Patent ID: 8284858

Claim:
An opportunistic radiofrequency transmission system comprising: means of scanning a predetermined frequency range and determining an unoccupied frequency band in the predetermined frequency range that relates to a predefined communication standard; means of producing at least one digital signal quantised on N bits according to said communication standard and at a lower frequency than said unoccupied frequency and; for each of said at least one digital signal, digital processing means comprising: filtering means of a sigma-delta type capable of producing, on basis of a digital input signal quantised on N bits at said lower frequency, a digital output signal quantised on M bits at said lower frequency, where M is less than N; downstream from the sigma-delta type filtering means, means of repetition over-sampling capable of producing, on the basis of a digital input signal quantised on M bits and sampled at said lower frequency, an output signal quantised on M bits and sampled at L times the second frequency by inserting L−1 zeros between each sample of the digital input signal, thereby generating a signal at said unoccupied frequency band, where L is an integer and is an oversampling factor selected based on the unoccupied frequency band, and downstream from the means of repetition over-sampling, convolution means capable of convoluting the digital input signal quantised on M bits and sampled at L times said lower frequency with a sequence having a length equal to L or 2L samples, quantised on M bits and rotating at L times said lower frequency; digital-to-analogue conversion means capable of converting the convoluted digital output signal into an analogue signal; and analogue filtering means capable of filtering said analogue signal so as to select a narrow frequency band which includes said frequency in said unoccupied frequency band.