應用於WLAN 802.11a系統之微波功率放大器設計與製作

Design and Implementation of Microwave Power Amplifiers for WLAN 802.11a System Applications

李菘茂(Sung-Mao Li)

指導教授 ： 黃建彰

元智大學/工程學院/通訊工程學系/碩士(2005年)

摘要

本論文使用分立式砷化鎵pHEMT 及GCTC InGaP/GaAs HBT 製程設計應用於IEEE 802.11a 無線區域網路之線性化微波功率放大器。由於OFDM 調變訊號之峰值對平均功率比(PAPR)過大，會使得功率放大器操作在非線性區，進而造成訊號失真，為了能符合系統規範只能將功率放大器之輸出功率後退(Back Off)和犧牲功率附加效益以獲取較高之線性度。因此本論提出新的設計方法，即使用OFDM 訊號配合Load-Pull量測系統對電晶體在大訊號下之射頻特性做特徵描述，且藉由既有的測試儀器配合自行撰寫的軟體、TRL 校正件和手動可調式阻抗調節器發展一套簡易式的Load-Pull 量測系統，並使用此量測到的特性資料來設計一線性功率放大器模組。量測結果顯示輸出端和輸入端的匹配電路設計均會影響功率放大器之線性度，量測結果：線性增益為10.1 dB，輸出1dB壓縮點為31.3 dBm，功率附加效率為39.2 %；最大輸出功率為32.5 dBm，最大PAE為51.7 %。單晶微波功率放大器線性化之方式是使用二極體線性器改善電路的線性度。適應式單晶微波線性功率放大器之量測結果：線性增益為14.4 dB，輸出1dB壓縮點為24.4 dBm，功率附加效率為24.3 %；最大輸出功率為27.5 dBm，最大功率附加效率為32.4 %，輸出之三階截取點為34 dBm。

關鍵字

功率放大器 ； 無線區域網路 ； 線性化

並列摘要

In this thesis, the linear power amplifiers (PA’s) used for wireless LAN 802.11a standard are designed and implemented by using the discrete GaAs pseudomorphic high electron mobility transistors (pHEMT’s) and InGaP/GaAs heterojunction bipolar transistors (HBT’s) supported by Global Communication Tech. Corp. (GCTC). Due to the high peak-to-average-power-ratio(PAPR) nature of the orthogonal-frequency-division-multiplexing (OFDM) signals, the PA’s operate in nonlinear regions resulting the signal distortion. For conforming to the IEEE 802.11a system specification, we can only back off the output power of PA and sacrifice the PA efficiency to acquire higher linearity. For this reason, a novel approach to characterize the power transistor is proposed by means of source/load-pull measurements with the OFDM signal stimulus. We also setup a simple load-pull measurement system by using the testing instruments, TRL calibration technique, manual tuner and Matlab programs. Then, the characterized data is utilized to design a linear PA module. The measurement results show that both of output and input matching circuit designs would determine the linearity of PA. The measurement results of PA : linear power gain is 10.1 dB, output power at 1dB compression point is 31.3 dBm, power added efficiency is 39.2 %; maximum output power is 32.5 dBm, maximum power added efficiency is 51.7 %. The monolithic microwave integrated circuit (MMIC) PA’s are designed by means of diode linearizer to improve the linearity. The measurement results of MMIC adaptively linear PA : linear power gain is 14.4 dB, output power at 1dB compression point is 24.4 dBm, power added efficiency is 24.3 %; maximum power is 27.5 dBm, maximum power added efficiency is 32.4 %, OIP3 is 34 dBm.

並列關鍵字

Power Amplifier ； WLAN ； Linearizer

參考文獻

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