Self-Calibration Technique and Permittivity Measurement Using a Slotted Rectangular Waveguide

Slots in rectangular waveguides are often used at elements in linear array antennas. The polarisation of the radiated energy is usually linear. Circular polarisation can be obtained with compound slots in the broad wall. Experiments have shown that circular polarisation can be obtained from certain I-shaped slots in the narrow wall.

Numerical analysis is presented for the characteristic parameters of centered-inclined coupling slot in rectangular waveguides, taking into account the transverse distribution of the electric field across the slot aperture. Integral equations are formulated based on dyadic Green’s function theories and solved using the method of moments. Trigonometric basis functions are adopted. It is found that the method will converge with up to ten basis functions. The characteristic parameters can be easily obtained for different slot sizes. Resonant length and resonant resistance of the coupling slots are calculated. It is shown that the calculated results have very high accuracy, compared with simulated results obtained from commercial software. Therefore, it can be effectively applied in the synthesis of antenna arrays. Effects of the transverse distribution on calculating resonant parameters of the coupling slot are also analyzed. The results show that if the transverse distribution of the electric field is neglected, the calculated error tends to become larger when the slot gets wider or thinner.

Waveguide coupling and radiation by means of apertures is modelled using a hybrid technique which combines the finite element method with the moment method. Unlike the conventional pulse expansion and point matching technique, it ensures the convergence of the resultant admittance matrix elements without introducing any assumptions about the field distribution on the apertures. Coupling and radiation problems formed by a conventional transverse slot in rectangular waveguide and a complex T-shaped slot in a bifurcated waveguide are examined respectively, and excellent agreement has been obtained for both cases when compared both with alternative theoretical predictions and with measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

With the advantage of small volume, light weight, high aperture efficiency and low side lobes, The Antenna Array of Slots in Rectangular waveguide is widely used in many microwave communication systems that requires narrow beam and shaped beam. This paper analyses the structure and design procedures of antenna array of slots in the narrow wall We first obtain the physical size of each slot by using the parameter sweep function of the Ansoft HFSS software. Then we created a complete model. Finally, we perform the simulation and compare against the design requirement There is a good agreement between simulation and design requirement.

The leaky-wave antennas in the form of closely spaced transverse slots cut in a broad wall of rectangular waveguide were investigated. The thickness of waveguide walls and interaction between slots were taken into account in numerical calculations.

Arrays of broadwall shunt slots in rectangular waveguides

A novel analysis for computing the admittance characteristics of edge slots with a salient feature in successfully considering the finite waveguide wall thickness is presented. The variational equation for the electric field in the slot region between the inner and outer waveguide walls is derived by applying the variational reaction theory and solved by the finite-element method. The division of the slot region into small elements of triangular cylinders and the basis function for each element are described in detail. In the limiting case of zero wall thickness, this finite-element analysis is reduced to a moment-method analysis using Galerkin's approach with triangular basis functions. The effects of waveguide wall thickness on the characteristics of the slot are investigated by comparing the numerical results with and without considering the wall thickness. Negligence of the wall thickness may result in a severe underestimation of the resonant length by as large as 14% for edge slots cut in typical X-band waveguides. The computed results with the finite wall thickness taken into account have been checked with the measured data published in previous literature and those obtained by a carefully devised experimental setup. Good agreement between theoretical and experimental results is obtained to demonstrate the validity of the analysis.

A complete analytic array design process [1] with slots fed by dielectric filled waveguide requires accurate prediction of slot characteristics. A theoretical analysis of a longitudinal slot on the wall of a rectangular waveguide was given by Vu Khac [2] and Vu Khac and Carson [3]. It is assumed that the magnetic current J has no variation along the narrow dimension of the slot. This assumption violates the edge condition and therefore reduces the accuracy of the final results. In this paper we formulate the same problem with the edge condition and analyze slots.

Technique is proposed for the calculation of radiation field from a slot in a rectangular waveguide, the slot shape being nonrectangular. The technique is based on a boundary-value problem formulation in terms of Hertz electric and magnetic potentials introduced for the interior and exterior domain of the slot and for the slot space as well.

A slotted single-grating rectangular waveguide is proposed as the SWS of a novel 0.65 THz BWO. Utilizing HFSS, the cold electromagnetic performance of the SWS is studied. Input/output structure is designed. This BWO is verified by a 3-D particle-in-cell simulation using MAFIA. A 0.88W peak output power at 0.65THz is obtained under12-kV operating voltage and 7-mA beam current.

The longitudinal slot in a rectangular waveguide is solved by the moment method, where the transverse variation of the tangential electric field on the apertures of the slot contains the correct edge behaviour. It is shown that three expansion functions are enough for an excellent convergence and accuracy of the solution.

The rectangular resonator chamber constructions have be proposed and investigated for vacuum-plasma processing and thin-film covering of multilayered planar substrates. The rectangular waveguide aperture and slot antennas have been considered to feed the chamber. The multiaperture, multislot with transverse slots, and single longitudinal slot antennas have been proposed

Rectangular waveguide slot arrays are commonly used in several microwave antenna systems. The slots are most often located in the broad wall of the rectangular waveguide, arranged longitudinally parallel with the waveguide axis, because this provides good control of the excitation of each slot over a large dynamic range by adjusting the offset of the slot from the center line of the waveguide. However, longitudinal slots can only radiate electrical fields that are transversely polarized with respect to the waveguide axis. If longitudinal (or dual) polarization is required, the slots (or half of them) must be located transverse to the waveguide axis. Transverse resonant slots in the broad wall are too strongly excited for use in large arrays, so transverse narrow slots in the narrow wall are preferred. In the latter case the slots are not excited unless they are tilted or coupled to tilted parasitic elements like wires or posts inside the waveguide. The purpose of the present paper is to analyse an untilted narrow wall slot excited by two tilted wires. An improved and extended analysis in which the slot extensions into the neighboring two broad walls are included, is described. The virtual cylinder method is applied to the calculation of the external admittances of the slot using wedge dyadic Green's functions and entire-domain basis functions in order to get good convergence of the integrals of the spectral domain formulations.

A new permittivity measurement method for low loss dielectric materials using frequency selective surface (FSS) resonator and rectangular waveguide are researched in this paper. FSS resonator is designed by analyzing the influences of outer radius, ring width, length and width of substrate integrated waveguide (SIW). The developed FSS resonator is placed in the flanged ridge waveguide, while the dielectric material is placed closely to the FSS resonator. Then it analyzed the relationship between the resonant frequency point shifting value before and after putting sample in tester. This technique is based on the frequency only, with enough measurement accuracy for the dielectric permittivity.

A simple nondestructive method is presented for the measurement of the complex permittivity ?r of materials. The reflection coefficient ? of a flanged open-ended rectangular waveguide placed, next to a flat large sample is computed by a variational method as a function of the dielectric constant. Computer-generated charts and an optimization computer program are elaborated. ?r can then be easily determined from the measured amplitude and phase angle of the reflected wave in the waveguide. The method is best suited for materials having high dielectric constants and large losses.