Computer Aided Optimization Of Diplexers

Diplexers, a sort of three-port filter, can separate different band of frequency, and are the key component in the RF communication system. Diplexer designing is more complicated and more difficult than two-port filter designing. Scientists in this research field around the world had worked on high performance diplexer for more than half century, their theory and means are mainly based on network synthesis theory.With the rapid development, the demand for information increase in recent years quickly. In this situation, the requirements on diplexer' s qualification are more strict. Whereas, the network synthesis theory could not have more great development, and is hard to match the rapid development of communication technology.In this thesis, we use circuit optimization technique to replace the network synthesis theory and design high performance diplexers on the basis of LC network. First, we formulate the objective function for the use of diplexer optimization, and calculate the gradient of the objective function with respect to the element parameters. Then we establish the optimization means on the basis of objective function, and take advantage of the flexibility of circuit optimization technique to obtain the optimum parameters of diplexers.In order to implement the optimization of diplexers, an optimization software have been designed in this thesis. According to the designing demands, such as bandwidth, stop-band attenuation, the optimization software can optimize the diplexers. Finally, we use the optimization software to optimize a diplexer, and show the optimization effect.