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To go further into integration and to understand parasitic coupling mechanisms in RF integrated circuits, this article describes an RF front-end direct conversion receiver co-integrated with a differential power amplifier (PA). It uses dedicated filtering functions based on bulk acoustic wave (BAW) technology. This circuit performs a prototype of complete transceiver which has been designed to address WCDMA FDD standard. It is realized in a 0.25 mum BiCMOS technology from STMicroelectronics using SiGe-C heterojunction bipolar transistors (HBT) and NLDEMOS transistors. BAW inter-stage filter and reject-cell are designed to improve isolation between transmission and reception bands by reducing coupling mechanisms between transmitter (TX) PA and receiver (RX) path. This circuit has been assembled and tested, RX chain gain is measured to be equal to 24 dB and it has more than 40 dB TX leakage attenuation at intermediate frequency (D7) mixer output under a 2.7 V voltage supply. Differential PA with BAW reject filter delivers up to 28 dBm linear output power.
Date of Conference: 23-25 Jan. 2008