In this paper, a periodic interdigital structure for wideband mitigation of differential-to-common mode conversion at the bend discontinuity of differential lines is proposed. A hybrid inductance and capacitance compensation property is exhibited to suppress the common-mode noise of asymmetric transmission lines. An equivalent circuit model is given to explain the working principle of the presented periodic interdigital structure for differential pairs. In comparison with the traditional methods, steep and wideband suppression performances are both observed with the proposed design. Moreover, no additional area is required at the bend discontinuity for compensation. From the measured result, the differential-to-common mode conversion of the differential signals can be mitigated from DC to 10 GHz with a rejection level of -20 dB. The measurements agree well with the simulation predictions.
2. Guo, W.-D., G.-H. Shiue, C.-M. Lin, and R.-B. Wu, "Comparisons between serpentine and flat spiral delay lines on transient reflection/transmission waveforms and eye diagrams," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 4, 1379-1387, Apr. 2006.
3. Tsai, C.-H. and T.-L. Wu, "A broadband and miniaturized common-mode filter for gigahertz differential signals based on negative permittivity metamaterials," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 1, 195-202, Jan. 2010.
4. Wu, L.-S., J.-F. Mao, and W.-Y. Yin, "Slow-wave structure to suppress diffetential-to-common model conversion for bend discontinuity of differential signaling," Proc. IEEE Elect. Design Adv. Packag. Syst. Symp., Hangzhou, China, Dec. 2011.
5. Lin, D.-B., "Signal integrity of bent differential transmission lines," Electron. Lett., Vol. 40, No. 19, 1191-1192, Sep. 2004.
6. Chang, C.-H., R.-Y. Fang, and C.-L. Wang, "Bended differential transmission line using compensation inductance for common-mode noise suppression," IEEE Trans. Compon. Packag. Manuf. Technol., Vol. 2, No. 9, 1518-1525, Sep. 2012.
7. Shiue, G.-H., W.-D. Guo, C.-M. Lin, and R.-B. Wu, "Noise reduction using compensation capacitance for bend discontinuities of differential transmission lines," IEEE Trans. Adv. Packag., Vol. 29, No. 3, 560-569, 2006.
8. Ranade, S. R., R. K. Shevgaonkar, A. Sidhique, and P. H. Rao, "Mitigation of common mode noise in bent differential transmission line using curved PBG unit cell," Microw. Opt. Technol. Lett., Vol. 60, No. 2, 347-352, 2018.
9. Zhu, H.-R., J.-J. Li, and J.-F. Mao, "Ultra-wideband suppression of SSN using localized topology with CSRRs and embedded capacitance in high-speed circuits," IEEE Trans. on Microw. Theory and Tech., Vol. 61, No. 2, 764-772, 2013.
10. Duffy, A. P., A. J. M. Martin, A. Orlandi, G. Antonini, T. M. Benson, and M. S.Woolfson, "Feature selective salidation (FSV) for validation of computational electromagnetics (CEM). Part I — The FSV method," IEEE Trans. Electromagn. Compat., Vol. 48, No. 3, 449-459, 2006.
11. Orlandi, A., A. P. Duffy, B. Archambeault, G. Antonini, D. E. Coleby, and S. Connor, "Feature selective validation (FSV) for validation of computational electromagnetics (CEM). Part II — Assessment of FSV performance," IEEE Trans. Electromagn. Compat., Vol. 48, No. 3, 460-467, 2006.