Research on Automatic Measurement of Impulse Magnetic Noise (VI) : Malfunction of Digital Circuit Caused by Electromagnetic Noise(B.Article,Special Edition for the 20th Anniversary of the University)

A jitter on a digital signal is one of the causes for malfunctions of digital circuit. It is thought that this jitter is generated by many kinds of noises. We designed a digital board which was composed of high speed CMOS logic ICs and exposed on it the external electromagnetic noises from an antenna. By the measurement of the frequency characteristics of a jitter appeared by it, the relations between the jitter and the appearance of a malfunction on a circuit is examined. An electromagnetic wave has a sinusoidal waveform and its frequency is changed between the range of 20 to 200 MHz. As the results, it is found that the jitter has a few maximum and minimum values among the variation of electromagnetic frequency, and malfunction of the measured circuit appears on the discontinuous magnetic wave bands of the vicinity of the maximum values of the jitter