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Originally posted by chudster
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Folks are welcomed to open up discussions on this topic under a new thread. -
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Originally posted by chudster View PostI think you are 100% on target. If you look at past posts I put a stake in the ground that 1MSPS was likely to be a practical limit to the start of sampling. It makes sense when experimenting, as you are, to go higher than that.
It will not stop the patent being granted if the examiner is not aware of it- and you are right that they mainly seek prior art from patents. Companies though are happy to sit on their patent as a threat but drop like a hot potato or don't start action if there is a valid threat to that patent's validity from prior public disclosure. There is an old adage that a patent's value is never known until a court tests it. I suggested in a past post that if BW wanted ML to go away, finding prior art would be a great strategy. There is also an obligation on the patent holder to disclose any prior art it knows about and if a company employee read a forum post they are on shaky ground if they don't disclose that to a patent examiner if it was relevant.
But yet linux lives....
I don't doubt it. You would need to get the legals right and perhaps avoid some of the alleged grandstanding of the QED folks. An issue with any hardware though is getting funding to make it as business people want a return and could get scared by past patent action. BTW, have you seen www.kickstarter.com ?
yep I have seen the kickstarter.com site ...very interesting concept ...who is up for it ?Comment
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Carl,
Thanks for your recent multiple posts and input on sampling rate which makes sense.
I had a look at the topics and nothing leapt out as being appropriate. Where should such a discussion topic best be posted?
ChudsterComment
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Well me for one. I think its an idea well worth exploring.Originally posted by moodz View PostComment
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If you put underengineering aside, a whole point IS squeezing as much juice from as little lemon. The way I see it, moodz made a platform that will enable him to squeeze all the juice there is, and hopefully he'll find a more economic way of doing it in a process. Now, why would that matter? Say GPS! You may have mm precision location using nowadays GNSS technology using signals at 1575.42 MHz (L1) and at 1227.60 MHz (L2) with bandwidth of only (!) 10.23 MHz. So instead of going THz we have a perfectly good navigation system with much less that can fit into a wrist watch, and be purchased by ... just about anyone.Originally posted by chudster View Post
Carl mentioned target variation in 10Hz range, and moodz mentioned digital CRO as revealing tool for PI secrets. Well, cheap digital CRO's mostly do not employ as sexy ADC as 24bit@2MSPS, instead they use SAH and relay on periodicity of the signal at hand - which we have. 10Hz is very slow by any account.
So, how GPS using only 10.23 MHz bandwidth achieves spatial precision is a key as why <24kHz can be just enough. Exactly as VLF utilises phase granularity, every other system can use it as a compression tool for fine time granularity. If it takes a super sexy ADC and FPGA to reach there - fine.Comment
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Hi all,
may I add my comments?
Hey, don't forget, that the target response is also a wideband frequency response. The infamous target time constant TC is just saying, that in 1 TC time, the target signal response is decaying into the 1/e level (100% - 63.2% = 36.8%) related to the initial/reference response.
Even a short time constant targets produce a low frequency response but at low signal energy levels. Short TC targets have significant more response energy at high frequency region (just after the flyback period for a short duration of time: 0 < t < 1-2 TC).
The fact, that VLF detectors can also detect small targets is, that they accumulate the low signal response at much higher pulse frequency rates. Compare a PI at 1kHz and a VLF at 30 kHz. The VLF detector is accumulating the small signal response 30 times more.
That's the reason, why a low bandwidth will also work. But it might not be sensitive enough to small targets due to low spectral energy acquired (leaving the high frequency response). For chasing the fly****e targets, 1 MHz bandwidth is by far enough (not to say, it's an overkill).
Cheers,
AzizComment
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Bandwidth limitting makes sense.
Consider, you have a TX transmitting a wide band pulse, let's say 10 Mhz bandwidth (ultra fast coil).
And you can detect only a bandwidth let's say 1 Mhz bandwidth.
Does it makes sense to transmit the other 9 Mhz bandwidth too?
No, not at all. You could move the "wasted" transmitted energy into the frequency region you take the measurements. And you have more bang to the targets.
Fortunately, the coil with it's parasitic capacitances and damping resistor forms a low-pass filter, which is limitting the reasonable frequency response into the 500kHz to approx. 1 MHz region. If you are not using (sampling) this frequency region, you are just wasting TX energy.
Now consider the TEM transmitter and a sound card processing at 48 kHz bandwidth. It works even, when the transmit energy is limitted to the 48 kHz bandwidth. And I have more bang to the targets instead of wasting a lot of TX energy.
AzizComment
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Once again:
If you want to investigate the EM physics, the sound card based system is sufficient enough to make it. It doesn't matter, if you have low bandwidth. The physical effects occur in the low frequency region as well. And the principle remains the same and you can apply it for a wide band version.
You can use a semi analog-digital system with the sound card as well. The analog section in the front-end is sampling the high frequency response using S/H or integrator (most welcome) and converts it (the spectral energy) into a low frequency modulated signal (using a modulator), which can be decoded by the sound card by the software using the Tablet PC as a processing back-end platform.
You can imagine, that such a system can easily knock out an over-priced top detector. And the ground balance can be implemented in a very sophisticated algorithm/method.
You guys don't take me serious. I'm almost tired to tell you the same stuff over and over again.
AzizComment
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Aziz, can we transpond those strong signal by some sort of modulation (e.g. phase modulation) from high coil resonance band to low sound card band?Originally posted by Aziz View PostComment
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You can move a bandwidth (frequency region) to any frequency region you want to have using a modulator. But if your measured bandwidth is limitted, you can't detect the higher bandwidth responses. TV, SAT and radio systems using this principle by translating the high frequency region into a low frequency region (or vice versa depending on the signal direction). This doesn't make sense in the MD technology. Forget this modulation type.Originally posted by WM6 View Post
The other concept is using an integrator, which is integrating a "spectral response" depending on the time position and time duration and the frequency response of the integrator (note, it's a low-pass filter). You get a phase dependent DC voltage, which can be modulated into any frequency. The semi analog-digital system just maps some integrated DC voltages (samples) into the 48 kHz region (or even into the 20 kHz region if you want), which can easily be decoded by a slow ADC system.
AzizComment
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Thanks. Do you suppose that time position and time duration of signals contain useful information for target identification or this is something too variable to rely on this for target identification?Originally posted by Aziz View PostComment
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The truth is: reliable discrimination can't be implemented.Originally posted by WM6 View Post
But the ground balance can be implemented (by separating X and R) and the relation of X/R (or vice versa) gives a good indication to discriminate iron/non-iron targets. It might work for most conditions. But can fool you too.
Aziz
PS: We have a very nice weather here. I'm heading for a walk.... Cheers.Comment
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We are discussing PI aren't we??? Where does the X come from for Ground Balance???Originally posted by Aziz View PostComment
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Back again.
While I ignore Ufox (he can't even write my name), we have to talk about the TX frequency response further. Where is the significant upper frequency limit?
Consider the following practical example:
We have a damping period of 6µs - 10 µs until we can get some samples. While looking at the coil current slope (dI(t)/dt), we can expect of having not much significant high frequency components after the flyback period. The later sampling times eating a lot of high frequency response and we effectively end up of having maybe a bandwidth of 200-400 kHz.
So 1 Mega samples/s is just an overkill and should be enough for experiments.
AzizComment
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