Synthesis And Design Of Multiplexer

With the rapid development of wireless communication technology, the available spectrum resources in the wireless communication system become more and more intense, and the channel has become more and more crowded. It’s necessary to separate and combine the channels reasonably which is a big challenge to design microwave multiplexers. Thus, it is of great significance to study the methods of synthesizing and designing multiplexers of high performance and miniaturization.First of all, the synthesis method of star junction multiplexers which is based on the characteristic polynomial theory proposed by G. Macchiarella is studied in this paper. The characteristic polynomial expressions of star junction multiplexer and its channel filters are derived. The iteration method is also introduced to evaluate the polynomials. The S parameter and group delay response curves are obtained according to characteristic polynomial of the multiplexer and the normalized coupling matrix is obtained from the characteristic polynomials of channel filters. The de-normalization of the prototype network is given to compute the design parameters, such as coupling coefficients, resonant frequencies and external Qs. This synthesis method is very flexible, because we can choose the topology of multiplexer after obtaining the frequency response which offers some extent of freedom. Examples of multiplexer synthesizing are presented to validate this method.Then, the extraction of coupling matrix of Generalized Chebyshev filter with arbitrary topology is studied. An approach based on matrix rotations is given. The new matrix is obtained through the matrix of folded prototype and a series of optimum rotation pivots and angles which are evaluated by optimization. Besides, this method is little sensitive to the starting point, so the value has little effect on the final results.Next, the computer-aided tuning technique in HFSS is studied. The formula of the theory of Y matrix and group delay is illustrated. The effects of different kinds of lumped ports on simulating results are discussed and the formula to compute the impedance of lumped port is given. The traditional way of tuning is blindness and time consuming to optimize11 S and21S curves directly. The method proposed in this paper can directly find the relations between the design parameters, such as coupling coefficients, resonant frequencies and external Qs, and dimensioning of model. We canobtain the desired dimensioning of filter models very fast, so it efficiently shorten the design circle.Finally, a synthesis program based on MATLAB GUI design is given, which allows a simple and fast design of star junction multiplexer and simplifies the design procedure. It would be very helpful in engineering application.