Wireless LAN Applications Research Articles

Monopole Patch Antenna with Dual Band of 2.4 and 5 GHz Designed for Wireless LAN Applications

A compact prototype of dual band monopole antenna has been fabricated on PCB with small overall size of 36.6 mm×47 mm. By the trial of simulation to tune the dimensions of PCB, an optimum design of antenna can be obtained. Dual resonances excited in 2.4 and 5 GHz bands. For return loss more than 9.6 dB, the achieved bandwidths are 2.41 to 2.77 GHz in 2.4 GHz band and 5.11 to 5.83 GHz in 5 GHz band. The return loss ( ) can keep larger than 9.6dB within the bands of 2.4 and 5 GHz.

Reduction of Cross Polarization of Slotted Microstrip Antenna Array Using Spiral‐Ring Resonator

ABSTRACTDesign of a (2 × 2) E‐shaped microstrip patch antenna array integrated with spiral‐ring resonators (SRRs) is introduced for the reduction of cross‐polar (XP) radiation. The addition of SRRs in the array structure does not affect other characteristics of the array antenna. The array is designed to function in the 5.25 GHz that corresponds to IEEE 802.11a wireless LAN application. The characteristic analysis such as return loss (RL), bandwidth (BW), and radiation patterns of the antenna with and without SRRs have been investigated. The array offers a BW of 405 MHz (for RL < −10 dB) covering frequencies ranges from 5.175 to 5.580 GHz and gain of 12.84 dBi has been achieved. The array has been studied both numerically and experimentally by introducing SRRs. The SRR geometry has been optimized for minimum XP radiation. The XP radiation has been reduced by 7 dB with two SSRs and 12.0 dB by four SRRs of similar geometry, placed in between the patch elements of the array structure. Prototype antennas with and without SRRs have been fabricated tested and a remarkable agreement is obtained between the measured and the simulated results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2083–2088, 2013

CROSS-POLARIZATION REDUCTION OF E-SHAPED MICROSTRIP ARRAY USING SPIRAL-RING RESONATOR

Design of (2 £ 2) E-shaped microstrip patch antenna array integrated with spiral ring resonators (SRRs) is introduced for the reduction of cross-polar (XP) radiation. The addition of SRRs in the array structure does not afiect other characteristics of the array antenna. The array is designed to function in the 5.25GHz which corresponds to IEEE 802.11a wireless LAN application. The characteristic analysis such as return loss (RL), bandwidth (BW), and radiation patterns of the antenna with and without SRRs have been investigated. The array ofiers a bandwidth of 405MHz (For RL < i10dB) covering frequencies ranges from 5.175 to 5.580GHz and gain of 12.60dBi has been achieved. The array has been studied both numerically and experimentally by introducing SRRs. The XP radiation has been reduced by 10.5dB with two sets of SSRs of similar geometry placed in between the patch elements of the array structure. Prototype antennas with and without SRRs have been fabricated tested and a remarkable agreement is obtained between the measured and the simulated results.

A Survey on Recent Approaches in the Design of Band Notching UWB Antennas

According to federal communication commission (FCC) rules, the 3.1 - 10.6 GHz band is allocated to the amateur ultra wideband (UWB) applications. On the other hand, the 5.15 - 5.825 GHz band is associated with the wireless LAN (WLAN) applications according to IEEE 802.11 and HIPERLAN/2 standards. Therefore, an unwanted intrusion will be expected between these two frequency requests. In This paper a comprehensive review will be done over a wide range of UWB microstrip antennas which all have the band notching property over the WLAN band to effectively avoid this interference. All the band notching techniques in the recent papers will be categorized in 4 distinct methods including the tuning stub, the shaped slot, the parasitic element, and the fractal geometry. A few typical papers will be introduced and evaluated in each category for declaration purposes. At last, a comparison will be done between these methods and the relative papers.

Low profile dual‐feed Planar Inverted‐F Antenna for wireless LAN applications

AbstractThis letter presents a new low profile dual‐feed Planar Inverted‐F Antenna (PIFA) suitable for wireless LAN applications. Pattern diversity is exploited using one common radiating plate and two isolated feeding ports. The isolation is successfully achieved mainly by modifying the ground plane under the radiating plate and producing an antiresonance between the ports. Thus, this single PIFA antenna can act as two separate antennas for diversity and MIMO applications with reduced space and cost. Simulated and measured results are obtained to verify the conclusion. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1382–1386, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25958

Tunable, continuous-wave Terahertz photomixer sources and applications

This review is focused on the latest developments in continuous-wave (CW) photomixing for Terahertz (THz) generation. The first part of the paper explains the limiting factors for operation at high frequencies ∼ 1 THz, namely transit time or lifetime roll-off, antenna (R)-device (C) RC roll-off, current screening and blocking, and heat dissipation. We will present various realizations of both photoconductive and p-i-n diode–based photomixers to overcome these limitations, including perspectives on novel materials for high-power photomixers operating at telecom wavelengths (1550 nm). In addition to the classical approach of feeding current originating from a small semiconductor photomixer device to an antenna (antenna-based emitter, AE), an antennaless approach in which the active area itself radiates (large area emitter, LAE) is discussed in detail. Although we focus on CW photomixing, we briefly discuss recent results for LAEs under pulsed conditions. Record power levels of 1.5 mW average power and conversion efficiencies as high as 2 × 10−3 have been reached, about 2 orders of magnitude higher than those obtained with CW antenna-based emitters. The second part of the paper is devoted to applications for CW photomixers. We begin with a discussion of the development of novel THz optics. Special attention is paid to experiments exploiting the long coherence length of CW photomixers for coherent emission and detection of THz arrays. The long coherence length comes with an unprecedented narrow linewidth. This is of particular interest for spectroscopic applications, the field in which THz research has perhaps the highest impact. We point out that CW spectroscopy systems may potentially be more compact, cheaper, and more accurate than conventional pulsed systems. These features are attributed to telecom-wavelength compatibility, to excellent frequency resolution, and to their huge spectral density. The paper concludes with prototype experiments of THz wireless LAN applications. For future telecommunication systems, the limited bandwidth of photodiodes is inadequate for further upshifting carrier frequencies. This, however, will soon be required for increased data throughput. The implementation of telecom-wavelength compatible photomixing diodes for down-conversion of an optical carrier signal to a (sub-)THz RF signal will be required.

Analysis, Design, and Evaluation of LDMOS FETs for RF Power Applications up to 6 GHz

The analysis, design, and evaluation of medium-voltage laterally diffused metal oxide semiconductor (LDMOS) transistors for wireless applications up to 6 GHz is presented. Using an optimized N-LDMOS transistor, power devices of different transistor geometries were fabricated in a standard 0.25-μm bipolar complementary metal oxide semiconductor (BiCMOS) technology with and without on-chip stabilization networks. The influences of the finger geometry and the stabilization networks on the RF performance were studied based on small-signal and large-signal on-wafer measurements. It was analytically shown and experimentally verified that transistor geometries with reduced gate width per finger but higher number of fingers are advantageous regarding the maximum oscillation frequency. From the source/load-pull characterization of a 1.8-mm total gate-width device, state-of-the-art, large-signal performance with a maximum output power of 29.7 dBm and a peak drain efficiency of 44% were obtained at 5.8 GHz. Power evaluation of the LDMOS transistors was also carried out in designed hybrid power amplifier modules targeted for vehicular wireless LAN applications. In the 5.8-5.9 GHz band, an output power of 1 W at 1-dB power compression, an adjacent channel power ratio of -38 dBc and an error vector magnitude of 3% at 1 dB peak power compression are reported.

Design of nonlinear CMOS circuits in the Nano-GHz Era and its mathematical challenges

Abstract Modern communication systems are working on industrial, scientific and medical (ISM) radio frequency (RF) bands. Today most research and development activities in industrial companies and universities are concentrated to frequency bands between 1 GHz and 24 GHz up to 60 GHz. For the construction of mixed-signal chips for cellular telephones and other wireless LAN applications (Bluetooth, HIPERLAN, etc.) different semiconductor technologies are used. In order to combine analogue functionality for the RF front end and digital functionality for high-speed signal processing nonlinear circuit concepts must be used and CMOS technology has to be applied. In order to construct high-quality RF transceiver chips a submicron CMOS technology (180 nm and below) is needed. Therefore we come into the Nano-GHz Era of circuit design. In this work corresponding mathematical challenges of modern RF CMOS design of transceiver circuits, with a focus on oscillator circuits, are discussed. It is shown that these circuits can be modelled as dynamical systems and their environment and their devices by partial differential equations. For circuit design aspects bifurcation theory and other mathematical concepts from dynamical systems as well as advanced numerical methods can be applied in order to build up an efficient design system for these RF CMOS circuits. In this paper some key aspects of future circuit design will be presented and discussed.

ANALYSIS AND DESIGN OF A GAUSSIAN BACKSCATTER ANTENNA WITH RING FOCUS FEED

This paper presents analysis and design of a Gaussian backscatter antenna with ring focus feed. The curvature of main re∞ector is Gaussian, and the subre∞ector is a portion of an ellipse. The antenna has axial symmetry. A backscattering technique is used with the main re∞ector to achieve wide beamwidth. The input parameters of the proposed antenna are derived in closed form. Physical theory of difiraction (PTD) is used to analyze the radiation pattern of the proposed antenna and verifled with experimental results. The efiects of the support structures on the radiation patterns of the proposed antenna have been investigated experimentally. The proposed antenna can produces high gain and wide beamwidth (coverage angle µ = §65 - ). This antenna can be used for realizing earth coverage beam in LEO satellite or indoor wireless LAN applications.

Reconfigurable Single Port Antenna With Circular Polarization Diversity

New design of a single feed reconfigurable circular patch antenna with polarization pattern diversity is presented. The radiating circular patch, printed on a thin substrate, is supported by non conductive posts on a conducting ground plane and is excited with a capacitively coupled feed. Wideband impedance matching is achieved. The pattern diversity is generated using two switch parasitic pins between the circular patch and the ground plane. By optimizing the position of the switching elements, two orthogonal patterns with the right-hand circular polarization (RHCP) and the left-hand circular polarization (LHCP) are generated. These patterns are used for diversity reception in indoor fading channel for wireless LAN applications. Detailed design of the antenna is described. Experimental results for return loss, radiation patterns, radiation efficiency, antenna gain, axial ratio and the diversity performance in Rayleigh fading channel are presented.

Dual-band bandpass filter with source-load coupling

A compact dual-band bandpass filter is presented for wireless LAN applications. Using two centrally-loaded stepped-impedance resonators, the second passband frequency can be conveniently tuned. Two transmission zeros are generated between the two passbands because of source-loading coupling topology. Simulated results show that two central frequencies are located at desired 2.4 and 5.7 GHz with 3 dB fractional bandwidths of 18.8 and 7.1%, respectively. Comparison of measured and simulated results shows good agreement.

Design of 5 GHz-Band Power Amplifier with On-Chip Matching Circuits Using CPW Impedance (K) Inverters

This Letter employs transmission-line theory for the impedance-matching circuits for a single-chip power amplifier (PA) and verifies for 5GHz-band wireless LAN (IEEE 802.11a) applications. The presented matching circuits are composed of conductor-backed coplanar waveguide (CPW) meander-line resonators and impedance (K) inverters. One of the advantages of the presented circuits is that it can save on-chip space occupied by the matching circuits compared to that using the spiral inductors, thus reducing the cost. The prototype chip, which consists of PA and matching circuits, is designed employing the presented theory and fabricated. A few of the measured results to verify the design theory are presented.

An Efficient Scheduling Scheme for Assigning Transmission Opportunity in QoS-Guaranteed Wireless LAN

The IEEE 802.11e standard defines several important techniques that guarantee the quality of service (QoS) of multimedia communications in wireless LAN applications. A key technique introduced in the standard is an efficient media access control based on the Hybrid Coordination Function (HCF), which assigns an appropriate transmission opportunity (TXOP) to each flow for satisfying several requirements on the flow, such as delay bound and communication bandwidth. Although the simple scheduler designed in HCF could provide an efficient tool to guarantee the QoS in wireless LAN applications, it has a serious drawback, wherein a useless bandwidth assignment frequently occurs. Such assignments occur primarily due to a limitation of the scheme, wherein all the flows share the same service interval (SI). In this paper, we propose a new scheduling scheme that associates each flow with its own SI according to the hardness of the required SI. The effect of this approach is experimentally evaluated by simulation, the results of which indicate that the number of admitted flows and network resource utilization increase due to the proposed scheme.

Implementation of a 5‐GHz LTCC bandpass filter using vertically‐interdigitated capacitors and via engineering

AbstractA low‐temperature cofired ceramic (LTCC) LC resonator bandpass filter for 5‐GHz wireless LAN applications is implemented. The miniaturization of the filter is achieved by utilizing vertically‐interdigitated capacitors as resonator capacitors, and the required small inductance (∼ 0.1 nH) is realized by via holes. The inductances of via‐holes connecting the capacitor plates also considerably affect the filter characteristics, and they are considered in circuit design stage of the filter. The fabricated bandpass filter has five layers with the size of 2.4 × 4.18 × 0.56 mm3. The measured center frequency, bandwidth, and insertion loss are 5.32 GHz, 340 MHz, and 2.87 dB, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 339–341, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23072

Exposure of the general public due to wireless LAN applications in public places

The typical exposure caused by wireless LAN applications in public areas has been investigated in a variety of scenarios. Small-sized (internet café) and large-scale (airport) indoor scenarios as well as outdoor scenarios in the environment of access points (AP) supplying for residential areas and public places were considered. The exposure assessment was carried out by numerical GTD/UTD computations based on optical wave propagation, as well as by verifying frequency selective measurements in the considered scenarios under real life conditions. In the small-sized indoor scenario the maximum temporal peak values of power density, spatially averaged over body dimensions, were found to be lower than 20 mW/m(2), corresponding to 0.2% of the reference level according to the European Council Recommendation 1999/519/EC. Local peak values of power density might be 1-2 orders of magnitude higher, spatial and time-averaged values for usual data traffic conditions might be 2-3 orders of magnitude lower, depending on the actual data traffic. In the considered outdoor scenarios, exposure was several orders of magnitude lower than in indoor scenarios due to the usually larger distances to the AP antennas.

Compact wideband inverted planar monopole antenna

AbstractIn this article, an inverted planar monopole antenna with two shorting plates is proposed. This inverted planar monopole antenna provides a 3.55:1 impedance bandwidth (for VSWR &lt; 2). Owing to its compact size and wide impedance bandwidth, this antenna is suitable for CDMA, GSM, DCS, PCS, and wireless LAN (IEEE 802.11b) applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2913–2914, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22900

Digitally controlled linear-in-dB variable-gain amplifier for high-frequency applications

A design technique to implement a digitally controlled dB-linear variable-gain amplifier (VGA) for high-frequency applications is presented. The design approach is applicable to current-steering VGAs and is based on a digital gain control circuit that operates as a nonlinear digital-to-analogue converter to achieve a digitally controlled dB-linear gain control characteristic. Using the proposed approach, a variable-gain up-converter for 5-GHz wireless LAN applications has been fabricated with a low-cost 46-GHz-f rceil silicon bipolar technology. The adopted VGA, operating at a frequency of 1 GHz, provides a linear-in-dB gain control characteristic over a 30-dB dynamic range with a 2-dB step and a +0.8-dB gain error.

Low-Loss 5.15–5.70-GHz RF MEMS Switchable Filter for Wireless LAN Applications

Low-loss 3.6-GHz fixed and 5.15-5.70-GHz RF microelectromechanical systems switchable filters were designed and fabricated on quartz substrates. Detailed design equations for the capacitively loaded coupled open-loop lambda/2 resonators are given and the realization of the tunable filter using these equations is discussed. The use of capacitively loaded coupled open-loop lambda/2 resonators made it possible to realize the fixed and switchable filters with unloaded Q of around 150 resulting in a -1.4-dB insertion loss. The measured -1-dB bandwidth for the 3.6-GHz fixed and 5.15-5.70-GHz switchable filters were 4% and 5%, respectively. To our knowledge, this represents the lowest loss planar tunable filter to-date in the 4-6-GHz frequency range

A Novel Dual Band Transmitter for Wireless LAN IEEE 802.11a/g Applications with Digital Predistortion Linearization

A novel dual band transmitter module for 2.4 GHz and 5.8 GHz wireless LAN applications with adaptive digital predistortion linearization is presented. The module operates either as a power amplifier for 2.4 GHz or frequency doubler for 5.8 GHz band. Amplification gain is 12.9dB at 2.4 GHz and multiplication gain is 3.3dB at 5.8 GHz. At 2.4 GHz band, the second harmonic is about 36.5 dB lower than the fundamental, and the 2.9 GHz fundamental signal is 20.3 dB lower than the second harmonic output at 5.8 GHz operation. An adaptive digital predistortion scheme is proposed to linearize the 2.4 GHz amplifier, and to get the proper 5.8 GHz band wireless LAN signal. The 2.4 GHz amplifier with predistortion satisfies the ACPR mask requirement for the input 1 dB compression power of 5 dBm and the linearized frequency doubler shows 26 dB ACPR improvement at 11 MHz offset from center frequency by using the proposed predistortion linearization. The frequency doubler output spectrum with prdistortion does meet the IEEE standard Tx mask.

Improvements on “IP – IAPP”: A fast IP handoff protocol for IEEE 802.11 wireless and mobile clients

One of the most critical issues in introducing Wireless LAN (WLAN) real-time and delay sensitive applications, such as Voice over IP (VoIP), is guaranteeing IP service continuation during inter-subnet Basic Service Set (BSS) transitions. Even though WLANs offer very high channel bandwidth, they exhibit long network-layer handoff latency. This is a restraining factor for mobile clients using interactive multimedia applications such as VoIP or video streaming. In a previous work, we presented a novel fast and efficient IP mobility solution, called "IP-IAPP", which offers constant IP connectivity to the 802.11 mobile users and successfully preserves their ongoing sessions, even during subnet handoffs (fast recovery of active connections). It is an 802.11-dependent IP mobility solution, which accelerates the network reconfiguration phase after subnet handoffs and significantly reduces the IP handoff latency. It restores L3 connectivity almost simultaneously to the L2 connectivity after a subnet handoff, due to a zero-delay movement detection method. As a result, even the most demanding next generation WLAN applications such as Voice over WLAN (VoWLAN) suffer insignificant disruption. In this paper we present an improved version of the IP-IAPP mobility mechanism (new optimized protocol procedures). Certain extensions have also been incorporated to the initial proposal, for the provision of more advanced services: (a) secure inter-AP IP-IAPP communications, (b) zero patching on the clients s/w, and (c) support of clients which use a dynamic IP address. Performance measurements out of further and more complex testing verify that the proposed method outperforms other existing mobility solutions, and still introduces the lesser imperative amendments to the existing 802.11 wireless LAN framework.