Low-Cost Microstrip-Line-Based Ferrite Phase Shifter Design for Phased Array Antenna Applications

Abstract

High-gain, electronically scanned phased array antennas are commonly used for radar and communications applications. These systems often require thousands of radiating elements, thousands of phase shifters, and hence, reduction in cost, size, and weight of the phase shifters are important goals in reducing the cost of the overall system. This letter presents a new ferrite phase shifter design based on microstrip-line technology that provides reduction in cost, size, and weight as compared to typical ferrite (analog) phase shifters. The design is based on the use of three microstrip lines arranged and fed with phase differences so as to produce circular polarization in the ferrite region. The proposed ferrite phase shifter was designed and simulated at 3 GHz to achieve a phase shift of approximately 360deg in less than an effective wavelength. A prototype was designed and fabricated to provide optimal circular polarization in the ferrite region and measured results show 309deg of phase shift in a wavelength, thus fulfilling the requirements. It is also shown that after calibrating measured values to account for the ratio between the applied external Ampere/turn values to the internally applied H-field value used in the high-frequency structure simulator (HFSS), good agreement may be seen between the simulation and experimental results. Based on this successful initial development, suggestions are made for further design improvements including reducing the number of turns in the biasing coil and minimizing the required input power