Design and Implementation of Compact Diplexers using Dual-mode Cavities Hussein Ezzeddine, 1 Kamel Frigui, 1 St  ephane Bila, 1 Serge Verdeyme, 1 Fabien Seyfert, 2 J  er ^ ome Puech, 3 Laetitia Estagerie, 3 Damien Pacaud, 4 1 XLIM, UMR 7252, Universit e de Limoges/CNRS, 123 Av. Albert Thomas, 87060 Limoges, France 2 INRIA, 2004 route des Lucioles, 06902 SOPHIA-ANTIPOLIS, France 3 CNES, 18 Av. Edouard Belin, 31401 Toulouse, France 4 Thales Alenia Space, 26 Av. Jean-Franc¸ois Champollion, 31100 Toulouse, France Received 11 December 2012; accepted 22 April 2013 ABSTRACT: In this paper, the design of compact diplexers with dual-mode cavities for satellite payloads is detailed. Compact diplexers are composed of coupled resonators without additional waveguide element, leading to a more compact architecture. Two topologies are first imple- mented and compared with a standard manifold output diplexer, in terms of electrical perform- ances, compactness, and power handling. Hardware prototypes are fabricated and measured for experimental verification. A third topology is finally introduced for the design of noncontiguous diplexers. V C 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:249–258, 2014. Keywords: circuit synthesis; diplexers; microwave filters I. INTRODUCTION Manifold networks are widely used in satellite systems for connecting channel filters [1–3] in an output multiplexer (OMUX). Such waveguide elements allow a separate design of each channel; however, they contribute to increase the size and the weight of the payload. Compact microwave multiplexers [4–9] are networks composed exclusively of coupled resonators, which can be used for implementing multiplexers with a reduced number of channels. The coupled resonator network allows size and weight reduction because of the waveguide elements’ suppression, but also offer additional design flexibility since coupling between channels is also possible [7]. Several examples can be found in the literature, where several prototypes of diplexers and triplexers have been designed using various technologies [5–9]. However, one can note that all these prototypes have been implemented in single-mode configuration and only few of them are consistent with stringent constraints required for the design of satellite OMUXs. In this study, a dual-mode implementation of micro- wave diplexers is preferred for more compactness and empty cavities working on their TE 113 dual mode are employed for a matter of power handling and quality factor. Compared with our previous work [4], new designs are provided and the design procedure is improved, leading to a more robust implementation of compact diplexers with dual-mode cavities. Moreover, the current study provides a comparison between compact diplexers and a manifold diplexer in terms of compactness and electrical perform- ances (including power handling), and the two topologies of compact diplexers are characterized through prototype measurements. Finally, a third topology is proposed for noncontiguous channel diplexers. II. MANIFOLD DIPLEXER For reference, a manifold diplexer formed of two dual- mode cavity filters coupled with waveguide sections has been designed. The electrical specifications for each chan- nel are a return loss of 20 dB, and an out-of-band rejec- tion of 8 dB at 645 MHz and 18 dB at 655 MHz from the center frequency. The two 72-MHz channels are cen- tered at 10.741 and 10.821 GHz, respectively. In order to reach the electrical specifications, each channel requires a five-pole quasi elliptic function with two transmission zeros at x 1,2 561.33 rad/s (pulsations normalized with Correspondence to: Hussein Ezzeddine, e-mail: hussein.ezzeddine@etu.unilim.fr DOI: 10.1002/mmce.20760 Published online 12 July 2013 in Wiley Online Library (wileyonlinelibrary.com). V C 2013 Wiley Periodicals, Inc. 249