Circular ring shaped ultra-wideband metamaterial absorber with polarization insensitivity for energy harvesting

<span>A circular ring-shaped metamaterial (CRM) absorber was designed to harvest radio frequency (RF) energy in the ultra-wideband (UWB) frequency band applications. The proposed metamaterial unit cell features a circular shaped structure, with rectangular strip lines connected in the form of a cross leaving a square shaped slot at center. The unit cell dimensions are 15×15×1.6 mm. The absorber was etched on a low cost FR4 substrate having a dielectric constant of 4.4. Ansys high frequency structure simulator (HFSS) software was used for simulation and the analysis were carried out for unit cell, 2×2, 3×3, and 4×4 array structures. The absorber parameters plotted are absorption characteristics and reflection characteristics. Also, the metamaterial parameters (μeff) and (εeff) are also retrieved from the absorber parameters and analyzed. From the analysis, the values (μeff) and (εeff) were found to be negative, leaving refractive index also negative (n&lt;0), which proved the metamaterial property. The proposed CRM absorber showed good absorption characteristics of more than 80% and also metamaterial property in the entire UWB band (4-13 GHz). Hence the absorber proves to be a good candidate in powering low power sensors/microcontrollers for internet of things (IoT) applications.</span>

Design and Implementation of High Directivity Directional Coupler at VHF Band Using Grounding Composed of Strip Lines Technics

This paper proposes a design of high directivity directional coupler (D.C) based on grounding composed of strip lines for high power Radar transmitter at Very High Frequency (VHF), (150 – 200 MHz). The directional coupler is used to check and verify the transmitter output high power, frequency, and reflected signal from an antenna connected with the Radar transmitter. The performance requirements of directional couplers are a strong coupling to reduce the effect on the transmitted output power and high directivity to suppress the interference of the reflected signal from the antenna. So far, various architectures have been proposed to gain high directivity, and there have been many studies used to obtain a strong coupling and higher directivity. However, the conventional architecture of the directional coupler has a directivity of only about 20 dB, and there have been difficulties to achieve the higher directivity of more than 20 dB. In this paper, the proposed architecture of directional coupler based on grounding composed of strip lines is discussed and compares the test results of the proposed directional coupler with the conventional one. The high directivity directional coupler is designed using a computer-aided design Simulation program; Advance Design System (ADS 2016), using Rogers 4003 substrate. The directional coupler was fabricated on printed circuit board (PCB) technology and measured using a vector network analyzer (VNA). The results show that the proposed directional coupler has directivity between -25 to -24 dB inside the working bandwidth and is adequate for a high-power radar transmitter.

Investigation of the Two-Mode Regime of Two-Gap Photonic-Crystal Resonance Systems Produced on a Printed Circuit Board with Fractal Elements "Minkowski Island

Introduction. The development of new amplifiers and generators of the Ku- and K-bands (12…27 GHz) for use in onboard equipment is increasingly attracting research interest. Low-voltage multi-beam klystrons (LMBK) can be a promising element base for such devices. Serious problems are associated with the need to suppress parasitic modes of oscillations in NMLK operating in the centimeter and millimeter range. A possible solution is to use double-gap photonic-crystal resonators (DPCR) in LMBK. Another promising direction for improving the characteristics of such resonators is to use resonant segments of strip lines with fractal elements. In this case, the strip lines are placed on a dielectric substrate in the interaction space. Such resonators exhibit new properties that are useful for klystrons (an increase in characteristic impedance, suppression of the spectrum of unwanted frequencies, a reduction in mass and dimensions).Aim. Determination of an optimal set of electrodynamic and electronic parameters of double-gap photonic-crystal resonance systems with fractal elements "Minkowski Island" when operated as part of the LMBK resonator system, excited on π- and 2π-modes of oscillation.Materials and methods. To calculate the electrodynamic parameters of resonators, the method of finite differences in the time domain was used. The well-known Wessel-Berg method was used to calculate electronic parameters, such as the Ge / G0 electronic conductivity and the coupling coefficient M.Results. The main electrodynamic parameters of the resonator – Q-factor, resonant frequency and characteristic impedance – were investigated. The electronic parameters of the resonator, the coefficient of coupling with the electron beam, and the relative electronic conductivity for π- and 2π-modes of oscillations were calculated. In this case, three variants of the resonator with zero, first and second iterations of the fractal element were investigated. The amplitude-frequency characteristics of the resonator were investigated with a change in the pitch of the photonic crystal lattice. An estimation of the inhomogeneity of the high-frequency field in the interaction spaces of the resonator was carried out. Operational conditions were determined simultaneously for two types of oscillations without self-excitation.Conclusion. The results can find application in the development of resonator systems for klystron-type devices in the centimeter and millimeter ranges.

Directional microwave coupled-line couplers with high lateral coupling level

Classic сoupled-line couplers with a high lateral coupling level by type of directivity are counterdirectional. Restrictions on their synthesis are imposed by the gap between transmission lines, which must be extremely small (tens of microns), the difference in the phase velocities of even and odd modes, which must be compensated and others. This makes it difficult of manufacturing couplers. Described in technical literature сoupled-line couplers with a high lateral coupling level with changed types of directivity are either quite bulky or have small dimensions due to the use of discrete inductors and capacitances, which complicates the technological process with surface mounting when implementing the final device. In this article we propose a compact сoupledline coupler with a high lateral coupling level, which implements power transfer to a single port (0 dB, crossover). The coupler topology uses periodic loops that are located between сoupled-line. The equivalent circuit of the coupled lines was calculated and analyzed for a single periodic stub. This allowed us to determine the necessary parameters and dimensions of the topology. The device is narrow-band (3 GHz ± 5 %), transmission coefficient minus 0.44 dB at the center frequency of 3 GHz, isolation for isolated ports is not less than 35 dB. The proposed compact coupler with a coupling level of 0 dB suits building distribution circuits in which it is necessary to exclude the intersection of transmission lines. The information on the synthesis of the 3 dB co-directional microwave coupler on coupled strip lines with lateral electromagnetic coupling is given. The coupler is characterized by a high isolation level with an isolated port, not less than 40 dB. The imbalance of the amplitudes between the working (through and connected) and the input port is minus (3.4 ± 0.8) dB.

MODELING THE FREQUENCY CHARACTERISTICS OF THE QUADRATURE THREE-LOOP L-BAND WAVELENGTH BRIDGE

Представлены результаты численного моделирования частотныххарактеристик квадратурного трехшлейфового моста (КШМ) L-диапазона, выполненного на основе симметричной полосковой линии с воздушным заполнением. Цель работы - установление допустимого уровня вносимых тепловых потерь полосковых линий (или других типов линий передачи), не оказывающих заметного влияния на рабочие характеристики КШМ, удовлетворяющие требуемым параметрам. Метод расчета основан на принципе декомпозиции электрической цепи КШМ на шесть симметричных 6-полюсников, три из которых соответствуют нечетной моде возбуждения КШМ, а три других - четной моде возбуждения КШМ. Алгебраическое суммирование матриц рассеяния указанных мод позволило получить частотные характеристики результирующей S-матрицы рассеяния КШМ. Нормирование S-матрицы к стандартному волновому сопротивлению 50 Ом выполнено с помощью вычисления собственных значений матриц рассеяния эквивалентных 4-полюсников КШМ. Моделирование проведено в среде LabVIEW. The paper presents the results of numerical simulation of the frequency characteristics of the L-range quadrature three-loop bridge (QLB), based on the symmetric striped line with air filling. The purpose of the study is to establish the permissible level of introduced thermal losses of strip lines (or other types of transmission lines) that do not significantly affect the performance characteristics of the QLB, satisfying the required parameters. The calculation method is based on the principle of decomposition of the QLB electric circuit into six symmetric 6-poles, three of which correspond to the odd excitation mode of the QLB, and the other three correspond to the even excitation mode of the QLB. Algebraic summation of the scattering matrices of these modes made it possible to obtain frequency characteristics of the resulting S-scattering matrix of the qLb. The normalization of the S-matrix to the standard wave resistance of 50 Ohms was carried out using the calculation of the eigenvalues of the scattering matrices of equivalent 4-poles of the QLB. The simulation was carried out in the LabVIEW environment.

A printed lens in antenna’s aperture to improve the performance of UWB-radar system

Abstractwe present a printed lens for radar applications. The structure of the presented lens consists of an array of modified micro-strip lines, which is positioned in the antenna’s aperture on the same planar substrate. Simulations show that the gain and directivity increase with the proposed lens in a wide band frequency band. The proposed design is insensitive to rotation of the antenna. This paper focuses on real industrial applications and problems. Further, we show that the lens can be used to improve the object detection ability of an ultrawide band radar system, which is used in industrial applications such as non-destructive monitoring of built-structures and for use in the renovation process. The signal to noise ratio is improved. Furthermore, we show how the microwave lens can also be used to reduce the clutter in applications where the complex refractive index of objects is determined. Further, different simulated results (for different cases) are compared, presented and concluded.

Coupled Strip Lines with Highly Unbalanced Electromagnetic Coupling and their Use

<p></p><p> Trinh To Thanh (Vietnam) postgraduate student of the Tomsk State University of Control Systems and Radioelectronics (TUSUR), Department of Components Design (KUDR), Radio Engineering Faculty (RKF), Russian Federation. The research topic is coupled strip lines with heterogeneous parameters in the cross-section and in longitudinal sections.</p><p></p>

Coupled Strip Lines with Highly Unbalanced Electromagnetic Coupling and their Use

<p></p><p> Trinh To Thanh (Vietnam) postgraduate student of the Tomsk State University of Control Systems and Radioelectronics (TUSUR), Department of Components Design (KUDR), Radio Engineering Faculty (RKF), Russian Federation. The research topic is coupled strip lines with heterogeneous parameters in the cross-section and in longitudinal sections.</p><p></p>