Frequency down converter to extend scope's range - Page 1
Forum section: electronics / testgear

author: petert
author_rank: Regular Contributor
timestamp: May 02, 2020, 03:55:55 pm
content: Hi,Many SDRs use a frequency up-converter to extend the range to lower frequencies.Are there down-converters, such that you could look at higher frequencies (maybe up to 500 MHz), though your scope is limited to 100 MHz?

author: joeqsmith
author_rank: Super Contributor
timestamp: May 02, 2020, 05:39:10 pm
content: I'm not sure out side of buying a faster scope. I made something like this many years ago, using a flash converter to capture the waveform then playing the wave back at a slower rate. Basically, this is designing the whole scope less the display. Now days, making something like this vs just buying a faster scope makes little sense.

author: james_s
author_rank: Super Contributor
timestamp: May 02, 2020, 05:56:52 pm
content: It's not possible to convert the frequency while maintaining the original shape of the signal. Since the purpose of a scope is to see the shape of the signal that wouldn't do you much good.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 02, 2020, 06:21:43 pm
content: Quote from: james_s on May 02, 2020, 05:56:52 pmThis. A mixer will downconvert the content just fine, but it's not possible to get the whole bandwidth of a 500MHz input into a 100MHz scope that way - you'd just get the 100MHz worth you select of that 500MHz based on your chosen LO frequency, so while you could use a 100MHz scope to capture an 80MHz channel's data waveform with a downconverting mixer (and this is done), you're throwing away all the frequency content outside of the bandwidth of the scope, so the resulting waveform won't look like it would when captured at full bandwidth.The reason radio applications can do this is because the information content of the signal is centered around a specific frequency, so when you downconvert from this frequency, you move the entire signal of interest into the lower band and with some filtering you can directly digitize it. Since a scope is a broadband instrument interested in all of the frequency content of the signal, it wouldn't really be valid for normal scope operation and use cases to just downconvert as it wouldn't represent the signal present at the 'input'.

author: ogden
author_rank: Super Contributor
timestamp: May 02, 2020, 07:26:45 pm
content: Depending on how good (FFT) spectrum display mode of scope is, one can make it poor man's spectrum analyzer. At least for narrowband ISM applications.

author: tonyalbus
author_rank: Super Contributor
timestamp: May 02, 2020, 07:33:34 pm
content: i dont trhink you can do that for a scope, it is usualy done for frequentie counters and its calles a preselector if i am correct.for a scope you want to keep the shape, for a frequency counter its just a pult to count, what even shape.Tony

author: ogden
author_rank: Super Contributor
timestamp: May 02, 2020, 08:06:03 pm
content: Quote from: tonyalbus on May 02, 2020, 07:33:34 pmIt's prescaler. Other name - divider. Do not apply here in this discussion because completely different thing than frequency downconverter. Preselector is bandpass filter right after antenna - if we talk about RF receivers.Yes indeed you can do frequency downconverion for scope - yet you shall know what you are looking at. For example if we take 866 MHz signal with 1KHz deviation and downcovert it into 100KHz "IF" frequency, it will still have 1KHz deviation. Using FFT function of the scope we essantially will look at spectrum of "downconverted" TX signal. That could be useful for those who do not have spectrum analyzer on hand. So idea is not that bad actually. Poor man's spectrum analyzer so to say.

author: petert
author_rank: Regular Contributor
timestamp: May 03, 2020, 07:32:14 am
content: Quote from: DaJMasta on May 02, 2020, 06:21:43 pmI know that I would still have a limited bandwidth of 100MHz just like an SDR. It would still be helpful when analyzing radio signals and looking at generated waveforms of transmitters.Is there a downconverter like this?

author: ogden
author_rank: Super Contributor
timestamp: May 03, 2020, 08:16:45 am
content: Quote from: petert on May 03, 2020, 07:32:14 amIt is already said that after downconversion you do not see generated waveform. Downconverted signal has same modulation properties like phase and/or frequency variation, but it is not original waveform anymore!QuoteYes. Inside many superheterodyne radios. Usually they are narrowband. In case you want to build one, check ali/*bay for "35-4400MHz USB Simple Spectrum Analyzer RF Signal Source". It has LO and mixer inside, thou (again) low freq and narrowband IF. It is not that hard to tap mixer output, introduce own IF filter and amplifier. Oh, and you need preselector filter as well. Search internet for HAM bandscope or panadapter mod. Radio amateurs are using their receivers as downconverters to look at receive spectrum at IF tap. They use SDR for that, but you may use FFT of your scope as well.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 03, 2020, 09:22:00 am
content: It can be, and had been done.Not all signals have a bandwidth extending from zero frequency to whatever the maximum frequency of interest is.Many, although quite wideband, are centred around a much higher frequency, which cannot be seen by theoscilloscope.Wideband down conversion can allow you to look at a segment of the specrum, but in the time domain.Test receivers for analog TV can demodulate say, a 500MHz signal so you can look at tne baseband video signals, or have an IF output, where you can observe the modulation envelope at around 30-odd MHz.Even though these are not "general purpose" 'scope uses, they are legitimate ones.

author: Andreas
author_rank: Super Contributor
timestamp: May 03, 2020, 09:42:49 am
content: Quote from: petert on May 02, 2020, 03:55:55 pmThat is exactly what sampling oscilloscopes are doing:DIY example for a sound card here:https://www.analog.com/en/analog-dialogue/articles/turning-pc-sound-card-into-sampling-oscilloscope.htmlwith best regardsAndreas

author: ogden
author_rank: Super Contributor
timestamp: May 03, 2020, 11:04:33 am
content: Quote from: Andreas on May 03, 2020, 09:42:49 amIncorrect. This is equivalent time sampling, not downconversion. Some scopes indeed have downconverters inside. One that I know: Teledyne-LeCroy LabMaster 10-100zi 100GHz Oscilloscope. Further info: The Signal Path youtube video #45.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 03, 2020, 02:59:56 pm
content: I never know anymore if my posts are censored or if I actually forgot to press enter.If I didn't explain it well enough, the flash converter would digitize the data and record it to a large buffer. Once I had the data, I would then play it back at a much slower rate so the scope could keep up. In my case, I was using analog scopes so I had to refresh the display by playing the recorded data over and over. The recorder provides a trigger output to the scope to keep it in sync. There was a delay adjustment for the trigger that allowed me to scroll through the data. It was very crude but at the time, high speed digital scopes were fairly expensive.The setup was very crude but it did allow me to view signals that were much faster than the scope could normally handle. I built a much slower, higher resolution system years later. This system had a power amplifier, a few preprogrammed waveforms and a PC interface. My first arb was born...

author: petert
author_rank: Regular Contributor
timestamp: May 03, 2020, 04:45:56 pm
content: Quote from: ogden on May 03, 2020, 08:16:45 amI am pretty sure we mean the same. When you adjust the scales on your scope and you assume your signal has a limited bandwidth, you'll get the same reading (=waveform) on the screen (within some errors bounds, obviously), even if your originalsignalis a higher frequency (but, again, limited in bandwidth).QuoteI was aware that radios had such signal processing stages built-in, but I hoped there would be some commercial options available, similar to upconverters for SDRs.Ideally, you could put them between the BNC inputs of a scope, and the signal source.

author: petert
author_rank: Regular Contributor
timestamp: May 03, 2020, 04:52:28 pm
content: Quote from: vk6zgo on May 03, 2020, 09:22:00 amThanks, that's exactly my goal. Are you aware of any commercial options that do that (ideally with a selectable band)?

author: ogden
author_rank: Super Contributor
timestamp: May 03, 2020, 11:23:03 pm
content: Quote from: petert on May 03, 2020, 04:45:56 pmSame example: 866MHz, 1KHz deviation and 1K symbols/sec is downconverted to 10MHz (IF) frequency. Tell me what good will be for you to look at 10MHz sine waveform coming out of downconverter? Sine will be sine no matter - you look at 10MHz+1000Hz or 10MHz-1000Hz waveform. Hint: RF engineers mostly use spectrum/signal analyzer rather than scope.

author: nctnico
author_rank: Super Contributor
timestamp: May 03, 2020, 11:32:07 pm
content: Quote from: ogden on May 03, 2020, 11:23:03 pmIt could be interesting to look at how the transmitter is starting up on, maybe look at some phase/frequency shifts in the signal. In theory you should be able to capture the waveform and demodulate it using software on a PC. All in all there are plenty of interesting time-domain properties of an RF signal.

author: ogden
author_rank: Super Contributor
timestamp: May 04, 2020, 12:19:44 am
content: Quote from: nctnico on May 03, 2020, 11:32:07 pmNah. Get RTL-SDR dongle and consider it done. For those who work with wider than 1MHz bandwidth signals scope with downconverter won't do any good anyway.QuoteSure. Please share your experience - tell how do you do RF work using scope.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 04, 2020, 09:28:59 am
content: Quote from: ogden on May 04, 2020, 12:19:44 amWhy do you say that?There are very few 1MHz bandwidth oscilloscopes around these days.There is no reason why a "chunk" of spectrum equal to the bandwidth of the associated 'scope cannot be downconverted.Such tricks were not uncommon in the days of quite low bandwidth oscilloscopes.Just such a device was described many years ago in an ARRL Handbook.The idea was so you could look at AM, SSB, & Morse code to check modulation percentage with the former, & the shape of the keyed signal with the latter.This still could be useful with, say, a UHF transmitter & a low-ish bandwidth 'scope.With the improvement in bandwidth of 'scopes, & the advent of, first, analog sampling oscilloscopes with bandwidths into the GHz region, followed by normal DSOs & GHz versions of them, the requirement (which was never mainstream) went away.QuoteCertainly, on one occasion, an oscilloscope found a problem in an FM Broadcast transmitter which appeared to be quite mystifying.The FET Driver PA drove the grid of a Tetrode output tube, with a meter showing the output of the former.The normal tuning method was to tune the tube grid circuit for a maximum on this meter, till in passing, we discovered that the Transmitter output increased when we detuned from that "grid peak", instead of falling.I looked at a monitor point associated with the meter & tuned as normal, displaying 3 or 4 cycles of the 100MHZ signal on a IWATSU 200MHz Oscilloscope.The problem was immediately obvious, from the shape of the waveform.When "peaked" the driver amplifier produced a large amount of 2nd harmonic distortion, which gave the waveform a "peakier" shape, with the narrower peaks higher in amplitude.The meter, being a "peak & hold" circuit, happily interpreted that as a higher output.The PA stage tuned circuits rejected the harmonics, so the output power dropped.A Spectrum Analyser would have shown the problem up, too, but the 'scope was there to hand, with a minimum of setup required, & the time domain result of a waveform change was probably easier to associate with the high meter reading than a bunch of extra carriers.This obviously wouldn't have been an application for the original idea we were discussion, but it is a real example of the use of an oscilloscope for RF work.

author: ogden
author_rank: Super Contributor
timestamp: May 04, 2020, 10:22:02 am
content: Quote from: vk6zgo on May 04, 2020, 09:28:59 am1MHz is RTL-SDR limitation, but scope won't help much because wideband signals usually are high speed transmissions that uses M-ary modulation, looking at such *waveform* using scope is pointless because in given bandwidth it looks like noise. Using scope as RF digitizer for spectrum/signal analysis PC software can be very good idea, yet I don't know any implementation. AFAIK there is no scopes in the GNU Radio hardware list (yet). Yes, there are Tek MSO5000 and alike which indeed is scope for RF work - with proper RF frontend and spectrum & vector signal analysis software (option).

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 04, 2020, 11:53:02 am
content: Quote from: ogden on May 04, 2020, 10:22:02 amWe do use scopes for a lot of RF work, for example for looking at (admittedly non-standard) communication signals, simply because a scope gives us a lot more analysis BW than any SA (high end real-time SAs go up to 1GHz, while with modern scopes we get >50Ghz of BW), and while the signal (to some extend) does resemble noise there are certain signal properties which are of interest.I actually see a lot more use of scopes in RF work in general, for tasks that in the past were performed with spectrum analyzers. SAs are still needed when RF performance is crucial but many modern high-end scopes perform really well in a wide range of RF related tasks.It's also very likely also the reason why the new Keysight MXR comes with optional RTSA functionality.QuoteThe Tektronix MSO5000 is the MSO model of the old DPO Series and it has nothing which would make it particularly well suited for RF work (in fact, it's an 8bit scope which is pretty slow, and even more so with SignalVu running on it). You might be thinking about the old MD3000 and MDO4000 Series which *did* have a separate RF input and built-in "spectrum analyzer" functionality but in reality this was just using scope FFT, with limits in analysis BW and resolution as well as a woeful RF performance, and in case of the MDO3000 with a complete lack of phase information and no way to run scope mode and "spectrum analyzer" in parallel.

author: ogden
author_rank: Super Contributor
timestamp: May 04, 2020, 12:28:55 pm
content: Mentioning hi-end 50GHz bandwidth scope in discussion where we talk wbout downconverter to reach 500MHz is blasphemyRegarding Tek "RF scopes" - most likely there are better MSO's than one I found using search. Please suggest then, preferably reaching said 500MHz, as low cost as possible. 50GHz frequencies are mm-wave, not even microwave or for god's sake RF. You most likely work on radar or UWB application where completely another set of tools, skills and methods are needed. Nothing even close to classic superheterodyne RF stuff (upconversion/downconversion) we were talking here.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 04, 2020, 01:43:38 pm
content: Quote from: ogden on May 04, 2020, 12:28:55 pmYou are absolutely right. I shall self-flagelate immediatelyQuoteThere aren't a lot of scopes in the 500MHz class which are particularly well suited for RF work (and those that are are also expensive). Most of the scopes are more basic, embedded-type scopes which have no decoding capability, so you mostly have to rely on external processing.Some scopes, like the MSO5000 (which isn't exactly cheap, though), are supported by signal analysis software of their manufacturers. For example the Keysight DSOX3000A/T, which is supported by the 89600B/C VSA software. However, while the scopes themselves already aren't exactly cheap, the software is pretty expensive, too.Of course there's always the 2nd hand market. For example, an Agilent DSO8064A or DSO8104A (although the 8064 can easily be converted into a 8104 by removing a resistor so you get the same 1GHz BW) or one of the older XP based 54800 Series scopes, together with a copy of the Agilent 89601A VSA software, would make a good option (provided you can 'find' the VSA software). Getting a DSO8k for cheap (i.e. below $2k) takes a bit of luck but the 54800s can sometimes be found below $1k. The VSA software can run on the scope so a separate PC isn't necessary.There also are the LeCroy LC, WaveRunner2 LT and WavePro 900 Series, which have 500MHz models and which offer good FFT and some demodulation/signal analysis capabilities which can be 'hacked' (unlocked). LC and WR2LT often go for notably below $1k. Keep in mind that these are primarily analysis scopes not high update rate scopes, though.There's of course always the option to couple any decent scope (even the ones from Rigol and Siglent) with external 3rd party software. There's SciLab/Xcos and Octave, both open source and free alternatives to Mathlab, which can be used to either use one of the available analysis toolboxes or write your own. These aren't the only tools, there's Mathlab (there's a hobbyist license but it's somewhat pricey), LabView Community Edition, and so on. It requires an external PC and monitor, though.At the end of the day it comes to what you want to achieve, what your budget is and if you can write some code yourself.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 04, 2020, 11:13:10 pm
content: Quote from: ogden on May 04, 2020, 12:28:55 pmFunny thing, nobody told the hams who use superheterodyne principles on 47 & 122 GHz!https://www.wia.org.au/newsevents/news/2019/20190318-1/index.php

author: 0culus
author_rank: Super Contributor
timestamp: May 05, 2020, 04:19:57 am
content: As a historical note, the old HP 8405A vector voltmeter can be used for exactly this purpose. On the rear panel is a pair of BNCs that give you a 20 KHz sampled output that preserves the important characteristics of the RF waveforms (particularly their phase relationship, relative to channel A which is the phase reference). The reasoning behind this is that ultra wideband oscilloscopes were rare and and exceptionally expensive even for many labs back in the 1960s (at that time, the Tek 519 might have been the only "commodity" option IIRC). You might instead have had access to a much lower bandwidth scope, but it could easily work at 20 KHz yet still be able to look at RF waveforms up to 1 GHz when used with the 8405A.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 05, 2020, 07:57:37 am
content: Quote from: ogden on May 04, 2020, 12:28:55 pmTwo things: for one, not everything we do is above 50Ghz, in fact we also regularly use Keysight and LeCroy scopes for RF stuff up to 8GHz, sometimes also in combination with down-converters. So there's that.The second thing is that your claim 50GHz being neither microwave or even RF is flat out wrong. While it's correct that 50GHz and above are part of the mm wave range, it's of course also still microwave (a range which is commonly defined as either the band between 300MHz and 300GHz or the band between 1GHz and 100GHz, with 50GHz well within both definitions). And since RF is defined as the frequency band up to 300GHz it means that the 50GHz - 110GHz band (the latter being the current limit for scopes) is, of course, still RF.As to heterodyne stuff not used in the mm band, you may want to have a look at what operating principle common spectrum analyzers which cover frequency ranges above 50GHz use. Or many receivers that covers such frequenciesLastly, working with RF stuff above 50GHz isn't really much different than working with lower RF ranges, the same laws of physics apply, just everything (tools, cables, connectors, components) gets exponentially more expensive

author: ogden
author_rank: Super Contributor
timestamp: May 05, 2020, 05:19:46 pm
content: Quote from: Wuerstchenhund on May 05, 2020, 07:57:37 amThat is not what I said, nor mean. You seemingly decided to ignore whole sentence where I mention radar and UWB. Whatever. That's offtopic anyway.Why don't you instead explain how one can connect Rigol scope to Octave, then do vector signal analysis of QAM modulated signal?QuoteThis is not what proud microwave or mm-wave engineer usually say. Whatever. As I said: offtopic.

author: petert
author_rank: Regular Contributor
timestamp: May 05, 2020, 07:07:02 pm
content: The discussion is quite interesting, thanks for the debate.Without wanting to be boring, what about the initial question about a commercial downconverter (for those that think it is useful for limited RF work :p)?

author: ogden
author_rank: Super Contributor
timestamp: May 05, 2020, 07:27:04 pm
content: Quote from: petert on May 05, 2020, 07:07:02 pmIf you can't find such product using internet search - most likely it does not exist. Perhaps you may consider making one and demonstrate all those cool things you can do with it?

author: vk6zgo
author_rank: Super Contributor
timestamp: May 05, 2020, 11:49:47 pm
content: Quote from: petert on May 05, 2020, 07:07:02 pmNo, as far as I can determine, they were never commercially available as "standalone" devices.There were quite a few described as construction projects in Electronics publications, but most similar use was that of using other equipment which happened to have a downconverted output available.Much everyday work at RF is to do with such questions as:-"Is it there?""Is it roughly the right amplitude?""Is it intermittent?""Is it the right frequency?"The first three can be determined by a low level pickup point & a calibrated detector, using a lower frequency 'scope.The down converted 'scope would be OK for one to three, & even the fourth, (using a bit of Mathematics), but for proper accuracy a frequency counter would do better in that case.Note: A Spectrum Analyser would still have poorer accuracy than a counter, but would do the first three OK.When you need to look for harmonic distortion of a higher frequency signal, as in my FM Broadcast anecdote, I'm a bit doubtful if the second harmonic information would survive the down conversion.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 06, 2020, 06:39:26 am
content: Quote from: ogden on May 05, 2020, 05:19:46 pmConnecting a scope to Octave isn't difficult. Ideally get a decent Linux (I'd recommend openSUSE Leap because it's the most easy to use variant), install Octave, then the Instrument Control package, and then configure your interface:https://wiki.octave.org/Instrument_control_packageOctave Packages can be found at the Octave Forge:https://octave.sourceforge.io/packages.phpYou'll also want to install application-specific packages, for signal analysis this would be signal, communications and general.And then you're set to start developing your code.The Mathlab web site has some examples which can be used as inspiration:https://www.mathworks.com/help/signal/examples.htmlQuote from: petert on May 05, 2020, 07:07:02 pmI'm not sure there is something read-to-use with a scope. Pretty much all the downconverters we use are either proprietary units not available on the open market or have been designed by ourselves.Still, as other said, you might be able to find some COTS converters which might work, but frankly if that's not for something in the high GHz range then you're much better off just getting a larger BW scope - even a 2nd hand one (which can be surprisingly inexpensive).

author: CaptDon
author_rank: Super Contributor
timestamp: May 10, 2020, 07:38:18 pm
content: In a manner of speaking an old UHF television tuner is a downconverter.They will use a local oscillator and mixer section to cover roughly 400mhzthrough around 800mhz down to something in the 45mhz television receiverI.F. range. Many ham radio folks tweaked these older modular tuners foramateur television on the 432mhz band. Some older HP frequency countersand spectrum analyzers used plug-in modular downconverters to run countersthat had a max rate of about 50mhz. The downconverted output did representthe input, but shifted to a lower frequency. Some of these converters had a weirdinverted shift if you didn't use them correctly, LSB became USB, as the frequencywent down on the input it went up on the output. You had to be aware!

author: hendorog
author_rank: Super Contributor
timestamp: May 10, 2020, 08:02:04 pm
content: There was a low cost down converter unit floating around, I have one somewhere. Little unit with alu case and screen.Cant remember what it's called or if it's still available, but I will dig it out and post.

author: mio83
author_rank: Regular Contributor
timestamp: May 10, 2020, 08:18:41 pm
content: Hi!Interesting thread!With the similar idea of extending the usability of my SA (not oscilloscope), I have been looking at the Morfeus mixer (so both downconverter and upconverter capabilities) unit:https://www.crowdsupply.com/outernet/morfeusYou can find a lot of discussion about it in the Outernet forum here:https://forums.othernet.is/t/rf-product-morfeus-frequency-converter-and-signal-generator/5025/215I have asked, and they will produce a new batch of these units in August 2020. I am very tempted to buy one.If somebody has experience with these units, or has any opinion on them anyway, please comment! I am curious!EDIT: of course if you already have a good signal generator for the LO signal, it might be just better to buy a good mixer such as those available here:https://www.minicircuits.com/WebStore/Mixers.html

author: joeqsmith
author_rank: Super Contributor
timestamp: May 10, 2020, 08:31:17 pm
content: I must have missed something. Obviously you can down convert using mixers but I thought the OP was trying to capture a single shot event of something higher than what their scope could sample and not loose information. A bit more difficult.

author: hendorog
author_rank: Super Contributor
timestamp: May 10, 2020, 08:39:41 pm
content: Quote from: mio83 on May 10, 2020, 08:18:41 pmThats the one I was trying to remember, thanks !If I can find it I will hook it up to the scope and take some screenshots.

author: mio83
author_rank: Regular Contributor
timestamp: May 10, 2020, 09:45:42 pm
content: Quote from: hendorog on May 10, 2020, 08:39:41 pmThanks! That would be great!I am curious of its behaviour both as a mixer (of course) but also as a signal generator. Can it produces signals of, e.g., 7dbm (for example to drive other types of mixers)? What is the signal purity/harmonic rejection vs frequency ? Etc...Also, I am not sure if you can give a look inside, so to see what kind of mixer they are actually using.thanks!

author: hendorog
author_rank: Super Contributor
timestamp: May 11, 2020, 05:10:19 am
content: Quote from: mio83 on May 10, 2020, 09:45:42 pmJust found it and plugged it in, here is some rough info for now.Output level is between 0 and 7dBm up to around 1.2 GHz. It is only at 7dBm for a small part of that so driving a level 7 mixer would be limited.There are of course active mixers you could use - ADL5801 from memory.Harmonics are not filtered, so about 10 dB down or a bit more.It worked as expected as a downconverter into a scope and a SA.I opened it up, it only has a single RF chip which is under a can.The RF chip is the RFFC 5072, synth + mixers all in one.Output is driven through a balun.https://www.qorvo.com/products/d/da000735Not high performance, but it is very convenient - It is USB powered so I powered it from the scope.Build wise, the PCB is only supported by the SMA adapters. There are no stand-offs holding the back of the PCB away the alu. back plate. A bit poor, but it probably doesn't matter unless it was dropped or exposed to vibration.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 11, 2020, 06:52:32 am
content: If you have a signal that is bandpass, you can actually use a downconverter and still use time-domain. The only thing you should do is to upconvert back to the original frequency in digital.This is actually used in some of the Lecroy high-speed oscilloscopes: In essence, their 100 GHz scope is 3 36 GHz (I think) scopes tied together, with a different downconverter in front of each. In the digital domain they are then converted back to the correct frequency and assembled back together.I know that some here have voiced their opinion that for some reason 50 GHz does not classify as RF, but there is no reason you can't use this technique in the home lab - all you need is something like MATLAB, or free alternatives like Octave or python.To get good performance out of it you would likely need some calibration techniques (calibrate out the phase response and amplitude response of the mixer, and perhaps figure out how to eliminate images) but that could be a cool project.Main limitation I would forsee is that by virtue of the limited capture time, you will see some edge effects in your signal when transforming back up.

author: ogden
author_rank: Super Contributor
timestamp: May 11, 2020, 03:52:17 pm
content: Quote from: TheUnnamedNewbie on May 11, 2020, 06:52:32 amLOL. Whatta sticky topic. Yes I had to say it other way around. I did mean simplified RF banding: 0-1GHz - "generic RFband", 1-30 GHz - microwaveband, 30-300 mm-waveband. Some may disagree, I don't mind. Whatever. For example even IEEE and ITU do not agree on what's actuallyUHF band.QuoteYou say that all you need for 50GHz work in home lab is MATLAB or Octave? LOL.

author: mio83
author_rank: Regular Contributor
timestamp: May 11, 2020, 09:04:01 pm
content: Thank you very much ogden for your tests.Interesting that the MoRFeus uses a RFFC 5072 mixer.The same chip is also used by the HackRF ONE (which is a similarly priced open source SDR) in combination with other RF chips (seehttps://github.com/mossmann/hackrf/wiki/Hardware-Components).I tried my HackRF and also couldn't get the desired 7dbm:However the harmonics rejection seems slightly better than that on your moRFeus?@30Mhz, max power = 14dbm.@30Mhz at 7dbm, harmonics rejection: -25db@100Mhz, max power = 9dbm.@100Mhz at 7dbm, harmonics rejection: -27db@200Mhz, max power = 4.5dbm@200Mhz at 4.5 dbm, harmonics rejection: -26db@500Mhz, max power = 1.5dbm@500Mhz at 1.5 dbm, harmonics rejection: -21db@1Ghz, max power = 0dbmharmonics rejection(can't verify with my HP 8591E spectrum analyser)@1.5Ghz, max power = -4dbmharmonics rejection(can't verify with my HP 8591E spectrum analyser)@1.8Ghz, max power = -3.5dbmharmonics rejection(can't verify with my HP 8591E spectrum analyser)(see video if interested:https://youtu.be/At13AUqLf-4)Now I wonder if I can "hack" my HackRF, get to its IF stage which is handled by the RFFC 5072 chip, and use it as a MoRFeus mixer.Wishful thinking question 1:Does anybody here have a HackRF and could check the max-power levels and harmonics at frequencies >1.8Ghz? I am curious because the "datasheet" of the HackRF claims >10dbm from 2100 to 2700 Ghz.Wishful thinking question 2:Does anybody here have a HackRF and has tried to get direct access to its IF stage?