Upcoming Rigol DSG815/830

[TurboTom]

I'ld rather think that Rigol simply didn't finish the I/Q add-on board at the time they first released the DSG800 series and had to create some cash flow to compensate for the design expenses of the project. The option to install an add-on I/Q board is clearly present on the early models and shown in Dave's DSG815 teardown, and hardware-wise, there's no indication that it wouldn't be operational.

Moreover, there's just a single firmware available for the whole range of instruments. I'ld rather say that after Rigol produced the initial batch of instruments, they quickly realized that the hardware is capable of more than initially anticipated, so they upped the bandwidth to 2.1GHz vs. 3.6GHz (of the 1.5G and 3G models, respectively) and finished the I/Q module and the accompanying firmware extensions. Shame that they don't offer the add-on as a separate option so users of the basic version can later on decide to upgrade to I/Q functionality.

[tv84]

Shame that they don't offer the add-on as a separate option so users of the basic version can later on decide to upgrade to I/Q functionality.

Yes but that is  also a factor behind my theory.

[TurboTom]

We can only know for sure after someone posts a detailed set of photos of a DSG800A teardown.

With the help of Rigol's spec sheet of the DSG800(A) I've been able to complete my flow scheme of the DSA815 of Dave's teardown (sorry for the "ill" choice of colours, some lables have to be magnified to be deciphered -- maybe I'll draw a block diagram to simplify understanding the signal flow). I added signal frequencies as far as possible.

Considering Rigol's preference of Hittite / Analog components, my best bet for the I/Q modulator they used on the add-on board would be the HMC1097. Unfortunately, Hittite's evaluation board for this chip isn't as complete to permit a direct use in the DSG since it requires differential I and Q signals. In order to achieve a good carrier suppression over the whole frequency range, it may also be necessary to adjust the I and Q bias levels depending on the LO frequency. So there probably is an additional look-up table stored soemwhere on Rigol's IQ add-on board. Likely just too much hassle for a DIY solution.

But there may be a real chance for a frequency upgrade... Seems like hardware-wise, evereything's already there.

[tv84]

But there may be a real chance for a frequency upgrade... Seems like hardware-wise, evereything's already there.

Nice work! 

[noreply]

OK noticed some other interesting parameters ....

001A - PLL              PLL         :SERVice:SET:BANDwidth:MODE:PLL
001B - DETect           DET         :SERVice:SET:BANDwidth:MODE:DETect
001C - MODulation       MOD         :SERVice:SET:BANDwidth:MODE:MODulation
001D - ALC              ALC         :SERVice:SET:BANDwidth:MODE:ALC

These are ONLY SET commands - so critical

BUT you can set the PLL BANDWITH - really stupid if Rigol has defined model independent of BW setting - possibly can set the 3.6GHz BW here??

Problem is there is no equivalent READ command - so we can see what the current setting is set at??

[TurboTom]

For those of you who are interested in the DSG800 operational details... 
I don't guarantee for 100% accuracy but the diagram should be fairly correct.

[TurboTom]

So here are a few remarks on the DSG815 (RF) hardware, looking at the block diagram I published yesterday:

It gets immediately obvious that Rigol's design is for the most part a simple "straight-through" approach. Since the main PLL oscillator covers a frequency range of 1:2 (1.82~3.64GHz), followed up by three by-two frequency dividers, the total frequency range is theoretically 1:16 (227.5MHz~3.64GHz) of which the range of 227.5MHz to 3.6GHz is used in the top-of-the-line model.

The lower range of 0~227.5MHz (okay, they start at 9kHz or the like, but for convenience I keep it "0"), the 910MHz signal that's available from the internal reference PLL divided by four, is mixed with the main PLL output divided by four (output range 910~682.5MHz), resulting in the required low frequency band as the difference. It's important to notice that now the control of the main PLL gets mirrored, i.e. all modulation schemes need to be mirrored as well (FM , PM and complex modulations will have to have the side bands reversed).

Another result of the straight-through approach is the necessity of a huge amount of filtering. In contrary to a full-range mixer approach with very high frequencies as input signals, say 5GHz fixed reference and 5~8.6GHz VFO to achieve a mixing product of 0~3.6GHz, where the sum and the mixer input signals are far away from the output signal range and the mixing product is fairly clean (if the mixer inputs were...), in this straight-through approach a lot of harmonics are generated due to the stacked dividers. To get this signal clean, a total of ten switchable low pass filters (plus a few that are doubled up) are required.

Since the filters can be arranged as distributed element configurations (for the upper end) and conventional passive filters, they are not really expensive. Most of the filter switching is accomplished by PIN diodes (HSMP-389B, now obsolete) which also isn't a driver for cost. The biggest advantage of this approach is that the highest frequency throughout the design is 3.64GHz, which may be just low enough to be able to use impedance-controlled FR4 as PCB material and not having to use more expensive and more difficult to process Rogers hybrid materials.

I didn't specifically address Rigol's modulation approaches (the two blocks that I identified as configurable band pass filters could also be amplitude modulators, utilizing HSMP-3832 PIN diodes, so bear with me...), but since the FPGA is controlling both the main PLL's reference clock and all the attenuators, it's well possible that these are the means for frequency, phase and amplitude modulation. The interface for complex modulation add-on circuitry is included in the signal path before the low-frequency band mixer. Still, this modulator will have to cover a very wide frequency range which is a considerable disadvantage of the straight-through approach.

There are two level detectors included in the design, one in front of the attenuator stack and one right at the output. The first one appears to be resposible for the level accuracy since it's heated and temperature stabilized. The second one is probably used as a protection monitor (in case RF is fed back into the output) and as a power monitor for higher output levels when the PA is used.

There is no reason that the entry level models of this instruments cannot be unlocked by software to cover the full frequency range unless on recent production models, part of the filters and switches aren't populated. But since these components really aren't ruining the bill, it would probably be less economical to run different production batches than having all the RF boards produced identically.

The DSG800 series is clearly built to a budget but I'ld still say that no real corners had been cut that would affect performance. The straight-through approach has also been utilized by other manufacturers, i.e. Dave's Marconi SG follows a similar route.

So much for that, if I'ld get my hands on a set of good photos of the "A" version torn down, I'll add some information on the I/Q modulator...

[noreply]

TurboTom,

Thank You so much for your very insightful observations and explanations 

A few questions, from a novices point of view ;-

1. Given Rigol's 'straight-through' approach - are there any inherent performance (i.e. better phase noise, smaller harmonics, etc, etc) advantages over the full-range mixer approach?
2. Did Siglent adopt a similar approach in their SSG3000x range? or the full-range mixer approach?
3. Are there inherent performance benefits of the full-range mixer approach - if so, what are they?

Thanks

[TurboTom]

TurboTom,

Thank You so much for your very insightful observations and explanations 

Thank you very much for your kind words 

A few questions, from a novices point of view ;-

1. Given Rigol's 'straight-through' approach - are there any inherent performance (i.e. better phase noise, smaller harmonics, etc, etc) advantages over the full-range mixer approach?

Actually, there are: Provided the same "care" is taken designing an oscillator for the fundamental frequency or one for a higher frequency suitable for mixing, the phase noise would be better for the straight-through approach. Dividing the fundamental frequency to provide the lower bands would further improve the phase noise. Rigol provided a factor "N" in their frequency band table which actually resembles the reciprocal divisor by which the LO frequency is divided to provide the configured output frequency. If a mixing approach is taken to produce the desired frequency, the resulting phase noise will be the geometrical sum of the phase noise of the two frequencies to be mixed, whereas it scales with the "N" factor in case a straight-through approach is utilized. You've got to be aware that the lowest band of the DSG800 utilizes the VFO to be divided by four and then mixed with the 3.64GHz reference divided by four, which results in a worse phase noise than Band 2 which is generated form the VFO divided by eight (see Rigol's table).

2. Did Siglent adopt a similar approach in their SSG3000x range? or the full-range mixer approach?

Sorry, I cannot answer this question exactly since I don't know of a complete tear-down of one of Siglent's SSG3000's RF modules. But the specs of the SSG3000X make me believe that Siglent had a very thorough look at Rigol's design when they started work on their generator... Yet the second lowest frequency band is the mixing product of the VFO divided by two, so provided the phase noise of the VFO of these two specimen is similar, Siglent's approach will be inferior (for whatever reason, Siglent splits the "mixed" frequency range into two, first 9kHz~1Mhz with "N" = 0.25 and the second 1~250MHz with "N" = 0.5).

3. Are there inherent performance benefits of the full-range mixer approach - if so, what are they?

Thanks

There are a some benefits of the full-range mixer approach: Provided the mixing partners, i.e. local reference and VFO frequencies are sufficiently "clean", the amount of filtering / filter switching required to provide a sufficiently "clean" output signal is reduced considerably. It basically reverts to an LPF suitable to block the sum frequency and the feed-through of the individual mixing partners. Modulation may also be easier since everything can be accomplished at a single frequency (the internal reference). Albeit, this frequency is much higher than in case of the "straight-through" approach, so the semiconductors required may be more expensive.

Edit: Forgot to mention another substantial advantage of the full-range mixer approach: Since range switching isn't required, signal generators following this approach will be capable of seamless frequecy sweeps over large ranges without dropouts or "phase hickups" which unavoidably will result during range-switching of a straight-through SG. Same situation for (ultra) wide-band FM, if your carrier is right on the edge of a band.

I hope this answers your questions so far.

All the best,
Thomas

[noreply]

Thank you once again for great explanation.

Yes - looking through the specifications for both the DGS800A series and the SSG3000X series - Rigol has slightly better phase noise figure quoted - from memory it was  -112 dBc/Hz typical to Siglent's  -110 dBc/Hz

[tv84]

Looks like I got a different version of the firmware file. For example the size of DoryApplication.sim is 0x2b7be4 in mine.

Chicken, I've placed renewed parsings in the previous msg. 

Check to see if you have a different FW from the ones I have. If yes, I would be interested in getting that one also.

I wasn't aware of that thread. The only difference is :SYSTem:PRESet (620, 0x4016cdd8, :SYSTem:PRESet, Programming Guide) which is missing in your list.

Thanks, this allowed me to correct a rare bug. You could correct your command IDs. It's not the int16 that you assumed (see my list).

[chicken]

Chicken, I've placed renewed parsings in the previous msg. 

Check to see if you have a different FW from the ones I have. If yes, I would be interested in getting that one also.

Judging from offset and size of DoryApplication.sim, your 00.01.06.00.01 FW file is the same as mine.

Thanks, this allowed me to correct a rare bug. You could correct your command IDs. It's not the int16 that you assumed (see my list).

Are you referring to the ID column in my list? It's the index of the SCPI command structure in the command tree array, not the int16 field that references the array of function pointers. IIRC there are "inert" entries to build the hierarchy. But I agree, your numbering based on function index makes more sense.

[tv84]

PS: And here my notes about loading extracted firmware binaries with Ghidra and radare2

A practical way that I use to load a IAR file in IDA Pro is using 0x3FFFFF94 as the loading address (attached).

[Sighound36]

Norepy

From this thread I take you have have bot the Rigol and Siglent offerings on test currently, so what are you conclusions thus far or is the jury still out?

[noreply]

Norepy

From this thread I take you have have bot the Rigol and Siglent offerings on test currently, so what are you conclusions thus far or is the jury still out?

Currently only the 815 - no stock on the Siglent when review started - but should be getting the Siglent shortly.

So far, I like the 815 - it 'does what's written on the tin' as the saying goes.

I have been using this for testing RF power amplifiers (as input source) and the signal(s) are extremely clean out of the RF Amplifier(s).

As you know, if you put 'crap' into an Amplifier - it WILL amplify your 'crap' - given that there are absolutely clean signal(s) out of the Amp is a good indication.

I would like a 'touch screen' (spoiled by the SVA and MSO5000) - but the 815 has a functional system - it takes a while to get used to the menu structure - but its possible to make all the setting you need - but sometimes many key presses.

I like the compact size - big bonus - can bring very close to DUT and have 'short' leads.

The 815 'looks' dated , I think it was loosely based on the R&S SM300 from a form factor point of view - a tribute to R&S - as their device was last revised in 2007 - and it still has better specs than Rigol and the Siglent offerings.

What I noticed, is  that there is no Square Wave output on the 815 - other than on the LF output (BNC) and only up to 20KHz.

Not sure if its same on the Siglent at this moment in time?

I can understand that there is no great desire for Square Waves when working with RF (and a digital DAC based signal generator can suffice at a much lower cost) but in my 'one off' case , I was looking for a ULTRA FAST  edge in a signal - I guess this is where the 'pulse mode' comes into play. This is my next area of testing , so will report soon.

On the 815, this is an option (I think the Siglent has this feature as standard offering - correct me if wrong) so at the moment its on 'trial' mode until time runs out.

Modulation works well on the 815, I have been able to successfully modulate FM carrier(s) with various tones and soon full Stereo Encoding with RDS - to check all the pilot frequencies in receiver tests.

I am hoping to do a 'full report' - side by side of the main features from a user's perspective - as soon as I get the Siglent unit and do some similar testing which I made with the 815.

My only negative for the 815 at this moment is that there is no 'hack' to enhance the device - because if it can be enhanced to the 3.6GHz variant - it will kill the Siglent from a price / performance - without a doubt!

Let's face it, most people here don't want to shell out big $$$ on an option which is already 'inside' the device you purchased - just awaiting an activation code?

This is why I think 'hackability' is a big factor when deciding to purchase.

At the moment the score is ;-

DSG815 = 0
SSG3021Z=1

BUT, if and when DSG815=1 - the Siglent will have to drop its price by a mile as the price / performance ratio of the Rigol will kill it for sure.

Like most RF Signal Generator customers TODAY, having a device limited to 1.5GHz is a deal breaker - unless you are ONLY going to be working within this frequency limit.

With 2.4GHz, 5GHz and even higher RF devices being the norm today - you really need to have the higher frequency capability - especially if you are going to drop >$3000 for a RF Signal Generator.

This makes me think that even the Rigol's 3.6GHz  and Siglent's 3.2GHz offerings are already dated.

But, and a big BUT, there are already RF Signal Generators which cover the higher frequencies and modern digital modulation protocols out on the market but  unfortunately they cost lots of $$$.

This is why for the majority of 'us' its the Rigol and Siglent offerings (even if dated) that are really affordable at the moment.

From a price performance point of view , Rigol and Siglent will always be behind the Agilent and R&S offerings - which will be beyond the budget of most people like myself (and possibly others in this forum) - and because Rigol and Siglent choose to be in this market sector we can benefit by having an affordable access to instruments which can be 'enhanced' to make them even more desirable for the price / performance they offer.

[Sighound36]

Indeed, costing is the issue especially with 5Ghz the minimum requirement for IoT development now. IQ mod is going to more important now as are custom wave form generations. Stability and low phase noise to are more preferable for many I suspect. Understand wishing to maximize your potential purchasing power as we all do. Sometime they will be a null spot and your not quite able to use the normal route. Personally I would look for a good Agilent VSA which will set you back around the same cost as a basic 3.2Ghz version. I now have two of them, one is 4Ghz with the OXCO, six hardware upgrades and a few sw options its not small but its decent cost less than the model you are looking at right now. The second unit I did pay more for but its 10Ghz.

Consider a sighound VSG60 amplitude accuracy is incidental, and phase noise looks good for the cost, compared to Rigol or Siglant not sure at what frequency the phase noise is measured?

https://signalhound.com/products/vsg60a-6-ghz-vector-signal-generator/

https://www.testequipmenthq.com/product/keysight-e4422b

https://www.testequipmenthq.com/product/keysight-e4428c

https://www.keysight.com/gb/en/assets/7018-02994/data-sheets/5990-8116.pdf

https://www.testequipmenthq.com/product/aeroflex-ifr-marconi-2026q

https://www.testequipmenthq.com/product/aeroflex-ifr-marconi-2032

https://www.testequipmenthq.com/product/rohde-schwarz-smj100a

[tautech]

I would like a 'touch screen

SSG3000X offers touch and mouse control.

What I noticed, is  that there is no Square Wave output on the 815 - other than on the LF output (BNC) and only up to 20KHz.
Not sure if its same on the Siglent at this moment in time?

The LF modulation section in SSG3kX is rated thus:
Sine wave 0.1 Hz~1 MHz
Square wave, triangle, saw-tooth 0.1 Hz~20 kHz

I can understand that there is no great desire for Square Waves when working with RF (and a digital DAC based signal generator can suffice at a much lower cost) but in my 'one off' case , I was looking for a ULTRA FAST  edge in a signal - I guess this is where the 'pulse mode' comes into play. This is my next area of testing , so will report soon.

On the 815, this is an option (I think the Siglent has this feature as standard offering - correct me if wrong) so at the moment its on 'trial' mode until time runs out.

IIRC same for SSG3kX and have it enabled in my unit if there's anything you want to see.

With 2.4GHz, 5GHz and even higher RF devices being the norm today - you really need to have the higher frequency capability - especially if you are going to drop >$3000 for a RF Signal Generator.

This makes me think that even the Rigol's 3.6GHz  and Siglent's 3.2GHz offerings are already dated.

But, and a big BUT, there are already RF Signal Generators which cover the higher frequencies and modern digital modulation protocols out on the market but  unfortunately they cost lots of $$$.

This is why for the majority of 'us' its the Rigol and Siglent offerings (even if dated) that are really affordable at the moment.

The newer range of SSG5000X RF gens go to 6 GHz but yes these are getting really pricey. 

[noreply]

Rigol DSG815 – FM Modulation Test


Just a few screen shots of some simple FM modulation testing


The modulated signal quality from the DSG815 is nice and clean


I dropped the resolution BW on the SVA to get some ‘clean’ plots


See attached images

(Sorry, when I performed the testing I did not figure out how to do a screen shot on the 815 - so used the next best thing - camara)

[noreply]

Just posted some results & a 'how-to' testing Frequency Accuracy for the Rigol DSG815 with a GPSDO 10MHz reference and any oscilloscope capable of X-Y ploting.

Here is the link

https://www.eevblog.com/forum/testgear/rigol-dsg815-testing-feedback-and-comments/msg3147430/#msg3147430

Hope its of interest to those visiting this thread 

[tv84]

Looking just at the FW side, I think it's possible to convert a DSG815 into a DSG830...

[noreply]

Its interesting to know that there might be mileage in enhancing the DSG815 

Despite it being released back in 2015 - its still a decent bit of Kit - especially when compared to the more recent Siglent offering of their SSG3000X range.

There is another thread - specifically for the review of the SSG3021X - but during the 'testing' - it had been constantly compared to the DSG815 - so for those following this thread - please hop over to here (last post as of today)

https://www.eevblog.com/forum/testgear/siglent-ssg3021x-testing-feedback-and-comments/msg3161586/#msg3161586

and review the findings on the DSG815 - quite a few tests have been made - the latest is a full FM stereo & RDS modulation on 108MHz (via EXT Modulation Input) - to test, tune or align any FM / RDS capable FM radio. 

[tv84]

It has 4 Options (last 2 of them require additional HW).

PUM
PUG
IQ
OCXO

The licenses to enable them are similar to what rigup creates. The FW contains default ECC public and XXTEA keys but allows the use of specific ones.

If anyone can make a memdump, we can have a dry run.   

[chicken]

If anyone can make a memdump, we can have a dry run.   

What's the procedure for a memdump? I may give it a try.

[noreply]

If anyone can make a memdump, we can have a dry run.   

What's the procedure for a memdump? I may give it a try.

From my understanding - easiest way is to use a Jtag cable - to your PC and access the console
Dave's teardown video clearly shows the Jtag connector - its on the CPU board.

I think once the memdump is available then we can investigate 

[chicken]

Here's how to enter FACTORY and MANAGER/REPAIR modes:

Prepare a USB stick:
1. Format as FAT32
3. Write the following string to disc sector 3 of the USB stick (I used HxD):
35O8O228OLO8LNMN9690217963MN2O9ON46O9P05975K0047

Plug USB stick into the RF generator

Now the following SCPI commands will work:
:PRIV:SOFT:MODE 0,FACTORYMODEENTRANCE
:PRIV:SOFT:MODE 0,REPAIRMODEENTRANCE
:PRIV:SOFT:MODE 0,MANAGERMODEENTRANCE

The first parameter (0) seems to be ignored.
MANAGER and REPAIR seem to be identical, but entering REPAIR doesn't require the USB stick.

The current mode can be verified with:
:PRIV:SOFT:MODE?

To return to USER mode, power cycle the device or use
:PRIV:SOFT:MODE 0,USERMODEENTRANCE
or
:PRIV:SOFT:MODE 0,EXITCURRENTMODE

Additional menus show up when in FACTORY/REPAIR/MANAGER mode:
Syst > Service
Syst > Service > Calibration
Syst > Service > RF DataSyn
Syst > License > Delete

I haven't dared to mess with settings in factory mode yet (like changing the model to DSG830). Don't blame me if you break your RF generator 

And a little mystery: When triggering the check of the disk sector, an empty file with the name "LqepdclquJ.txt" is created on the USB stick.