Abstract
For some time now, millimetre-wave radar has been regarded as the ideal all-weather sensor for automotive collision avoidance systems. In order to make it affordable, many millimetre-wave component producers are exploring the possibility of producing fully integrated units using MMIC technology. So far, their efforts are based exclusively on a basic homodyne transceiver architecture, which is limited to operation in FMCW and FSK modes only. If two vector modulators are added to the existing architecture, it is possible to extend this capability to include the generation and detection of arbitrary phase-codes. Not only will this increase sensitivity and reduce susceptibility to interference, but it will allow the radar to be software adapted between modulation schemes without requiring any hardware reconfiguration. Software radar is an entirely new concept that offers an unprecedented level of flexibility and the potential for substantially improved transceiver performance. The key circuit in this novel software radar is a W-band monolithic I-Q vector modulator, based on passive reflection-type circuits. It is compact, flexible and fully integrable with other radar components. Moreover, it allows for the application of direct-conversion techniques, thus avoiding the need for bulky IF stages and costly RF image-rejection filters. A fully generalised theoretical analysis of three alternative vector modulator topologies is presented along with measured results for two example circuits operating at 77 GHz and 110 GHz. Adding vector modulators to the conventional radar architecture also provides a renewed incentive to reduce the size and improve the performance of existing RF front-end components. Consequently, a comprehensive investigation of radar MMICs is presented. This includes a review and design examples for millimetre-wave RF signal sources, active circulators, passive couplers, mixers and amplifiers. Finally, three multifunctional software radar chips are presented as evidence that the new architecture can be successfully implemented as a single MMIC.