Folded meander-line slow-wave structure for millimeter-wave TWTs

The new concept of symmetric (double-folded) and asymmetric (single-folded) folded meander-line slow-wave structures is proposed for broader bandwidth and higher interaction impedance characteristics, respectively. The structures are analyzed using 3D numerical simulation in CST-Microwave Studio for the dispersion and interaction impedance characteristics at Ka-and W-bands. The results are compared against the conventional meander-line structure for the same dimensions. The proposed symmetric structure shows 35 % enhancement in cold bandwidth and the asymmetric structure shows more than 50 % enhancement in the interaction impedance.