A digitally controlled constant envelope phase-shift modulator for low-power broad-band wireless applications

A low-power constant envelope phase-shift modulator is presented. The circuit switches the phase of a constant amplitude carrier at output according to the input digital data. Design issues and their impact on the performance of the modulator are discussed. A test chip was fabricated in a 0.18-mum CMOS process. Experiment results verified the design principle of the modulator. The modulator consumes 2 mA and is suitable for low-power wireless applications like sensor network and personal area network. Since the circuit is implemented mostly by digital circuit, has broad-band frequency response, and supports high data rate, the modulator can be used at various wireless bands. The measured operating range of carrier frequency is 1.75 to 3.5 GHz, and the modulation data rate can go up to 500 Mb/s. In addition, the modulator can be modified to generate different modulations by digitally controlling both the phase and amplitude of the output signal from a phasor-combining circuit. Therefore, the modulator can potentially be used for software configurable radios