Hughes Aircraft Company

Raytheon Company

Hughes Aircraft

Roger J O'Connor

Khiem V Cai

Douglas A Dwyer

Stephen J Feitelson

Peter D Shloss

Keith A Lane

Gary S Gallagher

Michael Y Nishida

Edward Broad

Jeanne M Perales-Herdt

Robert C Knittle

Thomas L McDaniel

A cashless toll collection system and method that detects vehicles using transponders for prepaid customers and cameras for casual or non-transponder equipped vehicles. The system has a plurality of roadside toll collectors, one or more toll transaction processors, and a revenue management system. Each roadside toll collector has a vehicle to roadside communications system that communicates with transponders disposed in transponder equipped vehicles and generates entry and exit transaction reports indicating the entry and exit locations and times of the transponder equipped vehicles. Each roadside toll collector has a plurality of license plate cameras that selectively provide video images of license plates of vehicles that are not equipped with a transponder. Each roadside toll collector has a vehicle detector and classification system that detects the presence of vehicles, controls the cameras to capture the video images of the license plates, and generates entry and exit transaction reports indicating the entry and exit locations and times, and the license plate images of each detected vehicle that is not equipped with a transponder. The toll transaction processor processes the transaction reports to generate tolling transactions for each vehicle. The revenue management system processes the tolling transactions to generate tolls for each vehicle and generate bills for use of the toll road.

Open road cashless toll collection system and method using transponders

Apparatus and a method for generating a digital synthesized Gaussian noise-like waveform that may be used to modulate and demodulate communication data. The present invention uses a seed input that addresses a read only memory look-up table, for example, containing digital samples having Gaussian statistics. A sequence generator generates a pair of pseudo-random sequences in response to the seed input that address the read only memory to look up and output a pair of pseudo-random Gaussian samples that are used to generate the Gaussian noise-like waveform. A processor converts the pair of pseudo-random Gaussian samples into corresponding analog I and Q signals, and a modulator 33 modulates the analog I and Q signals to generate a modulated output signal having the Gaussian noise-like waveform.

Digital synthesized wideband noise-like waveform

A transponder detection system for detecting the presence at a detection area of a vehicle on which the transponder is mounted. Two antenna arrays are located on opposite sides of the detection area, and have their boresights directed to the detection area. For each array, a sum and difference signal of signals received from the transponder are measured. The sum channel signal is used to establish whether a transmission has occurred, and the difference channel signal is used to isolate any transponder that is at the detection area.

Transponder detection system and method

A method and system for tracking the position of a moving transmitter using angle of arrival measurements from direction finding antenna arrays. Each array includes several elements, with the elements grouped to provide subarrays of different element spacings which are multiple of one half the transmitter wavelength. Ambiguity is rejected by processing angle data received from the subarrays. The signals from the arrays are processed to convert electrical phase delay into spatial angles, the spatial angle data is processed to provide the x,y position, velocity and acceleration of the transmitter. For transmitters mounted in moving vehicles, the system further processes the x,y data and applies a quality weighting factor that filters out multipath factors and permits estimation of vehicle profile information.

Vehicle position tracking technique

A transponder location and tracking system having a phased array antenna mounted at a toll collection station includes a plurality of antenna array elements for receiving a signal from a transponder mounted on a vehicle and for providing a plurality of antenna element electrical signals. A plurality of phase detectors are provided for comparing the phase of the electrical signals to provide a plurality of phase difference signals. A plurality of angle-of-arrival calculation processors is provided for converting the phase difference signals to spatial signals to define the angles-of-arrival of the vehicle transponder signal. A position calculation processor is included for providing an output signal representative of the location of the vehicle in response to the defined angles-of-arrival. In a preferred embodiment, the transponder location and tracking system includes a plurality of receiver processing devices for amplifying and filtering the electrical signals from each antenna element. The phase detectors then compare the phase of the electrical signals to a reference element signal. Each phase detector provides a digital representation of the phase difference signals. The spatial signals represent the angle-of-arrival of the vehicle transponder signal. The position calculation processor operates on the spatial signal to determine the vehicle transponder position. A tracking mechanism is provided to plot the location of a moving vehicle along the roadway.

Transponder location and tracking system and method

Synchronization of a frequency hopping transceiver to a network by embedding synchronization codes in the pseudo-random frequency hopping transmission sequence. A receiver is implemented with a frequency detector and a correlator to generate a correlator signal in response to the synchronization codes in the pseudo-random frequency hopping transmission sequence. Detection of a peak in the correlator signal is indicative of synchronization of the receiver with the network. The network entry synchronization scheme is such that, when two transceivers A and B are communicating, a third unnetworked transceiver C extracts the hidden network entry code pattern from the A-B transmission in order to enter the network. As a part of the communication between the two transceivers A and B, transceiver A transmits a known pattern as a hidden part of the communication which allows transceiver C to enter the A-B network. This hidden code pattern permits rapid synchronization and correction of large initial time errors, and permits correction of time drift from then on.

Synchronization for entry to a network in a frequency hopping

Methods and apparatus for achieving high frequency (HF) modem communications. A predetermined plurality of frequency hopped, digital phase shift keying modulated tones are generated at a predetermined number of pseudo-randomly generated frequencies during a successive plurality of time frames. The phase of the tone at each frequency during a particular time frame is differentially modulated to one of a predetermined number of new phases using the phase of the tone at the same frequency in the previous frame as a reference. The tones are transmitted in the high frequency (HF) band, and then received and converted into digital signals. The digital signals are processed to determine the phase of the tone at each transmitted frequency. This may be accomplished by means of a Fourier transform filter. Finally the phase of each tone is compared to the phase of the tone received at the same frequency in the previous frame to decode the received signals, and hence accomplish the desired communications. The present invention provides for communications methods and apparatus which achieves HF skywave communications at high data rates with low bit error rate performance. The invention employs the use of frequency hopped digital phase shift keying and the convolutional coding that overcomes the dispersive nature of the HF channel and achieves the high data rate without resorting to channel equalization techniques. The performance of the modem of the present invention is not limited by the multimode multipath characteristics of the HF path. This is due to selection of a frequency dwell time that is significantly less than the multipath differential times of arrival, and a frame time of the waveform that is longer than the maximum multipath differential times of arrival.

HF high data rate modem

A method is disclosed for synchronizing the operation of frequency hopping, spread spectrum communication devices in a network. One device (the 'NTU') is deemed to be keeping the network time, to which the other devices must synchronize in order to communicate over the network. In a broadcast mode of the method an unsynchronized unit (a 'RTU') operates in an idle state to receive on a discrete set of receive frequencies. The total communication time period is divided into intervals, and a unique synchronization code is generated for each time interval which defines the idle state frequencies and time information transmit frequencies to be employed in accordance with the method. The time kept by the RTU is assumed to within a predetermined number of time interval of the present network time interval. In a broadcast mode the NTU transmits sequences of synchronization messages, each sequence including a message transmitted at a receive frequency for each of the past, present and future time intervals necessary to cover the time uncertainty time. This sequence is transmitted at a transmit hop rate substantially higher than the RTU receive hop rate, so that all possible receive frequencies and synchronization codes are bracketed by the transmission sequence. Each message include information enabling the RTU to predict the time and frequency at which network time information will be transmitted byt the NTU. The RTU receives one of the messages and tunes to the appropriate receive frequency to receive information enabling it to synchronize to the network time.

Growing community of inventors

Garden Grove, CA, United States of America

Roger J O'Connor