Analysis of longitudinal slots in rectangular waveguides

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.

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.

This paper presents analysis and design of corporate-feed waveguide slot array antennas by hybrid method of moments and finite element methods. Waveguide slot array antennas realize low loss, high efficiency and high gain simultaneously. The drawback for high speed wireless communication is bandwidth. To enhance the bandwidth, fact analysis method based on method of moments are developed and 16×16-element waveguide slot array is designed. The designed antennas realized 20.4% bandwidth.

A rigorous FDTD characterization of a longitudinal radiating slot in a dielectric filled rectangular waveguide in terms of an equivalent shunt admittance is presented. The FDTD method allows one to account for a number of details that affect the antenna performance, such as the waveguide wall thickness, the presence of a finite or infinite flange, a dielectric layer over the slot. High numerical efficiency has been obtained by using Stegen's factorization of the slot admittance. Comparison with other methods (MoM) and with experimental results have shown very good agreement with FDTD simulations even in the computation of the resonant length, which is the most critical parameter. The proposed equivalent circuit allows for a fast and accurate analysis of a radiating slot in a frequency range of the order of 15%.

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.

In this paper, the admittance characteristics of a dielectric filled inclined slot in the narrow wall of a rectangular waveguide have been calculated. By enforcing the continuity of the tangential magnetic field through the slot aperture, an integral equation with the tangential electric field in the slot as the unknown is obtained. An entire domain method of moments (MoM) is used to solve the integral equation. Numerical results show that the slot can resonate without penetrating onto the top and bottom broad walls of the waveguide. It has also been shown that the resonant frequency (length) and the resonant conductance of the slot depend on the dielectric constant of the material filling the slot. The computed results are shown to be in good agreement with those obtained by HP‐HFSS. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 222–226, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10876

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 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>

An analysis of hybrid modes in a rectangular waveguide filled with chiral material is presented in this paper. The modal wavenumbers are computed using the finite difference method together with Muller's root-finding algorithm. A novel scheme is presented whereby the validity of the numerical solution is established with analytical results. Using this numerical methodology, the existence of complex modes for a rectangular chiral waveguide is confirmed. Other notable features such as mode bifurcation and low frequency effects of chirality are also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The theoretical resonant length and experimental normalized conductance of inclined slots are applied in the design of an X-band edge slot waveguide array antenna over the frequency range of 9.5 to 10.5 GHz. The array consists of eight radiating slots machined in the narrow wall of a WR90 waveguide. The array has a non-uniform amplitude distribution with all of the elements fed in-phase. Since the array consists of only eight elements, each element contributes significantly to the overall antenna's characteristics. Experimental results of the measured slot conductances and a formula for the slot depth, including the waveguide wall thickness, for any slot orientation less than 46.6/spl deg/ is presented. This data was used to determine the amplitude distribution and configuration for each element of the array. Measured radiation patterns are presented and characteristics of the antenna examined.

This paper deals with the design of 2.4 GHz slotted substrate integrated waveguide (SIW) array antenna for wireless local area network (WLAN) application. The use of SIW structure is addressed to achieve a compact shape of waveguide-based array antenna especially at low frequency region. The proposed array antenna which is intended to work at the frequency of 2.4 GHz applies several configurations of longitudinal slot array on an SIW surface. A 1.6 mm thick FR4 epoxy dielectric substrate is used to deploy the design of SIW-based slotted waveguide array antenna. The performances of array configuration as well as the effect of slots number are investigated to attain the specified requirement. A 4.8 dBi gain could be achieved by a 1 × 2 slotted waveguide array antenna which has 8 slots in each array configuration.

A design of linear 8-element horn array antenna with 45/spl deg/-slant polarization operating in octave bandwidth (4...8 GHz) is presented. The array antenna is characterized by sector type radiation patterns with gain ranging from 14 dB (at low frequency) to 18 dB (at high frequency) and side lobe levels less than -12dB. Wide bandwidth, slant polarization and relatively simple construction were achieved due to the innovative use of combination of E-plane power divider based on rectangular waveguide with symmetrical double-ridged waveguide components. Proposed design was numerically optimized. A prototype has been manufactured, verified and all-round tested.

Planar Beam-forming Antenna Array for 60-GHz Broadband Communication

Monopole antennas are widely used in communication systems because of features such as pure vertical polarization and omnidirectional radiation patterns in the horizontal plane. Conventionally, monopole antennas are fed through a ground plane by a coaxial probe. Recently, monopole antennas fed by printed transmission lines have attracted increasing attention. However, to the best of our knowledge, monopole antennas are seldom fed by a rectangular waveguide. We consider the problem of this type of feed because of our interest in designing an omnidirectional antenna at millimeter wave bands. At millimeter wave frequencies, rectangular waveguides are preferred to coaxial or microstrip lines because they exhibit very low loss, have a large power handling capacity and other waveguide components are readily available. The paper presents a design for monopole antennas fed by a rectangular waveguide. In order to achieve a good transition from a rectangular waveguide to the monopole antenna, a ridged waveguide section is introduced, and the vertical monopole is attached to the ridge through a circular aperture opened on the upper broad-wall of the rectangular waveguide, which is part of the ground plane. Two examples are provided and experimental tests of one of these antennas shows that the monopole can achieve about 24% bandwidth and 5 dBi gain.