Millimeter-wave monolithic balanced BPSK modulator using a miniaturised backward-wave coupler

A miniature parallel-coupled microstrip coupler has been realised at millimeter-wave frequency using capacitor compensation at the ends. The coupler has been used in a very compact BPSK modulator as an example of application. The balanced modulator employs reflection-type topology and measures 0.7/spl times/0.9 mm excluding RF-on-wafer probe pads.