dual-band operation

In order to further study the electromagnetic mechanism of the proposed antenna for dual-band operation, surface current distributions of the whole antenna at the frequencies of 2.5 GHz and 3.5 GHz are given in Figure 6. It can be clearly seen from the figure that the current distributions are different in the two bands. When the antenna operates at 2.5 GHz, most of the surface currents are concentrated along the square slot as shown in Figure 6(a). This indicates that the square slot acts as a resonator to generate the lower resonance mode. Figure 6(b) shows the simulated current distributions at 3.5 GHz. As expected, the strong resonant currents flow along the monopole to yield the upper resonance mode. Due to resonance characteristic of the monopole, this simple design can obtain a wide frequency band, covering the 3.5 GHz WiMAX applications.

Several methods have been considered in the literature for dual band operation of the antennas [3–13]. A new approach using the defect in the ground plane of microstrip antenna has been presented in this work. Here, a stacked microstrip patch antenna has been designed in such a way that one patch is placed above another with air-gap between them. The lower patch is fed by microstrip line along with a quarter wave transformer. This arrangement provides a fairly good broadband operation (≈ 20% Bandwidth). In the second stage, a variety of DGSs were realized with a mictrostrip transmission line and antenna as well to see their effect on the transmission and resonant properties, respectively. Later, a specific skew-F shaped DGS has been etched in the ground plane of the lower patch of the fabricated modified SMPA to produce a dual band operation.

The demand of antennas with multiple operation bands, wide bandwidth, high efficiency, compact size, and low cost has been increasing rapidly. Coplanar waveguide (CPW)-fed slot antennas have numerous advantages such as uniplanar structure, wide bandwidth, ease of fabrication, and integration with other circuitries, and recently has attracted much attention. Consequently, various attractive multi-band CPW-fed slot antennas have been proposed [1–9]. A dual-band radial slot antenna with bandwidths of 9.7% and 23.2% was presented [1]. An aperture-coupled slot antenna was designed to achieve tri-band operation with bandwidths of 6.7%, 6.0%, and 15.2% [2]. A dual-band slot-F-shaped-monopole hybrid antenna was proposed with bandwidths of 9.1% and 11.1% [3]. A quad-band slot antenna consisting of three L-shaped slots and one rectangular slot was presented for W-WiMAX/WLAN applications [4]. The first spurious mode of the slot dipole antenna has been utilized to achieve dual-band operation [5]. Four parasitic slots were employed to modify the radiation patterns at the first harmonic mode to resemble those of the fundamental mode. Its measured bandwidths are 17.4% and 8.8%, respectively. Later, a stepped-impedance slot dipole antenna with flexible frequency ratios was investigated for dual- band operation [6]. Its measured bandwidths are 12.5% and 8.0%, respectively, for the lower and upper bands.

Recently, the developments of 802.11b/g wireless protocols have pushed the evolution of multi-band antennas [9, 10]. In addition, dual band operation is a solid advantage for positioning technology, as testified in [11], where a dual band radio operating in 2.45 and 5.7 GHz is successfully employed in indoor scenarios to improve the Direction of Arrival estimation accuracy. Usually when applied to this class of positioning system a set of N antenna elements is typically arranged in a regular architecture, to form a Switched Beam Antenna (SBA), which is the key component for space division multiple access (SDMA) technology [7, 12]. Thanks to the regular arrangement, SDMA is easily implemented selectively enabling the signal reception from a specific antenna, thus isolating the signal coming from a specific angular region. At the same time the N beams must be large enough to cumulatively cover the entire 360 ◦ angle, permitting to operate without blind areas. This approach mitigates the uncertainty due to the multiple path reception [13], which is a perfect match for the cross-polarization rejection characteristics of CP antennas.

The U-shaped slot loaded rectangular patch has been treated in this paper, it is found that this structure can operate at two resonance frequencies and consequently this antenna can be used for dual band operation, also the effects of different physical parameters on the characteristics of this structure are investigated, also the variation of substrate permittivity is presented.

Abstract—In the present paper notch loaded shorted microstrip patch antenna has been analysed using cavity model. The proposed antenna shows dual band operation which depends on notch dimensions as well as shorting wall. The frequency ratio is found to be 1.5278 for the notch loaded rectangular patch, while in notch loaded shorted patch, the frequency ratio varies from 2.9764 to 2.725 for increasing value of notch width and it is almost invariant with notch depth. Further a slot loaded shorted patch antenna shows the dual frequency nature with the frequency ratio 1.7. The theoretical results are compared with IE3D simulation as well as reported experimental results.

10.7 mm, UCILA gap = 1 mm and the 25 mm length of the shunted open-circuited slotline (OCS). Figure 1(b) shows the structural dimensions in detail. The dual-band mechanism will be described in Section 2.3. Note that the ground plane edge and movable metallic plate edge can be considered as a short circuited resonant cavity. The distance between these two edges is defined as `. The antenna can be switched between single-low frequency operation and single-high frequency operation by adjusting the length `. Figure 2 shows the WLAN low-band operation for ` = 3 mm, the WLAN high-band operation for ` = 17 mm and WLAN dual-band operation for ` = 25 mm (open slotline).

Poisonous chemicals may spread over any city due to explosion in a nearby chemical company. Rotten meat due to disruptions in power lines will cause plague. Even water may be dispersed due to malfunctioning of distribution systems.Nuclear disasters more severe than Chernobyl are to come. All are due to security holes of industrial control systems that are the heart of industries mentioned above. Industrial Control Systems (ICS) like PLCs (Programmable Logic Controllers), SCADA (Supervisory Control and Data Acquisition) and DCS (Distributed control Systems) are the integral part of our industries. It is quite clear for control community that disruptions in normal operation of these systems can create disasters.This paper aims to illustrate different vulnerable aspects of ICS systems. An important fact that control engineers are not aware of is securing ICS (Industrial Control Systems), SCADA and etc. cannot be obtained by buying or adding “Secure Products” and tools. Actually, security cannot be implemented except by securing all devices and networks. In addition,since today’s security mechanisms and tools to secure Information Systems (IS) do not guarantee a time response, use of these mechanisms and tools are not wise and cannot secure ICS.

As a point in this direction we report the optimum values of the bandwidth of the optical for a system of high mode coupling optical fibers using DPSK modulation format for the input sig[r]

A single line feed stacked microstrip antenna with help of Photonic Band Gap (PBG) Slot Structure antenna for dual-band application is presented. The proposed antenna with two properly square patches is stacked. By creating a regular square slot on the ground plane, the top patch can perform as a driven element is design on 2.44 GHz and lower patch is also design on 2.44 GHz. The performance of proposed antenna dual band frequency (1.2 GHz and 2.44 GHz). The first frequency exists in GPS frequency band and second is 4G band 2400-2600 MHz Also gating radiation and antenna efficiency are very high compared to normal antenna.

Context-Aware Mobile TV service along the delivery chain allows the Mobile TV system to gather in a dynamic and realtime manner the different context information related to the users, de[r]

Dichroic or frequency selective surface (FSS) is an infinite periodical array of two dimensions. These surfaces comprise of periodically arranged metallic-patch elements or aperture elements within a metallic screen, which exhibit total reflection or transmission characteristics respectively in the neighbourhood of the element resonance. Actually FSS can be viewed as a spatial filter whose characteristics are immensely affected by the change of incident angle, polarization, and frequency. As spatial filter, FSS is widely used in the fields of microwave and optics [1-5]. This includes its use as sub-reflector, as in Voyager, Galileo, and Cassini space mission’s frequency reuse system. Frequency reuse of reflectors thus accomplished via the use of a dichroic surface, allows the sky radiation to be filtered at different frequencies, and therefore be processed by different receivers concurrently. FSS can be used as superstrates above the patch antennas to enhance the antenna directivity and FSS radomes help the RCS reduction. The use of frequency selective surfaces has also been successfully proved as a potential means to increase the communication capabilities for satellites. The growing demands on potential multi-functional antennas for radio communications also require complex FSS with multi-band requirements. In this paper, we have discussed the design of a thin-screen compact frequency-selective surface (FSS) that utilizes the printed circuit technology for multiband operation.

1) The variation of input impedance with frequency for different notch length for a given width is shown in Fig- ures 2(a) to 2(d). It is observed that notch microstrip an- tenna shows dual resonance in which lower and upper resonance frequencies increases with increasing notch length from 2mm to 5mm.

A dual-mode dual-band compact microstrip patch antenna with slotted patch which looks like an antenna with strip and spur line loading has been presented in this paper. Due to the strip loading, the resonant frequency has been lowered, and the resonant frequency can be reduced further by using added spur lines. But as with the addition of strips, the overall patch size is increased, and the slots are introduced on the patch such a way that it seems to behave as a patch, loaded with strips. The effects of strips loading has been utilized in the proposed antenna by introducing slots only. From the simulated and measured results, it has been found that the proposed antenna shows the dual-mode ( T M 10 and

dual resonance in which both lower and upper resonance frequency increases with increasing value of slot width and the bandwidth at upper resonance (10.25%) is higher than the bandwidth at the lower resonance (3.26%). The bandwidth of the antenna also increases with slot width whereas at lower resonance it is almost the constant. All theoretical results are found to be approximately in good agreement with the simulated results using MOM based IE3D [21].

In this article, a CPW-fed circular patch is used to attain wideband response. Dual-band operation with a lower band from 1.68–2.06 GHz for Global Systems for Mobile (GSM: 1.71–1.88 GHz) and upper band from 3.27–11 GHz for Ultra Wide Band (UWB: 3.1–10.6 GHz) is obtained by inserting a slot in the patch such that the perimeter of the slot is an integer multiple of quarter wavelength of the GSM 1800 band resonant frequency. A triple-band antenna with two lower resonant bands from 1.36–1.47 GHz for Wireless Medical Telemetry Service (WMTS: 1.395–1.4 GHz) and 1.9–2.25 GHz for Universal Mobile Telecommunication Systems (UMTS: 1.92–2.17 GHz) and 3.14–10.8 GHz for UWB is also developed by inserting a bent monopole in the space created by the slot in the circular patch. The lower bands are achieved without increasing the overall dimensions of the antenna which makes the design compact. The paper is organized as follows. The design details and parametric study of the dual-band antenna are presented in Section 2 while the triple-band antenna is presented in Section 3. Comparisons of simulated and measured results are presented in Section 4 followed by the conclusion in Section 5.

Abstract—The design and performance of a stacked patch antenna for wideband and dual-frequency operation are presented in this paper. The proposed antenna consists of a three dimensional (3D) circular transition-fed patch that is excited by a coaxial probe. By introducing a regular patch and a ring patch above the 3D circular transition-fed patch, good input impedance matching has been achieved over two frequency bands. The lower band possesses an impedance bandwidth (VSWR < 2) of 22.8% (0.775 to 0.975 GHz) and a peak gain of 5.2 dBi, while the upper band has an impedance bandwidth (VSWR < 2) of 65.8% (1.425 to 2.825 GHz) and a peak gain of 7.4 dBi. Other than the wideband and dual-band operation features, this antenna also has a beam tilted downward with a broadside beam pattern on the horizontal plane. Therefore, this antenna is very suitable for the indoor base station that is required to service several wireless communication systems, included CDMA800, GSM900, 3G, PCS, UMTS, BLUETOOTH and WLAN, by a single antenna.

Design of dual band components such as antennas, filters, and transformers is the research focus. As the key components, PDCs are widely used in microwave and millimeter-wave systems. In usual, the conventional power dividers are designed at a single band. Many researchers like Wu Lei et al (2006) and Dib Nihad, Khodie Majid (2007) have been made Wilkinson power dividers for dual-frequency application. Wu Y. et al (2009) discuss a design i.e. transmission lines in conventional WPD are replaced by the two impedance transformer and at the output parallel connection of a capacitor (C), a resistor (R), and an inductor (L) with parallel connection are shunted. Sakagami Iwata et al (2013) present a planar Dual-band 3-Way Wilkinson Power Dividers, 2 sections of transmission lines with two open circuited stubs are used for all 3 outputs. Maktoomi Mohammad A. and Hashmi Mohammad S. (2014) have present a dual band power divider using coupled line sections and stub. Park Myun- Joo & Lee Byungje (2008) have been proposed a new scheme in which dual band operation is achieved by attaching two central transmission line stubs to the conventional WPDC. Design of a novel dual-band unequal Wilkinson power divider with power division ratio of K has discussed by Li X. et al (2010).

Abstract—In this paper, a study on the dual-frequency box- shaped antenna is presented. With a 5-branch feeding strip and two plates of shorting strips, the antenna shows broadband and compact property. Then a U-shaped slot is etched for dual-band operation. Simulated and measured results all show that this antenna exhibits dual-wideband characteristic, covering several present wireless communication systems, such as GSM800/900 (824–960 MHz), WLAN11b (2.4–2.5 GHz), WiMax802.16 (2.5–2.7 GHz), and Bluetooth band (2.4–2.8 GHz). The simulated impedance bandwidth (2 : 1 VSWR) is 21.5% and 37.2% in the lower and higher band, ranging from 790 MHz–980 MHz and 2.3 GHz–3.35 GHz. Then details of the antenna are described and the prototype is fabricated and tested. A measured bandwidth of 19.8% and 38.9% in the two bands, ranging from 820 MHz–1000 MHz and 2.28 GHz–3.38 GHz, is observed, shown good agreement with simulated results. Moreover, the antenna has a coaxial feed with a compact size of 0.27λ × 0.22λ × 0.036λ (λ is the wavelength referenced to the lowest edge of the operating band 820 MHz).

A novel compact loop-loaded monopole with integrated band-select filter for dual-band operation is proposed. The additional physical resonator structure is employed to create the second frequency band. The miniaturization design of a monopole is achieved using a rectangle loop as a reactive loaded element. The reactive loading reduces the resonant frequency of the monopole antenna without affecting the radiation characteristics. The impedance between the antenna and the filter is optimized to improve the performance of the filter-antenna without restricting it to 50 Ω. The filter-antenna provides good selectivity and rejection in out of band regions and omni-directional radiation patterns in dual-band. The proposed design, in this case, integrates the filter-antenna and the AP’s system circuit board into a WLAN AP.