Introduction
This application note will cover procedures for synchronizing LeCroy’s ArbStudio four-channel arbitrary waveform generators, which can be accomplished with or without an external trigger. Here, we show two synchronized instruments, but the concept can be expanded to as many as eight four-channel ArbStudios, yielding up to 32 outputs.
The Basic Setup (With External Trigger Source)
Synchronization of multiple ArbStudios can be approached in two ways: One is a traditional configuration in which each ArbStudio is fed with an external trigger source, while the other takes advantage of ArbStudio’s unique capability to be synchronized without an external trigger. Figure 1 shows the basic connection diagram for synchronizing two fourchannel ArbStudios, thus creating an eight-channel, time- and phasesynchronized arbitrary waveform generator. This configuration is a traditional one using an external Trigger-In source for both Arbstudios. In fact, this configuration will work not only with ArbStudios, but with many arbitrary waveform generators available on the market.
The 50-Ω coaxial cable from the trigger source’s output to the input of the power divider may be of arbitrary length (shorter is better). However, it’s recommended that the two 50-Ω coaxial cables connecting the outputs of the power divider to the Trigger In ports on the ArbStudios be of equal length and as short as possible. Lastly, both ArbStudios are connected by USB cables to a PC running LeCroy’s ArbStudio software, which provides the user interface for creating waveforms and controlling the generators. In the ArbStudio software, one of the ArbStudios is designated as the master and the other as the slave.
The Basic Setup (With No External Trigger)
As mentioned above and as shown in Figure 2, ArbStudio is unique among arbitrary waveform generators in that as many as eight units may be time- and phase-synchronized without any external trigger source. On the rear panel of each ArbStudio are two expansion-bus ports. Synchronizing multiple ArbStudios is a simple matter of interconnecting these ports with LeCroy’s AS-SYNC ArbStudio sync cable. The AS-SYNC cable transmits a common 25-MHz clock signal as well as Start/Stop/Marker signals that are synchronized with an internal clock in the master unit to all connected slave units. Synchronization accuracy amongst all ArbStudios is < 300 ps.
As with an external trigger source, all synchronized ArbStudios must be connected via USB cable to a PC running LeCroy’s ArbStudio software, which provides the user interface for creating waveforms and controlling the generators. In the ArbStudio software, one of the ArbStudios is designated as the master and the other as the slave. Figure 3 shows an ArbStudio screen capture in which Device #1 is designated as Master, which is denoted by a “crown” symbol.
Generating A Waveform
After establishing connection between the ArbStudios, the next step is to get it all running. The configuration shown in Figure 1 was demonstrated using a LeCroy WaveStation 2052, a 50-MHz waveform generator, as the trigger source (any suitable trigger source will do). The WaveStation is set to deliver a 100-Hz square wave with an amplitude of 4 V pk-pk. That trigger signal is fed into a 50-Ω power divider, and the divider’s two outputs feed the Trigger In ports of the two ArbStudio 1104 arbitrary waveform generators. Thus, each ArbStudio sees a Trigger In signal of 2 V pk-pk.
In the case of the setup shown in Figure 2, all that is required is the AS-SYNC cable between two four-channel ArbStudio models 1104 or 1104D (the latter adds up to 36 digital channels).
A waveform created in the ArbStudio software’s Advanced Waveform Editing function was loaded in an ArbStudio workspace and delivered to the waveform generators via USB. The generators were run in stepped mode with the last point in the waveform being at 0 V, which was set as the output between triggers.
The output of Channel 1 from the two ArbStudios was observed on a LeCroy WaveSurfer 104MXs-A oscilloscope and can be seen in Figure 4.
Recommended Equipment
The LeCroy WaveStation and ArbStudio can both produce standard functions (ramp, sine, pulse, etc.) and arbitrary waveforms. They both have the capability to import real-world waveforms that have been captured by an oscilloscope. Both standard functions and arbitrary waveforms can be edited to add noise, glitches or other features to the signal. Because it has a shorter memory than the ArbStudio, the WaveStation is better suited to producing shorter, repetitive waveforms.
There are many types of oscilloscopes that can be used to observe the output of the waveform generators. One product line that is well suited is the WaveSurfer from LeCroy. It can perform an FFT of up to one million points when spectrum analysis is needed and, with the addition of the AudioBus option, can decode I2S, LJ, RJ, and TDM protocols. For automotive applications, there are also options to decode CANbus, LIN, and FlexRay.
Summary
In situations requiring more than four time- and phase-synchronized analog outputs from an arbitrary waveform generator, LeCroy’s ArbStudio 1104 and 1104D generators lend themselves to being linked together to achieve that aim. Up to eight four-channel ArbStudios may be synchronized, giving the user control of as many as 32 analog channels simultaneously. Setup of the synchronized waveform generators is relatively simple.
