Author Topic: The Siglent SDG2042X Thread  (Read 264009 times)

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Online ebastler

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Re: The Siglent SDG2042X Thread
« Reply #1100 on: July 06, 2019, 04:50:47 am »
Have you tried selecting an unmodulated Arb waveform first, via the ARWV command, then setting a modulated mode with the parameter-less ARB as the modulation source? Maybe the SDG remembers the last used Arb waveform and uses that for modulation?

Just a wild guess -- I don't have my SDG2042X here at the moment. And you might have said in your first post on this topic that you tried this without effect; not sure I understood that part right.

Edit: A related question: When you set the MDWV mode via "C1:MDWV DSBAM,MDSP,ARB", which Arb waveform does the generator use as the modulation source?
« Last Edit: July 06, 2019, 04:56:22 am by ebastler »
 

Offline colorado.rob

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Re: The Siglent SDG2042X Thread
« Reply #1101 on: July 06, 2019, 05:57:32 am »
Have you tried selecting an unmodulated Arb waveform first, via the ARWV command, then setting a modulated mode with the parameter-less ARB as the modulation source? Maybe the SDG remembers the last used Arb waveform and uses that for modulation?

Yes, of course.

Code: [Select]
>>C1:ARWV?
C1:ARWV NAME,custom.bin
>>>>C1:MDWV?
C1:MDWV STATE,ON,DSBAM,MDSP,ARB,SRC,INT,FRQ,0.1610824742HZ,CARR,WVTP,SINE,FRQ,28121000HZ,AMP,0.005V,AMPVRMS,0.0017675Vrms,OFST,0V,PHSE,0

Quote
Just a wild guess -- I don't have my SDG2042X here at the moment. And you might have said in your first post on this topic that you tried this without effect; not sure I understood that part right.

I thought that I mentioned that I tried this.

Quote
Edit: A related question: When you set the MDWV mode via "C1:MDWV DSBAM,MDSP,ARB", which Arb waveform does the generator use as the modulation source?

The first one in its list of internal waveforms: StairUp.



Or the last one selected manually by going into "arb:arb:..." from the modulation screen.
« Last Edit: July 06, 2019, 06:00:58 am by colorado.rob »
 
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Offline colorado.rob

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Re: The Siglent SDG2042X Thread
« Reply #1102 on: July 06, 2019, 06:39:37 am »
I was just trolling through the SDG2000X firmware and noticed the name "BK Precsion" [sic].  I had not seen that mentioned here in relation to the Siglent AWGs.  A quick look a the BK Precision website shows a number of AWGs that look a lot like our Siglent here.  Judging by the specs, they are not 2000X models (500MSps/14-bit).  But there is little doubt Siglent made a bunch of their current models.

 

Offline tautech

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Re: The Siglent SDG2042X Thread
« Reply #1103 on: July 06, 2019, 06:57:47 am »
I was just trolling through the SDG2000X firmware and noticed the name "BK Precsion" [sic].  I had not seen that mentioned here in relation to the Siglent AWGs.  A quick look a the BK Precision website shows a number of AWGs that look a lot like our Siglent here.  Judging by the specs, they are not 2000X models (500MSps/14-bit).  But there is little doubt Siglent made a bunch of their current models.
SDG1000X models.
A few other Siglent rebrands listed in this thread:
https://www.eevblog.com/forum/chat/remember-when-siglents-logo-wasnt-ugly/
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Offline avp1

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Re: The Siglent SDG2042X Thread
« Reply #1104 on: July 08, 2019, 01:30:33 pm »
I tried to search, but could not find an answer: is it possible to use one channel of SDG2042X as a modulation source for other channel without running a cable from its output to AUX input? If it is - what are the appropriate menu options to configure that?
 

Offline bdunham7

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Re: The Siglent SDG2042X Thread
« Reply #1105 on: July 08, 2019, 01:40:52 pm »
I was just trolling through the SDG2000X firmware and noticed the name "BK Precsion" [sic].  I had not seen that mentioned here in relation to the Siglent AWGs.  A quick look a the BK Precision website shows a number of AWGs that look a lot like our Siglent here.  Judging by the specs, they are not 2000X models (500MSps/14-bit).  But there is little doubt Siglent made a bunch of their current models.

BK sells some nice stuff, but I don't think they make any of it anymore.  Some of their very old legacy products are their orginal design but manufactured for them by somebody in Taiwan.  The rest of their line comes from wherever.  The one I haven't figured out yet is their 1856D counter from South Korea.  Anyone know who makes it?
 

Online jjoonathan

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Re: The Siglent SDG2042X Thread
« Reply #1106 on: July 08, 2019, 02:31:36 pm »
What about their AC power supplies? I've wanted something like this for a while:

https://www.bkprecision.com/products/power-supplies/9801-programmable-ac-power-source.html

but the price was a bit hard to justify. If it's just a rebrand and is available somewhere else for cheaper, I'd be delighted!  ;D
 

Offline McBryce

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Re: The Siglent SDG2042X Thread
« Reply #1107 on: July 08, 2019, 04:51:18 pm »
What about their AC power supplies? I've wanted something like this for a while:

https://www.bkprecision.com/products/power-supplies/9801-programmable-ac-power-source.html

but the price was a bit hard to justify. If it's just a rebrand and is available somewhere else for cheaper, I'd be delighted!  ;D


Hmmm, looks suspiciously like an iTech IT7321 :)

https://www.itechcanada.ca/products/ac-source/it7300-series/it7321/

Usually Maynuo do clones with the same family of labels, but they don't seem to have released one yet.

McBryce.
« Last Edit: July 08, 2019, 04:53:03 pm by McBryce »
 
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Online Performa01

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Re: The Siglent SDG2042X Thread
« Reply #1108 on: July 08, 2019, 06:11:53 pm »
I tried to search, but could not find an answer: is it possible to use one channel of SDG2042X as a modulation source for other channel without running a cable from its output to AUX input? If it is - what are the appropriate menu options to configure that?
No, it's not possible to use one channel as the modulation source for another without an external connection, nor is it required.

Whenever using modulation, you have a separate internal DDS modulation source for each channel, which provides all the standard waveforms including noise and arbitrary. So you have effectively two independent modulated channels, each with its own internal fully fledged modulation source.
 
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Offline n3mmr

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Re: The Siglent SDG2042X Thread
« Reply #1109 on: July 13, 2019, 08:39:16 pm »
Can an sdg2000x use a sinewave as an external clock source?
 

Offline rf-loop

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Re: The Siglent SDG2042X Thread
« Reply #1110 on: July 13, 2019, 11:11:22 pm »
Can an sdg2000x use a sinewave as an external clock source?

Yes.
If practice and theory is not equal it tells that used application of theory  is wrong or the theory itself is wrong.
It is much easier to think an apple fall to the ground than to think that the earth and the apple will begin to move toward each other and collide.
 

Offline n3mmr

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Re: The Siglent SDG2042X Thread
« Reply #1111 on: July 14, 2019, 03:02:45 am »
Can an sdg2000x use a sinewave as an external clock source?

Yes.

Is there any advantage or disadvantage to using sine or square wave?
 

Online Performa01

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Re: The Siglent SDG2042X Thread
« Reply #1112 on: July 14, 2019, 03:19:45 am »
Is there any advantage or disadvantage to using sine or square wave?
The answer depends on the internal architecture.

I haven't tried it on the Siglent SDG yet, but in most other cases (AWGs and RF-signal generators) high spectral purity and low phase noise of the output signal could only be achieved with a pure sine wave as reference signal in my experience. So my general rule is using the purest possible sinewave as reference for any form of signal generators, whereas a squarewave is fine for digital gear like frequency counters.
 
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Offline n3mmr

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Re: The Siglent SDG2042X Thread
« Reply #1113 on: July 14, 2019, 03:54:51 am »
Is there any advantage or disadvantage to using sine or square wave?
The answer depends on the internal architecture.

I haven't tried it on the Siglent SDG yet, but in most other cases (AWGs and RF-signal generators) high spectral purity and low phase noise of the output signal could only be achieved with a pure sine wave as reference signal in my experience. So my general rule is using the purest possible sinewave as reference for any form of signal generators, whereas a squarewave is fine for digital gear like frequency counters.

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Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #1114 on: July 14, 2019, 04:36:51 am »
Is there any advantage or disadvantage to using sine or square wave?
Square waves don't go well with transmission lines.  A single frequency sinusoidal is much easier to transmit cleanly.  The receiver can then schmitt trigger it and do whatever it needs to to phase lock a VCO to it.
 
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Offline bdunham7

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Re: The Siglent SDG2042X Thread
« Reply #1115 on: July 15, 2019, 07:54:03 am »
I have a simple question that I can't find answer to in the manual--how do you turn the modulation function OFF???  It seems that once on it stays on....
 

Offline JDubU

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Re: The Siglent SDG2042X Thread
« Reply #1116 on: July 15, 2019, 10:50:23 am »
I have a simple question that I can't find answer to in the manual--how do you turn the modulation function OFF???  It seems that once on it stays on....

Push the modulation button again.
 

Offline bdunham7

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Re: The Siglent SDG2042X Thread
« Reply #1117 on: July 15, 2019, 12:55:23 pm »
I have a simple question that I can't find answer to in the manual--how do you turn the modulation function OFF???  It seems that once on it stays on....

Push the modulation button again.

OK, I swear that wasn't working when I tried it.  But it does now!  I'll have to try and reproduce the issue and see if there's a bug.
 

Online ebastler

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Re: The Siglent SDG2042X Thread
« Reply #1118 on: July 15, 2019, 03:26:58 pm »
I haven't tried it on the Siglent SDG yet, but in most other cases (AWGs and RF-signal generators) high spectral purity and low phase noise of the output signal could only be achieved with a pure sine wave as reference signal in my experience. So my general rule is using the purest possible sinewave as reference for any form of signal generators, whereas a squarewave is fine for digital gear like frequency counters.

Is that really so? Today's function generators and AWGs are "digital gear" too. Do they really care about the harmonics in a square trigger signal, as long as the edges are well-defined?
 

Online Performa01

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Re: The Siglent SDG2042X Thread
« Reply #1119 on: July 15, 2019, 08:00:36 pm »
I haven't tried it on the Siglent SDG yet, but in most other cases (AWGs and RF-signal generators) high spectral purity and low phase noise of the output signal could only be achieved with a pure sine wave as reference signal in my experience. So my general rule is using the purest possible sinewave as reference for any form of signal generators, whereas a squarewave is fine for digital gear like frequency counters.

Is that really so? Today's function generators and AWGs are "digital gear" too. Do they really care about the harmonics in a square trigger signal, as long as the edges are well-defined?
You are right, it sounds odd and you would think it should not matter for a digital PLL.

The problem with square wave signals is that they usually come from some digital circuitry, where the propagation delay and switching times are not absolutely constant due to crosstalk and noise. This is why pure signals with low phase noise require a continuous (sine) wave reference rather than a switched (digital) signal with its unavoidable jitter components.

 
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Offline radiolistener

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Re: The Siglent SDG2042X Thread
« Reply #1120 on: July 16, 2019, 02:00:09 am »
The problem with square wave signals is that they usually come from some digital circuitry, where the propagation delay and switching times are not absolutely constant due to crosstalk and noise. This is why pure signals with low phase noise require a continuous (sine) wave reference rather than a switched (digital) signal with its unavoidable jitter components.

sine wave has slow slope, it means that slope will move through zero level very slowly and if there is any small amplitude noise, it will leads to jitter. Square wave has fast slope, so it moving through zero level very fast and small amplitude noise doesn't affects it much. Isn't it?
 

Online Performa01

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Re: The Siglent SDG2042X Thread
« Reply #1121 on: July 17, 2019, 11:39:09 pm »
sine wave has slow slope, it means that slope will move through zero level very slowly and if there is any small amplitude noise, it will leads to jitter. Square wave has fast slope, so it moving through zero level very fast and small amplitude noise doesn't affects it much. Isn't it?
That’s a valid objection for PLL systems using a digital phase detector (XOR gate or flipflop). But with analog phase detectors (double balanced mixer), a sine wave is certainly more suitable. That’s why I've initially stated that it depends on the architecture.

Devices for which phase noise isn't much of a concern, like DSOs or frequency counters, often have nothing more than a simple TTL level digital input for the reference clock.

Apart from that, the sine wave always has the advantage of avoiding RFI. A fast risetime square wave might leak into the instrument and even radiate through (lower cost) shielded cables, hence polluting not only the instrument it's connected to but the entire lab.

The only way to find the ultimate answer to what provides the cleaner output for a particular instrument is to try it out…
 

Offline n3mmr

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Re: The Siglent SDG2042X Thread
« Reply #1122 on: July 18, 2019, 07:11:29 pm »
The only way to find the ultimate answer to what provides the cleaner output for a particular instrument is to try it out…

Would you consider trying it out on an sdg2000x series unit?
 

Offline TurboTom

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Re: The Siglent SDG2042X Thread
« Reply #1123 on: July 18, 2019, 11:58:43 pm »
I can offer some measurements for the SDG6000X AWG.

To cut a long story short, for virtually all practical applications, the shape of the reference signal makes no difference.

For those who are interested in the boring details  ;), here's some more information on what I did:

I used my Rb frequency standard based on a LPRO101 oscillator that provides a very good sine, and my homebrewn buffer / square trigger circuitry, as a reference.

It provides a sine output level of +7dBm. Alternatively, I used the 5V TTL square output. Both outputs have an impedance of approx. 50 ohms.

This signal was fed directly to the REF input of the SDG6000X via an RG58 cable of approx. 90cm length without additional termination at the SDG end.

The SDG6000X was configured to provide a 10.1MHz sine on channel 1 to an SSA3000X spectrum analyzer which was running on its internal reference. I always did three measurements:

- Trace A external sine reference
- Trace B external square reference
- Trace C internal reference

The attached screenshots of the SSA are self-explanatory by the file names though not really interesting. No intermodulation or the like could be observed, the worst that happens is a slight coupling of the harmonics of the REF signal to the output in the frequency ranges of 50~250MHz and then a little stronger around 1GHz. Considering the "forest" of peaks the SDG6000X produces when running on the internal reference, and the absolute amplitude of this noise which is close to -90dBm (except the clock feedthrough at 2.4GHz which is more like -70dBm), it's not worth worrying about.

FYI, I also recorded a set of traces with the output disabled which almost didn't change a thing. In this screenshot, I also added a fourth trace (D) with the generator completely powered down.

A test with the modulation domain analyzer (sorry for the crappy photos...) revealed a very slight improvement of the jitter / phase noise (standard deviation) if a square wave is used as a reference signal. An external sine ref signal and the internal reference are on par to each other once the instument has reached thermal equilibrium (except for the absolute frequency accuracy of course).

If all this information is also valid for the SDG2000X series is something that I cannot answer. So maybe someone who owns this AWG and the additional required gear may want to repeat the tests?

Cheers,
Thomas


Edit: Messed up one of the MDA photos...
« Last Edit: July 19, 2019, 07:36:42 am by TurboTom »
 
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Online Performa01

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Re: The Siglent SDG2042X Thread
« Reply #1124 on: July 19, 2019, 01:25:50 am »
The only way to find the ultimate answer to what provides the cleaner output for a particular instrument is to try it out…

Would you consider trying it out on an sdg2000x series unit?
Sorry, I don't have an SDG2000X, but I'm pretty confident that the basic circuit architecture is the same as for the SDG6000X, hence Turbo Tom's results will be valid for the entire SDG-X product range, even for SDG1000X.

If I interpret the test results correctly, then the square wave exhibits sligthly more peak to peak jitter, a slightly tighter (better) phase noise spectrum and a few additional spurious signals, especially at higher frequencies - so for all practical purposes these instruments work well with both reference signal shapes.

I personally still prefer the clean sine for two reasons:
1. Even though the SDG-X don't care, some instruments might show nasty output spectra with a square reference.
2. Highly sensitive low noise instruments might actually be compromised by the harmonics/spurs of the square wave.
 


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