Full W-Band Broadband High-Gain Monopulse Gap Waveguide CTS Array Antenna With Hybrid Beamformer and Comparator Network

This paper presents a broadband high-gain monopulse continuous transverse stub (CTS) array antenna based on gap waveguide technology, with its operating bandwidth covering the full W-band. The antenna comprises a novel hybrid beamformer and monopulse comparator network and a 16-element corporate-fed CTS array. A broadband sum and difference mode simultaneous excitation approach within the parallel-plate waveguide is explored, using a dual-mode planar horn with orthogonal port excitation. This approach is further implemented in dual reverse pillbox systems, combined with a magic-T and an E-plane divider, to realize a low-complexity monopulse array feed network with minimal components, thereby enabling broadband operation and high efficiency for the entire antenna. A prototype of the antenna has been fabricated and tested, with the measured results showing excellent agreement with simulations. The antenna operates over a bandwidth of 75-110 GHz (37.8%), with reflection coefficients of all three ports below -10 dB and isolation better than 30 dB. The measured gain of the sum beam ranges from 30.1 to 33 dBi, with an average total efficiencies of 63.4% across the entire operating band. Moreover, for the difference beam, the measured null depth is less than -35dB, and the amplitude imbalance is better than 0.2 dB. The proposed antenna combines broad bandwidth, high gain, and high efficiency with ease of fabrication and assembly, making it suitable for mm-wave and sub-THz tracking applications.