Amplification using amplitude reconstruction of amplitude and/or angle modulated carrier

• US 6,147,553 A
• Filed: 01/15/1999
• Issued: 11/14/2000
• Est. Priority Date: 03/06/1998
• Status: Expired due to Fees

• Current Assignee: Andrew Amplifiers Inc.
• Original Assignee: Fujant, Inc. (CommScope Holding Company, Inc.)
• Inventors: Kolanek, James
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/231,734
• Time in Patent Office: 669 Days
• Field of Search: 330/10, 330/124 R, 330/149, 330/202 A, 330/251, 330/295, 332/106, 332/107, 332/108, 332/109, 455/126
• US Class Current: 330/10
• CPC Class Codes: H03F 1/0277 Selecting one or more amplifiers from a plurality of amplifiers
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• 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 1/3288 to compensate phase shift as a function of the amplitude
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H03F 2203/7215 the gated amplifier being switched on or off by a switch at the input of the amplifier
• CPC Class Codes: H03F 2203/7236 the gated amplifier being switched on or off by putting into parallel or not, by choosing between amplifiers by (a ) switch(es)
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/602 Combinations of several amplifiers
• CPC Class Codes: H03F 3/72 Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths

Abstract

The present invention provides high power linear amplification of an amplitude and/or phase modulated signal using multiple saturated (or if desired, unsaturated) amplifiers driven by an appropriate set of switched, and/or phase modulated constant amplitude signals derived from the input signal. The present invention combines three amplitude reconstruction techniques and implements the amplitude reconstruction modulator digitally.

Claims

1. An apparatus for amplifying an input signal comprising:

a signal separator to separate the input signal into an amplitude component and a phase modulated component;

a divider coupled to the signal separator to generate drive signals representing a plurality of replicas of the phase modulated component;

a plurality of parallel paths coupled to the divider to receive the drive signals, wherein at least two of the plurality of paths comprising a switch and a phase modulator and each of the plurality of paths comprises an amplifier producing an amplified signal;

a combiner coupled to sum outputs of amplifiers of the plurality of parallel paths to produce an amplified output; and

an amplitude reconstruction controller coupled to the signal separator and said at least two paths to control each switch and phase modulator contained therein, wherein the amplitude reconstruction controller induces amplitude modulation to appear at the combiner output by introducing into the plurality of paths a combination of amplifier switching and phase modulation.

2. The apparatus defined in claim 1 wherein said each switch and phase modulator are used separately or in combination depending on dynamic range to extend the dynamic range beyond that attainable by each used alone.

3. The apparatus defined in claim 1 wherein amplitude modulation of the amplified output of the combiner matches amplitude modulation of the input signal.

4. The apparatus defined in claim 1 wherein the signal separator comprises:

a limiter to generate the phase modulated component in response to the input signal; and

a detector to generate the amplitude component in response to the input signal.

5. The apparatus defined in claim 1 wherein the detector comprises an envelope detector.

6. The apparatus defined in claim 1 further comprising an calibration unit coupled to the output and the amplitude reconstruction modulator to generate at least one calibration signal in response to the output, wherein the amplitude reconstruction modulator controls said each switch and phase modulator based on said at least one calibration signal.

7. The apparatus defined in claim 6 wherein the calibration unit generates said at least one calibration signal based on a comparison between the amplified output and a delayed version of the input signal, said at least one calibration signal causing the amplitude reconstruction modulator to compensate for amplitude and phase imbalances in the plurality of paths.

8. The apparatus defined in claim 7 wherein said at least one calibration signal causes a fixed amplitude and phase correction to be applied to each of the plurality of parallel paths.

9. The apparatus defined in claim 1 further comprising an isolator coupled to the amplified output and a filter coupled to the isolator to absorb distortion products and out of band harmonics at the combiner output.

10. The apparatus defined in claim 1 further comprising a phase modulation combining module having a pair of adders to add and subtract phase modulation generated by the amplitude reconstruction controller to the phase modulation component first and second half channels respectively.

11. The apparatus defined in claim 10 further comprising a calibration module to generate phase calibration signals, and wherein the phase modulation combining module further comprises a plurality of adders to add the phase calibration signals to the outputs of the pair of adders.

12. A method of amplifying an input signal comprising:

removing amplitude modulation from the input signal;

dividing the angle modulation component into a plurality parallel paths having amplifier stages, wherein at least two of the plurality of parallel paths have a switch and a phase modulator preceding the amplifier stage of the path;

inducing amplitude modulation into the plurality of paths by performing amplifier switching and phase modulation; and

combining outputs of the amplifier stages in each path to regenerate an output signal having the amplitude and phase modulation of the input signal.

13. The method defined in claim 12 further comprising the step of amplifying signals in the plurality of paths in a constant amplitude mode.

14. The method defined in claim 12 further comprising the step of applying phase modulation before amplifiers in the plurality of paths.

15. The method defined in claim 12 further comprising the step of applying amplifier channel switching differently for amplifiers of at least two of the plurality of paths.

16. The method defined in claim 12 wherein the amplitude modulation induced to appear at the output signal matches the amplitude modulation of the input signal.

17. The method defined in claim 12 wherein the phase modulation induced to appear at the output signal matches the phase modulation of the input signal.

18. The method defined in claim 12 further comprising the step of feeding back the output to provide calibration to compensate for mismatch of the plurality of paths.

27. The amplifier defined in claim 17 further comprising a calibration module having:

means for selecting samples of both the input and output signals;

means for generating AM/AM and AM/PM response data from the samples;

means for generating fixed phase and amplitude calibration signals for each of a plurality of parallel amplifier channels based on analysis of the AM/AM and AM/PM response data;

means for imparting phase and amplitude correction into one or more of the plurality of parallel amplifier channels;

means for performing calibration to null residual phase and amplitude imbalances that exist in the plurality of parallel amplifier channels.

19. An apparatus for amplifying a signal comprising:

means for separating an input signal into an amplitude modulation component and an angle modulation component;

means for dividing the angle modulation component into a plurality parallel paths having amplifier stages, wherein at least two of the plurality of parallel paths include a switch and a phase modulator;

means for inducing amplitude modulation into the plurality of paths by performing amplifier switching and phase modulation; and

means for combining outputs of the amplifier stages in each path to create an output signal.

20. The method defined in claim 19 wherein the amplitude modulation induced to appear at the output signal matches the amplitude modulation of the input signal.

21. The method defined in claim 19 further means for feeding back the output to provide calibration to compensate for mismatch of the plurality of paths.

26. The amplifier defined in claim 19 wherein the means for absorbing approximately minimizes the out of band harmonics and distortion products.

38. The apparatus defined in claim 26 further comprising an input equalizer coupled between the digital down converter and the rectangular to polar converter.

22. An amplifier to amplify an input signal to high power levels with low distortion, said amplifier comprising:

means for separating the input signal into its envelope and phase modulated components;

means for providing replicas of the phase modulated component to each of a plurality of parallel channels;

means for imparting phase modulation in each of the plurality of parallel channels;

means for generating switch and phase modulation for amplitude reconstruction based on a function of the signal envelope, wherein the means for generating supplies signals to each of the plurality of parallel channels;

means for controlling amplitude reconstruction based on a combination switched amplifier and differential phase modulation;

a plurality of amplifier means for amplifying the phase modulated component in each or any combination of the plurality of parallel channels; and

combining means for summing the output of the plurality of amplifiers means.

23. The amplifier defined in claim 22 wherein the combining means comprises a power combiner.

24. The amplifier defined in claim 22 further comprising means for absorbing out of band harmonics and distortion products at the output of the means for combining.

25. The amplifier defined in claim 24 wherein the means for absorbing comprises an isolator and a filter.

28. The amplifier defined in claim 22 wherein the plurality of parallel amplifier channels comprise fully saturated RF amplifiers.

29. The amplifier defined in claim 28 wherein the fully saturated RF amplifiers comprise Class C amplifiers.

30. An amplifier comprising:

means for performing analog to digital conversion to sample an analog input and calibration signals centered at an intermediate frequency (IF);

means for converting sampled the signals into complex baseband signals;

means for performing rectangular to polar conversion on the complex baseband signals to generate amplitude and phase modulated components;

means for computing phase modulation for reconstituting amplitude modulation based on vector recombination of multiple amplifier outputs;

means for generating and combining amplitude and phase calibration signals with amplitude reconstruction modulation signals to generate signals to drive a plurality of amplifier channels;

means for performing polar to rectangular conversion on signals from each of the amplifier channels to reconstitute I and Q signals;

means for converting complex baseband signals on each of the signals from the amplifier channels into real signals; and

means for converting the digital signal on each of the amplifier channel signals into analog signals centered at the IF.

31. The amplifier defined in claim 30 further comprising means for decimating the complex baseband signals prior to rectangular to polar conversion.

32. The amplifier defined in claim 30 further comprising means for interpolating data corresponding to the real signals prior to conversion of the digital signals of the amplifier channels into analog signals.

33. An apparatus for amplifying an input signal comprising:

a digital signal processor comprising

a rectangular to polar converter to convert the rectangular coordinate in-phase (I) and quadrature-phase (Q) input into a polar coordinate amplitude and phase format,

a phase modulation combining module to provide phase modulation to the polar coordinate phase component, and

a plurality of polar to rectangular converters coupled to the phase modulation combining module to convert amplitude and phase components from polar coordinates into rectangular coordinates; and

a plurality of amplifier modules, each being coupled to one of the plurality of polar to rectangular converters;

a combiner coupled to sum outputs of amplifiers of the plurality of amplifier modules to produce an amplified output.

34. The apparatus defined in claim 33 wherein each of the amplifier modules comprises a digital analog converter (DAC) coupled to an output of one of the plurality of polar to rectangular converters, and an amplifier coupled to the output of the DAC.

35. The apparatus defined in claim 33 wherein each of the channel amplifier modules further comprise:

a mixer coupled to the output of the DAC to mix a signal output from the DAC with a local oscillator frequency; and

a filter coupled to the output of the mixer, wherein the output of the filter is coupled to the input of the amplifier of said each of channel amplifier modules.

36. The apparatus defined in claim 33 further comprising

a digital down converter coupled to the input signal;

a plurality of digital up converters coupled to the plurality of polar to rectangular converters to upconvert signals received from the polar to rectangular converters.

37. The apparatus defined in claim 33 further comprising a plurality of output equalizers coupled between the plurality of polar to rectangular converters and the plurality of digital up converters.