Abstract: A system and method for receiving direct sequence spread spectrum transmissions with both chip code and frequency uncertainty including a parallel frequency acquisition technique for increasing receiver sensitivity and increasing process gain while reducing a preamble duration required for spread spectrum acquisition. The system and method include techniques for reducing effects of jamming and impulse noise on receiver performance via enhanced antenna diversity by constructively combining received signals. Further, techniques are provided which compensate for chip code alignment drift, providing an associated transmitter maintains carrier and chip code coherence, by comparing received signal energies at varying chip code alignments. These techniques enable the use of lower cost frequency setting crystals in both the receiver and transmitter as well as provide for system operation over a wider temperature range.

Abstract: The invention discloses several computation and control techniques which use historic information as well as other cues in order to enhance the accuracy of a radio position fix. These computational techniques include neural networks, mapped grid coefficients as input to a set of simultaneous or differential equations,and table lookup of correction coefficients for known low accuracy positions. The invention further discloses techniques for receiver array synchronization so that all system elements in a particular coverage area obtain a time reference appropriate for time of flight radio location measurements. The invention further teaches techniques to enhance the accuracy of a position fix by use of both fixed references, which are located in a coverage area, as well as a mobile reference carried by a search team. The invention also discloses techniques to provide information appropriate to guide a search team to an unknown positioned transmitter that is located within a building or structure.

Abstract: A method utilizing intentionally generated in-band frequency harmonics to compensate for frequency error and frequency drift in a voltage controlled oscillator of a receiver, thereby eliminating the frequency synthesizer and RF divider required in conventional designs. The method includes modulating the intentionally generated frequency in a predetermined manner so that a receiver can identify the intentionally generated frequency and includes the use of plural frequency harmonics for use in a curve fitting technique to correct frequency error in the voltage controlled oscillator.

Abstract: A method, apparatus, computer-based product and system employs a digital receiver (or transceiver) to receive, digitize and process a direct sequence spread spectrum signal using efficient, low-cost digital signal processing components. A radio front end portion of the receiver receives and digitizes the signal, and a digital signal processing portion downconverts and despreads the signal by applying a pseudorandom noise (PN) code, used at a transmitter to spread a data signal contained in the direct sequence spread spectrum signal, to the received signal. In order to initially align, and maintain alignment of, the PN code with the direct sequence spread spectrum signal, a timing and state control mechanism is included that provides time reference correction information to the signal processing components of the receiver.

Abstract: A direct sequence spread spectrum (DSSS) DSP implementation technique utilizing a unique combination of multiple filters, transforms, despreading algorithm and spectral compression, all in a single coefficient set, providing a highly efficient system requiring relatively nominal computational hardware and software requirements. Reallocatable computational resources allow for frequency uncertainty in the transmitter, without the typical excessive noise bandwidth penalties. The present system further contemplates a unique energy detection algorithm for discerning spread spectrum while in the search mode, utilizing several discrete sampling data sets to increase signal strength, reducing noise, while changing the relative phase of the received chipping code with respect to the received signal. The spectral compression of the spreading sequence is achieved by representing the PRC as an array of two, complimenting fractional coefficients.

Abstract: The invention discloses several computation and control techniques which use historic information as well as other cues in order to enhance the accuracy of a radio position fix. These computational techniques include neural networks, mapped grid coefficients as input to a set of simultaneous or differential equations,and table lookup of correction coefficients for known low accuracy positions. The invention further discloses techniques for receiver array synchronization so that all system elements in a particular coverage area obtain a time reference appropriate for time of flight radio location measurements. The invention further teaches techniques to enhance the accuracy of a position fix by use of both fixed references, which are located in a coverage area, as well as a mobile reference carried by a search team. The invention also discloses techniques to provide information appropriate to guide a search team to an unknown positioned transmitter that is located within a building or structure.

Abstract: An improvement in spread spectrum modulator systems, and more particularly further improvements in spread spectrum BPSK, or Binary Phase Shift Keying, Modulation systems, the present invention contemplating the utilization of an exclusive OR logic gate to replace an RF mixer stage in the SS transmitter, thereby providing enhanced gain at a lower energy consumption, with lesser cost and suppressed carrier output when compared to prior systems, as well as compatibility with CMOS low power logic modulation drive circuitry. The present system teaches a new, superior, and less costly BPSK transmitter than contemplated by the prior art, providing a less complicated system while outputting increased gain over prior art modulators.

Abstract: A method for improving a radio location system based on time-of-arrival. Time-of-arrival radio location systems are limited in ultimate accuracy by signal-to-noise ratio and by the time varying multipath environment in which they must operate. The present invention teaches techniques which maintain a high signal-to-noise ratio while identifying a feature of the received signal which is least affected by multipath. The technique uses correlation peak/envelope information to estimate the leading edge of the correlation function, then enhances discrete samples at the leading edge of the correlation function to yield high signal-to-noise ratio readings. The present invention can reduce required transmitted bandwidth, increase system resolution and accuracy by twenty to one, and maintain high message traffic throughput.

Abstract: A method for improving a radio location system based on time-of-arrival. Time-of-arrival radio location systems are limited in ultimate accuracy by signal-to-noise ratio and by the time varying multipath environment in which they must operate. These systems time stamp some feature of an arriving signal, from a transmitter, in order to calculate a range or a hyperbolic line-of-position. Some feature of the received signal must be identified which can provide repeatable readings, in order for a time-of-arrival system to be reliable. The present invention teaches techniques which maintain a high signal-to-noise ratio while identifying a feature of the received signal which is least affected by multipath. The technique uses correlation peak/envelope information to estimate the leading edge of the correlation function, then enhances discrete samples at the leading edge of the correlation function to yield high signal-to-noise ratio readings.

Abstract: The invention discloses several computation and control techniques which use historic information as well as other cues in order to enhance the accuracy of a radio position fix. These computational techniques include neural networks, mapped grid coefficients as input to a set of simultaneous or differential equations, and table lookup of correction coefficients for known low accuracy positions. The invention further discloses techniques for receiver array synchronization so that all system elements in a particular coverage area obtain a time reference appropriate for time of flight radio location measurements. The invention further teaches techniques to enhance the accuracy of a position fix by use of both fixed references, which are located in a coverage area, as well as a mobile reference carried by a search team. The invention also discloses techniques to provide information appropriate to guide a search team to an unknown positioned transmitter that is located within a building or structure.

Abstract: An enhanced frequency-agile radio for avoiding undesired signal energy, based on a prediction, by scanning an available radio spectrum, measuring a receiver output, identifying an occupied portion of the available spectrum, predicting a level of undesired signal energy in a future scan, and storing the prediction.

Abstract: An enhanced system for calculating the Z-Axis, or relative height or altitude, of a radio beacon. The present invention uses a barometric pressure sensing device co-located with the radio emitter to transmit data representing relative altitude. To further enhance the Z-Axis determination, one or several barometric sensors, located at known heights, are positioned around the city to provide real time barometric data. This real time data is used to form a differential correction factor which is compared to the to the time varying barometric sensor co-located with the radio emitter, thereby yielding Z-Axis accuracies of up to one (1) foot. Since the altitude essentially becomes a "known", this information can also be used in the least squares fit algorithm to enhance the X and Y determination as well.

Abstract: A method for maintaining spread spectrum chip sequence synchronization, over arbitrary time periods, without the use of traditional closed loop strategies. The technique can be accomplished entirely in software or with the addition of a minimum of electronic components. The receiver periodically forces a chip code reposition optimization to jog the receiver-chip sequence into a high level of synchronization after some period of time in which the receiver's chip sequence alignment has run open loop with respect to the transmitter-chip sequence embedded in the received spread-spectrum signal. The reposition technique allows the use of very low cost crystals for the chip sequence generator time base in both receiver and transmitter, and also provides time cues in which to optimize time-of-flight radio position fixes.

Abstract: A system for preventing unauthorized access to the programming and control features of a fire/security/control systems remote sensors. The exemplary embodiment of the present invention utilizes an association of transmitter identity/address with a central processor/control fire/security data base, which in turn is configured to securely program each transmitter with its location and function, or "personality". The various, individual sensors and central processor/control unit communicate individually via individual, repeatable pseudo randomization algorithms, producing a several bit result. The communicating central processor/control and each sensor must have a match on outgoing/incoming code before the transmitting sensor will accept the programming on its personality. The exemplary embodiment of the present invention also utilizes a randomization seed, which can altered occasionally, to further increase security.