Modulation and demodulation circuit
First Claim
1. An apparatus for processing an electrical signal, comprising a circuit for demodulating said signal and one or more digital components, wherein said circuit is coupled to a first port of one of said one or more digital components for providing a demodulated signal from said circuit to said one or more digital components, and wherein said circuit is further coupled to a second port of one of said one or more digital components, coupling said circuit to said second port providing to the circuit an electrical equivalent of a diode connected to a reference voltage, wherein said circuit lacks a diode associated with said demodulating.
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Abstract
The invention relates to the field of modulation and demodulation circuits, such as envelope detectors used to demodulate amplitude-modulated (AM) signals. By coupling an analog circuit to a port of a digital component, an envelope detector can be obtained, which achieves demodulation of AM signals for direct coupling into a digital input port. Accordingly, an envelope detector may be used in the data receiving part of a sealed device requiring post-manufacturing data transfer, in combination with additional components that provide electromagnetic coupling, such as inductive coupling, capacitive coupling, or radiative coupling. An example of such a device is a credit card sized authentication token.
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Citations
16 Claims
- 1. An apparatus for processing an electrical signal, comprising a circuit for demodulating said signal and one or more digital components, wherein said circuit is coupled to a first port of one of said one or more digital components for providing a demodulated signal from said circuit to said one or more digital components, and wherein said circuit is further coupled to a second port of one of said one or more digital components, coupling said circuit to said second port providing to the circuit an electrical equivalent of a diode connected to a reference voltage, wherein said circuit lacks a diode associated with said demodulating.
Specification