Antennas and Propagation (AP) Society
The Long Island Chapter of the Antennas and Propagation Society (AP-3) serves LI technical professionals and businesses in the microwave and communications industry, by providing lectures and seminars on antenna, wave propagation and related topics.
For upcoming APS lectures and meetings, please visit the
How Far is the Far Field?
We develop a new formula for determining the Far Field region of a radiator/scatterer. We arrive at this formula by examining the integral representation of the magnetic field scattered by a thin, straight wire. The formula consists of three distinct parts that result from bounding the errors on the amplitude and phase of the free-space Green's function and the error in dropping one of the two terms in the integral representation. It is more general than the existing formula and avoids the pitfall of the distance to the far field going to zero with the characteristic dimension of the object.
Finite Element and Integral Equation Solver
This presentation addresses design considerations for RF Microwave Components, Sub-Systems and Antenna design for large multi-feed antenna systems. Topics covered include co-site interference, system mounting, high-power/thermal design considerations as well as advanced simulation techniques using a full-wave 3D FEM electromagnetic tool.
Equation: Using Wheeler's Methodology
Described is the development of an impedance matching equation, which relates the fractional impedance matching bandwidth, the radiation Q of an antenna, and the maximum permissible VSWR. Highlighted topics include Wheeler’s three fundamental impedance matching equations (early 1950s), the original impedance matching equation (1973), the impedance matching equation (2006) and a special note on triple-tuned impedance matching (2010).
Turbine/Radar System Modeling and Analysis
Accurate modeling of wind turbines and their interaction with defense, weather and air traffic control (ATC) radar systems is a vital component of the wind farm planning and sitting process. Often, the impact of planned wind farms on radars is overlooked until too late, causing significant financial and schedule impacts to projects that get delayed. Many giga-Watts of planned capacity are currently on hold as developers await a thorough analysis of the impact of the intended wind farm on nearby radar systems. Wind farm developers armed with the right software tools are in a position to better understand and plan for this impact.
of Dielectric Resonator Antenna
For many years, dielectric resonators (DRs) have only been used as high-Q elements in microwave circuits until S. A. Long and his collaborators showed that they can also be used as efficient radiators. The studies were motivated by an observation that carrier frequencies of modern wireless systems had gradually progressed upward to the millimeter-wave region, where efficiencies of metallic antennas can be reduced significantly due to the skin effect. In contrast, DR antennas (DRAs) are purely made of dielectric materials with no conductor loss. This feature makes DRAs very suitable for millimeter-wave systems.
Design Considerations for LTE Mobile Applications
Long-Term Evolution (LTE) is one of the 4G mobile communication technologies that are being developed at different frequencies, ranging from 400 MHz to 4 GHz with bandwidths up to 20 MHz. The LTE standard allows Multiple-Input Multiple-Output (MIMO) technology to support high data rate 4G applications. However, modern day handsets with thin and slim shapes are making it difficult to integrate several antennas onto a small Printed Circuit Board (PCB). Computational Electromagnetic Simulations are used for the design, analysis and optimization of the antenna design. Numerical results of the antenna analysis and the channel capacity calculations are presented.
For years, mass deployment of MM wave links are always “round the corner” and finally may be realizable. Technology, regulations, and financial viability have finally converged to reduce most barriers to this reality. An overview of MM Wave communications is provided, including a brief history, current state, and future potential. Particular focus is placed on frequency bands available, today’s technology, applications, alternative solutions comparison and deployment success stories. Specific applications covered include enterprise, carrier and 3G/4G backhaul topologies. Advantages and disadvantages of MM wave technologies are described that include environmental, component, and manufacturability factors. MM wave radio assemblies and associated components are also shown.
RF Sensor Networks
for Improved Detection & Geolocation
Modern radios are more efficient than their predecessors making the signals they transmit harder to detect using traditional approaches. This is especially true in urban areas where the RF environment is crowded, and signal propagation is complex. This presentation explores the use and performance of RF sensor networks for improved detection, identification and geolocation of modern signals using coherent detection, proximity gain, and time-difference of arrival.
Using a Network Analyzer
The presentation discusses the interface requirements between the various components comprising an antenna system. Also covered are the issues related to selecting the equipment required to make antenna measurements.
Physical Layer Principles of WLAN, WiMAX & LTE
Commercial radio technology has reached an inflection point, similar to the transition from analog to digital, when we invented a whole range of digital technology. Now we’re moving from single carrier technologies, where we transmit one digital symbol at a time, to a new paradigm, where we’re potentially transmitting hundreds of symbols simultaneously. The change has been driven by both customer demand for more mobile services and the decreasing cost of the digital signal processing technology required to deploy high bandwidth broadband wireless systems. The technology can now be used in the variety of commercial communications devices: the phones, PDAs, and the laptops on which we have become so dependent.
The technology of choice for this broadband connection is based on a modulation scheme called Orthogonal Frequency Division Multiplexing (OFDM). OFDM offers very good spectral efficiency and is quite tolerant of the ever-present interference in the bands where it is used. One of the key reasons for this is that it transmits hundreds of symbols simultaneously, yet at a low rate per symbol.
Harold A. Wheeler’s
Antenna Design Legacy
Harold A. Wheeler (1903 – 1996) had a distinguished career in the field of radio-electronics. He had a unique talent for reducing complex scientific principles to simple forms that were universally helpful to theoreticians and practitioners. Of his many contributions, those related to antenna design are the subject of this paper. The writer was fortunate to be closely associated with Dr. Wheeler in the development of several antenna systems. The three principal antenna topics in Dr. Wheeler’s experience were impedance matching to a transmission line, electrically small antennas, and planar arrays. This paper concentrates on the first two topics and demonstrates how he developed simple forms that were very helpful and useful to the antenna community. His solutions, although simple in form, were in exact agreement with those based on more rigorous theory.
Adaptive Arrays for
The use of smart antennas, in heterogeneous networks with multi-platform devices, is explored. A universal smart antenna front-end for multi-platform communication devices (including WiFi, WiMax, and cellular with MIMO) that utilizes blind beamforming and a standards-based interface is presented. In addition, sensor applications using very small arrays, made of inexpensive carbon-nanotube antennas, are described. Finally, cross-layer optimization (between the physical and MAC layer) with these smart antennas in heterogeneous networks, including ad-hoc/mesh/sensor networks, is shown to be critical to obtaining the full benefit of smart antennas in these networks.
Microwaves in Medicine
Applications of radio frequency and microwave fields in medicine are not new, but advances in computer modeling and component fabrication, along with decreases in device cost, have resulted in new and old ideas coming to fruition. The non-ionizing nature of this part of the electromagnetic spectrum makes it particularly attractive for diagnostic applications. On the other hand, heating, the well-known interaction with biological tissues, enables some therapeutic uses.
One of the most promising diagnostic methods is in breast cancer detection. This application is based on differences in electrical properties between a healthy and diseased tissue. Two approaches have been explored, a classical tomography, and a wideband radar-based technique.
Several successful therapeutic applications have been developed. They include highly localized, as well as regional heating. Examples of localized heating include angioplasty, cardiac ablation to treat arrhythmias, and esophageal ablation. Regional heating has been achieved with implanted antennas, and surface arrays. The extensive modeling and simultaneous temperature evaluation, and thus control of the heating profile, have made a significant difference in efficiency of these treatments.
Design for Wireless Applications
Several specific electromagnetic design examples for wireless applications are reviewed. These examples include antennas for cellular handsets, RFIDs as well as electromagnetic interference solution concepts. Various characteristics of advanced design methods are then examined. The case is made that multidisciplinary design methods need to be developed and employed for efficient solution of complex problems. At present, multidisciplinary issues encountered at the design of feature-rich products are solved by intense communications between the design groups of interacting disciplines. The design of today’s challenging products demands the same and higher degree of communications between the tools used by interacting disciplines. An electromagnetic and structural design example is used to elucidate the concepts discussed. Additionally, an outline of a framework capable of addressing concurrent optimization of multiple disciplines and of complex products is presented. The seminar ends with a list of proposed problems that need to be solved so that maximum efficiency can be achieved in solving the complex problems of the future.
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Performance of Electrically Small Antennas
Electrically small antennas represent one of the most challenging design problems for the antenna engineer. As electronic components and devices rapidly decrease in size, there is an increasing demand for physically smaller antennas. At some frequencies, the requirement for a physically small antenna does not necessarily translate into a requirement for an electrically small antenna. However, with decreasing physical size at any frequency, the design challenge increases because performance requirements are rarely relaxed. This presentation provides an overview of the theory, challenges and performance trade-offs associated with the design of electrically small antennas. Additionally, several electrically small antenna designs are presented with a specific focus on recent advances made in this field.
The presentation begins with an overview of the basic theory and concepts associated with electrically small antennas. This segment of the presentation provides an understanding of antenna performance limitations in terms of impedance, radiation patterns, bandwidth, efficiency, and quality factor. The presentation continues with a discussion of recent advances in the field of electrically small antenna design. Numerous techniques used to design self-resonant electrically small antennas are discussed. Techniques discussed include dielectric loading, impedance loading, linear loading (increasing wire length), top-loading, folded configurations, Genetic Algorithm optimization, etc. The resonant performance properties of numerous antenna configurations and types are presented and compared. The relationship between the antenna’s performance characteristics and its physical properties are discussed. Issues such as the significance of antenna geometry and current vector alignment in establishing the resonant properties of an antenna are considered. The presentation concludes with a discussion of recent advances in the design of low profile, conformal and integrated device antennas.
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Electrically Small Antenna System
The limitations on bandwidth and efficiency of electrically small antennas are well known. However, those limitations are based on linear circuit theory. In this lecture a radiating system is described where electronic switches are embedded in the radiating structure. The switches operate at a rate significantly higher than the RF carrier frequency and are used to digitally synthesize the radiating current waveform. In this non-linear radiating system both the operating bandwidth and efficiency are not limited by antenna size. The efficiency of this approach is determined by switch characteristics and the synthesis algorithm. This non-linear method offers significant efficiency improvement compared to a passive electrically small antenna of the same size when operating over a multi-octave bandwidth. The theory and fundamental limitations of this approach are discussed. In addition, the design and performance of prototype small antenna systems that operate over multi-octave instantaneous bandwidths up to 120 MHz are described.
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RFID RADAR Technology
for Commodity Goods
Radio Frequency Identification (RFID) technology is an emerging automatic identification and data capture (AIDC) technology that has been overly hyped in the past as the panacea for supply chain automation and high asset visibility. RFID was invented in 1948 before the barcode. It has since captured the imagination of many technology innovators, and soon found its way into many successful applications that can bear its price point. Unfortunately, industry pundits have been advertising RFID as a solution for long standing AIDC visions such as automatic shopping cart inventory and pervasive, perpetual item level inventory in a store. However, the fundamentals of basic physics and economics currently limit the potential of this technology for wide scale deployment as a barcode replacement at the item level.
In this presentation, we will examine the fundamentals of RFID technology and its basic limitations. We will also outline the areas for future research that appear to be promising in their abilities to potentially address growing application demands across vertical markets. For example, both the Military and Wal*Mart recently announced an RFID mandate whereby all of their suppliers will be required to label shipped goods with RFID tags by 2006. Similar mandates are expected from the pharmaceutical industries and as part of the homeland security initiative. These mandates will require fast technological innovations that will provide cost-effective and high-accuracy data capture solutions that require little change to the existing logistical workflow.