Technical Insights > Benchtop

How to Phase Synchronize Two Signals Together with a Function Generator

2018-11-08  |  7 min read 

When you hear the word “synchronize,” you might think of synchronized swimming. Or, perhaps, synchronizing your watches to the official US time from the National Institute of Standards and Technology (NIST). Well, we are talking about the same thing related to electronic signaling phase synchronization.

For example, a group of synchronized swimmers are swimming backstroke at the same rate. The number of backstrokes per second is analogous to signal frequency. If their hand strokes are all perfectly timed, we can say they are phase synchronized. Clocks and watches are also phase aligned if their ‘second’ hands are in synch.

Today, we’ll look at what phase synchronization is from electronic signaling perspective and how to easily generate phase synchronized electronic signals with a function generator. We’ll also look at some applications where you need two-phase synchronized signals.

Not all function generators are the same. Some function generators require many steps to phase synchronize multiple channels and may go out of synch easily when changes are made to the signals.

So, what is phase synchronization and how do you set them up with a function generator?

Let us take an example of two periodic sinewave signals. In a single periodic cycle, a sinewave will oscillate from 0° to 359°. After that, it will restart at 0°. See Figure 1.

Sinusoidal signal plotted in degree angle
Figure 1. Sinusoidal signal plotted in degree angle.

Figure 2 shows two sinewaves (yellow & dark green waves) that are phase synchronized. The light green wave is 90° angle phase shifted from the dark green wave and yellow wave.

Phase difference between two signals
Figure 2. Two signals that are phase-synchronized and another signal with 90° phase difference.

Let’s look at how to phase synchronize two waveforms. For this example, we will use Keysight’s 33600A Trueform function generator. During pre-setup, I have already selected 3kHz and 100mV sinewaves for both channels via the Waveforms and Parameters menu buttons. Like most function generators, setting up two outputs doesn’t mean they are phase synchronized.

To synchronize your signals, select “Phase” under the Parameters menu and then select “Sync Internal.” Now, both channel waveforms will automatically phase synchronize.

Phase synchronization setup
Figure 3. Select “Sync Internal” to automatically synchronize two channels.

When testing, you may want to intentionally set a phase difference between the two output waveforms. The Trueform function generators allow you to set the phase difference in degree angle, in radians or a phase offset in time. All you need to do is simply select “Phase” under the Parameters menu button, and enter your phase angle.

Another way to create two identical, phase synchronized waveforms is tracking mode. Tracking mode is a simple way to make both outputs identical. To set up tracking mode, you first choose your desired waveform. In this case, we’ll use the same square wave with 3 kHz frequency and 100 mV on Channel 1. Then, select Dual Channel operation by pressing the Channel 1 Output button, and turn on the Tracking mode. (see Figure 4).

Dual channel tracking setup
Figure 4. Identical phase synchronized channel output settings.

The output of both Channels from the Trueform function generator are now two identical phase synchronized square waves with 3 kHz frequency and 100 mV amplitude, as shown in Figure 5.

Identical phase synchronized waveforms
Figure 5. Two identical phase synchronized waveforms (Phase 0° highlighted in red box).

What else can I do with my Trueform function generator?

1) Select frequency or amplitude dual channel coupling

Trueform function generator allows you to change the frequency or amplitude of one of your waveform outputs without losing phase synchronization with your other waveform.

This helps reduce the complexity of simulating mechanical gear systems with fixed ratios and always requires phase synchronization. AC inductive motors also require phase synchronization of sinusoidal waveforms.

2) Create identical inverted signals

The example in Figure 4 shows how to create two identical phase synchronized waveforms. Additionally, you can also create two identical, but complementary (opposite amplitude) waveforms by selecting the “Inverted” option.

Two identical but complementary (opposite amplitude) waveforms that are phase synchronized can be combined to simulate differential output signal.

3) Create an intentional phase offset with arbitrary waveforms

Sometimes, you need to intentionally set a phase offset between your two waveforms for testing. Here is one example: If you have a custom pair of IQ signals, you will want to keep a 90° phase angle relationship between your I and Q channels. To accomplish this, you simply set the signals to start at the same time and then load both custom signals onto Channels 1 and 2 respectively. Finally, go to the parameters menu and press SYNC ARBS button.

Phase Synchronization of Two Waveforms

Now you know how to phase synchronized two waveforms together to enable you to quickly simulate signals and test your devices or systems.

Keysight’s waveform generators are the ideal solution for this type of analysis. It simplifies setup, leaving you more time to run actual testing. The signal generation process has never been simpler, quicker and, less frustrating.

To learn more about phase synchronizing two waveforms with a waveform generator, check out the “5 key tips for getting the most out of your waveform generator” eBook.

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