Abstract: Composite Right/Left Handed (CRLH) Leaky-Wave Antennas (LWAs) are a class of radiating elements characterized by an electronically steerable radiation pattern. The design is comprised of a cascade of CRLH unit-cells populated with varactor diodes. By varying the voltage across the varactor diodes, the antenna can steer its directional beam from broadside to backward and forward end-fire directions. A CRLH Leaky-Wave Antenna for the 2.4 GHz Wi-Fi band is miniaturized by etching a Complementary Split-Ring Resonator (CSRR) underneath each CRLH unit-cell. As opposed to conventional LWA designs, the LWA layout does not require thin interdigital capacitors, significantly reducing the PCB manufacturing constraints required to achieve size reduction. The resulting antenna enables CRLH LWAs to be used not only for wireless access points, but also potentially for mobile devices.

Abstract: A wearable power harvesting system includes a knitted fabric rectenna including an antenna adapted to receive radio-frequency energy within a desired frequency band and a rectifier circuit that converts received radio-frequency energy into a DC current and voltage. A knitted fabric load/storage unit stores DC power from the rectifier circuit. The power harvesting system is adapted to harvest the radio-frequency energy within the desired frequency band, which may include WLAN frequencies such as the standard 2.4 GHz and 5 GHz WLAN standard frequencies.

Abstract: A learning protocol for distributed antenna state selection in directional cognitive small-cell networks is described. Antenna state selection is formulated as a nonstationary multi-armed bandit problem and an effective solution is provided based on the adaptive pursuit method from reinforcement learning. A cognitive small cell testbed, called WARP-TDMAC, provides a useful software-defined radio package to explore the usefulness of compact, electronically reconfigurable antennas in dense small-cell configurations. A practical implementation of the adaptive pursuit method provides a robust distributed antenna state selection protocol for cognitive small-cell networks. Test results confirm that directionality provides significant advantages over omnidirectional transmission which suffers high throughput reduction and complete link outages at above-average jamming or cross-link interference power.

Abstract: A method for selecting the state of a reconfigurable antenna installed at either the receiver or transmitter of a communication system is provided. The proposed method uses online learning algorithm based on the theory of multi-armed bandit to perform antenna state selection. The selection technique utilizes the Post-Processing Signal-to-Noise Ratio (PPSNR) as a reward metric and maximizes the long-term average reward over time. The performance of the learning based selection technique is empirically evaluated using wireless channel data. The data is collected in an indoor environment using a 2×2 MIMO OFDM system employing highly directional metamaterial Reconfigurable Leaky Wave Antennas. The learning based selection technique shows performance improvements in terms of average PPSNR and regret over conventional heuristic policies.

Abstract: Symmetric keys are generated by an algorithm that uses the randomness from the wireless PHY layer to extract the keys. When used with reconfigurable antennas, the algorithm yields longer keys. By using the randomness from the wireless PHY layer, the algorithm solves the issue of secure information leakage to the wireless channel during key establishment phase. The algorithm also omits transmitting anything secure during this phase and prevents any intruder from obtaining information related to the key. This approach can automatically secure the communications over open wireless networks (those without authentication or encryption) or closed wireless networks using other methods of authentication.

Abstract: A method allows reconfigurable multi-element antennas to select the antenna configuration in MIMO, SIMO and MISO communication system. This selection scheme uses spatial correlation, channel reciprocal condition number, delay spread and average Signal to Noise Ratio (SNR) information to select the antenna radiation pattern at the receiver. Using this approach, it is possible to achieve capacity gains in a multi-element reconfigurable antenna system without modifying the data frame of a conventional wireless communication system. The capacity gain achievable with this configuration selection approach is calculated through numerical simulations using reconfigurable circular patch antennas at the receiver of a MIMO system that employs minimum mean square error receivers for channel estimation. Channel capacity and Bit Error Rate (BER) results show the improvement offered relative to a conventional antenna selection technique for reconfigurable MIMO systems.

Abstract: Channel based authentication schemes for intrusion detection that operates at the physical layer are described that apply the capabilities of a pattern reconfigurable antenna for improved performance. Performance gains are achieved by the schemes as a function of the number of antenna modes. The first scheme relies on a channel based fingerprint for differentiating between transmitters whereas another scheme poses the intruder detection problem as a generalized likelihood ratio (GLR) test problem that operates on the channel realizations corresponding to different modes present in a reconfigurable antenna. The benefits of these two schemes over single element antennas are demonstrated. General guidelines are provided on how to choose the different elements of the decision metric in order to realize better performance for physical layer based authentication schemes based on any diversity scheme.

Abstract: Reconfigurable antennas in an ad-hoc network are provided where all nodes employ MIMO/SIMO/MISO communication techniques. Three types of reconfigurable antennas: Reconfigurable Printed Dipole Array (RPDA), Reconfigurable Circular Patch Antenna (RCPA) and Two-Port Reconfigurable CRLH Leaky Wave Antennas are used. The RPDA, RCPA and the CRLH Leaky Wave antennas have a different number of configurations as well as different degrees of pattern diversity between possible configurations. To effectively use these antennas in a network, the performance of centralized and decentralized antenna configuration selection schemes are quantified for reconfiguration at one or both link ends. The sum capacity of the network is used as a metric to quantify the performance of these antennas in measured and simulated network channels.

Abstract: Ultrasonic through metal communication systems are an effective solution for transmitting data across a metal barrier when the structural integrity of the barrier cannot be compromised by physically penetrating it. Substantial improvements in through metal communication systems have been made in recent years, enabling high speed communications of up to 15 Mbps, as well as power transmission up to 30 W across flat walls. A system is described that allows for ultrasonic through metal communication across the wall of a steel tube. Primary challenges of 1) transducer contact, 2) curvature effect on echoes, and 3) alignment are analyzed and addressed through the use of radial mode piezoelectric transducers, transducer “horns”, and Electromagnetic Acoustic Transducers (EMATs). The resulting system shows no significant loss due to changes in alignment, allows for the use of either piezoelectric transducers or EMATs externally, and achieves max data rates of approximately 600 kbps without echo equalization.

Abstract: Composite Right/Left Handed (CRLH) Leaky-Wave Antennas (LWAs) are a class of radiating elements characterized by an electronically steerable radiation pattern. The design is comprised of a cascade of CRLH unit-cells populated with varactor diodes. By varying the voltage across the varactor diodes, the antenna can steer its directional beam from broadside to backward and forward end-fire directions. A CRLH Leaky-Wave Antenna for the 2.4 GHz Wi-Fi band is miniaturized by etching a Complementary Split-Ring Resonator (CSRR) underneath each CRLH unit-cell. As opposed to conventional LWA designs, the LWA layout does not require thin interdigital capacitors, significantly reducing the PCB manufacturing constraints required to achieve size reduction. The resulting antenna enables CRLH LWAs to be used not only for wireless access points, but also potentially for mobile devices.

Abstract: Reconfigurable antennas in an ad-hoc network are provided where all nodes employ MIMO/SIMO/MISO communication techniques. Three types of reconfigurable antennas: Reconfigurable Printed Dipole Array (RPDA), Reconfigurable Circular Patch Antenna (RCPA) and Two-Port Reconfigurable CRLH Leaky Wave Antennas are used. The RPDA, RCPA and the CRLH Leaky Wave antennas have a different number of configurations as well as different degrees of pattern diversity between possible configurations. To effectively use these antennas in a network, the performance of centralized and decentralized antenna configuration selection schemes are quantified for reconfiguration at one or both link ends. The sum capacity of the network is used as a metric to quantify the performance of these antennas in measured and simulated network channels.

Abstract: Channel based authentication schemes for intrusion detection that operates at the physical layer are described that apply the capabilities of a pattern re-configurable antenna for improved performance. Performance gains are achieved by the schemes as a function of the number of antenna modes. The first scheme relies on a channel based fingerprint for differentiating between transmitters whereas another scheme poses the intruder detection problem as a generalized likelihood ratio (GLR) test problem that operates on the channel realizations corresponding to different modes present in a reconfigurable antenna. The benefits of these two schemes over single element antennas are demonstrated. General guidelines are provided on how to choose the different elements of the decision metric in order to realize better performance for physical layer based authentication schemes based on any diversity scheme.

Abstract: A real-time capable, protocol-aware, reactive jammer using GNU Radio and the USRP N210 software-defined radio (SDR) platform detects in-flight packets of known wireless standards and reacts to jam them—within 80 ns of detecting the signal. A reactive jamming device is achieved using low-cost, readily available hardware. The real-time reactive jamming device includes a real-time signal detector that detects an event in received packets in the wireless network, a reactive jamming device that sends a triggering signal when the event is detected, and a jamming generator responsive to the triggering signal to generate a jamming signal that has a user-defined delay so as to enable jamming of specific locations in received packets in the wireless network. The effects of three types of jamming on WiFi (802.11g) and mobile WiMAX (802.16e) networks are demonstrated and jamming performances are quantified by measuring the network throughput using the iperf software tool.

Abstract: A real-time capable, protocol-aware, reactive jammer using GNU Radio and the USRP N210 software-defined radio (SDR) platform detects in-flight packets of known wireless standards and reacts to jam them—within 80 ns of detecting the signal. A reactive jamming device is achieved using low-cost, readily available hardware. The real-time reactive jamming device includes a real-time signal detector that detects an event in received packets in the wireless network, a reactive jamming device that sends a triggering signal when the event is detected, and a jamming generator responsive to the triggering signal to generate a jamming signal that has a user-defined delay so as to enable jamming of specific locations in received packets in the wireless network. The effects of three types of jamming on WiFi (802.11g) and mobile WiMAX (802.16e) networks are demonstrated and jamming performances are quantified by measuring the network throughput using the iperf software tool.

Abstract: An optically transparent conformal polymer antenna and a method for producing the antenna from optically transparent conductive polymers. The method includes selecting an antenna design; providing an optically transparent conductive polymer material capable of being printed using an ink-jet printer device; and printing layers of the polymer in the desired antenna design pattern onto a substrate. The surface tension of the polymer solution is adjusted to allow the material to pass through a printer head for printing on a flexible substrate. The material is modified to have a higher conductivity than regular conductive polymer materials so that a suitable antenna may be formed.

Abstract: A wearable power harvesting system includes a knitted fabric rectenna including an antenna adapted to receive radio-frequency energy within a desired frequency band and a rectifier circuit that converts received radio-frequency energy into a DC current and voltage. A knitted fabric load/storage unit stores DC power from the rectifier circuit. The power harvesting system is adapted to harvest the radio-frequency energy within the desired frequency band, which may include WLAN frequencies such as the standard 2.4 GHz and 5 GHz WLAN standard frequencies.

Abstract: A method for selecting the state of a reconfigurable antenna installed at either the receiver or transmitter of a communication system is provided. The proposed method uses online learning algorithm based on the theory of multi-armed bandit to perform antenna state selection. The selection technique utilizes the Post-Processing Signal-to-Noise Ratio (PPSNR) as a reward metric and maximizes the long-term average reward over time. The performance of the learning based selection technique is empirically evaluated using wireless channel data. The data is collected in an indoor environment using a 2×2 MIMO OFDM system employing highly directional metamaterial Reconfigurable Leaky Wave Antennas. The learning based selection technique shows performance improvements in terms of average PPSNR and regret over conventional heuristic policies.

Abstract: By using reconfigurable antenna based pattern diversity, an optimal channel can be realized in order to maximize the distance between two subspaces, thereby increasing sum-rate. The inventors show the benefits of pattern reconfigurability using real-world channels, measured in a MIMO-OFDM interference network. The results are quantified with two different reconfigurable antenna architectures. An additional 47% gain in choral distance and 45% gain in sum capacity were achieved by exploiting pattern diversity with IA. Due to optimal channel selection, the performance of IA can also be improved in a low SNR regime.

Abstract: Knitting machines are used to intermesh conductive yarns into loops resulting in knitted fabrics. The knitting machine is adapted to import different types of yarns (conductive and non-conductive) directly into the knit structure. Combining conductive yarns and knitting systems allows for integration of electrical or mechanical component designs into existing clothing fabrication processes, avoiding current limitations of attaching or gluing conductive fabrics or other components over various materials. Starting with a planar design of an antenna, RFID tag, or some other electronic structure, the layout is converted into a CAD knitting program including a grid representing stitches. The CAD specifications of the final design/product are exported to the knitting machines so that the knitting machine may make conductive fabrics in accordance with the CAD specifications.

Abstract: A planar reconfigurable antenna that is capable of generating omnidirectional and directional radiation patterns over a wide frequency band or over multiple frequency bands includes a substrate, one or more pairs of conductive elements on at least one side of the substrate, a common RF feed point, and respective switches that selectively connects one or all of the conductive elements to the common RF feed point. An omni-directional radiation pattern is generated when all of the conductive elements are connected to the common RF feed point, while a directional radiation pattern is generated when only a pair of conductive elements on opposite sides of the substrate are connected to the common RF feed point. In the directional radiation mode, the conductive elements that are not connected to the common RF feed point act as a reflector for other conductive elements that are connected to the common RF feed point.