An analog GFSK modulator in 0.35-μm CMOS

An analog Gaussian frequency shift keying (GFSK) modulator designed in 0.35-μm CMOS consumes 600 μA from a 3-V supply and realizes an analog implementation of the FM differential equation. The modulator operates at baseband and is intended for use in a direct-conversion Bluetooth transmitter. It achieves a frequency deviation of 160 kHz with better than ±3% accuracy. The modulator implements an amplitude control loop to achieve a well-defined output swing. The total output harmonic distortion is less than 1%.