Abstract: A method of balancing the voltage of DC links in a cascaded multi-level converter (CMC) semiconductor circuit, including the steps of providing a plurality of H-bridge converters per phase in the CMC circuit and utilizing a three phase duty cycle value from the main controller to determine a normalized duty cycle value, a ceiling duty cycle value and a floor duty cycle value. The normalized duty cycle value and an output current of the CMC is used to determine the direction and polarity of a capacitor current, and utilizing the capacitor current to determine a plurality of output capacitor voltages. A voltage summation result and direction is obtained from a ceiling index pointer and a floor index pointer and the voltage summation result, direction from the ceiling index pointer and a floor index pointer are used to create a combined switching table for the H-bridge converters. A pulse width modulator is utilized to balance the voltage of the DC links and thereby eliminate DC-capacitor voltage imbalance.

Abstract: A phase-matched resonant waveguide modulator suitable for very high frequency modulation and applications such as FM laser spectroscopy is described. The width of a crystal modulator section of the waveguide is chosen so that the operating frequency is just above cut-off to achieve optical and RF phase velocity matching at high frequencies such as 10 GHz by virtue of the dispersion of the waveguide near cut-off. The waveguide contains air in opposite end sections so that those sections are below cut-off and the microwave is evanescent, with the result that the end sections preferably are open for ease of optical coupling to the waveguide.