Design Of Miniaturized And Tunable Microwave Multi-band Multiplexers

Microwave multiplexer is usually consists of some filters through certain coupling forms, It not only have the characteristics of filters, but can also be used as an isolation component to connect receiving and transmitting systems. Currently, there are more and more antennas and transceivers on the modern wireless communication platform, that the mutual interference is serious. Microwave multiplexers allow multiple transceivers share one antenna, effectively reducing the number of antennas, simplifying antenna placement, preventing crosstalk and ensuring the quantity of channels and quality of communication. Therefore, multiplexers have been widely applied in shipboard, airborne, space borne, automotive and mobile base station platforms. Multi-band multiplexer researched in this paper can achieve multichannel transceiver work at the same time. Besides, each channel can accommodate more than two pass-bands.However, in modern wireless communication system, it’s rather difficult to separate the signals in multi-band because of crowded frequency band, strong electromagnetic interference, and so on. At present, most of the emitter is simply works as a single RF channel to transmit the signal to the receiver. Microwave filter that realizing the important function such as frequency selective sometimes become the bottleneck of wireless communication development. In order to separate signals in different bands quickly, tunable filters arises at the historic moment. In addition, the tunable filter promotes miniaturization and integration of the equipment, which provides a new direction of the development of modern wireless communication component.In order to meet the performance requirements of miniaturization and tunability different design methods of microwave multi-band multiplexers are proposed. Here, the following aspects have been studied and completed:1. The development and the current status of the microwave filters, microwave multiplexers and tunable microwave multiplexers are surveyed. Moreover, the main research work in this paper is summarized2. the basic theory and research methods of the microwave multiplexer are analyzed. First, the synthesis of microwave multiplexer and the extraction of the external quality factor and coupling coefficient are introduced. Then, several design method of matching network of microwave multiplexer are simply discussed, such as adding eliminate susceptance circuit at the common port, adding circulator between filters, and so on. Finally, several design method of microwave multiplexer are briefly introduced and some examples are given to verify the validity of the design method.3. The odd-even mode method is utilized to analyze the basic characteristic and application of stepped impedance resonator. Based on stub-loaded stepped impedance resonators, two quad-band duplexers and a six-band triplexer are designed and measured. In addition, the measured results and simulation results are compared to demonstrate the design method.4. Based on the design method of tunable microwave filters, with the variable capacitance diode and stub-loading technology, a microstrip quad-band duplexer with two continuous tunable pass-band is presented and designed.5. Summarizing the innovation points and shortcoming of the existing work and arranging the next step to design multimode multiplexer on the basis of the previous work,then, designing the tunable multimode multiplexer.