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Can I use a DDS to produce modulation waveforms?

I understand that a DDS generates a sine wave. It seems logical that modulating the sine wave should follow easily.

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  • Modulation is, in fact, a logical extension of DDS.

    Because DDS provides digital tuning of the output frequency, the most obvious modulation format for DDS is FSK (frequency shift keying). Especially those DDS products that employ profiles (programming registers activated via one or more external pins). Users can program two or more profiles, each with a different frequency tuning word. Then use the profile pins to jump from one frequency to another at will. Generic FM is possible, too, but requires a controller capable of programming DDS frequency changes quickly enough to yield an FM signal.

    Most DDSs provide for programmable phase offsets. This feature opens the door for direct phase modulation. PSK (phase shift keying), like FSK, is readily implemented via profiles assuming the DDS includes phase offset as a profile parameter. Other phase modulation formats are possible, as well, but require a controller capable of programming phase changes quickly enough to yield the desire phase modulated signal.

    Some DDSs include a digital multiplier for scaling the DDS data just before delivering it to the DAC. Like the frequency and phase modulation examples above, AM (amplitude modulation) is possible by appropriately changing the digital scale factor over time.

    One DDS product in particular, the AD9910, provides the user with a 16-bit parallel port for real-time control of any one of the three DDS parameters (frequency, phase, amplitude). It even supports a polar modulation mode for simultaneously controlling both the amplitude and phase parameters.

    ADI also has a line of TxDACs (transmit DACs) and QDUCs (quadrature digital up-converters) that support a broad range of modulation types.

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  • Modulation is, in fact, a logical extension of DDS.

    Because DDS provides digital tuning of the output frequency, the most obvious modulation format for DDS is FSK (frequency shift keying). Especially those DDS products that employ profiles (programming registers activated via one or more external pins). Users can program two or more profiles, each with a different frequency tuning word. Then use the profile pins to jump from one frequency to another at will. Generic FM is possible, too, but requires a controller capable of programming DDS frequency changes quickly enough to yield an FM signal.

    Most DDSs provide for programmable phase offsets. This feature opens the door for direct phase modulation. PSK (phase shift keying), like FSK, is readily implemented via profiles assuming the DDS includes phase offset as a profile parameter. Other phase modulation formats are possible, as well, but require a controller capable of programming phase changes quickly enough to yield the desire phase modulated signal.

    Some DDSs include a digital multiplier for scaling the DDS data just before delivering it to the DAC. Like the frequency and phase modulation examples above, AM (amplitude modulation) is possible by appropriately changing the digital scale factor over time.

    One DDS product in particular, the AD9910, provides the user with a 16-bit parallel port for real-time control of any one of the three DDS parameters (frequency, phase, amplitude). It even supports a polar modulation mode for simultaneously controlling both the amplitude and phase parameters.

    ADI also has a line of TxDACs (transmit DACs) and QDUCs (quadrature digital up-converters) that support a broad range of modulation types.

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