Synchronization of multiple HDAWGs

This tutorial is applicable to the PQSC when used with multiple HDAWG.

Goals and Requirements

The goal of this tutorial is to demonstrate the multi-HDAWG synchronization with the PQSC. We demonstrate how to synchronize the clock reference of multiple HDAWG and how to synchronously start them. This tutorial assumes that you are already familiar with the HDAWG, otherwise, please do the tutorial ‘Basic Waveform Playback’ from the HDAWG user manual first. In order to visualize the multi-channel signals, an oscilloscope with sufficient bandwidth and channel number is required.

The equipment list is given below.

  • 1 PQSC

  • 2 or more HDAWGs

  • 1 oscilloscope (min. 2 channels, recommended 4, bandwidth 500 MHz or more)

  • 1 Ethernet switch

  • 1 Ethernet cable per instrument (supplied with your PQSC and HDAWGs)

  • 1 ZSync cable per HDAWG (supplied with your HDAWGs)

  • 2 SMA coaxial cables

  • 2 adaptors BNC male to SMA female

Preparation

Connect the cables as illustrated below. Make sure that the instruments are powered on and connected by Ethernet to your local area network (LAN) where the host computer resides.

For best performance, the system should be placed in a climate-controlled environment with stable temperature and humidity. Avoid exposing the instruments to direct sunlight.

After starting LabOne, the default web browser opens with the LabOne graphical user interface. It’s advised to open a tab in the browser for each instrument.

fig tutorial hdawgs multi devices sync basic setup
Figure 1. Connections for the multiple HDAWG synchronization tutorial

The tutorial can be started with the default instrument configuration (e.g. after a power cycle or after loading the Factory Default preset from the 'Device' tab) and the default user interface settings (e.g. as is after pressing F5 in the browser).

The PQSC needs to warm up for 30 minutes after power-up. Do not lock to external reference clock or start triggering before it’s ready. The CLK LED on the bottom right of the LabOne user interface will turn green when the instrument is ready to use.

Multi device synchronization

The first step to enable the device synchronization is to enable the ZSync clock and triggers on the HDAWGs. The following table summarizes the necessary settings. It should be repeated for each HDAWG connected to the PQSC.

Table 1. Settings: enable the ZSync clock on the HDAWG
Tab Sub-tab Section # Label Setting / Value / State

Device

Configuration

Reference clock Source

ZSync

Device

Configuration

Sample Clock Frequency (Hz)

2.4G

DIO

Digital I/O

Mode

QCCS
fig tutorial hdawgs sync ref clock
Figure 2. LabOne UI HDAWG: Device and DIO tabs

After changing the selector, the ‘Status’ LED will turn yellow for few seconds and then green again to signal that the HDAWG successfully locked to the reference clock provided by the PQSC over ZSync.

Then, check that the PQSC correctly recognized the HDAWGs. On the back of the instrument or in the ‘Ports’ tab of the PQSC verify that the status LED of the used ZSync ports turned blue and the serial number of the HDAWG is displayed. You may assign an alias to for each instrument to easily recognize it later.

The sample rate of the HDAWGs is variable. When used with the PQSC, two values are supported: 2.0 GSa/s or 2.4 GSa/s. The sample rate 2.0 GSa/s is useful when the HDAWG is used in conjunction with instruments from the SHF series which operate at the same sample rate. It’s not possible to mix the two sample rates: all HDAWGs connected to a PQSC must the same sample rate.

fig tutorial hdawgs sync pqsc ports
Figure 3. LabOne UI PQSC: Ports tab

Multi device synchronous triggering

To have a synchronous start of the HDAWGs, the PQSC needs to generate start triggers over ZSync and the HDAWGs have to wait for them and then start the execution. In the HDAWGs, these signals are internally routed over the DIO interface, which will be unavailable for normal usage.

We configure the sequencers to play a square waveform as soon as the trigger from the PQSC is received. The necessary settings are summarized in the following table. This must be done for each HDAWG connected to the PQSC.

Table 2. Settings: configure the HDAWG sequencers
Tab Sub-tab Section # Label Setting / Value / State

Output

Waveform Generators

4x2 channels

Output

Waveform Generators

1

Output Amplitude Wave 1

1.0

Output

Waveform Generators

1

Modulation

OFF

Output

Wave Outputs

1

Range

1 V

Output

Wave Outputs

1

Enable

ON

AWG Sequencer

Trigger

DIO Trigger

1

Strobe Slope

None

AWG Sequencer

Trigger

DIO Trigger

1

Valid Polarity

None

The following sequence should be loaded in the sequencer and then started:

wave w = ones(64);

while(true) {
  waitZSyncTrigger();
  playWave(w);
}

The AWG status LED will turn yellow, meaning that is ready and waiting for the trigger.

The scope should be configured as following:

Table 3. Settings: configure the external scope
Scope Setting Value / State

Ch1/Ch2 enable

ON

Ch1/Ch2 range

0.2 V/div

Timebase

20 ns/div

Trigger source

Ch1

Trigger level

200 mV

Run / Stop

ON

Finally, we configure the periodic trigger generation in the Ports tab of the PQSC and then start it by clinking on btn uielements runstop um button.

Table 4. Settings: configure the periodic trigger generation on the PQSC
Tab Sub-tab Section # Label Setting / Value / State

Ports

Control

Repetitions

2

Ports

Control

Holdoff (s)

100n

On the scope we can now see two pulses with both channels aligned in time. The inter-channel alignment can be further adjusted by changing the delay of each HDAWG Wave output in the field "Output > Wave Outputs > Delay (s)". The two pulses are spaced by 100 ns as specified by the Holdoff time.

fig tutorial hdawgs sync scope
Figure 4. Pulses as generated by the two HDAWG and captured by the scope