I would rather worry about overshoot:
I would rather worry about overshoot:
This is for 0 cm, 1 cm, 5 cm and 10 cm stubs, using vacuum (air) as dielectric. So this should correspond to about 0 cm, 0.5 cm, 2.5 cm and 5 cm stubs for real world dielectrics.
Well this is pretty much theory. This is the case if the coax cable impedanz is perfectly 50ohm which is not the case and if the Transmission line inside is perfectly and if the Terminator is perfectly 50ohm ... I would worry more about tolerances than this line theory
This is the fastest rise time I could generate within a few minutes for a simple test (that's the trigger output of my DG1022). So maybe someone with access to a faster rising edge could create a better test case.
Very interesting. What program did you use for this?
This is Qucs (http://qucs.sourceforge.net).
One thing you have to add to your simulation.
The scoop entry is also a low pass filter, in this case a 300 Mhz low pass filter,
thats why signals going to the 300 Mhz always look always like a sine wave, because of the low pass filter.
All the harmonics are gone after 150 Mhz, all is left is a sine wave..
So a scoop of 300 Mhz is usefool to 20 Mhz.
One thing you have to add to your simulation.
The scoop entry is also a low pass filter, in this case a 300 Mhz low pass filter,
This is tricky because the 16pF / 1 MOhm scope input is already part of the 300 MHz spec. But I've created bode plots of the original circuit and with an added first order 300 MHz low pass:
http://imgur.com/a/sMYNH
This set of images also contains a transient simulation of the circuit with the added additional filter. As you can see, the rise time is slightly lower now but it does not really make any difference regarding the qualitative effect of the short transmission line between the termination resistor and the scope input.thats why signals going to the 300 Mhz always look always like a sine wave, because of the low pass filter.
All the harmonics are gone after 150 Mhz, all is left is a sine wave..
So a scoop of 300 Mhz is usefool to 20 Mhz.
I think you are confusing bandwidth and sampling frequency here. All DS2000 scopes have a sampling frequency of 2 GHz.
Also: The harmonics above the nyquist frequency (1 GHz in this case) are not gone or magically filtered by the sampling. They show up as aliasing frequencies. You have to actively filter those components out using an anti-aliasing filter. If you sample fast enough you already have significant low pass characteristics on your input path and don't need to build a filter, its just implicitly there. That's the 300 MHz in this case.
But those filters never do have an ideal sinc impulse response. So you will never see a signal just morphing into a pure sine wave when approaching the filter edge frequency. (You can build such filters in a DSP of course: Just perform an FFT, mask out the frequencies you do not want, and run an IFFT. But you will never see the equivalent of that in an analog filter.)
There is this rule of thumb that you should have at least a factor 10 between sampling frequency and bandwidth. It is a good rule of thumb, but it is not the ultimate answer. The minimum factor between sampling frequency an signal bandwidth depends on the kind of signal you are interested in, the kind of aliasing filter you are using and the interpolation method you are using. In most RF applications you can get pretty close to the nyquist frequency, because you have extremely band-limited signals, use high order filters and you effectively use a sin(x)/x interpolation (you will never actually look at the signal in the time domain, but the algorithms work with an equivalent representation).
Highly summarized:
- For real time sampling acquisition and bandlimited signal: Fs > 2Fmax.
Now use common sense: Everything depends on the details that you want (I'm not talking about ADC dynamic range), more details -> more frequency components -> more BW, then -> more Fs.
i.e.: The sampling rate must also be sufficient for an acceptable reconstruction of the signal, for example a square pulse.
- For equivalent time sampling acquisition and only periodic bandlimited signal, then Fs can be less than signal's BW. But I think that this is not the case.
An interesting document (211 to 236) [220]:
http://w140.com/Handbook_of_Oscilloscope_Technology.pdf
For sin(x)/x interpolation, a sampling rate of 2.5x the highest frequency is considered good enough to faithfully reconstruct the signal from the samples. But sin(x)/x is highly susceptible to errors if the original signal contains frequencies higher than the Nyquist frequency.
That is why the Rigol DS2000 series automatically switches from sin(x)/x interpolation to linear interpolation when the sampling rate <= 500MSa/s - because the Nyquist frequency starts to drop too low for reliable reconstruction. For example, @ 200MSa/s the Nyquist frequency is 100MHz - which easily passes through the BW filter.
When you use linear interpolation, it's cruder so it requires a higher sample rate ratio for faithful reconstruction (at least 8x, but 10x is considered the rule of thumb as AndrejaKo mentioned), but it won't introduce false peaks at slower sample rates like sin(x)/x might.
I'm not sure which (or when, if switching between them) interpolation scheme the Owon uses.
Only as complement: pages 260-262 of the previous link.
Thanks marmad.
Hello,
Just to make sure: Is the JTAG-port on DS2202A at 3.3 Volt?
I will try it later tonight as well, just need to hack something together that generates a fast rising edges first, to test the 100 MHz with
I can try it too. Is latest DS1000Z firmware 00.02.01.SP1 requested for unlocking 100MHz?
Do we have some info or change list for this firmware? Thanks
I will try it later tonight as well, just need to hack something together that generates a fast rising edges first, to test the 100 MHz with
I can try it too. Is latest DS1000Z firmware 00.02.01.SP1 requested for unlocking 100MHz?
Do we have some info or change list for this firmware? Thanks
I just got a DS1074Z. Do the keys still work if I upgrade to 00.02.01.SP1? Also is there anyway to revert the options if I need to send in for repair?
Thanks
I'm having a few issues with my JTAG probe
Thanks for your efforts on this. Did you manage to do a JTAG verify of dump file against the device?. I'm not very familiar with DS code, but there is a lot of 0xFF empty space in the dump which would make me suspicious if I had dumped it.
I will try it later tonight as well, just need to hack something together that generates a fast rising edges first, to test the 100 MHz with
I can try it too. Is latest DS1000Z firmware 00.02.01.SP1 requested for unlocking 100MHz?
Do we have some info or change list for this firmware? Thanks
I just got a DS1074Z. Do the keys still work if I upgrade to 00.02.01.SP1? Also is there anyway to revert the options if I need to send in for repair?
Thanks
Ifaik the DS1000Z isn't hackable yet.
@ clifford: I agree, and I add some additional information that is related, read also attached fille:
[...]
PPS: I really like the introduction to sin(x)/x interpolation given in the following article.
I will try it later tonight as well, just need to hack something together that generates a fast rising edges first, to test the 100 MHz withI can try it too. Is latest DS1000Z firmware 00.02.01.SP1 requested for unlocking 100MHz?
Do we have some info or change list for this firmware? Thanks
I just got a DS1074Z. Do the keys still work if I upgrade to 00.02.01.SP1? Also is there anyway to revert the options if I need to send in for repair?
ThanksIfaik the DS1000Z isn't hackable yet.
DS1000z device options:
DSAB - Advanced Triggers
DSAC - Decoders
DSAE - 24M Memory
DSAJ - Recorder
DSBA - 500uV Vertical
DSEA - 100MHz
DSFR - all options
Also is there anyway to revert the options if I need to send in for repair?
Wow! The Agilent AppNote is a good read. Thanks!
(Nothing really new but everything in one place.)
...
I will try it later tonight as well, just need to hack something together that generates a fast rising edges first, to test the 100 MHz withI can try it too. Is latest DS1000Z firmware 00.02.01.SP1 requested for unlocking 100MHz?
Do we have some info or change list for this firmware? Thanks
I just got a DS1074Z. Do the keys still work if I upgrade to 00.02.01.SP1? Also is there anyway to revert the options if I need to send in for repair?
ThanksIfaik the DS1000Z isn't hackable yet.Yes DS1000Z is hackable: http://riglol.3owl.comQuoteDS1000z device options:
DSAB - Advanced Triggers
DSAC - Decoders
DSAE - 24M Memory
DSAJ - Recorder
DSBA - 500uV Vertical
DSEA - 100MHz
DSFR - all options
The hacks are even mirrored at your own website Avotronics http://rigol.avotronics.co.uk/mirrors/riglol/Also is there anyway to revert the options if I need to send in for repair?Use the SCPI command ":SYSTem:OPTion:UNINSTall" to remove installed option keys again. Search this topic for :SYSTem:OPTion:UNINSTall
Bugger! Lol.
That'll teach me. I was certain there were no hacks.
Wonder if I was thinking of another model....
Wait. Wasn't it that, originally, the DS1074Z hacks didn't add 100MHz option? Is that a new addition?
Anyone who wants to change their new DS1074Z into a DS1104Z use the following Codes:-
DSHA makes a DS1104Z with no options enabled .
DSHR makes a DS1104Z with all options enabled .
The 3dB bandwidth for the DS1104Z is approx 160Mhz.
The 3dB bandwidth for the DS1074Z is approx 90Mhz.
Minor correction to my previous post after some further investigation.
DSHA also enables the 500uV setting and another unknown, (at present), option.
DSEA is the correct code to change to a DS1104Z only. ( no options ). See table below.
Code DS1104z Unknown 500uV setting
DSBA X
DSCA X
DSDA X X
DSEA X
DSFA X X
DSGA X X
DSHA X X X
So to change a DS1074Z into a DS1104Z with all options enabled except the 500uV/div (which does not work correctly at present),
the code will be DSER.
It is possible to revert back to original, by using the SCPI command " :SYSTem:OPTion:UNINSTall " .
As mentioned in my previous post, the measured 3dB down bandwidth after changing to a DS1104Z, is approx 160Mhz.
All the tests were done on a DS1074Z with Ver:00.02.00.SP1.