Flexible Dielectric Waveguide Research Articles

A Multimodal Dielectric Waveguide-Based Monopulse Radar at 160 GHz

For highly integrated imaging systems above 100 GHz, the complexity and chip area increase significantly with an increasing number of channels. In addition, bulky dielectric lenses prevent applications in spatially restricted surroundings. The presented concept of an imaging monopulse radar with a mechanically flexible front end reduces the required chip area and allows the antenna to be placed in any desired position apart from the sensitive electronics. The radar system is based on a two-channel 160-GHz microwave monolithic integrated circuit (MMIC) feeding a flexible dielectric waveguide. Depending on the angle of the incidence signal, a sum mode (HE11 mode) and a difference mode (HE21 mode) are excited in the dielectric waveguide. MMIC and waveguide are connected by a self-aligning transition reducing the requirements for packaging accuracy. The required chip area of the transition is only $0.022\lambda ^{2}$ with a spacing between the on-chip antennas of $\lambda /4$ . The measured ambiguity-free region between −18° and 15° is defined by the modified elliptical lens antenna focusing in the $E$ -plane only. A mechanical bending of the flexible waveguide is possible down to a radius of at least 2 cm without affecting the angle estimation capability.

Self-Aligning and Flexible Dielectric Waveguide Plug for MMICs at G-Band

The packaging technology for transitions to dielectric waveguides in the frequency range above 100 GHz is complex and must be highly precise, and the waveguides are usually permanently connected. This letter presents a transition from a monolithic microwave integrated circuit (MMIC) to a flexible dielectric waveguide at $G$ -Band (140–220 GHz), which is self-aligning and, thus, reduces the requirements for packaging accuracy. Furthermore, the transition is mechanically decoupled to avoid mechanical stress to the MMIC and to reconnect it arbitrarily often. A patch radiator on a quartz-glass carrier is excited by a coupler on the MMIC. It feeds the $\mathrm {HE_{11}}$ mode into a rigid, high-permittivity dielectric dome, which increases the coupling efficiency. The flexible dielectric waveguide is placed above the dome and fixed with Rohacell half shells. The minimum insertion loss measured with a back-end-of-line (BEOL) MMIC is 3.0 dB at 168 GHz.

Low-Loss, Thermally Insulating, and Flexible Rectangular Dielectric Waveguide for Sub-THz—Signal Coupling in Superconducting Receivers

Dielectric waveguides have potential as transmission lines in subterahertz (sub-THz) applications due to their low-loss. A new application of a rectangular dielectric waveguide (RDW) for a THz superconducting receiver system for radio astronomy is investigated and demonstrated for the first time. The RDW can be used to transmit sub-THz local oscillator (LO) signals into the cryostat for driving the superconductor insulator superconductor mixer, with very low heat transfer. A series of RDWs with different lengths are fabricated. The measured average attenuation constants of the RDW are 0.034 and 0.069 dB/mm at 3.4 and 300 K measurement environments over 240–300 GHz, respectively. The double-sideband system noise temperature of the receiver system is also measured. With this LO signal feeding system, there is only 0.69 mW thermal transfer power from the 300 to the 3.4 K cold stage. Compared to traditional pumping signal feeding schemes, such as the horn-to-horn structure and beam splitter method, this approach outperforms the traditional schemes in terms of feeding flexibility, insertion loss, and thermal isolation for the cryostat. The proposed RDW can be widely applied to superconducting receivers for radio astronomy in the future.

160-GHz Radar Proximity Sensor With Distributed and Flexible Antennas for Collaborative Robots

There is a growing demand for collaborative robots in order to improve the efficiency of industrial processes and to push Industry 4.0 forward. The challenge for these robots is the compliance of the safety regulations to protect human workers from injuries. Therefore, a large number of sensors for the close range (several centimeters up to some meters) around the robot are needed. For a protective cover around the robotic arms all sensors must cooperate and process their information together. This paper presents a close range proximity sensor based on a 160-GHz radar MMIC with a transition to two flexible dielectric waveguides. On the low-loss waveguides, leaky-wave antennas with a large field of view are distributed. This reduces the number of sensors and achieves a coverage area for one sensor of more than 2200 cm 2 for a distance of 30 cm. For distances below 30 cm the sensor has blind areas. However, the expected extended targets like body parts can still be detected and the proximity sensor will stop the robot in the danger area. Additionally, the flexible waveguide offers the possibility to place the antennas almost arbitrarily around the robotic arm. For a single target scenario it is even possible to determine the target position by multilateration with only one receive channel.

Building Blocks for a Millimeter-Wave Multiport Multicast Chip-to-Chip Interconnect Based on Dielectric Waveguides

A multichip multiport communication network technology is proposed based on a network of dielectric waveguides. For optimum performance and best versatility, a combination of high-permittivity dielectric slab waveguide and low-permittivity flexible dielectric rod waveguide is proposed. Additional building blocks are a dielectric waveguide Y junction and transitions between waveguide types as well as between chip and waveguide. The resulting multichip multicast multiport interconnect network features low overall transmission loss and small chip-area consumption for the chip-to-waveguide transitions. Measurement results for all components are presented for frequency bands around 60 GHz and around 100 GHz. The insertion loss of the transition from on-chip microstrip line to dielectric slab waveguide, extracted from end-to-end measurements, is 3.3 dB around 60 GHz and 2.2 dB around 100 GHz. Experimental four-terminal networks, each comprising four chip-to-waveguide transitions and two dielectric waveguide Y junctions, show measured end-to-end insertion loss (including pass through two Y junctions and two chip-to-waveguide transitions) of 21 dB (around 60 GHz, covering 26-mm distance) and of 17 dB (around 100 GHz, covering 20-mm distance), respectively. These values outperform wireless interconnects by far and emphasize the performance and versatility of the proposed approach for chip-to-chip multicast multiport interconnects.

High permittivity ceramics loaded silicone elastomer composites for flexible electronics applications

The dielectric properties of silicone elastomer composites are important in designing flexible electronic devices. The recent explosive growth in wireless communication, automotive and biomedical applications increases the demand for flexible dielectric materials. However, it is very difficult to identify a homogeneous material which possesses these desired properties. Flexible silicone rubber- ceramic composites based BaTiO3 (BT), SrTiO3 (ST) and Ca(1−x)Nd(2x/3)TiO3 (CNT) ceramic fillers have been prepared. The relative permittivity, thermal conductivity and water absorption increase whereas the coefficient of linear thermal expansion decrease as the volume fraction of filler increases. In the case of dielectric loss; a decreasing trend is shown by SR-ST and SR-CNT composites with filler volume fraction whereas SR-BT composites show a reverse trend since BT is a lossy material. The composites have εr in the range 3–14 in the microwave frequency range. The composites with high filler loading are suitable candidates for core of flexible dielectric waveguide and embedded capacitor applications and the composites with ST and CNT are suitable for cladding of flexible dielectric waveguide and also for microwave substrate applications

Low loss flexible SrTiO3/POE dielectric composites for microwave application

Flexible, high dielectric constant and low dielectric loss composites for microwave application fabricated with SrTiO3 (STO) ceramic filler dispersed inside a thermoplastic polyolefin elastomer (POE) polymer matrix have been studied in this paper. The dielectric property and the mechanical property of STO/POE composites filled with different volume fraction of ceramic filler were investigated. The results indicated that with the increase volume fraction of ceramic filler, both the permittivity and the dielectric loss of composites increased. Good frequency stability within a wide range was observed in all the samples. For the composites containing 40 vol% STO, the composites has a tensile strength of 2.75 MPa with an elongation of about 90% at break value. The permittivity and the dielectric loss of the composites were 11.0 and 0.01 in microwave frequency, respectively. A microstrip transmission line on the composites containing 40 vol% STO as a microwave substrate is designed and measured after bending at different angles, meanwhile the transmission coefficients of the microstrip transmission line were unchanged when bending angle is less than 60°. This indicates that the STO/POE composites have the promising characteristics for potential applications in microwave substrate, flexible dielectric waveguide and related flexible microwave devices.

Dielectric properties of SrTiO 3/POE flexible composites for microwave applications

Composites fabricated with SrTiO 3 ceramic filler dispersed inside a thermoplastic polyolefin elastomer (POE) polymer matrix, with excellent dielectric properties and good flexibility, have been studied in this paper. The relative permittivity of SrTiO 3/POE composites blended with different volume fraction of ceramic filler was investigated as a function of temperature and frequency. The results indicated that with the increase of ceramic filler, both the relative permittivity and the dissipation factor of composites increased. Good frequency stability within a wide range was observed in all the samples. The theoretical dielectric constant obtained from the effective medium theory of Bruggeman's model is in good agreement with the experimental data. For the composites containing 40 vol.% SrTiO 3, the dielectric constant and the loss tangent were 11.0 and 0.01 at 900 MHz, respectively, while the mechanical test results showed good flexibility on the final quality of the composites with the elongation of 90%. This indicates that the ST/POE composites have the promising characteristics for potential applications in the flexible dielectric waveguide and related flexible microwave devices.

Measurement of dielectric and radiation losses for flexible circular dielectric waveguides in Q‐band

AbstractExperimental results are presented for the dielectric and radiation losses from flexible circular PTFE waveguides in the Q‐band. The dielectric and radiation losses from rod and tube waveguides were found to depend strongly on the design parameters, such as the operating frequency, area of the dielectric region in the guiding cross sections, and curvature radii of the bending. The dielectric losses from the straight guides showed a relatively good agreement with the theoretical results. The radiation losses with a small curvature radius, which cannot be predicted using current theories, were determined based on the differences between the measured insertion losses and the dielectric losses. The validity of the current results was confirmed based on the fractional power flow ratios in each region of the waveguides. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 000–000, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10529

Flexible dielectric waveguides with powder cores

Flexible dielectric waveguides have been demonstrated at 10 GHz and 94 GHz using thin-wall polymer tubing filled with low-loss, high-dielectric-constant powders. Absorptive losses of the order of 10 dB/m were measured at 94 GHz. with nickel-aluminium titanate and barium tetratitanate powder in polytetrafluoroethylene (PTFE) lightweight electrical tubing. Bending losses at 94 GHz were negligible for curvature radii greater than 4 cm. M.H. Kuhn's (1974) theory of three-region cylindrical dielectric waveguide was used to calculate dispersion curves for the lower-order modes for several combinations of dimensions and dielectric constants. Good agreement was obtained between experimental and theoretical values of guide wavelength. A scheme is proposed for classifying hybrid modes of three-region guides based on the ratio mod E/sub z//H/sub z/ mod . For two-region guides, this reduces to E. Snitzer's (1961) familiar scheme.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Tube‐contacted slab dielectric waveguide for millimeter waves

AbstractIn this paper, a tube‐contacted slab dielectric waveguide for millimeter waves is proposed, and a theoretical analysis and experiments are performed to determine the propagation characteristics. This waveguide consists of a dielectric tube with its radius larger than the wavelength, placed on a guiding film. The guided wave energy is concentrated near the contact point between the tube and the film. Since the tube is easily bent due to its structure and the field distribution is similar to Gaussian, the structure can be used as a low‐dispersion flexible dielectric waveguide. Also, since the tube radius is larger than the wavelength, the waveguide can be used for high power transmission. The effective dielectric constant method has been used for analysis, and the field distribution and the phase constant have been computed. A waveguide has been fabricated for 35 GHz and the field distribution, propagation loss, guide wavelength, the field distribution at a bend and the bending loss have been measured. Measured results of the field distribution, guide wavelength and bending loss have agreed well with theoretical predictions. The propagation loss is 1.52 dB/m. In addition to the bending loss, variations of the field distribution at the transition from the straight guide to the bend have been measured. Based on these measured results, it is shown that the waveguide can be used for low‐dispersion flexible transmission line or for high power transmission.