Patent ID: 8379698

Claim:
A circuit comprising: a digital modulation circuit receiving multiple channel binary data, and for each channel generating a digital representation; a digital-to-analogue (D/A) conversion circuit for each data channel, each said D/A conversion circuit receiving and converting respective said channel digital representations at a sampling rate to produce a resultant analogue signal that is band limited within each Nyquist zone of the sampling rate of said D/A conversion circuit, said band limitation being dependent on a characteristic of said channel digital representations; a bandpass filter receiving and filtering each analogue signal, the band width at the edges of the stop band of each said bandpass filter being wider than a respective band limited analogue signal and wider than the Nyquist bandwidth arising from the sampling rate of said D/A conversion circuit, whereby signal power in unwanted Nyquist zones is effectively removed; and a frequency translation circuit for translating said multiple channel bandpass filtered analogue signals in the frequency domain such that said multiple channel bandpass filtered analogue signals are each offset in the frequency domain by the band limitation of the band limited analogue signal, thereby abutting said multiple channel bandpass filtered analogue signals without any guard bands between adjacent channel signals.