A Novel Compact Broadband SIW Six-Port Junction for Angle-of-Arrival Applications

Abstract

A compact broadband SIW six-port junction based on a novel topology and its application in AoA (angle-of-arrival) finding system are proposed in this paper. The miniaturization design philosophy of the six-port junction is based on the change of the conventional topology rather than the special structure of the discrete component or the advantage of the fabrication technology. The proposed six-port junction is constructed by two multi-step H-plane Hybrid couplers, one complementary CSRR (split-ring resonator)-loaded wideband 90 ° phase shifter, two power dividers, and two extra phase shifters of arbitrary phase. The additional phase differences introduced by the extra phase shifters don’t deteriorate the application performance based on the S-parameters requirement of the six-port junction design. The power divider and the adjacent extra phase shifter are realized by one E-plane 3dB coupler with one port short by metalized holes. The combination of E-plane and H-plane coupler significantly reduces the volume of the entire six-port junction. The fabrication of the prototype is measured by a commercial vector network analyzer and shows a good agreement with the simulation results. The fractional working bandwidth is 32.2% at 7.15 GHz and more than 20% volume is reduced compared with other designs with comparable bandwidth. Besides, to directly verify the availability of the novel topology, a simplified six-port AoA finding system utilized the proposed six-port junction is realized. The maximum average error of the measured incident angle in the entire bandwidth is no larger than 1.65°, which is comparable to the traditional system. However, it’s worth to be noted that the proposed structure can make a considerable reduction of volume and can be utilized widely for the miniaturization design of the six-port measurement systems.