A 2.4 GHz Wideband Open-Loop GFSK Transmitter With Phase Quantization Noise Cancellation

A wide-bandwidth phase modulation transmitter with phase quantization noise cancellation technique is proposed. Unlike conventional phase-locked loop closed-loop modulation, very wide-bandwidth arbitrary phase modulation can be synthesized at the phase-locked loop output by selecting the desired phases that are generated by a phase generator. To further reduce the phase quantization noise due to the finite number of available phases, a phase quantization noise cancellation path is proposed through a second VCO control port. At least 7 dB phase noise cancellation was demonstrated using a prototype 0.18 μm CMOS 2.4 GHz GFSK transmitter integrated circuit. Measurements on the prototype show that out-of-band phase quantization noise is 49 dB lower than the signal when transmitting 20 Mb/s GFSK signal and that the rms error is only 3.2%. The current consumption is 34.5 mA excluding the transmitter output buffer.