RF distribution demo (the first attempt)

Note: this is page describes the very first attempt at RF distribution over Ethernet, done in 2013. This system is no longer developed.

Specification

Default frequency: 10 MHz (LHC bunch clock). Can be reprogrammed to 1-70 MHz.
Single master node sending to single slave node.
Hardware: a DDS mezzanine hosted on a SPEC FMC carrier and a White Rabbit switch.

Clocks:*

Everything except the DAC is clocked with 125 MHz WR clock, coming from the FMC (not the SPEC local oscillator).
The DAC is driven with a 500 MHz clock, in-phase with the 125 MHz WR reference.

DDS core:*

Lookup table-based DDS with configurable resolution & tuning word width.
LUT interpolation and dithering - no spurs in the output (~90 dB SFDR).
Output sample rate: 500 MSPS, tuning words are delivered synchronously to WR clock and interpolated
4 times.

DDS PLL:*

Locks the phase of the DDS numerically controlled oscillator to the phase of the RF input signal.
Analog phase detector (ADF4002) followed by a simple antialiasing filter and a 16-bit 1MSPS ADC
The true loop filter is digital (a simple PI controller for the moment).
The loop filter works at 1/1024 of the WR clock rate (~122 kHz) to reduce the amount of data samples to send. Interpolation is done with a CIC (cascaded integrator-comb) filter.
Corrections wrs the baseline frequency are added to the DDS.

Data streaming:*

Correction values are timestamped and sent over Ethernet (through the streamers from the WR tutorial).
Received corrections are "executed" after a fixed delay (set to 20 us for the moment).
Point-to-point only for the moment, MAC addresses are fixed.

Tom's PH-ESE Demo presentation - contains also preliminary measurements

Properly calculate the PLL filter.
Phase compensation (currently the slave can recover only frequency).
Compression/prediction of correction values and/or adaptive interpolation ratio. Currently used fixed update rate of 122 kHz causes a lot of network traffic.
Fix mezzanine's issues.