Microwave Circuit Design Facing X-band Radar System Application

X-band doppler radar has a wide range of applications in civilian areas,such as the anti intrusion radar used on the security.Anti intrusion radar applies the Doppler principle,it determine whether there is invasion by detecting the Doppler shift of radar.The low cost security radar on current market has short detecting distance and low sensitivity.Although the high quality radar has a good performance,but the cost is too high,which limits the popularity of security radar.In order to solve the contradiction between performance and cost of security radar,the security radar designed in this paper applies a new circuit scheme.In this paper,using discrete field effect tube with diode to setup radar system,and makes a reasonable distribution of indicators.The final designed radar not only has a far detecting distance and high sensitivity,but also has a low cost,solving the contradiction between the performance and cost of security radar.The Doppler radar designed in this paper can not only be used in security,but also can be used in the field of traffic speed test.First of all,this paper puts forward a kind of RF front-end circuit design of X-band radar sensor.The program consists of two parts,radio frequency,intermediate frequency signal processing.The radio frequency part by medium oscillator,power splitters,amplifiers,low noise amplifier,mixer,send and receive antennas.Intermediate frequency signal processing part is composed of intermediate frequency signal amplifier and intermediate frequency signal SCM processing.It develops a reasonable design of RF front-end and completes the indicators distribution according to practical requirements.Then completes the radar simulation design of rf circuit.The emission part of this RF front-end consists of dielectric oscillator,power divider,power amplifier and emission antenna.Dielectric resonator oscillator adopts parallel feedback structure to realize the output power of 8dBm.power divider adopts T equal structure to halve output power of the dielectric resonator oscillator.Power amplifier output power is 12dBm.Receiving part consists of the receiving antenna,low noise amplifier and mixer.In which the low noise amplifier adopts the field effect tube to realize the function,the gain is 13dB,the noise figure is less than 2dB.Mixer adopts diode single balanced mixer,mixer gain is-8dB.Transmitting and receiving antenna adopt microstrip antenna,the gain is 19dB,E plane and H plane angle are 30 degrees,S11 is better than-15dB.This paper details the working principle and design method of each module mentioned above.At last,a reasonable amplification of multi-level operational amplifier is used to amplify weak intermediate frequency signals and improve the level of intermediate frequency signals,so as to improve the radar detection range.This paper designs a signal processing system with regard to the intermediate-frequency processing of Doppler radar.Stm32 SCM is used to analyze intermediate frequency signals,analyzing the frequencies,so as to obtain velocity information of moving objects.According to practical testing results,it can detect human movement in 40 meters away.RF front-end and radar signal processing part are integrated in design to realize the miniaturization of radar module.