A novel balm based on an asymmetric coplanar waveguide with fuute gxouud plane (ASYCPWFGP) to coplanar strip (CPS) transition is presented. A xetum loss better than 16dB is obtained up to 5OGHz.丁he baluns are combined w2th four silicon Schottky barrier crossover diodes to yield a planar double- balanced mixer (DBM) which demonstrates an ultra-broadband performance up to 40GHz.