Conventional Metallic Waveguides Research Articles

Low-Loss Gap Waveguide Transmission Line and Transitions at 220–320 GHz Using Dry Film Micromachining

This article presents a novel microfabrication technique to manufacture gap waveguide (GW) components operating at submillimeter-wave (sub-mmWave) frequency range. The conventional metal waveguide component manufacturing has a low resolution and low throughput and is not suitable for applications above 100 GHz. The micromachining techniques have matured and applied in various applications. Several micromachining techniques have been developed to address the specification requirements of different fields. Conventional micromachining techniques suffer from fabrication issues, such as nonvertical sidewall, nonuniform surface, and time-consuming fabrication process. The proposed dry film photoresist offers a significant amount of benefits, such as fewer processing steps, reduced production cost, and shorter prototyping time over existing micromachine techniques. To validate the proposed fabrication method, SUEX dry film photoresist is used to demonstrate three GW transmission lines. Different transitions from rectangular waveguide (RW) to GW have also been designed to characterize the newly fabricated GW components with a standard measurement setup. All the designed and fabricated devices operate from 220 to 320 GHz. The fabricated devices showed a good agreement with the simulation result over this frequency band and the measured average insertion losses were in the order of 0.048 and 0.075 dB/mm for groove GW and ridge GW, respectively. Thus, dry film photoresist provides fabrication precision of the structures and consequently opens the path for low-cost fabrication of high-frequency waveguide components.

Reconfigurable Millimeter-Wave Components Based on Liquid Crystal Technology for Smart Applications

This paper presents recent development of tunable microwave liquid crystal (LC) components in the lower millimeter wave (mmW) regime up to the W-band. With the utilization of increasing frequency, conventional metallic waveguide structures prove to be impractical for LC-based components. In particular, the integration of the electric bias network is extremely challenging. Therefore, dielectric waveguides are a promising alternative to conventional waveguides, since electrodes can be easily integrated in the open structure of dielectric waveguides. The numerous subcategories of dielectric waveguides offer a high degree of freedom in designing smart millimeter wave components such as tunable phase shifters, filters and steerable antennas. Recent research resulted in many different realizations, which are analyzed in this paper. The first demonstrators of phased array antennas with integrated LC-based phase shifters are reviewed and compared. In addition, beam steering with a single antenna type is shown. Furthermore, the possibility to realize tunable filters using LC-filled dielectric waveguides is demonstrated.

Introduction to Photonics: Principles and the Most Recent Applications of Microstructures.

Light has found applications in data transmission, such as optical fibers and waveguides and in optoelectronics. It consists of a series of electromagnetic waves, with particle behavior. Photonics involves the proper use of light as a tool for the benefit of humans. It is derived from the root word “photon”, which connotes the tiniest entity of light analogous to an electron in electricity. Photonics have a broad range of scientific and technological applications that are practically limitless and include medical diagnostics, organic synthesis, communications, as well as fusion energy. This will enhance the quality of life in many areas such as communications and information technology, advanced manufacturing, defense, health, medicine, and energy. The signal transmission methods used in wireless photonic systems are digital baseband and RoF (Radio-over-Fiber) optical communication. Microwave photonics is considered to be one of the emerging research fields. The mid infrared (mid-IR) spectroscopy offers a principal means for biological structure analysis as well as nonintrusive measurements. There is a lower loss in the propagations involving waveguides. Waveguides have simple structures and are cost-efficient in comparison with optical fibers. These are important components due to their compactness, low profile, and many advantages over conventional metallic waveguides. Among the waveguides, optofluidic waveguides have been found to provide a very powerful foundation for building optofluidic sensors. These can be used to fabricate the biosensors based on fluorescence. In an optical fiber, the evanescent field excitation is employed to sense the environmental refractive index changes. Optical fibers as waveguides can be used as sensors to measure strain, temperature, pressure, displacements, vibrations, and other quantities by modifying a fiber. For some application areas, however, fiber-optic sensors are increasingly recognized as a technology with very interesting possibilities. In this review, we present the most common and recent applications of the optical fiber-based sensors. These kinds of sensors can be fabricated by a modification of the waveguide structures to enhance the evanescent field; therefore, direct interactions of the measurand with electromagnetic waves can be performed. In this research, the most recent applications of photonics components are studied and discussed.

Electromagnetic Wave Propagation Through Air-Core Waveguide With Metamaterial Cladding

Metamaterial-based waveguides offer unusual properties compared to conventional metallic and dielectric waveguides. We experimentally investigate a novel waveguide with an air-core and a cladding formed of slotted cylinder resonators, which can have an electric and/or a magnetic response at terahertz (THz) frequencies, depending on their orientation and the polarization of the light, and through these confine radiation to the hollow core. Various interesting phenomena are observed in the experiments, including confinement of radiation through the electric response as well as the magnetic response, spatial dispersion, total internal reflection with refractive indices below 1, and slit resonances. Such waveguides promise future novel THz applications, such as refractive index sensors or dispersion management.

Recent advances in theory and applications of substrate-integrated waveguides: A review

The use of substrate integrated waveguides (SIW) for microwave and millimeter wave integrated components has increased dramatically over the last decade. They mimic the performance of conventional metallic waveguides and they are fabricated using printed circuit boards using the top and bottom metallisation with two rows of vias forming the side walls. This creates a low profile, compact, and light weight alternative to conventional metallic waveguides, and they allow a direct interconnection with printed circuit boards and active components. This paper reviews the fundamental theory, documents the research that has been performed over the past decade, and summarises progress up to the recent state-of-the-art including novel SIW structures for passive circuits and antennas as well as new applications for reconfigurable and printed circuits using SIW technology.

Design and Analysis of Rectangular Conducting Slots Based Substrate IntegratedWaveguide

The demand for high performance, high gain, low cost, easy to fabricate and compact antennas for telecommunication and different applications has rapidly increased at microwave and higher frequencies. Substrate Integrated Waveguides (SIW) is planar in nature so it can be fabricated on planar circuits like Printed Circuit Boards (PCB) and can be integrated with other planar transmission lines like microstrips.Substrate Integrated Waveguides (SIW) keep the low loss property of their conventional metallic waveguides and are extensively used as interconnection in high speed circuits, filters, directional couplers, antennas. In this paper a Substrate Integrated Waveguide based antenna using rectangular slots is proposed and its integration with Microstrip line. ComsolMultiphysics is used for simulation results.

Photonic Crystal-Structures for THz Vacuum Electron Devices

The technology of photonic crystals (PhCs) is investigated here to improve the performance of THz vacuum electron devices. Compared with conventional metallic waveguides, the PhC arrangement alleviates typical issues in THz vacuum electron tubes, i.e. difficult vacuum pumping process and assembling, and improves the input/output coupling. A slow-wave structure (SWS) based on a corrugated waveguide assisted by PhC lateral walls and the efficient design of a PhC coupler for sheet-beam interaction devices are demonstrated. Based on the proposed technology, a backward-wave oscillator (BWO) is designed in this paper. Cold parameters of the novel PhC SWS as well as 3-D particle-in-cell simulations of the overall BWO are investigated, obtaining more than 70-mW-peak output power at 0.650 THz for beam voltage of 11 kV and beam current of 6 mA.

Dual-channel rainbow trapping of terahertz surface plasmon-polariton in graded metallic grating structures

We numerically show that slowing down and even stopping Terahertz waves can be achieved in a one-dimensional graded-grating-depth metal structure. Since the dispersion curves are dependent on the graded grating depths, waves of different wavelengths can be localized at different spatial positions of the structure, leading to rainbow trapping. Especially, dual-channel trapped rainbows with different modes can be realized in a single structure as two bands appear in the dispersion curve within the analyzed frequency range. In addition, due to the fact that the bands with different order modes do not overlap one another in the frequency domain, for each mode, its single-mode propagation can be available by properly choosing operation frequency. Such a phenomenon never happens for conventional dielectric or metal waveguides.

Design of a 45$^{\circ}$-Inclined SIW Resonant Series Slot Array Antenna for $Ka$-Band

In this letter, a new type of resonant series slot array antenna for Ka-band for 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> linear polarization (LP) is described. Sixteen radiating slots, tilted at an angle of 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , are separated by one-half guided wavelength due to use of the alternating inductive and capacitive load slot pairs. These alternating reactance slot pairs allow this novel antenna to achieve impedance matching, uniform field excitation, and suppression of grating lobes simultaneously. The antenna is designed and fabricated using substrate integrated waveguide (SIW) technology to overcome the drawbacks associated with conventional metallic waveguide antennas. The measured impedance bandwidth, maximum gain, and sidelobe levels are 2.7%, 15.64 dBi, and 15.36 dB, respectively, at the design frequency. The measured data are in agreement with the theoretical calculations and demonstrate the validity of the design technique for the proposed antenna structure.

Wide Band Metallic Waveguide With In-Line Dielectric Rods

Conventional rectangular metallic waveguides are seldom used at frequencies higher than twice the cutoff frequency because of higher mode propagation. Single-mode propagation is available for a metallic waveguide with arrayed dielectric rods at the center of the waveguide in the frequency under twice the cutoff frequency region using the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode, and in the frequency over twice the cutoff frequency region using the TE2o mode. If the metallic waveguide and dielectric loss tangent are assumed to be WR-90 (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ap6.55 GHz) and 3times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , respectively, then the attenuation constants are smaller than 0.25 dB/m in the frequency range from 7 to 10 GHz, 15 to 16.5 GHz, and from 17.2 to 21 GHz.

Low-loss terahertz ribbon waveguides

The submillimeter wave or terahertz (THz) band (1 mm-100 microm) is one of the last unexplored frontiers in the electromagnetic spectrum. A major stumbling block hampering instrument deployment in this frequency regime is the lack of a low-loss guiding structure equivalent to the optical fiber that is so prevalent at the visible wavelengths. The presence of strong inherent vibrational absorption bands in solids and the high skin-depth losses of conductors make the traditional microstripline circuits, conventional dielectric lines, or metallic waveguides, which are common at microwave frequencies, much too lossy to be used in the THz bands. Even the modern surface plasmon polariton waveguides are much too lossy for long-distance transmission in the THz bands. We describe a concept for overcoming this drawback and describe a new family of ultra-low-loss ribbon-based guide structures and matching components for propagating single-mode THz signals. For straight runs this ribbon-based waveguide can provide an attenuation constant that is more than 100 times less than that of a conventional dielectric or metallic waveguide. Problems dealing with efficient coupling of power into and out of the ribbon guide, achieving low-loss bends and branches, and forming THz circuit elements are discussed in detail. One notes that active circuit elements can be integrated directly onto the ribbon structure (when it is made with semiconductor material) and that the absence of metallic structures in the ribbon guide provides the possibility of high-power carrying capability. It thus appears that this ribbon-based dielectric waveguide and associated components can be used as fundamental building blocks for a new generation of ultra-high-speed electronic integrated circuits or THz interconnects.

Metal wires for terahertz wave guiding

Sources and systems for far-infrared or terahertz (1 THz = 10(12) Hz) radiation have received extensive attention in recent years, with applications in sensing, imaging and spectroscopy. Terahertz radiation bridges the gap between the microwave and optical regimes, and offers significant scientific and technological potential in many fields. However, waveguiding in this intermediate spectral region still remains a challenge. Neither conventional metal waveguides for microwave radiation, nor dielectric fibres for visible and near-infrared radiation can be used to guide terahertz waves over a long distance, owing to the high loss from the finite conductivity of metals or the high absorption coefficient of dielectric materials in this spectral range. Furthermore, the extensive use of broadband pulses in the terahertz regime imposes an additional constraint of low dispersion, which is necessary for compatibility with spectroscopic applications. Here we show how a simple waveguide, namely a bare metal wire, can be used to transport terahertz pulses with virtually no dispersion, low attenuation, and with remarkable structural simplicity. As an example of this new waveguiding structure, we demonstrate an endoscope for terahertz pulses.

Guided Modes in a Two-Dimensional Photonic Crystal WaveguideConsisting of Nearly-Free-Electron Metals

Guided modes in a two-dimensional photonic crystal consisting ofnearly-free-electron metals are considered. To avoid time-consumingconvolution, modified time-stepping formulae are used in afinite-difference time-domain approach. The guided modes in the metallicphotonic crystal waveguide are related to those in a conventional metallicwaveguide. A cut-off frequency exists, and consequently a mode gap at lowfrequencies exists in the photonic crystal metallic waveguide.

Guided modes in a two-dimensional metallic photonic crystal waveguide

Guided modes in a two-dimensional metallic photonic crystal waveguide are studied. The guided modes in the photonic crystal waveguide are related to those in a conventional metallic waveguide. There exists a cutoff frequency and consequently a mode gap at low frequencies (starting from zero frequency) in the photonic crystal metallic waveguide.

2.5-THz GaAs monolithic membrane-diode mixer

A novel GaAs monolithic membrane-diode (MOMED) structure has been developed and implemented as a 2.5-THz Schottky diode mixer. The mixer blends conventional machined metallic waveguide with micromachined monolithic GaAs circuitry to form, for the first time, a robust, easily fabricated, and assembled room-temperature planar diode receiver at frequencies above 2 THz. Measurements of receiver performance, in air, yield at T/sub receiver/ of 16500-K double sideband (DSB) at 8.4-GHz intermediate frequency (IF) using a 150-K commercial Miteq amplifier. The receiver conversion loss (diplexer through IF amplifier input) measures 16.9 dB in air, yielding a derived "front-end" noise temperature below 9000-K DSB at 2514 GHz. Using a CO/sub 2/-pumped methanol far-infrared laser as a local oscillator at 2522 GHz, injected via a Martin-Puplett diplexer, the required power is /spl ap/5 mW for optimum pumping and can be reduced to less than 3 mW with a 15% increase in receiver noise. Although demonstrated as a simple submillimeter-wave mixer, the all-GaAs membrane structure that has been developed is suited to a wide variety of low-loss high-frequency radio-frequency circuits.

Method of projection operators for photonic band structures with perfectly conducting elements

We introduce the method of projection operators based on plane-wave expansion to compute photonic band structures in periodic media containing perfectly conducting elements. Eigenfunctions of a unit configuration potential generate suitable projection operators in the form of a set of eigenvectors in the Fourier domain. By simply applying a projection operator onto a proper subspace, a quadratic or cubic eigensystem for finitely conducting media can be transformed into an ordinary symmetric eigensystem in the limit of perfect conductors. The procedure is equivalent to finding solutions of wave equations under the condition that the electromagnetic fields are entirely zero inside periodic perfect conductors. The methodology developed here, in fact, can be viewed as a generalization of the conventional metal waveguide or cavity theory. The method is numerically handy, fast, and readily extendible to general metallodielectric photonic crystals. As examples, we present photonic band structures in two-dimensional metal and metallodielectric cylinder structures.

Properties of high-Tc superconducting circular waveguides with Meissner boundary

The propagation properties of the TE-modes in a high-temperature superconducting circular waveguide using the Mei\ner boundary conditions on the wall are presented for the first time. The results show that now the normalized cutoff parameterk c R, (whereR is the radius of the superconducting circular waveguide andk c the cutoff wavenumber,) is dependent on the radius unlike conventional metallic circular waveguide whose normalized cutoff parameterk c R is a constant for a given mode and the filled dielectrics. Instead of TE11-mode now TE01 mode becomes the dominant mode and the normal component of magnetic field for the dominant mode is not equal to zero on the wall. Other unique results of high-T c superconducting circular waveguides are illustrated, too.

TM Modes In Oversized Planar Metallic Waveguides (Short Paper)

The propagation properties of transverse magnetic (TM) and hybrid modes in plane and circular metallic waveguides are considered when their dimensions are great with regard to the wavelength. When the oversizing is not too great, the behavior is the same as those of conventional metallic waveguides. For high frequencies (greater oversizing), we describe an unexpected bebavior for these modes. The aim of this work is mainly to derive asymptotic expressions useful for the design of for infrared (FIR) waveguide lasers.

Power handling capability of dielectric-coated, metallic, hollow waveguides for CO 2 laser light

A theoretical analysis has been carried out to evaluate the power handling capability of hollow waveguides for CO 2 laser light. Dielectric-coated metallic waveguides are shown to transmit much higher powers than conventional metallic waveguides.

LOSS COMPARISONS OF INSULAR GUIDE AND MICROSTRIP MILLIMETRE ANTENNA ARRAY FEEDERS

ABSTRACT The use of printed antenna techniques at millimetre wavelengths to create planar linear travelling wave antennas is commonly considered to be inhibited by the microstrip feeder loss and the alternate use of low loss dielectric feeders is thus attractive. In this investigation an additional source of unwanted loss is considered and a complete assessment, more favourable to microstrip, emerges. The fields of an insular guide antenna feeder are computed by a mode matching method to provide accurate data for the guide attenuation and also the launcher radiation loss when the insular guide is connected to a conventional rectangular metal waveguide using a horn launcher transition. This latter analysis is based both on a chopped surface wave distribution method and an alternative variational method. Similar loss data is computed for microstrip antenna feeders using existing theories and some experimental data presented. A comparison of total unwanted losses for both types of feeders establishes that mi...