A 900-MHz/1.8-GHz CMOS transmitter for dual-band applications

The design of a radio-frequency transmitter that can operate in two bands while employing a minimal number of external components entails many challenges at both the architecture and the circuit levels. This paper describes the design of a 900-MHz/1.8-GHz transmitter implemented in CMOS technology for dual-band applications. Configured as a two-step architecture, the circuit generates the first upconverted signal in quadrature form and subsequently performs single-sideband modulation to produce the output in two bands. Fabricated in a 0.6-/spl mu/m digital CMOS technology, the transmitter exhibits unwanted spurs 40 dB below the carrier while drawing 75 mW from a 3-V supply.