Axially corrugated cylindrical waveguides with wall radius described by 0 (1 + cos 2 ), where 0 is the average radius of the periodically rippled wall with period and amplitude , have been largely used as slow-wave structures in highpower microwave generators operating in axisymmetric transverse magnetic (TM) modes. On the basis of a wave formulation whereby the TM eigenmodes are represented by a Fourier-Bessel expansion of space harmonics, this paper investigates the electrodynamic properties of such structures by deriving a dispersion equation through which the relationship between eigenfrequencies and corrugation geometry is explored. Accordingly, it is found that for 0 1 a stopband always exists at any value of ; the condition 0 = 1 gives the widest first stopband with the band narrowing as the ratio 0 increases. For 0 = 0 5 the stopband sharply reduces and becomes vanishingly small when 0.10. Illustrative example of such properties is given on considering a corrugated structure with 0 = 1 0 = 2 2 cm, and = 0 1, which yields a stopband of 1.5-GHz width with the central frequency at 8.4 GHz; it is shown that in a ten-period corrugated guide, the attenuation coefficient reaches 165 dB/m, which makes such structures useful as an RF filter or a Bragg reflector. It is also discussed that by varying 0 and we can find a variety of mode patterns that arise from the combination of surface and volume modes; this fact can be used for obtaining a particular electromagnetic field configuration to favor energy extraction from a resonant cavity.

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In this letter, an UWB BPF with a CDSIR, an OLDGS, and an LPF using DGSs is presented. The LPF used in this BPF resulted in the wide upper-stopband performance than a conventional UWB BPF. The fabricated UWB BPF is compact and achieved a wide passband from 3.4 to 10.9 GHz with good frequency characteristics. The insertion loss of the compact UWB BPF is less than 1 dB at frequencies from about 4.4 to 9.3 GHz. The minimum insertion loss is 0.61 dB at a frequency of 7.02 GHz. The group delay variation, which is an important factor for a UWB system, is less than 0.4 ns within the operating band. Meanwhile, a wide upper-stopband with the insertion loss higher than 30 dB in range of 11.1-20 GHz is achieved. These results have indicated a reasonable agreement between simulation and measurements. In addition, it has a compact size with 19.5 Â 19 mm. ABSTRACT: Microwave propagation in a metallic waveguide loaded with an array of split-ring resonators is examined both analytically and experimentally. The synthesized combined medium exhibits a frequency band around 6.0 GHz with simultaneously negative values of permittivity and permeability, which allow transmission in an otherwise forbidden band for the hollow waveguide.

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