應用於自導式天線陣列的負回授相位補償器

Abstract

相位補償在電子式多天線的通訊系統裡是一個重要功能，而電子式多天線通訊系統中又以自導式相位陣列 (Self-steering Phased array) 系統最受歡迎，藉由波束 (Beam-forming) 成型的功能，使其朝向輸入訊號的方向，進而提升接收器的訊噪比 (SNR) 及通信傳播鏈結 (Link) 性能。在本論文中，學生提出了一種可運用在接收器 (Receiver) 的RF前端，使用負回授 (Negative feedback) 的相位補償的架構，用來達成自導式波束成型的功能。

本晶片是設計在以2.5 GHz為中心頻率的相位補償器，使用標準 0.18-μm CMOS製程。此電路主要由低雜訊放大器 (LNA)、功率偵測器 (Power Detector / PWD) 及相位移位器 (Phase Shifter) 和差動放大器 (Differential AMP) 組成。由量測得知，此電路在中心頻率為2.5 GHz時，對輸入相位範圍為 -90° 到 +90°產生相位補償的動作，使兩輸入訊號的相位差為零 (In-pahse)，由功率輸出對輸入相位差可觀察到有加相位補償器可改善2.07 dB左右，核心電路增益為 -2.74 dB，總面積為2.6 mm2，當操作電壓是1.8 V時，核心電路的最大直流功率為77mW。

Beam-forming is one of the most important functions in multi-antenna communication systems, such as self-steering phased array systems. Making antenna radiation towards the direction of the incident RF wave can improve the SNR (Signal to Noise Ratio) and the communication link. In this thesis, a negative feedback phase compensator architecture is proposed and used in receiver RF front-end.

A 2.5 GHz phase compensator is designed in standard 0.18-μm CMOS technology. The phase compensator consists of LNAs, a power detector and phase shifters. At the center frequency (2.5GHz), the compensator generates dc control voltage to the phase shifter with input a progressive phase shift from -90° to +90°, make the output signal in-phase. The output measurement results show the array factor could be improved about 2.07 dB. The gain of chip is about -2.74 dB without output current adder and occupies an area of 2.6 mm2. The DC power consumption of the core circuit is about 77 mW from 1.8 V supply.