Synthesis of Duplexers With the Common Port Matched at All Frequencies

Abstract

I. INTRODUCTIOND UPLEXERS are three-port selective networks, mainly used for connecting a single antenna to the transceiver of a communication system (with the receiving and transmitting bands more or less close together). They are typically constituted by two filters, whose inputs are connected to the first port (referred to as the antenna port) through a suitable three-port network (referred as the junction); the outputs of the filters are the other two ports of the duplexer (TX port and RX port). In the simplest type of duplexer, the junction is realized by means of a nonreciprocal three-port (circulator); in this way the interaction between the two filters is removed and the design of the duplexer reduces to that of two filters taken separately. This solution, however, is not always possible or convenient, for several reasons (cost, additional unwanted effects, etc.), so several approaches to the design of duplexers employing a reciprocal three-port junction have been developedAnyhow, all of them assume the classical topology of the duplexer recalled above, i.e., two filters connected through a three-port reciprocal junction. Recently, some works have

Advanced Butler Matrices With Integrated Bandpass Filter Functions

“…is a square matrix of dimensions . In recent years, there has been increasing interest in the general synthesis of multi-port networks based on coupled resonators [32]- [35]. However, many limitations of fully direct analytical synthesis methods have been faced, both in the definition of the polynomials of networks with more than three ports and with the maximum number of couplings that each resonator can sustain [36].…”

“…The conversion between the different types of matrices can be performed either analytically for some simple cases [35] or through numerical methods [39]. However, these techniques proved their validity mainly for multiplexing applications, and in particular when the transfer function exhibits all single poles [35]. If the last condition is not met, the method based on the derivation of the equivalent transversal network cannot be used.…”

Scattering matrix solution for an ideal star-junction multiplexer based on ladder-type filters

“…This topology provides compact size, minimizing the total area of the multiplexer but shows a strong interaction among filters when these are individually designed with classical techniques and connected afterwards. Several works have proved general synthesis procedures that consider the multiplexer as a whole to overcome this situation [1][2][3]. However, these methods are limited as the number of channels increases because of the round-off errors produced in the iterative procedure.…”

A General Coupling Matrix Synthesis Method for All-Resonator Diplexers and Multiplexers

“…The configuration offers high flexibility, and various topologies can be realized by appropriately coupling the resonators. Clearly, traditional CM synthesis methods are no longer applicable [12]. This paper targets a general CM synthesis method for these all-resonator diplexers and multiplexers.…”

“…However, there is no available analytical method for many topologies such as the targeted all-resonator diplexers and multiplexers in this paper. In [12] and [13], a pioneering analytical method is proposed based on polynomial calculation and obtains successful results. However, this technique is only applicable to a particular type of all-resonator multiplexer.…”