Modulation and demodulation circuit
View Patent ↗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.
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.
2. The apparatus of claim 1 , wherein said first port and said second port are ports of the same digital component.
3. The apparatus of claim 2 , wherein said digital component is a microprocessor.
4. The apparatus of claim 1 , wherein said electrical signal is modulated in amplitude modulation.
5. The apparatus of claim 4 , wherein said electrical signal is modulated in amplitude shift keying.
6. The apparatus of claim 5 , wherein said electrical signal is modulated in binary amplitude shift keying.
7. The apparatus of claim 1 , wherein said reference voltage is the system ground voltage.
8. The apparatus of claim 1 , wherein said reference voltage is the system power supply voltage.
9. The apparatus of claim 1 , wherein said circuit is a reduced envelope detector.
10. The apparatus of claim 1 , wherein said electrical signal has a carrier frequency of approximately 16 MHz.
11. The apparatus of claim 1 , wherein said electrical signal is modulated at a baud rate of 1 kHz.
12. The apparatus of claim 1 , wherein said electrical signal is received through inductive coupling.
13. The apparatus of claim 12 , wherein the coupling distance is approximately 0.005 meter.
14. The apparatus of claim 12 , further comprising a tuned circuit for effectuating said inductive coupling.
15. The apparatus of claim 14 , further comprising a switching assembly for modulating the reactance of said tuned circuit.
16. The apparatus of claim 15 , wherein said switching assembly is integrated in said second port.