Study of a Novel Zoom Spectrum Analysis Approach for Wireless Communication Analyzer

To perform FFT-based measurement in wireless communication analyzer, the frequency range and resolution on the x-axis of a spectrum plot depend on the sampling rate and the number of points acquired. However, the sampling rate of the acquisition front end is fixed in wireless communication analyzer, which implies a large size FFT to be used for getting high frequency resolution. On the other hand, it is necessary that the analysis range and the frequency resolution can be set by user. Aiming to solve these problems, a programmable zoom spectrum analysis method with multistage filtering technique is presented in this paper. The zoom FFT technique is investigated firstly, and then the key process is discussed in detail, such as the complex modulation, decimation filter and down-sampling. Especially a practical scheme of programmable multistage decimation in wireless communication analyzer has been given. Finally, the simulation results indicate that the frequency spectrum is more precision by using this method, and the decimation factor can be set by user between 2~20000 (1-2-5 step) in the application of a certain wireless communication analyzer.