Design Of W-band High-sensitivity Radiometer Receiver

With the rapid development of electronic technology in modern society,new technologies are emerging in the area of remote sensing,security check,radiation imaging and many other fields.So,the requirement on the front end of receiver are constantly improving.Millimeter wave detection circuit is one of the most important components of the front-end of the receiver,which has a great impact on the performance of the RF system.Therefore,the research on the millimeter detector has far-reaching significance for the development of the technology of millimeter wave.In this paper,a direct detection circuit of W band is studied in detail.Firstly,the front of receiver of millimeter wave is briefly introduced in this paper.The development of W-band detector and low noise amplifier in China and abroad is briefly described.It can be known that the relevant technology abroad has been quite mature,while the domestic market is still in the catch-up stage.Then,the principle of detector and low noise amplifier is introduced in detail,and a reasonable design scheme is developed and verified by simulation.In this paper,the detector is connected to the circuit by diode in series,and the topology of the waveguide microstrip transition-matching network,detection diode and low-pass filter is determined.The transition from the waveguide to the microstrip takes the form of probe to the coplanar waveguide and the dc loop is added to minimize the influence on the transition performance.The matching network adopts the form of fan branches to realize the good matching within the working frequency band.The low-pass filter adopts an "?"-shape filter with a suppression degree of more than 40 dB in the frequency band of 92-96 GHz.LNA adopts three-stage amplifier,and two kinds of MMIC chips are selected according to predetermined indexes.The final gain is greater than 50 dB and the noise figure is lower than 4.5dB.The power supply circuit is designed for the low noise amplifier,which is assembled on a PCB board with the video amplifier required by the detector.Then,the test chamber for the detector and amplifier is designed respectively to carry on the physical test,obtains the respective test result.After that,they are cascade tested to get the final results.Finally,the test result are analyzed and summarized,and the following improvement measures are proposed.