Ku Band Adaptive Analog Predistorter Design

In this thesis, we design an adaptive analog predistortion system for Ku-bandpower amplifier according to the Ku band transmitter power amplifier linearityrequirements. The designs of the analog predistorter module include simulation, circuitdesign and implementation to realize power amplifier linearization.First, we study the design scheme of the Ku band adaptive analog predistorter;Which includes the Ku band open-loop analog predistorter, three order intermodulationgenerator design and down-conversion detecting circuit. After design, we designappropriate adaptive algorithm according to the characteristics of the predistortion.Then we design the circuit and implement it with the ADS co-simulation tool toauxiliary with PCB and cavity design. The open-loop predistorter and down-conversiondetector circuit has being tests to obtain the improvement of nonlinear when thepredistorter used for power amplifier. Finally, we design the control program whichincludes an adaptive algorithm to realize the control of predistortion system accordingto the circuit debugging result. The system improves the nonlinear characteristic ofpower amplifier adaptively when we test the power amplifier predistortion results.After test, the open-loop predistorter improve6dB for amplifier IM3whichP1dB=23.7dB and input two-tone signal center frequency is14GHz. When input signalfrequency increase, the amplifier IM3improvement decrease. The predistorter improve3dB for another P1dB=41.2dB amplifier IM3. By adjusting the gate voltage of amplifier,the amplifier nonlinearity has a6dB improve. Also, the distortion signal detectioncircuit can realize the down-conversion of the amplifier output signal and the outputvoltage varies linearly with the input signal power. The adaptive algorithm programcontrol predistorter to improve the nonlinearity of P1dB=23.7dB amplifier which canrealize an improvement varies of14~14.5GHz. The optimal improvement result afterback-off2dB can reach11dB and the system is more stable than open-loop systemwhen improve the power amplifier nonlinearity.