Adaptive Interference Cancellation inNyquist Rate Scanned Arrays
R. Ekholdt · 1975
A conceptforadaptive directional filtering ina Nyquist rate scanned arraybased on time-domain sampling inthe arraysum channel ispresented. Bythismethodthe adaptation ratemay beindependent ofthescanratein contrast toarrayswithadaptive weight setting inthe arrayelement channels. Nyquist ratescanned receiver arrays havebeendescribed repeatedly intheliterature, themostwidely knownapplicationprobably being theMOSARsystem described byJohnson[1].Another example istheflood-lighting radar principle proposed byEdgar andJones[2], where this typeof array makespossible aradically newradar system which seems promising forsurveillance purposes, inparticular whenhigh data rates areneeded. Since these arrays consist ofseparate receivers foreachelement, theadaptive antenna techniques described byWidrow andothers [3] -[6]should beapplicable. Thehigh scanning rates involved, however, make adaptive weight andphase setting inthearray element channels difficult because these settings mustbeadjusted for eachbeamposition according tothedirectional distribution ofinterference. Toavoid this problem onemaytransfer thecancellation process fromtheelement channels tothearray sumchannel, where itmaybeperformed byadaptive filtering inthe timedomain. Since thearray scans ataratecorresponding tothesystem's information bandwidth, itsimply acts asatime-division multiplexer withregard tothedirectional variable, without limiting thepossibilities fordirectional filtering. Thebandlimitation requirement, which isessential inallsampled systems, ismetbyseparate matched filters ineacharray channel.