This paper presents an UWB antenna diplexer chip fabricated using high quality passive and active Si-Cu (P7MI) technology. This antenna diplexer has three functions, the main function is filtering for two band groups, the second function is matching between two impedance levels and the third function is differential to single ended mode conversion. This chip together with multichip packaging module technique enables a dual band group WiMedia UWB radio on full silicon RFIC. The diplexer is based on two 6th order elliptic filters. The simulated diplexer has an insertion loss of 3.5 dB in both bands and common mode suppression of around 15 dB for the low band and around 20 dB for the high band. The chip size is 1.65 mm times 1.65 mm.