本文提出一個使用z 域和無偏壓預失真技術的功率放大器之設計。透過z域技術可以找出功率放大器的初始匹配網路架構，由於放大器的反射係數不得由z域技術所控制，所以反射係數往往不如預期的好，雖然放大器仍具有濾波且平坦的增益響應，因此，放大器必須透過微波模擬工具進行額外的最佳化使得輸入端反射係數能達到-10 dB同時維持原有的濾波增益響應，這個過程會造成匹配網路中的大部分傳輸線之電氣長度不再是λ/4，這也是題目所稱的準z域技術。
一個2瓦特和10瓦特的功率放大器在本研究中已被實現，操作頻率為2.55到2.65 GHz，板材是UL2000，其介電係數為2.38，厚度是0.762 mm，兩個功率放大器的濾波增益響應與輸入端反射係數都有達到預期的效果，雖然它們都能輸出其電晶體最大功率，但是以線性度IM3(Third order imtermodulatio distortion)為-30 dBm參考標準下，可用輸出功率卻遠低於最大輸出功率，在此，預失真線性技術將被採用於改善功率放大器的IM3。
本研究將使用由一個反向並聯二極體群和一個π型衰減器所構成的預失真電路進行功率放大器的線性度之改善，另外，外加一個串聯電容並接於衰減器的串聯電阻可以減少預失真電路的植入損耗，同時也能加強對於放大器的線性度之改善效果。本預失真電路不需要額外的偏壓電路，透過調整二極體個數和衰減器的電阻以及外加的電容即可產生適當的非線性失真補償，優化所設計之功率放大器。藉由等效電路與ABCD矩陣進行電路分析，更能了解預失真電路的特性，選用板材UL2000進行電路製作，本預失真電路具有尺寸為小、低植入損失和好的反射係數等特性。功率放大器經過線性化技術的改善後，可以輸出更多的可用功率在一定的線性度標準下。

This thesis is a design of power amplifier using z-domain and predistortion technique. The use of z domain technique helps us to find out the initial configuration of the input/output matching networks of power amplifier. In order to improve the matching condition for the combination of both predistorter and power amplifier, the input return loss of power amplifier should achieve at least 10 dB for the better performance. In general, the return loss can’t be controlled by z-domain technique, so it is often not as good as the design goal. Afterward, the power amplifier is optimized with a microwave design tool especially so that the return loss attains 10 dB while its original gain response is maintained.
A 2-watt and a 10-watt power amplifier have been implemented and fabricated on a substrate UL2000 with εr=2.38 and h=0.762 mm. The operating frequency ranges are from 2.55 to 2.65 GHz. Though their output power has achieved the maximum value of the transistor, the usable power for a given level of IM3 is far less than the maximum output power. The predistortion technique is adopted to improve the linearity of power amplifiers.
A predistorter composed of anti-parallel diodes and a π-type attenuator is employed to improve the IM3 of power amplifiers. An extra capacitor is added into the predistorter to reduce the insertion loss and enhance the linearity. This predistorter doesn’t need any DC bias circuit. By varying the number of diodes, the series resistor and the value of the extra capacitor, a proper predistorter is obtained for the nonlinear distortion compensation of the power amplifiers. The analysis of predistorter is illustrated by its equivalent circuits and ABCD matrix. The circuit of predistorter is also built on UL2000. This predistorter is featured with compact size, small insertion loss and good return loss.
With the aid of predistorter, the power amplifier can provide more output power for a given IM3 level of -30 dBm with tone spacing of 5 MHz.

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