Chan H. See

Multiple Band-Notched UWB Antenna With Band-Rejected Elements Integrated in the Feed Line

To mitigate potential interferences with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.35 GHz, or 5.725-5.825 GHz bands, four novel band-notched antennas suitable for ultra-wideband (UWB) applications are proposed. These include UWB antennas with a single wide notched band, a single narrow notched band, dual notched bands, and triple notched bands. Each antenna comprises a half-circle shaped patch with an open rectangular slot and a half-circle shaped ground plane. Good band-notched performance is achieved by using high permittivity and low dielectric loss substrate, and inserting quarter-wavelength horizontal/vertical stubs or alternatively embedding quarter-wavelength open-ended slots within the feed line. The results of both simulation and measurement confirm that the gain suppression of the single and multiple band-notched antennas in each desired notched band are over 15 dB and 10 dB , respectively. The radiation pattern of the proposed triple band-notched design is relatively stable across the operating frequency band.

Ultra-Wideband Dual-Polarized Patch Antenna With Four Capacitively Coupled Feeds

A novel dual-polarized patch antenna for ultra-wideband (UWB) applications is presented. The antenna consists of a square patch and four capacitively coupled feeds to enhance the impedance bandwidth. Each feed is formed by a vertical isosceles trapezoidal patch and a horizontal isosceles triangular patch. The four feeds are connected to the microstrip lines that are printed on the bottom layer of the grounded FR4 substrate. Two tapered baluns are utilized to excite the antenna to achieve high isolation between the ports and reduce the cross-polarization levels. In order to increase the antenna gain and reduce the backward radiation, a compact surface mounted cavity is integrated with the antenna. The antenna prototype has achieved an impedance bandwidth of 112% at (|S11 | ≤ -10 dB) whereas the coupling between the two ports is below -28 dB across the operating frequency range. The measured antenna gain varies from 3.91 to 10.2 dBi for port 1 and from 3.38 to 9.21 dBi for port 2, with a 3-dB gain bandwidth of 107%.

An Active Microwave Sensor for Near Field Imaging

Near-field imaging using microwaves in medical applications is of great current interest for its capability and accuracy in identifying features of interest, in comparison with other known screening tools. This paper documents microwave imaging experiments on breast cancer detection, using active antenna tuning to obtain matching over a wide bandwidth. A simple phantom consisting of a plastic container with a low dielectric material emulating fatty tissue and a high dielectric constant object emulating a tumor is scanned between 4 and 8 GHz with a ultra-wideband microstrip antenna. Measurements indicate that this prototype microwave sensor is a good candidate for such imaging applications.

Automatic liquid level indication and control using passive UHF RFID tags

This paper proposes a new perspective to the liquid level monitoring and control technique by deploying energy efficient passive UHF RFID tags as liquid level sensors. The system consists of the pump, storage tank, level sensors (passive tags), RFID tag reader, pump control circuit, alarm circuit, and an indicator circuit. The tags are sealed (air and water tight), programmed with unique level labels using the Alien Reader software(860-868MHZ) and deployed to various levels of a storage tank for level monitoring and control. The mirrored P-shaped tag is designed modelled and deployed for use as the liquid level sensors. The RFID reader is disguised to form a part of the tank cover literarily few inches away from the tags. A variation of the tag readings received is used to infer level information which is communicated via the reader middleware to a computer database for monitoring.

Dual-Band Planar Inverted F-L Antenna Structure for Bluetooth and ZigBee Applications

This chapter will present and analyse a compact and dual frequency inverted L-F antennas for the operating frequency bands to meet the requirement for IEEE 802.11a/b/g, Bluetooth and ZigBee standards; the optimal design providing a compromise between size reduction and attainable bandwidth. The antenna consists of an F-shaped radiator and L-shaped parasitic element with the optimum (minimized) volume of 30 × 30 × 8 mm3, thus making it feasible to be adopted within the portable wireless electronic devices. By controlling the geometry parameters of the radiator, the lower resonant operating band can be tuned to achieve 8% bandwidth. Likewise, by optimising the geometry parameters of the parasitic element, the upper operating frequency band can reach the required 12.2% bandwidth. Both the computed and measured features of the present antenna are in good agreement.

Compact Wideband Printed MIMO/Diversity Monopole Antenna for GSM/UMTS and LTE Applications

Over the last decade, significant research effort has been devoted to enhance the isolation between multiple-input-multiple-output (MIMO) antenna elements. This has led to offer several solutions, which in terms of band calcifications may be categories as follows: narrow band, broadband and dual/triple band. Services that have been covered by the narrow band solutions include Long Term Evolution (LTE) 700–800 MHz, UMTS and WLAN 2.4, 5.2 and 5.8 GHz. Thus, within this chapter, a low profile printed crescent-shaped monopole MIMO diversity antenna for use in smart mobile devices is proposed. The mutual coupling is significantly mitigated by simply printing an I-shaped conductor over the ground place which is symmetrically placed between the two antenna elements. The proposed MIMO antenna exhibits a wideband frequency range from 1.8 to 2.6 GHz, equivalent to bandwidth of 54.5%, while simultaneously achieving an isolation of −14 dB. Moreover, the proposed antenna demonstrates nearly omnidirectional patters, acceptable power gain, good envelope correlation and channel capacity loss.

Link Budget Maximization for a Mobile-Band Subsurface Wireless Sensor in Challenging Water Utility Environments

A subsurface chamber transceiver system and associated propagation channel link budget considerations for an underground wireless sensor system (UWSS) are presented: the application was a sewerage system for a water utility company. The UWSS operates over the GSM850/900, GSM1800/1900, and Universal Mobile Telecommunications System (UMTS) bands in order to operate with the standard public mobile phone system. A novel antenna was developed to minimize path loss from the underground location: a folded loop type, which is small enough to fit conveniently inside a utility manhole access chamber while giving adequate signal strength to link to mobile base stations from such a challenging environment. The electromagnetic performance was simulated and measured in both free space and in a real manhole chamber. An experimental test bed was created to determine the return loss and received signal strength with different transceiver positions below the manhole chamber access cover. Both numerical and experimental results suggested an optimum position of the unit inside the manhole, combining easy access for maintenance with viable received signal strength. This confirmed that the characteristics were adequate for incorporation in a transceiver designed to communicate with mobile base stations from underground. A field trial confirmed the successful operation of the system under severe conditions.

Energy efficient gully pot monitoring system using radio frequency identification (RFID)

Sewer and gully flooding have become major causes of pollution particularly in the residential areas majorly caused by blockages in the water system and drainages. An effective way of avoiding this problem will be by deploying some mechanism to monitor gully pot water level at each point in time and escalating unusual liquid levels to the relevant authorities for prompt action to avoid a flooding occurrence. This paper presents a low cost power efficient gully pot liquid level monitoring technique. Passive RFID tags are deployed and signal variation from the Alien Reader Software are used to effectively estimate the level of liquid in the gully pot. The experimental set up is presented and an expository presentation is made of the passive tag design, modelled and simulated and adopted for same application.

Liquid level monitoring using passive RFID tags

Tank flooding have become major causes of pollution both in residential and industrial areas majorly caused by overflows of water(mostly residential) and volatile poisonous industrial liquids from the storage tanks. An effective way of avoiding this problem will be by deploying some mechanism to monitor liquid level at each point in time and escalating unusual liquid levelsto a pump control circuit or to the relevant authorities for prompt action to avoid a flooding occurrence. This paper presents a low cost power efficient liquid level monitoring technique. Passive RFID tags are designed modelled and deployed, the signal variation from the Alien Reader Software are used to effectively estimate the level of liquid in any surface or underground tank. The experimental set up is presented and an expository presentation is made of the passive tag design, modelled and simulated and adopted for same application.