Using high pass sigma-delta modulation for Class-S power amplifiers

Abstract

Switching power amplifiers offer the potential for superior efficiencies if used at radio frequencies. However many existing bandpass architectures require a switching frequency four times that of the signal, making implementation difficult. In this paper we propose to use a high-pass sigma-delta modulator to reduce the switching rate to only twice of the signal. We will present a solution to the problem of the reflected image and demonstrate it's viability for use in mobile telephony.

A GUI driven Σ-Δ modulator design, evaluation and measurement tool with a view to practical implementation

“…The resulting SNR values for OSRs of 32 and 256 are 41 dB and 65dB respectively, which shows a good agreement with the reported results in the literature [8], [9].…”

“…In addition, this tool has been developed to design High-Pass (HP) based Σ−Δ modulators for the applications reported in [8]. The creation of a Graphical User Interface (GUI) driven design, evaluation and measurement tool for HP Σ−Δ modulators has not been previously reported in the literature to the best knowledge of the author.…”

Lowpass delta-sigma modulator with digital upconversion for switching-mode power amplifiers

“…Thus, this topology is not well suited for gigahertz applications due to high speed requirements leading to significant power consumption. Also highpass ∆ΣM needs operation frequencies which are at least twice as high as the desired carrier frequency [6]. In contrast to this lowpass ∆ΣM (LP∆ΣM) can operate with frequencies lower than the carrier frequency.…”

System architecture of an all-digital GHz transmitter using pulse-width/position-modulation for switching-mode PAs

“…Bandpass ∆ΣM needs oversampling frequencies above the carrier frequency [3] and multiple switching operations during one RF cycle. Also highpass ∆ΣM needs sample rates which are at least twice the carrier frequency and require highly selective filters [4]. Lowpass ∆ΣM leads to high out-of-band noise due to the low oversampling -especially for larger bandwidths [5].…”