在通訊系統發射端中，功率放大器是相當重要的元件，其效率高低、頻寬及能否提供穩定輸出都是在發射端的重要主題。本論文針對功率放大器效率及回退功率的效率提升，加上考量現實發射端必須提供一個穩定輸出功率，應用了自動增益控制迴路於功率放大器之研製。 第二章為使用電抗補償之甚高頻 (VHF) E類功率放大器設計與實作，並使用Freescale公司製造之橫向擴散金氧半場效應電晶體 (LDMOS) 實作10 W及100 W寬頻功率放大器，飽和功率分別可達12 W及130 W，3 dB比例頻寬分別為45–175 MHz (123%) 與75–135 MHz (60%)，頻寬內最高效率分別在130 MHz可達到63% 及110 MHz達到76%，而頻寬內最高功率增益分別在105 MHz可達20.8 dB與100 MHz 達20.4 dB，當改變10 W功率放大器汲極直流電壓從20–50 V時，其增益控制範圍為16.6–21.4 dB (4.8 dB)。 第三章則延續第二章，將自動增益控制迴路應用於第二章所設計之功率放大器，以降低輸出功率受到輸入功率、頻率及溫度變動的影響，第三章中所設計的兩個迴路分別可以穩定輸出超過10 W與100 W，其輸入動態範圍分別在105 MHz為4.5 dB與120 MHz 為4.4 dB，而頻寬分別為90–130 MHz及100–130 MHz。 第四章則是介紹了 Doherty 功率放大器之設計，並使用橫向擴散金氧半場效應電晶體 (LDMOS) 實現了一個10 W 甚高頻(VHF) Doherty 功率放大器，在180 MHz 所量測之最高效率可達69%，6–dB回退功率之效率可達到41%，3 dB比例頻寬則可達50% (130–220 MHz)，頻寬內最高功率增益可達21.6 dB (180 MHz)，在180 MHz 增益1 dB 壓縮點輸出功率可達30.8 dBm，三階交調截取點 (Third-order Intercept Point) 輸出功率可達46.6 dBm。同時第四章也使用了0.15-μm 假晶式高速電子遷移率電晶體 (PHEMT) 積體電路製程實現一個於 K 頻段之 Doherty 功率放大器，最高小訊號增益達7 dB於26 GHz，量測到最高功率為114.8 mW，在25.8 GHz最高效率為16%。由於在 K 頻段之 Doherty 功率放大器進行電磁模擬時有地方考慮未周全，因此量測與模擬有落差，其原因亦在第四章中說明。 最後於第五章總結本篇論文所提出之電路與未來研究方向。 ;The power amplifier is a critical building block in the RF transmitter. The efficiency、bandwidth and the ability of providing the stable output are essential issues for the power amplifiers. This thesis focuses on the efficiency and back-off power efficiency enhancement and the power amplifiers with automatic gain control loop to provide a stable output. The reactance compensation method is applied to the VHF class-E power amp lifers in chapter 2, and two 10 W and a 100 W broadband power amplifiers were implemented using Freescale laterally diffused metal oxide semiconductor (LDMOS) transistors. The 3 dB fractional bandwidth of 10 W and 100 W power amplifiers reaches 45–175 MHz (123%) and 75–135 MHz (60%) respectively, and the highest efficiency of 10 W and 100 W class-E power amplifiers in the 3 dB fractional bandwidth is 63% at 130 MHz and 76% at 110 MHz respectively, and the highest power gain in the 3 dB fractional bandwidth is 20.8 dB at 105 MHz and 20.4 dB at 100 MHz Gain control range of 10 W class E power amplifier is from 16.6 to 21.4 dB when DC drain voltage varying from 20–50 V. In chapter 3, the automatic gain control loop is applied to the power amplifiers implemented in chapter 2. The automatic gain control loop can alleviate the effect of input power variation on the output power. The output power of the loops are over 10 W and 100 W respectively, and the input dynamic ranges are 4.5 dB at 105 MHz and 4.4 dB at 120 MHz respectively. In chapter 4, the design of Doherty power amplifier is introduced, and a 10 W VHF Doherty power amplifier is implemented by using laterally diffused metal oxide semiconductor (LDMOS). The highest efficiency of the power amplifier measured at 180 MHz reaches 69%, and the efficiency at 6–dB back-off power is 41%, and the 3 dB fractional bandwidth is 50% (130–220 MHz), and the highest power gain in the 3 dB fractional bandwidth is 21.6 dB at 180 MHz, and the output power at 1 dB gain compression point is 30.8 dBm (at 180 MHz), and the output power at third-order intercept point is 46.6 dBm. A K-band Doherty power amplifier is also implemented by PHEMT technology in chapter 4, and the highest small signal gain reaches 7 dB at 26 GHz, but the negligence during the EM simulation results in the difference between simulation and measurement results, and the difference will be discussed in chapter 4. Lastly, the future work and the conclusions are made in chapter 5.
