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| Frequency Divider for older Oscilloscopes?? |
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| tggzzz:
It strikes me that people in this conversation would benefit from thinking about how "Tayloe Mixers" work. Also see "Polyphase mixers" and "N-path filters". https://www.eevblog.com/forum/rf-microwave/polyphase-or-n-path-mixer/msg3381802/#msg3381802 isn't a bad starting point, but there are probably better ones. |
| bdunham7:
--- Quote from: Jorge Ginsberg on July 18, 2021, 05:44:49 pm ---If you take a single sample per period and repeat the same thing for 10,000 periods, when you reconstitute the signal, it will be an exact copy of the original signal, but its frequency will be 10,000 times lower. By doing that it is possible to observe a 100 Mhz signal as if it were a 10 Khz signal, something that any cheap oscilloscope can do. --- End quote --- You might want to draw a picture or something because something is missing here. If you take 10,000 samples at exactly the same rate as the input signal, which is what you seem to be implyiing, you'll have 10,000 of exactly the same sample--a flat line. Second, you are clearly not storing the samples anywhere, so how are you 'reconstituting the signal'? I believe the systems 2N3055 refer to require storing the samples. Third, are you implying that the fact that you take exactly 10,000 samples will result in an apparent frequency reduction of 10,000 times? I don't see how that would work and I don't see how your system could manage that in any case--it is too simple with just those components. The only way I can see something with that few components working is as some sort of mixer. You wouldn't have a schematic or anything by chance? |
| 2N3055:
--- Quote from: bdunham7 on July 18, 2021, 07:04:12 pm --- --- Quote from: Jorge Ginsberg on July 18, 2021, 05:44:49 pm ---If you take a single sample per period and repeat the same thing for 10,000 periods, when you reconstitute the signal, it will be an exact copy of the original signal, but its frequency will be 10,000 times lower. By doing that it is possible to observe a 100 Mhz signal as if it were a 10 Khz signal, something that any cheap oscilloscope can do. --- End quote --- You might want to draw a picture or something because something is missing here. If you take 10,000 samples at exactly the same rate as the input signal, which is what you seem to be implyiing, you'll have 10,000 of exactly the same sample--a flat line. Second, you are clearly not storing the samples anywhere, so how are you 'reconstituting the signal'? I believe the systems 2N3055 refer to require storing the samples. Third, are you implying that the fact that you take exactly 10,000 samples will result in an apparent frequency reduction of 10,000 times? I don't see how that would work and I don't see how your system could manage that in any case--it is too simple with just those components. The only way I can see something with that few components working is as some sort of mixer. You wouldn't have a schematic or anything by chance? --- End quote --- It is called RIS (random interleaved sampling) and ETS (equivalent time sampling). You need to have a trigger circuit with very low jitter. You have a sample and hold circuit (S/H) that takes super short sample (let say samples single value for 100 psec) and keeps it for readout. So you trigger, and take a 100 psec sample. You then readout that value and read it with slow A/D converter. In meantime, millions of periods of signal passed by. But since signal is repetitive we don't care. After saving that first point, we rearm trigger, and wait for new one. When it fires, then magic hapens: we sample signal with a 100 psec delay from trigger. Sample and save that. Third time, we take sample at 200 psec delay. That way we reconstruct a waveform from many many different trigger events. Equivalent sampling rate would be 10 GS/sec. With RIS (random interleaved sampling) we also trigger, but it is upside down: we sample at random intervals, not sequentially from the trigger. But we do keep triggering, and measure time from trigger and sample so we know where to position the point in time domain. It is funny to look at how it assembles the waveform by plotting random dots left and right until it starts to resemble the waveform... That is how analog sampler scopes worked, with different details in implementation of S/H circuit, and actual timing and trigger circuits. Some samplers didn't even have real trigger circuit, but you had to provide trigger yourself, already conditioned... |
| bdunham7:
--- Quote from: 2N3055 on July 18, 2021, 07:44:18 pm ---With RIS (random interleaved sampling) we also trigger, but it is upside down: we sample at random intervals, not sequentially from the trigger. But we do keep triggering, and measure time from trigger and sample so we know where to position the point in time domain. It is funny to look at how it assembles the waveform by plotting random dots left and right until it starts to resemble the waveform... That is how analog sampler scopes worked, with different details in implementation of S/H circuit, and actual timing and trigger circuits. Some samplers didn't even have real trigger circuit, but you had to provide trigger yourself, already conditioned... --- End quote --- I understand ETS and sampling scopes, I even have several still. I don't see how what Jorge is describing could possibly do any of those things. |
| Jorge Ginsberg:
A picture is worth a thousand words, the Chinese used to say. I would like to have a simple program with which I can draw sinewaves and other symbols to be able to explain in a single drawing what I find so difficult to explain with words... Does anyone know of a light program that would allow me to do that? |
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