Groove Waveguide Research Articles

Design and analysis of sensor structure based on ultrasonic temperature measurement

Abstract Based on the principle of ultrasonic temperature measurement, this paper designs the structure of a waveguide rod sensor with a reflective groove. Using multi-physics field simulation software to conduct acoustic thermal coupling parametric simulation analysis on six different high melting point materials, we obtain the curve functions of the relationship between sound velocity and temperature for the six materials and verify the feasibility of ultrasonic temperature measurement using waveguide rods. Analysis shows that the sensitivity of six alloys to temperature changes is as follows: Ti6Al4V titanium alloy > α-Al2O3 > Inconel693 nickel-based alloy > ThO2 > Tungsten-rhenium alloy > Ta8W2Hf. At the same time, three different shapes of waveguide rods were designed: single groove waveguide rod, multi-zone waveguide rod, and spiral waveguide rod to analyze the impact of temperature measurement accuracy. The research results have important theoretical guidance significance for solving the problem of temperature measurement in high-temperature environments.

Design and analysis antennas of transverse polarization on the dielectric waveguide

This paper addresses the issue of constructing millimeter band antennas using dielectric waveguide structures. A new type of linear antenna, incorporating metal pins on the side walls of the grooved dielectric waveguide, is proposed for generating polarization perpendicular to the waveguide axis. However, these antennas suffer from the drawback of cross-polarized radiation in directions close to the waveguide axis. To overcome this limitation, a modified antenna design with transverse polarization is introduced, featuring a closed groove waveguide with a longitudinal slot at the top of the wall. The paper provides a comparison between two types of dielectric waveguide antennas: first, waveguide antenna with grooves in the dielectric which results in longitudinal polarization, and second, waveguide antenna with quarter-wavelength pins which results in transverse polarization. Electrodynamic modeling data are provided to demonstrate the effectiveness of the proposed antennas for satellite, 5G antenna, and radar applications. Finally, an antenna of quarter-wavelength pins is proposed with a frequency of 39 GHz, a gain of 19.8 dBi, and a width of the radiation pattern of 3.2∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }$$\\end{document}, and a sidelobe level (SLL) of -13.3 dB has been achieved.

A novel SIGGW dual post band-pass filter for 5G millimeter-wave band applications with a transmission zero

Integration of planar circuits been considered a credible technique for low-cost mass production of microwave and millimeter-wave circuits and systems. For the first time, in this research a dual-post band-pass filter is designed and simulated in a three-layer substrate integrated gap groove waveguide (SIGGW) for 5G millimeter-wave frequency band applications. The filter includes 12 posts (6 times 2). Also, the structure facilitates to use resonant posts and so we can design the posts to add a transmission zero in lower rejection band. The design theory algorithm and its limitations are investigated based on the circuit model of filter. The results shows that FBW of 5% and a lower band transmission zero for the proposed 12 posts filter. Also, the results are verified by simulation using CST. According to the results, the proposed filter is a good option for Ka-band applications and can be used as the building block for suppressing the LO leakage that is commonly used for up-converting the 5G signal to Ka band.

Research on sensing characteristics of third-order runway series symmetric microring resonator based on hybrid plasma waveguide and metal insulator metal.

In this paper, a high-sensitivity refractive index sensor based on a hybrid plasma waveguide and metal-insulator-metal waveguide combined third-order runway series mosaic microring resonator is proposed. In this structure, a GaAs waveguide ring surrounds a gold waveguide ring in the middle, and the innermost layer is a disk made of gold material. The outer groove waveguide is composed of GaAs-air-alloy, and the inner groove waveguide is made of the Gold-Air-Gold material disc. By filling different substances in the groove, the change of refractive index will affect the optical signal strength of the output spectrum. The finite element method simulates the transmission spectrum and electric field distribution of the sensor structure. The amplitude coupling coefficient and attenuation factor affecting the resonator's performance are analyzed, and the structural parameters of the slot waveguide are optimized. The numerical simulation results show that the sensor quality factor of this structure is 1.54 × 104 , the sensitivity is 1.2 × 103 nm/RIU which is about 1.5 times higher than that of the Si ring with the same structure, the detection limit can reach 8.1892 × 10-7 RIU, and the free spectral range can reach 109 nm. Compared with the traditional microring structure, this microring has higher design freedom and free spectral range and is more suitable for producing biosensors with high sensitivity, low detection limit, and multi-parameter measurement.

Design and Measurement of Power-Coupling Structure for Parallel Operation of Two Folded Groove Waveguides

In this article, we design an input–output energy-coupling method for the parallel operation of two terahertz folded groove waveguides (FGWs)—a conversion from TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode to two modes of TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> . The mode is first converted in the H-plane of standard waveguide WR4 from TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> to TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , and which is then subsequently converted into two TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes through a Y-branch step impedance transformation. The novel energy-coupling structure was manufactured and measured so that the S parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{{11}}$ </tex-math></inline-formula> is less than −10 dB in the frequency range of 170–260 GHz. And in the frequency range of 190–250 GHz, the simulated and measured transmission coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{{21}}$ </tex-math></inline-formula> tends to be consistent. Moreover, using the coupling structure, the dispersion characteristics of the parallel operation of two FGWs was measured.

A Novel Slow-Wave Structure—Coupled Double Folded Waveguide Operating at High-Order TM₂₀ Mode for Terahertz TWT

A slow-wave structure named coupled double folded waveguide (CDFW) is proposed for traveling wave tube operating at terahertz region. Its electromagnetic characteristics and beam-wave interactions are presented in this letter. This structure, evolved from a single folded double ridge groove waveguide (DRGW) by intersecting the groove along its transverse direction, can operate at high-order TM₂₀ resulting in increased horizontal dimension. Furthermore, this novel CDFW can interact with two pencil beams and have high beam-wave coupling impedance, which is beneficial to output high power at terahertz band. The proposed CDFW, when applying a dynamic velocity taper technique, can produce an output power of 210 W at 340 GHz with a 3-dB bandwidth of 13 GHz, and it is 80 W higher than a folded DRGW with a single beam at the same condition, when the beam voltage and beam current are 27.98 keV and 0.25 A, respectively.

Parallel Arrangement Folded Double-Ridge Groove Waveguide for High-Power Terahertz Traveling-Wave Tube

In this article, a terahertz traveling-wave tube (TWT) with two identical folded double-ridge groove waveguides (DRGWs) operated in parallel is presented. Driven by a sheet electron beam in each DRGW TWT allows a higher beam current, and hence higher output power can be achieved. A magic T based on DRGW is designed as the input and output power couplers for this novel TWT. The performance of the magic T is optimized using Chebyshev impedance transforming structures. The simulated reflection and transmission coefficients of the whole tube with magic T in the operating frequency range of 330–350 GHz are less than −20 and −75 dB, respectively. In addition, a particle in cell (PIC) simulation of the beam–wave interactions involving the two sheet electron beams predicted an output power of 160 W at 340 GHz with a 3-dB bandwidth of 11 GHz when a beam of 27.68 keV in energy and 0.25 A in total current is used.

Investigation of Sine Groove Waveguide Slow Wave Structure for Terahertz Traveling Wave Tube

A novel sine groove waveguide slow wave structure (SGW-SWS), originated from the sine waveguide (SW), is proposed for a wideband terahertz (THz) traveling wave tube (TWT). SGW-SWS not only has high interaction impedance in a relatively wide frequency band, but also has a wide beam tunnel. In addition, it can be fabricated using the Nano-Computer Numerical Control (CNC) milling techniques. The high-frequency simulation results show that, under the same dispersion, the passband of SGW-SWS is 23 GHz wider than that of SW-SWS, and the average interaction impedance of SGW-SWS is higher than that of SW-SWS in the whole passband. And the transverse dimension of beam tunnel is independent of the dispersion characteristics of SGW-SWS, so the beam current can be further increased by enlarging the size of beam tunnel. Moreover, the particle-in-cell (PIC) simulation results reveal that the saturated power and electronic efficiency of SGW-TWT in the frequency range of 201–260 GHz are more than 84.9 W and 2.72%, respectively, when the operating voltage is 20.8 kV and the beam current is 150 mA.

A Gap Waveguide-Based Compact Rectangular Waveguide to a Packaged Microstrip Inline Transition

In this paper two different simple to design and easy to manufacturing transitions from a microstrip to rectangular waveguide based on ridge and groove gap waveguides are studied. The first one is based on a combination of a groove and ridge gap waveguide. In this case, the microstrip substrate occupies the whole bottom metallic housing block, namely, the transition and the gap between the bed of nails and the lid; therefore, it does not require any substrate shaping. Nevertheless, the transition needs to replace groove waveguide by ridge gap waveguide sections to avoid higher-order mode excitation. In the second approach, based on only a groove gap waveguide, the substrate is shaped to be only in the microstrip section, that is, outside the bed of nails area. This leads to a simplification of the design procedure. Prototypes of both transitions have been characterized, showing good agreement with the simulations taking into account the manufacturing tolerances. Performance comparable to the state-of-the-art in this frequency band has been achieved.

Dual-channel linear emitter based on a semi-open groove waveguide

This paper describes the design of a dual-channel semi-open groove waveguide and a methodology for designing such structures. A method for forming a negative phase shift by shortening the lengths of the radiating inhomogeneities is demonstrated. Simulation experiments were performed using the Ansys HFSS package.

Investigation of angular log-periodic folded groove waveguide slow-wave structure for low voltage Ka-band TWT

In this paper, a novel angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has been investigated theoretically and experimentally for application in Ka-band traveling-wave tubes (TWTs). The dispersion relation for the ALFGW is derived analytically, and the dispersion characteristics are calculated for a Ka-band design. The designed SWS is fabricated using oxygen-free-copper that is silver electroplated. The measured cold-test parameters show good agreement with the simulation results, with S21 varying from −2.7 dB to −4.8 dB and S11 better than −13.6 dB over the frequency range of 30–38 GHz. Simulations of beam–wave interactions using a 4850 V and 0.4 A sheet beam with a high aspect ratio of 28:1 indicate an output power of 128 W, corresponding to a maximum gain and electronic efficiency of 18.1 dB and 6.6%, respectively. Due to the log-periodic form, a higher output power, higher efficiency, wider bandwidth, and lower operating voltage are achieved as compared to a TWT based on the conventional folded groove waveguide (FGW) SWS. These results show that the proposed ALFGW SWS has good potential for application in relatively high-power wideband TWTs.

Design and Fabrication of Wideband Millimeter-Wave Directional Couplers With Different Coupling Factors Based on Gap Waveguide Technology

A class of wideband directional couplers suitable for achieving different coupling levels are proposed in this paper. The proposed couplers have been implemented using the double-layer groove gap waveguide at the millimeter-wave frequency range. They are composed of two parallel groove gap waveguide parts placed on top of each other in such a way that the coupling between the two waveguide sections can be achieved via the coupling structures placed in the common wall. Usually, the coupling layer consists of two rows of holes and depending on the number of holes the coupling levels can be controlled. The manifest and applicable property of the proposed directional coupler is that the coupling level can be simply changed using the different coupling layers without changing the top and bottom groove waveguides and transitions. As another significant advantage of the proposed coupler, there is no requirement of good electrical contact among different metallic parts of the structure, which considerably simplifies the manufacturing processes and mechanical assembly at millimeter-waves applications. For verification purpose, three sample couplers with coupling levels of 10, 20, and 30 dB have been designed, fabricated, and measured. To make the device accessible and measurable using the standard rectangular waveguides, two types of transitions from the groove gap waveguide to standard WR-15 are designed. The simulation and experimental results are in good agreement and show that the proposed couplers have large bandwidth for return loss level of 20 dB, coupling level of 10±1, 20±1, and 30±1 dB, and isolation level of 30, 35, and 40 dB over the desired frequency band of 50-70 GHz. The proposed directional couplers can be used as good candidates at millimeter-wave frequencies for probing and the design of compact integrated microwave circuits and systems, such as antenna array feeding networks.

Investigation of Ridge-Loaded Folded Rectangular Groove Waveguide Slow-Wave Structure for High-Power Terahertz TWT

A novel slow-wave structure (SWS) called ridge-loaded folded rectangular groove waveguide has been proposed for developing the wideband high-power terahertz (THz) traveling-wave tube (TWT). A new kind of attenuator suitable for this kind of SWS has also been proposed, which can successfully suppress the self-excited oscillations and keep the harmonics to a very low level. An input and output waveguide transition structure which is appropriate for this new kind of SWS is put forward. It can be found from the simulation results that the ridge-loaded SWS can enhance the electric field intensity in the electron beam tunnel so that the average interaction impedance of this ridge-loaded folded rectangular groove waveguide SWS at 0.34 THz is 30.1% higher than that of the folded rectangular groove waveguide SWS. Moreover, the particle-in-cell simulation results reveal that with the sheet electron beam parameters of 27 kV and the 250 mA, the average output power, the gain, and the electronic efficiency of the ridge-loaded folded rectangular groove waveguide TWT at the frequency of 0.34 THz can reach 39 W, 26.99 dB, and 0.59%, respectively. Therefore, the ridge-loaded folded rectangular groove waveguide SWS should be considered as a promising slow-wave circuit for high-power wideband THz radiation source.

Channel hybrid plasmonic modes in dielectric-loaded graphene groove waveguides

Dielectric-loaded graphene groove waveguide (DLGGW) structure is designed and the channel hybrid plasmonic modes are investigated in the terahertz domain. The proposed structure could effectively suppress the mode field confinement with relative low transmission loss due to the strong coupling between the dielectric mode and the channel graphene plasmonic mode. A typical propagation length is 37.8μm, and optical field is confined into an ultra-small area of approximately 52μm2 at 1.5 THz. By changing the size of cylinder, the angle of the graphene groove, and the thickness of dielectric coating layer, the compromise between confinement and loss could be balanced flexibly. Unlike plasmons in noble metals, the propagation loss in DLGGW structure could be tuned by the graphene conductivity. Moreover, because of the imaginary part of graphene conductivity being positive, the proposed waveguide can propagate in a large terahertz frequency regime. This waveguide shows great applications in optical integrated devices, such as detectors, sensors and spectroscopy.

ON THE FEASIBILITY OF USING A GROOVE WAVEGUIDE AS A DISPERSIVE ELEMENT IN A PASSIVE MICROWAVE POWER COMPRESSOR

In this paper, we discuss the numerical simulation of electromagnetic pulse compression in a waveguiding section containing a part of an open groove waveguide. It is shown that the total loss in such waveguiding section in the millimeter wave band could be less than ohmic loss in a closed rectangular waveguide of the same length. The time profile of the input signal has been calculated allowing for the radiation and ohmic loss in the waveguide, thus ensuring that the compressed pulse is shaped as necessary. The obtained results can be applied in the microwave power compressors engineering for millimeter wave band.

Investigation on Sheet Beam Folded V-Shape Groove Waveguide for Millimeter-Wave TWT

In this paper, a novel slow-wave structure (SWS) called folded V-shape groove waveguide SWS is proposed. The high frequency characteristics of this SWS is studied. An input and output waveguide transition structure, which is appropriate for this new kind of SWS is put forward. The transmission loss of the folded V-shape groove waveguide is lower than that of folded rectangular groove waveguide. The dimension of the folded V-shape groove waveguide is larger than that of the folded rectangular groove waveguide at the millimeter waveband, even at terahertz waveband. Based on this kind of SWS, a W-band sheet beam traveling-wave tube is studied, whose beam-wave interaction is calculated by means of the simulation software. The calculation results show that the output power can be over 260 W within 3-dB bandwidth from 84 to 98 GHz, the gain can reach up to 36 dB, and the electron efficiency is 12.33% at the center frequency.

Gap Waveguide Leaky-Wave Antenna

A novel leaky-wave antenna, realized using gap waveguide concept, is here proposed. Both, the feeding structure and the antenna are realized in groove gap waveguide technology, thus simplifying the whole structure. A complete design procedure, starting from a given groove waveguide to the final radiation mechanism, is described in this communication. The results are supported with measurements of a prototype that operates in the X-band. The realized antenna has a gain around 18 dB between 9 and 11.5 GHz, demonstrating the potential of the proposed radiation technology.

A Research of 140‐GHz Folded Rectangular Groove Waveguide Traveling‐Wave Tube

A two-section Folded rectangular groove waveguide (FRGWG) Slow wave structure (SWS) Traveling wave tube (TWT) with large dimension of beam tunnel is studied. Compared with the Folded waveguide (FWG) under the same size parameters conditions, the interaction impedance and center frequency of the FRGWG are higher. The advantage is that a beam tunnel with large dimension can be applied to the FRGWG without the influence caused by signal decrease, reflection and oscillation. The microwave amplification capability based on beam-wave interaction is obtained through the particle-in-cell method. This circuit structure can produce an output power of over 100W ranging from 136 to 142GHz when the operation voltage and beam current are set as 18.4kV and 150mA, respectively, for a 95mm long circuit.

Surface plasmon modes in graphene wedge and groove waveguides

Surface plasmon modes at terahertz-infrared waveband in subwavelength graphene wedge and groove waveguides are investigated, which can be categorized into perfect electric conductor and perfect magnetic conductor symmetric modes with different propagation characteristics. The electromagnetic near-fields are localized strongly in different regions for these two kinds of modes. Moreover, these modes can be interpreted by the folded graphene ribbon modes. The brim width of the waveguides and the Fermi energy of the graphene strongly influence the dispersion and propagation distances of the plasmon modes, which can be used for tuning the plasmon modes in graphene wedge and groove waveguides efficiently.

Nonlocal response in plasmonic waveguiding with extreme light confinement

Abstract We present a novel wave equation for linearized plasmonic response, obtained by combining the coupled real-space differential equations for the electric field and current density. Nonlocal dynamics are fully accounted for, and the formulation is very well suited for numerical implementation, allowing us to study waveguides with subnanometer cross-sections exhibiting extreme light confinement. We show that groove and wedge waveguides have a fundamental lower limit in their mode confinement, only captured by the nonlocal theory. The limitation translates into an upper limit for the corresponding Purcell factors, and thus has important implications for quantum plasmonics.