Open-ended Waveguide Cavities Research Articles

Beam Steering 3D Printed Dielectric Lens Antennas for Millimeter-Wave and 5G Applications.

Two types of cost-efficient antennas based on dielectric gradient index dielectric lens have been designed for 5G applications at 28 GHz. The first is a linearly polarized flat lens antenna (LP-FLA) for terrestrial 5G communications. The second is a novel circularly polarized stepped lens antenna (CP-SLA) for 5G satellite services. An efficient design method is presented to optimize and conform the lens topology to the radiation pattern coming from the antenna feeder. The LP-FLA is fed by a traditional linearly polarized pyramidal horn antenna (PHA). The CP-SLA is fed by an open-ended bow-tie waveguide cavity (BCA) antenna. This cavity feeder (BCA), using cross-sections with bow-tie shapes, allows having circular polarization at the desired frequency bandwidth. The two types of presented antennas have been manufactured in order to verify their performance by an easy, low-cost, three-dimensional (3D) printing technique based on stereolithography. The peak realized gain value for the flat (LP-FLA) and stepped (CP-SLA) lens antennas have been increased at 28 GHz to 25.2 and 24.8 dBi, respectively, by disposing the lens structures at the appropriated distance from the feeders. Likewise, using an array of horns (PHA) or open-ended bow-tie waveguide cavity (BCA) antenna feeders, it is possible to obtain a maximum steering angle range of 20° and 35°, for a directivity over 15 dBi and 10 dBi, in the planar and stepped lens antennas, respectively.

Miniaturized Cylindrical Open-Ended SIW Cavity Antenna and Its Dual-Band Applications

A cylindrical open-ended substrate-integrated waveguide (SIW) cavity is studied and analyzed in this work. Two orthogonally oriented gaps are used to shrink the dimension of the cylindrical open-ended SIW cavity. Then, the miniaturized cylindrical open-ended SIW cavity is used to construct dual-band antennas. One dual-band antenna is realized by a composite structure that supports two independent modes: they are the half-circular loop mode for the lower band and the half quasi TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11(1/2)</sub> mode for the upper band. The other dual-band antenna is an aperture-shared structure: the lower band is related to the miniaturized cylindrical open-ended SIW cavity which works at the quasi TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11(1/2)</sub> mode; the upper band is characterized by suspending a concentric slot-loaded circular patch which works at the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> patch mode over the empty space of the miniaturized cylindrical open-ended SIW cavity. All modes involved in the two dual-band antennas, the half-circular loop mode, the half quasi TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11(1/2)</sub> mode, the quasi TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11(1/2)</sub> mode, and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode, are featured by broadside radiation. The structures of the two dual-band antennas are easy to fabricate by using conventional printed circuit board (PCB) techniques and can be integrated with other planar circuits. Compared to other open-ended cavity antennas, the proposed cylindrical counterpart shows a more compact size and lower profile.

Open-ended microwave oven for flip-chip assembly

A novel open-ended waveguide cavity resonator for the microwave curing of bumps, underfills and encapsulants is described. The open oven has the potential to provide fast alignment of devices during flip-chip assembly, direct chip attach, surface mount assembly or wafer-scale level packaging. The prototype microwave oven was designed to operate at X-band for ease of testing, although a higher frequency version is planned. The device described in the paper takes the form of a waveguide cavity resonator. It is approximately square in cross-section and is filled with a low-loss dielectric with a relative permittivity of 6. It is excited by end-fed probes in order to couple power preferentially into the TM3,3,k mode with the object of forming nine ‘hot-spots’ in the open end. Low power tests using heat sensitive film demonstrate clearly that selective heating in multiple locations in the open end of the oven is achievable.

A polarimetric characterization of the modal behavior of open-ended waveguide cavities

A polarimetric characterization of the modal behavior of open-ended waveguide cavities

An iterative physical optics approach for analyzing the electromagnetic scattering by large open-ended cavities

A formulation based on the high frequency asymptotic principles of physical optics is developed for analyzing the scattering by relatively arbitrary open-ended waveguide cavities containing complex interior terminations. A magnetic field integral equation (MFIE) is obtained for the equivalent currents on the interior cavity walls and is solved using an iterative physical optics (IPO) algorithm which iteratively applies physical optics to account for multiple reflections inside the cavity. The number of iterations required for convergence is related to the expected number of important reflections. The IPO method is more approximate than a matrix solution of the MFIE, but it is quite accurate for electrically large cavities and is much more efficient. Numerical results are presented which demonstrate the convergence and accuracy of the method by comparison with modal reference solutions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spectral iterative algorithm for RCS computation in electrically large or intermediate perfectly conducting cavities

A novel algorithm designed to compute efficiently and accurately the high-frequency electromagnetic scattering from open-ended waveguide cavities is presented. The cavity is converted into a stepped-waveguide model so that the field spectra are propagated, forward and backward, along each waveguide section. As boundary conditions for perfect electric conductors are applied via image theory, they are of local nature and take into account only the first-order interactions between each pair of waveguide sections. Accordingly, additional forward-backward iterations must be performed if multiple interactions are to be taken into account. Finally, the radar cross section due to the interior irradiation is calculated by a Kirchhoff-based aperture integral. Good agreement with method of moments and hybrid modal solutions is found, as well as with experimental data, for two-dimensional and three-dimensional cavities with rectangular cross section. >

A finite-difference method for the third-order simplified wave equation: assessment and application

A finite-difference method for coding the third-order simplified one-way wave equation is analyzed and assessed for application to two-dimensional waveguide structures. The general formulation for the simplified one-way wave equations based on the expansion of the eigenvalue equation is briefly discussed. The stability criteria of the finite-difference schemes are analyzed by applying the von Neumann method. Numerical dissipation is studied by calculating the power attenuation along the propagation direction. Finally, the EM wave propagation and scattering in the small and medium size open-ended parallel-plate waveguide cavities are calculated by using the method, and are compared with modal solutions. >

A reciprocity formulation for the EM scattering by an obstacle within a large open cavity

A formulation based on a generalized reciprocity theorem is developed for analyzing the external high-frequency EM scattering by a complex obstacle inside a relatively arbitrary open-ended waveguide cavity when it is illuminated by an external source. This formulation is also extended to include EM fields whose time dependence may be nonperiodic. A significant advantage of this formulation is that it allows one to break up the analysis into two independent parts, one dealing with the waveguide cavity shape alone and the other with the obstacle alone. The external scattered field produced by the obstacle (in the presence of the waveguide cavity structure) is given in terms of a generalized reciprocity integral over a surface S/sub T/ corresponding to the interior waveguide cavity cross-section located conveniently but sufficiently close to the obstacle. Furthermore, the fields coupled into the cavity from the source in the exterior region generally need to propagate only one way via the open front end (which is directly illuminated) to the interior surface S/sub T/ in this approach, and not back, in order to find the external field scattered by the obstacle.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wavelet analysis of radar echo from finite-size targets

The wavelet analysis technique is applied to analyze the frequency-domain electromagnetic backscattered signal from finite-size targets. Since the frequency-domain radar echo consists of both small-scale natural resonances and large-scale scattering center information, the multiresolution property of the wavelet transform is well suited for analyzing such multiscale signals. Wavelet analysis examples of backscattered data from an open-ended waveguide cavity and a plasma cylinder are presented. Compared with the conventional short-time Fourier transform, the wavelet transform provides a more efficient representation of both the early-time scattering center data and the late-time resonances. The different scattering mechanisms are clearly resolved in the time-frequency representation. >

Wavelet analysis of backscattering data from an open-ended waveguide cavity

The wavelet analysis technique is applied to analyze the electromagnetic backscattering data from an open-ended waveguide cavity. Compared to the conventional short-time Fourier transform, the wavelet transform results in a better representation of the scattering features in the time-frequency plane, due to its multiresolution property. >

Two ray shooting methods for computing the EM scattering by large open-ended cavities

Two ray shooting approaches are presented for analyzing the high frequency external EM scattering by open-ended waveguide cavities of relatively arbitrary shape and with a planar interior termination. The contribution to the external scattering arising from the interior cavity region is found by (i) the shooting and bouncing ray (SBR) method, and (ii) the generalized ray expansion (GRE) method. The basic difference between the two methods is in the way the rays are initially launched into the cavity interior via the open end which is directly illuminated. While the SBR method tracks only the incident geometrical optics field which enters the cavity, the GRE method also intrinsically includes the fields diffracted into the cavity by the edges at the open end. Also, in the SBR method a new set of rays needs to be tracked for each incidence angle, while in the GRE method only one set of rays needs to be tracked independent of the incidence angles, although this is generally a much larger set than that used in SBR for a single incidence angle. Therefore, it is found that the SBR method is preferable for analyzing the scattering from cavities which are very large electrically and for relatively few incidence angles. On the other hand the GRE method is preferable for analyzing not only large but also moderately large cavities and for cases where a large number of incidence angles are needed. Numerical results and comparisons based on these methods are presented.

Modal, ray, and beam techniques for analyzing the EM scattering by open-ended waveguide cavities

The problem of high-frequency electromagnetic scattering by open-ended waveguide cavities with an interior termination is analyzed via three different approaches. When cavities can be adequately modeled by joining together piecewise separable waveguide sections, a hybrid combination of asymptotic high-frequency and modal techniques is employed. In the case of more arbitrarily shaped waveguide cavities for which modes cannot even be defined in the conventional sense, the geometrical optics ray approach proves to be highly useful. However, at sufficiently high frequencies, both of these approaches tend to become inefficient; hence, a paraxial Gaussian beam technique, which retains much of the simplicity of the ray approximation but is potentially more efficient, is investigated. Typical numerical results based on the different approaches are discussed. >