Reconfigurable fully digital transmitter with carrier-frequency pulse-width modulation

A reconfigurable fully digital transmitter with carrier-frequency (CF) pulse-width modulation (PWM) is implemented in 180 nm CMOS for low CF applications. Through delay lines, baseband phases are mapped to position delays of 1/4 period of a carrier clock. With delay lines based CF PWM, pre-corrected baseband envelopes are converted to pulse-widths of the position-modulated carrier clock. Both the pulse-widths and the positions of the modulated carrier clock are amplified and reshaped to the sine-wave carrier with baseband components by the sequent switched-mode power amplifier and a bandpass filter. The circuit-level simulation results verify that the proposed implementation achieves reconfigurable CF and 20 dB spectrum optimisation, when compared with the existing intermediate- frequency PWM based designs.