Patent ID: 7639734

Claim:
An ultra-narrow bandwidth digital RF communication system comprising: at least one transmitter configured to transmit ultra-narrow bandwidth digital RF radio signals at a frequency of at least 0.5 GHz, wherein the RF radio signals comprise a sequence of message bits having a data rate in the range of about 1-100 bits per second, resulting in a transmitter carrier frequency having an ultra-narrow frequency bandwidth in the range of 1-100 Hz, and wherein the RF radio signals are subjected to interfering processes based upon channel conditions that could induce carrier frequency shifts and instabilities in the range of 2-1000 times larger than the message bandwidth, wherein the at least one transmitter comprises a crystal stabilized SAW oscillator further comprising a varactor for reducing phase noise and carrier frequency drift, and a receiver configured to receive RF radio signals, wherein the receiver is further configured to shift the carrier frequency and isolate the frequency bandwidth of the received messages, centered on the shifted carrier frequency, convert each signal to digital data, compute a spectrogram of the converted signal, detect the message bits by searching possible bit frequency-time paths in the spectrogram, using a detection bandwidth about the same width as the signal bandwidth, and track and extract the detected message bits from the received signals.