Investigations On The Contiguous-Channel Multiplexers

The microwave payload on a communication satellite, radar system and the radio unit of a cellular base station system all need to process multi-frequency band and high-power microwave signals. Among various functional sub-systems, the high-performance microwave diplexer/multiplexer network is one of the indispensable sub-systems. In a multiplexer network, channel filters are used to select the desired microwave signals with the minimum loss and reject the interferences to a required level. In the design of contiguous-channel multiplexers, the mutual interference between the channel filters is very serious. Using the traditional design methods, several days or weeks are usually needed to get a respectable result. In order to improve the design efficiency and also to save space and mass of such sub-systems, a planar compact contiguous-channel substrate integrated waveguide (SIW) output multiplexers (OMUXs) and their systemic design method are proposed in this paper.In this paper we studied the output multiplexers based on substrate integrated waveguide technology. First, we reviewed the development of microwave multiplexers, substrate integrated waveguide and design method of microwave filters. Since the SIW components use large amount of metallic vias which require high density meshing associated with large number of unknowns, very long computation time has to be used for the full-wave simulations. Then it is impossible to design the complicated SIW OMUX by using the full-wave optimization method. Hence, novel high efficiency and high accuracy design technique needs to be developed for the computer-aid-design of SIW OMUXs. Space mapping method occurred in recently years can solve this problem commendably. Electromagnetic full wave-and circuit-simulation models are set up by using the commercial available software HFSS and ADS, Mapping relationship between physical geometries and circular elements is established through the algorithm. Then required specifications can be obtained through a few times iteration. The whole process only involved several full wave-simulation but achieved the rapid of circuit-simulation and the accuracy of full-simulation. Then using this method we did some research on SIW single band bandpass filters, dual-band bandpass filters, duplexers and multiplexers. The specific work is as follows:In the first chapter, the thesis reviewed the development of microwave multiplexers and SIW technology. In the second chapter, the basic theory of microwave filter and space mapping method are discussed. In the third chapter, this paper did some research on single-band and dual-band bandpass filters combination of SIW technology and filter design theory, and presented an efficient design method for SIW filter and validated by experiment. In the fourth chapter, based on space mapping method, the paper did some research on contiguous-channel SIW multiplexer and presented a compact planar integrated microwave multiplexer and its systemic design method. Then the paper gave several multiplexer examples to clarify the method in detail. Finally in the fifth chapter, the paper summarized the research work and gave the nature work.