Cross-shaped Waveguide Research Articles

Dual-Band Dual-Polarized Shared-Aperture Grid Antenna With Large Frequency Ratio

In this letter, a dual-band dual-polarized shared-aperture grid antenna with a large frequency ratio is presented. To achieve shared aperture and large frequency ratio, a millimeter-wave (mm-Wave) partially reflective surface (PRS) is embedded into a microwave patch antenna. A periodic circular grid patch is adopted not only as the microwave antenna but also as the mm-Wave PRS antenna. The mm-Wave PRS antenna is centrally excited by a cross-shaped waveguide with two coaxial connectors, and the microwave patch antenna is driven by a pair of orthogonal L-shaped probes, resulting in polarization diversity in both bands. A compact microstrip resonant cell (CMRC) and a metal post are designed to reduce the couplings between different ports. For demonstration, a prototype operating in the 3.5 GHz and 28 GHz bands is fabricated and measured. The overlapped measured -10 dB impedance bandwidths between the orthogonal ports cover 3.41–3.59 GHz (5.14%) and 26.62–30.26 GHz (12.8%) in the low and high bands, whereas the measured peak realized gains of 8.75 dBi and 12.79 dBi are obtained, respectively. All port-to-port isolations are larger than 20 dB over the bands of operation.

High-Gain and Low-Loss Dual-Polarized Antenna Array With Reduced Sidelobe Level Based on Gap Waveguide at 28 GHz

In this letter, a 16×16-element dual-polarized antenna array with a reduced sidelobe level is proposed at 28 GHz for fifth-generation (5G) communication systems. The dual linear polarization operation is carried out through cross-shaped waveguide slots and multilayer feeding networks. Low-loss gap waveguide technology and Taylor distribution are applied in the feeding networks. A ridge unequal power divider with flexible power ratio and phase difference is devised and applied in the gap waveguide feeding network to reduce the complexity of unequal power structural design. A prototype of the proposed dual-polarized antenna array is manufactured by milling technology. Measured results show that the realized gains are higher than 28 dBi over the operating frequency band of 27.4–28.6 GHz. Moreover, the sidelobe level is lower than −18.5 dB for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -direction polarization and −19.5 dB for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> -direction polarization.

A Millimeter-Wave Wideband Dual-Polarized Antenna Array With 3-D-Printed Air-Filled Differential Feeding Cavities

A millimeter-wave high-gain dual-polarized antenna array with an enhanced bandwidth is presented. An innovative air-filled differential feeding cavity loaded with a short-ended cross-shaped waveguide is investigated to serve as the feed network and the mode splitter simultaneously of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\,\,\times2$ </tex-math></inline-formula> dual-polarized subarrays. Wideband characteristics and a compact planar size that are desirable for the wideband array design are achieved. Moreover, a wideband dual-polarized waveguide-fed magnetoelectric (ME) dipole antenna with a lightweight self-support geometry and wideband H-plane parallel feed networks with modified dual-layered configurations are proposed, which are convenient to connect with the differential feeding cavity directly. With the use of a commercial metallic 3-D printing facility, the proposed radiating elements, feeding cavities, and feed networks can be combined successfully in a whole piece with a lightweight geometry. The printed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \times 8$ </tex-math></inline-formula> array prototype operating in the Ka-band confirms a wide bandwidth of about 30%, a gain of up to 28.5 dBi, and stable unidirectional radiation patterns for the two polarizations. Benefitted from the advantages of the promising wideband dual-polarized radiations and convenience of fabrication, the proposed antenna array would be attractive for millimeter-wave polarization diversity applications.

Directional coupler design for orbital angular momentum mode-based photonic integrated circuits.

An orbital angular momentum (OAM) dividable on-chip directional coupler design is proposed. To guide OAM modes of topological charge number l = ±1, a waveguide needs to support TE01 and TE10 modes with degeneracy. When a directional coupler is made with such an OAM mode waveguide, it is additionally required to equalize the horizontal-direction coupling strengths of those two OAM constitutive eigenmodes. Base on the coupled mode theory formulation, we have found that this requirement can hardly be satisfied and devised a modified cross-shaped waveguide structure to solve this problem. An example design of OAM mode directional coupler is demonstrated. The coupling length of the designed device is 670 µm, and our numerical simulation showed negligible degradation of OAM mode purity during the operation of complete optical power transfer between two waveguides. To the best of our knowledge, this is the first proposal of the on-chip OAM mode directional coupler. The proposed design approach can be applied to implement various devices for OAM mode-based photonic integrated circuits.

Waves in a Plane Rectangular Lattice of Thin Elastic Waveguides

We study the spectrum of a thin (with the relative width h ≪ 1) rectangular lattice of elastic isotropic (with the Lame constants ⋋ ≥ 0 and μ > 0) plane waveguides simulating joining seams of a doubly periodic system of identical absolutely rigid tiles. We establish that the low-frequency range of the essential spectrum contains two spectral bands (passing ones for waves) of length O(e−δ/(2h)), δ > 0. Above these bands there is a gap of width O(h−2) (stopping zones for waves) and then, in the mid-frequency range, above the cut-off value μπ2h−2 of the continuous spectrum of the infinite cross-shaped waveguide, there is a family of spectral bands of length O(h); moreover, between some of these bands there are opened up gaps of width O(1). The character of the wave propagation depends on whether the frequencies are below or above the cut-off value. In the first case, the oscillations are strictly concentrated near the lattice nodes and the edges are practically immovable. In the second case, the oscillations are localized on the lattice edges, i.e., the nodes are left at relative rest. We show that single perturbations of nodes or edges can cause the appearance of points of the discrete spectrum under the essential spectrum or inside the gaps; moreover, an infinite collection of identical perturbations of nodes can also change the essential spectrum. Bibliography: 78 titles. Illustrations: 5 figures.

Optimal Control Theory Applied to Unintended Source Control and Field Shaping for Time-Harmonic Electromagnetic Waves

This paper addresses the experimental control of time-harmonic electromagnetic waves. The underlying optimal control problem aims to find a set of values to apply to control sources, located in the controlled region or on its boundary, allowing any electromagnetic field caused by an undesired noise source to be suppressed or replaced by any other field map. After a presentation of the control method, illustrated with a few numerical applications, two experimental setups are considered. The first setup aims to control the voltage within a mixed microstrip/coaxial transmission line. In the second setup, the electric field inside a cross-shaped waveguide network is controlled. For both setups, the working frequency is chosen in the ultra-high frequency range, and a comparison is made to the results given by the equivalent numerical models.

Spectrum of a Problem of Elasticity Theory in the Union of Several Infinite Layers

The essential spectrum of the Dirichlet problem for the system of Lame equations in a three-dimensional domain formed by three mutually perpendicular elastic layers occupies the ray [Λ†,+∞). The lower bound Λ† > 0 is the least eigenvalue (its existence is established) of the problem of elasticity theory in an infinite two-dimensional cross-shaped waveguide. It is proved that the discrete spectrum of the spatial problem is nonempty. Other configurations of layers and the scalar problem of the junction of quantum waveguides are also considered.

Single photonic crystal structure for realization of NAND and NOR logic functions by cascading basic gates

In this article, we propose the realization of all-optical NAND and NOR logic functions on a single photonic crystal structure by cascading basic logic gates, viz. AND, OR, and NOT. Initially, to achieve this, a photonic crystal logic gate structure is designed with cross-shaped waveguide as a common gate for AND and OR functions, and another photonic crystal structure is devised with T-shaped waveguide as NOT gate. An additional input, namely reference input, is applied to these basic gate structures whose phase determines the type of the logic function in the former gate structure, and inevitable for NOT function in the latter one. The reference input is out of phase with the actual inputs in AND and NOT functions, whereas it is inphase in OR function. Simulation results show that the contrast ratio for AND, OR, and NOT is 11.74, 9.99, and 54.52 dB, respectively, with a response time of less than 0.15 ps. Later, these logic gate structures are cascaded to realize NAND and NOR functions, resulting a contrast ratio of 10.57 and 8.60 dB, respectively, at a response time of 0.152 ps. The percentage of reduction in the contrast ratio of the cascaded structure compared with the basic AND/OR gate is very small with a value of less than 1.5%. Moreover, the proposed NAND/NOR logic gate obtained by cascading the basic logic gates is quite compact with area occupancy lowered by a factor of 4.5 compared to the cascaded structures available in the literature.

The spectra of rectangular lattices of quantum waveguides

We obtain asymptotic formulae for the spectral segments of a thin () rectangular lattice of quantum waveguides which is described by a Dirichlet problem for the Laplacian. We establish that the structure of the spectrum of the lattice is incorrectly described by the commonly accepted quantum graph model with the traditional Kirchhoff conditions at the vertices. It turns out that the lengths of the spectral segments are infinitesimals of order , , and as , and gaps of width and arise between them in the low- frequency and middle- frequency spectral ranges respectively. The first spectral segment is generated by the (unique) eigenvalue in the discrete spectrum of an infinite cross-shaped waveguide . The absence of bounded solutions of the problem in at the threshold frequency means that the correct model of the lattice is a graph with Dirichlet conditions at the vertices which splits into two infinite subsets of identical edges- intervals. By using perturbations of finitely many joints, we construct any given number of discrete spectrum points of the lattice below the essential spectrum as well as inside the gaps.

H-plane cross-shaped waveguide circulator in magneto-photonic crystals with five ferrite posts

A novel H-plane cross-shaped circulator based on magneto-photonic crystals is experimentally investigated. The band gap of the TE mode for the photonic crystals is calculated by the plane wave expansion method. The transmission characteristics of the circulator are simulated by the finite element method. We perform the experiments in the microwave regime to validate the numerical results. At the central frequency of 10.15 GHz, the measured isolation and insertion loss of the circulator reaches −30.2 and −3.93 dB, respectively. The bandwidth of the circulator is about 550 MHz. The optimal experimental value of isolation is higher than the numerical value.

Development of a mathematical model of microwave filter based on the partially filled cross-shaped waveguide-dielectric resonators

A mathematical model of microwave filter based on the WDR, partially filled by height, set in the cut-off cross-shaped waveguide was developed. The solution to the problem of the H 10 wave scattering along the WDR chain was carried out by applying the GSM and partial regions methods. The obtained model makes it possible to consider an arbitrary number of waves not only in the regular, but also in the cut-off waveguide. Numerical algorithm was programmatically implemented and the convergence of calculations was studied, as a result of which we established that in order to ensure the error in the calculation less than 0.2 %, it was sufficient to consider 5–7 modes in the cut-off cross-shaped waveguide. A mathematical calculation of the one-tier filters designs and their comparison to the experimental prototypes was performed to establish the reliability of the developed model. An experimental study showed that the divergence between the calculated and measured frequencies did not exceed one percent that is the confirmation of the adequacy of the calculations, fulfilled on the basis of the developed model. This model was implemented in the original method of intellectual synthesis and optimization of designs of multitier microwave filters, whose key idea consists in the logical analysis of the frequency response and the subsequent decision making about an evolutionary change in the design, which ensures its assigned form. The results of the study are planned to apply in designing a new model of microwave filter with resonators of different classes

All-optical NOR and NAND gates based on photonic crystal ring resonator

We report a new configuration of all-optical logic gates based on two-dimensional (2D) square lattice photonic crystals (PCs) composed of silicon (Si) rods in Silica (SiO2). The proposed device is composed of cross-shaped waveguide and two photonic crystal ring resonators (PCRRs) without nonlinear materials and optical amplifiers. The gate has been simulated and analyzed by finite difference time domain (FDTD) and plane wave expansion (PWE) methods. The simulation results show that the proposed all-optical logic gates could really function as NOR and NAND logic gates. This new device can potentially be used in large-scale optical integration and on-chip photonic logic integrated circuits.

A rigorous analysis of a cross waveguide to large circular waveguide junction and its application in waveguide filter design

A rigorous analysis is obtained for the problem of scattering at the junction of a cross-shaped waveguide and a larger circular waveguide. The general case of an arbitrary offset and orientation of the cross waveguide axes is considered. The fields matching over the cross aperture of the smaller guide is facilitated by using the transformation of the circular cylindrical Bessel-Fourier modal fields of the circular guide into a finite series of exponential plane wave functions. This permits an analytical finite series solution for the elements of the fields mode matching matrix, from which the general scattering matrix of the junction is obtained. The application of the formulation to circular waveguide filter design is emphasized in the numerical examples. Excellent agreements between theoretical and experimental results are obtained in all the numerical examples.

Propagation of the analog of the H01-mode of circular waveguide in the bend of a cross-shaped waveguide

Propagation of the analog of the H01-mode of circular waveguide in the bend of a cross-shaped waveguide