Microwave Frequency Band Research Articles

Dynamically Tunable Phase Shifter with Commercial Graphene Nanoplatelets.

In microwave frequency band the conductivity of graphene can be varied to design a number of tunable components. A tunable phase shifter based on commercial graphene nanoplatelets is introduced. The proposed configuration consists of a microstrip line with two stubs connected with a taper. On each side of the stubs there is a gap, short circuited through a via, where the commercial graphene nanoplatelets are drop casted. By applying a DC bias voltage that alters the graphene resistance the phase of the transmitted signal through the microstrip line can be varied. In order to maximize the phase shift of the transmitted signal and minimize the insertion loss, the length of the taper and the stubs are optimized by the help of circuit model and full-wave simulations. A prototype working at 4GHz is fabricated and measured. A phase variation of 33 degrees is acquired with an amplitude variation of less than 0.4 dB.

Ink-jet printed metamaterial microwave absorber using reactive inks

Ink-jet printing technology is one of the most promising printing techniques enabling fabrication of metamaterial absorber (MMA) in a one-step and direct process. In this study and for the first time the metamaterial microwave absorbing structure is proposed using water-based reactive inks and ink-jet printing technique. The MMA based on Unite-Ring-Swastika Cross Resonator (URSCR) is printed on a copy paper. The printed MMA structure is flexible and includes an ink-jet printed silver unit cell, a dielectric layer (copy paper), and an ink-jet printed silver ground plate was formed underneath the substrate. The working principles of the unit cell of MMA and its parametric simulations are evaluated. The performance of MMA with the full-wave simulation at the microwave frequency band is assessed as well, showing great agreement with the results obtained from the measurements. The experimental results indicate that the amount of measured flexible MMA absorption based on URSCR at resonance frequency on a planar surface at 0° to 40° incident angles and on a cylindrical surface at a 0° incident angle stays over 99%.

Development of a Josephson junction based single photon microwave detector for axion detection experiments

Josephson junctions, in appropriate configurations, can be excellent candidates for detection of single photons in the microwave frequency band. Such possibility has been recently addressed in the framework of galactic axion detection. Here are reported recent developments in the modelling and simulation of dynamic behaviour of a Josephson junction single microwave photon detector. For a Josephson junction to be enough sensitive, small critical currents and operating temperatures of the order of ten of mK are necessary. Thermal and quantum tunnelling out of the zero-voltage state can also mask the detection process. Axion detection would require dark count rates in the order of 0.001 Hz. It is, therefore, is of paramount importance to identify proper device fabrication parameters and junction operation point.

Wideband (10–67 GHz) Dielectric Properties of Biosourced Cellulose Ester Flexible Films

In this article, the dielectric properties of a biosourced polymer are investigated. To that end, coplanar transmission lines were fabricated on a 600- $\mu \text{m}$ thick cellulose palmitate substrate by using a photolithographic process and a transfer technique. The ${S}$ -parameters of the transmission lines were measured in a broad microwave frequency band spanning from 10 to 67 GHz in order to determine the propagation constant. From these data, the complex dielectric permittivity was extracted by using two analytical methods (RLCG method, based on resistance, inductance, capacitance and conductance of transmission lines and conformal mapping method) and a numerical one [finite element method (FEM)]. The three methods allow distinguishing the dielectric losses from the total measured losses of the transmission lines. Finally, the dielectric constant and the loss tangent of this biopolymer were compared to the data of common and commercially available substrates: polyimide and polyethylene naphthalate.

Estudio de modelos circuitales de metamateriales bidimensiones de banda prohibida electromagnética basados en la celda de Yang

Los metamateriales en las bandas de frecuencias de microondas han sido ampliamente explorados en el diseño de antenas y arreglos de antenas. En este trabajo se ha estudiado la celda de Yang, que cuando es dispuesta periódicamente sobre un plano, conforma una estructura metamaterial que presenta bandas prohibidas de frecuencia más bajas que otras estructuras, con una mayor eficiencia en el uso del espacio. Se han estudiado los campos eléctricos y magnéticos en los primeros dos modos de propagación electromagnética de esta celda unitaria. Se han construido cuatro modelos circuitales equivalentes de la celda unitaria para poder obtener la respuesta en función de la frecuencia de la estructura metamaterial de forma rápida, que se encuentran explicados en el trabajo. Los modelos fueron validados por simulación numérica electromagnética de onda completa.

Nonlinear Cyclotron Resonance Absorber for a Microwave Subnanosecond Pulse Generator Powered by a Helical-Waveguide Gyrotron Traveling-Wave Tube

A well-known principle for periodical production of high-power ultrashort optical pulses is related to passive mode locking realized when a saturable absorber is incorporated into the laser resonator. A similar effect can be implemented in two-section electronic oscillators comprising an amplifier and a saturable absorber, which should be applicable in the microwave frequency band and suitable for high-power operation. In this paper, we analyze in detail the possibility of realizing a saturable absorber based on cyclotron resonance interaction in the regular waveguide with initially rectilinear electron beam, when saturation is caused by the relativistic dependence of the gyrofrequency on electron energy. Maximum contrast between the absorption of a high-power signal and of a weak signal is achieved in the group synchronism regime when the particle velocity is close to the wave's group velocity. Within the frame of a time-domain self-consistent model, we demonstrate that when such an absorber is installed in the feedback loop of an electron generator powered by existing Ka-band helical-waveguide gyrotron traveling-wave tube, periodical generation of subnanosecond pulses can be provided with peak power up to several hundred kW and sub-GHz repetition frequency. We discuss the influence of deviation from the group synchronism regime on the parameters of generated pulses. Experimental feasibility of the considered scheme is verified based on three-dimensional particle-in-cell simulations.

An ultra-low-firing NaBi3V2O10 ceramic and its dielectric properties at RF and microwave frequency bands

An ultra-low-firing NaBi3V2O10 ceramic, fabricated at 620 °C by a solid-state route, was studied in terms of microstructure, dielectric properties, and chemical compatibility with aluminum electrodes for the first time. NaBi3V2O10 crystalized in a primitive triclinic structure P1 and developed a dense microstructure, and exhibited good chemical compatibility with aluminum. These merits render its potential utilization in low-temperature cofired ceramic technology. However, the microwave dielectric properties of NaBi3V2O10 are unsatisfactory with er ~ 26.0, Q × f ~ 3200 GHz, and τf ~ − 88.3 ppm/°C. Based on RF dielectric characterizations of relative permittivity and impedance over a broad frequency and temperature range, the relatively low-quality factor was explained by the oxygen vacancies caused by sintering and Na and Bi volatilization. These results imply an optimization potential in dielectric properties of NaBi3V2O10 through compositional and processing adjustments. This work also provides an alternative paradigm to evaluate the performances of microwave dielectric properties.

Tunable left-hand characteristics in multi-nested square-split-ring enabled metamaterials

Left-hand materials have drawn increasing attention from many disciplines and found widespread application, especially in microwave engineering. A sandwiched metamaterial consisting of multi-nested square-split-ring resonators on the top side and a set of wires on the back side is proposed. Scattering parameters are retrieved by high-frequency structure simulator (HFSS) software based on the finite element method. Effects of square-split-ring number on the left-hand characteristics containing negative values of permittivity, permeability, and refractive index have been intensively investigated. Simulated results show that obvious resonant left-hand characteristics could be observed within 8–18 GHz, and the resonant frequency counts are inclined to be in direct proportion to the square-split-ring number over 8–18 GHz. Besides, the proposed sandwiched metamaterial with three square-split-ring resonators and three wires presents the widest frequency band of left-hand characteristics in a range of 8–18 GHz. Further, electromagnetic field distributions demonstrated that the induced magnetic dipole dominates the resonant absorption. The multi-peak resonance characteristics of square-split-ring resonant structure are considered to be a promising candidate for selective-frequency absorption or modulation toward microwave frequency band.

Design of the Ladder Multi-slot Fractal Split Growth Array Antenna

According to the performance requirements of the ultra-wideband multi-band compatible antennas for microwave band multi-network integration systems, the present paper originally combines the structure of ladder multi-slot, “Embedded” slot fractal iteration and the split growth array, designs a ladder multi-slot fractal split growth array antenna. The result of test indicates that this antenna can completely cover all working frequency bands of the mobile communication system, the frequency bands of the radio frequency identification system, the frequency band of the ultra-wideband system and the frequency band of the mobile digital TV system. With the advantages of small size, high radiation intensity and stable radiation characteristics, it can be applied to large-scale applications in the multi-network system of microwave frequency band.

Design of the Tree Growth Array Ultra Wideband Antenna

According to the performance requirements of the antenna for multi-network wireless communication terminal equipment, the present paper originally combines the structure of inductive multi-line antenna with the tree growth array, designs a tree growth array ultra-wideband antenna, and we also complete the production and the test of antenna samples. The measured results show that the antenna has stable ultra-wideband performance and can work in mobile communication systems, radio frequency identification systems, ultra-wideband communication systems and mobile digital TV systems at the same time. It has excellent compatibility and it is also a performance microwave frequency band multi-network and one terminal device antenna.

Correction to: Characterization of Liquids Using Electrical Properties in Microwave and Millimeter Wave Frequency Bands

Unfortunately, the author had missed to include the below acknowledgement text in the original publication of the article.

Coupling effects in dielectric metamaterials

Dielectric metamaterials have been proved to have broad applications in the microwave and optical frequency bands. However, as the components of the communication system shrink, the coupling effects caused by tight arrangements between the dielectric structures have not been carefully studied enough yet. In this paper, the deep coupling effects in limited space between the adjacent dielectric metamaterials cubes are investigated. According to the correlation between the coupling effect and the incident wave, the influence of coupling effect on the scattering characteristics of the structure is studied from three aspects: coupling effect parallel to the wave vector/electric field/magnetic field, respectively. Field distributions and constitutive parameters are also demonstrated to illustrate the relationship between the coupling effects and scattering coefficients.

The Contribution of Storage Medium and Membranes in the Microwave Dielectric Response of Packed Red Blood Cells Suspension

During cold storage, packed red blood cells (PRBCs) undergo slow detrimental changes that are collectively termed storage lesion. The aging of the cells causes alterations in the composition of the storage-medium in the PRBC unit. In this paper, we present the comparison of the dielectric response of water in the primary (fresh) storage medium (citrate phosphate dextrose adenine solution, CPDA-1) versus the storage medium from three expired units of PRBCs. Dielectric response of the water molecules has been characterized by dielectric spectroscopy technique in the microwave frequency band (0.5–40 GHz). The dominant phenomenon is the significant increase of the dielectric strength and decrease the relaxation time τ for the samples of the stored medium in comparison with the fresh medium CPDA-1. Furthermore, we demonstrated that removing the ghosts from PRBC hemolysate did not cause the alteration of the dielectric spectrum of water. Thus, the contribution associated with water located near the cell membrane can be neglected in microwave dielectric measurements.

Антенная система диапазонов сверхвысоких и крайне высоких частот с широкоугольным сканированием

Two variants of dual-band antenna systems with a common aperture are considered and compared. The common is that in the both variants there are used: two-reflector system with rotation of polarization plane for exсitation of extremely high frequency band electromagnetic waves and slotted-waveguide array for excitation of microwave frequency band electromagnetic waves. Twist-reflector of extremely high frequency band is combined with aperture of slot-waveguide array. The difference of the proposed variant of antenna system is use of a flat transreflector and a twistreflector, which is a multi-element polarization array and has little effect on the characteristics in the microwave range. The structure of flat transreflector is based on multi-layer zoned Frenel antenna. The both variants of antenna system allow to realize a wide-angle space scanning. Manufacturing of antenna system with flat multi-layer transreflector is greatly simplified with the help of well-developed technology for the production of printed circuit boards. There are presented the results of computer simulation that show the possibility of practical realization of the proposed antenna systems.

Role of Magnetite (Fe3O4)-Titania (TiO2) hybrid particle on mechanical, thermal and microwave attenuation behaviour of flexible natural rubber composite in X and Ku band frequencies

This current work aims to prepare a flexible elastomeric microwave shielding composite material with good mechanical and thermal properties by dispersing Fe3O4 and titania hybrid nano-particles. The primary aim of this research work is to prepare a high strength and high thermal stable flexible natural rubber composite with higher wave attenuation coefficient against ‘X (8–12 GHz)’ and ‘Ku (12–18 GHz)’ band microwave frequencies. The Fe3O4-Titania hybrids were prepared using low energy ball milling and the hybridization effect was confirmed using transmission electron spectroscopy. The prepared Fe3O4-Titania hybrids were surface-treated using 3-Aminopropyltriethoxysilane via wet solution method to avoid agglomeration. The natural rubber flexible composite was made by two-roll milling with recommended process parameters. The mechanical and thermal results showed improved tensile strength, modulus and mass decomposition. The highest tensile strength of 60 MPa was observed for composite contains 1.0 vol% of Fe3O4–TiO2 particles. Similarly, the highest thermal stability of 385 °C is observed for composite contain Fe3O4–TiO2 particles. The X and Ku band microwave attenuation behaviour revealed the highest attenuation of 28.1 dB for 1.0 vol% of Fe3O4–TiO2 particle dispersed rubber composite in Ku band frequency. These mechanically toughened thermally stable and high microwave attenuation flexible composites could be used as EMI shielding material at antennae and other telecommunication devices where electromagnetic wave interference creates crucial issues.

Paper Based Chipless RFID Leaf Wetness Detector for Plant Health Monitoring

This paper presents the design and analysis of a paper-based chipless RFID sensor for wetness content measurement in plant leaves. The sensor is designed using a passive microwave resonator to measure the ambient physical parameter. The resonator is designed with a rectangular loop inductively coupled with an interdigital capacitor. The experimental analysis of the designed sensor is illustrated here to prove its efficacy. The resonator provides adequate backscattered signal for wireless measurement in the microwave frequency band. When interrogated with a couple of UWB antennas and a VNA, it yields accurate leaf wetness response of the plant. The commercial competence of this sensing device is validated through its experimental analysis on three different types of leaf samples. This sensor is suitable for plant health monitoring in any small-scale gardening applications such as nurseries and greenhouses.

Comparative Study of Optimization Algorithms on the Design of Broadband Antennas

Broadband antennas find many applications in modern communication systems, such as Wi-Fi, 5G, and SatCom. Multiple competing optimization methods are available for the application to antenna design, while it would be preferable to know in advance if any method is superior. Here, an application of the cross-entropy method, along with particle swarm optimization and covariance matrix adaptation evolutionary strategy, to the design of broadband antennas is presented. The first example is an aperture-coupled microstrip patch antenna that has 9.5 dBi peak directivity and 53% bandwidth after optimization. It is then used as a feed in a high-gain broadband resonant cavity antenna. Using an all-dielectric superstrate with a transverse permittivity gradient, a compact thin resonant cavity antenna with a peak directivity of 19 dBi and 40% 3-dB bandwidth was designed. A comparative analysis of the cross-entropy method, particle swarm optimization, and covariance matrix adaptation evolutionary strategy applied to these two problems was carried out to provide the basis for further optimization of antennas in radio frequency and microwave frequency bands. We found that although all three methods reached a similar solution, the cross-entropy method has a speed advantage. It improves our ability to optimize existing designs and has wider applicability beyond antenna engineering.

L / C / X Triple band compact dipole array antenna for RADAR application

This article describes about L / C / X triple band compact dipole array antenna for RADAR communication using FR-4 Substrate. The proposed antenna is designed over a range of 1.0–10.0 GHz. The objective of the paper is to achieve appreciable basic antenna parameters for ease adaptation in Monolithic Microwave Integrated Circuits (MMIC) Technology. It is able to preserve its high recital over RADAR Communication system operating at Triple band (L, C, X – band) microwave frequency range. The proposed structure resonates at L / C / X Microwave bands and thus the antenna becomes inevitability for numerous wireless applications. The antenna is fictitious on a substrate with height of 1.6 mm, length 48mm, width 60mm and a relative permittivity of 4.2. The proposed antenna yields a VSWR of about 1.74 (1.70 GHz), 1.66 (6.70 GHz), 1.26 (8.30 GHz) and gain of 2.56 dBi (1.70 GHZ), 1.78 dBi (6.70 GHz) and 3.94 dBi (8.30 GHz) under simulation. The antenna is designed and simulated using HFSS, which helps to obtain the antenna parameters such as VSWR, gain and Return loss.

Stretching, Amplification, and Compression of Microwave Pulses Using Helically Corrugated Waveguides

We demonstrate the possible implementation of the chirped pulse amplification (CPA) method, which is widely used in optics, for the microwave frequency band. This method is based on the preliminary elongation of the incident pulse in the stretcher, sequential amplification of spectral components in a wideband amplifier, and final compression in a line with negative dispersion (compressor). A circuit is considered in which multifold, helically corrugated waveguides are used as an operating space in each section, including a stretcher, an amplifier, and a compressor. The dispersion characteristics of such waveguides can vary significantly when its geometrical parameters are changed, which makes it possible to ensure optimal dispersion characteristics in the stretcher and compressor, as well as the largest gain bandwidth in the amplifier. In addition, these dispersive elements allow us to avoid spurious reflection of the signal due to the absence of a stopband in the operating frequency range. Simulations within the framework of the coupledwave approach showed the prospects of the circuit proposed. In particular, using an experimentally realized 30-GHz gyro-TWT, the peak power of a 200-ns, 300-W incident pulse can be increased up to 4 MW, which is about six times higher than the power of the driving electron beam. With direct amplification (in the absence of a stretcher and a compressor) of the specified incident pulse in the same gyro-TWT, the output peak power does not exceed 250 kW.

Graphene-Based Microwave Antennas With Reconfigurable Pattern

This article presents a graphene-based, dynamically reconfigurable antenna with a voltage-controlled, far-field radiation pattern in the microwave frequency band. The proposed antenna consists of two radiating patches and a planar feed network mainly composed of a graphene-based attenuator and a power divider with a hybrid graphene–metal phase shifter. The output phase of the phase shifter changes by a bias voltage on the graphene. The antenna has two operating states with different beam directions when the bias voltage is between 0.7 and 5 V. The equivalent circuit model is employed to analyze the phase shift characteristic of the graphene–metal phase shifter. Then the prototype of the reconfigurable antenna is fabricated and tested. The experimental results are in good agreement with the simulated ones. This article demonstrates that in the microwave frequency band, by proper design, the graphene–metal structure can be used to realize the new type of the reconfigurable antenna, in which this kind of graphene-based tuning structure can be easily stacked with other circuits by a simple pasting technique than soldering. This feature has potential applications in flexible radio frequency system in future.