應用於WiMAX與WiFi傳送端並具備補償I/Q未匹配與LO饋出之直接升頻混波器

Abstract

本篇論文提出具備匹配補償之升頻混波器電路，可搭配回授電路與演算法可達到自動校正。利用向量的補償方法來使I/Q訊號達到正交，且找出引發混波器輸出端的本地振盪器訊號的主要原因，利用小電流源補償，使本地震盪器在輸出端的訊號大小達到一個最小值。所有用來匹配補償的小電流源需要三十組的控制訊號，因此我們使用序列訊號轉平行訊號的轉換器來輸入我們的控制訊號。經由模擬驗證後可達到0.67%的EVM。 此混波器電路利用台灣積體電路(TSMC)製程下線，整個架構包含I/Q混波器、本地振盪器的四相位產生器、本地震盪器的I/Q緩衝器、I/Q混波器和序列訊號轉平行訊號的轉換器。電路的下線面積為1.65X1.25 mm2，功率消耗為50.4mW。 由於序列訊號轉平行訊號的轉換器電路部分發生了箝制效應，致使控制訊號無法正確輸入且匹配補償電路無法正確工作，因此我們最後只能量測I/Q混波器未匹配補償的特性。量測結果顯示在2.4GHz~2.7GHz，I/Q混波器具有大於-11.15dB的增益、5dBm的1-dB功率增益壓縮點、大於15dB的無用邊帶抑制與最大15dB的LO饋出抑制。由於無法經由電路本身最匹配補償，經由人為手動補償後，可達到38.5dB的無用邊帶抑制。

This thesis proposes an up-conversion I/Q mixer with matching compensation eliminating I/Q imbalance and LO feedthrough. By accompanying with power detection feedback loop and algorithm, the auto-compensation can be achieved. The compensation for I/Q balance is achieved by using vectors compensation. The main factor resulting in LO feedthrough is identified and compensated by small current sources. All the small current sources used for matching compensation are controlled with thirty control signals. The thirty control signals is fed by 3-wire. From post-simulation results, the EVM with 0.67% can be achieved. The circuit in this work is realized in TSMC 0.18um CMOS technology and composed of I/Q mixer, polyphase filter, LO I/Q buffers, and 3-wire. The total area of this chip is 1.65x1.25 mm2 and the power consumption is 50.4mW. From measurement results, the 3-wire is failed due to latch-up. The control signals for matching compensation can’t be fed the circuit. So, the matching compensation can’t work successfully. The performance of the I/Q mixer without any matching compensation is measured with LO frequency form 2.4GHz to 2.7GHz. The I/Q mixer is with conversion gain of better than -11.15dBm, the 1-dB compression point of 5dBm, the unwanted sideband suppression of better than 15dB, and the maximum LO feedthrough suppression of 15dB. Since the matching compensation can’t be achieved by compensation circuit in the chip, the unwanted sideband suppression can be achieved 38.5dB after manual compensation with tuning the magnitude and phase of baseband I/Q signals.