To incorporate two different communication standards in a single device, a compact triple-band antenna is proposed in this paper. The proposed antenna is formed by etching an inverted L-shaped slot on the patch with defected ground structure. The antenna is targeted to excite three separate bands first from 2.39–2.51, second from 3.15–3.91, and third from 4.91–6.08 GHz that covers entire Wireless Local Area Network (WLAN) (2.4/5.2/5.8 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) (2.5/3.5/5.5) bands. Thus, the proposed antenna provides feasibility to integrate WLAN and WiMAX communication standards in a single device with good radiation pattern quality. Furthermore, a prototype of the proposed antenna fabricated and measured to validate the design, shows a good agreement between simulated and measured results. The simulation and measurement results show that the designed antenna is capable of operating over the 2.39–2.51 GHz, 3.15–3.91 GHz, and 4.91–6.08 GHz frequency bands while rejecting frequency ranges between these three bands. The proposed antenna offers a compact size of 20 × 30 mm2 as compared with earlier reported papers.

Triple band circularly polarized fractal boundary microstrip antenna is proposed and experimentally studied. The two orthogonal sides of the square patch are replaced with asymmetrical fractal curves for circular polarization (CP) radiation. A 45° rotated asymmetrical fractal slot is embedded at the center of the fractal patch for triband CP operation. The indentation factors of the fractal curves are optimized for better CP emission. The inserted fractal slot redistributes the current elements on the patch for triband CP radiation. The proposed antenna is implemented over a single layer with a single probe feed, so it is simple to fabricate and is cost effective when compared with the existing stacked layered multiband antennas in the open literature. The measured 3 dB axial ratio bandwidths of the proposed antenna at 2.4, 3.4, and 5.8 GHz are 2, 1, and 1.8%, respectively, so it is well suited for WLAN and Wi-MAX wireless applications.

With quad-band-notched characteristic, a compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna is introduced in the paper. The UWB–MIMO system has two similar monopole elements and occupies 30 × 45 mm2. By inserting two L-shaped slots, CSRR and C-shaped stubs, four notched bands are achieved (3.25–3.9, 5.11–5.35, 5.5–6.06, and 7.18–7.88 GHz) to filter WiMAX, lower WLAN, upper WLAN, and X-band. Meanwhile, the isolation is obviously enhanced with three metal strips on the ground plane. Results indicate that the antenna covers UWB frequency band of 3.1 – 10.6 GHz except four rejected bands, isolation of better than −18 dB, envelope correlation coefficient of <0.02, and good radiation pattern, thus making it useful for UWB systems.

Fractals have unique properties such as self-similarity and space-filling. The use of fractal geometry in antenna design provides a good method for achieving the desired miniaturization, multi-band, and wideband properties. In this communication, novel fractal geometry is proposed based on which a multiband antenna is designed. The proposed antenna has fractal patches which are shaped as different iterations of an eight-pointed star. The multiband behavior is in the frequency range from 4.50 to 17.00 GHz. The proposed antenna is designed on a dielectric substrate Roggers RO4003 lossy with a dielectric constant of εr = 3.55. The antenna has applications in commercial and military communication system.

In this paper, a vase-shaped monopole antenna is presented for dual band notch (WiMAX IEEE802.16 3.30–3.80 GHz with C-band 3.80–4.20 GHz and WLAN IEEE802.11a/h/j/n 5.15–5.35 GHz, 5.25–5.35 GHz, 5.47–5.725 GHz, 5.725–5.825 GHz) UWB and other wireless services (close range radar: 8–12 GHz in X-band & satellite communication: 12–18 GHz in Ku-band). Measured VSWR of proposed antenna shows a high band-rejection for WiMAX along with C-band with VSWR = 25.33 at 3.77 GHz and WLAN with VSWR = 6.0 at 5.64 GHz is achieved by cutting two C-shaped slots on the radiating patch. Designed antenna covers a wide usable fractional bandwidth 160% (2.58–20.39 GHz). Furthermore, the measured gain of antenna is relatively stable across the impedance bandwidth except band-notched. In addition, antenna offers omni-directional pattern, reasonably small 20 × 20 × 0.787 mm3 and easy to construct structure.

This paper presents a solution to reduce the feed complexity and to improve the total efficiency of X-band compact choke horn antenna with circular polarization and isoflux pattern. This kind of antenna had been designed before by our laboratory for nanosatellite applications, but it required a 4-way divider with phase shifter which generates the insertion losses and therefore a lower realized gain (RG). Among several feeds, a uniform circular helix antenna has been used here, which produces a satisfying feed without too much damage for the axial ratio (AR) and the isoflux pattern over a 400 MHz radiation bandwidth (8.0–8.4 GHz). Theoretical and experimental results show an AR lower than 5 dB and a RG higher than 0 dB at the limit of coverage, i.e. 65° whatever the azimuth angle (φ).

By introducing a modified F-shaped feeding strip and dual parasitic shorted strips, a small-size wireless wide area network/long-term evolution (WWAN/LTE) printed antenna is proposed and embedded in the 4 G mobile phone with octa-band operation. The operating impedance bandwidths (RL ≥ 6 dB) of 263/1093 MHz can be obtained across the LTE/WWAN bands, respectively. The overall antenna size of the proposed printed monopole antenna (MA) is only 35 × 10 × 0.8 mm3. Meanwhile, this small-size MA provides the measured peak gains and antenna efficiencies of 2.0/3.6 dBi and 80/75% for the LTE/WWAN bands, respectively.

A compact three-dimensional (3D) circularly polarized (CP) microstrip antenna is presented in this paper. The antenna adopts three low-cost printed circuit boards to form an integrated and closed 3D structure, and the radiation patch and the feed patches are etched on the surface of that. A crossed slot is cut on the radiation patch to miniaturize the antenna, and triangular feed patches are introduced to increase the bandwidths. In addition, because of the utilization of a low-loss series feed line, the antenna has a high efficiency of more than 95%. A prototype of the antenna is measured to validate the method. The dimensions of the antenna is 0.064λ × 0.36λ (λ is the wavelength in free space at 1.2 GHz). The results indicate that the impedance bandwidth for voltage standing wave ratio ≤ 2 reaches 23%, and the bandwidth for axial ratio (AR) ≤ 3 dB reaches 10.1%. In the overlap band, the gains are > 4.5dBic. Additionally, the 3 dB beamwidth is more than 114°, and the beamwidth for AR ≤ 3 dB is more than 131° at 1.2 GHz.

This paper presents the dual band notch characteristics of Ultra wideband (UWB) monopole antenna. Proposed antenna (30 × 30 mm2) consists of arrow shaped patch and truncated ground plane. Operating range of the proposed antenna (voltage standing wave ratio < 2) is 2.2–11 GHz. In order to achieve dual band stop characteristics, λ/2 open ended angularly separated slit pair has been inserted on the radiator for world interoperability for microwave access (WIMAX) (3.3–3.9 GHz) band rejection performance and wireless local area network (WLAN) (5.1–5.9 GHz) band rejection has been realized by introducing a pair of angularly separated λ/2 conductor backed plane (CBP). Using proper adjustment of angular separation for both slit pair and CBP pair, enhanced band rejection can be achieved for the WIMAX and WLAN band, respectively. The performance of antenna has been investigated in terms of frequency domain and time domain to assess its suitability in UWB communication.

A miniaturized dual-band CPW-fed metamaterial antenna is presented and developed in this paper. Zeroth-order mode is originated by realizing open-ended composite right/left-handed transmission line. A dual split ring resonator is introduced to obtain another mode. The antenna is operated in the frequency region 1.60–1.64 and 2.76–2.79 GHz. Shunt inductance is offered by means of thin stripline connecting ground planes. It is demonstrated that by applying metamaterial loading (thin stripline) proposed antenna is capable to achieve 51.9% miniaturization with respect to the antenna without metamaterial loading. The presented antenna has an electrical size of 0.162 λ0 × 0.108 λ0 × 0.008 λ0 at f0 = 1.62 GHz. The antenna exhibits simulated gain of 1.05 and 2.59 dB in the broadside directions at 1.62 and 2.78 GHz, respectively. Beside that this antenna offers dipolar-type pattern and omnidirectional pattern in the xz-and yz-planes respectively at both bands, which is beneficial to be used in modern wireless applications. The design methodology of the proposed antenna is described with the help of current distributions and parametric analysis.

A new planar microstrip-fed monopole ultra-wideband (UWB) antenna with dual notched bands has been presented. By employing a simple dual-mode resonator with two symmetrical outer high-impedance lines beside the microstrip feed line of the proposed UWB antenna, two controllable rejection bands with high-frequency selectivity are created. The parametric studies of the proposed structure are explored for the dual band-notched operating mechanism. Finally, the experimental results, including return losses, radiation patterns, and peak gains are shown, declaring that the proposed antenna has good impedance matching performance and radiation pattern properties.

A novel dual-band single-feed reconfigurable annular-ring slot antenna with polarization diversity is proposed. This antenna has the ability to switch frequency bands and polarization at the same time whereas applying a simple structure. It consists of two concentric circular slots and two tuning stubs on one side of the substrate and a 50 Ω microstrip feed line and two stubs on the other side. The proposed antenna can be switched between two resonant frequencies, 2.4 GHz (WLAN) and 3.5 GHz (Wimax). Furthermore, it can be switched between linear polarization (LP), left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP) at the first frequency band, LHCP and RHCP at the second band. All these capabilities are achieved by applying only five PIN diodes on both sides of the substrate. Simulation and experimental results indicate that the proposed antenna demonstrates a good impedance bandwidth at the two frequency bands and satisfactory radiation pattern in five different states.

Aperture-coupled ESPAR antenna with a unique feed structure for switched beam application has been presented. The feed structure provides control over surface current of the driven element with the help of which main lobe can be steered in desired direction. This control has been achieved through the use of PIN-diodes. Finite element method has been utilized for design and simulated and measured results have been presented for validation. The antenna has the ability to steer the main beam in six directions. All radiation patterns are symmetric. The planar aperture-coupled nature of proposed antenna is ideal for integration and commercialization.

This paper presents a miniature monopole reader antenna for tri-band radio frequency identification (RFID) portable devices. The proposed antenna operates at the main RFID frequencies and can alleviate and compensate for the shortcomings of a single-band antenna. An additional rectangular stub couples with the bent monopole antenna, allowing the latter to resonate at the RFID bands at 902–928 MHz, 2.4–2.48 GHz, and 5.725–5.875 GHz. By bending the feedline, the dimensions of the miniature antenna are reduced to 115.5 × 20 × 1.6 mm3, facilitating its integration into portable devices. The measured bandwidths(return loss < −10 dB) of the proposed antenna are 677, 580, and 250 MHz in the three operating bands, 883–1560 MHz, 2.31–2.89 GHz, and 5.65–5.9 GHz, respectively, with high-gain characteristics. An experimental study of a fabricated prototype of the optimized antenna is performed, and the results verify its good performance.

A compact asymmetric coplanar strip fed Sinc shaped monopole antenna suitable for multifrequency operations is proposed for portable wireless devices. The proposed Sinc shaped monopole antenna with truncated half ground plane operates at three frequency bands, 2110–2380, 4180–4600, and 5200–5678 MHz, showing fractional impedance bandwidths of 12, 9, and 8.8%, respectively, suitable for Universal Mobile Telecommunications System, Long Term Evolution handheld devices, Worldwide Interoperability for Microwave Access, Wireless Local Area Network, Hyperlan-2, and aeronautical navigation applications. Proposed antenna shows a dual mode of polarization. Finally a prototype model is developed for a typical configuration and the simulated results are validated experimentally.

Wide-band circularly polarized multi-input multi-output (MIMO) antenna array with a 2 × 4 feed network was proposed for C-band application. Different unique techniques were utilized in the proposed array to enhance the antenna characteristics, such as gain, 3 dB axial ratio bandwidth (ARBW), impedance tuning, and ruinous mutual coupling effects. A miniaturized dual-feed Tai chi-shaped antenna element with a pair of feeding points and a pair of eyebrow-shaped strips was presented for enhancing circular polarization (CP) purity and impedance matching. For a better improvement of CP features, a 2*4 MIMO sequentially rotated (MIMO-SR) feed network was used to achieve broader 3 dB ARBW. Besides, the MIMO feature of the feed network could control the left- and right-handed CP, respectively. Ultimately, specific forms of slot and slit structures were applied onto the top layer of MIMO feed network that provided a high isolation between the radiating elements and array network. Furthermore, the diversity gain (DG) was studied. The extracted measured results illustrated an impedance bandwidth of 3.5–8.2 GHz at port 1 and 3.5–8.3 GHz at port 2 for VWSR < 2 and 3 dB ARBW of 4.6–7.6 GHz at port 1 and 4.6–7.5 GHz at port 2. The peak gain of 9.9 dBi was at 6 GHz.

An ultra-wideband (UWB) log-periodic dipole array (LPDA) antenna inkjet-printed on a 0.5 mm thick photo paper substrate is presented. The overall size of the LPDA antenna is 130 × 60 mm2. The LPDA antenna exhibits stable input-impedance characteristics and a consistent end-fire radiation pattern over the whole operating band of 2.2–11 GHz. Fulfilling the need of high-gain flexible antennas for UWB, a highly directive measured gain of 9.5 dBi on a paper substrate makes it an excellent candidate for flexible wireless devices.

In this paper, the design of a new compact uniplanar coplanar waveguide-fed antenna for multiband wireless application is presented and investigated. This antenna has a compact size of 25 × 25 mm2 and consists of a three parallel stub optimized added on rectangular slot to the radiator patch and T-shaped which inverted in the ground plane. The final prototype antenna designing resonantes at frequency bands (2.4–2.9 GHz), (3.7–5.2 GHz), and (5.7–6 GHz) with a return loss less than −10 dB. Details of the antenna configuration, design, simulation, and experimental results are presented, investigated, and discussed. The compactness, simple feeding technique, and conception of the uniplanar design make it easy to be integrated within devices of multiples wireless applications.

Defected ground structure (DGS)-integrated arc-cornered rectangular microstrip antenna (RMA) has been investigated to achieve broadband along with high co-polarized to cross-polarized radiation (CP–XP) isolation over principal as well as over skew planes without affecting the dominant mode co-polarized (CP) radiation pattern. The present arc-cornered RMA on circular and rectangular dot-type DGS is thoroughly studied and compared with the conventional rectangular microstrip antenna. In the present paper, a crucial emphasis is given to improve CP–XP isolation in all the skew planes and by employing circular dot-type DGS around 20 dB CP–XP isolation is achieved over whole skew planes as well as in the H-plane with the proposed structure with 20% impedance bandwidth. On the contrary, the CP–XP isolation and impedance bandwidth vary in opposite manner in case of the rectangular dot-type DGS. Around 25 and 10 dB CP–XP isolation with 9 and 22% impedance bandwidth have been obtained with thin and thick rectangular dot-type DGS, respectively. The corners of the patch surface are rounded in such a way to reduce spurious radiations from the sharp corners, which are generally attributed for high XP radiation along the diagonal directions.

A compact dual-frequency antenna with enhanced bandwidth is proposed in this paper. Dual-frequency operation is realized by cutting a slot in the elliptical patch, and bandwidth enhancement is achieved by using a partial ground plane. Compared with the conventional half-wave antenna, the antenna has a compact size of 24 × 20 mm2, which equals to 0.38 λ1 × 0.31 λ1 (λ1, the guided wavelength at the first resonant frequency). The dual-frequency antenna with a partial rectangle ground and a partial arc-shaped ground is investigated for impedance matching. Simulated results indicate that the antenna with a partial arc-shaped ground can obtain a larger bandwidth for two bands than that with a partial rectangle ground. Experimental results show that the antenna with a partial arc-shaped ground can operate in 2.4 and 5 GHz bands, which covers the 2.4, 5.2 and 5.8 GHz for wireless local area network. The impedance bandwidths of two bands are 9.5 and 13.6%, respectively. Also, good radiation performances have been achieved at two bands.