高动态扫频仪的设计与实验

针对现有的扫频仪动态范围小、应用范围受限等问题,基于若干集成电路设计了一款高动态扫频仪。该扫频仪利用2个DDS芯片产生正交信号,利用MC1496模拟乘法器作为零中频检测器,利用LTC2440完成高精度采样及数字滤波。该系统中,一路DDS相位0/90可变,另外一路DDS相位保持不变,由此构造了消除直流偏置的零中频算法且信号处理及显示在PC机完成。实验测试结果表明,其动态范围接近120 dB。利用该扫频仪能够完成滤波器、放大器等器件幅频特性的测量,可广泛应用到高频器件生产及测试中。

Design and Experiment of a High Frequency Sweeper with High Dynamic Range

In order to improve the dynamic range of available sweepers,a high frequency sweeper is designed by using several ICs.The DDS chip is utilized as an orthogonal signal generator,analog multiplier (MC1496) is adopted as a zero-IF detector,and data are acquired and filtered by the LTC2440.Furthermore,an algorithm is proposed which can remove current offset by changing the phase of one DDS chip and PC is utilized to process these data.Experimental results show that the dynamic range of this sweeper is about 120 dB.The characteristics of the filter and amplifier can be measured.The sweeper can be widely applied to the production and testing of high frequency components.