RATE DECODER WITH ACTIVE FILTERS
First Claim
1. A decoding system for providing a control signal in response to an input of one of a plurality of selected code rates, each of said code rates coded to designate a restrictive control signal varying from a most restrictive control signal to a least restricted control signal, wherein the improvement comprises:
- a plurality of band-pass filtering means, each of said band-pass filtering means responsive to a code rate input for producing an output when the input is within the band of each of said filter means;
a plurality of comparator means each having a triggering level responsive to a corresponding one of said filter means output for producing a step signal when the amplitude of said corresponding filtering means output exceeds said triggering level;
said comparator including an amplifier triggered fOr producing its step output each time said filter output exceeds the triggering level, and cut-off for terminating the step output each time said filter output is less than said trigger level, thereby producing substantially a square wave output having a frequency in accordance with said code rate a plurality of output means, each output means coupled to a corresponding one of said comparator means for producing an output control signal when the corresponding one of said square wave outputs exceeds a minimum frequency; and
a restrictive circuit having parallel inputs from each of said band-pass filtering means and switching means governed by said output control signals from said output means, said restrictive circuit providing means for conducting only the output from said band-pass filtering means corresponding to the most restrictive control signal.
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Abstract
The decoding system provides a control signal in response to an input of one of a plurality of selected code rates. The improvement includes a band-pass filtering means for each code rate which is responsive to the input for producing the output when the rate is within the band of the filter. A comparator means has a triggering level responsive to the filter output and produces a step signal when the amplitude of the filter output exceeds the triggering level. An output means responsive to the step output of the comparator produces the control signal when the step output signal occurs at at least a minimum rate.
15 Citations
12 Claims
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1. A decoding system for providing a control signal in response to an input of one of a plurality of selected code rates, each of said code rates coded to designate a restrictive control signal varying from a most restrictive control signal to a least restricted control signal, wherein the improvement comprises:
- a plurality of band-pass filtering means, each of said band-pass filtering means responsive to a code rate input for producing an output when the input is within the band of each of said filter means;
a plurality of comparator means each having a triggering level responsive to a corresponding one of said filter means output for producing a step signal when the amplitude of said corresponding filtering means output exceeds said triggering level;
said comparator including an amplifier triggered fOr producing its step output each time said filter output exceeds the triggering level, and cut-off for terminating the step output each time said filter output is less than said trigger level, thereby producing substantially a square wave output having a frequency in accordance with said code rate a plurality of output means, each output means coupled to a corresponding one of said comparator means for producing an output control signal when the corresponding one of said square wave outputs exceeds a minimum frequency; and
a restrictive circuit having parallel inputs from each of said band-pass filtering means and switching means governed by said output control signals from said output means, said restrictive circuit providing means for conducting only the output from said band-pass filtering means corresponding to the most restrictive control signal.
- a plurality of band-pass filtering means, each of said band-pass filtering means responsive to a code rate input for producing an output when the input is within the band of each of said filter means;
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2. The decoder of claim 1 wherein said band-pass filtering means comprises:
- an active filter selectively responsive for passing its associated input code rate and attenuating all other input code rates.
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3. The decoder of claim 2 wherein said active filter includes:
- a passive filter network responsive to its associated input code rate and an operational amplifier having a feedback loop to said passive filter for maintaining the level of said passed code rate input to a level substantially equal to the input level.
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4. The decoder of claim 1 further including:
- output triggering means for each comparator responsive to said square wave output for producing said control signal.
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5. The decoder of claim 4 wherein said output triggering means comprises:
- a Schmitt trigger activated for producing a set output in accordance with said square wave signal and for producing a reset output at a different level than said set output when said square wave signal is less than the minimum rate.
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6. The decoder of claim 5 wherein said Schmitt trigger includes:
- a charging circuit including a resistor and capacitor charged for biasing the first of a plurality of transistor stages to a conductance state in accordance with the unstepped output of the comparator and discharged in accordance with the stepped output of the capacitor for biasing the transistor into a conductance state.
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7. The decoder of claim 6 wherein said Schmitt trigger includes:
- second and third transistor stages both regeneratively driven to conductance states for producing said reset output when said first stage is in a non-conductance state and both driven to a non-conductance state for producing said set output when said first transistor stage is in a conductance state.
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8. The decoder of claim 7 wherein said output triggering means further includes:
- an output device normally active for inhibiting the control signal in response to the reset output of said Schmitt trigger and deactivated for generating said control in response to the set output of said Schmitt trigger.
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9. The decoder of claim 8 wherein said output device includes:
- a transistor having a conductance and non-conductance state in accordance with the reset and set output condition of said Schmitt trigger respectively; and
a relay energized and deenergized for opening and closing its front contact in accordance with the respective conductance and non-conductance states of the transistor, the closing of said front contact providing the control signal.
- a transistor having a conductance and non-conductance state in accordance with the reset and set output condition of said Schmitt trigger respectively; and
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10. The decoder of claim 1 further including:
- a one and only circuit having an energy input and including additional switching means governed by the output means for conducting the input energy to its output only is one of said switching means is activated; and
output check means energized in accordance with the output of said one and only circuit to produce a one and only check signal.
- a one and only circuit having an energy input and including additional switching means governed by the output means for conducting the input energy to its output only is one of said switching means is activated; and
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11. The decoder of claim 10 for governing the operation of a vehicle in accordance with the control signals further including:
- a speed governor having an input varied for controlling the speed of the vehicle including;
impedance means varieD in accordance with said output means for controlling the input to said governor; and
a second restrictive circuit having its input coupled in parallel with said impedance at various levels of impedance, said restrictive circuit including further, additional switching means governed by the output means for coupling only the most restrictive impedance level to the speed governor.
- a speed governor having an input varied for controlling the speed of the vehicle including;
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12. The decoder of claim 11 wherein said second restrictive circuit includes:
- a check switching means for each of the output check means, any rate check means and third output check means and governed thereby, serially coupled with said restrictive circuit for decoupling the impedance means from the governor input unless each of the above recited check means are activated for closing said check switching means.
Specification