A High Precision/High Isolation Planar MM-Wave PSK/AM Modulator

A new approach to broadband mm-wave binary PSK/AM modulators is proposed using a double balanced configuration of 4 PIN diodes in a waveguide-coupled stripline circuit. The transition from two in-line orthogonal waveguides to four single-ended 180° reflection modulators is realized as a planar power divider/combiner structure in a plane transverse to the waveguide axis. Three states are available: 0°/180° transmission and an isolated state. The design allows individual matching and biasing of the diodes. The phase error is less then ±2°, amplitude imbalance below 0.3 dB. More than 30 dB isolation and 15 dB reflection loss are maintained over a 25% bandwidth in W-band.