We decided to use a DDS for the low frequency (LF) path. ERASynth’s current prototype does not have the LF extension. For the final revision, we were pondering our options: DDS or adjustable divider. There are several adjustable dividers on the market by different vendors and they are cost-effective compared to DDS ICs. Dividers generate waveforms with digital circuitry; their outputs are rich in harmonics. In addition, they tend to consume more power than DDS ICs.

DDS ICs also generate waveforms with digital means, but they have a built-in DAC to convert the digital waveform to analog domain. After evaluating AD9913 –a 250 MSPS DDS IC by Analog Devices– we decided to use it for the LF path. With AD9913, we can easily go down to 250 kHz or even below. AD9913 provides significant power savings since it consumes no more than 70 mW in single tone mode. It also provides better overall harmonics performance compared to divider ICs