Skew-Symmetric Slotted Waveguide With Mode Select Effect

The mode-selective transmission line (MSTL) has excellent transmission performance due to its wide bandwidth and low loss, which is characterized by the mode-selective effect. In this article, a skew-symmetric slotted waveguide (SSSW) is proposed, whose dominant mode also exhibits the interesting mode-selective effect and transmission performance is similar to that of the MSTL. It is investigated that the dominant mode of the SSSW performs quasi-transverse electromagnetic (TEM) mode at low frequency and quasi-TE ₁₀ mode at high frequency. Then, for fast design, a characteristic impedance formula of the SSSW is derived by the conformal mapping, which has the error less than 3% compared with the finite-element method (FEM). In addition, a microstrip line (MSL) to grounded coplanar waveguide (GCPW) transition is designed to excite the dominant mode of the SSSW, with good transmission of the dominant mode and significant suppression of higher order modes. Finally, the SSSWs with the transitions are fabricated under printed circuit board (PCB) technology and measured with the S21 larger than −2.1 dB and the S11 less than −12.7 dB from dc to 67 GHz, and the attenuation of the SSSW is less than 0.065 dB/mm below 65 GHz. Good eye diagram is obtained with bit error rate (BER) less than $10^{-12}$ for the 32-Gb/s data rate.