Patent attributes
A radio transmitter system responsive to a binary signal drives a narrow bandwidth VLF or LF antenna. A generator derives a first variable frequency wave frequency coded based on bit values of a binary signal. An arbitrary impulse response signal processor responsive to the first wave derives a first output signal having real and imaginary components representing the shape of a modulating wave having a variable amplitude envelope and the frequency of the coded values. A transmitter responsive to the processor output signal and a VLF or LF carrier supplies the antenna with another output signal including a modulation wave having a shape that is a substantial replica of the modulating wave shape. The processor causes the signal emitted by the antenna system to include modulation having a shape that is substantially the shape of the first wave.
