Receiver and method for near field communication
In one embodiment, an apparatus is provided that includes a first circuit configured and arranged to provide a modulated carrier signal in response to a signal provided from the antenna. The modulated carrier signal conveys data using peaks or amplitudes of the carrier signal. A second circuit is configured to rectify the modulated carrier signal and integrate the rectified signal in response to a first clock signal. A third circuit is coupled to an output of the second circuit and is configured to sample the integrated signal values and provide therefrom a sample-based approximation of the modulated carrier signal.
1. An apparatus for operating with an antenna, comprising:
a first circuit configured and arranged to provide a modulated carrier signal, conveying data using peaks or amplitudes of the carrier signal, in response to a signal provided from the antenna;
a second circuit coupled to an output of the first circuit and configured and arranged to process the modulated carrier signal, in response to a first clock signal, by providing a rectified version of the modulated carrier signal and by performing an integration of the rectified version of the modulated carrier signal to produce an integrated signal having a voltage proportional to an integral of the rectified version of the modulated carrier signal with respect to time; and
a third circuit coupled to an output of the second circuit and configured and arranged to sample the integrated signal and provide therefrom a sample-based approximation of the modulated carrier signal.
2. The apparatus of claim 1 , wherein
the integrated signal has a voltage proportional to a sum of the amplitude of the modulated carrier signal over a time period; and
the modulated carrier signal is an amplitude-shift-key (ASK) modulated signal.
3. The apparatus of claim 1 , further including a smart card that includes the second circuit, wherein the first circuit is also configured and arranged to generate the first clock signal, the first clock signal is developed from the modulated carrier signal, and the second circuit is further configured and arranged to provide a signal dump operation in response to a second clock signal, the second clock signal having a frequency equal to a frequency of the first clock signal.
4. The apparatus of claim 1 , wherein the first circuit includes a sub-circuit configured and arranged to generate the first clock signal from the modulated carrier signal, the sub-circuit including:
a differential to single-ended buffer having first and second inputs respectively coupled to first and second ends of the antenna; and
a frequency divider circuit coupled to an output of the differential to single-ended buffer and configured and arranged to reduce a frequency of a signal output from the differential to single-ended buffer by a factor of N, where N>1, an output of the frequency divider circuit providing the first clock signal.
5. The apparatus of claim 1 , wherein the second circuit is further configured and arranged to provide a signal dump operation for the integration performed by the second circuit in response to a second clock signal, the second clock signal having a frequency equal to a frequency of the first clock signal.
6. The apparatus of claim 1 , wherein the second circuit is further configured and arranged to provide a signal dump operation for the integration performed by the second circuit by resetting the integration performed by the second circuit, in response to a second clock signal, the second clock signal having a frequency equal to a frequency of the first clock signal.
7. The apparatus of claim 1 , wherein the second circuit is further configured and arranged to provide a signal dump operation for the integration performed by the second circuit by at least partially erasing signal buildup within the second circuit due to the integration performed by the second circuit.
8. The apparatus of claim 1 , further including a smart card that includes each of the first circuit, the second circuit and the third circuit, wherein the third circuit is configured and arranged to sample the integrated signal in response to a third clock signal.
9. The apparatus of claim 1 , further including a smart card that includes each of the first circuit, the second circuit and the third circuit, wherein the third circuit is configured and arranged to convert analog samples of the integrated signal to digital values.
10. The apparatus of claim 1 , further including a smart card that includes the antenna, the first circuit, the second circuit and the third circuit.
11. The apparatus of claim 1 , wherein the integration is performed by a circuit having a frequency-domain transfer function that is inversely proportional to a frequency of the rectified version of the modulated carrier signal.
12. The apparatus of claim 1 , wherein
the modulated carrier signal is an amplitude modulated signal; and
the first clock signal has a frequency and phase configured to cause the second circuit to integrate portions of the rectified version of the modulated carrier signal corresponding to peaks of the amplitude modulated signal.
13. The apparatus of claim 1 , wherein the first circuit, the second circuit and the third circuit are collectively configured and arranged to provide the sample-based approximation of the modulated carrier signal without providing either a phase-locked loop or a delay-locked loop operation.
14. The apparatus of claim 1 , wherein the first circuit, the second circuit and the third circuit are collectively configured and arranged to provide the sample-based approximation of the modulated carrier signal without providing a low-pass filtering operation.
15. A method comprising:
using a first circuit, providing a modulated carrier signal received from an antenna to a second circuit, the modulated carrier signal conveying data using peaks or amplitudes of the carrier signal;
using the second circuit, processing the modulated carrier signal, in response to a first clock signal, by providing a rectified version of the modulated carrier signal and by performing an integration of the rectified version of the modulated carrier signal to produce an integrated signal having a voltage proportional to an integral of the rectified version of the modulated carrier signal with respect to time; and
using a third circuit, sampling the integrated signal and providing therefrom a sample-based approximation of the modulated carrier signal.
16. The method of claim 15 , wherein the modulated carrier signal is an amplitude modulated signal; and
further comprising:
using the first circuit, dividing a frequency of the modulated signal by a dividend to produce the first clock signal, the first clock signal indicating portions of the rectified version of the modulated carrier signal corresponding to peaks of the amplitude modulated signal; and
using the third circuit, in response to a second clock signal, the second clock signal having a frequency equal to a frequency of the first clock signal, performing a signal dump operation that resets the integration of the rectified version of the modulated carrier signal.
17. The method of claim 15 , further comprising using the third circuit to convert analog samples of the integrated signal to digital values, and wherein the integration is performed by a circuit having a frequency-domain transfer function that is inversely proportional to a frequency of the rectified version of the modulated carrier signal.
18. An apparatus comprising:
a first means for providing a modulated carrier signal received from an antenna to a second means, the modulated carrier signal conveying data using peaks or amplitudes of the carrier signal;
a second means for processing the modulated carrier signal, in response to a first clock signal, by providing a rectified version of the modulated carrier signal and by performing an integration of the rectified version of the modulated carrier signal to produce an integrated signal having a voltage proportional to an integral of the rectified version of the modulated carrier signal with respect to time; and
a third means for sampling the integrated signal and providing therefrom a sample-based approximation of the modulated carrier signal.
19. The apparatus of claim 18 , wherein
the modulated carrier signal is an amplitude modulated signal; and
the first clock signal has a frequency and phase configured to cause the second means to integrate portions of the rectified version of the modulated carrier signal corresponding to peaks of the amplitude modulated signal.
20. The apparatus of claim 18 , wherein the first means, the second means and the third means are collectively configured and arranged to provide the sample-based approximation of the modulated carrier signal without providing either a phase-locked loop or a delay-locked loop operation.