Method of and system and apparatus for locating and/or tracking stolen or missing vehicles and the like

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The present invention relates to methods of and systems and apparatus for tracking stolen or missing vehicles and the like, being illustratively described in connection with its important and perhaps primary application to the recovery of stolen or missing automobiles and the like.

In U.S. Pat. No. 4,177,466 of common assignee with the present invention, an automobile theft detection system was proposed involving the concealment in protected automobiles or other vehicles of radio transceivers or transponders responsive to radio signal transmissions sent when vehicles are missing, and modulated with a code corresponding to the missing vehicle identification; each particular missing vehicle transponder transmitting the same transponder locator signal when its identification code is received for tracking by a police or other direction-finder vehicle. To implement a system of this character in practice, however, far more sophisticated techniques and safeguards are required, including the use of a single frequency for all transmissions and the problems of time-sharing dictated thereby, with protection against transponder transmission while other transmissions on that frequency are in progress; adaptability for varying the rate of transponder transmissions once initiated by request of the operator of the tracking receiver to provide faster or stepped-up periodic reply signals for homing-in on the vehicle; discrimination of different vehicle transponder reply transmissions for tracking; checks to insure against false transponder activation; and the solution of other practical usage problems such as the required police or other identification information storage and networking requirements for a universal, nationwide and/or at least state-wide system.

An object of the present invention, accordingly, is to provide an improved and highly practical method of and apparatus for locating and tracking stolen or missing vehicles and the like that, while employing prior underlying concepts of unique signal code-responsive transponders, provides the added sophistication, security and practical techniques found essential to enable a commercially useable universal system.

A further object is to provide such a system wherein, for the case of automobile theft, the vehicle owner need only report the theft, after which the entire system operates under the direct control of law enforcement equipment and personnel, with the system virtually insensitive to disarming or accidental activation.

Another object is to provide an improved transponder apparatus for identifying an object or vehicle with which it is associated and, where and if desired, permitting location of such object or vehicle.

It is a further object of this invention to provide such a transponder which broadcasts at a variable rate a reply code specific and unique to that transponder to establish its identity.

It is a further object of this invention to provide such a transponder for which such broadcast rate is externally controllable.

It is a further object of this invention to provide such a transponder which permits individual location of simultaneously broadcasting transponders on the same reply frequency.

It is a further object of this invention to provide such a transponder apparatus which can receive an activation code and transmit its reply code on the same frequency.

The invention results, in part, from the realization of a truly effective vehicle transponder that can detect encoded information, provide a reply code specific to the transponder, discern the presence of a specific identification code and a broadcast rate command in the encoded information, and determine the transmission period for the reply code based on the broadcast rate command.

Other and further objects will be explained hereinafter and are more fully delineated in the appended claims.

In summary, however, from its overall aspect, the invention embraces a method of tracking a computer-registered transponder equipped vehicle and the like, upon the same being missing, that comprises, checking the registration of such vehicle to determine that it is computer listed as transponder-equipped; upon affirmative determination of such transponder equipment listing, initiating the broadcasting in an appropriate sector of a radio activation command signal carrying coded identification unique to said vehicle and its transponder; receiving said command signal at the vehicle transponder, decoding the identification and verifying that the same is the unique code of said vehicle and its transponder, and, if so, causing the transponder to become activated to transmit periodic vehicle reply signals including unique identification; receiving said periodic vehicle reply signals in a tracking vehicle and locking onto the same; thereafter, at the request of the tracking vehicle, modifying the said sector radio activation command signals to provide increased-rate command signals to the vehicle transponder; and responding to the increased-rate command signals at the vehicle transponder to increase the periodicity of the transmitted transponder vehicle signals to facilitate tracking by the tracking vehicle.

From other viewpoints, the invention also involves a novel transponder apparatus for use in identifying the presence of an object interrogated by broadcasted radio activation command signals on a predetermined RF carrier carrying coded identification unique to that object and its transponder, the apparatus having, in combination, means for receiving said command signal and for decoding the identification and verifying that the same is the unique code of said object and its transponder; means operable in the event of such verification, for activating the transponder to transmit periodic reply signals on the same carrier frequency and including unique identification thereupon; and means responsive to further command signals requesting a variation in the rate of such reply signals for thereupon transmitting the reply signals at such varied rate.

From still another aspect, the invention provides a transponder apparatus which detects encoded information, discerns the presence of its specific and unique identification code and a broadcast rate command in the encoded information, and transmits a reply code specific to the transponder, while determining the next time of transmission of the reply code for periodically repeating such reply transmissions. In one construction, the transponder monitors RF command signals for predetermined encoded audio signal carried by the broadcast signal. The audio signal conveys encoded digital information using different audio frequency signals or tones, to define the information, which typically includes a broadcast rate command for the transponder replies and an identification code specific and unique to that transponder (although in certain instances a universal identification code such as a universal test code may be substituted for the specific identification code). The transponder converts the digital information into digital logic signals and, if the specific identification code is present, broadcasts a reply code, specific to the transponder, repeatedly at a rate determined by the externally controlled broadcast rate code command, which may be changed to vary the transponder reply rate. Mutual interference with both reception and transmission is avoided with the preferred single carrier frequency employed, by pseudo randomly varying the transmission period. A number of activated transmitters, moreover, can broadcast simultaneously on the same RF frequency as well as monitor that frequency for additional commands.

And, in another feature, the invention further provides a transponder vehicle tracking apparatus having, in combination, direction-finding means for receiving activated vehicle transponder periodic radio reply signals carrying vehicle identification code information; signal and microprocessor means for demodulating said identification code information and for alpha-numerically displaying the same; means also responsive to the last-named means for simultaneously displaying both the bearing from which the transponder reply signals are received and the signal strength thereof; and means for locking onto and displaying only radio reply signals of a selected vehicle transponder.

Mention should also be made of the feature of using non-volatile memory to remember the state of the transponder so that if electrical power should be removed after activation, when electrical power is restored to the transponder it will continue to transmit a reply code without need for re-activation.

Preferred and best mode embodiments and apparatus details are later explained.

The invention will now be described with reference to the accompanying drawings,

FIG. 1 of which is a system diagram of the preferred vehicle location system application of the concepts of the invention;

FIGS. 2 and 4 are block circuit diagrams of a transponder or transceiver apparatus particularly designed for use in the vehicles-to-be-tracked in the system of FIG. 1;

FIG. 3 is an encoded information sequence useful with the system;

FIG. 5 is a flow chart of the operation of the receiving and transmitting functions of the transponder of FIGS. 2 and 4;

FIGS. 6 and 7 are block circuit diagrams of a preferred vehicle tracking receiving and display systems for homing-in on the reply signals of the transponders of FIGS. 1, 2 and 4; and

FIG. 8 is a data flow diagram of the sector activation computer-controlled broadcast command system providing radio signals to interrogate and activate the vehicle transponders of the invention.

A description, first, of the overall philosophy and methodology underlying the total system operation of the invention in preferred form is in order, with reference to the system diagram of FIG. 1.

When a vehicle V (or V') equipped with the transponder T (or T') of the present invention is lost, the owner reports that fact to the local police department which, in turn, reports to a state computer station system S. In tests in Massachusetts, this system, as later explained, is termed LEAPS. This information is sent, as a matter of course, from station S, as by telephone network or link L, to a master computer file, preferably maintained, for example, by the National Crime Information Center (NCIC), a part of the FBI in Washington, D. C., (or at other suitable computer facilities) and whereat it is intended to have in storage (SVLS--stolen vehicle location system), a list of the vehicle identification numbers of registered subscribers to the theft system of the invention. Every stolen car report that comes in, will be checked against the subscriber list (SVLS data base), and if a match is found, a computer message will be sent back at L to the originating station S, with a set of information that includes a unique activation code and a unique reply code for the transponder of the stolen vehicle, and a description of the vehicle. This information, now at the computer (LEAPS) at location S, is used to cause a controlling computer (SVLS computer) to set up a transmission schedule and, as by microwave link M, initiating the transmitting of the activation code from a series of radio broadcasting transmitting antennas B (B'), operated sequentially or if sufficently spaced, simultaneously or in slave fashion, thereby causing the stolen vehicle transponder, if in the area or section, to activate with a certain probability. The activator code is broadcast periodically (schematically shown at C) until a report is received that the car has been retrieved or until some predetermined time interval has been exceeded. These activation command signals, broadcast at C, have the activation code of the vehicle transponder, check-sum digits, and certain command bits that cause turn-on, turn-off and speed-up, as later explained.

As before stated, the frequency of the broadcast transmitters is the same as that of every vehicle transponder; namely, for example, a nationally assigned VHF law-enforcement frequency. But each transponder T (T') transmits a digital coded response or reply of about a tenth of a second duration, periodically and preferably at pseudo random intervals, say, once every ten seconds, roughly. In accordance with a feature of the invention, however, if the transponder detects another transmission on the frequency, it waits until that message is completed and then commences its reply transmission.

A police or other tracking vehicle TR, appropriately equipped with a direction-finding antenna system A and a tracking receiver and display D, when within range of the missing vehicle, will display on an indicator panel the coded response of the vehicle transponder, received along schematic path(s) R (R'), a five-digit alpha-numeric code corresponding to the code being transmitted by the vehicle transponder T (T'). When the police officer sees that display at D, the officer calls into his radio dispatcher, via RD, who puts an inquiry at P into the state computer (LEAPS) and inquires as to the status of that code. If it turns out that this is a vehicle that is stolen or that it is otherwise desired to track, then the sector broadcast transmitters B (B') will be activated to send out a different transmission C distinguished from the first activation signals to vehicle transponders T (T') in that it represents a request to increase the periodicity or rate of vehicle transponder responses or replies. The second, step-up or speed-up reply request command signals C will have the same vehicle identification number. It may or may not have the same check-sum bits as the first type activation command signals, but it will have a different code in the command section of the message, causing the speed-up, as opposed to just turn-on.

When the vehicle transponder receiver receives this increased rate command signal, the transponder circuits will cause the transmission of the coded reply or response message signal from the transponder vehicle to be accelerated to a faster rate of transmission, say about once per second, along R (R'), so that those in the tracking vehicle TR, instead of seeing the coded number once every ten seconds on the display, will see it once every second or so to aid in homing-in. The transponder will stay in that speeded-up mode for a period of time, say 30 minutes, and then automatically return to the regular mode of transmitting once every ten seconds, the expectation being that within a half hour, the vehicle ought to have been recovered.

If recovery has not been made, the tracking vehicle can always ask for the speeded-up vehicle transponder reply command request to be broadcast again at B (B').

At the tracking vehicle TR, not only are vehicle transponder reply codes displayed, but a lock select or control (button, for example) is provided at D to cause the computer processor in the tracking device to display only signals with a particular reply code from a particular vehicle transponder, to the exclusion of other vehicle transponder signals as from other stolen vehicles in the area. In addition to the reply code display, the tracking vehicle installation is provided with a direction indicator such as a circle of light-emitting diodes that gives relative bearing or direction of reception of the transponder signals. The direction-finding system at the tracking vehicle preferably employs four roof antennas A, later discussed in connection with the embodiment of FIG. 6, that are electronically phased to determine the incoming signal by determining the Doppler shift, as is well-known, and providing the bearing indication.

In addition to the bearing indication, a bar-graph indicator is further provided at D that shows relative signal strength and thus a rough indication of range. This is important in tracking, particularly in urban environments where the signal can bounce off a building or other vehicles and trucks that may be close by. The signal that comes from the direction of the stolen vehicle will usually be the stronger; so that if the tracker sees the signal strength display in erratic mode, the direction of maximum signal strength is followed.

The tracking vehicle personnel, as they home-in, thus know the relative direction, the relative signal strength and a complete description of the vehicle being sought; and, of course, other information that may be pertinent such as whether the car may have been involved in an armed robbery or some other important aspect. After finding and securing the sought vehicle, the personnel of the tracking vehicle will report that the car has been retrieved so that the system may cancel the stolen car report in the NCIC and other computer files. Again, in accordance with preferred features of the invention, this is also automatically effected, with the software at NCIC checking and issuing a new set of command instructions which causes the turn-off of the command signals previously broadcasted in the search sector Other aspects of preferred refinements in the best mode of practice of the system of the invention include the following. Messages that come in to the computer controlling the broadcast transmitters are queued up before being transmitted because it takes a certain amount of time for the trasmitter to build up to full intensity, which amount of time is of the same order of magnitude as the messages-to-be-sent. The sector broadcast transmitters will send out their activation signals and codes on a periodic bases, perhaps once an hour or so, as before indicated, until the vehicle is either recovered or a certain period of time has gone by, which may, for example, be set at a month.

From a practical viewpoint, it is important to have some way of checking out the transponder system once it is installed in the car. This may be effected by an installation test unit, later described in connection with the functional or operational diagram of FIG. 5. This installation test unit is capable of sending a signal to the transponder receiver portion T-RX which the transponder recognizes as a signal coming from the test device and which causes the transmitter section T-TX of the transponder T to go into a low power mode, in response also to another safeguard signal that it picks up on it's DC power line, simultaneously.

In this preferred nationwide cooperative system illustrated in FIG. 1, (though the invention is also useful for smaller sectors, states, group of states or other sector sub-divisions as well), thus, each vehicle transponder or transceiver assembly is part of a national (or at least wide-area) stolen vehicle location system, as above indicated, shown as preferably coordi