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Wednesday, April 6, 2016

Generating Multi-PhaseWaveforms

Applications for multi-phase waveforms are everywhere – in Power-related applications, I/Q modulation, Automobile applications, Components,etc.

While Siglent’s SDG2000X series arbitrary waveform function generators all have two independent outputs with adjustable phase offsets, some applications call for three or more different signals, each with a phase relationship that is locked-to but adjustable from the other waveform phases. There are two main methods to accomplish this. For this application note we will use the SDG2000X generator.

Key Features
◆ Dual-channel, 40MHz/80MHz/120MHz maximum bandwidth, 20Vpp maximum output amplitude, high fidelity output with 80dB dynamic range
◆ High-performance sampling system with 300MSa/s sampling rate (1.2Gsa/s by 4X interpolation technology)  and 16-bit vertical resolution. No detail in your waveforms will be lost
◆ Innovative TrueArb technology, based on a point-by-point architecture, supports any 8pts~8Mpts Arb waveform with a sampling rate in range of 1μSa/s~75MSa/s
◆ Innovative Easy Pulse technology, capable of generating Square with lower jitter 150ps or Pulse waveforms, brings a wide range and extremely high precision in pulse width and rise/fall times adjustment
◆ Plenty of analog and digital modulation types: AM, DSB-AM, FM, PM, FSK, ASK and PWM
◆ Sweep and Burst function
◆ High precision Frequency Counter
◆ Standard interfaces: USB Device, USB Host, LAN(VXI-11, support U Disk storage and software, upgrading GPIB port is optional
◆ 4.3” touch screen display for easier operation


Each SDG2000X series generator has a built-in10MHz time base output/input port on the rear panel. Because each SDG2000X has two independent front-panel waveform outputs along with the ability to separate them by a calibrated amount of phase, we can use one SDG2000X for every two phases that is needed.
If only 3 or 4 phases are required for the application, simply connect the 10 MHz output from the first SDG2000X (Unit 1) to the 10 MHz input port of the second SDG2000X (Unit 2) via a suitable coaxial cable connection as shown in Photo 1. In this photo, the top generator’s time base is connected (Unit 1) to the bottom generator’s 10 MHz reference input (Unit 2) via a coaxialcable.

The next step is to set Unit 2 so that it uses the external 10 MHz time base (from Unit 1). On the Unit 2 keyboard:
a) Press UTILITY key on the front panel.
b) Choose Page selection
c) Chose CLKSource and push key to select External

The two SDG2000X generators are now sharing the Unit 1 time base. Notice that the two outputs from Unit 1 are synchronized1 and have adjustable phases. The same is true for the two outputs from Unit 2. However, there will be a phase offset of some arbitrary value existing between Unit 1’s two outputs and Unit 2’s two outputs. This is due to the fact that the two generators are locked to the same time base but the outputs were not synchronized upon power-up2 
The two outputs on Unit 2 can now be adjusted to be in phase (using and oscilloscope or other suitable phase displaying device) to the outputs from Unit 1. Once Unit 2’ outputs are inphase with Unit 1’s outputs then make note of the phase readings for the output’s from Unit 2. These ‘offset’ values will then need to be subtracted from any subsequent phase adjustment readings.

In Method 2, Unit 2 will use its own internal time base so CLKSource will be set to Internal on Unit1 and Unit 2.In this method, Unit1 will trigger Unit2 (and additional units if they are used) so that a residual phase offset is not present and does not need to be subtracted out of the settings.
On the rear panel, connect the theAux In/Out connector from Unit 1 with a coaxial cable to the Aux In/out connector on the back panel of Unit 2 (Photo2).
Once the connections in both Photo 1 and Photo 2 are made the generators are ready to set up from the front panel.
a) Push the BURST button. Make sure the unit is in NCYCLE mode and set for 1cycle.
b) Select Page then set the ‘Tirig Out’ selection for ‘Up’ ,Source should be set for Internal
c) Repeat step a for CH2.

a) Push the BURST button. Make sure the unit is in NCYCLE mode and set for 1cycle.
b) Select More then set the ‘Edge’ selection for ‘Up’. Source should be set for External.
c) Repeat steps a and b for CH2.

To Synchronize the Two Generators
The Phase adjustment for the two Unit 2 outputs can be adjusted from the Starting Phase screen under Burst for each of the two channels.
This photo (Photo 3) shows 4 output sine waves generated from two separate SDG5000 generator. Channel 2 is set to a 90 deg phase, Channel 3 (Unit 2, Channel 1) is set to 180 degrees and Channel 4 (Unit 2, Channel 2) is set to 270 degrees. Notice that the phase shifts are Leading.
If CH1 and CH2 are out of phase for either unit during setup choose EqPhase from the menu in order to align the two phase 

1 comment:

  1. I have heard about this generator before, and even wanted to buy it, but my friend said that its a little bit unreliable. I trust my friend, cause he is true beast in such technic. After that accident he advised me rigol dg1022 that I have been using for one years, and really, I still didnt have even single problem with it.