W-band waveguide-packaged InP HEMT reflection grid amplifier

This letter presents a 79-GHz broadband reflection-type grid amplifier using spatial power combining to combine the power of 64 unit cells. Each unit cell uses a two-stage cascade configuration with InP HEMTs arranged as a differential pair. A broadband orthogonal mode transducer (OMT) separates two orthogonally polarized input and output signals over a 75 to 85 GHz range. In conjunction with the OMT, a mode converter with quadruple-ridged apertures was designed to enhance the field uniformity over the active grid. Measurements show 5-dB small signal gain at 79 GHz and an 800-MHz 3-dB bandwidth. The amplifier generates an output power of 264 mW with little evidence of saturation.