Method of Controlling the Single-Ended Clock Bus Interference to the RF Bands

Abstract

The low-speed single-ended clock bus is widely used in automotive electronic control transmission, audio、 video transmission, phased array radar beam control transmission and other fields. It is used as the data synchronization clock of the SPI interface to realize the data synchronization transmission of multiple terminal nodes. In order to improve the transmission distance and multi-load driving capability of the clock bus, a non-linear switch driving circuit is usually used for signal buffer driving. After driving, the clock bus signal has a rich high-order harmonic spectrum and generates energy radiation. The electromagnetic radiation frequency band mainly covers the frequency band above 30MHz, and may reach or exceed the electromagnetic radiation index threshold required by the system, causing interference to radiation-sensitive equipment such as high-sensitivity receivers. The principle of high-order harmonic generation is that a clock signal similar to a square wave propagates in the medium in the form of a wave, and the rich multiple harmonics contained in its frequency spectrum radiate energy outward through the fringe field of the transmission line. This paper proposes a method of digital waveform generation, which effectively suppresses the radiation of higher harmonics by generating approximately linear clock signals. Simulation and experimental verification prove that this method can significantly reduce the synchronous serial data clock bus in a certain system. Harmonic radiation energy, in the high-order harmonic spectrum of the clock, noise peaks are effectively suppressed.