HTS Multiplexer And Its Application In Multi-channel Wideband Digital Receiver Frond-end

The high temperature superconducting (HTS) is a preferable microwave device material due to its three or five orders lower surface impedance than those of normal metals at L to X band and its large current density which can reach to 1×10~7 A/cm~2. Many low insertion loss HTS devices have been produced in recent years, including HTS filters, HTS multiplexers, HTS limiters, HTS delay lines, etc. When these high-performance HTS devices are used in the microwave systems ~ including mobile communication systems, Satellite communication systems, radar systems and electronic warfare receiver systems, these systems' performance has been greatly enhanced, which shows a great prospect of application.Though the design of HTS multiplexer is based on that of conventional multiplexer, the design procedures have to be modified due to some limited conditions when the HTS technology is in application. In this thesis, we developed the designs of HTS contiguous diplexers and HTS contiguous quadraplexers which are the key devices of the HTS receiver front-end. Experiments have been done to validate the design concept which is applied to the research and development of a new multi-channel HTS front-end in wideband digital receiver systems. The fabricated prototype of double-channel HTS front-end shows a high performance.The main results are as follows:1. We have developed the design of HTS filters, which are based on the relations between the parameters of filters' resonators and the frequency response of filters. The developed design procedures can reach to the design object more quickly and accurately without optimization process by the powerful computer simulation, which significantly reduces the designning period of HTS filters. Experiments have been done to validate the design concept. The fabricated 8-pole HTS filter and LNA modules operated at 77 K, and their performance of xxx-xxx MHz with 5 MHz wide is as follows: gain>21dB and noise figure<0.8dB.2. For the more complex and difficult design of HTS multiplexers, we have developed a "direct designing": The LC lumped parameter models of multiplexers are used for the analysis of the relations between the parameters of lumped parameter models and the frequency response of multiplexers. In this way we can know the main parameters that affect the performance of multiplexers and the trend to get an ideal matching. Thus, we can efficiently simplify the design task and significantly reduces amount of optimization time. Experiments have been done to validate the design concept. The fabricated 4-pole HTS diplexer and 4-pole HTS quadraplexer operated at 77 K shows excellent performance which operation frequency was from 3GHz to 4GHz with 500-MHz-wide channels and from 2GHz to 4GHz with 500-MHz-wide channels respectively. The insertion loss in the pass-band is less than 0.8 dB and the rejection between per channel is greater than 30dB.3. The power handling properties of a HTS diplexer have been measured. The tested power dependent frequency response of the HTS diplexer shows that the power handling capability of the HTS diplexer on the crossover region is not higher than that on the in-band region, even somewhat lower 1dB, due to larger microwave currents in the device in the crossover region.4. We have developed the technology of a new muli-channel HTS front-end in wideband digital receiver systems. The fabricated prototype of double-channel HTS front-end shows a high performance. Their performance of each channel is as follows: noise figure< 1.3 dB, P1dB=15.7dBm, OIP3=27.7dBm, G=47.8dB and S<-85dBm, when its operation frequency was from xxx GHz to xxx GHz with 500-MHz-wide channels.