Design and Characterization of a Compact Single Layer Modified S-Shaped Tag Antenna for UHF-RFID Applications

In this paper, we report the design of a new compact single layer modified S-shaped tag antenna for UHF-RFID applications. To achieve a compact size of 51×34 mm2 for this tag antenna, the technique of using S shaped strip is applied, and by further adding a pair of equilateral triangular stubs into this structure, good impedance matching can be obtained at 915 MHz, which is the center frequency of the North-American UHF-RFID band (902 to 928 MHz). Besides exhibiting acceptable 5m read range in free space at 915 MHz, the proposed design shows a read range of about 4.5 when mounted on a metallic object (200 ×30 cm2) separated by spacer foam of thickness 1 cm. Furthermore, the proposed design shows a reasonable read ranges when it is mounted on different dielectrics with low permittivity. The proposed design has a simple configuration, low cost, acceptable read range, and can work on various background materials. &nbsp

A Compact Multi-Band Monopole Antenna using Metamaterial for WLAN/WiMAX Applications

In this paper, a tri-band printed monopole antenna with electrically coupled metamaterial units is proposed and investigated. The proposed antenna is designed to cover WLAN/WiMAX applications. The antenna consists of a printed strip line and two double metamaterial unit cells of different size placed near the monopole antenna on opposite sides. Each unit cell exhibits a negative permeability over the resonance frequency at 2.5 GHz and 3.62 GHz, which produces magnetic couplings with the monopole antenna. The proposed antenna structure was fabricated and measured. The measured -10 dB bandwidth for the return loss is from 2.47GHz-2.51GHz, 3.59GHz-3.69GHz, and 5.3GHz - 7.2 GHz, which are suitable for (WLAN: 2.4–2.484,  5.15–5.35,  and  5.725–5.85  GHz) and  (WiMAX: 2.5–2.69, 3.4–3.8, and 5.25–5.85 GHz) band Applications. By using the switches across the gap of proposed-MTM unit cell, the effect of this unit deactivated and its resonance frequency will disappear. Hence, the proposed antenna maintains the omnidirectional radiation pattern

Microstrip Antenna Design with Circular Patch for Skin Cancer Detection

Due to the many advantages of microstrip patch antennas, nowadays, microstrip patch antennas are mostly preferred in biomedical areas. This study aims two antenna structures, as both transceiver and receiver, have same dimensions are designed to produce solution of the difficulties in pathology. For antennas with an operating frequency of 2.45 GHz, FR-4 substrate material with a value of 4.4 dielectrics is used. A model has been prepared to detect the presence of skin cancer with the designed antennas. The model is a method of determining E-field and scattering parameters differences between two antennas of cancerous and normal tissue specimens placed on the glass slides. The same antennas and experimental setup were prepared with the normal and cancerous structure of the skin tissue prepared by pathologists. Thus, scattering parameters are measured and their differences are determined. It has been shown that cancerous tissue can be determined with different values obtained as a result. Ansys HFSS program is used for designs and simulations

An Accurate and Compact High Power Monocycle Pulse Transmitter for Microwave Ultra-Wideband Radar Sensors with an enhanced SRD model: Applications for Distance Measurement for lossy materials

In This paper, a high power sub-nanosecond pulse transmitter for Ultra-wideband radar sensor is presented. The backbone of the generator is considered as a step recovery diode and unique pulse injected into the circuit, which gives rise to an ultra-wide band Gaussian pulse. The transistor driver and transmission line pulse forming the whole network are investigated in detail.  The main purpose of this work is to transform a square waveform signal to a driving pulse with the timing and the amplitude parameters required by the SRD to form an output Gaussian pulse, and then into high monocycle pulses. In simulation aspect, an improved output response is required, in this way a new model of step recovery diode has been proposed as a sharpener circuit. This proposition was applied to increase the rise-time of the pulses. For a good range radar, a high amplitude pulse is indispensable, especially when it comes to penetrate thick lossy materiel.  In order to overcome this challenge, a simple technique and useful solution is introduced to increase the output amplitude of the transmitter. This technique consists to connect the outputs of two identical pulse generators in parallel respecting the restrictions required. The pulse transmitter circuit is completely fabricated using micro-strip structure technology characteristics. Waveforms of the generated monocycle pulses over 10V in amplitude with 3.5 % in overshoot have been obtained. Good agreement has been achieved between measurement and simulation results

Wideband Microstrip Dipole Antenna Design for WLAN/WiMAX Applications

Recently, microstrip antennas are preferred in all areas of wireless communication, due to their advantages such as low volume coverage, light weight, surface compatibility, high cost requirements and easy production etc. The main disadvantage of these antennas is their narrow band performance (~11%). In the literature, there are some wideband microstrip antenna designs. These broadband characteristics are obtained by changing the antenna geometry or by adding new parasitic patches to the antenna elements. In this study, a classical wideband microstrip dipole antenna (MDA) design which can be used in WLAN/WiMAX applications (covering the bands 2.4–2.5 GHz and 2.5–3.5 GHz) is introduced. The proposed antenna has a pair of twisted strip which are placed asymmetrically near the feed of the dipole element with a length of 52 mm (~λ/2). Also a pair of square loop elements is placed on a sublayer. The proposed MDA has a resonance between 2.06-3.72 GHz with a bandwidth of 57%. The antenna has a directive radiation pattern with a gain of 6.49-3.98 dBi

Base Station Antenna with Enhanced Cross Polarization Discrimination Performance by Using Horizontal Meandered Dipole and Vertical Parasitic Elements

This study is related with the design of a ± 45° dual polarized base station antenna with improved cross-polarization discrimination (XPD) values. Parasitic elements are added to antenna design formed by orthogonal two compact meandered dipole above ground plane. The antenna designed with CST Microwave Studio program has VSWR ≤ 2 within 1.71-2.69 GHz frequency band, which covers GSM 1800/3G/LTE bands. The antenna has minimum of 0 dBi gain in the beamwidth of 120° ( 60°) at azimuth plane (ϕ = 0°) along the band, and XPD values being minimum of 2 dB at 1.71-2.4 GHz for  60° without parasitic elements are improved to 10 dB with parasitic elements. This design initially had two horizontal straight monopoles on the ground plane perpendicular to each other. Afterwards, antenna with microstrip balun feed applied but the XPD values were not appropriate to expected results. Because of that, by using image theory, vertical parasitic elements were added to get appropriate XPD values. Later, meandered structure used to make antenna smaller. Finally, according to base station applications, antenna frequencies optimized to 1.71 GHz and 2.69 GHz. The designed and optimized antenna produced and measured in laboratory environment. Return losses for port 1 and port 2 are measured above the 10 dB and isolation between the port 1 and port 2 are measured above the 20 dB. In addition, the maximum gain values are measured between 3 dB and 7 dB in 1.71 GHz and 2.69 GHz frequency band.  Finally, XPD values are measured more than 10 dB in bandwidth

An Inverse Scattering Approach Based on Inhomogeneous Medium Green's Functions for Microwave Imaging of Brain Strokes

In this study, an inverse scattering approach is investigated for the detection and imaging of an abnormal structure (a bleeding or a stroke) inside the human brain. The method is mainly based on the solution of an integral equation whose kernel is the Green’s function of the inhomogeneous medium (corresponding to a human head model) which is obtained by a numerical approach based on Method of Moments (MoM). In this context, an inverse scattering problem related to the difference of healthy and unhealthy brain models is formulated and a difference function is obtained which indicates the region where the anomaly is located by solving this inverse problem. In order to reduce the reflection effects caused by the electromagnetic differences between the free space and the brain, a matching medium is used as the background space

Numerical Method for Electromagnetic Wave Propagation Problem in a Cylindrical Anisotropic Waveguide with Longitudinal Magnetization

The propagation of monochromatic electromagnetic waves in metal circular cylindrical dielectric waveguide with longitudinal magnetization filled with anisotropic inhomogeneous waveguide is considered. The physical problem is reduced to solving a transmission eigenvalue problem for a system of ordinary differential equations. Spectral parameters of the problem are propagation constants of the waveguide. Numerical results are obtained using a modification of the projecting methods. The comparison with known exact solutions (for particular values of parameters) are made

Artificial Chiral Media Using Conical-Coil Wire Inclusions

The electromagnetic response of the electrically small conical wire coil as a chiral inclusion is described. An existing model of the helical coil wire inclusion is extended to model the conical coil wire inclusion, using the Method of Moments (MoM) to determine the dominant resonant circuit impedance of the inclusion. Material parameters are determined using mixing relations with polarizability coefficients expressed for the conical coil inclusion geometry. The polarization conversion of a dielectric slab loaded with conical coil inclusions is predicted and compared to simulated results using a forward scattering technique

Improved Efficiency of Inductive Power Transfer in Misalignment Conditions with Multi Coil Design

In charging process of electric vehicle, a misalignment between the transmitter (Tx) and receiver (Rx) coupling  structure decreases the efficiency of the wireless power transfer. In inductive power transfer system, misalignment reduces the effective coupling between the Tx and Rx coils. In this work, based on previous multiple coil structures, a new multi coil design in proposed to increase the efficiency of the power transfer. Here, a multi coil structure with two rectangular and four spiral coils is designed with the overall dimension of the coil structure 26.5 cm x 36.5 cm. The measurement shows, that for coil distance below 10.3 cm and a lateral misalignment of maximal 10 cm (27.4%), the efficiency of the designed multi coil structure is better compared to previous coil structures. However for larger coil distance or larger misalignment, the efficiency of the new coil structure deteriorates significantly