A 400-MHz/900-MHz/2.4-GHz multi-band FSK transmitter in 0.18-μm CMOS

A multi-band FSK transmitter (Tx) is presented in this paper. The Tx is designed to operate at the ISM frequency bands at 433/868/915 MHz, 2.4 GHz, and MICS band at 402~405 MHz, and supports a data rate well over 1 Mbps. The Tx adopts an analog modulator which allows a deviation frequency ranging from 714 kHz to 3.2 MHz. In addition, this work proposes an inductor-less wideband mixer and a voltage-controlled oscillator to save the chip area. Fabricated in a 0.18-μm CMOS process, the proposed Tx consumes 8.9 mA to 12 mA from a 1.8-V supply voltage at different frequency bands. The measured FSK errors range from 13.9% to 15.4%, which are adequate for most low-cost wireless applications. The proposed multi-band Tx occupies an area of 1.6 mm × 1.9 mm.