ELECTRO-OPTIC ANTENNA ELEMENTS FOR PASSIVE PHASED ARRAY RADAR

Passive phased antenna arrays are utilized in military and civilian radar systems to determine the received signal origination. Phased array placement for optimal reception is challenging due to the required supporting electronic hardware and the associated coaxial cabling that typically accompanies each antenna channel. Low noise amplifiers and frequency conversion hardware add size and complexity, limiting possible positions for phased array placement. Eliminating required phased array electronic subcomponents without sacrificing function would allow placement onto smaller agile platforms, such as unmanned systems and rapid deployment networks. Electro-optic (EO) antenna elements utilize an optical waveguide embedded between the antenna and ground plane that responds to the electric field received by the resonating antenna. Using EO antenna elements removes associated electronic hardware from antenna sites, thus simplifying advanced phased array technology. EO antenna elements modulate received signals directly into the optical domain where the low loss, electromagnetic immunity, low weight, and small size advantages of optical fiber can be utilized for antenna remoting. The combination of optical signals from EO antenna elements in Mach-Zehnder interferometers reduces the number of overall channels needed for a given radar system. The reduction of channels further serves to decrease the size, weight, cost, computation, and power requirements of the radar system. This thesis details the design, fabrication, and characterization of EO phased arrays and prototype EO antenna elements, both as individual antenna elements and in a phased array configuration. Waveguide loss, refractive index, and EO coefficient measurements are made for individual EO antenna elements. Radio Frequency (RF) phase modulation emulating a changing angle of arrival is applied by direct injection to a two-element phased array of EO antenna elements. The system’s optical output is correlated to the array factor for a two-element phased array showing proof-of-concept that EO antenna elements can be used in direction finding applications. The sensitivity of EO antenna elements is analyzed and a new design for EO antenna elements with improved sensitivity is presented. The electric field distribution of a rectangular patch antenna at resonance was found to be useful for driving a push-pull Mach-Zehnder modulator, doubling the EO antenna element sensitivity

The Allen Telescope Array: The First Widefield, Panchromatic, Snapshot Radio Camera for Radio Astronomy and SETI

The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in Northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting surveys of the astrophysical sky and conducting searches for distant technological civilizations. This paper summarizes the design elements of the ATA, the cost savings made possible by the use of COTS components, and the cost/performance trades that eventually enabled this first snapshot radio camera. The fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results will be discussed.Comment: Special Issue of Proceedings of the IEEE: "Advances in Radio Telescopes", Baars,J. Thompson,R., D'Addario, L., eds, 2009, in pres

Antenna Designs Aiming at the Next Generation of Wireless Communication

Millimeter-wave (mm-wave) frequencies have drawn large attention, specically for the fifth generation (5G) of wireless communication, due to their capability to provide high data-rates. However, design and characterization of the antenna system in wireless communication will face new challenges when we move up to higher frequency bands. The small size of the components at higher frequencies will make the integration of the antennas in the system almost inevitable. Therefore, the individual characterization of the antenna can become more challenging compared to the previous generations.This emphasizes the importance of having a reliable, simple and yet meaningful Over-the-Air (OTA) characterization method for the antenna systems. To avoid the complexity of using a variety of propagation environments in the OTA performance characterization, two extreme or edge scenarios for the propagation channels are presented, i.e., the Rich Isotropic Multipath (RIMP) and Random Line-of-Sight (Random-LoS). MIMO efficiency has been defined as a Figure of Merit (FoM), based on the Cumulative Distribution Function (CDF) of the received signal, due to the statistical behavior of the signal in both RIMP and Random-LoS. Considering this approach, we have improved the design of a wideband antenna for wireless application based on MIMO efficiency as the FoM of the OTA characterization in a Random-LoS propagation environment. We have shown that the power imbalance and the polarization orthogonality plays major roles determining the 2-bitstream MIMO performance of the antenna in Random-LoS. In addition, a wideband dual-polarized linear array is designed for an OTA Random-LoS measurement set-up for automotive wireless systems. The next generation of wireless communications is extended throughout multiple narrow frequency bands, varying within 20-70 GHz. Providing an individual antenna system for each of these bands may not be feasible in terms of cost, complexity and available physical space. Therefore, Ultra-Wideband (UWB) antenna arrays, coveringmultiple mm-wave frequency bands represent a versatile candidate for these antenna systems. In addition to having wideband characteristics, these antennas should offer an easy integration capability with the active modules. We present a new design of UWB planar arrays for mm-wave applications. The novelty is to propose planar antenna layouts to provide large bandwidth at mm-wave frequencies, using simplified standard PCB manufacturing techniques. The proposed antennas are based on Tightly Coupled Dipole Arrays (TCDAs) concept with integrated feeding network

Antenna integration for wireless and sensing applications

As integrated circuits become smaller in size, antenna design has become the size limiting factor for RF front ends. The size reduction of an antenna is limited due to tradeoffs between its size and its performance. Thus, combining antenna designs with other system components can reutilize parts of the system and significantly reduce its overall size. The biggest challenge is in minimizing the interference between the antenna and other components so that the radiation performance is not compromised. This is especially true for antenna arrays where the radiation pattern is important. Antenna size reduction is also desired for wireless sensors where the devices need to be unnoticeable to the subjects being monitored. In addition to reducing the interference between components, the environmental effect on the antenna needs to be considered based on sensors' deployment. This dissertation focuses on solving the two challenges: 1) designing compact multi-frequency arrays that maintain directive radiation across their operating bands and 2) developing integrated antennas for sensors that are protected against hazardous environmental conditions. The first part of the dissertation addresses various multi-frequency directive antennas arrays that can be used for base stations, aerospace/satellite applications. A cognitive radio base station antenna that maintains a consistent radiation pattern across the operating frequencies is introduced. This is followed by multi-frequency phased array designs that emphasize light-weight and compactness for aerospace applications. The size and weight of the antenna element is reduced by using paper-based electronics and internal cavity structures. The second part of the dissertation addresses antenna designs for sensor systems such as wireless sensor networks and RFID-based sensors. Solar cell integrated antennas for wireless sensor nodes are introduced to overcome the mechanical weakness posed by conventional monopole designs. This can significantly improve the sturdiness of the sensor from environmental hazards. The dissertation also introduces RFID-based strain sensors as a low-cost solution to massive sensor deployments. With an antenna acting as both the sensing device as well as the communication medium, the cost of an RFID sensor is dramatically reduced. Sensors' strain sensitivities are measured and theoretically derived. Their environmental sensitivities are also investigated to calibrate them for real world applications.Ph.D.Committee Chair: Tentzeris, Emmanouil; Committee Member: Akyildiz, Ian; Committee Member: Allen, Mark; Committee Member: Naishadham, Krishna; Committee Member: Peterson, Andrew; Committee Member: Wang, Yan

Reconfigurable photonic antennas

Sharing the electromagnetic spectrum and the physical space for multiple wireless applications in commercial and military applications has resulted in large and complex integrated solutions. Traditional microwave approaches required to look for other alternatives to overcome the aerodynamics limits of front-end devices, particularly in airborne platforms. The implementation of Microwave Photonics techniques to remote microwave antennas is increasingly finding more and more application in airborne Electromagnetic Support applications. This is not only because optical fibres are excellent substitutes of bulky transmission lines (e.g., coaxial and rectangular waveguide) but also because traditional microwave signal processing techniques can also be implemented using photonic techniques. The aim of this dissertation is to investigate the use of Microwave Photonic technologies and photonic signal processing techniques as a means of improving front-end receivers for wireless platforms, particularly for airborne Electronic Warfare applications. This work focuses in specific on the development of a single shared aperture sensor for Electromagnetic Support applications such as early detection radar and direction finding. The use of photonic signal processing techniques such as polarisation diversity, multiplexing and transversal techniques is proposed to control the radiation characteristics of multifunctional broadband antennas. Major contributions made by this work include the derivation of a flexible and broadband receiving “wireless kiosk” suitable for current and future integrated multiple antenna systems. The design and development of an orthogonal mode transformer that enables the multi-mode operational characteristics of broadband frequency independent two-arm spiral antennas. The implementation of a Photonic 180° hybrid coupler that controls the radiation modes of a multi-mode two-arm spiral antenna. The implementation of a microwave photonic mode transformer using photonic signal processing techniques that substitutes complex and bulky microwave mode transformers such as microwave Butler matrices. In specific, photonic transversal techniques were used to implement 90° photonic hybrid couplers that, combined with 180° photonic hybrid couplers, controlled the radiation patterns and polarisation characteristics of a multifunctional four- arms sinuous antenna

Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance