Ali I. Hammoodi

Cantor fractal-based printed slot antenna for dual-band wireless applications

Fractal geometries are attractive for antenna designers seeking antennas with compact size and multiband resonant behavior. This paper presents the design of a new microstrip fed printed slot antenna for use in dual-band wireless applications. The slot structure of the proposed antenna is in the form of Cantor square fractal geometry of the second iteration. The slot structure has been etched on the ground plane of a substrate with relative permittivity of 4.4 and 1.6 mm in thickness. A parametric study is conducted to explore the effects of some geometrical parameters on the antenna performance. Results show that the antenna possesses a dual band behavior with a wide range of resonant frequency ratio. In addition to the ease of fabrication and simple design procedure, the antenna offers desirable radiation characteristics. A prototype of the proposed antenna has been simulated, fabricated and measured. The measured 10 dB return loss bandwidths for the lower and the upper resonant bands are 42% (2.35

A Compact Dual Band Polyimide Based Antenna for Wearable and Flexible Telemedicine Devices

Recent wearable health monitoring systems use multiple biosensors embedded within a wireless device. In order to reliably transmit the desired vital signs in such systems, a new set of antenna design requirements arise. In this paper, we present a flexible, ultra-low profile, and compact dual band antenna. The proposed design is suitable for wearable and flexible telemedicine systems and wireless body area networks (WBANs). The antenna is inkjet printed on a 50.8µ mP olyimide Kapton substrate and fed by a Coplanar Waveguide (CPW). The proposed design has the merits of compactness, light weight, wide bandwidth, high efficiency, and mechanical stability. The performance of the antenna is also characterized against bending and rolling effects to assess its behaviour in a realistic setup since it is expected to be rolled on curved surfaces when operated. The antenna is shown to exhibit very low susceptibility to performance degradation when tested against bending effects. Good radiation characteristics, reduced fabrication complexity, cost effectiveness, and excellent physical properties suggest that the proposed design is a feasible candidate for the targeted application.

A tunable dual-band square slot antenna with stub for DCS, ISM, and WiMAX applications

This paper proposes a wearable dual-band square slot antenna with stub for ISM and WiMAX applications. The antenna has been built on a Vinyl substrate with a relative permittivity of 2.5 and a thickness angle of 0.47 mm. The square side length and the length of the stub are chosen to enable the antenna to provide a dual-band on 2.4 GHz and 3.5 GHz. The simulated and practical S-Parameters of the proposed structure show an excellent performance of the antenna with and without the bending. The radiation patterns have a good power distribution in both cases. The gain of the antenna is around 2.5 dB for both bands. This antenna is a good candidate for the application required a dual-band wearable antenna within the ISM and WiMAX bands. The High Frequency Structure Simulator (HFSS) has been used to provide the simulated results.This paper presents the design and parametric study of a tunable dual band square slot antenna with stub for DSC, ISM, and WiMAX applications. This dual band antenna has an ability to be tuned to any of the mentioned bands, according to the required applications, depending on the length of square side and the stub. The overall size of the designed antenna is 50mm × 50mm. The antenna has been etched to an epoxy FR4 substrate with a relative permittivity of 4.4 and a thickness of 1.6 mm. A parametric study has been presented for the stub. The design equation for the lower band and the design curve for the upper band are obtained. The resulted radiation patterns have been shown for different frequencies which give the antenna a good characteristic to be candidate as a dual-band antenna for the aforementioned applications. A commercial High Frequency Structure Simulator (HFSS), ver. 15, has been used to analyze the design parameters.

Isolation enhancment of two planar monopole antennas for MIMO wireless applications

This paper presents a planar slotted meander line structure to reduce the mutual coupling between two microstrip fed planar monopole patch antennas. The array provides a relative operating bandwidth of 98 % (1.37-4.00) GHz matched at a reflection coefficient S11 and S22 less than -10 dB with a total realized gain of 3.9, 4.66, and 4 dB at 1.85, 2.4, and 3.5 GHz respectively. The isolation level has been reduced to less than -20 dB for a wide frequency band of 85 % (1.46-3.64) GHz. The design represents a good candidate for modern wireless standards utilizing MIMO techniques including 3GPP LTE, WiMAX, WiFi, as well as systems utilizing ISM spectrum equipped with multiple antennas.

Mutual coupling reduction using grounded strip line with diamond slots

This paper presents a new proposed grounded strip line with diamond slots structure to reduce the mutual coupling between two closely spaced rectangular patch antennas for WLAN applications. The two patches are printed on a Roger RO3003 substrate with a relative permittivity of 3 and thickness of 1.52 mm. The decoupling structure is composed of diamond shape slots etched on a rectangular metallic strip placed between the two antennas on the top side of the substrate. The structure is grounded by a single via placed at the center. An isolation of 15 dB has been achieved with a separation of 0.19 λo at 5.8 GHz. The realized gain of the single element is around 6.2 dB. The array is suitable for WLAN application where compact size is required.

Isolation enhancement between two closely spaced circular patches using dgs

This paper presents a new Defected Ground Structure (DGS) to enhance the isolation between two closely spaced circular patches for wireless applications. The antennas are placed on a Roger substrate with a relative permittivity of 3 and thickness of 1.52 mm. Four arcs are slotted on the ground underneath the substrate to eliminated the mutual current interacting between the elements. An enhancement of 26 dB has been achieved with a separation of 0.05 λo at 4.8 GHz. The total realized gain at the resonance frequency after the isolation is 5.2 dB. The array is suitable for applications where compact circular patches array is suitable.

Studying the effect of bending on the performance of flexible dual band microstrip monopole antenna

This paper investigates the effects of bending on the performance of a flexible dual-band printed monopole antenna designed to work for GPS, WLAN, and WiMAX applications. The antenna is printed on a Polyimide substrate with a relative permittivity of 4.3 and thickness of 25 pm. The antenna is fed by a coplanar waveguide transmission line to enhance the impedance matching over the wide operating bandwidth. The dual bands are (1.53–1.67) GHz and (2.95–5.8) GHz. The simulated and measured values are in good agreement in term of Sn before and after bending. The radiation patterns show excellent performance of the antenna in the applications under consideration. The antenna achieves a maximum gain of 2 dB over the first band and 3.6 dB over the second band.

Effects of flexible substrates on the performance of UWB planar monopole antennas

The effects of thickness and dielectric constant of flexible substrates on the performance of a circular planar monopole antenna (PMA) is reported in this paper. The antenna is printed on a flexible Polyimide substrate and fed by 50 Ω microstrip line. Results revealed that substantial effect on the antenna performance due to substrate thickness and material even if the radiating structure is ungrounded. Hence, the substrate is an essential part of the antenna and not just a supporting structure as it is the case usually assumed in the literature. As substrate thickness decreases, the following changes were observed: reduction in impedance bandwidth especially for higher dielectric constants, and slight increase in the co-polarized gain. As the dielectric constant increases the following effects were identified: the impedance bandwidth increased on the high frequencies side while it is insignificant on the lower frequencies, as well as a decreased in the co-polarized gain.

A proposed flexible elliptical ring monopole antenna for DSC and UWB with notch suppression for 5.8GHz applications

Until recently, the UWB antenna has been used in many applications within different areas such in medical applications, multimedia connectivity, and personal communications, to mention a few, due to the design simplicity, low power, and high data rate transmission. The monopole antenna is a good candidate to be used in such applications due to the compact size, simplicity of fabrication, and cost effectiveness. Furthermore, the wearable devices technology requires a small size, high efficiency, and low profile antennas. An elliptical ring monopole antenna of 46 mm major axis and 23 mm minor axis printed on a Kapton substrate with a length of 66 mm, width of 36 mm, and a thickness of 50.8-µm is a good candidate to operate for the DSC (1.61 – 2) GHz and UWB (3.1 – 10.6) GHz bands. Two square slots of 2mm × 2mm have been removed from the two edge of the ground plane to enhance the impedance matching over the frequency range of (8–11) GHz. This antenna is fed by a tapered coplanar waved guide (CPW) transmission line of 12.8 mm length with a gap of 0.4mm to provide an enhanced impedance matching of 50 ohm over the aforementioned bands(H. Khaleel, H. Al-Rizzo, D. Rucker, S. Mohan, Antennas and Wireless Propagation Letters, IEEE, vol.11, no., pp.564–567, 2012). In addition, a modified rectangular slot line has been inserted to the monopole antenna to provide a notch at the frequency of 5.8 GHz to reject the signal comes from WLAN applications which operating at the given frequency. This slot line is able to be adjusted to any specified frequency that would be rejected. These types of antennas are very useful these days for the application that required a rejection of the unwanted frequencies especially for UWB applications. The antenna has been simulated using the High Frequency Structure Simulator (HFSS) ver. 15 and fabricated using an Inkjet printer. A parametric study has been carried out to obtain the final antenna dimensions which are mentioned on the attached figure. The simulated and practical S-Parameters are in a good agreement and shown in the figure below. The antenna has a good gain and radiation characteristic over the specified bandwidths. The proposed antenna is a good candidate for the applications required antennas operates on a DSC and UWB bands with a tunable band rejection.

Mutual coupling reduction between two closely spaced inverted-F antennas

Recent demands for miniaturized, lightweight, high data rate, and reliable wireless devices motivated researches and designers of wireless systems to adopt the use of multiple input-multiple output MIMO antenna arrays with close proximity of each other. One of the difficulties is to overcome the problems associated with the low isolation between any two closely spaced antennas. The low profile, small size, ease of fabrication, and simplicity of design encourage the use of the IFA/PIFA antennas. In this paper, two vertical IFA antennas with close separation of λ o /15 ( o /2) fed by coaxial lines are combined in an array operating at the frequency of 2.5 GHz. The two antennas are deployed on a ground backed substrate of 50 mm × 50 mm in length and width respectively and a thickness of 1.524 mm with a relative permittivity, e r of 10.2. Each IFA consists of a monopole as the main radiator with a length of 38 mm and a diameter of 1.22 mm placed 11 mm above the ground plane. The separation between the feeding point and the grounded end of the radiating element is 10 mm. The consequence of positioning the antenna in the proximity of each other is the high mutual coupling. To decrease the resulted effects, a new Defected Ground Structure (DGS) has been proposed. A rectangular slot of 32 mm and width of 1.5 mm with a strip line of 29 mm in length and a width of 1 mm have been introduced to the ground plane. The final proposed array with the DGS is shown in the attached figure. The Defected Ground Structure (DGS) has the effect of reducing the interaction between the antennas, main radiators, by restricting the current flow in the ground plane. A parametric study has been carried out to obtain the optimum dimensions of the structure using Ansys High Frequency Structure Simulator (HFSS). The S-Parameters of the design are shown in the enclosed figure. The antenna has an operating frequency of 2.5 GHz. A total isolation level of -22 dB has been achieved by the proposed structure at the operating frequency. The array with the proposed ground structure provides a gain of 3.9 dB at 2.5 GHz when the two ports are excited. This structure is a good candidate for reducing the mutual coupling between two vertical IFA for application utilizing MIMO techniques.