摘要:
An ultra-wideband (UWB) communications system combines the techniques of a transmitted reference (TR) and a multiple access scheme called delay hopping (DH). Combining these two techniques using UWB signaling results in a penalty in signal-to-noise ratio (SNR) over conventional pulse position modulation (PPM) techniques but avoids the synchronization difficulties associated with conventional approaches. The signaling pulse waveforms are designed to insure that their power spectral densities, after any frequency translation to the center of an operating band, are essentially spectrally disjoint with frequencies that must be protected. This TR technique is combined with the DH multiple access technique to create a UWB communications scheme that has a greater multiple access capacity than does the UWB TR technique by itself.
摘要:
In a system for optimizing television reception by a television receiver receiving a diversity of input signals from a plurality of antennas, one of a plurality of combiners and television tuners selects the strongest combination of input signals for viewing and another scans the various combinations of input signals searching for a combination significantly stronger than the combination being viewed. A plurality of multiplexers selects the output signal of one combiner and transmits the selected signal to one of the tuners. A signal evaluation module evaluates the strength of the combinations of input signals and compares the strength of each combination of input signals to the strength of the viewing signal, looking for a superior signal. A control processor controls the combination of input signals selected by the combiners and the combiner output signal selected by the multiplexers. The control processor converts any superior signal found into the signal being viewed, at which time the process starts over and repeats.
摘要:
A receiver for enabling one-way communications in a GHM network which does not interfere with or reduce the capability of the GHM network. The receiver detects a small modulation factor signal present on the GHM signal normally transmitted by the GHM transmitter. If the frequency of the modulated signal corresponds to a pre-defined frequency, then the receiver generates a command signal to, for example, a relay, annunciator, or other external device. More particularly, and in one embodiment, the receiver includes a filter which partially isolates the GHM energy from the lower 60 Hz harmonics. The receiver also includes a envelope detector coupled to filter. The envelope detector is coupled to a frequency detector. The frequency detector is coupled to a command decoder. The command decoder determines whether a plurality of AM modulation frequencies are present on the received signal. If the AM modulation signal is a specified frequency the decoder generates a signal which, in turn, causes signal generator to generate a command signal for transmission to an external device.
摘要:
The existing ATSC broadcast standard is modified to improve both the speed at which the periodically transmitted training sequence is found after channel selection by a viewer and the speed at which synchronization is achieved to a continuous wideband overlay signal used for equalization of the decoded signal. The modification involves slight amplitude modulation of the pilot signal in a manner synchronized with the transmission of the training sequences. The modulation of the pilot signal is sufficiently small to be ignored by existing ATSC receivers; that is, it is backwards compatible. Properly equipped receivers can detect, more quickly than receivers not so equipped, transmission of the training sequence by decoding this pilot signal modulation, thereby being capable of providing a decoded image to a viewer more quickly after a channel change than a receiver not so equipped. Additionally, the time required to synchronize to a continuous wideband overlay signal which has been provided for equalization is reduced, as by varying the modulation slightly to correspond to the start of a particular phase portion of the periodic sequence such as an m-sequence used for the overlay.
摘要:
A linking process allows a head-end unit (HEU) of a railroad train to determine the sequence of cars in the train using wireless links between nodes on the cars, and requires no physical connection between the nodes or cars. Each car in the train is equipped with a wireless communication device which models an oscillator i. Each oscillator is phase-variable, the phase .theta..sub.i linearly increasing from 0 to 1 such that, when the i.sup.th oscillator "fires", transmitting a packet, and phase .theta..sub.i then jumps back to zero. When a car receives the transmission of another car, it changes the phase of its oscillator according to a phase-response curve function, setting up a wave pattern of transmission from nodes, from one end of the train to the other end. The wave pattern, along with protocol logic, enables each car to determine the sequence in which cars are arranged in its vicinity. The protocol logic also enables each car to forward or relay this "local map" from all cars to the HEU, allowing the HEU to construct the entire train map which is the sequence of cars in the train. The compiled train map is compared with consist information and the operator is notified of any discrepancy.
摘要:
An array ultrasonic transducer precursor includes a body of piezoelectric material with a dielectric substrate bonded to a surface of the body. Circuit elements supported on the dielectric substrate include, in an active region, physically parallel signal conductors arranged in a pattern with spaces between adjacent ones of the conductors. Dicing saw cuts made in these spaces define individual circuit elements within the piezoelectric body. The circuit elements outside the active region include a set of resistive alignment elements in predetermined positions with reference to the pattern of signal conductors. The transducer precursor is mounted in a dicing saw fixture, and initial cuts made with the dicing saw remove portions of the resistive alignment elements. Locations of the initial cuts with reference to the resistive alignment elements are determined by measuring resistances of the resistive alignment elements after the initial cuts.
摘要:
A switched capacitor narrow band pass filter includes a first switch including a first pole movable between two first switch terminals, a second switch including a second pole moveable between second switch terminals, and a third switch including additional poles movable between third switch terminals. The filter further includes an effective capacitor coupled to the first pole and a plurality of matchinq capacitors coupled respectively to the second and third switch terminals. The additional poles are coupled to the third switch terminals according to a first predetermined sequence and to the third switch terminals at a predetermined frequency. A differential amplifier assembly includes two positive and two negative terminals coupled to the additional poles in a second predetermined sequence wherein two of the additional poles are coupled to the positive terminals and two others of the additional poles are coupled to the negative terminals for signal summation.
摘要:
A data gathering apparatus comprises a power generation device configured to generate power via movement of the rail. The data gathering apparatus further comprises a sensing device configured to receive power from the power generation device and to sense at least one property of the rail, wherein the property of the rail is at least partially defined by a vehicle traveling on the rail.
摘要:
A location system and method for determining the location of a tagged item in a facility. In one embodiment, the location system includes a plurality of room transmitters designed to be located throughout the facility. Each room transmitter has a unique signature. The system also includes at least one item or location tag affixed or otherwise associated with an item. Each tag is operable to send a signal having information related to the signature of a room transmitter within the reception range of the tag and information related to the identity of the tag. Signals from the tags are received by one or more locating receivers. Each locating receiver is operable to determine the identity of an item tag and the likely location of the item tag within the facility based upon the signal from that tag. The invention also provides a method of locating an item in a facility. In one embodiment, the method includes positioning room transmitters in multiple areas within a facility; configuring each room transmitter to generate a unique signature; fitting items with a tag; configuring each tag to generate a signal having a location portion and a signature portion; positioning a locating receiver within the facility; and determining the likely location and identity of that tag based on the tag's signal.
摘要:
A method for calibrating cameras includes moving a point of light on a first flat surface. A first and a second camera are capable of generating a first frame and a second frame of the point of light respectively. The respective points of light are in a first and a second field of view of the first and second camera. The method includes determining a relative position between the first camera and the second camera based in part on the first frame and the second frame.