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This paper describes a novel feed system for compact antipodal Vivaldi antenna arrays on a single layer of substrate integrated waveguide (SIW) by using SIW H-plane right-angled power dividers. The proposed antenna systems are composed of a Vivaldi array and an H-plane right-angled corner power divider which includes an over-moded waveguide section. Based on the number of antennas in the Vivaldi array, mode converter sections at K-band and Ka-band frequencies are designed, fabricated, and measured when feeding Vivaldi antenna arrays with two, three, and four antennas. Right-angled SIW power dividers are employed to obtain controllable phase distribution over the output ports which consequently controls the beam shapes of the systems. The phase relationships in the output ports are varied to obtain different pattern directions for different applications. The two-way divider system with 180-degree phase difference and three-way divider system are fabricated and measured; simulation results are presented for other designs. The measured results are in good agreement with simulations which confirms the design approach. All systems achieve good performance and meet all design goals including a return loss better than 10 dB in the operating bandwidth, gain higher than 8 dB for all systems, and radiation and polarization efficiencies higher than 80% and 98%, respectively.

This paper proposes a new beam steering antenna system consisting of two variable reflection-type phase shifters, a 3 dB coupler, and a 90° phase transition. The entire structure is designed and fabricated on a single layer of substrate integrated waveguide (SIW), which makes it a low loss and low-profile antenna system. Surface mount tuning varactor diodes are chosen as electrical phase control elements. By changing the biasing voltage of the varactor diodes in the phase shifter circuits, the far-field radiation pattern of the antenna steers from −25° to 25°. The system has a reflection coefficient better than −10 dB for a 2 GHz bandwidth centered at 17 GHz, a directive radiation pattern with a maximum of 10.7 dB gain at the mid-band frequency, and cross polarization better than 20 dB. A prototype is fabricated and measured for design verification. The measured far-field radiation patterns, co and cross polarization, and the reflection coefficient of the antenna system agree with simulated results.

A K-band frequency-selective front-end system for monopulse tracking applications is presented on a single layer of a substrate-integrated waveguide (SIW). The circuit comprises an antenna array of two Vivaldi antennas, a frequency-selective power combiner, and two frequency-selective SIW crossovers, which eliminate the need for subsequent filtering. Its performance is demonstrated in terms of sum and difference patterns, gain, and scattering parameters. In order to validate the design procedure, the monopulse tracking front end is fabricated and measured. It has a bandwidth of 540 MHz with an operating frequency range of 23.63-24.17 GHz. The sum and difference patterns are provided by in-phase and out-of-phase electric fields. The maximum achievable gain is 6.2 dB at the mid-band frequency, and a 30-degree field of view is obtained. The measurements are found to be in good agreement with simulations.

A simple yet efficient substrate integrated waveguide (SIW) crossover circuit is presented. It is formed by excitation of two orthogonal full-wavelength (TE102-mode) resonators whose centers coincide with that of the symmetric SIW cross junction. Half-wavelength (TE101-mode) resonators are added in all four ports to increase bandwidth. The SIW crossover is designed to operate at 24.75 GHz with a bandwidth of 3 GHz. A prototype is fabricated on RT/duroid 6002, and measurements agree well with simulations. The minimum measured return loss is better than 17 dB, maximum insertion loss is 1.1 dB, and isolation between the channels is better than 12 dB. Based on these results, two other crossovers with isolation better than 23 dB are proposed.