Underground radio communication system for roadways

Claim 1

A roadway radio communication system for transmitting a radio communication signal to vehicles for traveling along the roadway comprising: a radio communications transmitter means having an input signal coupled thereto from a program signal source and producing an output drive signal coupled therefrom, a series of bridging amplifiers each coupled to the output drive signal of said radio communications transmitter, a set of at least two in-phase and one out-of-phase amplifiers being driven by one of said series of bridging amplifiers, said in-phase amplifiers being identified as in-phase with said bridging amplifier and said out-of-phase amplifier being outof-phase with said bridging amplifier, a set of five road-imbedded wires generally parallel oriented longitudinally beneath the surface of said roadway constituting radiation antenna means being coupled to a center wire, an inner pair and an outer pair of wires, respectively, means coupling said center wire to the output terminal of said out-of-phase amplifier, means coupling said inner pair of wires to the output terminals of said in-phase amplifiers, and means coupling said outer pair of wires through an impedance means to the output terminals of said out-of-phase amplifier, or to such amplifiers or phase networks as will insure constraint of its signal field, impedance terminating units at the ends of each of the set of five road-imbedded wires and connected between said ends and electrical ground, and said set of amplifiers phasing communication signals produced in said inner pair of wires in substantial phase opposition to the communication signals in the center wire and outer pair of wires, whereby communication signals of predetermined level are confined to the immediate upper vicinity of the roadway, constrained to a predetermined level remotely outwardly of the roadway.