No abstract

No abstract

A microstrip diplexer that uses different types of resonant structures to exhibit four channels at two different outputs is presented in this paper. A procedure for synthesizing the diplexer with two dual‐band filters having the required passband characteristics is also proposed. To reduce the interference between the filters at different outputs, the original structures of the dual‐band filters are modified by inserting embedded impedance transformers at the inputs of the lumped‐element resonators in the filters. Another component, working as an inductive compensation, is connected to the common input port to achieve the desired quad‐channel characteristics when the filters with embedded impedance transformers cannot eliminate the interference between the channel filters. To verify the proposed design method, an experimental prototype with four channels located in commonly used wireless communication bands is fabricated on a commercial printed circuit board substrate. The diplexer is highly compact; the measured insertion losses of all passbands are <2.8 dB and the associated return losses are >15 dB in the desired passbands. The isolations between the four passbands of the two outputs are all >30 dB. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:883–888, 2017

A microstrip diplexer consisting of dual-mode ring filters with different feeding locations and sectional SIR ring structure is presented in this paper. The new feature of ring filter consisting of sectional step impedance resonators, of which the feeding capacitors are placed at appropriate locations to achieve the transmission zeros close to the desired frequency points, is proposed. The new type of the ring filter is not only compact in size, but it also can eliminate the superior responses of the conventional ring filter. By connecting one input of two ring filters with the quarter-wave transformer, a microstrip diplexer can be realized without altering the original filter characteristics. The experimental diplexer with two passbands is 3.6GHz and 5.0GHz.The measured insertion losses in the pass bands are less than 1.6 and 1.6dB, respectively. The isolation between two passbands is greater than 30dB and the input return losses of two passbands are about 20dB.