplitudes of the output envelope signal and the input envelope signal of the balancing signal that is measured in the balancing mode; and

e) performing an automatic amplitude predistortion by connecting the amplitude of the input signal of the high-frequency power amplifier by the amplitude correction factor.

10. The method according to claim 9, wherein in that both an in-phase component and a quadrature component are generated by the output envelope curve in that the reference carrier is shifted 90°

in phase for the generation of the quadrature component, and that the phase angle of the output envelope curve is obtained from the in-phase component and the quadrature component, generating a phase correction factor as a function of the amplitude of the input signal dependent on the phase angle of the output envelope curve of the balancing signal that is measured in the balancing mode, and performing an automatic phase predistortion by correcting the phase of the input signal of the high-frequency power amplifier by the phase correction factor.

11. The method according to claim 10, wherein the in-phase component and of the quadrature component occurs by separate synchronous demodulation.

12. The method according to claim 9, wherein the amplitude correction factor, and the phase correction factor, as warranted, are fed to a predistorting means, whose control characteristic and phase characteristic are automatically set inversely to the control characteristic and to the phase characteristic of the high-frequency power amplifier by the amplitude correction factor and by the phase correction factor.

13. The method according to claim 9, wherein the input envelope curve, the output envelope curve, or respectively, the in-phase component and the quadrature component of the output envelope curve are digitized, and the amplitude correction factor and, as warranted, the phase correction factor are calculated in a control computer.

14. The method according to claim 9, wherein the balancing signal is an amplitude-modulated single-carrier signal.

15. The method according to claim 9, wherein the balancing signal is a multi-carrier signal, all the carriers of the multi-carrier signal being in the same phase state.

16. The method according to claim 9, wherein the high-frequency power amplifier is a modular construction of several subamplifiers which function in parallel fashion, and that the measuring of the balancing input signal and of the appertaining balancing output signal in the balancing mode occurs using only one of the subamplifiers, the amplitude correction factor, as warranted, the phase correction factor, that are generated for this subamplifier being accepted for the other subamplifiers.

17. An apparatus which measures the distortion of a high-frequency power amplifier, comprising:

a) a reference carrier generator which generates a reference carrier from a measured input signal of the high-frequency power amplifier;

b) a first synchronous demodulator which generates an input envelope curve from the measured input signal and the reference carrier;

c) a second synchronous demodulator which generates an in-phase component of an output envelope curve from the measured output signal of the high-frequency power amplifier and from the reference carrier;

d) a phase shifter which shifts the phase of the reference carrier 90°

;

e) a third synchronous demodulator which generates a quadrature component of the output envelope curve from the measured output signal of the high-frequency power amplifier and from the reference carrier, which has been shifted 90°

in phase;

f) a first display which displays a control characteristic of the high-frequency power amplifier in the form of the amplitude or power of the output envelope curve as a function of the amplitude or power of the input envelope curve; and

g) a second display which displays a phase characteristic of the high-frequency power amplifier in the form of the phase angle of the output signal, which is defined by the ratio of the quadrature component to the in-phase component, as a function of the amplitude or power of the input envelope curve or as a function of the amplitude or power of the output envelope curve.

18. An equalization apparatus which automatically equalizes a high-frequency power amplifier, comprising:

a) a reference carrier generator which generates a reference carrier from a measured balancing input signal of the high-frequency power amplifier;

b) a first synchronous demodulator which generates an input envelope curve from the measured balancing input signal and from the reference carrier;

c) a second synchronous demodulator which generates an in-phase component of an output envelope curve from a measured balancing output signal of the high-frequency power amplifier and from the reference carrier;

d) a phase shifter which shifts the phase of the reference carrier 90°

;

e) a third synchronous demodulator which generates a quadrature component of the output envelope curve from the measured output signal of the high-frequency power amplifier and from the reference carrier, which has been shifted 90°

in phase;

f) a controller which generates an amplitude correction control signal and/or a phase correction control signal from the input envelope curve, the in-phase component of the output envelope curve and/or the quadrature component of the output envelope curve; and

g) a signal predistorter means, whose control characteristic and phase characteristic are adjusted in the balancing mode inversely to the control characteristic and/or the phase characteristic of the high-frequency power amplifier, by the amplitude correction factor and/or by the phase correction factor, respectively;

wherein,

the control characteristic is defined by the amplitude or power of the output envelope curve as a function of the amplitude or power of the input envelope curve, and

the phase characteristic is defined by the phase angle of the output signal as a function of the amplitude or power of the input envelope curve or as a function of the amplitude or power of the output envelope curve.