A broad-band uniplanar branch-line coupler using a coupled rectangular slotline ring

A uniplanar branch-line coupler has been developed that provides substantially improved broadband amplitude and phase characteristics when compared to conventional microstrip branch-line couplers. Experimental results show that the new coupler has over 20-dB isolation over a bandwidth of more than 40% centered at 3 GHz with +or-1-dB power dividing balance.<
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