Closely spaced transverse slots in rectangular waveguide

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.

Integrating antennas into a load-bearing airframe structure has the potential for profound improvements in the capability of military and commercial airplanes, by allowing for substantially increased radiator and array size with reduced weight or drag penalties. Reducing the size of array elements can significantly improve the mechanical performance of the loadbearing antenna. The novel single element spiral slot cut in the broad-wall of a WR-90 rectangular waveguide proposed in this paper is smaller than a quarter of the operating wavelength (half of the size of a conventional rectangular slot). The small antenna element enables a slotted waveguide array to be realized without significantly degrading the mechanical performance in load bearing applications. The proposed spiral slot is compared with conventional rectangular slots and exhibits comparable performance in terms of total efficiency (representing coupling from waveguide mode to the slot) and peak realized gain. Total efficiency and peak realized gain of the spiral slot in travelling wave mode are significantly higher than those of a quarter wavelength rectangular slot element which has near zero radiation. The simulated results were validated by manufacturing the spiral slot placed on the broad-wall of a rectangular waveguide. Realized gain patterns of the spiral slot measured at the design frequency corroborate reasonably with the simulations.

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.

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.

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.

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>

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.

Arrays of broadwall shunt slots in rectangular waveguides

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 novel beamforming circular-polarization waveguide antenna array is presented. The open quad-ridged waveguide fed by straight slots cutting in broad wall of rectangular waveguide is used to attain circular-polarization work. The beamforming is realized by using the narrow waveguide coupling power divider and the phase compensation waveguide. The simulated and experimental results show that the AR level is below 1.5dB in 3% bandwidth, and the area of shaped beam pattern is -40° ~ 0°.

The possibilities of control of polarization and energy characteristics of the X-slots cut in the broad wall of rectangular waveguide with a complex load at the end and with the dielectric heterogeneity of the input waveguide section with a slot investigated. Numerical and experimental investigation of energy and polarization characteristics of such systems are performed. Changing the parameters: the dielectric heterogeneity, position its relative the slot and changing complex load allow to adjust X-radiation field with circular polarization, with a high emissivity and low VSWR at the input.

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.

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.

This article proposes a method based on the use of a slotted rectangular waveguide (SRW) for determining the complex permittivity of materials under test (MUTs). Because the slots are nonradiating and the electric field between the two slots is the strongest, the MUTs can be put through the slots and partially filled in the SRW for measurements. The network parameters of the loaded segment of the SRW are evaluated directly via the line-network-network (LNN) self-calibration technique without needing to obtain the error coefficients of the test fixtures first. The LNN technique requires the measurement of an empty SRW and measurements of the SRW loaded with an MUT at three different positions. The mode matching method is used to determine the complex permittivity of the MUT, which is partially filled in the SRW. The proposed method is suitable for the measurements when there are a large number of MUTs to be measured or an MUT need to be measured many times. The simulation and measurement results show the validity, accuracy, and repeatability of the proposed method.