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 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 security device simulating a currency pack or the like to foil robbery includes a receiver unit for receiving a local carrier signal generated locally at the exits of the bank. The carrier signal includes information in a predetermined binary code and the security device includes logic elements producing a signal activating a tear gas charge or the like when a signal is received carrying information in the predetermined code.