Spectrum Analyzer Key Technologies And FPGA Imple Mentation

With the development of wireless communication technology, measurement technology is gradually developed. For the measurement of a signal can be divided into the time domain and frequency domain, time domain and frequency domain measurements can be measured to contact with Fourier transform and inverse Fourier transform, time domain measurement instrument tool is generally oscilloscopes, frequency domain measurements most used instrument is a spectrum analyzer. Spectrum analyzer measuring instruments is belonged to a high- value products, demanding for communications research, production and maintenance, applications are more and more popular.From the domestic spectrum analyzer research capability and technical level, there is no independent intellectual property core technology. The measurement accuracy is not enough, measurement range is limited, so the study of key technologies becomes meaningful.This article introduces two traditional types of spectrum analyzers, one is based on a Fast Fourier Transform analyzer, and another spectrum analyzer is based on the superheterodyne analyzer. Two ways compared to superheterodyne spectrum analyzer relatively inexpensive, wide measurement range, but can not measure the presence of phase information and other shortco mings. FFT spectrum analyzer mode is high measurement accuracy can measure the instantaneous signal characteristics, the price is relatively expensive.Based on the above two structures, the paper focuses on the modern spectrum analyzer several key technologies:1. At the structure of the design, the structure of the spectrum analyzer of this study is still used in the RF front-end and traditional superheterodyne spectrum analyzer as the input signal mixing two or three times, then the output signal of the mixer sampling, then all subsequent processing is carried out in the FPGA.2. Spectrum analyzer design includes a lot of passive filter design. This article uses a cutoff frequency of 700 Mhz characteristic impedance of 50 ohms 6th order Butterworth low-pass filter as demon, detailing the analysis of the project LC filter design. result of LC design is the attenuation is 3.037 db for frequency of 700.9MHZ.3. In the design of the scanning module, the module uses the local oscillator phase- locked loop is based on F4351 and scan logic is performed in an FPGA design, focusing on the timing of scan logic design, describes the scan logic implementations method. When the phase lock frequency is set to 90 Mhz, the power can reach 22 d B, and the phase noise is-117@100KHZ.4. IF signal is sampled Using AD9280 chip after the signal processing entirely in the FPGA. n the design of FPGA digital intermediate frequency, the first to use digital NCO 10 MHz two digital orthogonal signal, and then using the CIC extraction, the extraction rate for 2 to 32 can be adjusted, and then through the FIR digital filter design, FFT design and digital demodulation. The above modules are designed to give a specific design methods and design a timing chart.On the basis of more detailed analysis on the part of the above design are also part of the verification, which uses a passive filter verification Agilent ADS simulation software to simulate obtain simulation results. Verifying the scanning module using the method oscilloscope FFT function. Two verification methes can be used in FPGA design, for which the signal flow can be grabbed by embedded logic analyzer signaltap after output. Scanning and detection can be observed by digital logic simulation software. This article is aided an project of internship company, due to the length and workload This article covers only the spectrum analyzer key technologies.