The efectiveness of an active power filter depends basically on three characteristics: a) the design characteristics of the PWM modulator, b) the method implemented to generate the reference template and c) the modulation method used. For the last characteristic there are many methods, most of them based on PWM strategies. In this paper, three of these methods, whose characteristics are their simplicity, are analyzed: Periodical Sampling Control, Hysteresis Band Control, and Triangular Carrier Control. These three methods have been tested with different waveform templates: sinusoidal, quasisquare and rectifier compensation current. The paper shows that, depending on the type of current the active filter has to follow, one strategy may be better than the others. The analysis is based on using the same switching frequency and the results are compared through a THD method which takes into account the particular shape of the waveform template. Simulations and experimental results are presented in the paper.
An acousto-optic (AO) correlator is being constructed that offers a small, lightweight solution to detecting and analyzing widebandwidth, spread-spectrum signals. The processor is being inserted into an existing electronic support measure (ESM) test-bed under the Defense Advanced Research Projects Agency (DARPA) Transition of Optical Processors into Systems (TOPS) program. The correlator has a processing bandwidth of 500 MHz and will be used to detect direct-sequence, phase-modulated signals, frequency-hopped signals, chirps, and impulses. A description of the processor is provided along with experimental results obtained from an interim developmental breadboard. Subsequent digital processing, which includes nonlinear detection and Fourier transformation, is used to determine center frequencies, bandwidths, and band shape. Theoretical descriptions of the post-processing are provided and simulation results are discussed.
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