The ADF5709 VCO is typically controlled by the ADF41513 PLL. An alternative being considered is using a high-speed DAC, such as the AD3551R, to drive the VTUNE input directly.
The following concerns are also considered :
Can a DAC provide stable tuning over a 0–10 V range for 10–16 GHz output?
Is a 200 ns settling time achievable with this method?
Can the DAC be placed on a separate PCB from the VCO without degrading performance?
Answer:
Using AD3551R DAC for ADF5709 VTUNE Control
The ADF5709 VCO can be controlled using the AD3551R DAC as an alternative to the ADF41513 PLL. This approach may require circuit modifications to meet the specific requirements of the AD3551R. While an exact settling time value is not specified, achieving a 200 ns settling time appears feasible with proper implementation.
The DAC can be placed on a separate PCB; however, careful routing of the connection between the AD3551R’s output and the ADF5709's VTUNE input is essential to maintain optimal performance. Proper layout and signal integrity measures should be considered to minimize noise and preserve frequency stability.