Modulation and Demodulation Circuit

• US 20110007846A1
• Filed: 07/10/2009
• Published: 01/13/2011
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Onespan North America Incorporated (OneSpan, Inc.)
• Original Assignee: Vasco Data Security Incorporated (OneSpan, Inc.)
• Inventors: Marien, Dirk
• Granted Patent: US 8,115,538 B2
• Time in Patent Office: Days
• US Class Current: 375/319
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: H03D 1/08 by means of non-linear two-pole elements H03D1/22, H03D1/26, H03D1/28 take precedence
• CPC Class Codes: H03D 1/10 of diodes
• CPC Class Codes: H03D 2200/0011 Diodes
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

Abstract

The invention relates to the field of modulation and demodulation circuits, such as envelope detectors used to demodulate amplitude-modulated (AM) signals and amplitude-shift-keying (ASK) signals. By judiciously coupling an analog circuit comprising one resistor and two capacitors which are judiciously dimensioned to a port of a digital component, an extremely compact envelope detector can be obtained, which achieves demodulation of a binary ASK signal for direct coupling into a digital input port. Accordingly, a very compact envelope detector may advantageously 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, the electrical personalization of which happens after the production of the card-like housing. The digital port may additionally be used to modulate the backscattered wave, by switching the voltage of the diode port to the system ground level. In this way, the apparatus is advantageously equipped with a wireless bidirectional half-duplex transmission system.

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 digital component, 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 provides to the circuit an electrical equivalent of a diode connected to a reference voltage.

2. The apparatus of claim 1, wherein said circuit lacks a diode associated with said demodulating.

3. The apparatus of claim 1, wherein said first port and said second port are ports of the same digital component.

4. The apparatus of claim 3, wherein said digital component is a microprocessor.

5. The apparatus of claim 1, wherein said electrical signal is modulated in amplitude modulation.

6. The apparatus of claim 5, wherein said electrical signal is modulated in amplitude shift keying.

7. The apparatus of claim 6, wherein said electrical signal is modulated in binary amplitude shift keying.

8. The apparatus of claim 1, wherein said reference voltage is the system ground voltage.

9. The apparatus of claim 1, wherein said reference voltage is the system power supply voltage.

10. The apparatus of claim 1, wherein said circuit is a reduced envelope detector.

11. The apparatus of claim 1, wherein said electrical signal has a carrier frequency of approximately 16 MHz.

12. The apparatus of claim 1, wherein said electrical signal is modulated at a baud rate of 1 kHz.

13. The apparatus of claim 1, wherein said electrical signal is received through inductive coupling.

14. The apparatus of claim 13, wherein the coupling distance is approximately 0.005 meter.

15. The apparatus of claim 13, further comprising a tuned circuit for effectuating said inductive coupling.

16. The apparatus of claim 15, further comprising a switching assembly for modulating the reactance of said tuned circuit.

17. The apparatus of claim 16, wherein said switching assembly is integrated in said second port.