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ABSTRACT This article investigates the slotted bow-tie dual-polarization antenna with achieving the wide band. The proposed antenna consists of upper antenna and lower antenna in one PCB substrate. This antenna achieves a −10 dB return loss within the operating band of 1.6-2.3 GHz, which has a 700 MHz bandwidth. Isolation between antenna 1 and antenna 2 is about −30 dB within the operating frequency band. Antenna 1 and 2's gains are above 8 dBi in the entire frequency bandwidth. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:22-26, 2015 [ABSTRACT FROM AUTHOR]

New analytical formulas have been developed for evaluating the asymptotic impedance matrix of an asymmetric gap by using the integral transform method. Application of the newly derived formulas shows a dramatic improvement of the computation time for evaluating the overall impedance-matrix elements for the symmetric and asymmetric gaps while retaining the accuracy. Index Terms--Discontinuities, integral equation, spectral-domain method.

Modern personal communication handsets are shrinking in size and are required to operate at multiple frequency bands for enhanced functionality and performance. This poses an important challenge for antenna designers to build multiband antennas within the limited allowable space. In this paper, an internal antenna covering seven frequency bands is presented for personal communication handsets. The proposed antenna operates at GSM (880-960 MHz), DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), Bluetooth (2.4-2.48 GHz), and WLAN (5.0-5.5 GHz) frequency bands. Measured input return loss of the antenna is better than -10 dB at all the frequency bands with reasonable radiation performance. Antenna volume is 30 mm x 15 mm x 4.0 mm (1.8 cm3) that makes it attractive for modern multiband and multifunctional slim handsets. [ABSTRACT FROM AUTHOR]

Presents a study which discussed an integral transform technique for evaluating the scalar and vector potentials of a singular wire antenna. Equations on the integral transform technique of a singular kernel; Evaluation on an infinite integral transform; Computations and comparisons.

In this paper, a high efficiency broadband planar array antenna is developed at X-band for synthetic aperture radar (SAR) on small satellites. The antenna is based on a multi-layer element structure consisting of two dielectric substrates made of Taconic TLY-5 and three copper layers (i.e., the parasitic patch (top layer), the active patch (middle layer), and the ground plane (bottom layer)). The parasitic patch resides on the bottom surface of the upper TLY-5 substrate while the active patch is printed on the top surface of the lower substrate. A Rohacell foam material is sandwiched between the top layer and the middle layer to separate the two dielectric substrates in order to achieve high directivity, wideband, and to keep the antenna weight to a minimum as required by the SAR satellite application. To satisfy the required size of the antenna panel for the small SAR satellite, an asymmetric corporate feeding network (CFN) is designed to feed a 12 × 16 planar array antenna. However, it was determined that the first corporate feed junction at the center of the CFN, where higher amplitudes of the input signal are located, contributes significantly to the leaky wave emission, which degrades the radiation efficiency and increases the sidelobe level. Thus, a suspended microstrip slab, which is simply a wide and long microstrip line, is designed and positioned on the top layer directly above that feed junction to prevent the leaky waves from radiating. The experimental results of the antenna show good agreement with the simulated ones, achieving an impedance bandwidth of 12.4% from 9.01 to 10.20 GHz and a high gain above 28 dBi. The antenna efficiency estimated from the gain and directivity eclipses 51.34%. [ABSTRACT FROM AUTHOR]

This paper proposes the design of a small chip-type dielectric antenna using the advanced meander line technique, so that the radiation metals are formed on the bottom face of a ceramic dielectric (8 × 4 × 1.5 mm3, alumina) and on both faces of the substrate (thickness 1.0 mm, FR-4). The performance of the proposed antenna mode, which remarkably reduced the size, shows good agreement between measured and computed results. The measured results show that this antenna has 11.2% bandwidth (2.35–2.63 GHz, |S11| < -10 dB) and 2.3-dBi maximum radiation gain, respectively. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 366–368, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11218 [ABSTRACT FROM AUTHOR]

The development of radar technology for the detection of small drones is getting attention of researchers. In this work, the detection of drones using Ku-band radar system has been discussed. We have utilized the advantage of nonlinear frequency modulation (NLFM) waveform for the suppression of range sidelobes. The performance and sensitivity of a radar system can be related with the linearity of system response. Here, we have made an effort to minimize non-linearity in the radar system response by using digital predistortion method. In this method, amplitude weighting coefficients have been calculated based on the received data. We have used FPGA-based transceiver for intermediate frequency (IF) signal generation and data acquisition, along with Ku-band up-down converters. The radar system was first calibrated for desired frequency band using amplitude predistortion method. In this article, experiment results for the detection of single drone and two drones using NLFM pulse signal are presented. [ABSTRACT FROM AUTHOR]

Depolarized fields inside a magnetodielectric sample interfere with the accurate measurement of sample characteristics in a cavity perturbation method. These depolarized fields occur due to the polarization of the test sample, depending on the volume and shape of the sample, in the electromagnetic field. To characterize the magnetodielectric sample more accurately, we proposed an advanced rectangular cavity (RC) perturbation method. In this method, we investigated the change in the resonant frequency and $Q$ -factor of a cavity which depends on the volume, and shape of the sample, and depolarized fields within the sample. The depolarizing factor for calculating the permittivity and permeability of the sample is derived by separating the uniform and depolarized fields within the sample when the sample is inserted in the cavity. These separations of fields play an important role to improve the measurement accuracy. The proposed unified RC perturbation technique is validated initially by measuring the resonant frequency and quality factor and then calculating the complex permittivity and permeability at the TE $_{10l}$ mode. The standard dielectric material (Al2O3) and magnetic material (YIG) samples are measured with the vector network analyzer. The measurement was performed when the magnetodielectric sample having various shapes and volumes inserted into the RC resonator. In comparison with the previous cavity perturbation methods, the permittivity and permeability have been calculated more accurately with various shapes of the test sample, and we also found that the ratio of the maximum sample volume to the cavity for various samples increases about 40%. Based on the proposed method, for a cube-shaped sample, we obtained the complex permittivity and permeability consecutively at each resonance mode without any physical relocation of the test sample. Therefore, the test sample is capable of continuous more accurate and more effective measurement in the desired frequency band without relocation using the proposed technique. [ABSTRACT FROM AUTHOR]

Liquid crystal (LC)‐based radio‐frequency (RF) tunable antennas garner attention because of their compact size and minimal heat generation. Exploiting the LC's property to alter the RF permittivity depending on its alignment, voltage‐induced orientational switching enables frequency modulation of the radiated wave. To ensure dependable antenna performance, precise control of the initial LC alignment is crucial, which is conventionally achieved by polyimide (PI) coating followed by the rubbing process (PI‐rubbing). However, this approach demands high temperature (200 °C) and prolonged processing time (2 h), while also necessitating high voltage for LC reorientation due to induced excessive surface polar anchoring strength. Here, a PI‐free‐nanoscratching method creating 1D channels is introduced that induces initial LC alignment in a desired direction. The initial orienting capability of the scratched metal surface is superior to that of the PI‐rubbed surface. Furthermore, the LC‐based antenna employing the nanoscratching method shows a remarkable resonance frequency shift of up to 3 GHz with a low voltage of 2 V. This driving voltage is five times lower than that of antennas using the conventional PI‐rubbing method, which can open a new era for the next generation LC‐antenna. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical model of the rectangular-shaped microstrip patch antennas on liquid crystal (LC) substrates in order to accurately derive the resonant frequencies and radiation performances. The model is based on the solution of the mode matching about an LC loaded cavity. The calculation results of the theoretical model are compared with the experiment and simulation results. The discrepancy between calculation and simulation results is merely 2.7%. In addition, a tuning mechanism of the patch antenna on the LC substrate is verified depending on the strength of a biasing voltage. The calculated results of the theoretical model indicate that the resonant frequency is shifted toward lower direction and 3-dB beamwidth of radiation pattern increases as the bias voltage increases. Although the calculated maximum directivity decreases with the increment of voltage, the realized gain increases due to the radiation efficiency of the antenna. [ABSTRACT FROM AUTHOR]

This paper proposes an accurate method to calculate the permittivity and permeability of ferrites simultaneously at the demagnetized state. The eigenvalue equations for the resonator model can be obtained by applying the boundary condition of the structure of the resonator at both demagnetized and magnetized states. The complex permeability and permittivity are computed from the measured resonant frequencies and unloaded quality factors of the resonator using the mode splitting phenomenon. To verify the calculated magnetization values, the magneto-static simulation is performed by using CST EM studio based on the measured data of B-H curve. The measured complex permeability and permittivity of the demagnetized ferrite are verified by comparing with cavity perturbation method and statistic equation. [ABSTRACT FROM AUTHOR]

Abstract: In this article, a low‐profile full‐metal‐rimmed antenna with less nonground portion for smartphones is presented. The proposed antenna with full‐metal rim is designed on FR4 substrate within the volume of 115 × 60 × 5 mm3. Metal rim is made up of FR4 substrate with interconnected conducting vias which surrounds inner system circuit board. The gap between metal rim and system ground plane is 1.5 mm and they are connected by a single ground patch. Moreover, folded monopole branches are implemented on circuit board to obtain wide bandwidth and improve impedance matching at higher bands. Therefore, proposed antenna contains a system circuit board with monopole branches and a full metal rim which serves GSM (850), DCS (1800), PCS (1900), UMTS (2100), LTE (2300/2500), WiBro (2350), ISM (2400), SDM‐B (2650), and W‐LAN system operating bands. The proposed antenna also has an attractive feature of utilizing very less portion of ground clearance about 4 × 38 mm2 for placing monopole antenna and still covering a wide range of operating bands. This biggest merit makes it a potential candidate for metal rimmed smartphone applications with lesser nonground portion. A sample proposed structure has been realized on FR4 substrate to prove the design concept. [ABSTRACT FROM AUTHOR]

This paper presents an efficient method to measure the permittivity, permeability, and magnetization of ferrite at various resonance frequencies of ferrite resonator. A cylindrical dielectric rod is inserted to annular ring ferrite for tuning the resonance frequency of the ferrite resonator without changing the length of the resonator. The permeability and permittivity of ferrite are calculated using a characteristic equation for resonator in a demagnetized state. The permittivity is compared with the measured results by the cavity perturbation method to verify the calculated results. We analyzed the electromagnetic fields in each region of ferrite, and derived $8 \times 8$ eigenvalue matrix for the mode-splitting behavior on the HE+111/HE−111 mode. The induced magnetization of ferrite in the partially magnetized state is calculated by a nonlinear system with the measured resonance frequency. The calculated magnetization of the resonator is a critical parameter to analyze ferrite material, so the calculated results are verified by the magneto-static simulation based on the measured data of $B$ – $H$ curve. Finally, the permeability tensor components at various frequencies are obtained by statistic equations. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical model of a cylindrical hybrid resonator antenna. The hybrid resonator consists of an annular ring ferrite and a cylindrical dielectric with a dc magnetic bias field, applied in direction parallel to the antenna height. The HE11\delta mode splitting behavior caused by tensor nature of the permeability of a biased ferrite is investigated. To validate the proposed approximate analysis, an experimental investigation of an antenna loaded with a biased ferrite is also presented. The presented theory is shown to demonstrate the measured results. The antenna is found to be used as frequency, bandwidth, and polarization tunable antenna. The operating frequency can be chosen in the range from 9.07 to 9.84 GHz. In addition, the bandwidth can be extended from 7.3% to 12.7%. The polarization can be switched from linear to circular. The features mentioned earlier can be achieved by applying the appropriate magnetic field due to the \mathbf HE\mathbf {11\delta } mode splitting behavior. The theoretical model, the design process, and the measured results are presented in detail. The antenna is also found to be capable of tuning the operating frequency as well as the frequency tuning range without changing the overall size of the resonator. [ABSTRACT FROM AUTHOR]

ABSTRACT: This paper presents an FMCW K-band rain radar with the property of high resolution. The radar system was designed for measurement of localized torrential rain. Using DDS and FPGA control, heterodyne modulation was used to generate the FMCW down-chirp signal with 50 MHz bandwidth, and emitted a K-band signal with nominal power of 125 mW in the vertical direction. To obtain high resolution for the Doppler spectrum, the radar system used a coherent signal processing method. Several experiments were conducted and the results were compared with data from the meteorological administration. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:817-822, 2016 [ABSTRACT FROM AUTHOR]

A low side-lobe substrate-integrated-waveguide (SIW) antenna array is presented at the 28-GHz band using broadband unequal feeding network for millimeter-wave (mm-wave) handset devices. The ground-plane size of the proposed antenna is fixed to half of the size of the Samsung Galaxy Note 4. The antenna array has been implemented with a multilayer structure created by stacking three substrates and a copper plate. An 8-way SIW feeding network with broadband 4-stage T-junction dividers and a cavity-backed antenna are investigated to obtain broadband performance. The proposed unequal T-junction dividers with phase compensation are introduced and designed for various output ratios. Applying Taylor beam-pattern synthesis in the 8-way SIW feeding network, low side-lobe performance is achieved. The measured result of the fabricated antenna has 2.3 GHz bandwidth within \textS_11\,<\, - 10\ \textdB. The fabricated antenna can be performed with a gain up to 13.97 dBi with a low cross-polarization and symmetrical fan beam radiation patterns with low side-lobe levels. Most of the measured results are validated with the simulated results. The proposed antenna array provides low cost, broadband performance, and good radiation performances with low side-lobe levels for mm-wave handset devices. [ABSTRACT FROM PUBLISHER]

Electromagnetic (EM) lens antenna designs using cascaded metasurfaces for gain enhancement and beam steering applications are proposed. Two different lens aperture designs are proposed and populated with aperiodic unit cells of size 0.2λo × 0.2λo. In lens Design 1, the unit cells of different phases are distributed in concentric circular zones, whereas in lens Design 2, the unit cells of different phases are distributed in vertical linear zones on the aperture of the EM lens. Both lenses are composed of two cascaded metasurfaces with an air gap of 0.047λo (where λo = 51.7 mm at 5.8 GHz). For gain enhancement, the metasurfaces are positioned at an optimum focal distance, f = 0.61λo above source patch antenna (f/D = 0.3). Beam steering is accomplished by phase transformation of the source antenna, which can be realized by mechanically sliding the passive metasurfaces in one direction (i.e., ±x‐direction) above the source antenna. The prototype of the two proposed lenses are fabricated and tested. The measured peak boresight gain obtained from Design 1 and 2 are 14.98 and 15.12 dBi, respectively. The experimental results show −25° to +25° and −27° to +27° beam steering range for Design 1 and 2, respectively, with a little gain degradation at other angles. [ABSTRACT FROM AUTHOR]

In the field of synthetic aperture radar (SAR), a lot of researchers have tried to study an improved application beyond the conventional two-dimensional image. Video-SAR (ViSAR) is one of the hot issue in the SAR application. The main purpose of ViSAR is to monitor various targets in the area of interest in time order. It can offer video images to detect not only the fixed target but also the moving target. For the signal processing of ViSAR, this article introduces the improved performance by the Doppler shifting technique with fractional Fourier transform. And also, it shows that the proposed method can separate the unexpected signal of the moving target within each frame of single-channel ViSAR. Furthermore, the overall algorithm can increase efficiency and reliability in ViSAR processing. To verify the improvement of our method, we carry out the practical experiments by an X-band chirp pulse SAR system, mounted on an airplane. [ABSTRACT FROM AUTHOR]