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 microwavefrequencies 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 midrange FPGA technology. Â© 2008 IEEE.