【正文】
題目:簡易頻率特性測試儀 (E題)作者:紀(jì)強(qiáng)、朱志兵、張雅希賽前輔導(dǎo)教師:黃光明 文稿整理輔導(dǎo)老師:黃光明摘 要 本系統(tǒng)是基于零中頻正交解調(diào)原理的簡易頻率特性測試儀。采用AD9854 DDS集成芯片、C8051F020作為控制平臺實現(xiàn)正交掃頻信號源,RLC串聯(lián)諧振電路用作被測網(wǎng)絡(luò),AD835乘法器、低通濾波器、同相比例放大電路構(gòu)成零中頻解調(diào)模塊,與正交掃頻信號源共同構(gòu)成簡易頻率特性測試儀。經(jīng)最終測試,本系統(tǒng)能很好地完成對被測網(wǎng)絡(luò)頻率特性和相頻特性的曲線顯示。Abstract The simple frequency characteristic tester system is based on the principle of zeroif quadrature demodulation. It uses AD9854 DDS integrated chip and C8051F020 MCU as the control platform to carry out the quadrature sweep signal generator. RLC series resonant circuit is used for the under tested network. AD835 multiplier together with lowpass filter and inphase operational amplifier form the zeroif demodulation module. The quadrature sweep signal generator and the zeroif demodulation module make up the simple frequency characteristic tester. Through the final test, the system can show the frequency and phase response of the under tested network correctly.1 系統(tǒng)方案 方案比較與選擇方案一:采用鎖相環(huán)間接頻率合成方案。鎖相環(huán)頻率合成在一定程度上解決了既要求頻率穩(wěn)定精確,又要求頻率在較大范圍可調(diào)的矛盾。但輸出頻率易受可變頻率范圍的影響,輸出頻率相對較窄,不能滿足題目1MHz40MHz的高頻要求。方案二:采用直接數(shù)字頻率合成(DDS)方案。DDS技術(shù)具有輸出