Circuits and systems for 77 GHz MMIC software radar.
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 arc 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 T- 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 frontend
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 multi-functional
software radar chips are presented as evidence that the new architecture can
be successfully implemented as a single MMlC.