A single-chip CMOS direct-conversion transceiver for 900 MHz spread-spectrum digital cordless phones

This fully-integrated transceiver incorporates RF circuits, synthesizer, baseband filters, demodulator, and digital signal processing. The few off-chip components include an ISM band filter, a balun, an RF matching network, an RC loop filter for the PLL, a crystal resonator, and a resistor for biasing. A transmit/ receive (T/R) switch is avoided by sharing a single RF port between transmitter and receiver. An offset cancellation method attenuates offsets in the baseband without sacrificing bandwidth in the direct conversion receiver. Careful circuit design, timing, and layout considerations provide isolation between the sensitive RF signals and the digital switching noise. The IC is in 0.6/spl mu/m CMOS and provides a complete interface between antenna and voiceband codec.