VXI射频实时频谱分析仪模块数字中频技术研究

介绍了实时带宽为 10 MHz的 VXI射频频谱分析仪模块数字中频技术 ,采用高速 ADC直接数字化射频中频信号 ,基于一种新颖的模数混合自适应前馈 AGC技术扩展测量动态范围 ,基于大规模 FPGA专用芯片实现数字下变频、可程控带宽分辨率滤波器 ,基于 DSP实现 FFT频域分析以及相关时域分析 ,并可扩展 FPGA数字检波器支持数字扫频分析功能 ,通过VXI总线以及中断通信方式实现数据高速传输 ,从而大大简化电路构成 ,有效减小模块体积 ,真正实现射频中频信号实时、快速、宽带频谱分析。文中给出了相应实现方案与实验结果。

A Digital IF Approach for VXIbus-based RF Realtime Spectrum Analyzer Module

A digital IF approach for VXIbus-based RF realtime spectrum analyzer module is presented. By means of a adaptive realtime feedforward AGC technology and a closed-loop feedback gain/attenuation precontrol technology, very wide dynamic range is enabled. With a fast ADC, 10.7MHz IF signal is sampled directly, then low frequency I and Q pairs are obtained by applying a Hilbert transform on the sampled digital signal in digital domain. The digital down converter (DDC) implemented in FPGA chip here is based on the Hilbert transform for I/Q demodulation, decimation and antialias filtering of the I and Q pairs with CIC filter and HB filter, and resolution bandwidth (RBW) filtering with a linear-phase FIR filter. Finally, all frequency domain and time domain analyses such as FFTs or digital swept analysis are implemented in DSP, and the analysis results are transfered fastly to slot 0 controller through VXI interrupt mode. The all-digital IF technology enables the modularization of the RF realtime spectrum analyzer, an experimental scheme and simulation results are described.