Radio communication/control system for restricted range signaling near the earth{40 s surface

Claim 1

A radio communications system for inter-communications and control from a fixed station, comprising: at least two of a plurality of longitudinally disposed conductors generally parallel and juxtaposed in physical placement with respect to a communicating region, including means wherein the radio frequency current value and the phase and magnitude thereof arE chosen for the communicating region so as to produce relatively small radio field intensities in said communicating region, while generally establishing a desired distribution of horizontally and vertically polarized ''''near field'''' intensities by exploiting the existence of said vertically polarized ''''near field'''' intensity essentially directly above at least one of the conductors tending toward a maximum value while the existence of said horizontally polarized ''''near field'''' intensity tends toward a minimum value; said system for transmitting a radio communication signal to vehicles for traveling along the roadway, comprising: a radio communications transmitter means having terminal means for connection with an input signal coupled thereto from a program signal source and producing an output drive signal coupled therefrom, said conductors consisting of a length of coaxial line having an inner conductor and an outer conductor disposed and oriented longitudinally beneath a roadway or ground surface, and being driven at one end by said transmitter means, the other end of said coaxial line terminating in a passive device, and an added length of coaxial line similarly constructed to aid conductors of coaxial line, disposed and oriented for extending the roadway communications system being driven at one end by coupling to said passive device, said passive device comprising a capacitor and a primary transformer winding in series across the inner and outer conductor of the terminating end of the coaxial line, a first secondary transformer winding having one terminal connected to the outer conductor of the terminating end of the coaxial line, and the other terminal connected to the outer conductor of the driven end of the added length of coaxial line, a second secondary transformer winding inductively coupled to said primary transformer winding having one terminal capacitively coupled to the inner conductor of the driven end of the added coaxial line, and the other terminal connected to the outer conductor of the driven end of the added length of coaxial line, and a frequency trap filter means coupled between the inner conductor of the terminating end of the coaxial line and the inner conductor of the driven end of the added length of coaxial line.