Function
The DDS board produces two tuneable LO-frequencies at around 400 MHz for use on the MIXER-board. This board takes an input reference frequency, 100 MHz from the OCXO-board.
Using an AD9912 the (datasheet) frequency-tuning-word (FTW) is a 48-bit number, and when SYCLK is 1GHz the DDS output frequency is f_DDS = 1GHz * FTW / 2**48. Ideally the resolution would be 3.5 uHz, but we have found that the LSB is always zero, so effectively 47 bits of the FTW are tuneable, and the frequency resolution is 7.1 uHz.
When a 400MHz signal is output from the DDS the 7.1 uHz resolution corresponds to a fractional frequency change of 1.8e-14 (phase drift 1.5 ns/day).
Status
- 2020-06-02 DDS board draft
- 2020-01 Schematic design ongoing.
Implementation
- SYSCLK produced by ADF4531
- DDS used is AD9912
- LDOs LT3045 or LT3042
Links and references
- wb6dhw DDS-board
- OM3LZ DDS-board for AD9912
- Urukul ARTIQ-board, a 4-channel AD9912 DDS
- OZ2M DDS-board