Remote identification device
First Claim
1. An apparatus for distinguishing a moveable subject from a group of moveable subjects, comprising:
- transmitting means for transmitting electromagnetic signals towards a remote area where the moveable subject to be identified is located, said transmitting means including a local receiving means;
remote receiving means for receiving said electromagnetic signals at said moveable subject to be identified, said moveable subject including an antenna;
impedance varying means including means for generating a remote predetermined binary sequence code for varying the terminating impedance of said antenna on said moveable subject wherein the scattering cross-section of said antenna to an incoming signal is a function of the match of the antenna to that signal such that a scattered reflected signal is produced, said reflected signal being modulated by variations of said impedance, said local receiving means receiving said reflected signal;
means for generating a local binary sequence code identical with said remote binary sequence code;
detecting means for detecting said reflected modulating signal at said local receiving means, said detecting means including means for cross-correlating said reflected signal modulated by said remote binary sequence code with said local binary sequence code, said cross-correlating means including an invert-noninvert switch receiving an input signal from said transmitting means and from said local binary sequence code generator, an integrator coupled to said switch, an amplifier coupled to said integrator, and a threshold detector coupled to said amplifier;
a sample circuit coupled to said threshold detector providing an indication of the presence or non-presence of said remote binary sequence code; and
means for synchronizing said reflected and local coded signals.
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0 Petitions
Accused Products
Abstract
The conventional way of achieving an identification, friend or foe (IFF) function for a moveable subject requires the subject to carry a transponder that emits a coded return when a radar pulse is received by its receiver. In the present invention, an IFF system is disclosed which departs from the conventional transponder method and employs no radio-frequency power source. Instead, it uses the scattering or reflecting properties of an antenna to modulate, in a distinctive manner, the radar return from a moveable subject. A binary sequence code generator modulates the impedance of a receiver antenna, with the reflected signal being detected and correlated with a synchronized code sequence at the radar.
31 Citations
7 Claims
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1. An apparatus for distinguishing a moveable subject from a group of moveable subjects, comprising:
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transmitting means for transmitting electromagnetic signals towards a remote area where the moveable subject to be identified is located, said transmitting means including a local receiving means; remote receiving means for receiving said electromagnetic signals at said moveable subject to be identified, said moveable subject including an antenna; impedance varying means including means for generating a remote predetermined binary sequence code for varying the terminating impedance of said antenna on said moveable subject wherein the scattering cross-section of said antenna to an incoming signal is a function of the match of the antenna to that signal such that a scattered reflected signal is produced, said reflected signal being modulated by variations of said impedance, said local receiving means receiving said reflected signal; means for generating a local binary sequence code identical with said remote binary sequence code; detecting means for detecting said reflected modulating signal at said local receiving means, said detecting means including means for cross-correlating said reflected signal modulated by said remote binary sequence code with said local binary sequence code, said cross-correlating means including an invert-noninvert switch receiving an input signal from said transmitting means and from said local binary sequence code generator, an integrator coupled to said switch, an amplifier coupled to said integrator, and a threshold detector coupled to said amplifier; a sample circuit coupled to said threshold detector providing an indication of the presence or non-presence of said remote binary sequence code; and means for synchronizing said reflected and local coded signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification