GHz WLAN Systems Research Articles

Compact UWB flexible elliptical CPW‐fed antenna with triple notch bands for wireless communications

A coplanar waveguide (CPW)-fed flexible elliptical antenna with triple band notched characteristics is presented in this article. The designed antenna consists of an elliptical patch and slots incorporated CPW feed line to cover the bandwidth requirements for ultra-wideband (UWB) applications. The designed UWB antenna has a fractional bandwidth of about 166.19% (1.20-13 GHz) with a center frequency of 7.1 GHz in simulation and about 170.10% (1.05-13 GHz) with a center frequency of 7.025 GHz in measurement. The overall dimension of the proposed flexible antenna is 45 × 35 × 0.6 mm3. The triple notched bands are realized by designing with circular shaped split-ring-resonators (SRRs) and defected ground structure (DGS). According to the measurement, first notched band (2.0−2.70 GHz) is generated for rejecting 2.4 GHz WLAN by introducing a single circular ST-SRR on the radiating patch. The second notch (3.45-3.80 GHz) is obtained by embedding another circular ST-SRR on the patch to mitigate the interference of 3.5 GHz Wi-MAX system. Finally, due to presence of DGS, third notch (5.15-6.20 GHz) is produced which suppresses the interference from 5.5 GHz Wi-MAX and 5.2/5.8 GHz WLAN systems. The proposed antenna offers excellent performance in different flexible conditions that confirm its applicability on curved surfaces for UWB systems.

MFOA-integrated modified inverted F-based adaptive array Antenna for 2.4 GHz band applications

This research has proposed a modified fruit fly optimization algorithm (MFOA)-integrated adaptive array antenna (AAA) for the 2.4–2.5 GHz WLAN system. The principal components of the array antenna system encompass four array elements, four band pass filters (BPF), four digital phase shifters, a four-way power combiner/splitter, a directional coupler, a radio frequency (RF) detector, and a microcontroller unit (MCU). In the realization of the adaptive antenna system, the modified inverted F antenna with a finite ground plane was first innovated and subsequently deployed as the element of the four-element array antenna. In the study, simulations and experiments were carried out with the four-element AAAs of two configurations, i.e. the linear and planar array configurations. The simulation and experimental results revealed that the MFOA algorithmic scheme could determine the direction of the maximum arrival signal in an efficient and accurate manner and also was capable of manipulating the radiation pattern in the desired direction. In addition, the MFOA-integrated four-element AAA is of compact size (20 mm × 35 mm × 1.8 mm) and operable in the 2.31–2.55 GHz frequency band with omnidirectional radiation pattern and a gain of 1.6 dBi. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016.

A Horizontally Polarized Rectangular Stepped Slot Antenna for Ultra Wide Bandwidth With Boresight Radiation Patterns

In this paper, a horizontally polarized UWB antenna is proposed. The UWB nature of the antenna is achieved using a stepped impedance microstrip feed line to excite the stepped slot configuration. The -10 dB experimental impedance bandwidth acquired from VNA is 10 GHz (from 3.2 GHz to 13.2 GHz) which is 122% at the center frequency of 8.2 GHz. Symmetric feeding of the slot ensures good polarization characteristics and uniform radiation patterns throughout the operating band. The measured co to cross polarization ratio in boresight direction is around 15 dBi over most of the frequencies while the average peak gain is around 5 dBi. With the help of parametric studies, the choice of the antenna dimensions is justified. Finally, a modified design with band-notch characteristics to suppress interference from 5 GHz WLAN systems is presented. The simulated and measured results are in good agreement.

A Spatial Diversity Technique for IEEE 802.11ad WLAN in 60 GHz Band

This paper shows that a spatial diversity technique can maintain a stable link quality for a 60 GHz WLAN system in an indoor multi-path environment, which suffers from the human-induced shadowing. The 60 GHz spatial diversity technique is validated by simulations and experiments.

DUAL-BROADBAND TWIN-PAIR INVERTED-L SHAPED STRIP ANTENNA FOR WLAN/WIMAX APPLICATIONS

A simple and novel printed monopole antenna with dual broad operating bands is presented. The antenna fed by a 50-› microstrip line is composed by dual twin-pair inverted-L shaped strips as well as a small back truncated ground. By properly selecting widths of these inverted-L shaped stripes, dual broad bandwidths formed from triple resonances to meet the band requirement of the 2.4/5.2/5.8 WLAN or the 2.5(3.5)/5.5GHz WiMAX standard can be achieved. Experimental results for case of the obtained antenna prototype suitable for use in a 2.4/5.2/5.8GHz WLAN system have been done and shown good agreement with simulation. Good radiation performances including dual wide bandwidths of 270MHz and 3.16GHz, high average antenna gains of ‚ 2:6 and 4.6dBi, and monopole-like radiation patterns over the two operating bands, respectively, make this antenna a good candidate for use in the modern dual-broadband wireless communication system.

Compact CPW‐fed tri‐band monopole antenna for PCS and 2.4/5GHz WLAN applications

AbstractA compact tri‐band monopole antenna with coplanar waveguide (CPW)‐fed structure is presented for applications in PCS and 2.4/5 GHz WLAN systems. By using a spiral strip and a meandered strip closed to an inverted‐L ground strip, the proposed antenna with a compact size of 30 × 30 × 1.6 mm3 including the ground can not only meet the impedance bandwidth requirements for PCS band (1.85–1.99 GHz) and WLAN bands (2.4–2.484 GHz and 5.15–5.825 GHz), but also can provides good radiation characteristics and antenna gains for the operating bands, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2495–2498, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24593

Triple‐band CPW‐fed monopole antenna with branch strips for wireless applications

AbstractBy properly loading branch strips to a monopole antenna fed by a coplanar waveguide (CPW) feedline, an antenna with good impedance matching in a wide triple‐band covering PCS‐1900/UMTS‐2100 and the 5.2/5.8 GHz WLAN systems is designed. Prototype of the proposed antenna has been constructed and experimentally studied. The measured results not only explore wide −10 dB impedance bandwidths of 21, 18, and 15% at the operating bands of 2.16, 5.27, and 7.52 GHz, respectively, but also show good agreement with the numerical predictions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2794–2797, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23815

Compact dual‐band bandpass filter using stepped impedance resonators

AbstractA new dual‐band bandpass filter (BPF) for 2.4/5.2 GHz WLAN systems using two‐stepped impedance resonators is presented. With new properly coupled structure, this filter appears very compact and easy to be fabricated. Measured results show that this BPF has low insertion loss of 0.3 dB at 2.4 GHz and 0.7 dB at 5.2 GHz, and wide fractional bandwidths of 30% for the first band and 17% for the second band, respectively. Measured results are in good agreement with the simulated ones. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1292–1294, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23357

Oblique Incidence Performance of a Novel Frequency Selective Surface Absorber

Oblique incidence performance of a novel two-layer absorb/transmit frequency selective surface (FSS) is investigated. The FSS has good frequency stability for both horizontally and vertically polarized waves incident normally or at oblique angles. Due to its transmission for 900/1800/1900 MHz mobile bands and good absorption for 5 GHz waves, it has the potential as a security wall or isolator for 5 GHz WLAN systems. The absorption in the stop band helps reduce additional WLAN multipath fading caused by conventional reflecting FSS designs. The first layer of the FSS consists of conventional conducting cross dipoles having a circular aperture in the centre, while the second layer uses resistive cross dipoles. Moreover, the conducting cross dipoles have been sandwiched between two dielectric sheets to achieve a stable response for different angles of incidence. The periodicity of both FSS layers is the same while the distance between the two layers is reduced to one eighth of the free-space wavelength. This reduction leads to a more compact design compared to the conventional Salisbury screen, while still achieving acceptable absorption in the stopband. Both theoretical and experimental results are presented to confirm the performance of the absorb/transmit FSS.

Design and fabrication of pHEMT MMIC switches for IEEE 802.11.a/b/g WLAN applications

In this paper, we propose a channel structure for a promising switch pHEMT with excellent isolation characteristics based on the distribution of electric field intensity beneath the Schottky contact in the transistor. Using the proposed device channel structure, SPST and SPDT switches were designed and fabricated, applicable to 2.4 GHz and 5.8 GHz WLAN systems. We discuss the relationship between dc characteristics and switch parameters in this paper in detail. The developed SPST switch exhibits a low insertion loss of 0.26 dB and a high isolation of 34.3 dB with a control voltage of 0 V/−3 V at 5.8 GHz. The SPDT also shows a good performance of 0.85 dB insertion loss and 31.5 dB isolation under the same conditions. The measured power-handling capability at 2.4 GHz reveals that the SPDT has an output power of 27 dBm at the 1 dB compression point and a third-order intercept point of more than 46 dBm.

Compact diversity antenna for wireless devices

A compact diversity antenna, consisting of two E-shaped microstrip patch antennas, is presented. It has a wide bandwidth, covering all frequency bands of 5–6 GHz WLAN systems operating under IEEE 802.11a and HiperLAN2 standards. Corrugations have been introduced to reduce the overall width of the diversity configuration to 54 mm—the width of a standard PCMCIA card. The isolation between the two inputs is greater than 20 dB and the signal correlation is less than 0.2 over all WLAN bands.