Perhaps use the master drive pulse, inverted, to reasonable cancel the detected version as step one. Step two - try driven pass and shunt switching (TR/ATR style like in radar). Step three should then have lower level undesirable signals for switch diodes, etc.
But it does have an output winding (input "winding" being the beam) at present. Add one or two more for pulse cancelling.
The digitizer would be one of these super-fast sampling Guzik boxes, so expect 6 effective bits or so.
While it's certainly possible to do timed switching, I'd rather not go that way, because it complicates things considerably.
Your last suggestion, and Joerg's T/R switch are a good suggestion, I think. What about the following:
First attenuate the signal down to a more manageable 50Vp or so. Then use a diode *bridge* biased to some mA using a pair of
50 Ohm resistors to appropriate voltages at the top and bottom. Apply signal to one side, recover clipped signal at the other side. Then amplify again to bring out the spilled pulses. As a bonus, this should be pretty much non-reflective, which simplifies the interpretation of the output considerably.Let's see if I can make that work...
Jeroen Belleman
You can buy log strips from Analog Devices with about the right sort of bandwidth.
I think some other people make them too. (LT?)
Chris
The target is to deliver a signal from which the amount of spilled beam in each supposedly empty bucket can be measured. So, while signal compression would be useful, I don't think a detecting log amp is the right sort of device here.
Jeroen Belleman
Should work. A bridge is even better for T/R switching than a diode pair. I guess the extra 50 cents or so won't hurt on your project but on mine with 128 channels and non-government budgets it does.
However, make sure that your amplifier shows next to nothing in recovery time because it will still rail hard. Just like they do with ultrasound machines.
-- Regards, Joerg http://www.analogconsultants.com/
Ferrite circulators are used in RADAR front-ends, similar problem. The difficulty here is both signals have the same source, I think?
Actually, this does work. We used do it in ultrasound on the detection board in analog systems (now almost extinct). There, we have to be able to detect 20-30dB of blood flow information that is, in the time domain, right next to huge unwanted wall echoes that are 40dB above the maximum flow signal (in heavy smokers, for example).
-- Regards, Joerg http://www.analogconsultants.com/
If you're going to use a bunch of brain dead metaphors like "spill" and "bucket" in reference to electronic design then you get what you deserve: dumb ideas.
Bloggs! Why are you so cranky all the time? ...Jim Thompson
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I love to cook with wine. Sometimes I even put it in the food.
It's fast, but AFAICT there ain't no ferrites that would even work at 3GHz.
[...]-- Regards, Joerg http://www.analogconsultants.com/
Hi Joerg, I found this online,
I have used ferrite isolators past X-Band.
Those are the usual bifilar (sometimes multifilar) winding transformers. The core only provides coupling at lower frequencies (
Ok, there is some material available but that has DoD pricing level.
-- Regards, Joerg http://www.analogconsultants.com/
I think it's very descriptive and clear--similar to how people describe the operation of CCDs. What don't you like about it?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
I just designed an X-ray controller and one section is called "spit detector". No kidding. Has nothing to do with chewing tobacco or spittoons. That is the colloquial expression for tube arcing among those in the know in the field of X-ray.
-- Regards, Joerg http://www.analogconsultants.com/
Saturation doesn't work that way -- takes flux (volt seconds), not voltage. At best, you could clamp the later part of the spike, once the ferrite's charged up (so it tightens to a narrower pulse, but the peak value remains). You still need freewheeling to discharge it, which means as soon as that pulse is gone, you're going to have at least as big of a tail (at minimum, the waveform will look like dV/dt with a peak voltage similar to the original; at best, high frequencies will be attenuated in the ferrite and it will relax slowly).
A rectangular pulse, 600V * 4ns, is only 2.4 uVs, so you'd need quite a small core (about 8 mm^2 cross sectional area, about what's on a large ferrite bead-on-lead). I don't think any ferrites go fast enough, anyway; even the highest are all but RFI shielding by those frequencies. It would work (in the sense of doing what it will do, not necessarily what's intended :) ) on pulses of, say, 10V and 100s of ns.
I have another question for the OP: If these signals are so immensely weak... how is it even possible for the end purpose to care? How does it know? Surely there will always be some leakage between buckets, and the goal is simply minimizing the amount, and mitigating the error resulting therefrom?
Since this is physics we're talking, wouldn't it be possible to add two "kickers" to the line, timed to the big pulse, which neatly remove the leading and following buckets? If that requires modifying or lengthening the line (or, if the buckets are already zooming along near the speed of light.. it may require a bend!), well... whoever designed this should've thought of it in the first place..?
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
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