Reconfigurable Class S power amplifiers at RF and microwave frequencies

Abstract

Abstract-When a delta-sigma modulator (DSM) is placed before a class D switching stage the combination can be used to amplify time varying envelope signals. However a bandpass DSM is commonly employed and is required to have a sampling frequency approximately four times the carrier frequency. At RF or microwave frequencies proprietary hardware was previously needed to implement the DSM. However, it is shown here in simulation and from experimental measurement that a suitable DSM for class S power amplifiers can be implemented at RF and microwave frequencies using mid-range FPGA technology.

FPGA SerDes Capability as Switch mode PA Modulator

“…The shape of the spectral output of the SDM characterizes the system as either Low pass, Band pass or High pass. Previous papers have demonstrated the operation of modulator structures in FPGA logic such as [4][5][6]. In these papers it can be seen that there is a loss of dynamic range when comparing simulation results with measurements.…”

Reconfigurable high frequency class S power amplifier demonstrator

“…This requires a high frequency circuit to pre-process the signal and split it into two separate paths. The class S PA is similar as it requires pre-processing of the signal using pulse-density modulation [10]. Shown in this publication, the signal into the class S PA is a high resolution digital signal at a fraction of the carrier frequency.…”

Pulse width modulation of multilevel delta-sigma output for class S power amplifier

“…Digital multiplication of the delta-sigma modulator with a binary signal at twice the desired carrier frequency is an interesting case of the previous technique [7]. Binary multiplication is a single bit operation and easy to implement.…”