Design of wideband coaxial-TEM to circular waveguide TM<inf>01</inf> mode transducer

Abstract

Coaxial TEM to circular waveguide TM 01 mode transducer designs with wide bandwidth and compact size are presented in this paper. The coaxial feed with its centre conductor extended as a cone, is applied at the axis of a circular waveguide. Further modifications in the conical shape monopole are proposed (skirt and inverted cone), which result in a wide bandwidth (28.5% and 33.8% respectively) of TM 01 mode excitation in a circular waveguide. Many of the High Power Microwave (HPM) sources generate output signal in the form of TM 01 mode of circular waveguide. The proposed transducer is useful for low power calibration of an antenna or a mode converter designed for high power microwave applications.

Wideband Printed TM01 to TE11 Mode Converters

“…The output mode of the feed, which feeds the mode converters, should be a pure TM 01 mode in order for the mode converters to work appropriately. The monocone structures offer a wideband response for this transduction [30]. The feed, in this case, converts the TEM mode of the coaxial cable to the TM 01 mode over a wide bandwidth.…”

Computational Design of an In-Line Coaxial-to-Circular Waveguide Adapter with More Than an Octave Bandwidth

“…The lengths La and Lb of the rectangular-to-circular waveguide transformer are made sufficiently large so that the reflection coefficient is less than −20 dB at 8-24 GHz. Local peaks due to higher-order mode excitation occur at 19.18, 20. 2 . In a fabricated adapter, the transmission magnitude will be reduced by the finite conductivity of the conducting material and the contact resistance in the mating parts.…”

“…Circular waveguides are widely used in high-frequency signal transmission as well as in various microwave components, including rotary joints [1], high-power microwave devices [2], radiating elements [3][4][5][6], measurement fixtures [7] and power transmission using the low-loss TE 21 mode [8]. In all these applications, it is often necessary to launch a signal from a coaxial cable to a circular waveguide for which a high-performance adapter is required.…”

An in-line coaxial-to-circular waveguide transition at X band

“…To widen the bandwidth, conical coaxial line and tapered cylindrical horn was reported for radiation applications [9]. Using multistage impedance transformer to achieve bandwidth extension was a common way [10,11], while the multistage can also be approximated as a cone to realize the same purpose [12]. It is mentioned that such a transition can be orthogonal between the coaxial line and the circular waveguide [13,14].…”