LOCATING VEHICLES USING THEIR VOICE TRANSMISSIONS

• US 3,793,635 A
• Filed: 12/08/1972
• Issued: 02/19/1974
• Est. Priority Date: 12/08/1972
• Status: Expired due to Term

• Current Assignee: Basil E. Potter
• Original Assignee: Basil E. Potter
• Inventors: Potter, Basil E.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/313,526
• Time in Patent Office: 438 Days
• Field of Search: 343/1CL,112R,112TC 235/150.272
• US Class Current: 342/463
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A system for locating plural mobile units, vehicle aircraft or marine, using their voice or other intelligence transmissions to indicate their respective locations relative to at least three fixed-position receivers. These transmissions are intermittently on the air, sometimes interfering and sometimes not, and the system uses a correlation technique for determining when the transmissions received at the spaced receivers are all initiated by the same mobile unit. If so, the signals received are narrowband filtered to recover a component of their modulation which can be used as an indication of the time of arrival of the transmission at each of the receivers. These filtered components are then delivered to a computer which determines the location of the mobile unit using well-known time-of-arrival solutions. Conversely, if several mobile units are transmitting at once, their signals will not successfully correlate and no computations are performed during such periods of interference.

Claims

1. A system for locating plural mobile units of the type having three or more mutually spaced fixed-position receivers tuned to receive modulated transmissions from the mobile units and the receivers being coupled by separate channels to computer means programmed to compute the locations of the mobile units based upon the relative times of arrival at the receivers of components of their respective transmissions, comprising:

a. signal gating means in the channels operative when enabled to pass the received transmissions in the channels toward the computer means;

b. delay means in the channels operative to delay the passage of said transmissions through the channels for a fixed interval of time;

c. means operative during said interval between reception of a transmission and its passage toward the computer to correlate the transmissions being received in the channels by displacing them relative to each other in time and comparing them for coincidence, and operative upon a finding of coincidence to enable said gating means; and

d. filter means in each channel connected respectively to receive said transmissions from said gating means, and responsive to pass a predetermined component of the modulation of the transmissions, and coupled to deliver said component from each channel to the computer means as a time-of-arrival indicating signal.

2. The system as set forth in claim 1, wherein the transmissions received from the mobile units are voice modulated, and the filter means in each channel comprise narrow passband filters all tuned to the same frequency component in the voice spectrum when said component is present in correlated transmissions, whereby components in the severaL channels are passed to the computer means.

3. The system as set forth in claim 2, including means at the output of each channel for detecting when a filtered component is present in that channel and for thereupon delivering a control output signal to the computer to indicate the presence of such input to it.

4. The system as set forth in claim 3, wherein each mobile unit transmission includes a unit-identifying message, and the system further includes means responsive to received transmissions in the channels for recognizing an identifying message and for enabling said detecting means for delivering its control signals.

5. The system as set forth in claim 1, said correlate means comprising energy presence detector and logic means associated with the channels and operative upon the reception of messages to detect the first channel in which an incoming transmission is received;

means responsive to the detection of energy in a first channel and operative during said delay interval to displace the transmission received in that channel progressively toward bringing it into coincidence with the transmission as received subsequently in the other channels, and to enable their gating means when coincidence occurs to pass the received transmission to the filter means.

6. A system for locating plural intermittent voice-transmitting mobile units with respect to three or more receivers disposed in fixed mutually spaced locations and coupled to computer means operative to compute the locations of the mobile units from the relative times of arrival of their voice transmissions via separate channels interconnecting the receivers with the computer means, comprising:

a. means for establishing the presence in the channels of transmitted energy emanating from a single one of said mobile units, and comprising means for relatively shifting part of the received energy in time while comparing the energy in the channels for coincidence, and means responsive to coincidence in the channels for passing another part of the energy in the channels toward the computer means with the relative time-of-arrival relationships thereof unshifted; and

b. means in each channel for filtering said another part of the energy in each channel to recover from it a narrow band component, and for delivering the component recovered from the energy in each channel to the computer means as an indication of the relative times of arrival of the transmitted energy at each channel.