Gus,
Yes, it works, and phase is preserved if you use the same source for both the mix up and the mix down.
I tried a quick test with a NanoVNA-V2 and a couple of ZFM-4300 mixers. The NanoVNA-V2 swept 100 MHz to 900 MHz, and a 1 GHz LO mixed up and down to create a sweep from 1100 MHz to 1900 MHz. A tunable band pass filter responded as expected in that range, and the phase through the filter was stable. There was 12 dB or so of added loss from the mixers,
The biggest spurious responses were from the images, of course, with some minor responses due to limited RF-IF rejection of the mixers. You would want some filtering to limit the signals to your band of interest.
(I chose the frequencies to match the items I had on hand, but it should all scale up to 5 GHz)
--John Gord
toggle quoted message
Show quoted text
On Thu, May 14, 2020 at 03:46 PM, Gus Osborne wrote:
Hello all,
Think this is my first OP here - have a couple questions/thoughts I¡¯d like
to run by the group.
I¡¯ve ordered a couple of the SUP2400 satellite upconverters, with the
intention of modifying one to act as a 2.4Ghz down converter, like here:
I know this should work for my RX only SDR purposes (possibly even TX with
BladeRF) - but was also wondering about the feasibility of connecting one of
these modified ¡°downconverters¡± to CH1 on the S-A-A-2 (using an external
antenna and possibly some preamplification) in order to reach the 5.8Ghz band
for a ¡°poor mans¡± spectrum analysis tool. The primary use would be for
conducting quick and dirty site surveys.
My other thought, possibly even stranger - was using one in its default
configuration on CH0 to upconvert the tracking gen signal by 2.4Ghz (through a
DUT/bridge), then using the modified downconverter to receive output on CH1
for typical analysis. I¡¯m sure all bets would be off when it comes to phase
and possibly impedance.
Does anyone see an obvious reason this shouldn¡¯t work for simple purposes? I
understand it won¡¯t work nearly as well as a purpose built device; but will
it work? I¡¯m hoping the SAA2¡¯s usable 3.5Ghz + a 2.4Ghz conversion will
put me right were I need to be, for (somewhat crude) 5.2-5.8Ghz analysis.
Thoughts..?
