A Subharmonic Super-Regenerative FMCW Radar With Improved Intermodulation Efficiency for Applications Beyond Cut-Off Frequency

Thisarticlepresentsanovelsubharmonicsuper-regenerative receiver (SHSRR) radar for high-sensitivityand low-noise operation in beyond-fmaxfrequency-modulatedcontinuouswave(FMCW)applications.Incontrasttoconventional super-regenerative designs, the proposed conceptis extended by an inherently implemented, subharmonicdownconversion. This downconversion allows a tripling of bothoperation frequency and bandwidth and thereby enables thesystem's operation beyond its gain limit. Operated with the novelSHSRR, the maximum operating frequency and bandwidth ofFMCW transceivers is proven to be significantly increased. Withlocal oscillator (LO) power requirements considerably reducedcompared with passive mixer approaches, the concept is alsosuited for massive multichannel scaling. Optimized modulationsignals are applied to the SHSRR concept, which intentionallyboost the receiver's nonlinearity and thus substantially improvepreviously achieved intermodulation efficiencies for the firsttime. The concept is verified experimentally with a 24-GHzFMCW radar transceiver implemented in planar microstriptechnology. Due to the introduced optimization approach,extremely high sensitivity levels of well below-114 dBmhave been accomplished, whereby the previously achievednoise figure is improved from almost 30 dB down to 11 dB.Power consumption was limited to 9 mW. This simple, novelconcept is thus suitable for scaling to integrated circuits witha high number of receive channels at several 100-GHz carrier frequencies.