Design of High Efficiency High Power Broadband Amplifiers with Automatic Gain Control and Doherty Power Amplifier

• Main Authors: Jien-Rong Ji, 紀建榮
• Other Authors: Hong-Yeh Chang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/63345277136376315717

碩士 === 國立中央大學 === 電機工程學系 === 105 === 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.