quasi-TEM Wave Research Articles

A Dual-Polarized CTS Array Antenna with Four Reconfigurable Beams for mm-Wave Wind Profile Radar

The wind profiler radar (WPR) system requires a dual-polarized antenna with multiple low-sidelobe and high-gain beams to facilitate the detection of weak signals reflected by atmospheric turbulence. This paper proposes a dual-polarized continuous transverse stub (CTS) K-band antenna with four reconfigurable beams, which comprises a series-fed CTS array and four 1-to-14 power dividers as line source generators (LSGs) to generate a high-quality quasi-TEM wave. The CTS element incorporates a stepped transition radiation stub design and employs a short cutoff stub on the upper surface of the series-fed parallel plate waveguide (PPW) to achieve optimal impedance matching. The entire antenna is an all-metal structure with remarkably low loss, and low-cost standard fabrication processes are employed for the prototype, which achieves fast reconfigurable four-beam scanning to 15°, with a gain of 31.09 dBi and sidelobe levels below −17.6 dB. Measurement results in an anechoic chamber agree well with simulations, demonstrating the antenna’s ease of manufacture, stability, and suitability for wind profile radar applications.

Numerical Analysis of the New Wireless Relay Transmission Model Based on FEM

In this article, a wireless relay transmission system in long-distance wells with new close winding helical coils is proposed. This system can realize more efficient bottom-up superposition transmission of signals in long transmission wells. At the same time, by redesigning the structure of the transmitting and relay antennas, a close winding helical coil structure with metal ring protection is proposed to excite quasi-TEM waves, which improves the efficiency of signal transmission in each channel and the compressive strength of the antenna. The simulation and experimental results demonstrate that under long distance and harsh stratum conditions, the wireless transmission system in long-distance wells has excellent signal transmission performance at extremely low frequencies. Compared with previous antenna structures, the new helical coil has better performance in transmission efficiency. This new wireless relay transmission system can greatly meet the long-distance transmission and conditions of oil and gas wells in the future.

Dynamic terahertz transmission based on coupling reconfiguration of spoof surface plasmon polaritons.

In this paper, we propose a dynamic transmission structure based on the coupling reconfiguration of spoof surface plasmon polaritons (SSPPs) in a 2D coplanar grating. By embedding a VO2 film into the signal line, the dynamic transmission is realized by reconfiguring the coupling of terahertz waves from quasi-TEM waves to SSPPs. The analysis shows that the transmission can be modulated in almost the entire band of the SSPPs, which further benefits a promising group delay due to the weak dispersion characteristic in the frequency region much lower than the cut-off frequency of SSPPs. In addition, for the dynamic modulation caused by the coupling reconfiguration, only rather a small area of VO2 film is needed to break the robustness of the 2D coplanar grating. Therefore, the coupling reconfiguration mechanism proposed in this paper facilitates the realization of an easily on-chip integrated dynamic SSPPs transmission structure with ultra-large bandwidth, and low group delay time difference. Accordingly, the presented mechanism will play a positive role in promoting the development of terahertz dynamic devices.

Low-Profile Dual-Polarized Multi-Beam Antenna Based on Pillbox Reflector and 3D-Printed Ridged Waveguide

In this article, a dual-polarized multibeam antenna is proposed. Two orthogonally polarized slotted waveguide antennas (SWAs) are cross-placed as the main radiator, which is designed based on ridged waveguides (RGWs) to reduce the width of the waveguides and obtain a wider steering range. The two SWAs are fed by two pillbox reflector beamforming networks (BFNs), and a special impedance transition is designed to reduce the reflection between the quasi-TEM wave in the parallel-plate waveguide (PPW) to the TE10 wave. By exciting different feeding patches in the focal planes of the pillbox reflectors, the SWA achieves different beams. In order to further increase the crossover level, the single-port excitation (SPE) and the dual-port excitation (DPE) method are used together to increase the equivalent source number in the compact area of the focal plane. Besides, the DPE method can also reduce the sidelobe level (SLL) of the beams excited by the side ports. A prototype is designed at the operating frequency of 10 GHz and fabricated by the 3-D-printed technology and computer numerical control (CNC) technology. The measured results show that the proposed antenna achieves ± 36° beam scanning in the multibeam plane with the minimum crossover level of −2.1 dB. The cross polarizations are below −20.0 and −15.9 dB for the horizontal polarization (H-P) and the vertical polarization (V-P), respectively. The advantages of dual polarization, high aperture efficiency, low cross polarization, wide beam scanning range, and low crossover level make this antenna a very appropriate choice in multibeam radars and communication systems.

A Low-Profile SIW-Based CTS Array with Reconfigurable Four Beams and Dual Polarizations for K-Band Sensing.

A dual-polarized continuous transverse stub (CTS) K-band antenna with reconfigurable four beams and low profile is proposed based on substrate-integrated-waveguide (SIW) design. It consists of a line source generator (LSG) on the bottom surface, a spherical-wave to plane-wave transforming part on the middle layer, and CTS radiators on the top surface. Particularly, the LSG has four SIW-based H-plane horns, and a chip is integrated to switch among the two pairs of horns, so as to transfer the quasi-TEM waves on the bottom surface by a ±10° deflection angle to the middle layer for the CTS radiators on the top surface, resulting in four reconfigurable scanning beams with 10° for two polarizations. The measurements show that it realizes four reconfigurable beams with a 25.8 dBi gain at 24 GHz, verifying the design. The proposed antenna takes into account the advantages of reconfigurable multi-beam, dual polarization, low side lobes, low profile, and high gain, which can be applied to K-band sensing, especially for wind profile radars.

Wideband and High-Gain Substrate Integrated Folded Horn Fed Open Slot Antenna

This article presents a novel substrate-integrated folded horn-fed open slot antenna with wide bandwidth and high gain for millimeter-wave (mmW) applications. The antenna has a three-layer planar structure, including a pair of open slot radiators and two substrate-integrated H-plane horns (SIHs) that are incorporated as the feed to generate quasi-TEM wave excitations. A folded SIH structure is introduced, which reduces the antenna size by 37%. To improve the gain and radiation patterns, the proposed antenna is designed with differentially fed excitations. The measured results validate that the antenna achieves a wide impedance bandwidth of 54.4% from 52.3 to 91.4 GHz and a peak gain of 16.3 dBi. Meanwhile, the radiation patterns are stable throughout the operating bandwidth with low cross-polarization, sidelobe, and back lobe levels. The proposed wideband, high-gain, planar, and low-cost antenna is an attractive candidate for mmW applications.

Enhanced Pencil-Beam Scanning CTS Leaky-Wave Antenna Based on Meander Delay Line

This letter presents a millimeter-wave (mmW) continuous transverse stub (CTS) leaky-wave antenna (LWA) with pencil-beam broadside radiation, high scanning-rate, and low sidelobe levels (SLLs) characteristics. A parallel-plate waveguide (PPW) meander delay line is employed to control the phase constant of the proposed LWA. By adjusting the length of the transverse electromagnetic TEM-mode PPW delay line, the phase difference between adjacent radiating elements can be altered, achieving flexible control of scanning-rate. Match stubs close to the radiation slots are utilized to suppress the open stopband, which help enlarge the beam scanning range. A linear source generator excited by multiple ports with amplitude tapering is employed to generate the quasi-TEM wave. Combined with additional amplitude tapering among the CTS radiation slots, low SLLs at both principal planes are realized. Experimental results show that the LWA with 12 radiation elements has a scanning range of -68° to 42° over the frequency range of 26-34 GHz (a scanning-rate of 13.75°/GHz) with SLLs lower than 13.5 dB/16.6 dB and a peak gain of over 22.5 dBi.

Generalized Design Technique of Ultra-Wideband Transitions for Quasi-TEM Planar Transmission Lines Based on Analytical Models

A generalized design technique of ultra-wideband planar transitions using EM-based analytical models is presented in this paper. Among various planar transmission lines, each transmission line has unique advantages over other line types, and a microwave component in a system can be designed to perform much better if it is implemented on a certain type of transmission line. Therefore, low-loss and high-performance transitions between transmission lines, with easy integrability with the main circuit board, are needed. The proposed transition design technique uses the Schwarz-Christoffel transformation, which is one of conformal mapping methods, and can be applied to design any planar transition between a pair combination of planar transmission lines based on TEM or quasi-TEM waves. To optimally match the characteristic line impedance and smoothly transform the electromagnetic field distribution between the planar transmission lines, entire cross-sections through the planar transition should be analyzed with proper models. In this paper, the cross-sections of planar transitions are categorized into 4 cross-sectional models, where each cross-section is divided into multiple regions for the analysis to obtain line capacitance. Therefore, for the 4 cross-sectional models, 7 types of basis structures are identified to obtain their capacitances by applying conformal mapping. By adding capacitances of a combination of the 7 analysis types, the total line capacitance, thus the characteristic line impedance, of any cross-sectional model of the planar transition can be obtained. The characteristic line impedance of each cross-sectional model calculated with the proposed analytical formulas is compared with the 3D EM calculations, and it is found that the deviated values are mostly well under 6%. This proposed technique enables to design various planar transitions efficiently and quickly for the maximum performance without parameter tuning trials, by providing optimal impedance matching and smooth field transformation up to mm-wave frequencies.

High Gain Periodic 2-D Leaky-Wave Antenna With Backward Radiation for Millimeter-Wave Band

A two-dimensional (2D) periodic leaky-wave antenna (LWA) is proposed in this article. Using dielectric-filled wedge-like waveguide as medium for wave propagation, the quasi-TEM wave inside the guide is leaked through periodic rings of narrow slots, resulting in high gain frequency-dependent beam. Due to the two-dimensional nature of the antenna, along with the slots distribution, the radiation has low side lobe level (SLL) without the need to extend the length of the antenna as in the case of periodic one-dimensional (1D) LWA. The measured gain of the antenna is 20.34 dBi with SLL less than −13 dB and cross-polarization less the −28 dB. The antenna is proposed for millimeter-wave (mm-Wave) applications.

Crosstalk Suppression Based on Mode Mismatch Between Spoof SPP Transmission Line and Microstrip

We propose an efficient method to suppress the crosstalk based on the mode mismatch between spoof surface plasmon polariton (SPP) transmission line (TL) and microstrip. Since microstrip and spoof SPP TL support quasi-transverse electromagnetic (quasi-TEM) wave and transverse magnetic (TM) wave, respectively, the transmitting electromagnetic (EM) energy can hardly be coupled between these two kinds of TLs, which helps to reduce the crosstalk. For the cases of weak and strong coupling, two kinds of structures of spoof SPP TLs are designed. To verify the performance of crosstalk suppression, two samples of the coupled TLs are presented and fabricated. Simulated and experimental results show that the crosstalk of both strong and weak coupling is reduced by approximately 35 and 30 dB, respectively, by introducing the spoof SPP TL into the microstrip pair. Thus, crosstalk in traditional circuits can be alleviated by the mode mismatch between spoof SPP TLs and microstrips, which is significant for high-speed and high-density integrated systems.

High-Performance E-Band Continuous Transverse Stub Array Antenna With a 45° Linear Polarizer

This letter presents a continuous transverse stub (CTS) array antenna with high aperture efficiency, low sidelobes, and cross-polarization characteristics over an E-band. The antenna consists of a full-corporate-feed 32-slot CTS array and a 45° linear polarizer. A multiple-aperture excited parallel-plate waveguide structure works as a linear source generator to generate the quasi-TEM wave with a uniform amplitude distribution over the whole operating band from 71 to 86 GHz. The 45° linear polarizer contains two layers of slots, shifting the linear polarization from the principal E-plane (φ = 90°) to the intended E-plane (φ = 135°). The array antenna achieves the low cross polarization and sidelobe level (SLL) while maintaining high aperture efficiency. Measurement results show that the antenna has an aperture efficiency of over 74% with the peak gains of better than 37.9 dBi over the whole E-band, while the far-field SLLs in the intended E- and H-planes approach the ETSI class IV envelope standard.

Low-Profile Wideband CTS Array Using Substrate-Integrated Waveguide Technology for $K$ -Band Applications

A low-profile wideband continuous transverse stub (CTS) array with stable radiation patterns is proposed in this communication. It is integrated on six-layer substrates by using substrate-integrated waveguide (SIW) technology, which consists of three parts: a line source generator (LSG), a power divider, and a CTS radiator. The LSG can generate a quasi-TEM wave by using an offset parabolic cylindrical reflector based on geometrical optics (GO), and the CTS radiator is fed in parallel by a 1-to-8 power divider. The performance of the proposed antenna is demonstrated by simulation and measurement. The measurement results show that the fabricated prototype achieves a wide impendence bandwidth of 32.6% from 17.2 to 23.9 GHz with a reflection coefficient below −10 dB. The measured peak gain is 22.6 dBi occurring at 22 GHz in the broadside direction. The proposed SIW-CTS array has a low-profile, high gain, low cross polarization, and a compact structure of $9.95\lambda _{0}~8.13\lambda _{0}~0.27\lambda _{0}$ , which can be applied to the wireless communication system in $K$ -band.

Traveling electromagnetic waves in annular Josephson tunnel junctions

It is well known that long Josephson tunnel junctions (JTJs) act as active transmission lines for the slow-mode propagation of magnetic flux-quanta (in the form of solitary waves) that is at the base of many superconducting circuits. At the same time, they support the propagation of quasi-TEM dispersive waves with which the magnetic flux non-linearly interact. In this work, we study the properties of the electromagnetic resonances, under different conditions of practical interest, in annular JTJs (AJTJs), in which the wavelengths are limited to the length of the circumference divided by an integer. Our analysis is based on perturbed sine–Gordon equations the (1+1)-dimensional space with periodic boundary conditions. We discuss the discrete modes of the traveling EM waves in circular AJTJs in the presence of an in-plane magnetic field, as well as in the recently introduced confocal AJTJs (in the absence of magnetic field). In both cases, a variable-separation method leads to quantitatively different Mathieu equations characterized by even and odd spatially periodic solutions with different eigenfrequencies. It implicates that a single mode circulating wave is given by the superposition of two standing waves with the same wavelengths but different frequencies, and so has a periodically inverting direction of propagation. The control parameters of this frequency splitting are the in-plane magnetic field amplitude for the circular AJTJ and the aspect ratio for the confocal AJTJs. In the appropriate limits, the previously known solutions are recovered.

Millimeter-Wave High-Gain Frequency-Scanned Antenna Based on Waveguide Continuous Transverse Stubs

A millimeter-wave frequency-scanned antenna based on continuous transverse stubs applications is presented in this communication. The waveguide CTS radiation slots are fed by a wideband quasi-TEM linear source generator (LSG). To increase the scanning angle, a nonuniform slow-wave structure is employed underneath the radiation slots to control the amplitude and phase distributions. The LSG is constructed of a parallel-plate waveguide excited by a modified three-stage 1-to-8 power divider, generating high-quality quasi-TEM wave over a wide frequency band. The beam direction is tunable with varying frequency. To validate the design, a prototype array at the Ka-band is designed, fabricated, and measured. Excellent agreement is achieved between simulations and measurements. The measured results show that the proposed array has an impedance bandwidth from 26 to 42 GHz (47%). The peak gain is 22.9–29.2 dBi, and the radiation angle can be scanned from −56.2° to −2.2°. Over the entire frequency band, the first sidelobe is suppressed to below −12.6 dB.

Wideband Full-Corporate-Feed Waveguide Continuous Transverse Stub Antenna Array

A Ka-band waveguide continuous transverse stub antenna array with full-corporate-feed network is presented in this paper. Multiple-section stepped-impedance transformers are used for wideband impedance matching of the radiation slots. The required high-quality quasi-TEM wave excitation is generated by a wideband plane-wave generator (WPWG). Compared with the conventional pillbox structure, the WPWG produces a quasi-TEM wave with more uniform amplitude distribution. By using the combination of these design features, significant increases both in bandwidth and antenna aperture efficiency are achieved. For demonstration, a prototype is designed, fabricated, and measured. Excellent agreement is achieved between simulations and measurements. The antenna is matched over the entire Ka-band of 26–40 GHz. A high antenna aperture efficiency of over 75% and a low cross-polarization of less than −46 dB are achieved over the entire bandwidth. The demonstrated features of wideband, high aperture efficiency, and low cross-polarization have great potentials for millimeter-wave applications.

On switching behavior of ferrite substrate with magnetostatic and spin wave exchange term

Due to the generation of magnetostatic and spin waves, switching phenomena of ferrite substrate with a normal magnetic biasing field is presented. Generally below the X-band of microwave range, the Pozar’s quasi TEM waves (extraordinary waves) were studied, but for the study of X-band there should be an inclusion of spin wave exchange term (ωr) in the magnetostatic wave analysis which depends upon the static internal field (Hex). This term is included in analysis because the wavelength of microwave approach is the inter-atomic distance of ferrite material. In this work we synthesize LiTi ferrite through Solid State Reaction Technique (SSRT) and obtained electric and magnetic properties for the analysis. Absorbing and transmission power coefficients have been calculated to obtain the power loss and transmitted power through the substrate, respectively. The absorbing power coefficient verifies the switching behavior of substrate for certain range of applied external magnetic field (H o) which depends on the resonance line width parameter (ΔH) of ferrite material.

Design of Narrow Wall Windows in a Waveguide to Feed Partially-Dielectric-Filled Oversized-Rectangular Waveguide Based on 2-Dimensional Analyses of Two Orthogonal Directions

A series of windows in the narrow wall of a fully-dielectric-filled rectangular waveguide to feed partially-dielectric-filled oversized-rectangular waveguide is presented. The overall structure is single-layer and 3-dimensional however; the waveguide which is uniform along the height is analyzed by the 2-dimensional method of moments and the oversized waveguide which is uniform in the longitudinal direction of the waveguide is analyzed by the 2-dimensional mode matching. It is found that utilizing simple mode conversions between the two orthogonally uniform structures is sufficient for obtaining the results similar to those of a 3-dimensional solver HFSS. The parameters for the windows designed for a uniform input division are presented. A simulation shows that a 12 window array provides a 3.5% bandwidth in terms of reflection below −20dB. The uniform excitation of the quasi-TEM wave is confirmed in the 60GHz band by measuring a uniform aperture field in amplitude and phase over the slotted oversized-waveguide.

A NEW TYPE OF THE QUASI-TEM EIGENMODES IN A RECTANGULAR WAVEGUIDE WITH ONE CORRUGATED HARD WALL

The problem of determining the eigenmodes of a rectangular waveguide with one hard wall formed by longitudinal corrugations with grooves filled with dielectric is considered. The characteristic equation is derived by using the asymptotic boundary conditions for corrugated surfaces. It is shown analytically that if the groove depth is equal to the value 0.25 lambda/(epsilon - 1)(1/2) corresponding to the hard wall condition, the TE eigenmode spectrum of the waveguide contains an infinite set of new non-uniform quasi-TEM modes with different transverse propagation constants in the empty part and identical longitudinal propagation constants equal to the wavenumber k. Analytical solution for the case of excitation of the waveguide by a specified source is given, and an example of forming local quasi-TEM waves is considered and discussed.

Exposure of Hamsters to GSM900 Signals Carried by a Quasi-TEM Wave Propagating in a Rectangular Waveguide

The development of exposure devices for investigating possible effects of mobile communication systems to nonrestrained animals aims at a homogeneous field distribution in the area the animals occupy. In the presented 900 MHz exposure device based on a modified rectangular waveguide (WR1150) a quite good field homogeneity of 5 % (including the standing wave contribution due to internal reflections) is reached in the cage region mainly by flattening the transverse field. The desired maximal whole-body specific absorption rate (SAR) of 4 W/kg in the Djungarian hamster model is achieved at an input power of only 3.7 W.

A TE/TM modal solution for rectangular hard waveguides

A TE/TM modal solution for a longitudinally corrugated rectangular waveguide is developed. These longitudinal corrugations can be used to excite a quasi-TEM wave and form a hard waveguide by correctly choosing the impedance at the guide wall. The correctly chosen impedance is referred to as the hard boundary condition. The modal solution developed here solves the problem of longitudinal corrugations filled with a dielectric material by first finding and solving the characteristic equation for a complete TE/TM modal set. It is shown that this TE/TM mode solution can be used to achieve the hard boundary condition resulting in the quasi-TEM wave in a hard waveguide for discrete values of corrugation depth. Beyond each of these depths, a mode becomes a surface wave. The theoretical mode set is amenable to the solution of problems using the mode-matching method. A combination of the mode-matching method and the TE/TM modal solution will allow the solution of larger problems.