Quantization noise cancelation scheme for digital quadrature RF pulse encoding

Abstract

Quadrature type pulsed radio frequency (RF) signal encoding combined with class-S switched-mode power amplification (SMPA) constitute a potential solution for high efficiency RF transmitters. However, the digital center frequency adjustment for such encoding methods is limited by quantization noise folding. In this paper, a novel quantization noise cancelation scheme is proposed that in an ideal case suppresses the folding distortion components completely. In addition, a low complexity practical solution easily embedable in an existing modulator architecture is given. According to the measurement results, up to 7 dB improvement in signal-to-noise-and-distortion ratio was achieved over a total center frequency tuning range of 160 MHz using a 20 MHz LTE signal excitation.Index Terms-4G mobile communication, PWM, radio frequency power amplifiers, sigma delta modulation, software radio.

Analysis Predicted Location of Harmonic Distortion in RF Upconverter Structure

“…For a single carrier environment, an increase in offset frequency also increases the unwanted spectral components. More other literatures, Routsalainen et al in [7,8] showed that larger frequency offsets caused image noise to fold in-band. They investigated a solution using complex noise shaping filters to move the main noise null and suppressing the image noise [7] and then another solution by using a fractional delay in the feedback path [8].…”