Search

Terahertz Technology is a promising newer technology for various applications in wireless and radar communication namely tracking and detecting radar targets. The challenging aspect of radar transmitters in the target detection process is spurious harmonic signals that affect the communication path between radar transceivers. The spurious signal can be neglected by a strong filtering method. Filtering is vital in radar transmission to avoid high spurious emission level signals. Low pass filtering at terahertz frequency range (LPFT) in microstrip structure defined in the chapter analysis to avoid the harmonics above the cut-off frequency. In this chapter, the analysis part of microstrip structured LPFT is implemented under finite difference time domain analysis at (0.3 THz to 0.5 THz) cut-off frequency. Finite difference time domain (FDTD) is the three-dimensional approach commonly used for the analysis in higher frequency applications. In this FDTD method, Maxwell equation's partial derivatives are centred to finite frequency by discretization. LPFT 3D-plot is characterized by the signal factors of the input signal, reflected signal, and passed signal concerning time. Scattering parameters|s11| and|s21| are characterized by frequency and magnitude plots with an insertion loss of 0.3 dB. Full-wave analysis of LPFT is compared with Chebyshev and Butterworth filter at terahertz cut-off range is implemented. The comparison plot of attenuation versus relative frequency and characteristic impedance versus dielectric constant is shown with FDTD results with good agreement. [ABSTRACT FROM AUTHOR]

A series of Schottky diodes based on single GaN nanowires has been fabricated. Based on the data of small-signal frequency analysis (parameter S21) of diode structures at various bias voltages, the parameters of the corresponding equivalent electrical circuit were determined. It is shown that the cutoff frequency of the fabricated diodes reaches 27.5 GHz. [ABSTRACT FROM AUTHOR]

In this letter, a rectangular waveguide with controlled negative group delay (NGD) is proposed. The equivalent circuit of the structure is proposed and analyzed. The NGD value and NGD center frequency can be adjusted continuously by the corrugation width and height. Simulation results showed that NGD values of up to −0.7 ns were achievable. The fractional bandwidth was up to 5.67%, at which point the NGD response was observed. A prototype of the proposed structure was fabricated and characterized. Results showed that the fabricated structure was capable of generating a group delay of up to −0.09 ns at 18.9–20 GHz, which was consistent with theoretical and simulated predictions. To the best of our knowledge, this is the first time negative group delay has been achieved in the microwave‐band in a rectangular waveguide. [ABSTRACT FROM AUTHOR]

This paper presents a new design for a dual-band double-cylinder dielectric resonator antenna (CDRA) capable of efficient operation in microwave and mm-wave frequencies for 5G applications. The novelty of this design lies in the antenna's capability to suppress harmonics and higher-order modes, resulting in a significant improvement in antenna performance. Additionally, both resonators are made of dielectric materials with different relative permittivities. The design procedure involves the utilization of a larger cylinder-shaped dielectric resonator (D1), which is fed by a vertically mounted copper microstrip securely attached to its outer surface. An air gap is created at the bottom of (D1), and a smaller CDRA (D2) is inserted inside this gap, with its exit facilitated by a coupling aperture slot etched on the ground plane. Furthermore, a low-pass filter (LPF) is added to the feeding line of D1 to eliminate undesirable harmonics in the mm-wave band. The larger CDRA (D1) with a relative permittivity of 6 resonates at 2.4 GHz, achieving a realized gain of 6.7 dBi. On the other hand, the smaller CDRA (D2) with a relative permittivity of 12 resonates at a frequency of 28 GHz, reaching a realized gain of 15.2 dBi. The dimensions of each dielectric resonator can be independently manipulated to control the two frequency bands. The antenna exhibits excellent isolation between its ports, with scattering parameters (S12) and (S21) falling below −72/−46 dBi at the microwave and mm-wave frequencies, respectively, and not exceeding −35 dBi for the entire frequency band. The experimental results of the proposed antenna's prototype closely align with the simulated results, validating the design's effectiveness. Overall, this antenna design is well-suited for 5G applications, offering the advantages of dual-band operation, harmonic suppression, frequency band versatility, and high isolation between ports. [ABSTRACT FROM AUTHOR]

The application of microwave diamond-based HBAR as a sensor of microwave acoustic attenuation α was considered, using the Mo film as an object of research. A multilayered piezoelectric structure, as the Al/Al0.73Sc0.27N/Mo/(100) diamond/Mo, was produced using aluminum–scandium nitride composition, and was studied in detail for a number of the Mo films with different thicknesses obtained by magnetron deposition. The operational frequency band of 3.3 ... 18 GHz was used. It was found that the dependence of the resonant frequency shift vs. the h(Mo) thickness for all the overtones to be investigated was linear. For a given sensor, it was found that the mass sensitivity per unit area rm was equal to −26 × 10−12 and −8.7 × 10−12 g/(cm2∙Hz) at 6.0 GHz and 18.3 GHz, respectively. The frequency dependencies of quality factor Q, which changed as a result of Mo film deposition, were considered as the basic experimental data. A method for extracting the α(Mo) values was proposed. The Q-factor under the complete deposition of Mo film was 936 nm, and dropped moderately to ~25%. Such values were enough for an aim of the given experiment. The α(f) in molybdenum was obtained, and demonstrated a dependence that was close to quadratic, corresponding to the Akhiezer attenuation law. [ABSTRACT FROM AUTHOR]

This paper presents a new design for a dual-band double-cylinder dielectric resonator antenna (CDRA) capable of efficient operation in microwave and mm-wave frequencies for 5G applications. The novelty of this design lies in the antenna’s capability to suppress harmonics and higher-order modes, resulting in a significant improvement in antenna performance. Additionally, both resonators are made of dielectric materials with different relative permittivities. The design procedure involves the utilization of a larger cylinder-shaped dielectric resonator (D1), which is fed by a vertically mounted copper microstrip securely attached to its outer surface. An air gap is created at the bottom of (D1), and a smaller CDRA (D2) is inserted inside this gap, with its exit facilitated by a coupling aperture slot etched on the ground plane. Furthermore, a low-pass filter (LPF) is added to the feeding line of D1 to eliminate undesirable harmonics in the mm-wave band. The larger CDRA (D1) with a relative permittivity of 6 resonates at 2.4 GHz, achieving a realized gain of 6.7 dBi. On the other hand, the smaller CDRA (D2) with a relative permittivity of 12 resonates at a frequency of 28 GHz, reaching a realized gain of 15.2 dBi. The dimensions of each dielectric resonator can be independently manipulated to control the two frequency bands. The antenna exhibits excellent isolation between its ports, with scattering parameters (S12) and (S21) falling below −72/−46 dBi at the microwave and mm-wave frequencies, respectively, and not exceeding −35 dBi for the entire frequency band. The experimental results of the proposed antenna’s prototype closely align with the simulated results, validating the design’s effectiveness. Overall, this antenna design is well-suited for 5G applications, offering the advantages of dual-band operation, harmonic suppression, frequency band versatility, and high isolation between ports.

In this paper, single-layer ultra-Wide Band (UWB) microstrip patch antennas loaded with asymmetrical U-shaped slot in both microwave and millimeter wave applications are presented. These novel antennas cover a fractional bandwidth around 40% in both microwave and millimeter applications. The applications cover the C-band (4-8) GHz, V-band (40-75) GHz, and W-band (75-110) GHz. In addition to that, it is the sole article that cover the bands (5.15-5.825) GHz and (8.025-8.4) GHZ for WiMaX and ITU band applications, respectively. Moreover, it covers three bands for Automotive radar applications within (71-76) GHz, (81-86) GHz, and (92-95) GHz, in addition to further 5G/mm-wave applications at 60 GHz. Each antenna is coaxial fed and implemented on a Roger 5880 substrate with relative dielectric constant of 2.2, thickness of $1.575~mm$ and loss tangent of 0.0009. They operate over the frequency band (5.5-9.5) GHz for microwave band and (55-95) GHz for mm-wave band. To achieve either a notch in other bands or develop a multi-band structure, the conventional ground is replaced by two different structures. The first ground is an array of patches and the other is a mushroom ground. The first ground results in a notch within the band (73-79) GHz while the second one achieves a multi-band within (55-68) GHz and (81-95) GHz. Both antennas are simulated and verified using Finite Difference Time-Domain analysis (FDTD); CST Microwave Studio and Finite Element Method (FEM); Ansoft HFSS. For microwave band, the antenna is fabricated and measured for verification. Concerning the mm-wave version, three different types of ground planes are presented; traditional, periodic structure of patches and mushroom. The structure with periodic patches conducts the same band as the traditional ground plane does. This is a prestep for the design of the notches. The mushroom ground is carried out for multi-band applications. The average gain of the antennas is 7 dB.The measured two dimensional cuts of the radiation pattern, radiation efficiency, and reflection coefficient of the microwave version are presented and are in good agreement with the simulated results while for the mm-wave antenna the same parameters are simulated with two different methods and are in good agreement.

As one of the candidates of low-temperature cofired ceramics (LTCC), the sintering behavior, dielectric properties, and silver chemical compatibility of NaCaVO 4 were studied. The bulk ceramic samples were densified well at a low sintering temperature of 720 oC with an optimal bulk density of 2.87 g/cm3. Excellent microwave dielectric properties with a low relative permittivity ε r ~ 9.9, a high quality factor Q × f ~ 31,600 GHz, and a temperature coefficient of resonance frequency τ f ~ -66.5 ppm/°C were achieved at 11.5 GHz. The far infrared reflectivity spectra revealed the intrinsic dielectric properties (relative permittivity of 8.34 and dielectric loss of 2.7×10-4) are comparable to the measured values. The absence of chemical reaction between NaCaVO 4 and silver at firing temperature, evidenced by X-ray diffraction and energy dispersive spectroscopy indicated the potential prospect for LTCC application. Furthermore, the very low density of NaCaVO 4 opens up an avenue for its potential applications in light-weight devices. [ABSTRACT FROM AUTHOR]

Since it is designable, metasurface was widely used in various fields, especially the design of polarization converters. However, most of the polarization converters currently designed can only work under normal incidence or small angle incidence, which hugely limits the application of the device. In this paper, a chiral metasurface based on the z-shaped unit cell, which can manipulate circular polarization wave, is proposed. The simulation result shows that this converter can maintain the polarization state of circular polarization after reflection from 8.18 to 13.988 GHz with a polarization conversion ratio of more than 90%. Moreover, the structure is insensitive to the incidence angle, which can keep a stable performance both for left-handed circularly polarized wave and right-handed circularly polarized waves as the incident angle increase to 75°. The proposed metasurface with simple structure and angular stability can be used in communication and polarization manipulating devices.

In this paper, a nested square-shape dielectric resonator (NSDR) has been designed and investigated for antenna applications in the microwave band. A solid square dielectric resonator (SSDR) was modified systematically by introducing air-gap in the azimuth (Φ-direction). By retaining the square shape of the dielectric resonator (DR), the well-known analysis tools can be applied to evaluate the performance of the NSDR. To validate the performance of the proposed NSDR in antenna applications, theoretical, simulation, and experimental analysis of the subject has been performed. A simple microstrip-line feeding source printed on the top of Rogers RO4003 grounded substrate was utilized without any external matching network. Unlike solid square DR, the proposed NSDR considerably improves the impedance bandwidth. The proposed antenna has been prototyped and experimentally validated. The antenna operates in the range of 12.34 GHz to 21.7 GHz which corresponds to 56% percentage bandwidth with peak realized gain 6.5 dB. The antenna has stable radiation characteristics in the broadside direction. A close agreement between simulation and experimental results confirms the improved performance of NSDR in antenna applications. [ABSTRACT FROM AUTHOR]

This paper presents the improvement of radiation characteristics performances of the RFID array antenna for detection system of objects or living things in motion. The proposed array antenna is composed of two identical elements, connected in parallel via simple microstrip line divider, having a power port adapted to 50 Ω. This array is designed using RT/duroid-5880 substrate with the following parameters: loss tangent tan δ=9.10-4, ε r of 2.2 and substrate's height of 1.56 mm. The total size of this array antenna is (110.5 × 83)mm2. The simulation results obtained in this work show that the proposed array antenna has a high gain about of 9.22 dB, a good reflection coefficient S 11 of -25.36 dB, and a good adaptation at the 2.4 GHz microwave band. [ABSTRACT FROM AUTHOR]

Although many different kinds of polarisers have been extensively studied in the last 20 years, most previous designs were passive and single-functional designs. In this study, a kind of a new active polarisation converter is designed. The active polarisation converter is comprised of periodically arranged circular ring embedded with PIN diodes. Four different results of polarisation transformation and reflection can be presented by controlling the bias voltage of the PIN diodes. The full-wave simulation results show that the proposed metasurface can rigorously satisfy the asymmetric transmission and can achieve cross-polarisation conversion with high efficiencies for linearly polarised waves. In addition, there is another particularly obvious advantage of the proposed structure is its broad operation bandwidth in microwave band, the bandwidth of the polariser reaches 70%, more than 90% cross-polarisation conversion efficiency is observed from 6.5 to 13.5 GHz.

Based on the research achievements of the surface plasmon theory, a polarizer with sub-wavelength metal rectangular hole array structure is designed. Polarization filtering and polarization rotation effect are realized in microwave band. Polarization filtering effect and Marius law are verified by using polarizers of single-layer metal rectangular hole array, and the polarization rotations of 15°, 30°, 45°, 60°, 75° and 90° are realized by using polarizers of double-layer metal rectangular hole array. This experiment can not only make up for the lack of polarization experiment in science and engineering related courses, but also help students to understand the frontier of the discipline and help them to train and improve their comprehensive scientific ability and quality. [ABSTRACT FROM AUTHOR]

Although many different kinds of polarisers have been extensively studied in the last 20 years, most previous designs were passive and single-functional designs. In this study, a kind of a new active polarisation converter is designed. The active polarisation converter is comprised of periodically arranged circular ring embedded with PIN diodes. Four different results of polarisation transformation and reflection can be presented by controlling the bias voltage of the PIN diodes. The full-wave simulation results show that the proposed metasurface can rigorously satisfy the asymmetric transmission and can achieve cross-polarisation conversion with high efficiencies for linearly polarised waves. In addition, there is another particularly obvious advantage of the proposed structure is its broad operation bandwidth in microwave band, the bandwidth of the polariser reaches 70%, more than 90% cross-polarisation conversion efficiency is observed from 6.5 to 13.5 GHz. [ABSTRACT FROM AUTHOR]

RFID tag antennas with stable performance on the diverse electromagnetic mounting platforms are an integral part of the ubiquitous RFID systems. This research article presents a novel tag antenna design that facilitates the said objective. The proposed antenna consists of a modified H-shaped slot structure that ensures considerable robustness from the application environment through confining the surface current density within the antenna structure. The antenna offers a tunable bandwidth of 40 MHz within the microwave band of (2.4–2.5) GHz. The proposed tag antenna exhibits excellent response on metallic platforms of different sizes and thicknesses with an effective gain of almost four times of that in free space. Furthermore, the designed tag antenna performs adequately well on low–medium permittivity dielectrics (glass, paper, and plastic) and RF absorbers (water). The free space and on-metal performance of the proposed tag antenna are verified by testing a prototype realized on the FR4 substrate. [ABSTRACT FROM AUTHOR]

This paper presents the improvement of radiation characteristics performances of the RFID array antenna for detection system of objects or living things in motion. The proposed array antenna is composed of two identical elements, connected in parallel via simple microstrip line divider, having a power port adapted to 50 Ω. This array is designed using RT/duroid-5880 substrate with the following parameters: loss tangent tan δ=9.10-4, ε r of 2.2 and substrate's height of 1.56 mm. The total size of this array antenna is (110.5 × 83)mm2. The simulation results obtained in this work show that the proposed array antenna has a high gain about of 9.22 dB, a good reflection coefficient S 11 of -25.36 dB, and a good adaptation at the 2.4 GHz microwave band. [ABSTRACT FROM AUTHOR]

Characteristics of symmetric planar slot antennas of axial radiation, the size of which is comparable with the radiation wavelength ( = 30 mm) having a linearly extending opening was studied. The same directional diagram investigated antennas have been theoretically calculated, experimentally measured and analyzed for Aperture angle of 30, 60, 90 and 120. Experimentally measured directional diagram of the antennas (at frequencies of 10 GHz) are in good agreement with the developed mathematical models.

Abstract: Based on theoretical analysis, this paper studied experimentally the tunable low-pass, band-stop and band-pass filter effects of the MNG-DPS-MNG (μ-negative materials/double positive materials/μ-negative materials) magnetic plasmon polaritons waveguide. The research results show that the MNG-DPS-MNG waveguide without defect possesses the tunable low-pass filter characteristic. The waveguide with defect in the MNG region possesses the band-stop filter characteristic where the defect is equivalent to a sub wavelength cavity. And the waveguide with cavity in the DPS region possesses the band-pass filter characteristic. So the filter characteristics of the magnetic plasmon polaritons waveguide can be tuned by drawing into the resonators and changing the position and parameters of resonators. The experimental results are in good agreement with the simulation results. These properties will have potential application value in the tunable single channel or multi-channel filters. [Copyright &y& Elsevier]

model of the electrodynamic interaction of pyramidal horns in the Fresnel zone to take into account the curvature of the wavefront when measuring the gain is proposed. The results of experimental investigations to reduce the error in measuring the gain in the Fresnel zone are presented. [ABSTRACT FROM AUTHOR]

Remote sensing systems must be calibrated before use, so the accuracy of calibration source has a significant effect on the property of the whole remote sensing system. In this paper, calibration sources constructed of a periodic metallic pyramid array covered with absorbing material are studied for remote sensing systems working in the microwave band. The scattering properties of this kind of calibration source are first analyzed by the Floquet theory and the spatial harmonic method. Then, the finite-difference time-domain method is used to simulate the calibration source structure to obtain the scattered field and the corresponding differential scattering coefficient. By integrating the scattering coefficient, the emissivity is finally obtained. The relationships between the emissivity and the pyramid array structural parameters, and the electromagnetic parameters of the covering material are given. [ABSTRACT FROM PUBLISHER]

It is desirable that the method used for outdoor path loss estimation at microwave frequencies be one for which a worldwide consensus can be obtained through an ITU-R international standard. In this paper, a path loss prediction model for over-rooftop propagation environments is proposed for suburban areas. This model is based on the propagation mechanism explained by using the geometrical optics and consists of the direct wave region, the reflected wave region, and the diffracted wave region. The boundary points of these regions can be determined uniquely from the antenna height and building environment and all regions are continuously connected. Hence, high-precision estimation of the path loss can be estimated from the short-distance line-of-sight region to the far-field non-line-of-sight region. The proposed model is useful for channel design of microwave-band wireless access systems. Further, the method contributes to the ITU-R international standardization described above. Finally, it is shown that the measured path loss and the value estimated by the present model agree well at 2.2, 5.2, and 19.4 GHz. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(1): 13–24, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20333 [ABSTRACT FROM AUTHOR]

This paper discusses a λ/4-type wave absorber for the microwave band made with conductive paper, which is paper with a coating of conductive material. A simplified wave absorber of this type is first designed and constructed for the X band and Ku band. Using the resulting absorption characteristics, experimental formulas are derived for the relative permittivity and surface resistance. These formulas are then used to design and construct a more practical wave absorber, whose absorption characteristics are measured. Excellent absorption characteristics, better than 20 dB, are verified in the intervals from 8.2 to 10.6 GHz and from 14.1 to 17.2 GHz for wave absorption in the X band and Ku band, respectively, although there is a difference of approximately 0.4 dB between the designed matching frequency and the measured value. Design guidelines for such a microwave absorber using a conductive coating are then presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(10): 100–107, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1180 [ABSTRACT FROM AUTHOR]

New theoretical and experimental results of microwave acoustic wave propagation in diamond-based multilayer piezoelectric structures (MPS) as "Me1/(Al,Sc)N/Me2/(100) diamond/Me3" and "Me1/AlN/Me2/(100) diamond/Me3" under three metal film depositions, including the change in the quality factor Q as a result of Me3 impact, were obtained. Further development of our earlier studies was motivated by the necessity of creating a sensor model based on the above fifth layered MPS and its in-depth study using the finite element method (FEM). Experimental results on the change in operational checkpoint frequencies and quality factors under the effect of film deposition are in satisfactory accordance with FEM data. The relatively small decrease in the quality factor of diamond-based high overtone bulk acoustic resonator (HBAR) under the metal layer effect observed in a wide microwave band could be qualified as an important result. Changes in operational resonant frequencies vs. film thickness were found to have sufficient distinctions. This fact can be quite explained in terms of the difference between acoustic impedances of diamond and deposited metal films. [ABSTRACT FROM AUTHOR]

An experimental method is suggested that supposes the study of characteristics of slot bridge (SB) cells in the multimode operating regime. It is based on the preliminary numerical investigation of the resonant scattering characteristics of SB, i.e., the solution of the boundary value problem (BVP). The configuration of an experimental SB cell is computed according to the required frequency band and preliminary information about dielectric parameters of the materials chosen for tests. Etalon scattering characteristics of an SB cell are computed by software development on the basis of a rigorous solution of the BVP, providing numerical data with required accuracy. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 455–458, 1999. [ABSTRACT FROM AUTHOR]

The experimental method suggested suppose the studying of energy characteristics of slot bridge (SB) cells in the multi mode operating regime based on the preliminary numerical investigation of scattering resonant characteristics of SB (solution of boundary value problem and investigation of eigen frequencies and relevant field modes). The configuration of experimental model of SB cell is computed accordingly to required frequency band and preliminary information about dielectric parameters of materials chosen for tests. Ethanol scattering characteristics of SB cell are computed by software, developed on the base of rigorous solution of the boundary value problem, providing numerical data with any required accuracy. [ABSTRACT FROM AUTHOR]

In the microwave band, substrate integrated waveguide (SIW) couplers take the advantages of low profile, low insertion loss, low interference etc., but suffer from the big size. In this letter, a novel half mode substrate integrated waveguide (HMSIW) 3-dB coupler is proposed, which keeps the good performance of the SIW coupler with nearly a half reduction in size. Simulated results are in agreement with the measured data [ABSTRACT FROM PUBLISHER]

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%. [ABSTRACT FROM AUTHOR]

Local Multipoint Distribution Services (LMDS) system is a fixed cellular radio based point-to-multipoint technology in the microwave band providing broadband services. These systems need very accurate network planning method because of the variable carrier-to-interference ratio (C/I) in the whole service area and high sensitivity for meteorological phenomena especially for precipitation. The effects of a moving rain cell over an LMDS system was analyzed and site diversity as one possible countermeasure technique is demonstrated. The location dependent C/I in the LMDS service area under rainy conditions with and without site diversity technique was calculated applying a rain shower profile. [ABSTRACT FROM PUBLISHER]