Telecommunication technologies

The proposed waveguide strategy for arbitrary routes at 15 kHz a Simulated energy fields of a “N”-shaped waveguide with width l = 0.82λ. The radius of curvature is 2.8λ. S refers to the location of point source. b “U”-shaped waveguide with width l = 1.47λ. The radius of curvature is 3.3λ. S refers to the location of point source. c Two adjacent waveguide paths with a distance of

2λ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda$$\end{document} (l = 0.82λ). The radius of curvature is 2.9λ. Two point sources are placed on S1 and S2. d Wave splitting by a waveguide junction (l = λ). The radius of curvature is 3.2λ. S refers to the location of point source.

Guided-mode theory for waveguides a Schematic of omnidirectional wave reflection in a waveguide excited by a point source S placed in the middle of the waveguide. Points A and E are located symmetrically at the boundary of waveguide. Wave fields in points A and point C have the same phase with their projections B and D, respectively. φ represents the phase shift when total reflection appears at the waveguide boundary. b The guided-mode order β as functions of the ratio l/λ and the incident angle θi. The whole region is divided into three parts (0.2–1.2, 1.2–2.2, and 2.2–3.2), which represent different patterns in standing wave fields. c Simulated displacement fields |w| in the waveguides with l/λ = 0.5,1.5,2.5, respectively. The amplitude |w| on a typical line (dashed yellow line) crossing the waveguide (the orange curve) is examined in each subplot.


Concept:
Waveguide paths are designed to minimize signal attenuation, reflection, and phase shift. The design of waveguide paths involves selecting the proper waveguide type, dimensions, and element configurations to achieve optimal performance. The selection of waveguide type and dimensions is based on the operating frequency, power level, and environmental requirements.

The field patterns of some common waveguide modes
One of the most important differences in the operation of waveguide filters compared to transmission line designs concerns the mode of transmission of the electromagnetic wave carrying the signal. In a transmission line, the wave is associated with electric currents on a pair of conductors. The conductors constrain the currents to be parallel to the line, and consequently both the magnetic and electric components of the electromagnetic field are perpendicular to the direction of travel of the wave. This transverse mode is designated TEM^[l] (transverse electromagnetic). On the other hand, there are infinitely many modes that any completely hollow waveguide can support, but the TEM mode is not one of them. Waveguide modes are designated either TE^[m] (transverse electric) or TM^[n] (transverse magnetic), followed by a pair of suffixes identifying the precise mode.^[9]
This multiplicity of modes can cause problems in waveguide filters when spurious modes are generated. Designs are usually based on a single mode and frequently incorporate features to suppress the unwanted modes. On the other hand, advantage can be had from choosing the right mode for the application, and even sometimes making use of more than one mode at once. Where only a single mode is in use, the waveguide can be modelled like a conducting transmission line and results from transmission line theory can be applied.^[
The mode with the lowest cutoff frequency of all the modes is called the dominant mode. Between cutoff and the next highest mode, this is the only mode it is possible to transmit, which is why it is described as dominant. Any spurious modes generated are rapidly attenuated along the length of the guide and soon disappear. Practical filter designs are frequently made to operate in the dominant mode