C. H. See

Wideband Printed MIMO/Diversity Monopole Antenna for WiFi/WiMAX Applications

A novel printed diversity monopole antenna is presented for WiFi/WiMAX applications. The antenna comprises two crescent shaped radiators placed symmetrically with respect to a defected ground plane and a neutralization lines is connected between them to achieve good impedance matching and low mutual coupling. Theoretical and experimental characteristics are illustrated for this antenna, which achieves an impedance bandwidth of 54.5% (over 2.4-4.2 GHz), with a reflection coefficient <;-10 dB and mutual coupling <;-17 dB. An acceptable agreement is obtained for the computed and measured gain, radiation patterns, envelope correlation coefficient, and channel capacity loss. These characteristics demonstrate that the proposed antenna is an attractive candidate for multiple-input multiple-output portable or mobile devices.

A Low-Profile Ultra-Wideband Modified Planar Inverted-F Antenna

A miniaturized modified planar inverted-F antenna (PIFA) is presented and experimentally studied. This antenna consists of a planar rectangular monopole top-loaded with a rectangular patch attached to two rectangular plates, one shorted to the ground and the other suspended, both placed at the optimum distance on each side of the planar monopole. The fabricated antenna prototype had a measured impedance bandwidth of 125%, covering 3 to 13 GHz for reflection coefficient better than -10 dB. The radiator size was 20×10×7.5 mm3, making it electrically small over most of the band and suitable for incorporation in mobile devices. The radiation patterns and gains of this antenna have been cross-validated numerically and experimentally and confirm that this antenna has adequate characteristics for short range ultra-wideband wireless applications.

Design and Analysis of Planar Ultra-Wideband Antenna with Dual Band-Notched Function

A novel planar ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed. The antenna is fabricated on a printed circuit board (PCB), having a circular monopole and arc-shaped parasitic strips on one side and a ground plane with a slot aperture on the other side. Two narrow bands at 5.15-5.35 GHz and 5.725-5.825 GHz are notched by using two arc-shaped parasitic strips on the same layer of the radiator. Compared with other band-notched UWB antennas, the proposed antenna exhibits the advantages of simple structure, compact size, simple control of each notched frequency band using separate parasitic strips, and good performance. Surface current distributions and equivalent circuit model are applied to analyze the operating principle of the proposed antenna. To validate the concept, a prototype is fabricated and tested. Both simulated and measured results confirm that the proposed antenna achieves a wide bandwidth from 3.1 GHz to 10.6 GHz with two narrow bands notched successfully. The results of VSWR, radiation patterns and gain response are shown and discussed in detail. The antenna enables the independent control of the notched frequency bands, and the proposed method can be extended for designing planar UWB antennas with multiple band-notched characteristics and reconfigurable notched frequency.

Dual-Frequency Planar Inverted F-L-Antenna (PIFLA) for WLAN and Short Range Communication Systems

The design and analysis is presented of a low profile and dual- frequency inverted L-F antenna for WLAN and short range wireless communications, providing a compromise between size reduction and attainable bandwidth. The optimum (minimized) volume of 30times30times8 mm of the proposed antenna gives 8% bandwidth at lower resonant mode of 2400 MHz, while at the higher resonant mode of 5500 MHz a bandwidth of 12.2% is obtained. Both the simulated and measured characteristics of the proposed antenna are shown.

A Crescent-Shaped Multiband Planar Monopole Antenna for Mobile Wireless Applications

A planar multiband monopole antenna is presented for mobile wireless applications. The antenna is constructed from a crescent-shaped radiator patch, microstrip feed line, and defected ground structure (DGS). Theoretical and experimental characteristics are presented for this antenna, which achieves an impedance bandwidth of 58.3% (over 1.7-3.1 GHz), at a reflection coefficient |S11| < -10 dB and has an average gain of 1.75 dBi.

A Low Power Wireless Sensor Network for Gully Pot Monitoring in Urban Catchments

Sewer and gully blockages are the main cause of residential sewer flooding in the U.K. A low-cost and power efficient wireless sensor mesh networking communication system has been designed, developed and implemented to provide adequate warning on potential blockage incidents to prevent sewer failure. By monitoring the water level of the gully pot at each residential property, the water company will be proactively informed of the best course of actions to eliminate the causal problem, i.e., blockage and leakage within the sewer infrastructure. Hence, the number of residential sewer flooding and pollution incidents can be reduced. The prototype system consists of eight Zigbee based wireless sensor nodes and a GPRS enabled data gatherer. Each Zigbee sensor node comprises of a radio transceiver, a data acquisition board and an acoustic sensor probe. Field trials were carried out in an outdoor scenario to cross-validate the theoretical and practical performance of the prototype system. The results in terms of durability of sensors, sensor nodes and gateways and reliability of communication under real operational conditions and within a typical inner city urban environment are discussed. The problems encountered and solutions to tackle these problems were addressed.

A Planar Inverted-F-L Antenna (PIFLA) With a Rectangular Feeding Plate for Lower-Band UWB Applications

A planar inverted-F-L antenna (PIFLA) with a broadband rectangular feeding structure is proposed for lower-band ultrawideband (UWB) applications. This antenna is constructed from a driven F-shaped element and a parasitic L-shaped element. Both patches are inverted and aligned face to face over a finite ground plane; the optimized dimensions of this antenna are 30 × 15 × 4 mm3. The realized antenna achieves a gain between 2.5 and 4.7 dBi over a 66.6% impedance bandwidth (on the interval 2.85.6 GHz) for |S11| ¿ -10 dB. The radiation patterns, antenna efficiency, and antenna group delay are also measured and discussed.

Miniaturized Tapered Slot Antenna With Signal Rejection in 5–6-GHz Band Using a Balun

A miniaturized elliptically tapered slot antenna fed by a novel balun is proposed for directional ultrawideband (UWB) applications. The feeding configuration consists of a stepped microstrip line and a folded slotline connected with a circular slot. An arc-shaped parasitic strip is printed inside the circular slot. This design achieves the minimization of the physical size and the capability of signal rejection at 5-6 GHz with significant gain suppression of 15 dB. Both simulated and measured results confirm the advantage of the design in reducing the size of the antenna while maintaining the UWB performance with band-notched function.

Wireless sensor transmission range measurement within the ground level

The maximum transmission range of crossbow wireless sensors are considered and discussed for sensor to sensor on ground level communication, and sensor on ground level to base station on lamppost. Two different crossbow wireless sensors kits operated at 900 MHz and 2400 MHz bands were used. Both indoor and outdoor sensor to sensor communication ranges were performed for one and five different types of environments respectively. The performance of the crossbow mote with four different types of antennas, in term of transmission range was considered. Several measurement results for fixed power transmission of the two operated frequencies were recorded for comparisons.

A Zigbee based wireless sensor network for sewerage monitoring

Blockages in sewers are major causes of both sewer flooding and pollution. Water companies which fail to tackle this problem face hefty fines and high operational costs if they unsuccessful to provide a practical solution to prevent flooding. As a result, the detection of sewer condition is routinely required to inform on the best course of action to eliminate this critical problem. This paper presents a novel low cost wireless sensor technology to detect blockages proactively, and feed these event data back to a central control room. The practical deployment of the proposed WSN in an urban area will be demonstrated. In addition, the challenges of this technology in a field trial and the recorded data in terms of the sensor and communication reliability will be addressed.