Patent US4720701A successfully refreshed from Google Patents.
US4720701A
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System with enhanced signal detection and discrimination with saturable magnetic marker
Assignee: Checkpoint Systems Inc
•
Filing: 1986-01-02
•
Granted: 1988-01-19
•
Expires: 2006-01-02
Abstract
Abstract An antipilferage system is provided with an improved signal processing system to prevent false alarms. This signal processing involves singly or in combination the improvements of a slew rate limited amplifier, which prevents impulse noise from ringing or being stretched by subsequent filters; a gain-controlled amplifier ahead of said slew rate limited amplifier, the gain of the gain-controlled amplifier being reduced as the noise and/or signal exceeds a minimum threshold level; a video detector which controls the gain-controlled amplifier and serves to maintain a minimum signal to noise ratio; a digital smoothing circuit which averages several "frames" of the entire signal such that random noise is averaged to zero while any signals which are synchronized with the modulation are added together; signal processing circuitry for the recognition of incoming signal pulse shape as compared to a predetermined pulse shape, the output of which is a trigger signal to an alarm. Moreover, blanking is employed to block any signals from passing through the system during specific portions of the modulation period and when no "tag" signals would normally be present in the system. A dead zone elimination circuit is also disclosed along with a power-up timed inhibit circuit to prevent false alarms when the system is turned on or when severe power line transients are present.
Inventors
- 👤 George J. Lichtblau
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:15
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2408; G08B13/2465; G08B13/2488; G08B29/00; G08B29/18; G08B29/20; G08B29/24; G08B29/26
Claims Analysis
Total Claims: 113
Claim 1
Independent Claim
205 words
Apparatus for detecting the presence of an object within an interrogation zone comprising: a marker adapted to be secured to said object; means for applying in said interrogation zone an electomagnetic field having a periodic waveform; means for monitoring said field in the vicinity of said interrogation zone and detecting disturbances to said field due to the interaction of said marker with said field so as to produce a monitor signal including pulses and noise; means for removing from said monitor signal substantially all frequency components in the vicinity of the frequency of said periodic waveform of said applied field; means for detecting pulses in the remaining frequency components of said monitor signal; signal discrimination and noise rejection means receiving said detected pulses for determining is said detected pulses were caused by said marker and, if so, to produce an alarm indication signal; said signal discrimination and noise rejection means including a slew rate limited amplifier, the maximum rate of change of voltage with respect to time of the output of said amplifier being limited to be less than a predetermined value; and means operative in response to production of said alarm indication signal for indicating the presence of said marker within said interrogation zone.
Claim 2
Dependent Claim
205 words
Apparatus for detecting the presence of an object within an interrogation zone comprising: a marker adapted to be secured to said object; means for applying in said interrogation zone an electomagnetic field having a periodic waveform; means for monitoring said field in the vicinity of said interrogation zone and detecting disturbances to said field due to the interaction of said marker with said field so as to produce a monitor signal including pulses and noise; means for removing from said monitor signal substantially all frequency components in the vicinity of the frequency of said periodic waveform of said applied field; means for detecting pulses in the remaining frequency components of said monitor signal; signal discrimination and noise rejection means receiving said detected pulses for determining is said detected pulses were caused by said marker and, if so, to produce an alarm indication signal; said signal discrimination and noise rejection means including a slew rate limited amplifier, the maximum rate of change of voltage with respect to time of the output of said amplifier being limited to be less than a predetermined value; and means operative in response to production of said alarm indication signal for indicating the presence of said marker within said interrogation zone.
Claim 3
Dependent Claim
22 words
The apparatus of claim 1 and further including a linear low-pass filter receiving the output signal of said slew rate limited amplifier.
Claim 4
Dependent Claim
41 words
The apparatus of claim 1 and further including means for generating a gain control signal, an amplifier, means for passing said pulses through said amplifier, and means for varying the gain of said amplifier in response to said gain control signal.
Claim 5
Dependent Claim
31 words
The apparatus of claim 3 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-mean-square (RMS) of the detected pulses and the noise.
Claim 6
Dependent Claim
30 words
The apparatus claim 3 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and the noise.
Claim 7
Dependent Claim
29 words
The apparatus of claim 3 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 8
Dependent Claim
50 words
The apparatus of claim 3 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds very rapidly to such peak but decays slowly to a previously low level, thereby to provide a fast-attack-slow-decay response.
Claim 9
Dependent Claim
33 words
The apparatus of claim 1 and further including a gain-controlled amplifier for amplifying said pulses and means for rapidly switching the gain of said amplifier from full gain to a very low gain.
Claim 10
Dependent Claim
19 words
The apparatus of claim 1 and further including a variable gain-controlled amplifier coupled to said slew rate limited amplifier.
Claim 11
Dependent Claim
28 words
The apparatus of claim 1 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before further signal processing.
Claim 12
Dependent Claim
31 words
The apparatus of claim 10 wherein said said signal discrimination means includes means for synchronizing the timing of the analog to digital conversion with the periodic waveform of the applied field.
Claim 13
Dependent Claim
12 words
The apparatus of claim 11 wherein said synchronizing means includes a phase-locked-loop.
Claim 14
Dependent Claim
31 words
The apparatus of claim 1 wherein said signal discrimination means includes means for providing a representation of the expected signal produced by the marker, and a memory for storing said representation.
Claim 15
Dependent Claim
12 words
The apparatus of claim 13 where said memory is a digital memory.
Claim 16
Dependent Claim
19 words
The apparatus of claim 13 wherein said memory includes one or more threshold detectors and minimum pulse width detectors.
Claim 17
Dependent Claim
54 words
The apparatus of claim 1 wherein said signal discrimination means includes means for providing a representation of the expected signal produced by the marker, a memory means for storing said representation and further including means for comparing the detected pulses with the representation in said memory to discriminate the expected marker signal from noise.
Claim 18
Dependent Claim
28 words
The apparatus of claim 1 wherein the marker is a magnetic marker and the applied field has sufficient magnetic force to cause magnetic changes in said magnetic marker.
Claim 19
Dependent Claim
26 words
The apparatus of claim 17 wherein said magnetic marker includes a strip having a length at least ten times the maximum dimensions of the cross-sectional area.
Claim 20
Dependent Claim
25 words
The apparatus of claim 17 and further including a linear low-pass filter receiving said pulses from the output of the said slew rate limited amplifier.
Claim 21
Dependent Claim
36 words
The apparatus of claim 17 and further including means for generating a gain control signal, and amplifier receiving said pulses, and means for varying the gain of said amplifier in response to said gain control signal.
Claim 22
Dependent Claim
31 words
The apparatus of claim 20 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-means-square (RMS) of the detected pulses and the noise.
Claim 23
Dependent Claim
31 words
The apparatus of claim 20 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and the noise.
Claim 24
Dependent Claim
29 words
The apparatus of claim 20 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 25
Dependent Claim
50 words
The apparatus of claim 20 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds very rapidly to such peak but decays slowly to a previously low level, thereby to provide a fast-attach-slow-decay response.
Claim 26
Dependent Claim
33 words
The apparatus of claim 17 and further including a gain-controlled amplifier for amplifying said pulses and means for rapidly switching the gain of said amplifier from full gain to a very low gain.
Claim 27
Dependent Claim
19 words
The apparatus of claim 17 and further including a variable gain-controlled amplifier coupled to said slew rate limited amplifier.
Claim 28
Dependent Claim
28 words
The apparatus of claim 17 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before further signal processing.
Claim 29
Dependent Claim
30 words
The apparatus of claim 27 wherein said signal discrimination means includes means for synchronizing the timing of the analog to digital conversion with the periodic waveform of the applied field.
Claim 30
Dependent Claim
12 words
The apparatus of claim 28 wherein said synchronizing means includes a phase-locked-loop.
Claim 31
Dependent Claim
33 words
The apparatus of claim 17 wherein said signal discrimination means includes means for providing a representation of the expected signal produced by the marker, a memory, and storing said representation in said memory.
Claim 32
Dependent Claim
12 words
The apparatus of claim 30 where said memory is a digital memory.
Claim 33
Dependent Claim
19 words
The apparatus of claim 30 wherein said memory includes one or more threshold detectors and minimum pulse width detectors.
Claim 34
Dependent Claim
56 words
The apparatus of claim 17 wherein said signal discrimination means includes means for providing a representation of the expected signal produced by the marker, a memory means for storing said representation in said memory; further including means for comparing the detected pulses with the representation in said memory to discriminate the expected marker signal from noise.
Claim 35
Dependent Claim
43 words
The apparatus of claim 17 wherein said field is alternating and wherein said detected pulses and noise are passed through a recirculating delay line integrator with the delay time of the delay line equal to the period of the alternating applied magnetic field.
Claim 36
Dependent Claim
15 words
The apparatus of claim 34 wherein said delay line includes a charge coupled device (CCD).
Claim 37
Dependent Claim
17 words
The apparatus of claim 34 wherein said recirculating delay line is synchronized to the applied magnetic field.
Claim 38
Dependent Claim
21 words
The apparatus of claim 36 and further including a phase-locked-loop synchronization of said recirculating delay line to the applied magnetic field.
Claim 39
Dependent Claim
28 words
The apparatus of claim 17 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before further signal processing.
Claim 40
Dependent Claim
30 words
The apparatus of claim 38 wherein said signal discrimination includes means for synchronizing the timing of the analog to digital conversion with the periodic waveform of the applied magnetic field.
Claim 41
Dependent Claim
12 words
The apparatus of claim 39 wherein said synchronizing means includes a phase-locked-loop.
Claim 42
Dependent Claim
35 words
The apparatus of claim 17 and further including means for inhibiting said apparatus from indicating the presence of said magnetic marker for a fixed period of time after power is turned on to said apparatus.
Claim 43
Dependent Claim
34 words
The apparatus of claim 1 wherein the marker is a resonant circuit and the applied electromagnetic field is at a freqeuncy which is swept through a range including the resonant frequency of the marker.
Claim 44
Dependent Claim
31 words
The apparatus of claim 42 and further including a linear low-pass filter receiving said pulses from the output of said slew rate limited amplifier and then through said linear low-pass filter.
Claim 45
Dependent Claim
37 words
The apparatus of claim 42 and further including means for generating a gain control signal, an amplifier receiving said pulses, and means for varying the gain of said amplifier in response to said separate gain control signal.
Claim 46
Dependent Claim
31 words
The apparatus of claim 44 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-mean-square (RMS) of the detected pulses and the noise.
Claim 47
Dependent Claim
31 words
The apparatus of claim 44 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and the noise.
Claim 48
Dependent Claim
29 words
The apparatus of claim 44 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 49
Dependent Claim
50 words
The apparatus of claim 44 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds very rapidly to such peak but decays slowly to a previously low level, thereby to provide a fast-attack-slow-decay response.
Claim 50
Dependent Claim
33 words
The apparatus of claim 42 and further including a gain-controlled amplifier for amplifying said pulses and means for rapidly switching the gain of said amplifier from full gain to a very low gain.
Claim 51
Dependent Claim
20 words
The apparatus of claim 42 and further including a variable gain controlled amplifier coupled to said slew rate limited amplifier.
Claim 52
Dependent Claim
28 words
The apparatus of claim 42 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before further signal processing.
Claim 53
Dependent Claim
31 words
The apparatus of claim 51 wherein said signal discrimination means includes means for synchronizing the timing of the analog to digital conversion with the modulation of the swept radio frequency field.
Claim 54
Dependent Claim
12 words
The apparatus of claim 52 wherein said synchronizing means includes a phase-locked-loop.
Claim 55
Dependent Claim
33 words
The apparatus of claim 42 wherein said signal discrimination means includes means for providing a representation of the expected signal produced by the marker, a memory, and storing said representation in said memory.
Claim 56
Dependent Claim
12 words
The apparatus of claim 54 where said memory is a digital memory.
Claim 57
Dependent Claim
19 words
The apparatus of claim 54 wherein said memory includes one or more threshold detectors and minimum pulse width detectors.
Claim 58
Dependent Claim
56 words
The apparatus of claim 42 wherein said signal discrimination means includes means for providing a representation of the expected signal produced by the marker, a memory means for storing said representation in said memory; further including means for comparing the detected pulses with the representation in said memory to discriminate the expected marker signal from noise.
Claim 59
Dependent Claim
257 words
Apparatus for detecting the presence of an object within an interrogation zone comprising: a marker adapted to be secured to said object; means for applying in said interrogation zone an electromagnetic field having a periodic waveform; means for monitoring said field in the vicinity of said interrogation zone and detecting disturbances to said field due to the interaction of said marker with said field so as to produce a monitor signal including pulses and noise; means for removing from said monitor signal substantially all frequency components in the vicinity of the frequency of said periodic waveform of said applied field; means for detecting pulses in the remaining frequency components of said monitor signal; receiving said pulses for determining if said detected pulses were caused by said marker and, if so, to produce an alarm indication signal; said signal discrimination and noise rejection means storing in a digital memory a representation of the signal expected when said member is present in said interrogation zone, said representation comprising a predetermined series of alternating polarity pulses which occur in a predetermined time sequence wherein each of said pulses is approximated by a rectangular voltage waveform with a predetermined minimum amplitude and with a pulse width defined as falling between a predefined minimum and maximum value, and comparing the detected pulses from said monitor to the representation in memory to discriminate the expected marker signal from noise; and means operative in response to the production of said alarm indication signal for indicating the presence of said marker within said interrogation zone.
Claim 60
Dependent Claim
257 words
Apparatus for detecting the presence of an object within an interrogation zone comprising: a marker adapted to be secured to said object; means for applying in said interrogation zone an electromagnetic field having a periodic waveform; means for monitoring said field in the vicinity of said interrogation zone and detecting disturbances to said field due to the interaction of said marker with said field so as to produce a monitor signal including pulses and noise; means for removing from said monitor signal substantially all frequency components in the vicinity of the frequency of said periodic waveform of said applied field; means for detecting pulses in the remaining frequency components of said monitor signal; receiving said pulses for determining if said detected pulses were caused by said marker and, if so, to produce an alarm indication signal; said signal discrimination and noise rejection means storing in a digital memory a representation of the signal expected when said member is present in said interrogation zone, said representation comprising a predetermined series of alternating polarity pulses which occur in a predetermined time sequence wherein each of said pulses is approximated by a rectangular voltage waveform with a predetermined minimum amplitude and with a pulse width defined as falling between a predefined minimum and maximum value, and comparing the detected pulses from said monitor to the representation in memory to discriminate the expected marker signal from noise; and means operative in response to the production of said alarm indication signal for indicating the presence of said marker within said interrogation zone.
Claim 61
Dependent Claim
37 words
The apparatus of claim 58 and further including means for generating a gain control signal, an amplifier receiving said monitor pulses, and means for varying the gain of said amplifier in response to said gain control signal.
Claim 62
Dependent Claim
30 words
The apparatus of claim 59 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-mean-square (RMS) of the detected pulses and noise.
Claim 63
Dependent Claim
30 words
The apparatus of claim 59 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and noise.
Claim 64
Dependent Claim
29 words
The apparatus of claim 59 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 65
Dependent Claim
49 words
The apparatus of claim 59 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds rapidly to such peaks but decays slowly to a previously low level, thereby to provide a "fast-attach-slow-decay" response.
Claim 66
Dependent Claim
28 words
The apparatus of claim 58 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before further signal processing.
Claim 67
Dependent Claim
23 words
The apparatus of claim 64 further including means for synchronizing said analog to digital conversion to the periodic waveform of the applied field.
Claim 68
Dependent Claim
14 words
The apparatus of claim 65 wherein said means for synchronizing includes a phase-locked loop.
Claim 69
Dependent Claim
28 words
The apparatus of claim 58 wherein the marker is a magnetic marker and the applied field has sufficient magnetic force to cause magnetic changes in said magnetic marker.
Claim 70
Dependent Claim
37 words
The apparatus of claim 67 and further including means for generating a gain control signal, an amplifier receiving said monitor pulses, and means for varying the gain of said amplifier in response to said gain control signal.
Claim 71
Dependent Claim
30 words
The apparatus of claim 68 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-mean-square (RMS) of the detected pulses and noise.
Claim 72
Dependent Claim
30 words
The apparatus of claim 68 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and noise.
Claim 73
Dependent Claim
29 words
The apparatus of claim 68 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 74
Dependent Claim
49 words
The apparatus of claim 68 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds rapidly to such peaks but decays slowly to a previously low level, thereby to provide a "fast-attack-slow-decay" response.
Claim 75
Dependent Claim
27 words
The apparatus of claim 67 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before signal processing.
Claim 76
Dependent Claim
21 words
The apparatus of claim 73 wherein said analog to digital conversion is synchronized with the periodic waveform of the applied field.
Claim 77
Dependent Claim
13 words
The apparatus of claim 74 wherein said synchronizing means includes a phase-locked loop.
Claim 78
Dependent Claim
34 words
The apparatus of claim 58 wherein the marker is a resonant circuit and the applied electromagnetic field is at a frequency which is swept through a range including the resonant frequency of the marker.
Claim 79
Dependent Claim
37 words
The apparatus of claim 76 and further including means for generating a gain control signal, an amplifier receiving said monitor pulses, and means for varying the gain of said amplifier in response to said gain control signal.
Claim 80
Dependent Claim
30 words
The apparatus of claim 77 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-mean-square (RMS) of the detected pulses and noise.
Claim 81
Dependent Claim
30 words
The apparatus of claim 77 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and noise.
Claim 82
Dependent Claim
28 words
The apparatus claim 77 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 83
Dependent Claim
49 words
The apparatus of claim 77 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds rapidly to such peaks but decays slowly to a previously low level, thereby to provide a "fast-attack-slow-decay" response.
Claim 84
Dependent Claim
28 words
The apparatus of claim 76 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before further signal processing.
Claim 85
Dependent Claim
24 words
The apparatus of claim 82 further including means for synchronizing said analog to digital conversion to the modulation of the swept radio frequency field.
Claim 86
Dependent Claim
14 words
The apparatus of claim 83 wherein said means for synchronizing includes a phase-locked loop.
Claim 87
Dependent Claim
35 words
The apparatus of claim 58 and further including a recirculating delay line integrator wherein said signals from said monitor are passed through said integrator prior to comparison with said digital representation of said monitor signal.
Claim 88
Dependent Claim
20 words
The apparatus of claim 85 wherein said delay line integrator is synchronized with the periodic waveform of the applied field.
Claim 89
Dependent Claim
17 words
The apparatus of claim 85 wherein said delay line integrator is implemented in a charge-coupled delay line.
Claim 90
Dependent Claim
21 words
The apparatus of claim 85 wherein said delay line integrator is implemented in a digital memory in conjunction with a microprocessor.
Claim 91
Dependent Claim
243 words
Apparatus for detecting the presence of an object within an interrogation zone comprising: a marker adapted to be secured to said object; means for applying in said interrogation zone an electromagnetic field having a periodic waveform; means for monitoring said field in the vicinity of said interrogation zone and detecting disturbances to said field due to the interaction of said marker with said field so as to produce a monitor signal including pulses and noise; means for removing from said monitor signal substantially all frequency components in the vicinity of the frequency of said periodic waveform of said applied field; means for detecting pulses in the remaining frequency components of said monitor signals; signal discrimination and noise rejection means for receiving said detected pulses for determining if said detected pulss were caused by said marker and, if so, to produce an alarm indication signal; means for generating a gain control signal, an amplifier, means for passing said monitor pulses through said amplifier, and means for varying the gain of said amplifier in response to said gain control signal, wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise adn responds rapidly to such peaks, but decays slowly to a previously low level, providing a fast-attack-slow-decay response; and means operative in response to production of said alarm indication signal for indicating the presence of said marker within said interrogation zone.
Claim 92
Dependent Claim
243 words
Apparatus for detecting the presence of an object within an interrogation zone comprising: a marker adapted to be secured to said object; means for applying in said interrogation zone an electromagnetic field having a periodic waveform; means for monitoring said field in the vicinity of said interrogation zone and detecting disturbances to said field due to the interaction of said marker with said field so as to produce a monitor signal including pulses and noise; means for removing from said monitor signal substantially all frequency components in the vicinity of the frequency of said periodic waveform of said applied field; means for detecting pulses in the remaining frequency components of said monitor signals; signal discrimination and noise rejection means for receiving said detected pulses for determining if said detected pulss were caused by said marker and, if so, to produce an alarm indication signal; means for generating a gain control signal, an amplifier, means for passing said monitor pulses through said amplifier, and means for varying the gain of said amplifier in response to said gain control signal, wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise adn responds rapidly to such peaks, but decays slowly to a previously low level, providing a fast-attack-slow-decay response; and means operative in response to production of said alarm indication signal for indicating the presence of said marker within said interrogation zone.
Claim 93
Dependent Claim
27 words
The apparatus of claim 89 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before signal processing.
Claim 94
Dependent Claim
21 words
The apparatus of claim 90 wherein said analog ot digital conversion is synchronized with the periodic waveform of the applied field.
Claim 95
Dependent Claim
13 words
The apparatus of claim 91 wherein said synchronizing means includes a phase-locked loop.
Claim 96
Dependent Claim
28 words
The apparatus of claim 89 wherein the marker is a magnetic marker and the applied field has sufficient magnetic force to cause magnetic changes in said magnetic marker.
Claim 97
Dependent Claim
31 words
The apparatus of claim 93 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-means-square (RMS) value of the detected pulses and noise.
Claim 98
Dependent Claim
30 words
The apparatus of claim 93 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and noise.
Claim 99
Dependent Claim
29 words
The apparatus of claim 93 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 100
Dependent Claim
27 words
The apparatus of claim 93 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before signal processing.
Claim 101
Dependent Claim
21 words
The apparatus of claim 97 wherein said analog to digital conversion is synchronized with the periodic waveform of the applied field.
Claim 102
Dependent Claim
13 words
The apparatus of claim 98 wherein said synchronizing means includes a phase-locked loop.
Claim 103
Dependent Claim
44 words
The apparatus of claim 93 wherein said field is alternating and where in said detected pulses and noise are passed through a recirculating delay line integrator with the delay time of the delay line equal to the period of the alternating applied magnetic field.
Claim 104
Dependent Claim
15 words
The apparatus of claim 100 wherein said delay line includes a charge coupled device (CCD).
Claim 105
Dependent Claim
17 words
The apparatus of claim 100 wherein said recirculating delay line is synchronized to the applied magnetic field.
Claim 106
Dependent Claim
34 words
The apparatus of claim 89 wherein the marker is a resonant circuit and the applied electromagnetic field is at a frequency which is swept through a range including the resonant frequency of the marker.
Claim 107
Dependent Claim
31 words
The apparatus of claim 103 wherein the gain of said amplifier is controlled by a signal which is proportional to the true root-mean-square (RMS) value of the detected pulses and noise.
Claim 108
Dependent Claim
30 words
The apparatus of claim 103 wherein the gain of said amplifier is controlled by a signal which is proportional to the average absolute value of the detected pulses and noise.
Claim 109
Dependent Claim
29 words
The apparatus of claim 103 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise.
Claim 110
Dependent Claim
49 words
The apparatus of claim 103 wherein the gain of said amplifier is controlled by a signal which is proportional to the peak value of the detected pulses and noise and responds rapidly to such peaks but decays slowly to a previously low level, thereby to provide a "fast-attack-slow-decay" response.
Claim 111
Dependent Claim
27 words
The apparatus of claim 103 and further including means for periodically converting said detected pulses and noise from an analog to a digital representation before signal processing.
Claim 112
Dependent Claim
24 words
The apparatus of claim 108 further including means for synchronizing said analog to digital conversion to the modulation of the swept radio frequency field.
Claim 113
Dependent Claim
14 words
The apparatus of claim 109 wherein said means for synchronizing includes a phase-locked loop.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-01-18 | 1991-07-20 | 1992-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-18 | 1995-07-20 | 1996-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-18 | 1999-07-20 | 2000-01-19 | $7700.00 | Window Closed / Lapsed |