Research On Anti-interference Shortwave Receiver Front-end

With the ever-changing development trend of the communications industry and the ever-increasing demand for communication quality in practical projects,researches on high-performance receivers has received increasing attention from researchers in recent years.Short-wavebands tend to have smaller absolute bandwidths.At the same time,the short-wave propagation characteristics make the interference in this band more severe than in other bands.Therefore,the linearization of the device becomes more important,and the short-wavelength wavelength is longer.It is often relatively large,so how to realize the miniaturization of the short wave receiver system is also a very important issue.Based on this trend,this article studies the selection of frequency filters,high linearity amplifiers,and automatic gain control circuits for key components of the short-wave receiver front-end,AGC,and analyzes the architecture of the system based on the analysis of key technical indicators of the receiver.Research design.The filter theory and the basic design synthesis method were studied and analyzed.The characteristics of varactor diodes were discussed.From the lumped parameter point of view,an electrical tuning filter with high Q value,low insertion loss,miniaturization,and large tuning range was designed and manufactured.Device.At the same time,the method for improving the linearity of the amplifier is discussed,focusing on the balanced structure and feedforward technology,and using the two techniques in combination to design the amplifier to suppress the second-order and third-order intermodulation products.There is a clear improvement.Based on the analysis of the key technical indicators of the receiver system and the above research on the value of each key device,the system architecture of the receiver front-end is designed,and the working principle and key quality indicators of the automatic gain control circuit AGC are briefly analyzed.And using the VCA810 and other chips designed and manufactured automatic gain control circuit AGC module to ensure the stability of the output signal.Finally,a cascade test of all devices was performed,and the final test results basically reached the expected index requirements.