Compact Wide Dynamic Range Transmitter For Point To Point Radio

• US 20080287076A1
• Filed: 05/17/2007
• Published: 11/20/2008
• Est. Priority Date: 05/17/2007
• Status: Active Grant

• Current Assignee: Aviat U.S., Inc. (Aviat Networks Incorporated)
• Original Assignee: Harris Stratex Networks Operating Corporation (Aviat Networks Incorporated)
• Inventors: Shen, Ying, Nguyen, Thanh H., Laudolff, James, Schafer, David C., Nichols, Todd, Mashburn, Travis
• Granted Patent: US 8,095,088 B2
• Time in Patent Office: Days
• US Class Current: 455/114.3
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/62 for providing a predistortion of the signal in the transmitter and corresponding correction in the receiver, e.g. for improving the signal/noise ratio
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion

Abstract

A radio frequency transmitter comprising a modem which receives one or more input data signals and an adaptive predistortion signal and provides a baseband in-phase signal and a baseband quadrature signal. The transmitter may comprise a power amplifier module which receives the in-phase and quadrature phase signals and provides a radio frequency output signal. A predistortion module receives the radio frequency signal, downconverts the radio frequency signal to an intermediate frequency signal, and downconverts the intermediate frequency signal to a baseband feedback signal. The transmitter samples the feedback signal and provides an adaptive predistortion signal to the modem.

Claims

1. A radio frequency transmitter comprising:

a modem which receives one or more input data signals and an adaptive predistortion signal and provides a baseband in-phase (“

I”

) signal and a baseband quadrature (“

Q”

) signal;

a power amplifier module which receives said I and Q signals and provides a radio frequency (“

RF”

) output signal; and

a predistortion module which receives said RF signal, downconverts said RF signal to an intermediate frequency (“

IF”

) signal, downconverts said IF signal to a baseband feedback signal, and samples said feedback signal to thereby provide said adaptive predistortion signal to said modem.

2. The transmitter of claim 1 further comprising a dynamic range power control module including a root-mean-squared (“

RMS”

) power detector and a variable attenuator operating on said IF signal.

3. The transmitter of claim 1 wherein said power amplifier module includes a Doherty amplifier.

4. The transmitter of claim 3 further comprising a programmable bias control module.

5. The transmitter of claim 4 wherein said programmable bias control module adjusts a bias signal to an amplifier in said power amplifier module as a function of an output power level of said power amplifier module.

6. The transmitter of claim 1 further comprising a dual loop synthesizer.

7. The transmitter of claim 1 further comprising a temperature compensation module.

8. The transmitter of claim 7 wherein said temperature compensation module includes a first temperature sensor located in proximity to an RF detector circuit, said first temperature sensor controlling a fan as a function of the temperature of said RF detector circuit.

9. The transmitter of claim 8 wherein said temperature compensation module includes a second temperature sensor located in proximity to said power amplifier module.

10. A radio frequency transmitter system comprising:

an electronics rack having an electrical backplane;

a plurality of radio frequency transmitters each operatively connected to said backplane, each transmitter comprising;

a modem which receives one or more input data signals and an adaptive predistortion signal and provides a baseband in-phase (“

I”

) signal and a baseband quadrature (“

Q”

) signal;

a power amplifier module which receives said I and Q signals and provides a radio frequency (“

RF”

) output signal;

a predistortion module which receives said RF signal, downconverts said RF signal to an intermediate frequency (“

IF”

) signal, downconverts said IF signal to a baseband feedback signal, and samples said feedback signal to thereby provide said adaptive predistortion signal to said modem;

a local reference signal generator; and

a frequency locking circuit; and

a data processing unit (“

DPU”

) operatively connected to said backplane, said DPU having a first and a second common reference signal generator,

wherein each said local reference generator is switchably connected to said first common reference signal generator via said frequency locking circuit.

11. The system of claim 10 wherein said DPU further comprises a second switch adaptable to switch from a first of said plural transmitters to a second of said plural transmitters.

12. The system of claim 11 wherein said switching occurs as a result of an error or failure in said first transmitter.

13. The system of claim 12 wherein said switching occurs as function of a quality measurement of said RF signal.

14. The system of claim 13 wherein said quality measurement is selected from the group consisting of:

signal strength, signal to noise ratio, bit error rate, and received power level.

15. The system of claim 10 wherein the number of said plural transmitters is four.

16. A method for transmitting a signal comprising the steps of:

providing a co-located modem and transmitter in an assembly;

receiving data and a pre-distortion signal in the co-located modem to provide a first signal;

converting the first signal to a baseband signal;

providing a synthesizer that generates plural reference signals for use by the modem and transmitter;

modulating the baseband signal;

amplifying the modulated signal with an amplifier;

demodulating the amplified signal with distortion circuitry to provide the pre-distortion signal; and

transmitting the amplified signal with a transmitter.

17. The method of claim 16 wherein the step of further comprises providing thermal control for optimizing bias points of the amplifier.

18. The method of claim 16 wherein the step of amplifying further comprises compensating the modulated signal for temperature changes in the amplifier.

19. The method of claim 16 wherein the step of providing an oscillator further comprises providing a common reference signal to the modem and transmitter.

20. The method of claim 16 wherein the step of providing an oscillator further comprises locking the local oscillator to a reference frequency as a function of an alarm.

21. The method of claim 16 further comprising the step of calibrating the amplified signal.

22. The method of claim 16 further comprising the step of switching to a standby transmitter to transmit the amplified signal if said transmitter fails.

23. The method of claim 16 wherein said synthesizer is a dual loop synthesizer.