I have evaluated the “Wave Combine” feature in the SDG6052X and found that it is only useful at (very) low frequencies (Reply #460):
https://www.eevblog.com/forum/testgear/siglent-sdg6000-series-awg_s/msg5093877/#msg5093877Knowing the challenges in an AWG and the particular history of the SDG6000X, I thought it would be interesting how the SDG7102A would perform in this regard. This is not just a big brother of the SDG2000X series (like the SDG6000X actually is), but a very ambitious design right from the start.
For the SDG6052X, I have tested three different setups suitable for the full frequency range:
1. Resistive power combiner with two attenuators in the source paths from the generators.
2. Resistive power combiner with a single attenuator at its output.
3. Internal “Wave Combine” function with external attenuator.
The first setup tests the SA rather than the generator, so there’s no use to repeat it once again. That leaves the tests 2 and 3.
The attenuators in this test are 20dB. The big advantage of this arrangement is that we need not touch the generator settings (except for frequency) and get the exact same output levels. As a consequence, the spectrum analyzer always sees the same signal levels of about -30 dBm, which is the standard test level for intermodulation distortion in most spectrum analyzers.
I’ve tested 4 MHz and 400 MHz in order to get comparable results to the SDG6000X test, but have added a 900 MHz test to scratch the limits of the SDG7000A. As always, we expect the generator output buffer performance to degrade at higher frequencies. The 2nd tone is just 10 kHz above the first one. An automatic Intermodulation measurement has been used to get the results quickly and accurately.
Let’s start with a single attenuator at the output of the power splitter. The isolation between the two generator outputs is only 6 dB, so any non-linearity will show up pretty clearly.
Not a problem at 4 MHz:
SDG7102A_Ext_1x20dB_4MHz_-4dBm
Still not bad at 400 MHz (the SDG605X was at -58 dBc here, whereas the SDG7102A manages respectable -80 dBc.
SDG7102A_Ext_1x20dB_400MHz_-4dBm
Even at 900 MHz, the intermodulation distortion is very reasonable at -78 dBc.
SDG7102A_Ext_1x20dB_900MHz_-4dBm
Now let’s have a look at the internal wave combine function, 4 MHz at first:
SDG7102A_Int_1x20dB_4MHz_-4dBm
Once again the distortion is already significantly higher than with the external splitter – and it is even worse than the SDG6052X: -80 dBc, yet this might be still good enough for many tasks.
The truth gets revealed if we try to use the “Wave Combine” at high frequencies – first at 400 MHz. The result is not grat at -61 dBc, but certainly a lot better than the -38 dBc we got with the SDG 6052X.
SDG7102A_Int_1x20dB_400MHz_-4dBm
Finally the result for 900 MHz. At -57 dBc the distortion is still 19 dB better as the SDG6000X at just 400 MHz:
SDG7102A_Int_1x20dB_900MHz_-4dBm
Verdict: Even though the SDG7000A is significantly better than the SDG6000X, the internal “Wave Combine” feature is not really suitable for characterizing the distortion performance of highly linear test objects at higher frequencies.
Home
Help
Search
Login
Register
