Compact broadband couplers based on the waveguide magic-T junction

In this paper, a broadband 180° waveguide directional coupler based on a modified magic-T junction is presented. The well-known magic-T waveguide junction is effectively modified and optimized leading to enhanced performance. Moreover, the volume of the proposed enhanced magic-T is similar to the classic junction. The novel magic-T proposed uses an iris in the E port, a single width step in the H port, a simple post in the junction and reduced height in the H and common ports. The bandwidth of the directional coupler can be significantly enlarged with a proper optimization of these four key elements. Different designs are presented covering the full standard rectangular waveguide band, over 40% relative bandwidth, with more than 25 dB return loss in the four ports. In addition, a compact bend with integrated transformer is introduced at the input/output interfaces.

[1]  W.A. Tyrrell,et al.  Hybrid Circuits for Microwaves , 1947, Proceedings of the IRE.

[2]  Xiaoping Chen,et al.  A Planar Magic-T Structure Using Substrate Integrated Circuits Concept and Its Mixer Applications , 2011, IEEE Transactions on Microwave Theory and Techniques.

[3]  H. Riblet The Short-Slot Hybrid Junction , 1952, Proceedings of the IRE.

[4]  U. Mahr,et al.  A Multimode Feed System for Angle Diversity Operation in Two Polarizations , 1990, 1990 20th European Microwave Conference.

[5]  Ruey-Beei Wu,et al.  A Laminated Waveguide Magic-T With Bandpass Filter Response in Multilayer LTCC , 2011, IEEE Transactions on Microwave Theory and Techniques.

[6]  T. Kawai,et al.  An H-plane waveguide 180-degree hybrid~A planar magic-T~ , 2010, The 40th European Microwave Conference.

[7]  Keum Cheol Hwang,et al.  Design and Optimization of a Broadband Waveguide Magic-T Using a Stepped Conducting Cone , 2009, IEEE Microwave and Wireless Components Letters.

[8]  W. K. Kahn E-Plane Forked Hybrid-T Junction , 1955 .

[9]  V. Minassian,et al.  A Ku/Ka dual-band dual-CP tracking feed , 1996, IEEE Antennas and Propagation Society International Symposium. 1996 Digest.

[10]  J. A. Ruiz-Cruz,et al.  A Pseudo-Elliptical Response Filter at W-Band Fabricated With Thick SU-8 Photo-Resist Technology , 2012, IEEE Microwave and Wireless Components Letters.

[11]  Youn H. Choung,et al.  NASA acts autotrack antenna feed system , 1986, 1986 Antennas and Propagation Society International Symposium.

[12]  M. T. Faber,et al.  High-Output, Single- and Dual-Diode, Millimeter-Wave Frequency Doublers , 1985 .

[13]  A. Kerr,et al.  A Broadband In-Phase Waveguide Power Divider/Combiner , 2000 .

[14]  C. G. Montgomery,et al.  Principles of Microwave Circuits , 1965 .

[15]  Jr. R. Wyndrum Microwave filters, impedance-matching networks, and coupling structures , 1965 .

[16]  J. Ritter,et al.  Efficient FDTD/matrix-pencil method for the full-wave scattering parameter analysis of waveguiding structures , 1996 .