Design of a Broadband Comparator Network at $X$-Band

Abstract

This paper presents a novel broadband comparator network design operating at X-band. A multilayer aperture coupling scheme and shielding around the microstrip structures are utilized to achieve broadband performance. There are two main building blocks of the proposed comparator network. These are a quadrature hybrid coupler and a 90-degree phase shifter. These two main components are designed to have broadband performance so that the designed comparator would also have wideband performance. The proposed quadrature hybrid coupler achieves more than 19.7 dB return loss, a 0.75 dB amplitude imbalance, and 1.4 ° phase imbalance along the frequency band 5 GHz to 10 GHz. The 90-deg. phase shifter has less than -10 dB S11 in addition to having less than 1.6 °. phase error and 1.5 dB insertion loss within the frequency band 5 GHz to 9.9 GHz. The proposed comparator is acquired by combining the multiple quadrature hybrid couplers and phase shifters. The results of the manufactured and simulated comparator agree well with each other. The impedance bandwidth (VSWR<2) of the manufactured comparator is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> 61 and operates from 5.26 GHz to 9.9 GHz. An 8x8 microstrip patch antenna array is designed and manufactured to verify the comparator network's sum and diff pattern forming capability. The far-field measurements of the proposed comparator combined with the 8x8 antenna array indicate that 36 dB null depth is acquired at the azimuth plane, and 40 dB null depth is achieved at the elevation plane.