Frequency modulated imaging radar using distributed frequency swept antennas

Abstract

In this work a novel approach to collision avoidance radar is presented. Leveraging the chipsets currently in development for the automotive industry, with an operational band of 77 to 81 GHz a new frontend has been developed using a distributed frequency swept antenna. The frequency swept antenna is able to steer the beam based on the transmit frequency. Multiple sub-array elements are distributed across the bumper of a vehicle increasing the aperture size of the system for improved beam resolution, thereby leading to better system sensitivity. To this end, system modeling was implemented to study the tradeoff between system sensitivity or range and power, gain, antenna aperture size and number of sub-array elements. The sub-arrays were designed, optimized, manufactured, and characterized using a conformal, flexible, low loss high frequency Rogers 3003 material. The measured far field patterns of the developed antenna array demonstrated consistent angular steering characteristics of -4° to 8° over the frequency from 75 to 85GHz with minimum reflection. The developed sub-array elements are cascaded and then synchronized using electronically controlled, high resolution, wideband, low loss W-band phase shifters. To drive such a large distributed array, we also focused on the development of high-resolution or analog phase shifters with 360 degrees coverage from 77-81GHz. The phase shifter chip was designed based on three-vector method and manufactured by leveraging SiGe foundry run. RF integration of the fabricated chips along with the control circuit was also conducted to demonstrate fully phase control over the band of interest. The packaged antenna subarrays and phase shifters are integrated together to form a distributed array. Through synchronization, coherent operation of the system can be established, enhancing the angular resolution of the system. The developed antenna array will be integrated with a Frequency Modulated Continuous Wave (FMCW) transceiver for applications of automobile radars.