Design of broadband transition structure from microstrip to slotline with band notched characteristic

Abstract

In this paper, a broadband transition structure from microstrip line to slotline with band-notched characteristic is proposed. To match the 50O microstrip line, 4 Chebyshev impedance transformations are used in the transition structure, and its bandwidth is widened. There is a fan-shaped radial line at the microstrip terminal. A U-shaped slot is etched on the microstrip line with stepped impedance matching to achieve band-notch characteristic. By changing the length of the slot, the band notch is realized at different frequencies. Simulation and optimization of the transition structure are made by using the high frequency simulation software HFSS to achieve the band-notch function at 3.37-3.84 GHz and 10.67-11.14 GHz. In the rest of the band, return loss S11 is less than -15 dB, and voltage standing wave ratio (VSWR) is less than 1.5.