Waveguide Elements Research Articles

Wideband radiation enhancement of waveguide arrays operated as feeds for reflector antennas using patch array covers

[1] This work rigorously analyzes a periodic microstrip patch array printed on a dielectric slab and placed over an array of open-ended sidewall loaded rectangular waveguides. The method of moments using spectral Green's functions for multilayer structures is employed. The application selected to feature the computed results of this structure is array matching. This work thus investigates the ability of such patch arrays to improve the transmission levels of waveguide arrays over those of uncovered ones. The matching performance is also compared with conventional dielectric sheath-type tuners. Two array operation scenarios are studied: direct radiating phased arrays, and focal plane arrays as feeds for reflectors. Earlier studies of the latter scenario show that the decoupling efficiency tends to be poor at low frequencies, due to the electrical proximity between the waveguide elements. It will be demonstrated here that both forms of matching layers can be tuned to provide good matching at low frequencies. This study has opted to investigate the beneficial effects of the sheet and the patch array over a wide frequency band, rather than its optimization over a selected narrow band. Such optimizations can be done in practice for known specific operating bands.

Domino plasmons for subwavelength terahertz circuitry

A new approach for the spatial and temporal modulation of electromagnetic fields at terahertz frequencies is presented. The waveguiding elements are based on plasmonic and metamaterial notions and consist of an easy-to-manufacture periodic chain of metallic box-shaped elements protruding out of a metallic surface. It is shown that the dispersion relation of the corresponding electromagnetic modes is rather insensitive to the waveguide width, preserving tight confinement and reasonable absorption loss even when the waveguide transverse dimensions are well in the subwavelength regime. This property enables the simple implementation of key devices, such as tapers and power dividers. Additionally, directional couplers, waveguide bends, and ring resonators are characterized, demonstrating the flexibility of the proposed concept and the prospects for terahertz applications requiring high integration density.

Novel Optical Neuronal Cell and Data Recognition-generation Circuits in RFID Tags

The optical neuronal cell composed of silicon structure is also studied, and novel cell is proposed. The circuits that recognizes tag call signal and generates the sending data using the analog threshold element with a nonlinear characteristic are studied. In addition, single-mode silicon optical switch with T-shaped SiO2 optical waveguide as a control gate is proposed (5). In this report, the neuronal cell composed of silicon waveguide and electronic active elements is studied, and novel neuronal cell is proposed. The electron-hole pairs generated by illumination with short-wavelength light are used here.

Estimating Waveguide Model Elements from Acoustic Tube Measurements

One-dimensional digital waveguides are widely used to model traveling pressure waves along wind instrument bores comprised of concatenated cylindrical or conical sections. Waveguide filter elements model frequency-dependent losses and delay (dispersion) occurring during propagation and at any boundary or discontinuity producing reflected and transmitted waves. In this work, a technique is described for estimating wind instrument waveguide elements from several measurements of the system's impulse response, each measurement taken with the system having incrementally varying termination/boundary conditions. The measured impulse responses yield sequences of multiple arrivals from which estimates of waveguide element transfer functions may be formed. The measurement and post signal processing technique is explored using simple structures consisting of cylindrical and conical tubes, as these are well described theoretically and provide a basis for validating measured data. All waveguide elements necessary for modeling typical wind instrument bores are collected here, each presented with a theoretical description and accompanying measurement. The measurement and processing system is then shown to yield data closely matching the theory, thus providing confidence that the technique may be extended to accurately measure structures which are more difficult to describe theoretically, such as an instrument's flaring bell.

Near-field excitation and near-field detection of propagating surface plasmon polaritons on Au waveguide structures

The propagation of surface plasmon polaritons guided along Au metal waveguides fabricated by electron-beam lithography is experimentally investigated using simultaneous near-field excitation and detection of plasmon-polariton modes localized at the air/Au interface. The directly measured propagation characteristics of surface plasmon-polaritons agree well with simulation results obtained using full-vector calculations and the analytic dispersion of asymmetric plasmonic waveguides for thin Au films. Our results demonstrate that near-field excitation/detection schemes are well suited for direct imaging and characterization of propagating surface plasmon-fields bound to thin-film metal layers, and can be used for fast and reliable characterization of plasmonic waveguide elements and nanodevices.

A Compact Ridge-Waveguide Contiguous-Channel Frequency Multiplexer

The experimental 4-6.25-GHz contiguous-channel frequency multiplexer being presented comprises three equal-bandwidth four-pole ridge-waveguide channel filters that are series-connected through a quasi-low-pass ridge-waveguide manifold. To minimize insertion loss, the multiplexer's port impedance-matching networks are also realized in ridge-waveguide, limiting the use of strip-type transmission line segments to short uniform-width microstrip feeder lines for linking to the multiplexer's external coaxial ports. The three channel filters are stacked with their waveguide broadsides adjacent to each other, separated only by the thicknesses of the filters' walls to achieve maximum compactness. Quasi-lumped waveguide elements are employed to properly couple the filters to the manifold. The multiplexer design methodology relies on the use of commercial general-purpose software, and on equivalent-circuit models of waveguide multiplexer subcomponents derived therewith. The observed good agreement between measured and predicted multiplexer response characteristics helps to validate the approach.

The Radiotransparent Windows Formed of Waveguides with Complex Cross Sections

Radiotransparent windows with plane surfaces that are periodic structures are considered. The periodic structures are based on dual-polarization and wideband waveguides of a complex section with minimal intercenter distances between waveguides. The aperture e-ciency for such windows is simulated. The use of radiotransparent waveguide windows (frequency-selective surfaces) is a promising line in the development of highly durable and vibrostable centimeter- and millimeter-wave antennas. One of the main requirements of radiotransparent waveguide windows is good matching of their aperture surfaces with free space. Re∞ections from a window are determined to a considerable extent by re∞ections from the apertures of its waveguide elements. Available structures of waveguide windows contain square, circular, and rectangular waveguides whose open ends are poorly matched with free space. In addition, windows based on square and circular waveguides cannot be applied in a wide frequency band when frequency-coverage coe-cient Kf equal to the ratio of the upper and lower frequencies of a waveguide window exceeds » 1:2:::1:3. The use of waveguides with a complex shape of the cross section can improve the characteristics of radiotransparent windows (1{4). A change in the parameters of sections can govern the internal and external characteristics of radiators and radiotransparent windows based on such waveguides. In our investigations, we used the mathematical model of an inflnite array antenna (AA) formed of waveguides with an arbitrary section. The model involves solution of the exterior problem by means of the fleld-joining projection method and solution of the interior problem by means of the flnite element method (5). Propagation of electromagnetic waves through both surfaces of a window is taken into account. The walls of waveguides are assumed inflnitely thin.

Linear and nonlinear light localization within photorefractive photonic superlattices in lithium niobate

Some features of discrete diffraction of light, which manifest themselves in the possibility of its linear and nonlinear localization in one or several waveguide elements, in photorefractive photonic superlattices optically induced in lithium niobate crystals, and in planar optical waveguides based on this material, have been experimentally investigated.

Three-dimensional numerical modeling of photonic integration with dielectric-loaded SPP waveguides

Using full three-dimensional numerical modeling, we demonstrate highly efficient passive and active photonic circuit elements based on dielectric-loaded surface plasmon polariton waveguides (DLSPPWs). Highly confined surface plasmon polariton (SPP) mode having subwavelength cross section allows high level of integration of DLSPPW circuitry. We demonstrate very efficient guiding and routing of SPP signals with the passive waveguide elements such as bends, splitters, and Bragg reflectors, having a functional size of just a few microns at telecommunication wavelengths. Introducing a gain in the dielectric, we have found the requirement for lossless waveguiding and estimated the performance of DLSPPW lossless and active elements. DLSPPW based components have prospective implementation in photonic integrated chips, hybrid optical-electronic circuits, and lab-on-a-chip applications.

Optical waveguide properties of single indium oxide nanofibers

The luminescence and waveguide properties of single In2O3 nanofibers were investigated by means of scanning near-field optical microscopy. The nanofibers showed spatially uniform emission intensity in photoluminescence (PL) images. This emission is associated with a PL emission band centered at ~630 nm. We found that this PL light is propagated through the nanofiber over a distance of several hundreds of micrometers. By measuring the PL intensity for different propagating distances, the optical loss of single nanofibers was evaluated. Waveguiding behavior for incident light with different wavelengths in the visible region was also observed. These results indicate that In2O3 nanofibers can be used as good waveguide elements for integrated photonic applications.

HYBRID ARRAY ANTENNA FOR BROADBAND MILLIMETER-WAVE APPLICATIONS

A hybrid array configuration suitable for wideband millimeter-wave applications is presented in this work. The proposed structure is based on the use of circular waveguide elements electromagnetically coupled trough circular apertures to a stripline distribution network. The adopted excitation mechanism avoids the use of transition components generally reducing the overall antenna efficiency. Simulated and measured results on a Ka-band prototype are discussed to prove the wideband radiation behavior.

New Optical Waveguide Design Based on Wavefront Matching Method

We have studied the wavefront matching (WFM) method, which synthesizes optimum waveguide patterns from the desired characteristics, and demonstrated its feasibility. In this paper, we expand this method to create optimum waveguide shapes with low-loss and low-wavelength dependence in waveguide lenses, Y-branches, and waveguide crossings. We describe the design procedures for each waveguide element and report the experimental results as proof of concept. The measured results agree well with our design requirements, and the waveguide patterns designed by the WFM method exhibit better characteristics than the reference patterns.

Method for synthesis of wideband multimode waveguide elements

We propose a modification of the iterative method for synthesis of waveguide mode converters, which allows obtaining various elements of microwave transmission lines with a wide operating frequency band. The efficiency of the synthesis is illustrated by the calculated waveguide components. This method makes it possible to synthesize converters with significantly improved characteristics, e.g., a converter of the TM0,1 mode to the rotating TE3,1 mode, a converter of the TM0,1 to the TE1,1 mode, a converter of the TE1,1 mode of a smooth waveguide to the HE1,1 mode of a corrugated waveguide, and a waveguide 90° bend for the TE1,1 mode.

Millimeter-Wave Transition From Waveguide to Two Microstrip Lines Using Rectangular Patch Element

A millimeter-wave transition from a waveguide to two microstrip lines and the design methodology are proposed. A rectangular patch element in a short-terminated waveguide is analyzed by the cavity model of a patch antenna and the dyadic Green's function of the waveguide. The analysis points out that the rectangular patch element has an optimum width for wideband, which only has the function of the broad wall width of the waveguide. The transition also works as a divider. A numerical investigation of a transition having two microstrip lines validates the analytical model in terms of wideband, and indicates that the distance between the two microstrip lines has an optimum length for suppressing higher order modes. A prototype transition exhibits an insertion loss of 0.5 dB from 76 to 77 GHz, and a bandwidth of 6.9% (5.29 GHz) for the reflection coefficient below -15 dB for the waveguide port

Design of compact CPW bandpass filters with wide stopband

AbstractTwo compact bandpass filters composed of the lumped elements in various coplanar waveguide (CPW) forms have been presented in this study. The filters were designed to operate at the frequency of 2.45 GHz. The behaviors of these filters can be simulated by the equivalent lumped‐element circuit models with each element realized by the corresponding CPW discontinuity. Simulation and measurements were found to be in good agreement. Most attractive of all, the improved‐design filter has achieved about a 363% (9.04 GHz) stopband bandwidth under a 20 dB out‐of‐band rejection, and the measured passband's minimum insertion loss is around −1.24 dB with 10.84% 3‐dB bandwidth. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 973–976, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22299

Design concept of multi-band antenna with resonant circuit on PCB

Multi-band operation of an internal antenna for mobile phones is achieved by using a practically simple matching circuit constructed on a PCB. The matching circuit consists of a coplanar waveguide and lumped elements on a PCB. Simulation is conducted to verify the new idea of generating the multi-band operation, and the performance of the antenna is measured.

Broadband/Multiband Conformal Circular Beam-Steering Array

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A new approach for a broadband/multiband conformal circular beam-steering array is presented with both theory and experimental data. The array is low-profile, suitable for conformal mounting on a platform. It has an omnidirectional coverage with a unidirectional beam that aims at a moderate directivity of 5 to 15 dBi. It consists of a center driven element and parasitic surface waveguide elements symmetrically positioned in the periphery, for electronic beam steering and beam forming to enhance RF connectivity and/or spectral efficiency. This array can achieve ultrawideband multiband performance and low-profile conformability unattainable by conventional array approaches. In addition, its cost is estimated to be an order of magnitude lower than that of conventional beam-steering arrays. Breadboard and brassboard development efforts for the array have essentially achieved a bandwidth of 1.0–2.5 GHz. A larger bandwidth is feasible since its driven element has achieved a continuous 10:1 bandwidth, and since the surface waveguide elements could achieve a multioctave bandwidth similar to the broadbanding path from the Yagi-Uda array to the LP array. </para>

A novel wavelength dispersive device with a dispersive element based on staircase-like straight and parallel arrayed waveguides

We propose a new type of arrayed waveguide grating (AWG) multiplexer/demultiplexer based on modified group refractive index. This device is composed by an array of straight and parallel waveguides of equal length and each waveguide consist of two sections with different width. The length of the two sections are changed from a waveguide to the adjacent one following a linear dependence resulting in a wavelength dispersive waveguide array. An example of the device design for silicon-on-insulator (SOI) platform is provided and numerical simulations have been carried out for various arrayed waveguide parameters. We demonstrate that the group index modification can be used for tailoring device dispersion properties, and that it can also result in new dispersion characteristics predicted numerically not observed in conventional AWGs. Additional advantages are that the demultiplexer does not necessarily require bending waveguide sections as in a conventional AWG (de)multiplexers, and thus yields highly compact devices with potentially very low insertion loss. Channel spacing of 1 nm have been predicted for sub-micron waveguides sizes. In this paper it is also proposed a novel wavefront converter based on waveguide array lens-like element with waveguides broadened sections. Numerical results for different input/output geometries are analized.

Microwave High T C Superconductor MEM Switch-Based Circuits–the Current State-of-the-Art–Design and Performance Considerations

A summary of the current state of the art in MEM switches using high T C superconducting transmission line elements is presented. The most significant advantages of the MEM technology are the low mass and volume of the implemented devices. On the other hand one of the principal drawbacks of the room temperature MEM rf-switches are their losses. These are primarily resistive losses in the waveguide structure and contacts and are large due to the dimensions required (on the order of 100 μm wide by 3μm thick). This places serious limitations on their use in noise loss sensitive applications. The use of superconductors for the waveguide elements in MEM switches can reduce these losses very significantly (several orders of magnitude are not unusual in devices with identical dimensions). Adding a high dielectric constant insulator to the switch can also help shrink the necessary dimensions or extend the low frequency response of the switch.

Silicon-on-insulator irregular waveguide mode converters

Irregular waveguide elements in a silicon-on-insulator platform that allow new device concepts are introduced. Specific designs are achieved using a multiresolution optimization strategy where the waveguide width is varied in stepwise increments. Simulation results are given for high-efficiency waveguide mode converters, power splitters, and waveguide transitions operating at 1.55 microm. The degrees of freedom available permit these functions and small dimensions, making these devices candidates for optical integrated circuits.