An FSK demodulator for Bluetooth applications having no external components

An injection-locked oscillator in combination with a phase detector is shown to make a very effective frequency-shift keying (FSK) demodulator for Bluetooth applications. The dynamic behavior allows automatic tuning from outside the locking range. Two tuning methods are described which eliminate the need for external components, allow fast tuning and can handle low-frequency data. A cancellation technique is used which minimizes filtering requirements. The demodulator was fabricated in a bi-complementary metal-oxide-semiconductor (BiCMOS) technology with L_eff = 0.25 μm. The die area was 0.09 mm² and the current consumption was 0.8 mA with a supply voltage of 2.8 V.