Resonant circuit detection, measurement and deactivation system employing a numerically controlled oscillator
First Claim
1. An apparatus for measuring electrical characteristics of a resonant circuit without physically contacting the resonant circuit comprising:
- a numerically controlled oscillator for generating an alternating electric signal, the frequency of the alternating electric signal varying in accordance with a numerical frequency control signal;
a transmitting antenna connected to the numerically controlled oscillator for establishing an electromagnetic field within a measurement zone;
a receiving antenna for sensing disturbances to the electromagnetic field due to a presence of the resonant circuit within the measurement zone;
a receiver for receiving signals from the receiving antenna representative of the disturbances to the electromagnetic field and for determining a Q and a center frequency of the resonant circuit; and
a clock having a substantially fixed frequency connected to the numerically controlled oscillator for providing a frequency reference to the numerically controlled oscillator, wherein the frequency of the alternating electric signal is restricted to being an integer multiple of an integer sub-multiple of the clock frequency.
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Accused Products
Abstract
An apparatus for measuring electrical characteristics of a resonant circuit without physically contacting the resonant circuit. The EAS system includes a numerically controlled oscillator for generating an alternating electric signal, the frequency of the alternating electric signal varying in accordance with a numerical frequency control signal; a transmitting antenna connected to the numerically controlled oscillator for establishing an electromagnetic field within a measurement zone; a receiving antenna for sensing disturbances to the electromagnetic field within the measurement zone; a receiver for receiving signals from the receiving antenna representative of disturbances to the electromagnetic field and for determining the Q and center frequency of the resonant circuit; and a clock having a substantially fixed frequency connected to the numerically controlled oscillator. The frequency of the alternating electric signal is restricted to being an integer multiple of an integer sub-multiple of the clock frequency.
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Citations
18 Claims
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1. An apparatus for measuring electrical characteristics of a resonant circuit without physically contacting the resonant circuit comprising:
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a numerically controlled oscillator for generating an alternating electric signal, the frequency of the alternating electric signal varying in accordance with a numerical frequency control signal;
a transmitting antenna connected to the numerically controlled oscillator for establishing an electromagnetic field within a measurement zone;
a receiving antenna for sensing disturbances to the electromagnetic field due to a presence of the resonant circuit within the measurement zone;
a receiver for receiving signals from the receiving antenna representative of the disturbances to the electromagnetic field and for determining a Q and a center frequency of the resonant circuit; and
a clock having a substantially fixed frequency connected to the numerically controlled oscillator for providing a frequency reference to the numerically controlled oscillator, wherein the frequency of the alternating electric signal is restricted to being an integer multiple of an integer sub-multiple of the clock frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An electronic article security (EAS) system for detecting the presence of a security tag in a detection zone comprising:
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a numerically controlled oscillator for generating an alternating electric signal, the frequency of the alternating electric signal varying in accordance with a numerical frequency control signal;
a transmitting antenna connected to the numerically controlled oscillator for establishing an electromagnetic field within the detection zone;
a receiving antenna for sensing disturbances to the electromagnetic field due to a presence of the security tag within the detection zone;
a receiver for receiving signals from the receiving antenna representative of the disturbances to the electromagnetic field and for determining the presence of the security tag within the detection zone; and
a clock having a substantially fixed frequency connected to the numerically controlled oscillator for providing a frequency reference to the numerically controlled oscillator, wherein the frequency of the alternating electric signal is restricted to being an integer multiple of an integer sub-multiple of the clock frequency. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification