A CMOS 434/868 MHz FSK/OOK transmitter with integrated fractional-N PLL

A 434/868 MHz FSK/OOK transmitter with integrated PLL is reported. Direct digital modulation of a fully integrated Σ-Δ fractional-N PLL frequency synthesizer is used to ensure fine frequency resolution and low phase noise. A wideband VCO together with an Adaptive Frequency Calibration (AFC) is used to cover the desired bands. A differential-to-single output programmable power amplifier is integrated to make the chip low cost and low power. The measurement results show that the phase noise are -76dBc/Hz and -131dBc/Hz at 10-kHz offset and 3-MHz offset with carrier centered at 868 MHz, respectively. The peak output power of the transmitter is 3.5dBm on 50-Ω load and the measured adjacent channel power ratio (ACPR) for 100 kHz channel is less than -50-dBc. The chip is fabricated with 0.35-μm RF CMOS process. The 2-mm² transmitter IC including PLL and power amplifier (PA) consumes 87.6mW at 3V voltage supply.