Signal detector and method for detecting signals having selected frequency characteristics
First Claim
1. A signal detector for monitoring ultrasonic signals having an ultrasonic frequency within a selected frequency range and operative to produce a detector output in response thereto, comprising:
- a transducer means for receiving sound signals and converting said sound signals into an electrical transducer signal;
a filter means for filtering said transducer signal to remove all frequency components thereof not within the selected frequency range to produce an input signal having an input signal frequency and an input signal amplitude;
processing circuit means responsive to said input signal for producing an intermediate signal having an intermediate signal frequency that is scaled from the input signal frequency into an audible frequency;
amplification control means responsive to said input signal for amplifying said intermediate signal proportionally to the input signal amplitude to produce a detector output signal; and
means for displaying said detector output signal.
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Abstract
A signal detector and signal detection methodology is provided to monitor oscillatory signals, such as sound signals, to produce detector output in response to the presence of target signals having a frequency within a selected frequency range, such as ultrasonic sound signals. The detector has input processing circuitry that receives the oscillatory signals and filters out those which do not fall within the selected frequency range to produce an input signal. The input signal is split into two components, a primary input component and a control component. The primary input component is amplified proportionally to the amplitude of the control component. Preferably, the primary input component is processed to produce a clean, stable intermediate signal. Here, the signal detector provides processing circuitry that passes primary input components that have amplitudes exceeding a threshold, to eliminate low level noise; the primary input components are variably amplified inversely to the amplitude thereof to produce an initial intermediate signal having a substantially uniform amplitude at the frequency of the input signal. This initial intermediate signal is processed by a Schmitt-Trigger to create a square-wave signal. The processing circuit includes a scaler sub-circuit to divide the square-wave signal by an integer, and an integrating sub-circuit integrates the resulting scaled signal to produce the intermediate signal. An amplification circuit has variable gain controlled by averaging the amplitude of the input signal by way of the control component so that the intermediate signal is amplified according to the original amplitude to produce a scaled replica of the filtered input signal. Sensitivity adjustment and visual and audible displays are used for the detector output.
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Citations
22 Claims
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1. A signal detector for monitoring ultrasonic signals having an ultrasonic frequency within a selected frequency range and operative to produce a detector output in response thereto, comprising:
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a transducer means for receiving sound signals and converting said sound signals into an electrical transducer signal; a filter means for filtering said transducer signal to remove all frequency components thereof not within the selected frequency range to produce an input signal having an input signal frequency and an input signal amplitude; processing circuit means responsive to said input signal for producing an intermediate signal having an intermediate signal frequency that is scaled from the input signal frequency into an audible frequency; amplification control means responsive to said input signal for amplifying said intermediate signal proportionally to the input signal amplitude to produce a detector output signal; and
means for displaying said detector output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for monitoring sound signals in order to indicate the presence of ultrasonic signals having a frequency within a selected frequency range, comprising the steps of:
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receiving sound signals and producing in response thereto a first electrical signal having a composite frequency and amplitude corresponding to said sound signals; filtering said first electrical signal to remove all components thereof which do not have a frequency within the selected frequency range and producing an input signal corresponding to all sound components having a frequency within said selected range; deriving a primary input component and an input control component from said input signal; processing said primary input component to produce an intermediate signal having an intermediate signal frequency that is scaled into an audible frequency range and which has a substantially uniform amplitude; amplifying said intermediate signal proportionally to the amplitude of said input control component to produce a detector output signal as an amplitude modulated scaled replica of said input signal. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification