應用於 5G 毫米波通訊系統採用差動有預失真線性器和自動適性偏壓技術及轉導補償技術以優化線性度及效率之CMOS功率放大器

Abstract

本篇論文提出了兩個於 Ka 頻段使用台積電 90-nm 互補式金氧半導體製程 之功率放大器，旨在提升電路的線性度、輸出功率、功率附加效率及退縮 6-dB 處的功率附加效率。 於第一個電路中，我們採用了差動預失真寄生二極體線性器，功率放大器使 用 1.2 V 偏壓供電，級間加入差動預失真寄生二極體線性器以提高電路整體線性 度。由於佈局失誤，於量測時使用第二個電路之相同模態驗證差動預失真寄生二 極體線性器之效能。此三級差動共源極功率放大器在 1.2 V 以及線性器控制電壓 1 V 開啟情況下，實際量測可得 Ka 頻段操作小訊號增益 21 dB、OP1dB 為 16.3 dBm 以及飽和輸出功率 17.5 dBm，於 OP1dB 點的 PAE 與 PAE 的最大值分別為 20.2 %與 23.9 %，而在 P1dB 退縮 6 dB 點的 PAE 為 8 %。 於第二個電路中，我們採用了偏壓自動適性技術並使用 1.2 V 電壓供電。加 入偏壓自動適性電路後，功率放大器在小訊操作時將偏壓在近 B 類操作提升效 率，而大訊號操作時自動偏壓至近 A 類操作以提供較大的線性度與輸出擺幅。 使用此技術可改善 P1dB退縮 6-dB 點的 PAE。由於使用之墊片含有內阻使得內部 偏壓自動適性電路無法正常提供偏壓，隨後切除該部分電路後改採用自製外部 偏壓自動適性電路實現理想轉移曲線以進行量測。在 1.2 V 電源供電下，實際量 測可得 Ka 頻段操作小訊號增益 21.3 dB、OP1dB 為 16.6 dBm 以及飽和輸出功率 17.7 dBm，於 OP1dB 點的 PAE 與 PAE 的最大值分別為 21.4 %與 23.5 %，而在 P1dB 退縮 6-dB 點的 PAE 為 12 %。於 back-off 6-dB 點時，量測有無加入偏壓適 性技術在直流功耗的節省上可達到節省 50 %的直流功耗，可驗證偏壓自動適性 技術在 Ka 頻段仍可對直流功耗作出改善以提升 P1dB 退縮 6-dB 點之 PAE 約 1.5 %。另外也加入轉導補償技術後電路的 OP1dB提升了 0.3 dBm 且在該點的 PAE 增 加 1.5 %。使得電路在 OP1dB 及其退縮點處的 PAE 皆有改善。

In this thesis, two Ka-band power amplifiers in TSMC 90-nm CMOS process are proposed to improve the linearity, output power, PAE and back-off 6-dB efficiency. First, a Ka-band power amplifier using 1.2 V supply voltage with a differential complementary pre-distortion parasitic diode linearizer is designed and measured. Due to the layout error we use the second chip to verify the performance of the linearizer. With linearizer turned on, the measured small signal gain is 21 dB, OP1dB is 16.3 dBm, and saturation power is 17.5 dBm. The PAE is 20.2 % at OP1dB, and 8 % at 6-dB backoff from P1dB. Second, a Ka-band power amplifier using 1.2 V supply voltage with adaptive-bias technique is designed and measured. With adaptive-bias circuit, power amplifier can be biasd at near class-B for small signal operation to provide better efficiency and at near class-A for large signal operation to provide better linearity and output swing. Therefore, PAE at 6-dB back-off from P1dB can be improved, and DC power consumption can be reduced. As the pad used has internal resistance, the adaptive-bias cannot provide the bias normally. So we use an external adaptive-bias to function like the ideal adaptive-bias network. According to the measurement results, this Ka-band PA provides 21.3 dB small signal gain, OP1dB is 16.6 dBm, and PAE at OP1dB is 21.4 %, PAE at 6-dB back-off from P1dB is 12 %. Compared with Class-A PA, the proposed PA saves about 50 % DC power consumption, and the PAE at 6-dB back-off from P1dB can be improved by 1.5 %. Gm compensation technique can also enhance OP1dB by 0.3 dBm and the PAE at OP1dB by 1.5%. This PA can enhance PAE at OP1dB and other back off power level points.