Abstract: An electronic ballasts for a gas discharge lamp. The ballast includes a variable frequency power generator, a tuned driver network, and a valley correction modulation system. The driver network has a first resonant frequency when the lamp is off and a second resonant frequency when the lamp is on. The power generator switches a rectified AC power line signal at a starting lamp frequency corresponding to the first resonant frequency for starting the lamp and at an operating lamp frequency corresponding to the second resonant frequency for operating the lamp. The valley correction modulation system compensates for the cyclic low voltages of the AC power line voltage cycle by adjusting the operating lamp frequency to be closer to the second resonant frequency.

Abstract: Methods and apparatus to transmit and receive information bits encoded in duobinary, multilevel pulse-amplitude-modulated (PAM) optical signals are described. The transmitted optical signal has a narrow optical spectrum and a low symbol rate. Information bits are encoded in a M-ary PAM symbol sequence, where M≧2. The PAM symbol sequence is input to a finite-state machine, which yields an encoded sequence that changes sign between two symbol intervals when the encoded sequence takes on a nominally zero value during an odd number of intervening symbol intervals. The encoded sequence is lowpass filtered and modulated onto an optical electric field. The receiver processes a received optical electric field to obtain an electrical signal proportional to the received optical intensity, and performs M-ary symbol-by-symbol decisions to recover the transmitted information bits, without potential error propagation.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector detects the presence of particular data states that are expected to result in particular modulation states or transition locations. When a particular data state is detected the IQ correction code compares the detected scalar magnitude with others that have been detected. The IQ correction code then uses the comparison to generate adjustments for I and Q offsets, I/Q phase, and I/Q gain. In a rotation embodiment, the modulation system further includes a rotation signal generator for generating rotation angles and an IQ rotator for applying the rotation angles for rotating the I and Q digital data streams.

Abstract: A cellular telephone having a global positioning system (GPS) receiver using a blended combination of GPS signals from GPS satellites and GPS pseudolites for determining a location. The cellular telephone includes a cellphone transceiver and a GPS receiver. The cellular transceiver receives wireless downlink cellphone signals from the cell site transceiver and transmits wireless uplink cellphone signals to the cell site transceiver. The cell site transceiver passes voice and data from the downlink and uplink cellphone signals within a local area into the worldwide network of telephone services. The GPS receiver receives satellite GPS signals from GPS satellites and pseudolite GPS signals from GPS pseudolites. The GPS pseudolites augment the GPS satellites for the local area by broadcasting pseudolite GPS signals having location-determination information with a format that is similar to the format in the satellite GPS signals.

Abstract: A differential global positioning system (DGPS) using coarse data for the locations-in-space of GPS satellites for ranging to the GPS satellites and then determining a precise differentially corrected GPS location of a GPS user receiver. The coarse GPS data can be GPS almanac data or non-current GPS ephemeris data as long as the same data is used by both a GPS reference receiver and the GPS user receiver.

Abstract: A GPS receiver having a fast acquisition of a GPS signal having a low signal-to-noise ratio. The GPS receiver adjusts a local frequency for iteratively downconverting raw GPS signal samples to baseband GPS signal code data, combining a plurality of code epochs of the GPS signal code data in chunks and super chunks for providing representative code epochs, and correlates the representative code epochs to a replica code epoch for providing correlation times. A microcontroller processes the correlation times for providing the frequency corrections and computes a GPS pseudorange when the error in the corrected local frequency is less than a threshold. The GPS pseudoranges for several GPS satellites are transmitted back to the base for computing the GPS-based location of the GPS receiver.

Abstract: A communication system having hubs and mobile units where a mobile unit uses selection signals from hubs during dedicated time slots for selecting a particular hub for communication during operational time slots. The hubs communicate on respective channels. The mobile units communicate with a particular hub on the channel associated with that hub. Each hub transmits a selection signal during a time slot that is dedicated for the selection signal from that hub. The mobile units base their selection of hub upon a comparison of the error rates of the respective selection signals and then communicate with the selected hub during with operational signals during the operational time slots. Certain message data is included in the selection signal from all the hubs in order to increase the reliability that the message data will be received by the mobile units.

Abstract: A GPS receiver having a fast time to lock to a GPS signal by storing a time period of an incoming GPS signal in a signal memory and rapidly comparing the signal memory against locations in a replica memory having stored GPS signal replicas. The GPS receiver includes a memory-based search engine for acquiring the GPS signal so that it may be tracked. The memory-based search engine includes a signal memory for storing a millisecond of a digitized GPS signal, a replica memory section for storing replicas representative of the digitized GPS signal for all possible frequency differences between the GPS carrier frequency and a local reference frequency and phase offsets between the GPS code phase and a local reference time, and a GPS memory comparator for comparing the stored signal in signal memory to the stored replicas in replica memory and issuing an acquisition detection signal when the level of the comparison is greater than a selected threshold.

Abstract: Methods and apparatus to transmit and receive information bits encoded in duobinary, multilevel pulse-amplitude-modulated (PAM) optical signals. The transmitted optical signal has a narrow optical spectrum and a low symbol rate. Information bits are encoded in a M-ary PAM symbol sequence, where M≳2. A subtraction-based encoder precodes and duobinary filters the M-ary PAM symbol sequence, yielding an encoded sequence. The encoded sequence is lowpass filtered and modulated onto an optical electric field. The receiver processes a received optical electric field to obtain an electrical signal proportional to the received optical intensity, and performs M-ary symbol-by-symbol decisions to recover the transmitted information bits, without potential error propagation.

Abstract: A communication system using GPS-based time for synchronizing communication data packets and symbols. The communication system includes a transmit apparatus for transmitting and a receive apparatus for receiving a communication data signal. The transmit apparatus includes a transmit station GPS receiver for providing GPS-based time, a transmit framer for using the GPS-based time for framing packets of communication data symbols, and a transmit symbol timer for synchronizing the communication data symbols to the GPS-based time. The receive apparatus includes a GPS receiver for providing the GPS-based time, a receive framer for using the GPS-based time for receiving the packets of the communication data signal, and a receive symbol timer for synchronizing the reception of the communication data symbols to the GPS-based time.

Abstract: A cordless machine operation detector including a vibration sensor, a location detector, a data logger, and a transceiver. The vibration sensor detects when a machine is operating by sensing the vibrations that are caused by the machine during operation. The location detector provides a geographical location and includes a time clock for providing time. The data logger uses time from the time clock and an operation indication from the vibration sensor for logging the time for operation of the machine. The data logger also logs a geographical location associated with the machine operation. The transceiver communicates the times and locations of the operation of the machine through an interchange to a tracking monitor. The machine operation detector, the interchange, or the tracking monitor includes an engine time monitor and an alarm sensor. The engine time monitor tracks an accumulated time of operation of the machine.

Abstract: Methods and apparatus to transmit and receive information bits encoded in duobinary, multilevel pulse-amplitude-modulated (PAM) optical signals are described. The transmitted optical signal has a narrow optical spectrum and a low symbol rate. Information bits are encoded in a M-ary PAM symbol sequence, where M≧3. The subsequence-based encoder decomposes the PAM symbol sequence into M1 subsequences, precodes each subsequence, performs duobinary filtering on each precoded subsequence, and forms a weighted sum of the duobinary precoded subsequences. The weighted sum of duobinary precoded subsequences is lowpass filtered and modulated onto an optical electric field. The receiver processes a received optical electric field to obtain an electrical signal proportional to the received optical intensity, and performs M-ary symbol-by-symbol decisions to recover the transmitted information bits, without potential error propagation.

Abstract: Methods and apparatus to transmit and receive information bits encoded in duobinary, multilevel pulse-amplitude-modulated (PAM) optical signals are described. The transmitted optical signal has a narrow optical spectrum and a low symbol rate. Information bits are encoded in a M-ary PAM symbol sequence, where M≧2. The PAM symbol sequence is input to a finite-state machine, which yields an encoded sequence that changes sign between two symbol intervals when the encoded sequence takes on a nominally zero value during an odd number of intervening symbol intervals. The encoded sequence is lowpass filtered and modulated onto an optical electric field. The receiver processes a received optical electric field to obtain an electrical signal proportional to the received optical intensity, and performs M-ary symbol-by-symbol decisions to recover the transmitted information bits, without potential error propagation.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes digital filters for converting I and Q data bit streams into filtered multilevel I and Q digital data streams, digital-to-analog converters for converting the digital data streams from digital to analog form, and an IQ modulator for converting the analog I and Q data streams into a modulated output signal having a representative IQ diagram having modulation states and transition locations between the modulation states. The digital filters include forward shifting memories having several samples of the data bit streams for each data bit time. The system also includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector monitors the data states in the memory and detects the presence of particular data states that are expected to result in particular modulation states or transition locations.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes digital filters for converting I and Q data bit streams into filtered multilevel I and Q digital data streams, digital-to-analog converters, and an IQ modulator for converting the analog I and Q data streams into a modulated output signal having a representative IQ diagram having modulation states and transition locations between the modulation states. The system also includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector monitors the data states in memories of the digital filters and detects the presence of particular data states that are expected to result in particular modulation states or transition locations. The amplitude detector monitors the modulated output signal and provides representative detected magnitudes.

Abstract: An electrified emergency exit device having a normally locked condition and having an operable hold off lock that is accessible from the emergency use side for maintaining an unlocked condition. The emergency exit device includes a star wheel door latch for locking or unlocking a door, a sliding catch having a lock position where the sliding catch is engaged to the door latch for locking the door and a free position where the sliding catch is disengaged from the door latch for unlocking the door, a push bar linkage operable from the emergency use side and coupled for sliding the sliding catch to the free position, a remotely operable solenoid coupled for sliding the sliding catch to the free position, the hold off lock coupled for maintaining the sliding catch in the free position, and a solenoid spring for biasing the solenoid for urging the sliding catch to the lock position when none of the push bar, solenoid, and hold off lock are actuated.

Abstract: A DGPS system using GPS almanac data for determining the locations-in-space and the DGPS corrections for GPS satellites for providing a differentially corrected location of a remote GPS user receiver. A GPS reference receiver determines almanac-based DGPS corrections from the differences between ranges that are measured to GPS satellites and ranges that are calculated to the GPS almanac-based locations-in-space of the GPS satellites from the known location of the GPS reference receiver. The GPS user receiver measures pseudoranges to the GPS satellites. Then, in a first embodiment, the GPS reference receiver radios the DGPS corrections to the GPS user receiver. The GPS user receiver uses almanac-based locations-in-space for the GPS satellites and the almanac-based DGPS corrections for differentially correcting the measured user pseudoranges for providing a differentially corrected user location. In a second embodiment, the GPS user receiver radios the measured user pseudoranges to the GPS reference receiver.

Abstract: A GPS receiver and an RF GPS integrated circuit for receiving a GPS signal. The GPS integrated circuit includes a synthesizer for generating LO signals, first and second downconverters for using the LO signals for downconverting the GPS signal, and a sampler for providing in-phase and quadrature phase sampled output signals representative of the GPS signal. The synthesizer includes a multi-mode divider for providing substantially the same first LO frequency at about the midpoint of the L1 and L2 GPS lo frequencies for either of two reference frequencies. The RF GPS integrated circuit uses an entirely on-chip voltage controlled oscillator (VCO) having a resonator for generating the LO signals and an entirely on-chip filter for filtering a first intermediate frequency signal.

Abstract: A global positioning system (GPS) controlled marking apparatus for staking and a method of using the apparatus to stake a surface. The apparatus uses a standard architectural or other surface site application program and a stakeout driver program in a standard computer and includes a GPS receiver, a stakeout tool, an autopilot, a vehicle, a geographical drawing converter, and a location comparator. The geographical drawing converter converts an image of a drawing pattern to geographical mark locations. The autopilot guides the vehicle to the geographical mark locations. The location comparator detects a location march between the geographical mark locations of the drawing pattern and a current geographical location determined by the GPS receiver. Information for the location match is used by the stakeout tool for driving a stake into the ground.