| Products > Test Equipment |
| Two Tone Test with Scope and SA |
| << < (6/33) > >> |
| mawyatt:
--- Quote from: David Hess on August 01, 2020, 02:58:13 am --- --- Quote from: mawyatt on July 31, 2020, 09:32:48 pm --- --- Quote from: PeDre on July 31, 2020, 07:52:46 pm ---I'm not sure I did everything right. I combined the two signals from the generator with a T-piece and terminated them with 50 Ohm on the oscilloscope. --- End quote --- Think you want to resistively combine the two sources for the tones unless you can combine them internally like the Siglent. A resistive "T" should work, think this has 16.7 series ohms on each leg to maintain 50 ohms on all three ports. --- End quote --- You have to be very careful combining the signals because the output amplifiers of the signal generators will produce the same distortion products that you are testing for if they are driven with the other signal. Ideally a combiner which provides isolation between the input ports is required but it is usually sufficient to pad each output with an attenuator and use minimum loss resistive divider. --- End quote --- That's why you want to look at this with a SA, to see if the AWG is causing any self-generated IMD issues when resistively combined outputs, if so then add some pads. The Siglent AWG has this nice feature where the two tone combining is done internally (digitally I suspect). Best, |
| TheSteve:
Keysight 33522B generating 10 kHz and 10.1 kHz @ 1 VPP, combined via resistive network, 50 ohms everywhere. FFT on Keysight MSOX3024T and SA on Keysight N9918A(20 dB external atten used here, also at the very bottom of its freq range). Same test repeated at 10 MHz and 10.1 MHz: |
| mawyatt:
--- Quote from: PeDre on August 01, 2020, 09:07:48 am ---I have now combined the signals with 16 ohm resistors on a breadboard, and again terminated with 50 ohm. The spectrum analyzer measures 10 dBm for one tone, the oscilloscope measures 1 Volt peak. Attached are the measurements for 10 kHz, 100 kHz, 1 MHz and 10 MHz. FFT is normal this time, without Max Hold. The small values jump a little bit up and down around 1 dB. Generator Rigol DG4162 Oscilloscope R&S RTB2004 (200 MHz BW) Spectrum Analyzer Rigol DSA815 (with external 20 dB Attenuator) --- End quote --- This shows off the R&S true 10 bit ADC, nice results!! Best, |
| mawyatt:
--- Quote from: TheSteve on August 01, 2020, 06:35:29 am ---Keysight 33522B generating 10 kHz and 10.1 kHz @ 1 VPP, combined via resistive network, 50 ohms everywhere. FFT on Keysight MSOX3024T and SA on Keysight N9918A(20 dB external atten used here, also at the very bottom of its freq range). Same test repeated at 10 MHz and 10.1 MHz: --- End quote --- The scope results are interesting, they don't show the 2F1-F2 & 2F2-F1 3rd Order IMD products, or they are buried in the noise floor. Seems Keysight is getting more performance out of the 8 bit 5GSPS ADC than I would expect, maybe some sort of manipulation to extend the apparent ADC resolution? Anyway, very nice result for a very nice scope!! Best, |
| mawyatt:
--- Quote from: PeDre on August 01, 2020, 02:07:56 pm ---And here the Rigol DS1104Z and MSO2302A. I haven't managed to get better settings. The DS1104Z FFT uses the memory, not the screen as source. --- End quote --- You need a longer time span to separate these two tones. Best, |
| Navigation |
| Message Index |
| Next page |
| Previous page |