I want to generate an analog signal of 1MHz with 50Hz modulation. Can I do that numerically with a DDS and without any extern PGA ?
Thank you for help
Most DDSs require some type of external controller to handle the programming of internal registers, etc. Without an FPGA (or other type of control) how do you plan to control the DDS?
DDS is controlled with a PIC (18F23K20) via SPI. Frequencies are fixed, but the signal level may be adjusted... DDS is initialized at begin of main function (sinus wave, freqreg, phase)
In that case, I assume the PIC would be used for modulating phase, frequency and/or amplitude via the SPI.
Since your intended modulation frequency is only 50Hz you should be able to use the PIC to write modulation samples to the device (that is, samples of frequency, phase and/or amplitude). You'll need to provide samples at a rate of at least 100 samples/second to satisfy the Nyquist criteria.
Let's assume a 1kHz sample rate, in which case there will be 1ms between samples. Therefore, you'll have 1ms to update the appropriate device register(s) and assert any addition control pins required by the device. As long as you can program the device as needed within the sample period (1ms in this example), you should be able to perform the desired modulation.
Thank you for answer
How can we modify the signal amplitude, what is the right register in DDS ?
Or with a numeric potentiometer at output ?
Several of our DDSs have built-in digital amplitude control via the SPI port. You will find the appropriate register in the datasheet for the specific DDS you have in mind.
Retrieving data ...