Method and system for detecting encoded radio signals
First Claim
1. An encoded radio signal detecting system comprising:
- first means for receiving an encoded radio signal and producing an analog signal having a signal amplitude varying with the amplitude of the received signal;
second means for detecting the amplitudes of a signal component and of a noise component in said analog signal and deriving the difference between the amplitudes of said signal component and said noise component;
third means for deriving a threshold amplitude based on said difference and outputting a threshold indicative signal; and
fourth means for comparing said analog signal value with said threshold indicative signal value to detect the presence and absence of said encoded radio signal.
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Accused Products
Abstract
A method for detecting an encoded radio signal involves comparing the received signal amplitude with a predetermined threshold amplitude. The difference between the received signal-component amplitude and the noise-component amplitude is derived and used to adjust the threshold amplitude. By adjustng the threshold amplitude depending upon the difference between the signal-component amplitude and the noise-component amplitude, mis-detection which could occur otherwise when the reception amplitude of the noise component is relatively high or the reception amplitude of the signal component is relatively low can be successfully and satisfactorily avoided. In order to implement the foregoing process, an encoded radio signal detecting system comprises detecting means separately detecting the signal-component amplitude and the noise-component amplitude, arithmetic means for deriving the difference between the received signal-component amplitude and the noise-component amplitude and deriving a value proportional to the derived difference, which derived value serves as a threshold amplitude, and comparator means for comparing the received signal amplitude with the threshold amplitude, thereby detecting the presence or absence of encoded radio signals.
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Citations
13 Claims
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1. An encoded radio signal detecting system comprising:
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first means for receiving an encoded radio signal and producing an analog signal having a signal amplitude varying with the amplitude of the received signal; second means for detecting the amplitudes of a signal component and of a noise component in said analog signal and deriving the difference between the amplitudes of said signal component and said noise component; third means for deriving a threshold amplitude based on said difference and outputting a threshold indicative signal; and fourth means for comparing said analog signal value with said threshold indicative signal value to detect the presence and absence of said encoded radio signal. - View Dependent Claims (2, 3, 4, 9)
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5. A method for detecting an encoded radio signal comprising the steps of:
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receiving radio signals and generating an analog signal having a value varying with the amplitude of the received radio signal; detecting the signal-component amplitude and the noise-component amplitude in the received signal and deriving the difference between said signal-component and noise-component amplitudes; deriving a threshold value based on said difference between said signal-component and said noise-component amplitudes; and comparing said analog signal value with said threshold value in order to detect the presence and absence of said encoded radio signal and producing a binary signal varying between HIGH and LOW values depending upon the presence and absence of the encoded radio signal. - View Dependent Claims (6, 7, 10)
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8. A keyless entry system for an automotive vehicle device for actuating the vehicle device, comprising:
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an electrical actuator connected to said vehicle device and responsive to a control signal to operate said vehicle device to a position ordered by said control signal; a manual switch; a transmitter transmitting a radio code signal indicative of a unique code which identifies said transmitter; a detector incorporated in said radio code signal transmitter for detecting a radio demand signal for activating said transmitter to transmit said radio code signal, said detector comparing a received signal with a predetermined threshold which varies with the difference between the signal-component amplitude and the noise-component amplitude in the received signals and outputting an activation signal for activating said radio signal transmitter when the received signal amplitude is higher than said threshold amplitude; and a controller responsive to manual operation of said manual switch to generate a radio demand signal to activate said transmitter, to transmit said radio demand signal to said transmitter, to receive said unique code indicative radio code signal from said transmitter, to compare said unique code with a preset code, and to generate said control signal when said unique code matches said preset code. - View Dependent Claims (11)
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12. An encoded radio signal detecting system comprising:
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a signal receiver means, for receiving an encoded radio signal producing an analog signal having a signal amplitude varying with the amplitude of the received signal; a detector means for comparing said analog signal value with a given threshold value to detect the presence and absence of said encoded radio signal, said detector means producing a detector signal having a first level when the presence of said encoded radio signal is detected and a second level when the absence of said encoded radio signal is detected; a first signal holding means, responsive to said first level detector signal for holding said analog signal value as a first value; a second signal holding means, responsive to said second level detector signal, for holding said analog signal value as a second value; and a threshold value derivation means, operative for deriving said given threshold value for a next cycle, said threshold value derivation means reading out said first and second values for comparing to derive a difference therebetween, and deriving said given threshold value on the basis of said difference.
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13. An encoded radio signal detecting system comprising:
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a signal receiver means, for receiving an encoded radio signal producing an analog signal having a signal amplitude varying with the amplitude of the received signal; a detector means for comparing said analog signal value with a given threshold value to detect the presence and absence of said encoded radio signal, said detector means producing a detector signal having a first level detected and a second level when the absence of said encoded radio signal is detected; a first signal holding means for holding said analog signal value as a first value, said first signal holding means being responsive to said first level detector signal for updating said first value with the value of said analog signal; a second signal holding means for holding said analog signal value as a second value, said second signal holding means being responsive to said second level detector signal for updating said second value with the value of said analog signal; and a threshold value derivation means for deriving said given threshold value, said threshold value derivation means reading out said first and second values for comparing to derive a difference therebetween, and deriving said given threshold value on the basis of said difference.
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Specification