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.