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This paper describes a pseudorandom carrier modulation scheme and its harmonic spectra spread effect. The pseudorandom carrier of the proposed scheme are produced through the random synthesis of the two triangular carriers, each of the same fixed frequency, but of opposite phase. The random selection of the two triangular carriers is decided by ``0'' or ``1'' states of the pseudorandom binary sequence (PRBS) random bits. Multiplexer which are used as random selector of the PRBS random bits, produces the resultant pseudorandom frequency carrier waveform. In order to verify the validity of the proposed method, the simulations and experiments were conducted and tested with a single-phase low-power H-bridge multilevel inverter. An EXAR XR2207 is used as a triangular carrier generator with fixed frequency, also an XR2206 is used for generation of single-phase sinusoidal wave. The PRBS random bits generator is implemented, using a shift register and an EXCLUSIVE OR gate. The experimental results show that the harmonics spectra of voltage and current are dispersed over a wide-band area by using the proposed scheme.
Date of Publication: April 2010