Ultra-compact on-chip spoof surface plasmon polariton transmission lines with enhanced field confinements

On-chip transmission lines (TLs) for spoof surface plasmon polariton (SSPPs) have been proved to suppress on-chip channel crosstalk in terahertz band due to their field confinement property. But the contradiction between strong field confinement and miniaturization limits the application of the on-chip SSPP TLs in millimeter and terahertz bands. Here, an ultra-compact on-chip SSPP TL with strong field confinement is proposed using 0.18 mu m CMOS technology. The proposed SSPP TL reduces the cutoff frequency down to 435 GHz in a very limited TL width. Broadband feeding without using gradient transition structures is presented to guarantee the compact size. Compared to microstrip and the typical SSPP TLs, outstanding field confinement of the novel on-chip SSPP TL is demonstrated by the electrical-field- intensity distributions. Measured result matches to simulated one well. It is shown that the proposed on-chip SSPP TL possesses the lowest cutoff frequency and the smallest width relative to the cutoff wavelength, compared to the microstrip and the typical SSPP TLs. Thus the ultra-compact on-chip SSPP TL with strong field confinement may be widely used in the future miniaturized monolithic microwave integrated circuits.