A Wideband Planar Excitation Technology of TE20 Mode Substrate Integrated Waveguide (SIW) and Its Applications

The higher order mode Substrate Integrated Waveguide (SIW) has advantages in the applications, (1) simplifying the structure with reduced fabrication cost and (2) enhancing the stability of performance by relaxed fabrication tolerance. In this paper, a new wideband TE20 mode excitation technology is proposed and investigated for the SIW. A slot along the mid line in the longitudinal direction of the SIW is employed to convert the electromagnetic field pattern between slotline and the higher order modes SIW. The transition has simple and compact tructure as well as wide bandwidth. According to the measured results, the return loss is better than 10dB, in the frequency range from 7.3GHz to 11.6GHz with a fractional bandwidth of 45.5%. The average measured insertion loss of the back-to-back transition between the slotline and the TE20 mode SIW is about 1.5 dB in the operation band. As an application example of this novel structure, a SIW planar balun is proposed and fabricated. The measured return loss, amplitude imbalance, and phase imbalance are better than 15 dB, 0.45 dB, and 3.8°, respectively. The average measured insertion loss is about 4.67 dB, with 47.7% bandwidth (7.5-12.2 GHz). The balun not only shows excellent performance but also demonstrates the existence of TE20 mode in the SIW.