Transmitter, receiver antennas and sensors monolithically integrated with CMOS LSIs are strongly demanded as a means of reducing the cost of wireless equipment. As the first step, an RF front- end (low-noise-amplifier [LNA] and mixer) is designed for use in the 7-GHz band corresponding to multi-band OFDM UWB group3 spectrum allocation. We clarify the design methodology of antennas on lossy Si substrates. The RF front-end with the antenna was fabricated using a 0.18-mum CMOS process. Measured conversion gain with 60-cm air interface is about -50 dB in the above band.