Patent ID: 6434372
Filing Date: 2002-08-13
Classification: G01S,H01Q,H04B

Abstract:
A radio communications system comprising in combination:(a) a stationary system which comprises: (i) means for generating an airborne carrier frequency; (ii) means for generating an airborne radio communication; and (iii) means for receiving and demodulating a modulated, reflected airborne carrier frequency; and (b) a mobile unit which comprises: (i) data input means capable of generating electrical signals; (ii) a passive transponder comprising: an antenna having gain in a plurality of directions for receiving the modulated carrier frequency; an impedance switch in electrical connection with said antenna for varying the impedance thereof; and means for receiving the electrical signals from said data input means and for varying the impedance of said impedance switch in response thereto, thereby modulating the carrier frequency by varying the reflectivity of said antenna to the carrier frequency; (iii) a radio receiver for receiving the airborne radio communication from said means for generating an airborne radio communication and generating electrical signals therefrom; and (iv) data output means in electrical connection with said radio receiver for receiving the electrical signals generated thereby and generating an observable signal therefrom; whereby two-way radio communication is established between said stationary unit and said mobile unit.