06-02-2019, 09:00 AM
If you want cleaner spectra and/or higher frequencies then you either need a more advanced DDS chip or a DIY approach with programmable logic. This Xilinx document shows how to get the best out of DDS using their standard DDS core. Altera may have something similar. A small FPGA module is more expensive than those little AD9833 but not prohibitive. Then you need to add a decent DAC.
https://www.xilinx.com/support/documenta..._ds558.pdf
The FPGA can also do the 25Hz tone, mutliple frequencies at the same time, etc etc. All to be added together inside the device before applying the result to the DAC. Since 100MHz+ clock is very easy with a modern FPGA tehre will beno problem with 10MHz+ outputs. As I said elsewhere, Frank is experimenting with DDS to generate modulated audio and video in Band I.
https://www.xilinx.com/support/documenta..._ds558.pdf
The FPGA can also do the 25Hz tone, mutliple frequencies at the same time, etc etc. All to be added together inside the device before applying the result to the DAC. Since 100MHz+ clock is very easy with a modern FPGA tehre will beno problem with 10MHz+ outputs. As I said elsewhere, Frank is experimenting with DDS to generate modulated audio and video in Band I.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
