简易频谱分析仪

【摘要】本简易频谱分析仪由模拟高中频部分、显示处理部分和波形控制部分组成。模拟高中频部分采用了二次混频结构，混频采用模拟乘法器实现，第一级扫频本振和第二级点频本振均采用DDS技术产生，滤波器采用不同Q值的晶体滤波器，检波采用经典的AM非相干检波。示波器的显示采用FPGA控制，DDS的配置和系统的总体控制采用单片机完成。系统采用了独特的一键式自动测量，操作简单。系统整体指标好，频率分辨力达到了200Hz，能够正确识别调幅、调频和等幅波三种波形及其调制带宽。

【关键词】 频谱分析仪 晶体滤波器 直接数字合成 示波器

【Abstract】：This simple spectrum analyzer is composed of HF/IF circuits, display processing and waveform controlling. The HF/IF circuits adopt dual conversion architecture. The mixers are implemented by analog multipliers while the first LO for sweep frequency and the second LO for point frequency are both generated by DDS. The filters are active crystal filters with different Q value. Detectors are classical incoherence AM detectors. The displaying on an oscilloscope is controlled by a FPGA, and the configurations of DDS chips and the controls of the whole system are accomplished by a MCU. The operation about the spectrum analyzer is very simple because a special automatic mode called one key measurement is adopted, and the system specifications are so excellent that the frequency resolution is up to 200Hz and the FM, AM and CW signals and their bandwidths can be recognized automatically.

【Key Words】Spectrum analyzer, Active Crystal Filter, DDS, Oscilloscope