Abstract
The carrier-frequency (CF) and intermediate-frequency (IF) pulse-width modulators (PWMs) based on delay lines are proposed, where baseband signals are conveyed by both positions and pulse widths or densities of the carrier clock. By combining IF-PWM and precorrected CF-PWM, a fully digital transmitter with unit-delay autocalibration is implemented in 180 nm CMOS for high reconfiguration. The proposed architecture achieves wide CF range of 2 M–1 GHz, high power efficiency of 70%, and low error vector magnitude (EVM) of 3%, with spectrum purity of 20 dB optimized in comparison to the existing designs.
Highlights
Wireless communication is becoming more and more important and ubiquitous in modern society
Under low CF band, the transmitter working in mode “1” and CF-pulse-width modulators (PWMs) enabling, multibit phase component Φ is mapped to 1/4-period position of the carrier clock, and multibit envelope component A is converted to precorrected pulse width of the carrier clock
The proposed fully digital transmitter is designed in 180 nm CMOS with external class-D power amplifier (PA) and band-pass filter (BPF)
Summary
Wireless communication is becoming more and more important and ubiquitous in modern society. The existing design [1, 2], employing all-digital phaselocked loop (ADPLL) and delta-sigma modulator, introduces large fractional spurs and requires strict energy match between power branches. The existing architecture [9] employing outphasing amplification technique is not widely used in commerce due to strict matching requirements between dual paths and distortion and efficiency degradation caused by RF power combiner. Delay-line based CF-PWM with precorrection logic is proposed, where the only carrier clock is employed to ensure spectrum purity under low CF conditions. By combining IF-PWM for high CF and precorrected CF-PWM for low CF, a fully digital transmitter is presented with wide CF range and high efficiency. A unitdelay autocalibration loop for delay lines is proposed with reconfigurable carrier frequency fC
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