US4344150A
Expired / Lapsed
US
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Coherent noise cancelling filter
Assignee: Newmont Corp
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Filing: 1980-07-10
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Granted: 1982-08-10
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Expires: 2000-07-10
Abstract
Abstract Apparatus and method for removing coherent noise from an electrical signal, such as powerline noise, and operating in real time. An operational amplifier with digital filter and a low pass filter in the feedback loop, with the digital filter providing a feedback signal corresponding to the coherent noise in the absence of the desired signal. In the preferred embodiment, an integrating type digital filter with digital memory, and alternative embodiments with condenser memory.
Inventors
- 👤 George H. McLaughlin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 23:51
CPC Classifications
H; H03; H03H; H03H17/00; H03H17/02; H03H17/0283; H03H17/0286; H03H17/0289
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
108 words
In a coherent noise cancelling filter, the combination of: means defining a circuit input and a circuit output; an operational amplifier connected between said circuit input and circuit output; a feedback circuit connected from the output of said operational amplifier to the input thereof, said feedback circuit including a digital filter and a low pass filter connected in series between said operational amplifier output and input, said digital filter including memory means and first switching means for connecting said operational amplifier to said memory means; and timing means for operating said first switching means to interconnect said operational amplifier output and said memory means during a predetermined time.
Claim 2
Dependent Claim
108 words
In a coherent noise cancelling filter, the combination of: means defining a circuit input and a circuit output; an operational amplifier connected between said circuit input and circuit output; a feedback circuit connected from the output of said operational amplifier to the input thereof, said feedback circuit including a digital filter and a low pass filter connected in series between said operational amplifier output and input, said digital filter including memory means and first switching means for connecting said operational amplifier to said memory means; and timing means for operating said first switching means to interconnect said operational amplifier output and said memory means during a predetermined time.
Claim 3
Dependent Claim
20 words
A coherent noise cancelling filter as defined in claim 1 wherein said digital filter is an integrating type digital filter.
Claim 4
Dependent Claim
26 words
A coherent noise cancelling filter as defined in claim 2 wherein said digital filter includes an integrator between said first switching means and said memory means.
Claim 5
Dependent Claim
68 words
A coherent noise cancelling filter as defined in claim 3 wherein said integrator includes a capacitor, and said digital filter includes second switching means for shunting said capacitor, and said timing means includes means for closing first switching means during an integrating period and then opening said first switching means and closing said second switching means at a subsequent time to set said integrator to the zero state.
Claim 6
Dependent Claim
92 words
A coherent noise cancelling filter as defined in claim 3 wherein said digital filter includes an analog-to-digital converter, an adder, and a digital-to-analog converter, and said memory means includes a first memory and a second memory, with said first and second memories and adder connected in a series loop, means connecting the output of said integrator as an input to said analog-to-digital converter, means connecting the output of said analog-to-digital converter as an input to said adder, and means connecting the junction of said memories as an input to said digital-to-analog converter.
Claim 7
Dependent Claim
43 words
A coherent noise cancelling filter as defined in claim 5 wherein said low pass filter has a substantially constant time delay in its pass band, and including means connecting the output of said digital-to-analog converter as an input to said low pass filter.
Claim 8
Dependent Claim
19 words
A coherent noise cancelling filter as defined in claim 6 wherein said low pass filter is a Bessel filter.
Claim 9
Dependent Claim
36 words
A coherent noise cancelling filter as defined in claim 5 including timing means for shifting data from said first memory to said digital-to-analog converter prior to shifting data from said first memory to said second memory.
Claim 10
Dependent Claim
22 words
A coherent noise cancelling filter as defined in claim 8 wherein said first and second memories are first in first out memories.
Claim 11
Dependent Claim
20 words
A coherent noise cancelling filter as defined in claim 3 including an oscillator providing clock signals for said timing means.
Claim 12
Dependent Claim
18 words
A coherent noise cancelling filter as defined in claim 10 wherein said oscillator operates at a fixed frequency.
Claim 13
Dependent Claim
26 words
A coherent noise cancelling filter as defined in claim 10 wherein said oscillator operates at a variable frequency related to the frequency of the coherent noise.
Claim 14
Dependent Claim
43 words
A coherent noise cancelling filter as defined in claim 2 wherein said low pass filter has a substantially constant time delay in its pass band, and including means connecting the output of said digital filter as an input to said low pass filter.
Claim 15
Dependent Claim
19 words
A coherent noise cancelling filter as defined in claim 13 wherein said low pass filter is a Bessel filter.
Claim 16
Dependent Claim
31 words
A coherent noise cancelling filter as defined in claim 1 wherein said digital filter includes an analog-to-digital converter, and said timing means includes means for controlling the output of said converter.
Claim 17
Dependent Claim
39 words
A coherent noise cancelling filter as defined in claim 1 including means for reading data from said memory means and for writing data in said memory means, and means for varying the time between said reading and writing operations.
Claim 18
Dependent Claim
75 words
A coherent noise cancelling filter as defined in claim 1 wherein said digital filter memory means includes a plurality of condenser memory units, and corresponding input and output switches for each condenser memory unit, said first switching means including said input switches, circuit means for connecting each of said output switches to said low pass filter, and said timing means including means for closing said input switches in sequence and said output switches in sequence.
Claim 19
Dependent Claim
22 words
A coherent noise cancelling filter as defined in claim 17 wherein said condenser memory units includes a condenser connected to circuit ground.
Claim 20
Dependent Claim
23 words
A coherent noise cancelling filter as defined in claim 17 wherein said condenser memory units includes an operational amplifier connected as an integrator.
Claim 21
Dependent Claim
72 words
A process for cancelling coherent noise in a signal which has an information period and a no information period, said noise havng a fundamental frequency and harmonics thereof, including the steps of: during a no information period, storing the signal, including the noise fundamental and lower harmonics, in memory; and during a subsequent information period, combining the stored signal with the then existing signal in cancelling relation providing the desired output signal.
Claim 22
Dependent Claim
72 words
A process for cancelling coherent noise in a signal which has an information period and a no information period, said noise havng a fundamental frequency and harmonics thereof, including the steps of: during a no information period, storing the signal, including the noise fundamental and lower harmonics, in memory; and during a subsequent information period, combining the stored signal with the then existing signal in cancelling relation providing the desired output signal.
Claim 23
Dependent Claim
46 words
The process as defined in claim 20 including during the no information period, integrating the output signal during an integrating period prior to storage in memory, converting the integration result to a digital value, and storing the digital value in memory to provide the stored signal.
Claim 24
Dependent Claim
31 words
The process as defined in claim 21 including during both of said periods converting the output from memory to an analog signal, and filtering the analog signal to remove higher harmonics.
Claim 25
Dependent Claim
64 words
The process as defined in claim 22 including during both of said periods transferring data from a first memory unit of the memory to a second memory unit of the memory of a first time and transferring the data from the first memory unit to a digital-to-analog converter at a second time prior to said first time to provide a compensation for system delay.
Claim 26
Dependent Claim
35 words
The process as defined in claim 20 including during the no information period dividing the signal to be stored into a plurality of time segments and storing each time segment separately in sequence in memory.
Claim 27
Dependent Claim
16 words
The process as defined in claim 24 inclduing storing each signal time segment in a condenser.
Claim 28
Dependent Claim
17 words
The process as defined in claim 24 including storing each signal time segment in an integrating amplifier.
Claim 29
Dependent Claim
21 words
The process as defined in claim 24 including storing each signal time segment in a digital first in first out memory.
Claim 30
Dependent Claim
24 words
The process as defined in claim 24 including during both of said periods reading each stored signal time segment from memory separately in sequence.
Claim 31
Dependent Claim
25 words
The process as defined in claim 28 including varying the time between reading from memory and storing in memory to provide compensation for system delay.
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) | 1985-08-09 | 1986-02-08 | 1986-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-08-09 | 1990-02-08 | 1990-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-08-09 | 1994-02-08 | 1994-08-10 | $7700.00 | Window Closed / Lapsed |