使用數位控制電流導向可變增益放大器之 Ka頻段相移器

Abstract

本論文提出一使用於Ka頻段之數位控制可變放大器的向量合成式相移器，此架構可應用於5G毫米波段的通訊系統中。 此相移器主要由90˚耦合器形成相差90˚的I/Q訊號，接著透過0-π相位切換器轉換成±I/±Q訊號來實現四象限切換。並將±I/±Q訊號由可變增益放大器改變其大小，達到相位移的效果。本架構中的可變增益放大器為數位開關式可變增益放大器，由4組開關控制電流的原理改變增益放大器的大小。但因可變增益放大器在不同的大小時，相位的誤差太大，因此只能選擇前面相位誤差較小的點，導致增益範圍不夠，無法在任一象限達成0˚~90˚切換，所以最後再加上45˚切換器補償，藉此實現360˚全相位切換。 本文採用台積電 0.18 μm CMOS 製程實現，可達到等效6位元解析度，而量測結果均方根增益誤差為0.139dB，RMS 相位誤差為0.609˚，平均增益為-18.737dB，直流功耗最大為25.2mW。

This thesis presents a phase shifter digital control variable gain amplifiers in the Ka band. This architecture can be applied to communication systems in the 5G millimeter wave band. This phase shifter uses a 90˚ coupler to form an I/Q signal with a phase difference of 90˚, and then converts it into a ±I/±Q signal through a phase-invertible variable attenuator (PIVA) to realize four-quadrant switching. And the ±I / ±Q signal is changed by the variable gain amplifier to achieve the effect of phase shift. The variable gain amplifier in this architecture uses a digital controlled switch-type variable gain amplifier, and the magnitude of the gain amplifier is changed by the principle of four sets of switches controlling the current. However, because the phase error of the variable gain amplifier is too large when the gain range is large, thus only gainwith small phase error can be selected, resulting in insufficient gain range. A 45° phase shifter compensation is added at the end to achieve 360° all-phase shifting. This circuit is implemented in TSMC 0.18μm CMOS process. It has 6-bit resolution in phase shift. The measured RMS gain error is 0.139dB, and RMS phase error is 0.609˚. The average gain is -18.737dB with maximum DC power consumption at 25.2mW.