Vehicle locating system utilizing AM broadcasting station carriers

• US 3,889,264 A
• Filed: 05/21/1973
• Issued: 06/10/1975
• Est. Priority Date: 05/21/1973
• Status: Expired due to Term

• Current Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, George R. Hansen Jr
• Original Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, George R. Hansen Jr
• Inventors: Hansen, George R. Jr., Fletcher, James C. Administrator of the National Aeronautics and Space (N/A)
• Primary Examiner(s): Tubbesing, T. H.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/362,145
• Time in Patent Office: 750 Days
• Field of Search: 343/15R,112D
• US Class Current: 342/394
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

A vehicle locating system is disclosed which uses the carrier signals of unsynchronized commercial AM broadcasting stations to form hyperbolic isophase grid lines. Each vehicle is equipped with a three-channel receiver, each channel being tuned to a different one of three spaced apart stations to provide to a central station information of motion from a known position by counting isophase lines crossed. A stationary receiver similarly counts isophase lines, which cross some fixed location due to drift in the transmission of the unsynchronized stations, to provide drift information to be subtracted from the vehicle motion information.

Claims

1. In a radio position finding system of the hyperbolic isophase line type in which a plurality of radio signals are continuously received by a vehicle, a plurality of spaced apart AM broadcasting stations, each transmitting at a different frequency independently of the other stations, the number of stations being sufficient to provide at least two unique pairs of stations, each pair providing a family of hyperbolic isophase lines crossing lines of the other pair to form a grid, and a receiver carried by said vehicle, said receiver having a plurality of channels, each channel being tuned to a different one of said stations and having means For coherently converting the radio signal received to a common frequency, whereby all channels provide output signals at said common frequency, and the common frequency signal of each channel is in phase with the radio signal to which it is tuned, said receiver further having a plurality of counting means, each responsive to output signals of a different pair of channels to count up cycles of one signal of the pair and count down cycles of the other signal of the pair, whereby each counter provides a count of isophase lines crossed of a different family of isophase lines as said vehicle moves in an area covered by said grid from which counts a new position of the vehicle may be calculated with reference to a known starting position of the vehicle in said area.

2. In the radio position finding system defined by claim 1, a second receiver like the one carried by said vehicle in the particulars set forth, said second receiver being held stationary to provide counts of isophase lines crossing a fixed point due to drift in the frequencies of said broadcasting stations, whereby said drift counts may be subtracted from corresponding vehicle motion counts from said receiver carried by said vehicle.

3. In a radio position finding system as defined by claim 2, a radio transmitter connected to said second receiver for transmitting said drift counts to a location where said vehicle position is to be calculated.

4. In a radio position finding system as defined by claim 2, a radio transmitter connected to said vehicle receiver for transmitting vehicle motion counts to a central station, and a radio transmitter connected to said second receiver for transmitting said drift counts to said central station where said vehicle position is to be calculated.

5. In a radio position finding system of the hyperbolic isophase line type in which a plurality of signals are received and compared as to phase in pairs, thereby effectively providing a family of isophase lines from each pair, lines from one pair crossing lines of other pairs to provide a grid covering a geographic area, three spaced apart and unsynchronized AM broadcasting stations, each transmitting at a different frequency, and a receiver carried by said vehicle as it moves about in said area, said receiver comprising three receiver channels, each tuned to a different station and each having means for multiplying the signal received to a predetermined frequency, the output signal of each channel at said predetermined frequency being in phase with the signal received from a broadcast station, three up-down counters, each for comparing the phase of a different pair of channel output signals by counting up cycles of one channel output signal, and counting down cycles of another channel output signal of the pair being compared, and means for coupling said channel output signals to said counters in pairs.

6. The combination of claim 5 wherein said coupling means comprises a clock pulse source and synchronizing logic means responsive to clock pulses from said source for producing noninterfering pulses from cycles of said channel output signals, whereby cycles of one pair of channel output signals are counted up and down regardless of how close they are in phase.

7. The combination of claim 6 wherein said synchronizing means includes means for inhibiting each one of said counters from counting up or down when cycles of a pair of channel output signals being compared by the counter are in phase as received.

8. In a radio finding system as defined by claim 7, a second receiver like the one carried by said vehicle in the particulars set forth, said second receiver being held stationary to provide counts of isophase lines crossing a fixed point due to drift in the frequencies of said broadcasting stations, whereby said drift counts may be subtracted from corresponding vehicle motion counts from said vehicle receiver counters.

9. In a radio position finding system as defined by claim 8, a radio transmitter conNected to said second receiver for transmitting said drift counts to a location where said vehicle position is to be calculated.

10. In a radio position finding system as defined by claim 8, a radio transmitter connected to said vehicle receiver for transmitting vehicle motion counts to a central station, and a radio transmitter connected to said second receiver for transmitting said drift counts to said central station where said vehicle position is to be calculated.