Slot Transmission Line Research Articles

Radio Frequency Tag Based on an Impedance Transformer and a Slot Transmission Line

A radio frequency tag (33 x 30 x 5 mm) operating at a frequency of 867MHz has been developed. The design of the tag consists of the radiating part of the antenna in the form of metal plates forming a capacitor, a slot transmission line that is part of a highly inductive impedance transformer, a conducting circuit, the ends of which are connected to the chip, and a chip. The proposed transformer is designed to convert the capacitive impedance of the chip into a high-quality inductance, which can be connected to the emitting element in the form of a capacitance. The slot transmission line practically forms a quarter-wave section. A nu­merical calculation of the proposed tag was carried out and a method for achieving complex matching of the impedances of the chip and the rest of the tag was presented. The matching of the active and reactive components of the impedances occurs in independent ways: by varying the size of the slot transmission line and the width of the jumper that is part of the conducting circuit. The measurement of the tag developed by modeling was carried out. The results showed that the tag can be read from a distance of several meters when it is placed on various dielectric surfaces.

A phase shift keying modulator integrated single‐feed circular polarization agile array antenna

AbstractThis paper proposes a novel design of a circular polarization agile array antenna using two phase shift keying (PSK) modulators. The proposed antenna includes four dual linear polarization microstrip patch antenna elements, two PSK modulators, two quarter‐wavelength slot transmission lines, microstrip‐slot line transitions, and a single feed network. The PSK modulator generates phase switching of either 180° or 0° of the vertical signals of each antenna element with the aid of the four diodes. The quarter‐wavelength slot transmission lines are added to adjust the 90° phase difference between orthogonal signals of the array antenna. By controlling the PSK modulators, the proposed antenna can achieve dual circular polarization switching capabilities. A prototype antenna is used to demonstrate the antenna concept. The measured results confirm the concept with a good agreement between the simulated and measured performances. The proposed antenna has no complex circuits for RF and DC signals, and it provides a compact structure.

High‐Precision Complementary Metamaterial Sensor Using Slotted Microstrip Transmission Line

Metamaterial‐based microwave sensor having novel and compact structure of the resonators and the slotted microstrip transmission line is proposed for highly precise measurement of dielectric properties of the materials under test (MUTs). The proposed sensor is designed and simulated on Rogers’ substrate RO4003C by using the ANSYS HFSS software. A single and accumulative notch depth of ‐44.29 dB in the transmission coefficient (S21) is achieved at the resonant frequency of 5.15 GHz. The negative constitutive parameters (permittivity and permeability) are extracted from the S‐parameters which are the basic property of metamaterials or left handed materials (LHMs). The proposed sensor is fabricated and measured through the PNA‐X (N5247A). The sensitivity analysis is performed by placing various standard dielectric materials onto the sensor and measuring the shift in the resonant frequencies of the MUTs. A parabolic equation of the proposed sensor is formulated to approximate the resonant frequency and the relative permittivity of the MUTs. A very strong agreement among the simulated, measured, and calculated results is found which reveals that the proposed sensor is a highly precise sensor for the characterization of dielectric properties of the MUTs. Error analysis is performed to determine the accuracy of the proposed sensor. A very small percentage of error (0.81%) and a very low standard deviation are obtained which indicate high accuracy of the proposed sensor.

Compact Dual-Band Tapered Open-Ended Slot-Loop Antenna For Energy Harvesting Systems

In this study, a compact dual-band combined loop-slot planar antenna is proposed. (1) Background: multi-function antennas are desired for wireless communication to cover the desired frequency spectrum. (2) Methods: the proposed antenna consists of a semi-rectangular open-ended loop (OEL) operating at the lower frequency band 920 MHz, an open-ended slot (OES) transmission line that provides resonance at the higher band 2.4 GHz, and a feeding port using the asymmetric coplanar strip (ACS) line. The ACS is used to excite the antenna to achieve dual-band performance. The overall dimensions of the fabricated prototype are 32.5 × 53.5 mm2 (0.1λo×0.16λo), where λo represents the free-space wavelength at the lower frequency. (3) Results: from the calculations, the antenna shows two impedance bandwidths (estimated at −10dB) of 30 MHz (920–950 MHz) and 300 MHz (2.2–2.5 GHz) to cover the ISM band (920 MHz) and 2.45 GHz WiFi bands, respectively. Indeed, the antenna has stable radiation patterns and achieves peak measured realized gain of 1.8 dBi in the lower band and 4.2 dBi in the higher band. (4) Conclusion: the antenna shows the merits of low profile structure, single-layer, and low-cost fabrication. The proposed antenna not only achieves incremental increase in radiation efficiency, but also provides a lightweight, and small footprint.

The Investigation of the Volumetric Strip-Slot Transition with U-Shaped Slot Resonator

The application of volumetric strip-slot transition for the implementationof wireless devices with contactless frequency-selective transmission of microwave signals is relevant. This is due to the compactness of volumetric strip-slot transition achieved by the multilayer arrangement of its functional parts and of its electrical frequency-selective characteristics. At the same time the volumetric-modular design allows the replacement of its individual components which provides high functional flexibility of the device. Reducing of weight and dimensions of the volumetric strip-slot transition while maintaining its electrical characteristics is possible due to well-known methods used in microwave technology: 1) using of substrates with a high value of the relative permittivity, 2) due to the transition to higher frequency ranges. The authors of this paper present the third method for reducing of weight and dimensions of the volumetric stripslot transition by using a U-shaped slot resonator. The development of the equivalent circuit of the volumetric strip-slot transition and calculation of all its lumped elements are also presented. The values of such lumped elements as linear capacitance of the strip line, linear inductance of the strip line, characteristic impedance of the slot transmission line were determined. The value of the inductive inhomogeneity occurred when the slot resonator bends by 90 degrees was calculated and its S-parameters in the frequency range were simulated. Numerical electrodynamics simulation was performed to confirm the validity of the results of circuit simulation. Then the experiment research of the sample of the volumetric strip-slot transition with the U-shaped slot resonator was carried out. The theoretical and experimental results of the conducted researches of volumetric strip-slot transition with the U-shaped slot resonator are in good qualitative and numerical agreement with each other. The use of the U-shaped slot resonator provides an opportunity to achieve a 36% reduction of weight and dimensions parameters of the volumetric stripslot transition while maintaining its electrical characteristics.

COMPACT DIRECTIONAL COUPLERS USING COMBINATION OF MICROSTRIP AND SLOT LINES

Context. Transition of modern electronics to higher frequencies is directly related with an extremely important problem of miniaturization of microwave integrated circuits. Conventional planar structures such as microstrip directional couplers have the feature – their linear dimensions are defined by the wavelength in the transmission lines, so the use of such structures for miniaturization of microwave integrated circuits becomes problematic. Objective. Using 3D-structures on combinations of transmission lines to study frequency properties of two possible implementations of quarter-wave directional couplers based on a combination of microstrip and slot transmission lines. Obtaining simple analytical expressions for calculating the electrophysical parameters of these directional couplers and confirm their properties by rigorous electrodynamic calculation. Methods. An even-odd mode decomposition technique and the scattering matrix theory were used to derive simple analytical formulas for calculating impedances of transmission line segments that define the topology of couplers considered. Results. Electrodynamic modeling of proposed couplers with dispersion and losses in the lines showed that the proposed constructions have better frequency characteristics in comparison with traditional three-branch microstrip directional couplers. It is also shown that the considered designs of couplers have great potential in the selection of the desired electrical characteristics of devices. Conclusions. The presented compact couplers can find a broad range of applications in mobile communication systems for decoupling of channels, division of power and frequency conversion. The method of transition from planar to three-dimensional structures used in the development of directional couplers on combinations of transmission lines permits not only to create compact devices with desired characteristics but also paves the way for significant decrease in the size and costs of the broad range of electronic equipment utilizing such couplers.

Tamm States in Bragg Heterostructures on Waveguide Slot Lines

Tamm surface states are experimentally studied and calculated for a Bragg heterostructure consisting of two groups of periodic fragments of waveguide slot transmission line with finite sizes. The Tamm surface states are not observed in a perfect Bragg heterostructure. The Tamm surface states emerge in the presence of an interface element at the interface of two Bragg structures when the characteristics of the element differ from the characteristics of both Bragg structures.

Synthesis of Combined Radiating and Filtering Structures Based on a Symmetric Slot Transmission Line

A model of a travelling wave printed slot antenna based on a symmetrical slot transmission line is considered. It is shown that a longitudinal segmentation allows to develop an analytical method of synthesis in the frequency domain, based on the approaches of smooth irregular transmission lines theory. A general method of synthesis is presented, and its specific features related to the slot line characteristics and an unknown distribution of the propagation constant are addressed. Method approbation was successfully demonstrated by synthesis of ultra-wideband structures with predetermined rejection bands.

Blinding and Depolarization Effects in Vivaldi Antenna Arrays

The blinding and depolarization effects in a two-dimensional unipolarization Vivaldi antennas array are studied numerically. By the numerical electrodynamic simulation, it is shown that, in the quasiperiodic mode, the reflection coefficient in such an array has narrow-band peaks, which lead to a dramatic reduction in the transmission coefficient to free space. It is established that, when scanning beyond the main planes in a frequency band, significant changes in the polarization characteristics, which can change the polarization of the radiation field, are observed. An approximate model describing the electromagnetic processes in the array as an interaction of the eigenwaves of a system of coupled slot transmission lines is proposed. It is shown that the model proposed makes it possible to describe qualitatively and, in some cases, quantitatively the blinding and depolarization effects.

Eigenmodes of a 2D array of coupled slot lines in the impedance approximation

A 2D periodic array of coupled slot transmission lines is considered in the approximation of equivalent boundary conditions. The eigenmode problem for an array operating in the quasi-periodic mode is formulated and solved. The dispersion equation for eigenmode propagation constants and expressions for eigenmode fields are obtained. The behavior of eigenmodes in a frequency band and in a range of values of geometric parameters is analyzed. The orthogonality of eigenmodes is shown. Theoretical results are compared to the results of numerical calculation performed with the use of electromagnetic simulation systems.

Theoretical investigation of thin-film multiferroic heterostructures based on a width-modulated slot transmission line

The microwave properties of multiferroic magnonic crystals based on a width-modulated slot-line were investigated theoretically for the first time. Dispersion characteristics of spin-electromagnetic waves propagating in the heterostructures were calculated. It was shown that band gaps in the spin-electromagnetic wave spectrum are controlled with both electric and magnetic fields.

Tapers in waveguides with sharp edges

The cross-section method is extended to the case of waveguides containing sharp metal edges. Such structures comprise strip lines, microstrip lines, and slot transmission lines. Relationships for eigenmode coupling coefficients in a section with parameters varying in the longitudinal direction are derived by passing to the limit: from a waveguide with smooth contour of the cross section to a waveguide with sharp edges. These relationships are applied to a single-mode strip line with conductor having variable width. It is shown that the obtained results agree with the results of the theory of microwave transmission lines.

Microwave photonic crystal on the slot transmission line with a ferroelectric film

A microwave electrically tunable photonic crystal based on a periodically width-modulated slot transmission line with a ferroelectric film is investigated for the first time. The dispersion and transmission characteristics of electromagnetic waves propagating in such a structure are calculated. The electric control over photonic crystal characteristics is simulated.

A Dual-Band Low-Profile Aperture Antenna With Substrate-Integrated Waveguide Grooves

This communication presents a new dual-band low-profile aperture antenna with relatively high gain using substrate-integrated waveguide (SIW) corrugated structures. It consists of a cavity excited by a transmission line and four SIW grooves that produce good reflection coefficient and enhanced gain. By designing corrugated structure using constructive superposition of electric fields of patch and grooves, the antenna with high performance in both bands is achieved. In the proposed structure, three simple printed circuit boards (PCBs) for implementing a resonant transmission line and specific SIW structures are employed instead of waveguide feeder and grooves on metallic plate in conventional corrugated antennas. Removing the metallic plate reduces the weight and cost of the structure and provides ease of fabrication. Dual-band characteristic is achieved using resonant slot (cavity) and resonant transmission line. Fabrication results show that the SIW grooves significantly increase the antenna gain with respect to the simple slot antenna.

Dispersion characteristics of spin-electromagnetic waves in planar multiferroic structures

A method of approximate boundary conditions is used to derive dispersion relations for spin-electromagnetic waves (SEWs) propagating in thin ferrite films and in multiferroic layered structures. A high accuracy of this method is proven. It was shown that the spin-electromagnetic wave propagating in the structure composed of a thin ferrite film, a thin ferroelectric film, and a slot transmission line is formed as a result of hybridization of the surface spin wave in the ferrite film and the electromagnetic wave in the slot-line. The structure demonstrates dual electric and magnetic field tunability of the SEW spectrum. The electric field tunability is provided by the thin ferroelectric film. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the slot-line gap width. The theory is confirmed by experimental data.

Planar arrays of Vivaldi antennas in the single-mode approximation

Periodic arrays of Vivaldi antennas are considered. Planar arrays infinite along two coordinates are analyzed. A planar array is studied with the use of a well-known model in the form of the Floquet waveguide with variable parameters. Propagation of the fundamental mode of this structure is described in the single-mode approximation in which only forward and counter-propagating fundamental modes are taken into account. An equivalent circuit of the Floquet waveguide with variable parameters is proposed. The concept of the characteristic impedance of the wave of an array of slot transmission lines is introduced and used for calculation of the scattering matrix of the Floquet waveguide with variable parameters. Results of numerical calculations are presented.

Quasi-static analysis of the eigenmodes of an array of coupled slot transmission lines

The problem of the eigenmodes of an infinite 2D array of slot transmission lines operating in the quasi-periodic mode is solved. The boundary-value problem is reduced to a system of integral equations for longitudinal components of the electric current on metal conductors and the magnetic current in slots. The system of integral equation is solved in the static approximation at the first stage and, afterwards, the solution to the electromagnetic problem is found using the Galerkin method. The results of the numerical analysis of the dependences of eigenmode propagation constants on geometric parameters of the structure and phase shifts between the array channels are analyzed.

Propagation Characteristics of Superconducting Slotlines in Vortex State

The propagation characteristics of a slotline structure under the influence of a static magnetic field have been studied using the model developed by Mark W. Coffey and John R. Clem. The complex valued resistive boundary condition formulated using the Coffey and Clem (CC) model is used to modify the dyadic Green’s function in the spectral domain for the slot transmission line. The propagation characteristics are then calculated using the Galerkin’s procedure. The numerical results are presented for propagation parameters and quality factor for a wide range of applied field, reduced temperature and superconducting layer thickness. The increase of the magnetic field and temperature causes an increase in vortex motion which results in a corresponding change in the propagation parameters and quality factor. The variation in the quality factor with respect to the superconducting strip thickness is explained using vortex effects.

Excitation of High-Q Whispering Gallery Modes in a Hemispherical Shielded Dielectric Cavity Using a Slot Transmission Line

We studied experimentally the electrodynamic characteristics of a hemispherical shielded dielectric cavity in the 8-mm wavelength range. The use of a slot transmission line is proposed to excite whispering gallery modes in such a cavity. It was found that the proposed excitation method is efficient and allows one to generate high-Q higher modes in a shielded dielectric cavity introducing no additional energy losses. It was shown experimentally that the achieved intrinsic Q-factor of the cavity under consideration can exceed the threshold values limited by the dissipative losses in its material. This effect is determined by the shift of the resonance field to the air gap between the metal and dielectric elements of the cavity. Agreement of the calculated and experimental data is demonstrated.

A microwave phase shifter based on a planar ferrite-ferroelectric thin-film structure

Microwave phase shifters employing slot transmission lines based on thin ferroelectric films of barium strontium titanate and thin single-crystalline films of yttrium iron garnet ferrite have been experimentally studied for the first time. The phase shifters admit double electronic control based upon the phenomenon of hybridization of the electromagnetic wave propagating in a slot delay line on the ferroelectric film and the spin wave propagating in the ferrite film. At a bias voltage of 150 V applied to electrodes of the slot lines with 50- and 150-μm-wide slots, the phase shift amounted to 53° and 26°, respectively.