an), Hai-Hui Zha and Hao Feng (Keysight CO., LTD, Shanghai), Lei Shi (Ceyear Techologies CO., LTD, Qingdao) for their helpful discussions. We also thank Professors Jianqing Shi and Qiang Lin for helping establishing the microwave easurement laboratory.
In this paper, the characteristics of a class of transmission lines which support spoof surface plasmon polaritons are investigated both numerically and experimentally. In order to provide the characteristic impedance of spoof surface plasmon polaritons for PCB designers, the equivalent circuit parameters of the microstrip line periodically structured on subwavelength scale are extracted with the numerical method. It is found that the equivalent circuit parameters significantly vary with frequency when the subwavelength periodic structure is introduced into the edge of the conventional microstrip line. The results of time-domain measurements show that spoof surface plasmon polaritons have remarkable advantage over conventional microstrip lines and can be directly used in actual high-speed circuits, which is helpful for eliminating the doubts whether the metamaterials can be directly used in actual circuits.
This paper proposed a kind of guard traces based on a subwavelength periodic structure to reduce the far-end crosstalk (FEXT) of parallel microstrip lines in the PCB. This technology can be used to improve the false triggering and signal transmitting capacity of a multiconductor transmission line circuit system. In order to explore the present novel guard trace effect on isolating electromagnetic interference (EMI), the frequency response of the mutual capacitance and mutual inductance of the overall circuit system was provided and an equivalent circuit model was built. In comparison to the conventional microstrip line for isolating the EMI between parallel microstrip lines, the novel guard trace can efficiently reduce the mutual capacitance and mutual inductance of the overall circuit system. Thus, it is favorable for suppressing the crosstalk between microstrip lines. The S-parameters calculation result showed that this kind of subwavelength periodic microstrip guard trace can isolate the EMI between two microstrip lines more effectively. Particularly, the conventional grounded guard trace needs a lot of dense grounded holes, which severely influences the wiring design of various layers of a multilayer circuit board. However, the proposed guard trace requires only one grounded hole, which has little influence on the circuit wiring of each layer of a multilayer printed circuit board. In our experiment, the step function signal of 30 ps rise time was imported into one microstrip line to measure the FEXT of the other microstrip line. It was demonstrated by the measurement result that the subwavelength periodic microstrip guard trace can reduce the FEXT to be below 5% of the transmission signal amplitude and is more flexible in practice. In compliance with the actual demand for a high-speed circuit, three isolation structures were proposed, and their isolation effects on the electromagnetic coupling between microstrip lines were verified individually.INDEX TERMS Multiconductor transmission lines, crosstalk, guard trace.
It has been proved that a subwavelength periodic microstrip structure can be used to suppress crosstalk between two adjacent microstrip lines and such a microstrip structure can be widely used in the application of high‐speed circuit systems. To further increase the accuracy of the equivalent circuit model of the subwavelength periodic microstrip line (SPML), we focus our attention on a single unit cell with the periodic structure, which is divided into several sub‐regions, and the circuit parameters in each sub‐region are analysed for setting up a complete circuit model of the unit cells. Then the details of the interaction between each sub‐region and the electromagnetic field are clearly indicated. The S $S$‐parameters of the circuit model accord well with full‐wave simulation results, showing a maximum deviation of 0.03973 dB for S21 and 0.1211 dB for S11 below 15 GHz. For the first time, we also study the frequency‐dependence of the mutual capacitance and the mutual inductance for analysing the coupling effect between an SPML and a conventional microstrip line (CML). The instantaneous impedance obtained by the full‐wave simulation of the SPML is consistent well with the experimental results.
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