US Patent 7027795 Low temperature co-fired ceramic double balanced mixer

A double balanced mixer with improved isolation between the LO and RF frequency signals. The mixer has a local oscillator balun, an intermediate frequency balun and an RF balun. The baluns are located on inner layers of a substrate comprised of low temperature co-fired ceramic. The baluns are formed from spiral lines that form windings. The windings are coupled between adjacent layers. The local oscillator balun is connected to the intermediate frequency balun. A diode ring is connected between the RF balun and the intermediate frequency balun. The diode ring is mounted to a top layer. Several vias extend through the substrate. The vias provide an electrical connection between the baluns and the diode ring.