Compact wide dynamic range transmitter for point to point radio

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.

What we claim is: 
     
         1 . A radio frequency transmitter comprising:
 a modem for receiving one or more input data signals and an adaptive predistortion signal, the modem providing provides a baseband in-phase (“I”) signal and a baseband quadrature (“Q”) signal, each of the I and Q signals being based on the input data signals and the adaptive predistortion signal;   a power amplifier module coupled to the modem, the power amplifier module for amplifying the I and Q signals into a radio frequency (“RF”) output signal; and   a predistortion module coupled to the power amplifier module and the modem, the predistortion module for receiving the RF signal, for downconverting the RF signal to an intermediate frequency (“IF”) signal, for downconverting the IF signal to a baseband feedback signal, and for sampling the feedback signal to provide the adaptive predistortion signal to the modem.   
     
     
         2 . The transmitter of  claim 1  further comprising a dynamic range power control module coupled to the predistortion module, the dynamic range power control module including a root-mean-squared (“RMS”) power detector and a variable attenuator operating on the IF signal. 
     
     
         3 . The transmitter of  claim 1  wherein the power amplifier module includes a Doherty amplifier. 
     
     
         4 . The transmitter of  claim 3  further comprising a programmable bias control module coupled to the power amplifier module, the programmable bias control module configured to provide a programmable bias control signal to the power amplifier module. 
     
     
         5 . The transmitter of  claim 4  wherein the programmable bias control module adjusts the programmable bias control signal to an amplifier in the power amplifier module, the adjusting being as a function of an output power level of the power amplifier module. 
     
     
         6 . The transmitter of  claim 1  further comprising a dual loop synthesizer for generating plural reference signals for the modem and the transmitter. 
     
     
         7 . The transmitter of  claim 1  further comprising a temperature compensation module for controlling a temperature of one or more of the modem and the power amplifier module. 
     
     
         8 . The transmitter of  claim 7  wherein the temperature compensation module includes a first temperature sensor located in proximity to an RF detector circuit, the first temperature sensor controlling a fan as a function of the temperature of the RF detector circuit. 
     
     
         9 . The transmitter of  claim 8  wherein the temperature compensation module includes a second temperature sensor located in proximity to the 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 the backplane, each transmitter comprising;
 a modem for receiving one or more input data signals and an adaptive predistortion signal, the modem providing provides a baseband in-phase (“I”) signal and a baseband quadrature (“Q”) signal, each of the I and Q signals being based on the input data signals and the adaptive predistortion signal; 
 a power amplifier module coupled to the modem, the power amplifier module for amplifying the I and Q signals into a radio frequency (“RF”) output signal; and 
 a predistortion module coupled to the power amplifier module and the modem, the predistortion module for receiving the RF signal, for downconverting the RF signal to an intermediate frequency (“IF”) signal, for downconverting the IF signal to a baseband feedback signal, and for sampling the feedback signal to provide the adaptive predistortion signal to the modem. 
 a local reference signal generator; and 
 a frequency locking circuit; and 
   a data processing unit (“DPU”) operatively connected to the backplane, the DPU having a first and a second common reference signal generator,   wherein each the local reference generator is switchably connected to the first common reference signal generator via the frequency locking circuit.   
     
     
         11 . The system of  claim 10  wherein the DPU further comprises a second switch adaptable to switch from a first of the plural transmitters to a second of the plural transmitters. 
     
     
         12 . The system of  claim 11  wherein the switching occurs as a result of an error or failure in the first transmitter. 
     
     
         13 . The system of  claim 12  wherein the switching occurs as function of a quality measurement of the RF signal. 
     
     
         14 . The system of  claim 13  wherein the 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 the plural transmitters is four. 
     
     
         16 . A method for transmitting a signal, the method comprising:
 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 amplifying the modulated signal with an amplifier comprises providing thermal control for optimizing bias points of the amplifier. 
     
     
         18 . The method of  claim 16  wherein amplifying the modulated signal with an amplifier comprises compensating the modulated signal for temperature changes in the amplifier. 
     
     
         19 . The method of  claim 16  wherein the providing an oscillator comprises providing a common reference signal to the modem and transmitter. 
     
     
         20 . The method of  claim 16  wherein, the providing an oscillator comprises locking the local oscillator to a reference frequency as a function of an alarm. 
     
     
         21 . The method of  claim 16  further comprising calibrating the amplified signal. 
     
     
         22 . The method of  claim 16  further comprising switching to a standby transmitter to transmit the amplified signal if the transmitter fails. 
     
     
         23 . The method of  claim 16  wherein the synthesizer is a dual loop synthesizer.