Design of a Broadband Comparator Network at X-Band

This letter 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 degrees 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 degrees phase imbalance along the frequency band 5-10 GHz. The 90 degrees phase shifter has less than -10 dB S11 in addition to having less than 1.6 degrees phase error and 1.5 dB insertion loss within the frequency band 5-9.9 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 (voltage standing wave ratio (VSWR)<2) of the manufactured comparator is 61% and operates from 5.26 to 9.9 GHz. An 8 x 8 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 8 x 8 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.