RF Module Design And Implementation Of 3GHz Spectrum Analyzer

Spectrum analyzer is the most widely and largest used measuring instruments in measure of frequency domain. Super-heterodyne architecture is the main structural for designing a spectrum analyzer, which determines the overall structure of the RF modules of the spectrum analyzer, and RF module is one of the key technologies to realize spectrum analyzer, Many of its key performance indicators has an important impact for the whole performance of spectrum analyzer.This paper aim to design an economical, high performance and simple structure-based RF module of spectrum analyzer. Paper introduces the current situation of RF module designed in spectrum analyzer at home and abroad, and analyzes the mutual relationships and influencing factors of key technical indicators in RF module. Through the analysis of indicators and technical problems, design and implement the triple super-heterodyne RF module of the 3GHz spectrum analyzer. The RF module mainly consists of three modules: RF channel-link module, the LO frequency-synthesis-source module and the control module.RF channel-link module includes programmable attenuator module, low noise amplifier module, three mixing module and the frequency selection module with filters. We analyze the noise figure and gain, use the BUGET tool in ADS2008 to simulate the entire link’s budget and use electromagnetic simulation software(HFSS and IE3D) to design and simulate the key micro-strip filters in RF module. The oscillator synthesizer source module is design to implement the first LO signal sweeping from 4.1357 GHz to 7.1357 GHz, fixed frequency source, the power compensation circuit and filter circuit to achieve the target indicators. We use PLL and high-performance VCO chips to design sweep source, which is less cost and space than using YTO. The control module uses DSP + FPGA structure and SPI four-wire data transmission mode to control the sweep source and other programmable chips, which enables functions of the entire RF module.Finally, the paper completed the design and implemented the third IF(10.7MHz) output and tested related indicators. The results showed that the RF module could achieve the required targets and functional requirements.