Research On Superheterodyne And Direct Detection Low Noise Receiving Front End Of W Band

W-band?75¹10GHz?is a"window"for the propagation of millimeter wave in the atmosphere.It plays a significant role in millimeter wave radar,communication,imaging and other fields due to low transmission loss,wide frequency bandwidth and short wavelength.Receiver is one of the most widely used systems in the field of electronic and communication.It has always been the focus and hot spot of research.As a key component of the receiver,the receiving front-end has an important impact on the performance of the receiver.Therefore,this thesis mainly focuses on the W-band superheterodyne and direct detection radiometer receiving front-end.According to the anticipated technical specifications of superheterodyne receiver,the receiving front-end consists of low noise amplifier modules,frequency doubling and mixing module,intermediate frequency amplifier module.Next,each module is designed.The design of active circuit mainly includes chip selection and power supply circuit.The design of passive circuit mainly includes waveguide-coplanar waveguide transition structure and E-plane finline bandpass filter.In order to ensure the feasibility of the scheme,each module is processed and debugged separately,and its indicators are tested and verified.Fianlly,each module is cascaded.The receiving front end is tested.The test results show that the gain of the superheterodyne receiving front end is greater than 39dB,and average noise figure is less than 5dB from 94 to 96GHz.Millimeter wave radiometer has the characteristics of high sensitivity and good security.It has been widely used in security imaging,meteorological observation and other fields.The research work of radiometer is based on a thorough understanding of the working principle of radiometer.In this thesis,characteristics of different systems and structures of radiometer are compared.The realization scheme of the radiometer is based on the specific application background.According to the requirements of the project indicators,W-band two-stage cascade low noise amplifier,E-plane finline bandpass filter and detector are integrally designed.The shielding cavity and DC layout are dsigned and reasonably distributed to make the structure of radiometer more compact.Finally,f₀^f₀?10?3GHz,?f₀?10?3?^f₀?10?6GHz,?f₀?10?6?^f₀?10?10GHz single-channel narrow-band radiometer have been developed.Parameters of the radiometer are tested.The suppression is greater than 5dB at 1 GHz deviation from the upper and lower sidebands.When the transient time is 0.5ms,the temperature sensitivity of the three modules is less than 0.7K and linearity is better than 0.997.Overall performance is good.