Wideband compact phase shifter based on hybrid half-mode substrate integrated waveguide and spoof surface plasmon polariton

This paper proposes a wideband compact equal-length phase shifter based on the hybrid half-mode substrate integrated waveguide (HMSIW) and spoof surface plasmon polariton (SSPP) concept for the first time. The HMSIW transmission lines (TLs) with different widths result in different propagation constants. The difference of propagation constants between two HMSIW TLs with two different widths decreases as the frequency increases. Therefore, a wideband phase shifter cannot be designed by using this technique. In this paper, a series of half-butterfly grooves are etched on the top conductor layer of the HMSIW TL to compensate the phase shift. The combination of the SSPP and HMSIW structures provides a higher degree of freedom to keep the propagation constants difference constantly. Accordingly, a wideband response can be achieved by properly tuning the structure. Here, the dispersion characteristic of the butterfly-shaped HMSIW-SSPP can be adjusted by changing the width of the HMSIW and the radius and angle of the half-butterfly grooves. Moreover, the HMSIW-SSPP structure with half-butterfly grooves reduces both longitudinal and transverse dimensions of the proposed circuit. It has more slow-wave effects than the traditional counterpart with rectangular grooves. To validate the concept, a 90 degrees phase shifter is designed and fabricated on a single-layer substrate at the center frequency of 5.8 GHz covering WLAN. The simulated and measured results are in good agreement. The measured results show that the phase shifter has a fractional bandwidth of 31.7% with a phase error of +/- 3.5 0 , an insertion of 1.1 +/- 0.25 dB, and a return loss of higher than 13.8 dB. Also, the size of the proposed phase shifter is 0.4 lambda(g) x 2.18 lambda(g).

Automated summary

This paper proposes a wideband compact equal-length phase shifter based on the hybrid half-mode substrate integrated waveguide and spoof surface plasmon polariton concept. By etching half-butterfly grooves on the top conductor layer of the waveguide, the phase shift is compensated and a wideband response is achieved. The validation shows that the phase shifter has a large bandwidth, small phase error, and small size.