Compact microstrip parallel coupler with high isolation

A compact microstrip parallel coupler with high isolation is presented. Adopting the reflected power canceller approach, the developed coupler with dual transmission lines not only effectively enhances the directivity of the coupler, but also has compact size. For verification purposes, a proposed parallel coupler is fabricated and measured at 915 MHz. The proposed parallel coupler can obtain excellent isolation of -65 dB and directivity of -47.7 dB at 915 MHz. Simulated results are in good agreement with measured results, which verified the reliability of the designed coupler.