The HMC555 is a compact I/Q MMIC mixer which can be used as either an Image Reject Mixer or a Single Sideband Upconverter. The chip utilizes two double balanced mixer cells and a 90 degree hybrid fabricated in a GaAs MESFET process. All data shown below is taken with the chip mounted in a 50 Ohm test fixture and includes the effects of 1 mil diameter x 12 mil length bond wires on each port. A low frequency quadrature hybrid was used to produce a 100 MHz USB IF output. This compact mixer is a much more compact alternative to hybrid style Image Reject Mixers and Single Sideband Upconverter assemblies, and is ideal for microwave radio applications. The redundant IF port connections located on opposing sides of the HMC555 chip, provide added layout flexibility.