US3729587A
Expired / Lapsed
US
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Voltage tunable frequency threshold circuit
Assignee: Bendix Corp
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Filing: 1971-07-12
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Granted: 1973-04-24
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Expires: 1991-07-12
Abstract
Abstract A circuit having a voltage tunable threshold generates an output signal indicative of whether an input signal frequency is above or below the threshold frequency. A ramping signal is started and terminated at predetermined points on the input signal frequency waveform. The ramp amplitude at termination is compared against a d.c. reference voltage proportional to the threshold frequency to indicate whether the input signal frequency is above or below the threshold. The threshold circuit is also shown used in an adaptive frequency shift keying demodulator. The demodulator threshold analyzes a received reference frequency and generates a d.c. reference voltage level for the frequency threshold circuit proportional to the reference frequency.
Inventors
- 👤 Gill R Mc
- 👤 C Worsham
- 👤 N Green
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:25
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/156; H04L27/1563
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
177 words
A circuit for generating output signal indicative of whether an input frequency signal is above or below a reference frequency wherein said input frequency signal includes an initial frequency tone having a predetermined relationship to a frequency approximately centrally located between a relatively higher frequency and a relatively lower frequency, comprising means for generating a first voltage level proportional to said input frequency; a source of a reference voltage level proportional to said reference frequency; means for generating a first output signal when said first voltage level is greater than said reference voltage level and a second output signal when said first voltage level is less than said reference voltage level said first and second output signal comprising said output signal; and, means responsive to said initial frequency tone for sweeping said reference voltage level through a predetermined range of values until a predetermined sequence of said first and second output signals is generated at which time said sweeping reference voltage level is held at a pre-determined relationship with the voltage level proportional to said initial frequency.
Claim 2
Dependent Claim
177 words
A circuit for generating output signal indicative of whether an input frequency signal is above or below a reference frequency wherein said input frequency signal includes an initial frequency tone having a predetermined relationship to a frequency approximately centrally located between a relatively higher frequency and a relatively lower frequency, comprising means for generating a first voltage level proportional to said input frequency; a source of a reference voltage level proportional to said reference frequency; means for generating a first output signal when said first voltage level is greater than said reference voltage level and a second output signal when said first voltage level is less than said reference voltage level said first and second output signal comprising said output signal; and, means responsive to said initial frequency tone for sweeping said reference voltage level through a predetermined range of values until a predetermined sequence of said first and second output signals is generated at which time said sweeping reference voltage level is held at a pre-determined relationship with the voltage level proportional to said initial frequency.
Claim 3
Dependent Claim
36 words
The circuit of claim 1 wherein said means for generating a first voltage level comprises timing means for generating a voltage level proportional to the time between identical points of successive cycles of said input frequency.
Claim 4
Dependent Claim
71 words
The circuit of claim 2 wherein said timing means comprises: means for generating a pulse each time one of said identical points occurs; and, means responsive to said pulse for generating a voltage ramp and terminating a previous voltage ramp, said means for comparing being responsive to said pulse for comparing the instantaneous value of said voltage ramp with said reference voltage level, said instantaneous value being said first voltage level.
Claim 5
Dependent Claim
103 words
The circuit of claim 2 wherein said timing means comprises: means for generating a strobe pulse at each occurrence of said identical point; means triggered by said strobe pulse to generate a second pulse; and, a voltage ramp generator responsive to said second pulse for terminating a preceding ramp and initiating the next ramp; and wherein said means for comparing includes means responsive to said strobe pulse for energizing said means for comparing during said strobe pulse whereby the instantaneous value of said ramp is compared with said reference voltage level during said strobe pulse, said instantaneous value comprising said first voltage level.
Claim 6
Dependent Claim
78 words
The circuit of claim 4 wherein said comparing means comprises a differentially connected amplifier energizable in a first state for generating said first output signal when said fiRst voltage level is greater than said reference level and energizable in a second state for generating said second output signal when said first voltage level is less than said reference voltage and including means for latching said amplifier in its instantaneous state during the occurrence of each said strobe pulse.
Claim 7
Dependent Claim
19 words
The circuit of claim 1 with additionally means for initializing said circuit in the absence of said input frequency.
Claim 8
Dependent Claim
87 words
The circuit of claim 1 wherein said input frequency signal includes a relatively pure frequency tone having a predetermined relationship to a center frequency approximately centrally located between a relatively higher frequency and a relatively lower frequency, said circuit additionally comprising: means responsive to said relatively pure frequency tone for sweeping said reference voltage level through a predetermined range of values; and, means responsive to said output signal for holding the instantaneous value of said sweeping reference voltage level at a level proportional to said center frequency.
Claim 9
Dependent Claim
133 words
A circuit for generating an output signal indicative of whether an input frequency signal is above or below a reference frequency comprising: threshold means responsive to said input signal attaining a preset threshold amplitude for generating a strobe pulse; means responsive to said strobe pulse for generating a second pulse; means responsive to said second pulse for initiating a voltage ramp and terminating a previous voltage ramp; a source of reference voltage level related to said reference frequency; a voter circuit which considers a plurality of said output signals and generates a final output signal in accordance therewith, said voter circuit comprising a shift register for receiving and storing said plurality of output signals; and, an output circuit for generating said final output signal in accordance with the contents of said shift register.
Claim 10
Dependent Claim
133 words
A circuit for generating an output signal indicative of whether an input frequency signal is above or below a reference frequency comprising: threshold means responsive to said input signal attaining a preset threshold amplitude for generating a strobe pulse; means responsive to said strobe pulse for generating a second pulse; means responsive to said second pulse for initiating a voltage ramp and terminating a previous voltage ramp; a source of reference voltage level related to said reference frequency; a voter circuit which considers a plurality of said output signals and generates a final output signal in accordance therewith, said voter circuit comprising a shift register for receiving and storing said plurality of output signals; and, an output circuit for generating said final output signal in accordance with the contents of said shift register.
Claim 11
Dependent Claim
53 words
The circuit of claim 8 wherein said means for comparing comprises a differentially connected amplifier having as inputs thereto said voltage ramp and said reference voltage level, said amplifier being energized by said strobe pulse to compare the instantaneous value of said voltage ramp with said reference voltage level during said strobe pulse.
Claim 12
Dependent Claim
21 words
The circuit of claim 9 wherein said amplifier includes means for latching said amplifier during the period of said strobe pulse.
Claim 13
Dependent Claim
38 words
The circuit of claim 8 with additionally means for sweeping said reference voltage level through a predetermined range of values; and, means responsive to said output signal for holding the instantaneous value of said sweeping reference voltage level.
Claim 14
Dependent Claim
114 words
A circuit for generating an output signal indicative of whether an input frequency signal is above or below a reference frequency comprising: means responsive to said input frequency attaining a preset threshold amplitude for generating a voltage ramp and terminating a preceding voltage ramp; a source of a reference voltage level related to said reference frequency and including means responsive to a predetermined state of said input signal for sweeping said reference voltage level through a predetermined range of values; and, means responsive to said input frequency attaining said preset threshold amplitude for comparing the instantaneous value of said voltage ramp with said reference voltage, the results of said comparison comprising said output signal.
Claim 15
Dependent Claim
114 words
A circuit for generating an output signal indicative of whether an input frequency signal is above or below a reference frequency comprising: means responsive to said input frequency attaining a preset threshold amplitude for generating a voltage ramp and terminating a preceding voltage ramp; a source of a reference voltage level related to said reference frequency and including means responsive to a predetermined state of said input signal for sweeping said reference voltage level through a predetermined range of values; and, means responsive to said input frequency attaining said preset threshold amplitude for comparing the instantaneous value of said voltage ramp with said reference voltage, the results of said comparison comprising said output signal.
Claim 16
Dependent Claim
34 words
The circuit of claim 12 wherein said means for sweeping includes means responsive to a predetermined sequence of a plurality of said output signals for memorizing the instantaneous value of said reference voltage level.
Claim 17
Dependent Claim
58 words
The circuit of claim 12 wherein said input signal includes an initial tone related to a center frequency between a relatively high frequency and a relatively low frequency and wherein the predetermined state of said input signal is comprised of the absence of said input signal and the subsequent preSence of said input signal including said initial tone.
Claim 18
Dependent Claim
47 words
The circuit of claim 14 wherein said predetermined sequence of a plurality of said output signals comprises a sequence of output signals indicative of no input signal and subsequent output signals indicating that said sweeping reference voltage level has attained a predetermined relationship with said ramping voltage.
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) | 1976-04-23 | 1976-10-23 | 1977-04-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-23 | 1980-10-23 | 1981-04-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-23 | 1984-10-23 | 1985-04-24 | $7700.00 | Window Closed / Lapsed |