Imaginary hyperbolic grid patterns formed by three local AM broadcasting stations were utilized in study. Each hyperbola is defined by constant phase difference between arbitrary signals integrally related to those coming from two stations. When three stations are used, grid is formed covering area with intersecting hyperbolas

Hansen, G. R., Jr.

English

NASA Technical Reports Server

February 1975	 B74-10300 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from' the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Location of Vehicles Using AM Station Broadcasting Signals 
A system has been studied- which can be- used in 
locating police, emergency, and fleet vehicles within a 
defined city area. The background of this study is 
published in a report entitled "Vehicle Location Study 
Phase 0 Report." The report discusses various 
systems used in navigation and approaches suitable 
for vehicle location. 
In the system studied, imaginary hyperbolic grid 
patterns formed by three local AM broadcasting 
stations are utilized. Each hyperbola is defined by the 
constant phase difference between arbitrary signals 
integrally related to those coming from two of the 
three stations. When three stations are used, a grid is 
formed covering an area with intersecting hyperbolas. 
Vehicles traveling within this area detect the change 
in position within the grid and transmit this 
information to a central monitoring station. 
Each vehicle is equipped with three phase-lock loop 
receivers. Each receiver unit is tuned to one of the 
three AM stations and generates the same arbitrary 
signal. The relative phases of these signals vary as the 
vehicle travels within the hyperbolic grid. This 
information is detected by the receivers and is stored 
electronically. The change in vehicle position within 
the grid is automatically transmitted after interroga-
tion by the central monitoring system. The central 
monitoring system computer then calculates the
geographical position of the vehicle- from the change 
in grid position. 
Note: 
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to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP74-10300 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive , or exclusive license for its commercial 
development should be addressed to: 
Patent Counsel - 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: G. R. Hansen, Jr., of

Caltech/JPL
under contract to

NASA Pasadena Office
(NPO-13217) 
Category: 02 (Electronics Systems) 
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Location of vehicles using AM station broadcasting signals

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