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

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.