New Wideband Transition From Microstrip Line to Substrate Integrated Waveguide

Abstract

A new wideband transition from microstrip line to substrate integrated waveguide (SIW) is introduced. Unlike most transitions that show reduced return loss over significant parts of a regular waveguide band, the presented configuration achieves return losses better than 30 dB in standard waveguide frequency bands from X to E. The new aspect of this transition is the addition of two vias to the widely used microstrip taper transition. Moreover, the influence of the substrate height is demonstrated. The results in each frequency band are compared with the data for the regular microstrip taper alone. A design formula for the placement of the vias and taper dimensions is presented and demonstrated to provide excellent results. The structures are simulated and optimized with CST Microwave Studio. Measurements performed on a Ku-band back-to-back prototype transition demonstrate a minimum return loss of 26.05 dB and maximum insertion loss of 0.821 dB over the entire Ku-band, thus validating the design approach.

Ku-band Transition with not Metalized Air-Vias between Microstrip Line and Substrate Integrated Waveguide

“…About the return loss in fig. 4(b), the results show that the return loss is higher than 35 dB for taper-vias transition [9] and higher 41 dB for the proposed air-vias transition. 5(a), we can see that the insertion loss is lower than 0.17 dB for taper-via transition and lower than 0.16 for the proposed transition.…”

“…After the optimization in the parameters of the transition, in the simulation results we can see that the insertion loss is lower than 0.16 dB for taper-vias transition [9] and lower than 0.15 for the proposed transition in the entire Ku-band (12.4 -18 GHz), from Fig. 4(a).…”

“…Fig. 4 shows the comparison between the simulated S parameters of the proposed transition and those from [9] in Ku-band frequency.…”

“…Comparing to the other microstrip transitions, the advantage of this new structure, is that there is better field matching between the SIW and micosrtip due to the confinement of the fields around the microstrip line. In order to validate this configuration we compare with taper transition without air-vias proposed in [9]. The structure consists of SIW substrate with ten metallized vias and thirteen not metallized air-vias at the both sides of the microstrip line.…”

An Improved Broadband Siw Phase Shifter With Embedded Air Strips

“…Figure 1 shows the configuration of the proposed broadband SIW phase shifter with embedded air strips. For the constant reference line, it seems to be the same as the new wideband SIW structure [17], which is formed by two rows of metallized vias, four metallized vias on the edge of SIW section, two microstripto-SIW transitions and two microstrip lines. For the phase shifters, a row of embedded air strips is additionally added to both generate phase shift and expand the bandwidth.…”