A Wideband Transition from Microstrip Line to Microstrip Spoof Surface Plasmon Polariton Line for Microwave/Millimeter-Wave Applications

In this article, a wideband transition from a microstrip transmission line to a microstrip spoof surface plasmon polariton (SSPP) transmission line is reported. The proposed transition is realized to achieve better performance starting from low frequencies up to 40 GHz. The proposed shape of the unit cell is taken in such a manner that the momentum, impedance, and polarization of the microstrip line can be matched with that of the SSPP transmission line. The wide operating band of the transition can be achieved by perturbing only the shape of the unit cell. Extra care is taken in choosing the shape of the unit cell so that the fabrication of the circuit becomes easier, especially at millimeter-wave frequencies. The proposed transition has a good transition-occupation ratio and transmission efficiency. The achieved transition-occupation ratio and transition efficiency for all three designed cases are excellent, and it is 34.18%, 44%, and 39% for p=1 mm, 2 mm, and 3 mm, respectively. It is a potential candidate for realizing millimeter-wave antennas and devices due to its attractive properties, such as compact layout, low fabrication cost, ease of fabrication even at millimeter-wave frequencies, and good operational characteristics.