S-matrix of a slot-coupled circular to rectangular waveguide T-junction

An analysis of a slot-coupled T-junction consisting of a circular to rectangular waveguide is presented. The Galerkin method of moments with entire domain sinusoidal basis functions is used to solve the slot aperture electric field integral equations taking into account finite wall thickness. The slot coupler characteristics are deduced, including resonant length and dominant mode scattering. The theoretical results on the magnitude of the s-parameters are compared with experimental results. The effect of the variation of diameter of the circular waveguide as well as the width of the slot on the resonant length of the slot is also studied.     

A rigorous modal analysis of H-plane waveguide T-junction loadedwith a partial-height post for wide-band applications

A rigorous modal analysis (MA) for the H-plane waveguide T-junction loaded with a partial-height conducting post is presented in this paper. The analysis is based on the classical resonator mode-matching technique for waveguide junction problems and a novel concept called extended eigenmode functions. The new concept can be used for constructing eigenmode functions of a complex resonator region as long as the modal solution for a subproblem is available. Particularly for the T-junction problem, the modal solution for the two-port in-line waveguide loaded with the post is used. The proposed MA has been extensively verified by a finite-element method software package. Excellent agreement can be observed. Numerical results obtained by the analysis reveal that by adjusting the dimension of the loading post, the usable band width of the T-junction for constructing a diplexer can be significantly expanded. Since the generalized scattering matrix is obtained, the proposed analysis can be integrated with other available waveguide key building-block models for system analysis     

Analysis of slot-coupled transitions from microstrip-to-microstripand microstrip-to-waveguides

This paper provides an accurate, versatile, and computationally efficient method for the analysis of slot-coupled transitions from microstrip-to-microstrip, and microstrip-to-rectangular and parallel-plate waveguides. The accuracy of this method is ensured by satisfying all the boundary conditions through a mixed electric-magnetic current integral equation formulation, combined with the moment method. Computational efficiency is achieved by limiting the discretization to only the strips and apertures and by using the accurate and rapidly convergent complex images. To verify the accuracy of this method, the transitions are analyzed using the finite-difference time-domain (FDTD) method. Experimental results are also obtained for some structures. Close agreement is found between the complex image results, the FDTD results, and experiment over a wide frequency range     

Analysis of a strip in a waveguide

An analysis and an experimental study of a strip in a transverse plane of a rectangular waveguide below cutoff are presented. This work is a preliminary step in analyzing a stripline-fed slot antenna array in which each stripline feed is enclosed in a rectangular waveguide below cutoff. A numerical method is developed to solve a “pseudo” mixed-potential integral equation for the current on the strip excited by a delta-gap source at some point along the strip. The Green's function for dipole sources in the rectangular waveguide is used in the spectral and spatial representations and Shanks' transform is employed to speed up the convergence of the doubly infinite series. Numerical and experimental results are presented for a monopole fed at one wall of a rectangular waveguide and for a bottom-fed and bottom-loaded strip in a rectangular waveguide     

Construction of a slot-coupled planar antenna for dual polarisation

A new type of feeding technique for a dual polarisation antenna is presented. The proposed feeding system was experimentally investigated for both a single element antenna and basic planar array antenna. This antenna system demonstrated high performance in both isolation characteristics and radiation patterns     

Analysis of a rectangular waveguide isolator

Isolator conditions are derived for a rectangular waveguide in which magneto-optical and anisotropic dielectric crystals are integrated for reciprocal and nonreciprocalE^{x}-E^{y}mode conversion functions, respectively. Relations between structural parameters are derived by perturbation analysis, and design examples of single-mode isolators with 3.6-, 4.6-, and 6.6-μm square cores are given at the 1.55-μm wavelength. Tolerances in the structural parameter deviations are investigated analytically and numerically. Isolation of more than 20 dB is feasible without any parameter adjustment even when there is a 9- percent deviation in the core dimension.     

Annular slot-coupled dielectric resonator antenna

An annular slot-coupled dielectric resonator antenna is investigated experimentally. As compared with the previous rectangular-slot version, the new configuration offers a much wider bandwidth of 18%. The return loss, radiation patterns, and antenna gain of the configuration have been measured and are discussed     

Analysis of stripline-fed slot-coupled patch antennas with vias forparallel-plate mode suppression

The paper presents an analysis of slot-coupled stripline-fed patch antennas with vias around the slot to minimize the power launched into the parallel-plate mode. A moment-method scattering formulation is invoked to include the effect of vias on the impedance characteristics of the antenna. Coupling between the stripline feed and the ground-plane slot is obtained by invoking reciprocity. Two design examples were fabricated and the measured input impedances verify the accuracy of the analysis. Vias considerably modify the impedance and resonant characteristics of a patch antenna. The radiation efficiency of patch antennas with and without vias is studied and proper location of the vias is shown to drastically reduce power in the parallel-plate mode     

Resonant-tunnelling diode oscillator using a slot-coupled quasioptical open resonator

A resonant-tunnelling diode has oscillated at X-band frequencies in a microwave circuit consisting of a slot antenna coupled to a semiconfocal open resonator. Coupling between the open resonator and the slot oscillator improves the noise-to-carrier ratio by about 36 dB relative to that of the slot oscillator alone in the 100-200 kHz range. A circuit operating near 10 GHz has been designed as a scale model for millimetre- and submillimetre-wave applications.<>     

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

A novel coupling scheme to a rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through a narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low cross polarization components, and minimize back radiation without using a back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results.     

Analysis of a centered-inclined waveguide slot coupler

Integral equations are developed for a centered-inclined coupling slot (including the effect of finite wall-thickness of the common broad-wall) and the slot-aperture electric intensity field is found using the method of moments. Numerical results for resonant length, backscattered wave amplitude, and phase variation off-resonance are presented over a range of values of the waveguide b dimension, wall thickness, slot width, and frequency. It is shown that the resonant length is relatively insensitive to slot tilt, &thetas;, for a standard-height X-band waveguide, whereas its dependence on &thetas; is significant for reduced-height waveguides. The phase variation of scattered TE₁₀ waves in both waveguides off-resonance is less for wider slots and smaller b dimensions. Shunt-series coupling slots exhibit greater phase variation off resonance when compared to a centred-inclined coupling slot. Also, the former has a longer resonant length for a smaller b dimension and for a wider slot. Thus the centred-inclined slot coupler possesses superior characteristics. The higher-order mode coupling between a centred-inclined slot coupler and a pair of straddling radiating slots in the branch waveguide is significant     

Computation of mutual coupling between slot-coupled microstrippatches in a finite array

An analytical method is presented for the evaluation of mutual coupling between slot-coupled microstrip patches in a finite array. The approach is a combination of the equivalence principle and the reciprocity theorem and uses the spectral domain Green's functions for a dielectric slab in a moment method solution for the unknown patch and slot current distribution. The excitation mechanism of the patches is taken into account by introducing an N-port equivalent network, and the impedance matrix of an array of N-element slot-coupled patches is evaluated directly from its network voltage and current matrices of order N². As examples, the mutual impedances and scattering coefficients for two-, four-, and eight-element arrays are evaluated. Results are compared with measured data     

Radiating and scattering analyses of a slot-coupled patch antennaloaded with a MESFET oscillator

In this paper, radiating and scattering analyses of a slot-coupled patch antenna loaded with a MESFET oscillator at free-running and injection-locked states are presented. This arrangement is a basic module of an injection-locked active array. With a small injection signal applied directly to the oscillator in a transmission-type mode or indirectly through a patch antenna to the oscillator in a reflection-type mode, the oscillator loaded antenna then becomes an injection-locked active antenna (ILAA) within the locking range. Simulation results yield the oscillating frequency and radiating power at the free-running state and the locking range and radiating power at the injection-locked state. Both radiating and scattering analyses are performed in a unified approach for the transmission-type and reflection-type operation modes of ILAA. Experiments show the validity of the developed theoretical analyses. These results can be applied in the ILAA array design     

Analysis of a wide resonant strip in waveguide

An analysis has been developed to calculate the susceptance due to a wide resonant strip on the transverse plane of a rectangular waveguide. The theory is based upon a variational form for the susceptance, where the current distribution is determined by the moment method. Accurate results have been obtained for the wide strips as confirmed by the measurements     

Analysis of a ridge waveguide using overlapping T-blocks

A T-block (TB) approach is proposed to analyze the dispersion relation of a ridge waveguide. The field representations of a TB are obtained with the Green's function and mode-matching technique. Rigorous, yet simple dispersion equations for symmetric and asymmetric ridge waveguides are presented using a superposition of overlapping TBs. The rapid convergence characteristics of the dispersion equation are illustrated in terms of the cutoff wavenumbers. A closed-form dispersion relation, based on a dominant-mode approximation, is shown to be accurate for most practical applications such as couplers, filters, and polarizer designs.     

Analysis of a PIN photodiode with integrated waveguide

The absorption coefficient of an InGaAs PIN photodiode integrated with an InGaAsP-InP waveguide is analysed by means of the mode-matching technique. The results compare excellently to published data for ? = 1.3 ?m. It is shown that by an optimised device structure the absorption coefficient can be increased to about 0.15 dB/?m, enabling reduced detector length and smaller capacitance.     

Analysis of irregularities in a planar dielectric waveguide

A numerical method based on the partial variational principle (PVP) is proposed to solve discontinuity problems due to arbitrary irregularities in a planar dielectric waveguide. A variational equation is established and solved by the finite-element method along with the Green's-function technique. The integral variable of the Green's-function is changed so that numerical calculations can easily be performed. Because of the accuracy of the present method, the radiation fields can be obtained with no difficulty. Several numerical results, including the reflection and transmission coefficients as well as the radiation losses and patterns, are calculated and compared     

Dual-polarization slot-coupled printed antennas fed by stripline

This article presents recent techniques in the field of dual-polarization printed antennas for designing shielded radiating structures with high-quality performances in terms of cross-polarization level and input-port isolation. The use of gridded patches provides a natural solution to filtering surface currents and is of key importance in limiting inter-element coupling in arrays. Experimental results obtained on various designs are presented     

Analysis of dielectric-loaded waveguide

The calculation of eigenvalues including propagation constants and cutoff wavelengths of longitudinal section electric and magnetic modes of different orders (LSE_nm and LSM_nm modes) in homogeneous and inhomogeneous lossless dielectric-slab-loaded rectangular waveguides using a modified variation-iteration method is presented. The initial eigenvalues used in the iteration are selected on the basis of a physical consideration. As shown in numerical examples, this method is very efficient for finding all the eigenvalues of LSE_nm and LSM_nm modes by a given free-space propagation constant calculation and a given lower bound of the cutoff wavelength for the cutoff wavelength calculation. In addition, the importance of the adaptive update factor in preventing the possibility of missing existing eigenvalues is also discussed