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"Discriminating Time Domain Conducting Metal Detector Utilizing Multi-Period Rectangular Transmitted Pulses"
The independent claims in this patent are 1, 7, 13, and 18.
---- IT IS NOT PULSE INDUCTION ----
All the independent claims specify that the voltage transitions are between "substantially non-zero" voltages.
All systems which anyone refers to as PI that I know of, including the CCPI system I disclosed here on 29 Dec 01, involve transitions which are primarily to or from a zero voltage.
----TRANSMIT PULSE WIDTH--------
Remember that we're using the word "pulse" here in a non-customary manner. Here, a "pulse" refers to a period during which a voltage, which may be either positive or negative, but not zero, is applied. In other words, a multifrequency machine, not pulse induction.
All the independent claims state that the long pulse is at least 4 times the duration of the short pulse.
THEREFORE, combinations of transmit pulse durations which differ in duration by less than 4:1 do not infringe.
COMMENT #1: All else being equal, bigger differences would be better. However, all else ain't equal, and for many purposes, a difference of less than 4:1 would be quite satisfactory. The well-known Fisher CZ transmits a symmetrical square wave.
COMMENT #2: Why were the claims restricted to the condition that the ratio be at least 4:1? When you see a thing like this in a patent, it usually means prior art. A look at the patent file wrapper would almost certainly reveal this prior art, and a look at that prior art would probably reveal obviousness. Unfortunately, it usually costs several hundred bucks to obtain a file wrapper.
-----DEMODULATORS---------
Each independent claim describes demodulators which operate in the time domain (in that sense like a PI machine), not in the frequency domain.
Therefore any machine which demodulates in the frequency domain does not infringe.
In a multifrequency machine, I am not aware of any substantial advantage of demodulating in the time domain, other than that the "front end" can be gated to exclude reactive signals from the resistive amplification channels, allowing higher gain.
---SUMMARY-----
This patent does not concern anyone who is doing pulse induction, or anyone doing a multifrequency machine which demodulates in the frequency domain, or anyone doing an MF machine which demodulates in the time domain and which has a transmitter timing ratio less than 4:1.
The patented invention does not appear to have a substantial advantage over the alternative ways of doing things.
--Dave J.
The independent claims in this patent are 1, 7, 13, and 18.
---- IT IS NOT PULSE INDUCTION ----
All the independent claims specify that the voltage transitions are between "substantially non-zero" voltages.
All systems which anyone refers to as PI that I know of, including the CCPI system I disclosed here on 29 Dec 01, involve transitions which are primarily to or from a zero voltage.
----TRANSMIT PULSE WIDTH--------
Remember that we're using the word "pulse" here in a non-customary manner. Here, a "pulse" refers to a period during which a voltage, which may be either positive or negative, but not zero, is applied. In other words, a multifrequency machine, not pulse induction.
All the independent claims state that the long pulse is at least 4 times the duration of the short pulse.
THEREFORE, combinations of transmit pulse durations which differ in duration by less than 4:1 do not infringe.
COMMENT #1: All else being equal, bigger differences would be better. However, all else ain't equal, and for many purposes, a difference of less than 4:1 would be quite satisfactory. The well-known Fisher CZ transmits a symmetrical square wave.
COMMENT #2: Why were the claims restricted to the condition that the ratio be at least 4:1? When you see a thing like this in a patent, it usually means prior art. A look at the patent file wrapper would almost certainly reveal this prior art, and a look at that prior art would probably reveal obviousness. Unfortunately, it usually costs several hundred bucks to obtain a file wrapper.
-----DEMODULATORS---------
Each independent claim describes demodulators which operate in the time domain (in that sense like a PI machine), not in the frequency domain.
Therefore any machine which demodulates in the frequency domain does not infringe.
In a multifrequency machine, I am not aware of any substantial advantage of demodulating in the time domain, other than that the "front end" can be gated to exclude reactive signals from the resistive amplification channels, allowing higher gain.
---SUMMARY-----
This patent does not concern anyone who is doing pulse induction, or anyone doing a multifrequency machine which demodulates in the frequency domain, or anyone doing an MF machine which demodulates in the time domain and which has a transmitter timing ratio less than 4:1.
The patented invention does not appear to have a substantial advantage over the alternative ways of doing things.
--Dave J.