Dielectric Line Research Articles

Radiation of a TM mode from an open end of a three-layer dielectric capillary

Abstract Modern trends in beam-driven radiation sources include the interaction of Cherenkov wakefields in open-ended circular waveguides with complicated dielectric linings, with a three-layer dielectric capillary recently proposed to reduce radiation divergence being a representative example [Opt. Lett. 45 5416 (2020)]. We present a rigorous approach that allows for an analytical description of the electromagnetic processes that occur when the structure is excited by a single waveguide TM mode. In other words, the corresponding canonical waveguide diffraction problem is solved in a rigorous formulation. This is a continuation of our previous papers which considered simpler cases with a homogeneous or two-layer dielectric filling. Here we use the same analytical approach based on the Wiener–Hopf–Fock technique and deal with the more complicated case of a three-layer dielectric lining. Using the obtained rigorous solution, we discuss the possibility of manipulating the far-field radiation pattern using a third layer made of a low permittivity material.

Terahertz-driven acceleration of subrelativistic electron beams using tapered rectangular dielectric-lined waveguides

We investigate the use of tapered rectangular dielectric-lined waveguides (DLWs) for the acceleration of low-energy, subrelativistic, electron bunches by the interaction with multicycle narrowband terahertz (THz) pulses. A key challenge exists in this subrelativistic regime; the electron velocity changes significantly as energy is gained. To keep electrons in the accelerating phase, the phase velocity must also be increased to match. We present simulations which demonstrate that the dielectric thickness can be kept constant and the width of the dielectric lining can be tapered along the direction of travel to vary the phase velocity, an approach only possible by the use of a rectangular waveguide geometry. The properties of tapered DLWs are discussed and following this, a design process is presented to demonstrate that the way this tapering can be optimized for different pulse and beam parameters. The minimum accelerating gradient for electron bunch capture is derived and compared to simulations. As examples of this design process, designs are considered based on considerations of the THz source, incoming electron beam, and manufacturing tolerances. A maximum THz pulse energy of 22.5 μJ in the DLW was considered, which represents what is readily achievable using mJ-level regenerative amplifier laser systems together with optical-to-terahertz conversion in lithium niobate crystals. This will be more than double the energy of a 100 keV electron beam, increasing it to 205 keV. We describe the optimization process and present a detailed exploration of the beam dynamics, discussing how the performance will further improve with compressed bunches. Published by the American Physical Society 2024

Thermal Properties of Backfill Material for Underground Heat Exchange Applications

We are investigating the effect of the thermal properties of backfill material on the efficiency of underground thermal energy systems. We have used aluminum to increase the thermal properties of clay-bentonite and to investigate its potential as a backfill material in underground heat exchange applications. The measurements of thermal properties were made at room temperature using the Transient Plane Source (TPS) technique. The measurements were based on an infinite homogeneous medium using different composites of aluminum and clays in amounts of aluminum concentration ranging from 6 to 25 percent of the sample’s weight. The results confirmed an overall relative increase of 170% and 135% in the thermal conductivity and diffusivity, respectively as the Al content increased by 25%. The estimated average of the thermal transmittance (U-value ) of these samples was in the range from 0.40 to 1.1 W/m2K, which was directly proportional to the relative increase in the measured properties. Our findings can be applied to underground thermal energy systems, ground source heat pumps, and solid dielectric underground transmission lines.

Design and analysis of high-resolution CMOS digitally controlled oscillator with tunable transformer

A tunable transformer based millimeter-wave digitally controlled oscillator (DCO) is proposed to achieve high frequency resolution with compact area in this paper. An 8-shaped inductor is employed as primary coil of the transformer to generate the opposite magnetic field and achieve a weak coupling to the secondary coil, which is beneficial to enhance the scaling effect of the capacitor to achieve a smaller equivalent capacitance. The equivalent model of the transformer structure is analyzed theoretically. Distributed capacitors are placed under the secondary coil, which can be flexibly adjusted to achieve high frequency resolution. A digitally controlled artificial dielectric (DiCAD) differential transmission line is implemented to achieve coarse and medium frequency tuning. The DCO is implemented in 40-nm CMOS process with a core area of 0.026 mm2. Simulated results demonstrate a minimum frequency tuning step of 381 KHz with a frequency tuning range of 12.3% from 58.60 to 66.28 GHz, and the phase noise at 1-MHz offset is from −91.3 to −94.0 dBc/Hz, corresponding to an FoM range of −179.5 to −182.2 dB, while the power consumption is 8.8 mW.

A K-Band CMOS Standing Wave Oscillator Using Digital-Controlled Artificial Dielectric Differential Transmission Lines

This letter presents a K-band standing wave oscillator (SWO) based on digital-controlled artificial dielectric differential transmission lines (DiCAD-DTLs). By combining the unique property of constant phase and digitally controlled wide tuning range, the proposed design achieves a better balance between phase noise and tuning range. A compact layout and high operating frequency are, hence, possible, since DiCAD-DTLs in this design behave like a resonator instead of a capacitor bank. This chip was fabricated in a standard 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process with an area of 0.035 mm2. It achieves a tuning range from 19.2 to 21.6 GHz. The measured phase noise is around −104.7 dBc/Hz at a 1-MHz offset. This oscillator including buffer consumes 5 mA from a 1.5-V supply, demonstrating a figure of merit (FOM) and FOM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {_{T}}$ </tex-math></inline-formula> of −181.8 and −183.3 dBc/Hz, respectively.

An Integrated Low-Power and Small-Area Time-Domain Dielectric Chip Sensor

We presented a novel integrated dielectric chip sensor based on time-domain sensing technique. The sensor is based on a dielectric constant-dependent delay line with a load capacitor realized by an interdigitated capacitor (IDC). The IDC exposed to the material under test (MUT) is used to sense the change of MUT’s dielectric constant. The delay line is utilized to generate a delay proportional to the measured dielectric constant. To improve the sensitivity with a smaller area, a time-amplifier (TA) is employed to amplify the delay change. As a proof of concept, the sensor has been calibrated with Ethyl-acetate, Butyraldehyde, Isopropanol and Ethanol. Ethanol and Ethyl-acetate mixture solutions, in steps of 20% of concentration change, have been used to demonstrate the performance of the sensor. The chip is fabricated in a 55 nm CMOS technology with a core area of 0.105 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> mm. It only consumes 0.13 mA from a single 1.2 V. Compared with other methods, this method has more advantages in sensor array applications.

Evaluation Means of Oil-paper Insulation’s Water Based on DC Conductivity

.The measured spectral line based on frequency domain dielectric spectrum contains multiple superpositions of conductance and polarization processes. In view of the lack of methods to separate the polarization and the conductance processes and the lack of unique methods to characterize the model conductance parameters, the micro conductance processes are studied in depth according to the real and imaginary Kramers-Kronig relation. Firstly, different water content insulation samples were prepared during the laboratory conditions, and dielectric lines in frequency domain were obtained by measurement. Secondly, according to the k-K relation, the relaxation loss spectrum line is obtained by numerical integration of the measured real part of the complex polarization spectrum line, and then the conductivity loss spectrum line is obtained. Finally, the least square method is used to fit the conductivity spectrum line and calculate the conductivity value. The experimental results show that the conductance of the virtual part of the repolarization measurement can be separated from the relaxation loss line by k-K transformation, and the dc conductance can be calculated. At the same time,with the oil-paper insulating sample’s water content increasing, its electrical conductivity is gradually enhanced.

Design Plasmonic Optical 4 × 2 Encoder Based on 2D Photonic Crystal Ring Resonator

Digital encoders are one of the key devices required in optical communication and digital signal processing systems. In this paper, a new photonic crystal structure is used to design all-optical 4 × 2 encoder constructed from GaAs rods with square lattice in the pentane background based on plasmonic effect. Gold rods have also been used at the interface of dielectric rods and lines defect, which create plasmonic properties into the photonic crystal structure. The designed optical device is composed of four input waveguides and two output waveguides with two ring resonators at the resonant wavelength of 1.14 μm with TM polarization. The presented encoder platform has the small size of 19 μm × 33 μm that makes it to integration into compact all-optical processing systems. The encoder operation is simulated and analyzed with numerical finite-difference time-domain (FDTD) method and plane wave expansion (PWE) method. In the proposed structure, we have shown that by selecting the appropriate radius size for the resonant cavities, the desirable wavelength can be obtained. The maximum values of transmission efficiency for the first and second outputs are 82% and 96%, respectively. Resonant cavities are also located in the crystal lattice in such a way that by activating third input, 50% and 48% of the input signal will be obtained in each output ports indicating (1,1) logic state. So the new plasmonic photonic crystal encoder could be future applicable in the field of optical computing.

Narrowband and Wideband Bandpass Filters Based on Empty Substrate Integrated Waveguide Loaded With Dielectric Elements

Although several bandpass filters have been designed in the recently proposed empty substrate integrated waveguide (ESIW) technology to improve the quality factor and reduce losses with respect to those in SIW and planar technologies, all structures exhibit narrowband properties and none uses the design concept applied in this paper. The idea has been to insert a dielectric element in an ESIW section (DE-ESIW), which can work as a dielectric resonator or impedance inverter depending on the propagation nature of the fundamental mode. Thus, two novel Chebyshev bandpass filters for narrow and wide bandwidths based on this design concept have been designed in this paper in ESIW technology. The narrow bandpass filter has been realized by inserting four dielectric resonators in an evanescent ESIW section and using a coupling matrix synthesis method, whereas the wideband bandpass filter has been implemented by including six dielectric line sections in an ESIW line propagating the fundamental mode and applying a stepped impedance synthesis approach. A novel wideband microstrip to ESIW transition using cubic Bezier curves has also been designed for the successful integration of both narrow and wideband filters with other microstrip components. EM simulation and measurement frequency responses on manufactured prototypes have shown the versatility of the dielectric elements to efficiently implement narrowband and wideband ESIW bandpass filters, using the proposed design techniques based on coupling matrix and stepped impedances, respectively.

Silicon Probe Measurement and Characterization in Sub-THz Range

We propose, investigate, and demonstrate a pure and simple dielectric probe operating in the sub-terahertz range with an example band of interest 190-220 GHz. High-resistivity silicon technology is deployed for this non-TEM mode probe development as it presents a viable low-loss material. A T-shape alignment dowel was used to integrate the silicon probe with the waveguide block. The probe can be used to measure and characterize the low permittivity-based dielectric waveguide transmission line and its building components free from the use of any transition structures and TEM-mode probes. For demonstration, the silicon probe was used to measure a substrate integrated image guide and its components in the range of 190-220 GHz. A substrate integrated image guide (SIIG)-based thru, reflect, and line (TRL) calibration kit was developed, and a two-tier TRL calibration was used to characterize the SIIG.

A compact filtering antenna using dielectric strip resonator and parallel microstrip feed line

A filtering antenna using dielectric strip resonator and parallel microstrip feed line is proposed to achieve compact dielectric size and filtering response without gain reduction. The compact dielectric size is contributed by the dielectric strip resonator with high permittivity operated in the TMδ1 cavity mode, whose electric field distribution along the short side is far less than half-wavelength distribution. Therefore, the size of the proposed dielectric strip resonator is smaller than the traditional dielectric patch resonator operated in the TM11 cavity mode. Additionally, the parallel placed microstrip line not only can excite the dielectric strip resonator for filtering response without gain reduction, but also can provide one upper-edge radiation null for frequency selectivity enhancement. Compared with the reported filtering dielectric antennas, the proposed design exhibits the features of compact dielectric size, simple structure and wide stopband. For demonstration, one prototype operating at 4.9 GHz is fabricated, achieves the dielectric size of 0.00078 λ3 0 (λ0 is the wavelength in the free space at the center frequency), the measured peak gain of 7.1 dBi, the 10-dB impedance matching bandwidth of 4%, the stopband (> 16 dB) up to 1.84 f0, and the cross-polarization level of 20 dB within 3-dB beam range.

Response Improvement of Liquid Crystal-Loaded NRD Waveguide Type Terahertz Variable Phase Shifter

Liquid crystals, which have high dielectric anisotropy even in the terahertz region and are easily controllable for dielectric permittivity by applying an electric field, have become increasingly attractive in recent years. The non-radiative dielectric (NRD) waveguide has a structure in which a dielectric line is sandwiched between two metal plates and by replacing the dielectric part with liquid crystal, a low loss liquid crystal-loaded NRD waveguide type terahertz phase shifter can be obtained. However, since the thickness of the liquid crystal layer is several hundred micrometers, it has a response time of as long as several hundred seconds when the driving voltage is removed. It is necessary to devise improvements for practical application. By inserting two polyethylene terephthalate (PET) films and reducing the thickness of the liquid crystal layer, the decay time was improved well, but the phase change was significantly reduced. In this study, we report improving both decay time and phase change with aligned nanofiber/liquid crystal complex. In addition, we demonstrate liquid crystal-load phase shifter, which has 360° phase change and the response time below one second.

Cointegration of Single-Mode Waveguides and Embedded Electrical Interconnects for High-Bandwidth Communications

This article presents the modeling, development, and demonstration of glass interposer technology with single-mode waveguides (SMWGs) for high-bandwidth communications and embedded trenches for ultrafine copper traces for high-speed electronics. Glass as the substrate for the integration of photonics and electronics exhibits a unique combination of superior properties over silicon, laminates, and polymers. In conjunction with the advantages of glass, shape control of photoimageable dielectric lines during development and cure was developed and optimized. Single-mode polymer waveguides on glass were fabricated and characterized. Sample preparation methods and their impact on the sample edge quality and coupling loss will also be discussed in this article. Overall, this article presents the successful process development and demonstration of 3- $\mu \text{m}$ embedded trenches in the dielectric film for ultrafine copper traces and 2- $\mu \text{m}$ microvias for interlayer interconnects.

A 280-GHz Digitally Controlled Four Port Chip-Scale Dielectric Resonator Antenna Transmitter With DiCAD True Time Delay

A 280-GHz, fully integrated and digitally controlled multiport coherent radiator is presented. The silicon die acts as a chip-scale dielectric resonator antenna (CSDRA) and is excited by four differential loop inductors. The chip incorporates a balun for an X-band input signal, a 1–4 ultracompact differential Wilkinson splitter, and four $\times$ 27 active multipliers chain (AMC), which drive the four exciting elements. High-resolution, digitally controlled true time delay (TTD) elements, based on digitally controlled artificial dielectric transmission lines (DiCAD), are used to calibrate the variations between channels to optimize overall broadside radiated power and enable beam steering of ±15°. High-resolution DACs are used to accurately set the bias through a 3-wire SPI module. Fabricated in 65-nm CMOS, the $1.4\times 2$ -mm2 chip achieves a record EIRP of +21 dBm, a TRP of +8.5 dBm, and a power density of 2.25 mW/mm2 with 0.72% total efficiency, without using any external lens, superstrate, or postprocessing.

Development of inductance reference standard using coaxial transmission lines

The National Metrology Institute of Japan is developing a reference inductance standard using air dielectric coaxial transmission lines that can be used up to the gigahertz range. In this paper, inductance determination steps for a lossy air line were presented. In addition, a verification procedure by comparing electrically determined length le and measurement‐determined length lm was considered. In practice, the inductances of a 60‐mm‐long air line are determined and verified at the measurement frequency from 0.05 to 10 GHz. No significant difference was observed between le and lm. Therefore, the determined inductances from 0.05 to 10 GHz were considered verified. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Conductivity Induced by High-Field Terahertz Waves in Dielectric Material

An intense, subpicosecond, relativistic electron beam traversing a dielectric-lined waveguide generates very large amplitude electric fields at terahertz (THz) frequencies through the wakefield mechanism. In recent work employing this technique to accelerate charged particles, the generation of high-power, narrow-band THz radiation was demonstrated. The radiated waves contain fields with measured amplitude exceeding 2 GV/m, orders of magnitude greater than those available by other THz generation techniques at a narrow bandwidth. For fields approaching the GV/m level, a strong damping has been observed in SiO_{2}. This wave attenuation with an onset near 850 MV/m is consistent with changes to the conductivity of the dielectric lining and is characterized by a distinctive latching mechanism that is reversible on longer timescales. We describe the detailed measurements that serve to clarify the underlying physical mechanisms leading to strong field-induced damping of THz radiation (hω=1.59 meV, f=0.38 THz) in SiO_{2}, a bulk, wide band-gap (8.9eV) dielectric.

A Polarization Conversion Radome for High-Power Microwave Applications

A polarization conversion radome with embedded meander line with high-power microwave applications potential is presented. This radome is sandwiched by three-layer dielectric and two-layer metal meander line. The metal meander line is used to achieve polarization conversion, and the sandwich structure is used to avoid the contact between air and metal and then increase power handling capacity. After optimizing unit cell parameters, a polarization conversion radome with embedded meander line is constructed and loaded on the radial-line helical array antenna. The simulated and measured results show that the incident circular polarization wave is converted to a transmitted linear polarization wave well, and the antenna system is matched well in different radiation directions. The simulated results show that the polarization conversion radome with embedded meander line has great applications potential for high-power microwave field.

Controlled Out-of-Band Rejection of Filters Based on SIW With Alternating Dielectric Line Sections

A study for managing the out-of-band rejection in a new topology of filters based on substrate integrated waveguide with alternating dielectric line sections (ADLSs) is presented in this letter. ADLS is a filtering structure consisting on line sections of the same width but with alternating air and dielectric filling. The design of the lengths of each section provides the central frequency and the bandwidth of bandpass filter response. The proper selection of the structure substrate dielectric permittivity can increase the rejection band up to $2f_{o}$ . Moreover, the selection of the filter order (i.e., the number of sections with and without dielectric) can affect the depth of the rejection band. A study of the width and the depth of the rejection band is performed with different permittivities and orders for two different filters. Then, for validation purposes, the prototypes of both filters have been manufactured and measured.

Recent advances in compact repetitive high-power Marx generators

AbstractThis paper introduces recent activities on Marx-based compact repetitive pulsed power generators at the Institute of Applied Electronics (IAE), China Academy of Engineering Physics (CAEP), over the period 2010–2018. A characteristic feature of the generators described is the use of a simplified bipolar charged Marx circuit, in which the normal isolation resistors or inductors to ground are removed to make the circuit simpler. Several pulse-forming modules developed to generate a 100 ns square wave output are introduced, including thin-film dielectric lines of different structures, a pulse-forming line based on a Printed Circuit Board, and non-uniform pulse-forming networks. A compact repetitive three-electrode spark gap switch with low-jitter, high-voltage, and high-current was developed and is used in the generators. A positive and negative series resonant constant current power supply with high precision and high power is introduced. As an important part of the repetitive pulse power generator, a lower jitter pulse trigger source is introduced. Several typical high-power repetitive pulsed power generators developed at IAE are introduced including a 30 GW low-impedance Marx generator, a compact square-wave pulse generator based on Kapton-film dielectric Blumlein line, a 20 GW high pulse-energy repetitive PFN-Marx generator, and a coaxial Marx generator based on ceramic capacitors. The research of key technologies and their development status are discussed, which can provide a reference for the future development and application of miniaturization of compact and repetitive Marx generators.

Microwave Filter Based on Substrate Integrated Waveguide With Alternating Dielectric Line Sections

A new topology of microwave filter based on substrate integrated waveguide (SIW) with alternating dielectric line sections is presented in this letter. The two alternating sections are waveguides without and with a dielectric material acting, respectively, as the inverters and the resonant sections of the proposed filter. This topology allows to easily design and manufacture compact filters with lower losses and higher rejection band than other available SIW realizations. For validation purposes, a prototype of a four-pole bandpass filter, based on alternating dielectric line sections, has been designed and manufactured, including successful experimental results.