Abstract-Frequency modulation (FM) and random switching methods have been used for reducing conducted electromagnetic interference (EMI) in power converters. Limited theoretical studies and comparisons of these schemes, however, are available. In this paper, a detailed analysis and the spectral characteristics of a random carrier-frequency (RCF) technique for suppressing conducted EMI in an offline switched-mode power supply are presented. The analysis provides a theoretical platform for studying the characteristics of this random switching scheme. The level of randomness is defined for the RCF scheme and varied in the converter example so that its effects on the power spectra can be demonstrated. Theoretical predictions of the spectral characteristics of this scheme are confirmed with measurements. The RCF scheme has been compared with the standard constant-frequency pulsewidth modulation (PWM) scheme and the FM scheme. Comparisons of their spectral performance show that the RCF scheme has better conducted EMI suppression than the FM and standard PWM schemes.

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The noise power estimation for pulsed interference detection in global navigation satellite system (GNSS) receivers is considered. Previous effective consecutive mean excision (CME) related algorithms in this area work in an inter-block iterative fashion and the convergent process is usually quite time-consuming and needs a large storage space. A block-flow manner based on the backward CME (BCME) algorithm to overcome these problems is proposed. Numerical results show that the method decreases the computation and storage requirements of BCME, and possesses closer convergence properties.