Research On 2～18GHz Multichannel Receiving Front End

The ever-evolving wireless communication technology necessitates the fabrication of microwave components in the ultra wideband and miniaturization direction for modern electronic countermeasures systems.As the kernel component of microwave system,the receiving front end plays a prominence role in the system function,which makes the requirement of its performance increasingly strict,so it is of great value and significance to conduct research on it.This thesis introduces the design and development of a 2～18GHz multichannel receiving front-end.The modular design concept divides the receiving front end into four modules: microwave receiving,frequency source,IF and control,all of which are based on the system index and function requirements.Microwave receiving module is responsible for receiving the signal to obtain the required IF signal;The frequency source module is responsible for providing the local oscillator signal required by the microwave receiving module for twice frequency conversion.If and control module is responsible for filtering,amplifying and gain control of IF signals.In order to solve the problem of mirror frequency interference caused by wide-band signals,this design adopts upconversion superheterodyne receiving technology,which converts 2～18GHz signals up to 22.25±0.25 GHz,which can effectively suppress mirror frequency interference;In order to solve the problem of input large dynamic range up to 90 dB,this design adopts the automatic gain control(AGC)technology.Through the structure of "coupling + detection+ controllable gain",the design sets the appropriate power threshold to provide the gain of different sizes in the input of different power ranges,which can not only ensure the noise coefficient of small signal input,but also avoid the system blocking of large signal input.The test of the entire system is conducted after the design and fabrication of each module has been finished.The multi-channel receiving front-end’s dynamic range is demonstrated to be greater than 90 dB,its maximum gain is 45 dB,its gain control is 60 dB,the noise factor is less than 8dB,the gain flatness in the IF signal band is less than 1.8dB,the ability to constrict spurious is better than 60 dBc,the frequency hopping time of the local oscillator one signal is less than 200 us,and the amplitude consistency of the fivechannel is less than 2dB.Less than 20° of phase consistency.The system’s current issues are examined and enhanced,and all the indicators can satisfy the criteria.