On the Effects of Driven Element L/D Ratio and Length in VHF-SHF Yagi-Uda Arrays

While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-to-diameter ratio. This paper looks at that question. It shows that decreasing the L/D ratio increases impedance bandwidth, but it may shift the IBW band sufficiently far from the design frequency that other parameters such as gain and front-to-back ratio probably are adversely affected. It also shows that array performance is not relatively independent of element diameters. This paper also investigates the effect of lengthening the driven element, which can substantially improve IBW. Several iterations of a 3-element prototype and improved arrays are modeled with the Method of Moments and discussed in detail. A five step design procedure is recommended and applied to a Genetic Algorithm-optimized 3-element Yagi at 146 MHz. This array exhibits excellent performance in terms of gain, front-to-back ratio, and especially impedance bandwidth (nearly 14% for voltage standing wave ratio ≤ 2:1 with two frequencies at which 50 ? is almost perfectly matched). While the analysis and recommended design steps are applied to cylindrical array elements, which commonly are aluminum tubing for stand-alone VHF-SHF Yagis, they can be applied to other element geometries as well using equivalent cylindrical radii, for example, Printed Circuit Board traces for planar arrays. One consequence of lengthening the driven element while reducing its L/D ratio is that some reactance is introduced at the array feedpoint which must be tuned out, and two approaches for doing so are suggested.

Classification Approach for Intrusion Detection in Vehicle Systems

Vehicular ad hoc networks (VANETs) enable wireless communication among Vehicles and Infrastructures. Connected vehicles are promising in Intelligent Transportation Systems (ITSs) and smart cities. The main ob-jective of VANET is to improve the safety, comfort, driving efficiency and waiting time on the road. VANET is unlike other ad hoc networks due to its unique characteristics and high mobility. However, it is vulnerable to various security attacks due to the lack of centralized infrastructure. This is a serious threat to the safety of road traffic. The Controller Area Network (CAN) is a bus communication protocol which defines a standard for reliable and efficient transmission between in-vehicle parts simultaneously. The message moves through CAN bus from one node to another node, but it does not have information about the source and destination address for authentication. Thus, the attacker can easily inject any message to lead to system faults. In this paper, we present machine learning techniques to cluster and classify the intrusions in VANET by KNN and SVM algorithms. The intrusion detection technique relies on the analysis of the offset ratio and time interval between the messages request and the response in the CAN.

Measurement of Rain Attenuation in Terahertz Wave Range

Rain attenuation at 355.2 GHz in the terahertz wave range was measured with our new 355.2 GHz measuring system under rainfall intensities up to 25 mm/hr. Rain attenuation coefficients were also calculated using four raindrop-size distributions, e Marshall-Palmer (M-P), Best, Polyakova-Shifrin (P-S) and Weibull distributions, and using a specific rain attenuation model for prediction methods recommended by ITU-R. Measurements of a terahertz wave taken at 355.2 GHz were compared with our calculations. Results showed that the propagation experiment was in very good agreement with a calculation from a specific attenuation model for use in prediction method recommended by ITU-R.

Multiband Monopole Antenna with Sector-Nested Fractal

A kind of novel multi-frequency monopole antenna with sector-nested fractal is proposed and designed, which is nested with a series of similar circular sector elements. By means of the trapeziform ground plane with the tapered CPW (coplanar waveguide) feeder in the middle, the antenna’s radiation performance is greatly improved. The antennas can synchronously operate in three frequencies, covering the working frequency bands of WLAN/WiMAX, 2.44 GHz/3.5 GHz/5.2 GHz - 5.8 GHz. The pattern and impedance measurements of antenna show a good performance over the WLAN/WiMAX band;it possesses a near omni-directional characteristic and good radiation efficiency. Moreover, the antenna is miniature and its design idea can be easily applied into other types of nested structure, the features of which make the proposed antenna have a promising application in other fields.

Effect of Partial Ground Plane Removal on the Radiation Characteristics of a Microstrip Antenna

This study presents a new, simple method for reducing the back-lobe radiation of a microstrip antenna (MSA) by a partially removed ground plane of the antenna. The effect of the partial ground plane removal in different configurations on the radiation characteristics of a MSA are investigated numerically. The partial ground plane removal reduces the backlobe radiation of the MSA by suppressing the surface wave diffraction from the edges of the antenna ground plane. For further improving the front-to-back (F/B) ratio of the MSA, a new soft-surface configuration consisting of an array of stand-up split ring resonators (SRRs) are placed on a bare dielectric substrate near the two ground plane edges. Compared to the F/B ratio of a conventional MSA with a full ground plane of the same size, an improved F/B ratio of 9.7 dB has been achieved experimentally for our proposed MSA.

Plus Shape Slotted Fractal Antenna for Wireless Applications

Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlines a multiband antenna design based on fractal concepts. Fractal antennas show multiband behavior due to self-similarity in their structure. The plus shaped fractal antenna has been designed on a substrate of dielectric constant €r = 4.4 and thickness 1.6mm. The proposed antenna is characterized by a compact size and it is microstrip feed fractal patch of order 1/3. It is observed that the antenna is radiating at multiple resonant frequencies. The resonant frequency is reduced from 2.2 GHz to 900 MHz after I & II iterations respectively. Thus considerable size reduction of 81.77% & overall bandwidth of 12.92% are achieved. The proposed antenna is simulated using the method of moment based commercial software (IE3D) and it is found that simulated results are in good agreement with the experimental results.

Rain Attenuation at Terahertz

Rain attenuation values were calculated using empirical raindrop-size distributions, which were, Marshall-Palmer (M-P), Best, Polyakova-Shifrin (P-S) and Weibull raindrop-size distributions, and also calculated using a specific rain attenuation model for prediction methods recommended by ITU-R. Measurements of Terahertz wave taken at 313 GHz (0.96 mm) were compared with our calculations. Results showed that the propagation experiment was in very good agreement with a calculation from the specific attenuation model for use in prediction methods by ITU-R.

Hybrid IEEE 802.15.6 Wireless Body Area Networks Interference Mitigation Model for High Mobility Interference Scenarios

The field of Wireless Sensor Networks (WSNs) has revolutionized tremendously in the recent past with its major application in Wireless Body Area Networks (WBANs). This has in the same dimension attracted immense interests from the researchers and technology providers. The operational modality of the WBANs is that a few sensor nodes are placed in or around the body and that they are meant to operate within a limited condition while providing high performance in terms of WBAN life time, high throughput, high data reliability, minimum or no delay and low power consumption. As most of the WBAN operates within the universal Industrial, Scientific and Medical (ISM) Narrow Band (NB) wireless band (2.4 Ghz) frequency band, this has posed a challenge in respect to inter, intra and co-channel interference especially in dense areas and high mobility scenarios. As well the body posture changes dynamically due to these mobility effects. In this paper, we propose a hybrid WBAN interference mitigation model based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Contention Window (CW) approach and User Priority (UP) queues. Using Omnet++ simulation, a comparison to the IEEE 802.15.6 based WBAN protocol is presented under the standing, walking sitting and Lying postural mobility scenarios. The results show that the proposed hybrid model outperforms IEEE 802.15.6 based CSMA/CA protocol in areas of network throughput, bandwidth efficiency and network delay in these mobility postures.

Millimeter-Wave Absorption Properties of Thin Wave Absorber in Free Space with New Porous Carbon Material

In this paper, we focus on PHYTOPOROUS, a porous carbon material made entirely from plant-based ingredients, as a new broadband-wave absorber material that acts in the millimeter wave band. We created prototypes of thin rubber-sheet wave absorbers that contain porous carbon (PHYTOPOROUS) made from rice chaff and soybean hulls, which are both agricultural residue products that are generated in large quantities. We investigated the permittivity and reflectance characteristics of this material using the free-space time-domain method. The thin rubber-sheet wave absorber that contained PHYTOPOROUS made from soybean hulls exhibited a frequency band that was approximately 18 GHz wide and centered at 90 GHz. The return loss for this material was greater than −20 dB. This demonstrates that the material provides nearly constant reflection absorption over a wide frequency band.

Broadband Quasi-Yagi Antenna for WiFi and WiMax Applications

In this paper, we present a broadband quasi-Yagi antenna. Good impedance matching is obtained by using parasitic elements. The antenna has been designed and successfully measured. Experimental results show that the 10 dB return loss bandwidth of this antenna is 50% operating from 2.3 GHz to 3.8 GHz. We obtain very flat gain (around 5 dB) over the entire bandwidth. For the design and optimization of antennas, we use HFSS CAD software from ANSOFT.

Comparison of Indoor Localization Systems Based on Wireless Communications

Localization using a Wireless Sensor Network (WSN) has become a field of interest for researchers in the past years. This information is expected to aid in routing, systems maintenance and health monitoring. For example, many projects aiming to monitor the elderly at home include a personal area network (PAN) which can provide current location of the patient to the medical staff. This article presents an overview of the current trends in this domain. We introduce the mathematical tools used to determine position then we introduce a selection of range-free and range-based proposals. Finally, we provide a comparison of these techniques and suggest possible areas of improvement.

Improving Bandwidth of Yagi-Uda Arrays

A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technology, a novel, proprietary design and optimization methodology, to produce an array with 33.09% fractional impedance bandwidth. This array’s performance is compared to its CFO-optimized Fixed Z0counterpart, and to the performance of a 6-ele- ment Dominating Cone Line Search-optimized array. Both CFO-optimized antennas exhibit better performance than the DCLS array, especially with respect to impedance bandwidth. Although the Yagi-Uda antenna was chosen to illustrate this new approach to antenna design and optimization, the methodology is entirely general and can be applied to any antenna against any set of performance objectives.

Opportunistic Usage of Maritime VHF Band—Deployment Challenges for a New Regulatory Framework

Similarly to other domains, maritime community requests for broadband services have been significantly increasing. Worldwide navigation footprint and the lack of practical alternatives to Satellite Communications (SATCOM) empower VHF band as the natural choice to support most of those demands. Nevertheless, the major challenge for an implementation of maritime broadband VHF services is unquestionably the spectrum availability and management. Eventually, the solution must include spectrum sharing, using a Cognitive Radio (CR) based approach, but unfortunately current regulatory framework and spectrum management regime are not appropriate for such concepts and emerging technologies. To overcome such constraints, it is necessary to address a whole field of regulatory and standardization issues in order to prepare an evolution towards a more flexible and dynamic approach to spectrum management and a transition that would ensure incumbents live operations and legacy systems. The required paradigm change encompasses a new policy definition, an enforcement mechanism implementation and a comprehensive transition plan. The presented analysis pretends to address the regulatory feasibility of a framework change, discusses its evolving process and points some challenges related with practical aspects associated to Quality of Service (QoS) enforcement metrics definition, centering the arguments in maritime VHF band.

Wireless Power Feeding with Strongly Coupled Magnetic Resonance for a Flying Object

Wireless power feeding was examined with strongly coupled magnetic resonance for an object moving in 3-D space. Electric power was transmitted from the ground to an electrically powered toy helicopter in the air. A lightweight receiver resonator was developed using copper foil. High Q of greater than 200 was obtained. One-side impedance matching the transmitter side was proposed to cope with high transmission efficiency and the receiver’s weight reduction. Results show that the efficiency drop near the ground was drastically improved. Moreover, the measured efficiency showed good agreement with theoretical predictions. A fully equipped helicopter of 6.56 g weight was lifted up with source power of about 5 W to an altitude of approximately 10 cm.

A New Algorithm of Mobile Node Localization Based on RSSI

Position mobile node coordinate is a key component to determine the accuracy and efficiency of positioning in wireless sensor networks. Flexible location algorithm admits to adjust the accuracy and time cost of positioning based on the users references. This paper develops a location algorithm named Signal Strengthening Dynamic Value (SSDV) based on the database of RSSI to position the mobile node in terms of the value of beacon nodes RSSI. The proposed algorithm has successfully improved the accuracy of mobile nodes positioning and real-time, and simulation results show high performance in effectiveness of the algorithm.

Effect of Changes in Sea-Surface State on Statistical Characteristics of Sea Clutter with X-Band Radar

We have made observations of X-band radar sea clutter from the sea surface and sea-surface state in the Uraga Suido Traffic Route, which is used by ships entering and leaving Tokyo Bay, and the nearby Daini Kaiho Sea Fortress. We estimated the distributions of reflected amplitudes due to sea clutter using models that assume Weibull, Log-Weibull, Log-normal, and K-distributions. We then compared the results of estimating these distributions with sea-surface state data to investigate the effects of changes in the sea-surface state on the statistical characteristics of sea clutter. As a result, we showed that observed sub-ranges not containing a target conformed better to the Weibull distribution regardless of Significant Wave Height (SWH). Further, sub-ranges conforming to the Log-Weibull or Log-normal distribution in areas contained a target when the SWH was large, and as SWH decreases, sub-ranges conforming to a Log-normal. We also showed that for observed sub-ranges not containing a target, the shape parameter, c, of both Weibull and Log-Weibull distribution correlated with SWH. The correlation between wave period and shape parameters of Weibull and Log-Weibull distribution showed a weak correlation.

An Investigation of Wideband Rectennas for Wireless Energy Harvesting

This paper is focused on a wireless energy harvesting system using a rectifying antenna (rectenna). The proposed device consists of a wideband cross-dipole antenna, a microwave low-pass filter and a doubling rectifying circuit using Shottcky diodes as rectifying elements. Previously, a few of wideband rectennas have been investigated at 1.7 to 2.5 GHz. The originality of this paper is on the new wideband rectenna design which can harvest the ambient radio frequency (RF) power at 1.7 to 2.5 GHz. In this system, a new wideband cross dipole is designed and used to achieve the required bandwidth and duel-polarization. In addition, the voltage doubling rectifying circuit is optimized to achieve the best performance at power density levels 2 which are typical in urban environments. The characteristics of the proposed rectenna over the desired frequency range are investigated, and the integrated rectenna is simulated, made and tested for low input power densities from 5 to 200 μW/cm2. The simulation and measurement results of the rectenna are compared and a good agreement is achieved. The results demonstrate that the maximum rectenna conversion efficiency is nearly 57% around 1.7 GHz and over 20% over the wideband of interest for the incident power density of 120 μW/cm2. It is noted that the impedance matching is one of the main factors affecting the rectenna energy conversion efficiency. This new wideband rectenna has great potential to harvest wireless energy in GSM/3G/4G and ISM 2.4 GHz bands.

3 - 10 GHz Ultra-Wideband Low-Noise Amplifier Using Inductive-Series Peaking Technique with Cascode Common-Source Circuit

The objective of this paper is to investigate a ultra-wideband (UWB) low noise amplifier (LNA) by utilizing a two-stage cascade circuit schematic associated with inductive-series peaking technique, which can improve the bandwidth in the 3-10 GHz microwave monolithic integrated circuit (MMIC). The proposed UWB LNA amplifier was implemented with both co-planer waveguide (CPW) layout and 0.15-μm GaAs D-mode pHEMT technology. Based on those technologies, this proposed UWB LNA with a chip size of 1.5 mm x 1.4 mm, obtained a flatness gain 3-dB bandwidth of 4 - 8 GHz, the constant gain of 4 dB, noise figure lower than 5 dB, and the return loss better than –8.5 dB. Based on our experimental results, the low noise amplifier using the inductive-series peaking technique can obtain a wider bandwidth, low power consumption and high flatness of gain in the 3 - 10 GHz. Finally, the overall LNA characterization exhibits ultra-wide bandwidth and low noise characterization, which illustrates that the proposed UWB LNA has a compact size and favorable RF characteristics. This UWB LNA circuit demonstrated the high RF characterization and could provide for the low noise micro-wave circuit applications.

Energy-Efficient and Coverage-Aware Clustering in Wireless Sensor Networks

Energy efficiency and sensing coverage are essential metrics for enhancing the lifetime and the utilization of wireless sensor networks. Many protocols have been developed to address these issues, among which, clustering is considered a key technique in minimizing the consumed energy. However, few clustering protocols address the sensing coverage metric. This paper proposes a general framework that addresses both metrics for clustering algorithms in wireless sensor networks. The proposed framework is based on applying the principles of Virtual Field Force on each cluster within the network in order to move the sensor nodes towards proper locations that maximize the sensing coverage and minimize the transmitted energy. Two types of virtual forces are used: an attractive force that moves the nodes towards the cluster head in order to reduce the energy used for communication and a repulsive force that moves the overlapping nodes away from each other such that their sensing coverage is maximized. The performance of the proposed mechanism was evaluated by applying it to the well-known LEACH clustering algorithm. The simulation results demonstrate that the proposed mechanism improves the performance of the LEACH protocol considerably in terms of the achieved sensing coverage, and the network lifetime.

Research of Intelligent Transportation System Based on the Internet of Things Frame

According to city public transit problem characteristic, the main body of a paper has been submitted and has worked out one kind of based on the Internet of things frame Intelligent transportation system. That system collects data by vehicle terminal and uploads data to the server through the network and makes data visible to the consumer passing an algorithm in the server. One aspect, the consumer may inquire about public transit vehicle information by Web. On another aspect, the consumer can know public transit vehicle information by station terminal. The experiments have tested that the Intelligent transportation system can offer public transit vehicle information to many consumers with convenient way thereby this system can solve the city mass transit problem.