The GRINSIW based directional coupler has a bandpass filtering response. The stop band rejection beyond the right cut-off frequency is low. The value of the stop band rejection beyond the right cut-off frequency is around 8 dB. Hence in order to improve stop-band rejection, complementary split ring resonators (CSRRs) are introduced in the ground plane of the GRINSIW based directional coupler. The complementary split ring resonators (CSRRs) are the dual equivalent of the SRRs. The equivalent circuit for a CSRR is constituted by a tank circuit (or) a LC circuit. When CSRRs are etched in the ground plane of the GRINSIW directional coupler, a bandstop response at the resonant frequency of the CSRR is achieved. Hence multiple CSRRs with resonant frequencies higher than the right cuto® frequency are etched in the ground plane of the feeding arms of the GRINSIW directional coupler. This technique leads to a overall bandpass filtering response for the directional coupler with a high stopband rejection of better than 20 dB.