Cyclostationary characterization of electromagnetic interference with spread spectrum clocking

Spread spectrum clocking (SSC) is used for data transmission in modern synchronous digital systems in order to comply with electromagnetic compatibility (E MC) regulations. In a synchronous digital system, a single clock signal is delivered to all subsystems, where actions within each subsystem only occur during the clock periods (Kao and Hsieh, 2009; Kawamoto et al., 2014). Due to the periodic nature of a clock signal, its bandwidth is very narrow. In an ideal rect angular clock signal, in fact all the signal energy is concentrated at a single frequency and the higher order harmonics. Radiated electromagnetic interference (EMI) originating from clock signals ther efore also radiates all it s energy at a very narrow frequency band. The peak radiation power in such a scenario can easily reach the limits defined by EMC regulations. When measuring the near-field emissions from th e PCB under test, the existence of the spreading spectrum effects need to be taken into account for correct signal processing of the measured time domain data. It is known that data containing emissions reveal the cyclostationary properti es of their second-order stochastic characteristics. But in the case of SSC the cyclic frequencies of the correlation functions become dependent on time lag, which in the case of time-continuous functions could be described by a Generalized Almost Cyclostationary model (Russer et al., 2015a, b). But after the uniform discretization the stochastic process could loose the properties of the continuous one. The possible way for overcome this problem is the de-spreading of the clock signa l at the preprocessing stage of the algorithm for revealing cyclostationary properti es of the measured EMI data. The comparison of the modeling and measurement results shows the good agreement between the characteristics of the composed model for the SSC signal and corresponding c haracteristics evaluated from the near-field measurements of the EMI from t he Spartan 6 FPGA electroni c device. The proposed model can be used for the prediction of spectral characteristic of any m easured and approximated frequency modulation function using for the implementation of the SSC. It can be also effectively used for the necessary de-spreading procedure of t he measured near-field time domain EMI data. Kao, Y. H. and Hsieh, Y. B.: A Low-Power and Hi gh-Precision Spread Spectrum Clock Generator for Serial Advanced Technology Attachment Applicatio ns Using Two-Point Modula tion, IEEE Transactions on Electromagnetic Compatibility, 51, 245- 254, doi:10.1109/TEMC.2008.2012115, 2009. Kawamoto, T., Suzuki, M., and Noto, T.: 1.9-ps Jitte r, 10.0-dBm-EMI Reduction Spread-Spectrum Clock Generator With Autoca libration VCO Technique for Serial-ATA Application, IEEE Tr ansactions on Very Large Scale Integration (VLSI) Systems, 22, 1118-1126, doi:10.1109/TVLSI.2013.2257901, 2014. Russer, J. A., Russer, P., Konovalyuk, M., Gorbuno va, A., Baev, A., and Kuznetsov, Y.: Analysis of Cyclostationary Stochastic Electromagnetic Fields, in: International Conference on Electromagnetics in Advanced Applications (ICEAA) , 2015, pp. 1452-1455, IEEE, 2015a. Russer, J. A., Russer, P., Konovalyuky, M., Gorbuno va, A., Baev, A., and Kuznetsov, Y.: Near-Field Propagation of Cyclostationary Stochastic Electrom agnetic Fields, in: International Conference on Electromagnetics in Advanced Applic ations (ICEAA), 2015, pp. 1456-1459, IEEE, 2015b.      «

Spread spectrum clocking (SSC) is used for data transmission in modern synchronous digital systems in order to comply with electromagnetic compatibility (E MC) regulations. In a synchronous digital system, a single clock signal is delivered to all subsystems, where actions within each subsystem only occur during the clock periods (Kao and Hsieh, 2009; Kawamoto et al., 2014). Due to the periodic nature of a clock signal, its bandwidth is very narrow. In an i...     »