I am looking for a “dynamic signal analyzer” with extended bandwidth (“DC” to approx. 10MHz). This will be used during experimentation with analog front ends for optical sensors (mainly interested in noise and FFT of the modulated light). Signals of interest are typically small (1mV <>100mV), but sometimes also riding on “large” DC (+-15V). I would like to have input ranges that go down to around -40dBVrms (10mV), and still have a good noise floor (-80dbFs preferred). Input impedance 1M to prevent loading of the DUT. Budget is around 1500€ but stretchable . I prefer more modern instruments, but off course considering my budget, I will need to make compromises somewhere...
This is my list of possible options I found so far:
1) Dynamic signal analyzer + spectrum analyzerMost (affordable) spectrum analyzers start only somewhere around 9 KHz. I could use one of these combined with an older dynamic signal analyzer like an HP 35665A, but these are huge, quite old and go still for quite some money. Also it is annoying to have to use 2 unit for the range I am interested in. Most spectrum analyzers will need some kind of active probe for the higher input impedance required (could be something homebrew because it only needs to go up to 10MHz). Not the most practical solution. I already have a CMU200, so the additional range offered by the spectrum analyzer is of no real interest.
2) USB Spectrum Analyzer: Signal Hound sa44b covers” the range I am interested in as it goes from 1 Hz to 4.4GHz, I am however unsure if no compromises were are made at the low end to go up this high. The datasheet does not specify a lot. Needs the (homebrew) active probe and a DC block. Unsure about the performance for my goals.
3) High Resolution ScopeAn alternative could be the
picoscope 4262 . This one is a little low on bandwidth, but so far seems like a reasonable solution. It does seem quite expensive for what it only offers. If bandwidth would be a little higher, this was a winner. The picoscope 5000 series also claim 16 bit of resolution, but their noise specs are much worse.
4)
HP 89410-89441A (with or without RF-downconverter)
This seems like a good solution for what I need. Disadvantages are they are very big and heavy, which makes importing them from the US to Belgium very expensive . In Europe they do not seem to be common, and if they appear on Ebay, they are way overpriced. They are typically quite old (1994-98), and there seems to be a common problem with the corners of the screen getting quite dim (there is a VGA port available however). Temped by this solution also as it also offers network analyzer capabilities if the second channel is installed.
Any advice, tips, other units to consider?
Edit: added hyperlinks to specification datasheets