A 3-5 GHz FSK-UWB transmitter for wireless personal healthcare applications

A dual band frequency-shift keying (FSK) transmitter for low data rate, short range application, operating in the 3-5 GHz ultra-wideband is described in this paper. Chirped signal with FSK modulation enables direct conversion technique which simplifies the transceiver architecture. Two sub-band frequencies are used to encode the binary data employing chirped pulse generator. The front-end consists of an RF fast startup LCVCO, a ramp signal generator and a differential wideband resistive feedback power amplifier. All circuits are designed in 0.18 μm CMOS. The ramp generator produces linear rising ramp and can maintain a constant chirp range across PVT variation. The simulated chirp pulses show a V_ppof 0.26 V. The differential power amplifier achieves a P_-1dB of 4.4dBm. It realizes a flat gain of 10.27 ± 0.03 dB across the dual band spectrum and a NF less than 2dB. The transmitter maximum output power is in the -10.077 to -10.15dBm range. The ramp generator, the pulse generator and the power amplifier consume currents of 0.95 mA, 1.6 mA and 7.5 mA respectively. The simulated PSD at the output of the transmitter meets FCC spectral mask requirement and the 500 MHz bandwidth constrain. The transmitter achieves energy efficiency of 0.6 nJ/bit at a data rate up to 3.2 Mbps.