調頻解調器設計

Abstract

本論文描述調頻信號的原理及數種常見的調頻解調方式，並提出適用於實驗性家用無線電話系統的調頻解調器，限制器，信號強度偵測器與壓縮擴展器。 因進入調頻解調器的載波頻率為125kHz，所以使用計數器形態的調頻解調器，此解調方法是將調頻信號轉成脈波寬度調變信號後再經過低通率波器得到語音信號，此調頻解調器屬數位式，故解調器前加一個限制器是必須的。為了使此家用無線電話開機時，可以偵測出無人使用的頻道，故將信號強度偵測器與限制器做在一起。為得到較好的信號傳輸，也製作了壓縮擴展器。 調頻解調器，限制器，信號強度偵測器與壓縮擴展器已由UMC以DPDM製程，0.5微米技術製作，並完成測量。

In this thesis, the principle of FM signal and several ways to recover the original information from a FM signal are described. For an experimental one-chip in-door cordless phone, the FM demodulator, limiting amplifier, signal-strength indicator and compander are presented. The carrier frequency of the FM signal is 125kHz before entering the FM demodulator, so a counter-type FM demodulator is used. The FM signal is transferred to PWM signal, then PWM signal passes through a low-pass filter for getting a message signal. The FM demodulator is belong digital type, so it is necessary to add a limiting amplifier before FM demodulator. In order to detect the unused channel when the wireless telephone turned on, the signal-strength indicator is implemented. For achieving better performance in the presence of noise, and then removing the effect of the predistortion, the compander is used in the FM system. FM demodulator, limiting amplifier, signal-strength indicator and compander are fabricated with UMC CMOS 0.6 technology, Double-Poly-Double-Metal (DPDM) process and it is also measured.