Planar Monopole Antenna

A small-size microstrip-fed multi-band planar monopole antenna is presented. The base of the proposed antenna is a diamond-shaped patch (DSP) that covers the ultrawideband (UWB) frequency range. The range of UWB is 3.1- 10.6GHz. Using narrow strips in DSP antenna, acting as resonance paths, can be integrated with the multiband antenna. It is shown that by removing the centre part of the DSP antenna, without distorting the UWB behavior, quarter-wavelength strips can be added to the notched region. This will not affect the dimension of the base antenna. The designed multiband antenna has a substrate size of 16×22×1 mm 2. and covers the frequency bands 3.1– 10.6 GHz. The antennas have omnidirectional and stable radiation patterns across all the relevant bands.

This article proposes the design of a compact beveled rectangular planar monopole antenna for Ultra wideband (UWB) applications. The radiating element is printed on a low- cost FR-4 epoxy substrate with relative permittivity of 4.4 and thickness of 1.6mm. It has overall dimensions of 18×15×1.6 mm3. A 50-ohm coplanar waveguide (CPW) transmission line is used to excite the proposed antenna. The simulated impedance bandwidth of the proposed antenna for -10dB reflection coefficient is from 2.9GHz to more than 12GHz. Radiation efficiency better than 90% and group delay variation less than 1ns are obtained throughout the UWB. Furthermore, a stable omnidirectional radiation and a peak gain of 3.91dB are observed. A prototype of the proposed antenna is fabricated. The measured reflection coefficient of the proposed antenna covers a wide impedance bandwidth from 2GHz to over 12GHz with S11 better than -10dB.

Recently, ultra wideband communication systems have been developed widely and rapidly, which lead to a great demand in designing wideband microwave components, such as antennas, filters and so on [1–9]. Several antenna configurations including planar monopoles and dipoles have been studied for ultra broadband applications [10– 15]. Also, UWB transmitters should not cause any electromagnetic (EM) interference on nearby communication systems such as WiMAX and WLAN systems. The use of the 3.4–3.69 GHz band is limited by WiMAX. Therefore, a band-rejection filter is necessary in UWB RF front-ends, and this will provide complications for UWB systems.

In this paper, a printed fork-shaped monopole antenna for UWB applications [3] is modified with tri-band notched characteristics. The tri-band notched characteristic is obtained by defected ground structure (DGS) U-shaped and two extended U-shaped slots [2] for WIMAX and X-band satellite communication systems, respectively. However, in order to realize the notched band in the WLAN band, a semi arc-shaped slot is etched in the radiating element. The rejected bands can be controlled by adjusting the length of slots and the radius of semi arc-shaped slot. The performances of the proposed antenna are studied, and the simulated and measured results are presented.

monopole antenna [10], a microstrip-fed double-T monopole antenna [11]. A CPW-fed notched monopole antenna [12], a CPW-fed meander monopole antenna [13, 14], a novel planar monopole antenna antenna with an H-shaped ground plane [15], a microstrip fed monopole patch antenna with three stubs [16]. From these studies, however, it can be observed that none of above-mentioned designs support the worldwide interoperability for microwave access (WiMAX) applications and achieve a multi-band response to cover the 2.5/3.5/5.5 GHz (2500– 2690/3400–3690/5250–5850 MHz) WiMAX bands [17]. In this article, we propose a new CPW-fed monopole antenna for the purpose of WLAN/WiMAX operation. The antenna is originally designed as a T-shaped CPW-fed monopole with a trapeziform ground plane and two parasitic elements to generate the resonant responses. This way, the antenna can achieve a tri-band performance to simultaneously cover the most commonly used WLAN and WiMAX bands. The 10-dB bandwidth of simulated return losses reaches 2.35–2.71 GHz, 3.35–3.72 GHz and 4.9–6.1 GHz in the three bands, respectively, and can cover the 2.4–2.484 GHz, 5.15–5.35 GHz, and 5.725–5.825 GHz WLAN bands, and the 2.5–2.69 GHz, 3.4–3.69 GHz, and 5.25–5.85 GHz WiMAX bands.

In recent years, many engineers focus their interests on how to design multiband antennas that can be integrated in a portable wireless communication device for several communication standards, especially for the WLAN (2.4–2.48, 5.15–5.35, and 5.72–5.85 GHz) and the WiMAX (2.5–2.69, 3.40–3.69, and 5.25–5.85 GHz) in wireless communication. Thus, different types of multiband antennas have been proposed to cater various user requirements, such as [1–12]. For example, a dual-band coplanar patch antenna integrated with an electromagnetic bandgap substrate is reported in [1], a dual-wideband printed T-shaped monopole antenna is proposed for WLAN and WiMAX applications [2], a compact ring monopole antenna with double meander lines is proposed for WLAN applications [3], a couple dual-U-shaped antenna is presented for WiMAX triband operation [4]. However, there are only two bands involved in [1–3], and only triple WiMAX band is reported in [4], which limited the number of working bands in portable devices. A compact triband planar monopole antenna suitable for WLAN and WiMAX is presented [5], the antenna consists of a L-shaped microstrip feedline and open-ended slot on the ground plane is proposed for WLAN/WiMAX applications [6], miniature triband CPW- fed monopole antenna embedded with dual U-shaped slot is reported in [7], the antenna with simply shaped radiator element for multi-operating bands of the wireless communication systems is studied in [8]. Furthermore, some compact antennas for WLAN/WiMAX applications have been presented in [9–12]. However, the antennas mentioned above have either complex structure or large size, which are not suitable for the portable wireless terminals with limited space. A coplanar-waveguide (CPW)- fed single-band antenna, loaded with a reactive termination has been proposed to reduce the size of an antenna [13], but it still has a large size.

Abstract—The proposed antenna structure is excited for multiple operational modes by means of meandered strips. The compact planar monopole antenna is demanded enormously for handheld devices especially automatic meter reading and tablet devices. Due to Chu limit, it is extremely vital to miniaturize an antenna by balancing tradeoff between bandwidth and radiation efficiency. The designed antenna is formed by two interconnected broad monopole open slots which covers multi-bands for smart energy meter and tablet computer applications. The cost effective FR4 laminate of size 50 × 200 mm 2 (0.4 λ × 1 . 6 λ ) is employed to match standard tablet computer communication module dimensions. The impedance bandwidth, for all excited resonant modes, is above typical requirement of 2%, and the VSWR is well below the necessary requirement of 1.5. The peak gain ranges from 0.94 dBi to 1.92 dBi. Radiation patterns along with other antenna parameters are satisfactorily meeting the demand of Wireless Energy Meter and Tablet Devices. The effects of varying dimensions of a monopole on the radiation characteristics have also been presented. The return loss and radiation patterns computed through simulations are validated through experimental measurements in an anechoic chamber environment.

In 2002, Federal communication commission approved the unlicensed ultra-wideband (UWB) that ranges from 3.1 to 10.6 GHz [1]. In the past, conventional configurations such as log periodic, bi- conical and spiral broadband antennas were used extensively for wideband communication systems, but they were not always suitable for compact handheld mobile devices. So, the design of innovative ultra-wideband antennas is demanded to satisfy different specific requirements including size, gain and radiation patterns. Many low cost non-planar metal antennas are reported for ultra-wideband application [2, 3]. In the last few years, some innovative antennas such as printed planar monopole antenna, planar inverted cone antenna (PICA), Vivaldi and volcano antenna have been developed and analyzed for wireless communication related applications to provide ultra-wide bandwidth and omnidirectional radiation pattern [4–11]. The reported planar metal antenna is a modified design of non-planar metal antenna [12, 13].

Wideband communication systems are rapidly growing and attract a lot of attention due to the wide applications such as radar and short-range communication systems. However, due to their broadband operation, wideband antenna has the potential to be interfered by the existing wireless communication systems such as WIMAX, WLAN and C-band satellite communication systems. Several solutions have been attempted to overcome the interference problem, mainly by introducing band notch or band stop function to the wideband antenna design. In [1], a ultra-wideband antenna (UWB) with single band notch function using electromagnetic bandgap (EBG) structure is presented. A wideband planar monopole antenna with dual band notched characteristics is discussed in [2]. Dual band and triple band notched characteristics have also been discussed in [3–5]. However, the techniques used in [1–5] are applicable to only fixed single or dual frequency band. Recently, new techniques using reconfigurable notched function have been investigated. In [6], a reconfigurable slot antenna with band notch function is presented. A dual band notched UWB with triple band WLAN reconfigurable antenna has been discussed in [7]. Meanwhile, [8] proposes a UWB circular slot antenna with reconfigurable notch band function. In [9], a miniature UWB antenna with dual tunable band notched characteristics has been presented. Reconfigurable band notched antenna has also been discussed in [10–12]. However, none of the reported techniques use reconfigurable EBG to achieve reconfigurable notch function and capable of reconfiguring more than two band notches.

Abstract—A microstrip-fed planar monopole antenna consisting of an inverted-L monopole and a square parasitic element extending directly from ground plane to obtain wideband operation covering Bluetooth/ISM, 2.5 GHz WiMAX, 3.5 GHz WiMAX and 5.2/5.8 GHz WLAN bands is presented. The proposed antenna employs a shorted parasitic element to improve the bandwidth. The return loss of the suggested antenna geometry was calculated by a commercial HFSS 9 simulator and the results are compared with measured return loss, which shows a good agreement between them. Details of the proposed antenna designs and experimental results of the constructed prototypes are presented.

Figure 1 depicts the geometry and configuration of the simple and proposed planar monopole antenna. The simple planar monopole antenna contains two metallic rectangular radiating plates of dimensions 14 × 16 mm 2 and 12 × 5 mm 2 placed orthogonally on the coplanar system ground plane of dimensions 20 × 40 mm 2 and is excited using an edge port. The proposed antenna has a bevel-slot transition feed and radiating patch of dimensions 12 × 16 × 5 mm 3 mounted on a coplanar system ground plane. The compact antenna structure makes the antenna a suitable candidate for practical wireless UWB-USB dongle applications. Foremost, the modal analysis of corresponding simple planar monopole antenna is carried out by means of Theory of Characteristic Modes to get the physical insights in the different radiating modes of the arbitrary shaped antenna geometry. Based on the physical interpretation of the characteristic modes the antenna shape is modified to get the desired radiation characteristics using following four step procedure:

Abstract—An ultra-wideband (UWB) planar monopole antenna integrated with a narrow-band (NB) cylindrical dielectric resonator antenna (DRA) is presented. The proposed antenna consists of a UWB monopole excited by a coplanar waveguide (CPW) transmission line, acting as a ground for a DRA excited by a slot. The mode HEM 11δ is excited in the NB DRA. To validate the concept of integration, an antenna is fabricated and measured. The measured results demonstrate that the UWB antenna provides a 2 : 1 voltage standing wave ratio (VSWR) bandwidth for 3.05–11 GHz, integrated with a dual-band NB antenna. Moreover, the two ports have the same polarization and a reasonable isolation (less than −10 dB) between each other. This is a promising candidate for applications in cognitive radio, where the UWB antenna can be used for spectrum sensing and the NB antenna for communication operation.

In this investigation, a compact triple-band monopole antenna for WLAN/WiMAX bands is proposed. The antenna comprises a circular ring around and a goblet-shape-like strip inside. The trapezoid CPW-fed structure works as a balun, which converts between the unbalanced coaxial cable and the balanced symmetrical loop antenna. Thus, the efficiency and gain of the antenna are enhanced. By etching an extra rectangular split ring resonator (SRR) onto the original monopole antenna, better impedance matching is achieved, broadening the bandwidth especially the middle band covering from 3.23 GHz to 4.14 GHz. The small gap within the SRR structure produces large capacitance values which lower the resonance frequency and reduce the area of the antenna. By utilizing a modified trapezoid coplanar waveguide (CPW) feed structure and optimizing the dimension of the strip, the upper band is broadened and covers from 5.08 GHz to 6.03 GHz. Compared with a conventional UWB planar monopole antenna, the proposed antenna tunes the bandwidth of middle band more easily, by optimizing the lengths of d1 and d2, and obvious change can be found from 3.2–4.1 GHz. In addition,

Differential evolution (DE) as a new algorithm was proposed by Price and Storn [2–4]. It is an effective, robust, and simple global optimization algorithm, which only has a few control parameters. DE has been successfully applied to many EM problems, such as array synthesis [5], electromagnetic imaging [6], and synthesis of coplanar strip lines [7]. Meanwhile, to solve binary optimization problems, some binary versions of DE have been proposed [8, 9]. In [9], a novel binary version of DE, namely Boolean differential evolution (BDE), has been applied to thinned array design, and it is observed that DE is also a powerful tool for binary optimization problems. Genetic algorithm (GA) optimized mesh-grid structure has been widely used in electromagnetic design, problems, such as microstrip patch antenna [10], planar monopole antenna [11], and frequency selective surface (FSS) [12] design ones.

Planar monopole ultrawideband (UWB) antenna has drawn wide interest from the researchers for increasing the data rate in wireless communication, since the Federal Communications Commission (FCC) released 3.1 to 10.6 GHz as an unlicensed band for radio communication. Due to many attractive features, such as simple structure, small size, light weight, and low cost, printed monopole antennas are the most frequently used antennas for UWB applications [1–4]. However, the planar monopole antenna design for UWB communication system is still facing many challenges. The UWB communication system has allowed very low power emission level, thus it could be easily interfered by nearby communication systems such as WiMax communication system operating at 3.5 GHz (3.4–3.7 GHz), WLAN system such as IEEE 802.11/a operating at 5.2 GHz (5.15–5.35 GHz, 5.725–5.875 GHz) and X-band downlink communication frequency operating at 7.5 (7.1–7.76 GHz). So the interferences of these narrowband communication systems with UWB systems should be avoided for better performance. To avoid interference, band-stop filer can be used. However, the use of band-stop filter requires more space to integrate, and it also increases the cost and complexity of the system. A better way to avoid interference is using UWB antenna with band-notch characteristic.

The proposed antenna design satisfies WLAN/WiMAX standards. The details of the proposed antenna geometry are presented and discussed in section 2. Simulated results and discussions are provided in section 3, and conclusions are presented in section 4.

On the other hand, the antennas designed for applications in communication systems, such as WLAN and GSM should have acceptable performance in the specified frequency bands, rather than merely exhibit wide bandwidths outside the designed operation frequencies. Accordingly, in this paper we intend to design a dual band printed monopole antenna. The objective is to add an adjustable operation frequency band to the proposed antenna. Examples of antenna structures with multiband characteristics are PIFA [10] and stacked antenna [11], which suffer from being 3-dimensional (which leads to occupying a large space contrary to the prevalent trend for miniaturization) and complexity of fabrication (which is against the economic requirements of mass production of devices, such as mobile sets). The proposed structure consists of the inductive loading of triangular patch, which is fabricated by simple photolithography technology.

Parasitic elements are used between the antennas to cancel part of the coupled fields between them by creating an opposite coupling field thus reducing the overall coupling on the victim antenna using parasitic tape and stepped impedance resonator as parasitic element [22, 23]. A T-shaped ground stub with a slot is used between the two square monopole elements to reduce mutual coupling in [24]. The T-shaped ground stub improves the matching of antenna, and the slot within it improves the isolation by reflecting radiation from the radiators. The mutual coupling between adjacent MIMO antenna elements can be reduced by introducing defects within the ground plane. The defects act as band reject filters and suppress the coupled fields between the adjacent antenna elements by decreasing the current on the ground plane and hence increasing the separation between the elements. The defects can be slitted ground and circular split ring [25, 26]. In [27], an H-shaped DGS W d × L d of dimension 2 × 20 mm 2

In order to achieve the best performance, key parameters of parallel line and monopole are tuned. In Figure 5, as d or g increases, the wide band provided by CRLH-TL becomes slightly narrower or remains unchanged. It is confirmed that the slight parameter changes have little influence on the equivalent inductance and capacitance of transmission line. Great influence is observed in different resonant modes in Figures 5(c) and (d). The electrical length of the right arm can affect not only its resonant mode, but also the TL’s resonant mode, and the dimension of left arm mainly controls the first resonance, which agrees with current distribution in Figure 4.

Various papers focused to scale back the mutual coupling through distinctive enhancement method. MIMO antenna contains two planar Monopole set oppositely to each other to accomplish high isolation between the ports [3]; the MIMO antenna system is made of two symmetric printed monopole antenna and a decoupling method to accomplish isolation further noteworthy than -15 dB [4]; two U- shaped slots are acquainted with to reduce the coupling between the MIMO antenna elements [5]. Two types of antenna elements imprinted on different sides of the substrate to achieve extraordinary isolation and a series of slits are etched in the ground plane that enhances the isolation stage by level of 10 dB [6]. The Procedure contains in embedding a parasitic lossless radiating elements between the antennas with optimized position, measurements, and size. It obtained isolation higher than 15 dB [7].The EBG likewise improved array performance by eliminating with blind spots and grating lobes [8].To lower the coupling and thus improve the antenna’s total efficiency, optimized neutralization lines were embedded between the radiating elements [9].The isolation is improved by reversed Y formed stub on ground plane. The noteworthy increment in port isolation nearly as good as reduction in mutual coupling with the help of utilizing the stub has helped in miniaturizing the antenna [10]. This article planned a straightforward layout for reducing mutual coupling between two planar monopole by introducing slots in the ground plane [11].