Modulation and demodulation circuit
First Claim
1. An apparatus for processing a modulated electrical signal, the apparatus comprising:
- at least one digital component having a first port and a second port, the second port providing the electrical equivalent of a diode connected to a reference voltage; and
an analog circuit for receiving and demodulating the modulated electrical signal, the analog circuit coupled to the first port and the second port of the at least one digital component, the received modulated electrical signal clamped to the reference voltage by the electrical equivalent of a diode in the at least one digital component, the analog circuit configured to provide the demodulated signal to the first port.
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Accused Products
Abstract
The invention relates to 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, a compact envelope detector can be obtained, which achieves demodulation of AM signals for direct coupling into a digital input port. Accordingly, a compact 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, capacitive, or radiative. An example of such a device is a credit card sized authentication token.
13 Citations
25 Claims
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1. An apparatus for processing a modulated electrical signal, the apparatus comprising:
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at least one digital component having a first port and a second port, the second port providing the electrical equivalent of a diode connected to a reference voltage; and an analog circuit for receiving and demodulating the modulated electrical signal, the analog circuit coupled to the first port and the second port of the at least one digital component, the received modulated electrical signal clamped to the reference voltage by the electrical equivalent of a diode in the at least one digital component, the analog circuit configured to provide the demodulated signal to the first port. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An apparatus for processing a modulated electrical signal, the apparatus comprising:
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a microprocessor having a first port and a second port, the second port providing the electrical equivalent of a diode connected to a reference voltage; and an analog circuit for receiving and demodulating the modulated electrical signal, the analog circuit including a first node coupled directly to the first port and a second node coupled directly to the second port, the received modulated electrical signal clamped to the reference voltage at the second node by the electrical equivalent of the diode in the microprocessor, the analog circuit configured to provide the demodulated signal via the first node to the first port of the microprocessor. - View Dependent Claims (24, 25)
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Specification