Pulse step modulator having faulted module detection and compensation

Abstract

A pulse step modulator (PSM) is presented herein for use in an AM transmitter. The modulator includes a plurality of unit step modules connected together in series with each module including a DC voltage source together with an associated actuatable switch for, when actuated, turning on the associated module to provide a unit step voltage. An output circuit is connected to the series connected modules for providing an output voltage to a load wherein the magnitude of the output voltage is equal to the sum of all of the voltage sources of the modules that are turned on. A plurality of module turn on signals are provided with each turn on signal serving to actuate one of the switches in one of the modules with the number of turn on signals being provided being dependent upon the magnitude of an input signal. A fault detector monitors the operation of the modules for fault conditions and provides for each module a first signal representing that the module has faulted in an on condition or a second signal representative that the module has faulted in an off condition. Circuitry is provided for varying the number of turn on signals dependent upon the fault conditions detected by the fault detector to compensate for any faulted modules.