<whitequark>
except for the microstrip inanity this thing is very simple actually
<whitequark>
the very thin conductors complete DC circuits
<whitequark>
the "transistor" is not quite just a transistor, it's an MMIC
<whitequark>
basically a transistor with an integrated bias circuit
<whitequark>
specifically for heterodyne resonators like this one
<DocScrutinizer05>
aaah
<DocScrutinizer05>
I guess BAV99 is rather envelope demod
<whitequark>
BAV99 is just to protect the microwave diode. it has a Vbrkdn of a few V
<DocScrutinizer05>
and what they call "IF" is actually the demodulated interference aka beat product
<whitequark>
yeah
<whitequark>
the "demodulation" (not sure if you can call it so) is the usual result of mixing transmitted with received
<whitequark>
where received would shift by a few Hz due to doppler, and you'll get a signal with those few Hz to the left of microwave diode
<DocScrutinizer05>
right
<whitequark>
(it's not really... modulating anything, it just transmits baseband and looks for shift)
<DocScrutinizer05>
ring modulator
<whitequark>
right
<DocScrutinizer05>
f1 * f2
<DocScrutinizer05>
where f1/2 are signals, not frequencies
<DocScrutinizer05>
resulting in f1+f2 and f1-f2, this time frequencies of the signals
<DocScrutinizer05>
f1-f2 is what we're interested in here. No demod needed
<whitequark>
exactly
<DocScrutinizer05>
I gather the 1202 upper left is a capacitor?
<DocScrutinizer05>
to DC-decouple the IF out signal
<whitequark>
resistor
<whitequark>
it's a pulldown
<whitequark>
the IF signal is not DC balanced :D
<whitequark>
I mean... there's nothing special about these lumped components. the numbered ones are bog standard SMD resistors
<DocScrutinizer05>
hmm, ok
<whitequark>
the white ceramic thing is a DC block capacitor
<whitequark>
again to protect the microwave diode
<DocScrutinizer05>
so the whole ring modulator works completely passive?
<DocScrutinizer05>
I.E. no power supply?
<whitequark>
yes
<DocScrutinizer05>
DC power
<DocScrutinizer05>
wow
<whitequark>
the only powered thing here is the oscillator
<DocScrutinizer05>
:-)
<DocScrutinizer05>
as simplistic as it gets
<whitequark>
it works pretty well despite that
<DocScrutinizer05>
amazing
<DocScrutinizer05>
mere voodoo ;-D
<whitequark>
detects my hand with hundreds of mV on the IF output, if within 50cm
<whitequark>
datasheet says up to 20m, I think it will be able to detect large metal like cars in that range
<whitequark>
but not people
<DocScrutinizer05>
ooh, 50cm - yes that's sort of easy
<DocScrutinizer05>
20m is absolutely non-trivial
<DocScrutinizer05>
considering the signal levels on RX
<DocScrutinizer05>
I'm instantly thinking of automatic doors where approaching person needs to get detected in ~2..3m distance, which prolly is what those critters are used for in 99% of installations
<whitequark>
that is exactly what the description said
<DocScrutinizer05>
did they tell anything about directivity of antenna and about how to mount that thing?
<DocScrutinizer05>
like "15mm above a metal surface"
<DocScrutinizer05>
or whatever
<whitequark>
nope
<DocScrutinizer05>
:-P
<whitequark>
it's fairly directional
<DocScrutinizer05>
I nevertheless guess it would be a good idea to mount it in that way, with the device surface pointing at sensor range
<DocScrutinizer05>
you could link the rigol directly to your PC ethernet jack, not even a crossover patch cable needed with contenptorary NICs that do autodetect
<DocScrutinizer05>
honestly, rigol-snapshot is cooool
<whitequark>
I don't have an ethernet jack in my PC :D
<DocScrutinizer05>
and a 1000 times more convenient than even the USB hookup to PC
<DocScrutinizer05>
wow!
<whitequark>
it's one of the thin ultrabooks, they're too thin for that
<DocScrutinizer05>
err
<DocScrutinizer05>
USB-attached NIC then?
<whitequark>
I have the USB thingy but it's just annoying to use
<whitequark>
for occasional use I prefer just the USB drive
<whitequark>
it's permanently plugged into the scope
<DocScrutinizer05>
yeah, I had that too
<whitequark>
except when extracting data
<DocScrutinizer05>
but the unplugging and plugging to PC and copying of files is a PITA
<DocScrutinizer05>
I wouldn't pierce nails into that cat6 flat cables
<whitequark>
definitely
<whitequark>
does conrad.de even ship to RU?
<whitequark>
I don't know of any remailer in DE
<DocScrutinizer05>
I could, if you don't mind
<whitequark>
hm
<DocScrutinizer05>
dunno about conrad
<whitequark>
that'd work
<whitequark>
on a second thought I'm going to move in a few months hopefully
<whitequark>
so probably no point now
<whitequark>
unless the flat I'm going to rent has an equivalently shitty layout (hopefully not)
<DocScrutinizer05>
aaaw
<DocScrutinizer05>
take nice things like that cable with you when you move ;-)
<DocScrutinizer05>
you can use it again, for sure
<whitequark>
well... could be
<DocScrutinizer05>
anyway, I *strongly* recommend ethernet for Rigol, and when you actually would make up your mind to get decent ethernet and want that cable, just drop me a note with exact instructions how to send
<DocScrutinizer05>
but seems to work, well, usually. Though I didn't verify the results yet
<DocScrutinizer05>
anyway a downloaded waveform should be sufficient input data for anything like sigrok
<DocScrutinizer05>
you're welcome to "upstream" any improvements you make, e.g. regarding buffer depth configured in Rigol (script assumes 24M) ;-)
<whitequark>
sigrok is more than just waveform viewer, it can do stuff like infinite capture
<whitequark>
and configuring the scope
<DocScrutinizer05>
which prolly won't work with DS1000
<whitequark>
which is the reason to use it
<whitequark>
the SCPI or whatever commands are there
<DocScrutinizer05>
it can't download waveforms realtime
<whitequark>
hm
<DocScrutinizer05>
only when stopped
<whitequark>
oops
<DocScrutinizer05>
at least afaik
<DocScrutinizer05>
even screen snapshots take 3 times as long when running than when stopped. So in my book it's a hw (bus bandwith) limitation
<DocScrutinizer05>
quite possibly the ASIC that does all the heavy lifting is hooked up to the communications processor with a flimsy I2C or whatever
<DocScrutinizer05>
and the ASIC is not made for doing concurrent communications to processor and same time capturing
<whitequark>
sounds about right
<whitequark>
is it even an ASIC?
<DocScrutinizer05>
wild guessing, but sort of educated
<DocScrutinizer05>
yep, afaik it is
<DocScrutinizer05>
I once scrutinized a photo "DS1054 internals"
<DocScrutinizer05>
prolly on eevblog?
<DocScrutinizer05>
also somebody in that context said sth like "the bandwidth linit on the 50MHz devices is implemented by a simple switchable RC filter in the ASIC's inputs - this is how you enable DS1104"
<DocScrutinizer05>
which on second thought makes questionable sense since the DS1000 has a well known dedicated discrete ADC chip. But only one, not 4, and it needs prescalers/amps anyway, which might be part of the ASIC as well
<DocScrutinizer05>
anyway once you look at DS1000 screen with that info and from this perspective, you can virtually *see* how messages like "USB connected" etc are sent as bitmap from comm cpu to asic via I2C, for the asic to superimpose them into the display
<whitequark>
gross
<DocScrutinizer05>
considering reaction times I wonder how much of stuff like FFT, RS232 decoding etc is done on comm processor as well
<DocScrutinizer05>
the low price of the DS1000 is made possible only by very nifty software exploiting the available hw resources to the limit
<DocScrutinizer05>
you have a relatively simple ASIC doing the samplig and transcoding sample buffer into a display waveform and raster image, and you got a loosely linked auxiliary processor handling all the switches and communication at large, and also doing the more fancy stuff that includes lots of math or for example the help function etc
<DocScrutinizer05>
note how all messages like "function rate limited" or whatever look alike and look awful compared to usual display
<DocScrutinizer05>
err "Paramater limited!"
<DocScrutinizer05>
and how it akes 400ms between you turning the Y-sensitivity knob "beyond the limit" and the "Parameter linited!" showing up on display
<DocScrutinizer05>
takes*
<DocScrutinizer05>
sure the asic has some ALU to do for example the left/bottom side value display
<DocScrutinizer05>
"Vpp=..." etc
<DocScrutinizer05>
also I guess triggering is supported by that ASIC ALU
<DocScrutinizer05>
while the whole menu display, RS232 decoding, FFT etc is done on the aux CPU
<DocScrutinizer05>
it even seems to me that for unknown reasons all display elements coming from aux CPU are mainly B&W while ASIC is more colorful. I have no real good explanation for that yet
<DocScrutinizer05>
possibly a hw limitation in compositor
<DocScrutinizer05>
"compositor" I meant the stuff in ASIC doing overlay of data (from aux CPU, e.g. menus) over the display created locally (the colorful waveform and stuff)
<DocScrutinizer05>
then otoh those menus have a blue highlight, which voids such explanation
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