Patent ID: 7881397

Claim:
A method comprising: directly generating a phase-modulated signal using a direct digital synthesizer (DDS), the phase-modulated signal comprising a sequence of contiguous one-cycle sinusoidal waveforms having a frequency above 50 MHz and a carrier frequency above 50 MHz, wherein phases of the one-cycle sinusoidal waveforms correspond to symbols of a message signal, and wherein the carrier frequency of the phase-modulated signal is equal to the frequency of the one-cycle waveforms; reducing a bandwidth of the phase-modulated signal using a bandpass filter centered at the frequency of the contiguous one-cycle sinusoidal waveforms; wirelessly transmitting the phase-modulated signal; receiving a second phase-modulated signal comprising a second sequence of contiguous one-cycle sinusoidal waveforms; determining a phase of each of the contiguous one-cycle sinusoidal waveforms of the second phase-modulated signal to recover a second message signal; and wherein determining the phase comprises: collecting first and second samples from each of the contiguous one-cycle sinusoidal waveforms of the second phase-modulated signal at respective first and second sampling times occurring when the second phase-modulated signal is monotonic, the second sampling time occurring later than the first sampling time; calculating a difference between the first and second samples; and determining the phase based on whether the difference is a positive or negative value.