Self-powered vehicle detection system
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsJohn F. Scarzello, Daniel S. Lenko, Albert D. Krall, Wayne R. Grine, Robert E. Brown, George W. Usher, Milton K. Mills, Albert M. Syeles
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Abstract
An improved self-powered vehicle detector (SPVD) uses a two-axis magnetomr to sense a vehicle's magnetic signature and then telemeter vehicle presence information to a roadside receiver. The SPVD system includes digital nulling loops to cancel D.C. offset changes in the magnetometic output, a multi-tone code transmitter to transmit vehicle presence and SPVD condition signal, and an omnidirectional microstrip antenna to simplify installation and maintenance of the SPVD.
Claims15
A vehicle detection system comprising:
- a two-axis magnetometer for generating signals proportional to the vertical and horizontal magnetic field components at a desired monitoring location;
- means coupled to said magnetometer for nulling said vertical and horizontal magnetic field signals whenever said signals are below a predetermined threshold level, wherein said nulling means generates a vehicle presence pulse whenever said vertical and horizontal magnetic field signals exceed said threshold level;
- encoder means coupled to said nulling means for generating a first multi-tone signal upon the occurence of the leading edge of said vehicle presence pulse and a second multi-tone signal upon the occurence of the trailing edge of said vehicle presence pulse;
- transmitter means coupled to said encoder means for generating a radio frequency signal proportional to said multi-tone signals;
- first antenna means coupled to said transmitter means for radiating said radio frequency signal as a vertically polarized wave;
- second antenna means spaced apart from said first antenna means for receiving said vertically polarized wave;
- receiver means coupled to said second antenna means for detecting and demodulating said radio frequency signal;
- and decoder means coupled to said receiver means for providing a control signal upon receipt of said multitone signals.
Dependencies are inferred from the claim text.