Showing papers on "Antenna (radio) published in 1997"

Application of antenna arrays to mobile communications. II. Beam-forming and direction-of-arrival considerations

Abstract: Array processing involves manipulation of signals induced on various antenna elements. Its capabilities of steering nulls to reduce cochannel interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiating sources, make it attractive to a mobile communications system designer. Array processing is expected to play an important role in fulfilling the increased demands of various mobile communications services. Part I of this paper showed how an array could be utilized in different configurations to improve the performance of mobile communications systems, with references to various studies where feasibility of apt array system for mobile communications is considered. This paper provides a comprehensive and detailed treatment of different beam-forming schemes, adaptive algorithms to adjust the required weighting on antennas, direction-of-arrival estimation methods-including their performance comparison-and effects of errors on the performance of an array system, as well as schemes to alleviate them. This paper brings together almost all aspects of array signal processing.

Space-time processing for wireless communications

Abstract: This paper reviews space-time signal processing in mobile wireless communications. Space-time processing refers to the signal processing performed in the spatial and temporal domain on signals received at or transmitted from an antenna array, in order to improve performance of wireless networks. We focus on antenna arrays deployed at the base stations since such applications are of current practical interest.

Spatio-temporal processing for communication

Abstract: A space-time signal processing system with advantageously reduced complexity. The system may take advantage of multiple transmitter antenna elements and/or multiple receiver antenna elements, or multiple polarizations of a single transmitter antenna element and/or single receiver antenna element. The system is not restricted to wireless contexts and may exploit any channel having multiple inputs or multiple outputs and certain other characteristics. Multi-path effects in a transmission medium cause a multiplicative increase in capacity.

Method of manufacturing an enclosed transceiver

Abstract: The present invention teaches a method of manufacturing an enclosed transceiver, such as a radio frequency identification (“RFID”) tag. Structurally, in one embodiment, the tag comprises an integrated circuit (IC) chip, and an RF antenna mounted on a thin film substrate powered by a thin film battery. A variety of antenna geometries are compatible with the above tag construction. These include monopole antennas, dipole antennas, dual dipole antennas, a combination of dipole and loop antennas. Further, in another embodiment, the antennas are positioned either within the plane of the thin film battery or superjacent to the thin film battery.

Article tracking system

Abstract: System for tracking mobile tags. Cell controllers with multiple antenna modules generate a carrier signal which is received by the tags. Tags shift the frequency of the carrier signal, modulate an identification code onto it, and transmit the resulting tag signal at randomized intervals. The antennas receive and process the response, and determine the presence of the tags by proximity and triangulation. Distance of a tag from an antenna is calculated by measuring the round trip signal time. The cell controllers send data from the antenna to a host computer. The host computer collects the data and resolves them into positional estimates. Data are archived in a data warehouse, such as an SQL Server.

Optical antenna: Towards a unity efficiency near-field optical probe

Abstract: We demonstrate that an antenna can be used to realize a near-field optical probe that combines spatial resolution well below the diffraction limit with transmission efficiency approaching unity. The probe consists of a planar bow-tie antenna with an open-circuited gap at its apex. We present proof-of-principle measurements using microwave radiation and discuss scaling the antenna to the visible optical spectrum.

System and method for equalizing the delay time for transmission paths in a distributed antenna network

Abstract: A communication system and method are provided for equalizing delay of transmission paths in a distributed antenna network. The distributed antenna network includes a plurality of remote antenna units, a central unit or a base station connected to the remote antenna units by transmission media, where each connection between the base station and one of the remote antenna units forms a separate transmission path having an associated delay time, a delay detector for determining the associated delay time of the separate transmission paths for each of the remote antenna units, and a delay compensator for adjusting the associated delay times in response to the delay detectors so that all of the associated delay times are substantially equalized. The system and method allow the delay parameters for the entire network to be set upon installation and then to be periodically updated without physical intervention by an operator. The detection and compensation allow for equalization of delay time differences that could not otherwise be compensated in the base stations of mobile stations of conventional systems and methods. Furthermore, the equalization synchronizes the bursts so that air frame timing between cells served by the remote antenna units is enhanced and the hand-off performance therebetween is improved.

Low-profile enhanced-bandwidth PIFA antennas for wireless communications packaging

Abstract: The development of small integrated antennas plays a significant role in the progress of the rapidly expanding military and commercial communications applications. The recent advances in RF and microwave high-density circuit packaging technologies in multifunction wireless communications systems have called for the parallel development of compact and efficient antennas that can be used over a wide frequency range. This paper addresses the development and characterization of several low-profile and integrated antennas with enhanced bandwidth for wireless communications systems. The new radiators are developed by adding parasitic elements or tuning devices to a familiar integrated antenna-the planar inverted F antenna (PIFA). Simulations based upon the finite-difference time-domain (FDTD) method and method of moments (MoM) are used to model the performance of the antennas. Comparisons with measured results on fabricated antenna structures are provided for simulations validation.

A high data rate communications network employing an adaptive sectored antenna

Abstract: A high data rate communication system (12) that employs an adaptive sectored antenna (46) is disclosed. The high data rate communication system (12) includes an antenna subsystem (28) for receiving and transmitting data. The antenna subsystem (28) is adapted to be spatially steered. A radio frequency transceiver (32) that is coupled to the antenna subsystem (28) and that selectively generates a bit error rate (BER) signal (206) and a receive signal strength indication (RSSI) signal (210) based upon a received antenna training sequence is also provided. The system (12) also includes a beam steering state machine (200) that is coupled to the radio frequency transceiver (32) and that selectively generates a BER_PASS signal (207) and an RSSI_PASS signal (209) based upon whether the BER signal (206) is in a first logical relationship with a predetermined BER signal and the RSSI signal (210) is in a second logical relationship with a predetermined RSSI signal. An antenna controller (38) is coupled to the antenna subsystem (28) and the beam steering state machine (200) and selectively generates antenna control signals (220) to spatially steer the antenna subsystem (28) based upon the BER_PASS signal (207) and the RSSI_PASS signal (209).

Intravascular magnetic resonance imaging using a loopless catheter antenna.

Abstract: Recently, intravascular catheter probes have been developed to increase signal-to-noise ratio (SNR) for MR imaging of blood vessels. Miniaturization of these catheter probes without degrading their performances is very critical in imaging small vessels such as coronary arteries. Catheter coils have a loop incorporated in their structure and have limitations in physical dimensions and electromagnetic properties. The use of a loopless intravascular catheter antenna is proposed to overcome these problems. The catheter antenna is essentially a dipole, which makes a very thin diameter possible, and its electronic circuitry can be placed outside the blood vessels without performance degradation. The theoretical foundation for the design and operation of the catheter antenna is presented. Several catheter antennae, as small as 1.5 French, were constructed and tested on phantoms and rabbits with great success. The catheter antenna has a simple structure and is easy to design, implement, and operate.

Compact radio frequency transmitting and receiving antenna and control device employing same

Abstract: A radio frequency antenna for use with a wall mounted transmitter and/or receiver for receiving and/or transmitting signals adapted to control a control device and/or indicate status of the control device. The antenna includes an insulating substrate sized to fit within an area defined by a faceplate sized to cover an outwardly facing opening of an electrical wallbox. Conductors are disposed on both sides of the substrate forming a capacitive component. At least one of the conductors is adapted to radiate radio frequency energy into the environment. The one conductor is electrically coupled to the other conductor, and the one conductor has a pattern such that the conductor is absent in areas so as to provide the antenna with an inductive component. The at least one conductor further provides a connection to the transmitter and/or receiver. The antenna provides an antenna near-field which is substantially at the edges of the substrate and which provides insubstantial electromagnetic field coupling to an electronic circuit disposed adjacent the antenna connected to the antenna and further provides a radiated field substantially isotropic in the antenna far-field.

Stacked-carrier discrete multiple tone communication technology and combinations with code nulling, interference cancellation, retrodirective communication and adaptive antenna arrays

Abstract: A "stacked-carrier" spread spectrum communication system based on frequency domain spreading that multiplies a time-domain representation of a baseband signal by a set of superimposed, or stacked, complex sinusoid carrier waves. In a preferred embodiment, the spreading energizes the bins of a large fast Fourier transform (FFT). This provides a considerable savings in computational complexity for moderate output FFT sizes. Point-to-multipoint and multipoint-to-multipoint (nodeless) network topologies are possible. A code-nulling method is included for interference cancellation and enhanced signal separation by exploiting the spectral diversity of the various sources. The basic system may be extended to include multi-element antenna array nulling methods also for interference cancellation and enhanced signal separation using spatial separation. Such methods permit directive and retrodirective transmission systems that adapt or can be adapted to the radio environment. Such systems are compatible with bandwidth-on-demand and higher-order modulation formats and use advanced (maximum-SINR) despreader adaptation algorithms.

Enhanced range transponder system

Abstract: An identification and telemetry system including an interrogator ( 1 ) containing an interrogator antenna ( 2 ) for generating at an interrogation frequency, an interrogtion signal. The interrogation signal is adapted to excite over an electromagnetic coupling path (M 1 ) at least one coded label ( 3 ) containing a label antenna ( 4 ) and a label microcircuit ( 5 ). The coded label is adapted to extract energy from the label antenna and to generate a label reply signal. The label reply signal is adapted to be conveyed to a label reply antenna and, via an electromagnetic coupling path, to a receiver in the interrogator. The label antenna is placed in proximity to a further antenna ( 6 ) being a parasitic antenna coupled electromagnetically (M 2 , M 3 ) with the interrogator antenna and with the label antenna so as to enhance transfer of power between the interrogator and the coded label.

Communication system using geographic position data

Abstract: A wireless communication system employs directive antenna arrays and knowledge of position of users to form narrow antenna beams to and from desired users and away from undesired users to reduce co-channel interference. By reducing co-channel interference coming from different directions, spatial filtering with antenna arrays improves the call capacity of the system. A space division multiple access (SDMA) system allocates a narrow antenna beam pattern to each user in the system so that each user has its own communication channel free from co-channel interference. The position of the users is determined using geo-location techniques. Geo-location can be derived via triangulation between cellular base stations or via a global positioning system (GPS) receiver.

Analysis of radome-enclosed antennas

Abstract: This book and software package provides the analytical tools needed to evaluate and predict the effects of a radome on an enclosed antenna. It features an overview of radome wall concepts and materials, and presents ray trace approaches to achieve solution using a PC. The interactive software allows the user to compute antenna patterns and boresight error of gimbaled radar antennas an a multilayer radome. System requirements: IBM-compatible 386 or higher (Pentium recommended) with a maths coprocessor; 4MB RAM; Epson-compatible printer to output data.

Design of Yagi-Uda antennas using genetic algorithms

Abstract: A method of using genetic algorithms to optimize the element spacing and lengths of Yagi-Uda antennas is presented. A method of moments code, NEC2, performs the task of evaluating each of the antenna designs generated by the genetic algorithm (GA) during the optimization process. To illustrate the capabilities of the method, the length and spacing of several Yagi-Uda antennas are optimized for various performance characteristics. The results are compared to published results from other optimization techniques and to well-designed equally spaced arrays.

Performance of radial-basis function networks for direction of arrival estimation with antenna arrays

Abstract: The problem of direction of arrival (DOA) estimation of mobile users using linear antenna arrays is addressed. To reduce the computational complexity of superresolution algorithms, e.g. multiple signal classification (MUSIC), the DOA problem is approached as a mapping which can be modeled using a suitable artificial neural network trained with input output pairs. This paper discusses the application of a three-layer radial-basis function neural network (RBFNN), which can learn multiple source-direction findings of a six-element array. The network weights are modified using the normalized cumulative delta rule. The performance of this network is compared to that of the MUSIC algorithm for both uncorrelated and correlated signals. It is also shown that the RBFNN substantially reduced the CPU time for the DOA estimation computations.

Self-cancelling full-duplex RF communication system

Abstract: A method is presented herein whereby both transceivers of a full-duplex RF communications system can use the same spectrum at the same time. Self-interference is cancelled using a combination of antenna placement, analog RF suppression, and digital adaptive filtering. The details of this self-cancelling technique are presented.

Contact/contactless data transaction card

Abstract: A data transaction device having contact and contactless modes of operation, comprises a semiconductor device for operating in contact and contactless modes in accordance with a respective contact or contactless data communications protocol. A contact field includes contacts fixedly connected to the semiconductor device for allowing data transmission between the contacts and the semiconductor device in accordance with the contact data communications protocol, whilst a coil antenna allows contactless data transmission between the coil antenna and the semiconductor device, in accordance with the contactless data communications protocol. An antenna interface coupled to the coil antenna, to the semiconductor device and to at least some of the contacts in the contact field is responsive to an electromagnetic field across the coil antenna for effecting contactless data transmission.

Spectrally efficient high capacity wireless communication systems with spatio-temporal processing

Abstract: A wireless system comprising a network of base stations (1) for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to the remote terminals using a plurality of channels including a plurality of antenna elements (19) at each base station for receiving uplink signals, a plurality of antenna elements (18) at each base station for transmitting downlink signals, a signal processor (13) at each base station connected to the receiving antenna elements (19) and to the transmitting antenna elements (18) for determining spatio-temporal multiplexing and demultiplexing functions for each remote antenna for each channel, and a multiple base station network controller for optimizing network performance, whereby communication between the base stations and the remote terminals in each channel can occur simultaneously.

Combined structure of a helical antenna and a dielectric plate

Abstract: The invention relates to a particular structure of high-frequency antenna, which comprises a support element (1) provided with a cylindrical coil conductor which forms a helix (2) On the support element (1) there is formed, for example by means of a conductive coating, the electrical parts of the antenna, such as the attachment points (3b) for the helix and for other parts, such as feeder lines (4), radiators (5) or impedance matching devices By varying the number and size of the helices (2), the number and form of the feeder lines (4) and radiators (5) and the quality of any impedance matching devices, it is possible without difficulty to obtain a very wide choice of different antenna structures The feeder lines and radiators extend, at least in part, within the helix

Arrangement for transmitting and receiving radio frequency signal at two frequency bands

Abstract: The present invention relates to an arrangement for transmitting a radio-frequency signal at two different frequency bands and for receiving at two different frequency bands. The arrangement can be applied for instance to a transceiver of a radio communications system operating at two different frequency bands, or to a transceiver meant to be used in connection with two different radio communications systems. One of the ideas of the invention is that one and the same filter (72), belonging to the RF front end of the antenna circuit, is used for filtering interference from at least two signals located at different frequency bands, in which case the number of filters (72, 75) can be reduced. By means of the solution suggested in the invention, also the number of controllable switches (73) provided on the signal path of the RF front end can be minimized.

Method and apparatus for data transmission using multiple transmit antennas

Abstract: A method and apparatus for increasing the data rate and providing antenna diversity using multiple transmit antennas is disclosed. A set of bits of a digital signal are used to generate a codeword. Codewords are provided according to a channel code. Delay elements may be provided in antenna output channels, or with suitable code construction delay may be omitted. n signals represent n symbols of a codeword are transmitted with n different transmit antennas. At the receiver MLSE or other decoding is used to decode the noisy received sequence. The parallel transmission and channel coding enables an increase the data rate over previous techniques, and recovery even under fading conditions. The channel coding may be concatenated with error correction codes under appropriate conditions.

Dielectric rod antenna

Abstract: A dielectric rod antenna has a dielectric rod and a waveguide which receives one end of the dielectric rod to excite the dielectric rod. The dielectric rod is divided along its length into at least two sections including a hollow tubular dielectric sleeve and a dielectric internal rod telescopically received and secured in the hollow of the dielectric sleeve. One end of the dielectric internal rod makes a releasable-fit engagement with the adjacent end of the dielectric sleeve so that the overall length of the antenna can be fixed against change during the use. The overall radius and the hollow radius of the dielectric sleeve and the overall radius of the dielectric internal rod are determined such that the propagation constant in the dielectric sleeve and the propagation constant in the dielectric internal rod are equalized to each other. The end of the dielectric internal rod adjacent to the dielectric sleeve is tapered so as to converge towards the end extremity.

Plasma processing system

Abstract: A plasma processing system capable of carrying out a uniform processing is provided. According to the present invention, a substantially annular high-frequency antenna 156 of a predetermined number of turns, e.g., 1 turn, is provided in an opening 102b via a first shielding member 160 and a dielectric member 158. The capacitance of a variable capacitor 172 connected to ground is adjusted so that series resonance occurs at the mid point of the high-frequency antenna 156. With this construction, it is possible to form a desired electric field in a plasma producing space to produce a high-density plasma. In addition, a feeding member 126 is formed so that the substantially vertical cross-section thereof has a profile expressed by an exponential function r=f(L). Therefore, it is possible to supply a high-frequency power to an upper electrode without causing the electric breakdown and the damping of the high-frequency power.

"IF" bandstacked low noise block converter combined with diplexer

Abstract: An arrangement is provided for combining the video and audio signals from a satellite antenna with other auxiliary input signals producing a frequency stacked band arrangement for transmission by a single cable to a satellite receiver or TV monitor located within a home or structure. Multiple TV input signals from the satellite antenna are processed and separated into intermediate frequency bands which are then combined in a diplexer with one or more auxiliary input frequency bands. The output of the diplexer is connected directly to the signal output terminal at the antenna. All components for performing this combining process are included within the sealed housing of the LNB provided at the satellite antenna. Improved band isolation and reduced noise and interference are produced by the novel arrangement.

Feeder link antenna

Abstract: A steerable feeder link antenna is formed of a steerable reflector and a stationary feed horn assembly. A novel feed horn assembly allows dual mode transmit and receive functions for circularly polarized microwaves. The feed horn assembly includes a four arm turnstile junction coupled to a feed horn through the feed horn's side wall to couple transmit frequencies and an axially coupled transmission line for the receive frequencies. Each turnstile junction arm incorporates chokes for the receive frequencies. The transmission line's cut off frequency is above the transmit frequency to prevent transmit signals from interfering with receive signal receivers.

Antenna and method for receiving or transmitting radiation through a dielectric material

Abstract: A low profile, receiving and/or transmitting antenna is adapted to be mounted onto an interior portion of a building or other structure to receive or transmit radiation through a first dielectric material, such as a window, associated with the building or other structure. The antenna includes a receiving/transmitting horn filled with a second dielectric material and a surface for mounting the antenna to the first dielectric material so that the horn is disposed at a particular angle with respect to a surface of the first dielectric material. A matching layer may be disposed between the first dielectric material and the second dielectric material to provide for a reflectionless match between the first and second dielectric materials.

An SBR/image approach for radio wave propagation in indoor environments with metallic furniture

Abstract: In this paper, we propose a deterministic approach to model the radio wave propagation channels in complex indoor environments. This technique applies the modified shooting-and-bouncing-ray (SBR) method to find the equivalent sources (images) for each launched ray tube. In addition, the first-order wedge diffraction from furniture is included and the diffracted rays also can be attributed to the corresponding images. By summing the contributions of all these images coherently, we can obtain the total received field at a receiver. Besides, the vector-effective height (VEH) of an antenna is introduced to consider the polarization coupling effect resulting from multiple reflection inside the rooms. We verify this approach by comparing the numerical results in three canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high-frequency radio propagation inside rooms where multiple reflection is dominant. Work reported in this paper has shown that the propagation loss in indoor environments varies considerably according to furniture and polarizations.