You are not logged in.
Dear all,
We are trying to find suitable high precision external clocks in order to drive the clock inputs on the clock board of the v2 WARP platform (the FPGA clock and RF clock). The clock precision that we are aiming for is around 0.1ppm - 1ppm. In selecting the clock sources, we would need some information regarding the signal properties of signals to be fed into the clock inputs, namely their respective frequency, waveform shape and voltage.
Apart from this technical information, if you have any suggestions regarding clock manufacturers that might offer suitable clock sources, we would appreciate that information as well. I guess you might have done a similar research step when selecting the oscillators for the clock boards.
Regards,
Vlad
Offline
For reference, the Clock Board schematics are available in the repository.
The external inputs on the clock board (J2 & J3) are routed through a transformer (Minicircuits TC1-1T; datasheet), then AC-coupled to the CLK1 port on the AD9510 clock buffers (datasheet). For frequencies in 10's of MHz, the transformer/coupling caps won't affect amplitude much, so the level requirements are determined by the AD9510 inputs. These are detailed on page 5 of the AD9510 datasheet.
The RF reference clock must be either 20MHz (default for the Clock Board) or 40MHz. If you use 40MHz, you'll need to change a value in the radio controller reset function which sets the MAX2829 reference clock ratio (see the code/comments in radio_controller_basic.c).
The range of frequencies for the sampling clock will depend on your FPGA design. Anything in [1,65]MHz will work for the Radio Board (the range of valid sampling frequencies for the AD9248 ADC; pg. 7 of its datasheet). Our reference designs assume a 40MHz clock, but could probably be modified to use other frequencies without too much trouble.
We don't have any exerience using clock sources that accurate. We've always used TCXO's in the WARP hardware, but these have tolerances of a few ppm. You'll probably need a OCXO to get the sub-ppm tolerance you're looking for. I don't think any exists that is small enough to replace an oscillator on the Clock Board (5x3mm package), but you may be able to find a eval board that could be cabled into the Clock Board.
Offline