A programmable variable waveshape generator for electrosurgical research

A variable waveform electrosurgical unit (VWESU) was designed and used for electrosurgical research. The design criteria included the ability to modulate the amplitude of a sinusoidal carrier on a cycle-by-cycle basis, output power equivalent to commercial generators, and provision for varying the output impedance. These were realized with a microprocessor-controlled variable waveform generator which allows the user to program waveforms into memory with a set of simple descriptive commands, a linear power amplifier, and a custom output transformer. The contents of the memory are directly pipelined to a set of analog switches, which modulate the radio-frequency carrier with one of eight amplitude levels, thereby bypassing the speed limitations of the microprocessor.