US3813669A
Expired / Lapsed
US
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Frequency filter circuit apparatus
Assignee: Kidde Inc
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Filing: 1972-03-27
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Granted: 1974-05-28
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Expires: 1992-03-27
Abstract
Abstract Disclosed is a sharp cutoff frequency filter. An alternating input signal derived from a source such as a Doppler detection system is fed to a threshold detector that provides a pulse output of a preselected first level when the alternating input voltage is below a predetermined input level and of a second preselected level during excursions of the alternating input above the predetermined threshold level. The two level pulse signal is next passed to a filter circuit. Within the filter, capacitive integration is provided such that energy is absorbed by a capacitor at a controlled rate when the pulse output is at the second preselected lvel and the capacitor is rapidly discharged when the threshold detector produces the first preselted output level. Thus, the energy stored in the capacitor is a measure of the total time that the second preselected digital output was produced in a particular cycle. A second threshold detector samples the energy stored in the capacitor and produces an output signal when energy in the capacitor exceeds a predetermined level. Thus, an output signal is supplied only if the alternating input signal possesses a minimum wave length and the filter circuit functions as a low pass filter. Another preferred embodiment is disclosed in which the quiescent output from the second threshold detector enables an output circuit to pass the pulse signal. The output circuit is disenabled only in the event that the alternating input signal possesses a wave length greater than a predetermined minimum length. Consequently, this second embodiment functions as a high pass filter. Additional related embodiments disclosed herein function as sharp cutoff notch and sharp cutoff band pass filters.
Inventors
- 👤 L Saunders
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 14:18
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/52; G01S13/56
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
124 words
Frequency responsive circuit apparatus comprising: source means for providing an alternating analog signal; converter circuit means for converting said alternating analog signal into a pulse signal with pulse widths dependent upon the time period during which said analog signal remains beyond a reference level; filter and control circuit means receiving said pulse signal, said filter and control circuit means comprising timing means for producing an output signal and comprising energy storage means for receiving and storing energy in said pulse signal and further comprising primary detector means for providing a primary output signal in response to predetermined minimum pulse widths of said pulse signal as determined by the energy level in said energy storage means; and output circuit means responsive to said output signal.
Claim 2
Dependent Claim
124 words
Frequency responsive circuit apparatus comprising: source means for providing an alternating analog signal; converter circuit means for converting said alternating analog signal into a pulse signal with pulse widths dependent upon the time period during which said analog signal remains beyond a reference level; filter and control circuit means receiving said pulse signal, said filter and control circuit means comprising timing means for producing an output signal and comprising energy storage means for receiving and storing energy in said pulse signal and further comprising primary detector means for providing a primary output signal in response to predetermined minimum pulse widths of said pulse signal as determined by the energy level in said energy storage means; and output circuit means responsive to said output signal.
Claim 3
Dependent Claim
24 words
An apparatus according to claim 1 wherein said energy storage means comprises R-C network means for measuring the pulse widths of said pulse signal.
Claim 4
Dependent Claim
50 words
An apparatus according to claim 2 wherein said converter circuit means comprises: threshold means receiving said analog signal and providing one output in response to amplitudes of said analog signal above a given level and a different output in response to amplitudes of said analog signal below said given level.
Claim 5
Dependent Claim
36 words
An apparatus according to claim 3 wherein said network means comprises regulator means for controlling the rate at which energy is received by said energy storage means when said threshold means is producing said one input.
Claim 6
Dependent Claim
45 words
An apparatus according to claim 4 wherein said network means comprises discharge means for removing energy from said energy storage means when said threshold means is producing said other output and at a rate much greater than the rate at which energy is received thereby.
Claim 7
Dependent Claim
45 words
An apparatus according to claim 1 wherein said timing means further comprises high pass means responsive to said primary output signal to produce said output signal only in response to pulse widths of said pulse signal that are less than said predetermined minimum pulse width.
Claim 8
Dependent Claim
50 words
An apparatus according to claim 6 wherein said converter circuit means comprises: threshold means receiving said analog signal and providing one output in response to amplitudes of said analog signal above a given level and a different output in response to amplitudes of said analog signal below said given level.
Claim 9
Dependent Claim
72 words
An apparatus according to claim 7 wherein said pulse continuity means comprises charging means to supply energy to said energy storage means when said threshold means is producing said one output and regulator means to discharge said energy storage means when said threshold is producing said other output, and said primary detector means produces said primary output in response to the absence of a predetermined energy level in said energy storage means.
Claim 10
Dependent Claim
40 words
An apparatus according to claim 1 wherein said timing means further comprises an auxiliary detector means that produces an auxiliary output only in response to a greater minimum pulse width of said pulse signal than said predetermined minimum pulse width.
Claim 11
Dependent Claim
54 words
An apparatus according to claim 9 wherein said timing means further comprises band pass means responsive to said primary and auxiliary outputs to produce said output signal in response to a pulse with of said pulse signal that is longer than said predetermined minimum pulse width and less than said greater minimum pulse width.
Claim 12
Dependent Claim
58 words
An apparatus according to claim 10 wherein said timing means further comprises a multiple input means that is triggered to produce said output signal by trailing transitions of said digital signal and inhibit means that enables said multiple input means in response to said primary output and disenables said multiple input means in response to said auxiliary output.
Claim 13
Dependent Claim
14 words
An apparatus according to claim 11 wherein said multiple input means comprises a one-shot.
Claim 14
Dependent Claim
54 words
An apparatus according to claim 9 wherein said timing means further comprises notch means responsive to said primary and auxiliary outputs to produce said output signal only in response to pulse widths of said pulse signal that are either less than said predetermined minimum pulse width or longer than said greater minimum pulse width.
Claim 15
Dependent Claim
58 words
An apparatus according to claim 13 wherein said timing means further comprises a multiple input means that is triggered to produce said output signal by trailing transitions of said pulse signal and inhibit means that disenables said multiple input means in response to said primary output and reenables said multiple input means in response to said auxiliary output.
Claim 16
Dependent Claim
14 words
An apparatus according to claim 14 wherein said multiple input means comprises a one-shot.
Claim 17
Dependent Claim
57 words
An apparatus according to claim 1 wherein said source means comprises transmitter and receiver means for directing wave energy into and receiving wave energy from a given zone, and Doppler circuit means coupled to said transmitter and receiver means and adapted to produce said analog signal in response to relative movement of objects in said given zone.
Claim 18
Dependent Claim
44 words
An apparatus according to claim 16 wherein said timing means further comprises high pass means responsive to said primary output to produce said output signal only in response to pulse widths of said digital signal that are less than said predetermined minimum pulse width.
Claim 19
Dependent Claim
15 words
An apparatus according to claim 16 wherein said output signal corresponds to said primary output.
Claim 20
Dependent Claim
40 words
An apparatus according to claim 16 wherein said timing means further comprises an auxiliary detector means that produces an auxiliary output only in response to a greater minimum pulse width of said pulse signal than said predetermined minimum pulse width.
Claim 21
Dependent Claim
54 words
An apparatus according to claim 19 wherein said timing means further comprises band pass means responsive to said primary and auxiliary outputs to produce said output signal in response to a pulse width of said pulse signal that is longer than said predetermined minimum pulse width and less than said greater minimum pulse width.
Claim 22
Dependent Claim
58 words
An apparatus according to claim 20 wherein said timing means further comprises a multiple input means that is triggered to produce said output signal by falling transitions of said pulse signal and inhibit means that enables said multiple input means in response to said primary output and disenables said multiple input means in response to said auxiliary output.
Claim 23
Dependent Claim
54 words
An apparatus according to claim 19 wherein said timing means further comprises notch means responsive to said primary and auxiliary outputs to produce said output signal only in response to pulse widths of said pulse signal that are either less than said predetermined minimum pulse width or longer than said greater minimum pulse width.
Claim 24
Dependent Claim
26 words
An apparatus according to claim 22 wherein said predetermined minimum pulse width and said greater minimum pulse width represent a frequency band centered at 120 Hertz.
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) | 1977-05-27 | 1977-11-26 | 1978-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-27 | 1981-11-26 | 1982-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-27 | 1985-11-26 | 1986-05-28 | $7700.00 | Window Closed / Lapsed |