The Research And Design Of Rf Front-end Circuit In Ultra-short Wave Receiver

In recent years, with the increasing social demand, wireless communication technology has become the most dazzling star in the information industry, and ultra-short wave technology, as the important branch of wireless communication, has not limited to the application of professional areas, but widely extended to various fields, including military, transportation, medical and fishery industries, and so on.The main contents of this paper are the study and design of the ultra-short wave FM receiver, which is based on27.5MHz～39.5MHz. By comparing several various schemes, the classical dual-conversion superheterodyne structure is selected to implement higher sensitivity and large dynamic range, which mainly includes pre-filter, automatic gain control (AGC) amplifier, mixer, the phase-locked loop (PLL) frequency synthesizer circuit and FM demodulation circuit. Among them, the phase-locked loop frequency synthesizer circuit is mainly used to produce the local oscillator signal of receiver. In this paper, a hardware receiving platform system is designed by focusing on each module of the overall scheme. In the system, the radio frequency signals are firstly received by the antenna, then, though amplifying and mixing, audio signals will be output by the demodulation of orthogonal frequency discriminator.Firstly, the topic background and present situation of the receiver are introduced in the paper; Secondly, the relevant performance indicators of the receiver are analyzed in detail, including sensitivity, linearity, noise figure and so on; Then it discusses the design of this hardware circuit, which mainly include phase-locked loop frequency synthesizer, pre-filter, automatic gain control circuit, mixer, narrow band frequency modulation circuit module, and it gives schematics of each module and part of the circuit simulation diagram; Finally, the system hardware was tested, and its problems and results are analyzed in the test. The extensive test results show that all indicators of the designed system have met the design requirements.