Dielectric Loading Research Articles

Ultracompact polarization beam splitter based on hybrid plasmonic waveguide

A compact polarization beam splitter (PBS) based on a three-waveguide plasmonic directional coupler was proposed and modeled. The directional coupler comprised two common silicon-on-insulator (SOI) ridge waveguides, with a metal-capped plasmonic SOI waveguide sandwiched between them. The geometrical structure of the three-waveguide directional coupled waveguide was optimized, realizing the phase matching of transverse magnetic (TM) modes but not of transverse electric (TE) modes. The structure and performance of the PBS was optimized using a finite-difference time-domain method. Simulation results showed that the birefringence comparison of TE and TM modes in a hybrid plasmonic waveguide was enhanced using a dielectric loading waveguide to obtain an ultra-compact structure; the final optimized coupling length of the device was 6.1 µm. At the center wavelength of 1.55 µm, the polarization extinction ratio of the TE and TM modes was 34.57 dB and 23.24 dB, and the insertion loss was 0.01 dB and 0.13 dB, respectively.

A Staggered Vane-Shaped Slot-Line Slow-Wave Structure for W-Band Dual-Sheet Electron-Beam-Traveling Wave Tubes.

A staggered vane-shaped slot-line slow-wave structure (SV-SL SWS) for application in W-band traveling wave tubes (TWTs) is proposed in this article. In contrast to the conventional slot-line SWSs with dielectric substrates, the proposed SWS consists only of a thin metal sheet inscribed with periodic grooves and two half-metal enclosures, which means it can be easily manufactured and assembled and has the potential for mass production. This SWS not only solves the problem of the dielectric loading effect but also improves the heat dissipation capability of such structures. Meanwhile, the SWS design presented here covers a -15 dB S11 frequency range from 87.5 to 95 GHz. The 3-D simulation for a TWT based on the suggested SWS is also investigated. Under dual-electron injection conditions with a total voltage of 17.2 kV and a total current of 0.3 A, the maximum output power at 90 GHz is 200 W, with a 3 dB bandwidth up to 4 GHz. With a good potential for fabrication using microfabrication techniques, this structure can be a good candidate for millimeter-wave TWT applications.

Developing wideband antenna based on the metamaterial and dielectric silicon load for terahertz spectrum

Developing wideband antenna based on the metamaterial and dielectric silicon load for terahertz spectrum

Effect of Electric field on Dielectric Loads by Using the Electrode Plates for Exterminating Pests Applications

Effect of Electric field on Dielectric Loads by Using the Electrode Plates for Exterminating Pests Applications

Transformer‐less drive and operation stability analysis of dielectric barrier discharge using a double resonance circuit

AbstractA dielectric barrier discharge load (DBD) with a maintenance voltage of 1.5 kV has been successfully driven stably from a 48 V inverter only by resonance voltage boost and no transformer. The proposed circuit consists of a two‐stage resonant circuit. The circuit operation is investigated using both prototyping measurement and circuit simulation, which shows that despite the high Q value, the design margin and operating stability of the circuit are extremely wide. It is found that this operational stability can be explained by considering the impedance characteristics of DBD. We believe that the circuit is suitable for driving discharge loads such as DBD in practical applications.

Microwave meta‐absorber by using Smith Chart

AbstractAs a representative technique in electronics, the Smith Chart provides a fast, less‐computation, and graphical approach to solve the problems related to impedance matching. In this paper, we transplanted the Smith Chart into the design and analysis of a microwave metamaterial absorber (meta‐absorber) to develop an analytical and graphical approach for impedance matching of electromagnetic wave absorption. Before the structural design, four traces on the Smith Chart plane from the load to arrive at the impedance matching point (the center of the Smith Chart) can be graphically found to obtain perfect absorption. Then, we have designed four impedance matching circuit networks made of resistance, inductance, and capacitive elements and transmission lines to fit the four traces. Then, the matching circuits are mapped into the meta‐absorber structure by using three types of proposed layers. The full simulation method based on the finite element method is used to verify the proposed concept. Furthermore, an external dielectric loading strategy has been developed to achieve good angular stability up to 60° for the radar cross section reduction under transverse electric and transverse mangetic polarization incidence. The proposed method may provide a convenient way for various microwave devices, such as antennas.

A Multi-Band Circularly Polarized-Shared Aperture Antenna for Space Applications at S and X Bands

In this article, a compact multiband antenna design and analysis is presented with a view of ensuring efficient uplink/downlink communications at the same time from a single antenna for CubeSat applications. This design shares the aperture of an S-band slot antenna to accommodate a square patch antenna operating in the X-band. Shared aperture antennas, along with an air gap and dielectric loading, provided good gain in both frequency bands. The S-band patch had an S11 = −10 dB bandwidth of 30 MHz (2013–2043 MHz, 1.5%), and the X-band antenna demonstrated a bandwidth of 210 MHz (8320–8530 MHz, 2.5%). The Axial Ratio (<3 dB) bandwidth of the slot antenna in the S-band is 7 MHz (2013–2020 MHz, 0.35%), and it is 67 MHz (8433–8500 MHz, 0.8%) in the case of patch antenna in the X-band. While the maximum gain in the S-band reached 7.7 dBic, in the X-band, the peak gain was 12.8 dBic. This performance comparison study shows that the antenna is advantageous in terms of high gain, maintains circular polarization over a wideband, and can replace two antennas needed in CubeSats for uplink/downlink, which essentially saves space.

Partially dielectric loaded planar Vivaldi array antenna for forward‐looking GPR applications

AbstractThis paper presents a novel two‐element partially dielectric loaded planar Vivaldi antenna array for ultra‐wideband applications. This array is capable of operating between 380 MHz and 3 GHz and is designed on a 1.6‐mm thick low‐cost FR4 substrate with total size of 25 × 330 × 430 mm3. Innovative approaches to various gain enhancement techniques such as partial dielectric loading, corrugations, and U‐shaped back reflector used for planar Vivaldi antennas, are collectively employed in this design. Various elements of the array are interconnected. The two‐element Vivaldi array is fed by using a power divider. The array is designed by using a full‐wave three‐dimensional EM simulation tool. The designed antenna is manufactured and then measured. The simulation and measurement results are found to be consistent with each other.

The effects of catalyst conductivity and loading of dielectric surface structures on plasma dynamics in patterned dielectric barrier discharges

Dielectric barrier discharges (DBDs) are promising tools for air pollution removal and gas conversion based on excess renewable energy. Catalyst loading of dielectric pellets placed inside the plasma can improve such processes. The effects of such metallic and dielectric catalyst loading on the discharge are investigated experimentally. A patterned DBD is operated in different He/O2 mixtures and driven by a pulsed rectangular voltage waveform. Hemispherical dielectric pellets coated by different catalyst materials at different positions on their surface are embedded into the bottom grounded electrode. Based on phase resolved optical emission spectroscopy the effects of different catalyst materials and locations on the streamer dynamics are investigated. The propagation of cathode directed positive volume streamers towards the apex of the hemispheres followed by surface streamers, that move across the structured dielectric, is observed for positive applied voltage pulses. Coating the apex with a conducting catalyst results in attraction of such streamers towards the apex due to charging of this surface, while they avoid the apex in the presence of a dielectric catalyst. Surface streamers, that propagate across the hemispheres, are stalled by conducting catalysts placed on the embedded pellets as rings of different diameters, but propagate more easily across dielectric coatings due to the presence of tangential electric fields. Reversing the polarity of the driving voltage results in the propagation of negative streamers across the patterned dielectric and attenuated effects of catalytic coatings on the streamer dynamics.

A novel reconfigurable H-plane Horn leaky wave Substrate Integrated Waveguide MIMO antenna for K band

In this paper a novel reconfigurable H-plane horn Multiple Input Multiple Output (MIMO) leaky wave substrate integrated waveguide (SIW) antenna is proposed. The antenna is operating at two resonant frequencies, 22.8 GHz and 26.32 GHz. The transverse periodic leaky wave slots are radiating power in the broadside direction at 22.8 GHz and pattern diversity is achieved at 26.32 GHz. Dielectric loading and an array of meta-material structures are used, which further improve gain of the antenna. The antenna achieves better matching with a return loss of –33.5 dB at 22.8 GHz and maximum isolation of −38.7 dB at 26.32 GHz is achieved between antenna elements. A 2x2 and 4x4 MIMO SIW antenna is designed and analyzed in this paper. All the MIMO performance measurement parameters have values within limits. The antenna achieves a maximum gain of 7.3 dBi and 8.1 dBi. The proposed antenna operates in the K band (18 GHz–27 GHz) region, making it suitable for automotive radars and short-range applications.

Modeling and Operation of Series-Parallel Resonant Load in Industrial RF Dielectric Heating Application

Radio Frequency (RF) based heating application is used in multiple industries like drying cross-laminated woods, food and packaging, melting silicon etc. These industrial RF heating plants operate at frequencies of 6.78 MHz, 13.56 MHz, or 27.12 MHz (ISM band). Historically, the high frequency requirement has forced the industry to rely on vacuum tube based RF generator, which are only 60% efficient. Modern semiconductors like wide bandgap (WBG) devices have achieved the high frequency operation that is required to replace the inefficient vacuum tubes. However, a comprehensive study of load network for an industrial RF heating plant has not been undertaken such that an existing plant can be retrofitted with semiconductor based turn-key solution. In this paper the authors present design equations for an industrial RF dielectric heating load structure and suggest necessary modifications required to replace vacuum tube RF generator with voltage source converter (VSC). A new figure of merit (FOM) is defined that impacts the load structure efficiency. Finally, a small-scale prototype load is manufactured as a case study. The prototype demonstrated an output power of 750 W at 6.76 MHz with an overall efficiency of 90% from DC input to RF load which can not be achieved with a vacuum tube technology.

Metamaterial-based electromagnetically induced transparency-like sensor design with low-volume sliding dielectric loadings

Abstract In this study, tunability of the electromagnetically induced transparency (EIT)-like transmission window by low-volume dielectric loadings is presented both numerically and experimentally in S-band. The EIT-like transmission behavior is obtained by a metamaterial, composed of an electric resonator and a closed-ring resonator patterned on a dielectric substrate. The frequency tuning is obtained by two applications called horizontal sliding application (HSA) and vertical sliding application based on sliding of the low-volume loadings from the edges to geometric center (i.e., inward). For both applications, the frequency tuning has been investigated for dielectric loadings which have relative permittivity of 2.2, 3, 4.5, and 6.15. The results reveal that the proposed sliding applications are effective on tuning the transmission peak frequency. An achieved 1136 and 971 MHz absolute spectral shifts and corresponding 6.34% and 5.41% absolute sensitivities by simulations and measurements, respectively, are the best results which are obtained for HSA at 5 mm shift value. Moreover, 14.67% sensitivity is obtained in simulations for the complete dielectric loading on the resonator in response to the increase in refractive index from 1 to 1.5. It is believed that the proposed applications will contribute to the existent sensing studies.

A Frequency-Reconfigurable Dielectric Resonator Antenna With a Water Layer

This letter introduces a frequency-reconfigurable dielectric resonator antenna (DRA) with a water layer integration. The proposed method is based on the strategy-combination of mode reconfiguration and dielectric loading. Firstly, the frequency band of the DRA is reconfigured between the resonant frequencies of the fundamental <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE^\rm{y}_{111}$</tex-math></inline-formula> and quasi- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE^\rm{y}_{111}$</tex-math></inline-formula> modes by flowing liquid control of water pumping in and out of the microfluidic cavity. Then, the frequency response of quasi- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE^\rm{y}_{111}$</tex-math></inline-formula> mode is continuously swept by altering the thickness of water layer. For demonstration, the DRA is designed with a solid dielectric material of K9 glass with the permittivity of 6.25 and loaded with a layer of fresh water with the permittivity of 77. Finally, the proposed antenna is fabricated and measured, which performs with a wideband reconfigurability and stable far-field performance corresponding to the different frequency responses.

Innovative method of broad banding a helical-TWT

A new method of broad banding a helix TWT is suggested in which, instead of shaping the dispersion characteristics of helical structure by using tapered geometry dielectric helix-support rods, a two-stage dielectric loading is provided by severing the structure in two sections each with a conventional helix supports here typically of wedge cross section. One of the sections was heavily dielectric loaded compared to the other section so that two gain peaks on the frequency scale occur in the former section unlike in latter in which a single gain peak occurs. The structure parameters of the two sections and the beam parameters were so adjusted that the gain peak of lightly loaded section falls between the two gain peaks of the heavily loaded section resulting in ultra-wide bandwidths of the proposed two-stage device. In addition to the well-known Pierce’s gain formula, the basic sheath-helix model of the structure was used in the process of developing this method. Research has been done to investigate whether or not a positive stage speed tightening might help to enhance the display of a broadband helix voyaging wave tube.

Beyond-Decade Ultrawideband Quad-Ridge Flared Horn With Dielectric Load From 1 to 20 GHz

In this article, we present a novel dielectrically loaded quad-ridge flared horn (QRFH) as a reflector feed with beyond-decade ultrawideband performance. The dielectric is machined in a low-loss, space-grade polyimide specified with low outgassing for a vacuum environment. The feed covers 1–20 GHz bandwidth with a measured band-average input reflection of −13.6 and 41.5 dB isolation between two orthogonal polarized ports. Predicted performance in a paraboloidal reflector with a 60° half-subtended angle is 62% aperture efficiency average over the band. The ridges of the horn are designed with analytic-spline-hybrid 3-D profiles with thickness flaring outwards toward the feed aperture, improving low-frequency polarization properties. The QRFH was manufactured in four quarters for accurate ridge-to-ridge alignment and a reduced number of interfaces for good thermal properties in cryogenic applications. A prototype feed has been installed and tested with promising results in one of the 6 m offset Gregorian reflectors of the Allen Telescope Array (ATA) located at the Hat Creek Observatory, Hat Creek, CA, USA.

A high‐voltage solid‐state Marx generator with adjustable pulse edges

AbstractMost reactors for non‐thermal plasma excitation are capacitive to pulse generators. The density and temperature of electrons in plasma are dominated by the discharging currents which are proportional to the pulse edges. However, adjusting the pulse edges is quite challenging since the switching speed and the inductance and capacitance in the discharging loops dominate them. This study proposes a drive circuit for solid‐state Marx generators with adjustable edges. The drive circuit controls the Miller plateau by adjusting the gate voltage amplitude to adjust both the rise time and fall time of pulses continuously and independently. The influence of the gate voltage on the Miller plateau and the rise time is studied. The feasibility is verified by both simulating and experimental results. An 8‐stage solid‐state Marx generator prototype was built, and 4.8‐kV pulses with a rise time in the range of 79 ns‐22.21 μs were obtained over capacitive loads. Adjusting pulse edges can control the current amplitudes in dielectric barrier discharge loads.

Dual-Polarized 6–18-GHz Antenna Array With Low-Profile Inverted BoR Elements

This article investigates a dielectric-loaded Vivaldi-type antenna array that is formed inside a plastic block. It utilizes the inverted body-of-revolution (BoR) structure, where cone-shaped cavities are formed in a dielectric material and metalized from the inside. The metalized cavities form an array of inverted BoR elements that are fed by a single printed circuit board. In contrast to previous work, this paper uses a solid, shaped plastic block instead of foam as a dielectric material and exploits its considerably higher permittivity to reduce the height of the elements. The reduced profile provides an excellent polarization purity in the class of tapered slotline (TSL) antennas while a 3:1 bandwidth is maintained with an active reflection coefficient (ARC) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\leq -10$ </tex-math></inline-formula> dB. The shaping of the dielectric block decreases the scan loss of the array and prevents detrimental surface waves. The proposed array can steer the beam up to ± 50° in all planes without exceeding −10 dB ARC. The proposed dielectric loading may be applied also to other antenna types, such as conventional BoR antennas. The excellent electrical performance and manufacturability of the array are confirmed by fabricating and measuring a prototype.

Simulation and Measurement of an Interaction Structure With Distributed Radiation Coupling Circuit for a High-Power Ku-Band Gyro-TWT

Design and measurement of a distributed radiation coupling (DRC) circuit for the Ku -band TE11-mode gyrotron traveling wave tube (gyro-TWT) amplifier are presented. Different from the dielectric-loaded (DL) waveguide, the proposed DRC circuit can suppress the parasitic modes by achieving sufficient radiation coupling losses. It has the merit of lowering the microwave power loss density, which can improve the tube stability and average power-handling capability. Based on this proposed DRC circuit, a Ku -band TE11-mode gyro-TWT was designed and the particle-in-cell (PIC) simulation shows it can obtain a saturated output power of over 150 kW from 15.3 to 17.2 GHz for an electron beam with a velocity spread of 4.35%. As a comparison, the maximum average microwave power loss density is only 20% of the DL circuit under the same operating parameters. For verification, a DRC circuit was manufactured and cold tested. The maximum deviation between the measured results and our analysis is within 10%.

Gain and Bandwidth Improvement Studies of Millimeter Wave Periodically Dielectric Loaded Gyro-Twystron Amplifier

In this article, the spurious oscillations in the output section of gyro-twystron have been analyzed and the design and modeling of its various subassemblies also been presented. The periodic dielectric loading (PDL) technique has been adapted in the output waveguide section to improve the device gain by suppressing the backward wave oscillations (BWOs). Further, to improve the performance of the amplifier all the cavities were staggered tuned. The particle-in-cell (PIC) simulation of the present PDL gyro-twystron predicted an RF output power of ~120 kW in the fundamental TE01 mode at 94 GHz. The conversion efficiency, 3-dB bandwidth, and saturated gain were calculated as ~34%, ~2.2 GHz, and ~51 dB, respectively. A triode magnetron injection gun (MIG) was designed for 60 kV and 6 A gyrating electron beam and optimized for the velocity spread of ~2.2% with a velocity ratio of 1.6. A single-stage depressed (SSD) collector has also been designed to enhance the efficiency of the amplifier to ~57%. A double-disk window was designed and optimized for the broader bandwidth of ~8 GHz.

Theory and measurement of the single and hybrid-mode excitation and evolution in a lossy-dielectric-loaded waveguide

ABSTRACT This paper investigates the mode excited, evolved, and propagating properties of the lossy dielectric-loaded waveguide (DLW) used in a Ku-band TE11-mode gyrotron traveling wave tube (gyro-TWT). Theoretical calculation and numerical simulation show that different DLW eigenmodes can be excited by the hollow circular waveguide as a single or hybrid-mode. This study clearly reveals the transformation conditions of the single and hybrid-mode, and the mechanism of the resulting specific dispersion, loss, and electromagnetic field distribution. According to the mode excitation principle and its evolution laws, the propagating properties can be accurately controlled by adjusting the dielectric thickness, which can effectively suppress the potential oscillations and improve the electron bunching phase in the gyro-TWT. As a result, the dielectric loading scheme can be optimized by properly arranging the DLWs, thus enhancing the stability and gain of the gyro-TWT. The theory and simulation are verified by the vector network analyzer measurement at Ku-band, and the results show a good agreement.