▁The ▁wave ▁guide ▁contains ▁sl its ▁with ▁size ▁of ▁about ▁ 1 / 4 ▁w avel ength , ▁in ▁a ▁distance ▁of ▁ 1 / 2 ▁w avel ength . ▁ ▁History ▁The ▁slot ▁anten na ▁was ▁invent ed ▁in ▁ 1 9 3 8 ▁by ▁Alan ▁Bl um lein , ▁while ▁working ▁for ▁E MI . ▁He ▁invent ed ▁it ▁in ▁order ▁to ▁produce ▁a ▁practical ▁type ▁of ▁anten na ▁for ▁V H F ▁television ▁broadcast ing ▁that ▁would ▁have ▁horizontal ▁polar ization , ▁an ▁om n id irection al ▁horizontal ▁radiation ▁pattern ▁and ▁a ▁narrow ▁vertical ▁radiation ▁pattern . ▁ ▁Prior ▁to ▁its ▁use ▁in ▁surface ▁search ▁rad ar , ▁such ▁systems ▁used ▁a ▁par abol ic ▁segment ▁reflect or . ▁The ▁sl otted ▁wave guide ▁anten na ▁was ▁the ▁result ▁of ▁collabor ative ▁rad ar ▁research ▁carried ▁on ▁by ▁McG ill ▁University ▁and ▁the ▁National ▁Research ▁Council ▁of ▁Canada ▁during ▁World ▁War ▁II . ▁The ▁co - in vent ors , ▁W . H . ▁Watson ▁and ▁E . W . ▁Gu pt ill ▁of ▁McG ill , ▁were ▁granted ▁a ▁United ▁States ▁pat ent ▁for ▁the ▁device , ▁described ▁as ▁a ▁" direct ive ▁anten na ▁for ▁mic row aves ", ▁in ▁ 1 9 5 1 . ▁ ▁Similar ▁techn ologies ▁For ▁comparison , ▁in ▁the ▁par abol ic ▁type ▁of ▁anten na ▁a ▁feed horn ▁at ▁the ▁end ▁of ▁a ▁wave guide ▁direct s ▁a ▁con ical ▁beam ▁of ▁output ▁energy ▁toward ▁the ▁reflect or , ▁wh