Study Of The Uhf Band High-temperature Superconducting Receiver Front-end Subsystem

Radar technology developed rapidly after the World WarⅡ,now it has beeningused widely both in military and civil fields,so it is very important to study the receiverwhich is the key component for the radar system. Modern warfare requires the radarreceiver not only having high sensitivity and selectivity but also keeping great ability ofanti-jamming which is quite a challege for normal receiver, that is the reason therecoming the high temperature superconductor(HTSC) receiver.In this paper some basic property of HTSC and recent development of HTSCtechnology is first introduced,then the principle of component for the frond-end systemof HTSC receiver is given,after that more attention is focused on the design of thesub-system,finally the test result and analyse is shown.The sub-system which should be put in cryogenic environment is composed of theHTSC filter and the cryogenic low noise amplifier, its centeral frequency is the downside of UHF band,such low frequency and temperature leads to two difficulties:ones isthe size of the filter will be too big to realize if we use the normal way to design;theother is that there is not very suitable transistor for the amplifier, HEMT can work wellin the low temperature,but its stability and reflection is bad in such frequency band.Inorder to overcome the difficulties,several methods and some special technologies areintroduced,such as the zigzag line resonator for the filter and the feedback technologythe amplifier.The design combine simulation softwares with theory calculations.In order toavoid added loss the filter and amplifier are integrated, the sub-system is the outcome ofthe integration.The front-end system is tested in the temperature of 77K, themeasurement result indicates that the noise figure is around 0.7dB, the input reflectionis lower than -15dB, the gain is above 21dB, the suppression is better than 60dB, andthe rectangle coefficient is nearby 1.The outcome of radar test tells that such receiver'sperformance on sensitivity and anti-jamming is improve to a great degree, it also showsthat the HTSC receiver has bright future in the field of military radar system.