Demodulator and method for demodulating a modulated carrier signal

• US 8,792,846 B2
• Filed: 04/06/2010
• Issued: 07/29/2014
• Est. Priority Date: 04/06/2010
• Status: Active Grant

• Current Assignee: Infineon Technologies AG, Technische Universitat Munchen
• Original Assignee: Infineon Technologies AG, Technische Universitat Munchen
• Inventors: Kargl, Walter, Ehrlich, Edmund
• Primary Examiner(s): West, Lewis
• Assistant Examiner(s): Chan, Richard
• Application Number:
  US12/755,094
• Publication Number:
  US 20110244811A1
• Time in Patent Office: 1,575 Days
• Field of Search: 329/361, 329/347, 329/348, 329/363, 329/304, 329/306, 455/73, 455/130, 455/293, 455/76, 455/77, 375/324, 375/355
• US Class Current: 455/293
• CPC Class Codes: H04L 25/068 by sampling faster than the nominal bit rate
• CPC Class Codes: H04L 27/2338 using sampling H04L27/2331 - H04L27/2335 take precedence

Abstract

A demodulator includes a sampler configured to sample a plurality of first amplitude values of a modulated carrier signal using a constant sampling frequency and a plurality of second amplitude values of the modulated carrier signal at different times using the same constant sampling frequency. The constant sampling frequency is equal to a carrier frequency of the modulated carrier signal with a tolerance of +/−1% of the carrier frequency.

Claims

1. A demodulator comprising:

a sampler configured to sample a plurality of first amplitude values of a modulated carrier signal using a constant sampling frequency and a plurality of second amplitude values of the modulated carrier signal at different times using the same constant sampling frequency; and

wherein a time a first amplitude value of the plurality of first amplitude values is determined and a time a temporal directly following a second amplitude value of the plurality of second amplitude values is determined comprises a time difference so that for each pair of first and second amplitude values at least an absolute value of the first amplitude value or an absolute value of the temporal directly following the second amplitude value is equal to or larger than 50% of a maximal absolute value of an amplitude of the modulated carrier signal between the first amplitude value and a temporal directly following the first amplitude value or between the first amplitude value and a temporal directly preceding the first amplitude value.

2. A demodulator according to claim 1, wherein the constant sampling frequency is equal to a carrier frequency of the modulated carrier signal with a tolerance of +/−

1% of the carrier frequency.

3. A demodulator according to claim 1, wherein the time difference is equal to a quarter of the period of oscillation of the modulated carrier signal with a tolerance of +/−

1% of the period of oscillation.

4. A demodulator according to claim 1, wherein the sampler comprises a first and a second analog-digital-converter, wherein the first analog-digital-converter is triggered by a sampling signal comprising the constant sampling frequency and the second analog-digital-converter is triggered by the sampling signal delayed by the time difference, wherein the first analog-digital-converter is configured to sample and provide the plurality of first amplitude values and the second analog-digital-converter is configured to sample and provide the plurality of second amplitude values.

5. A demodulator according to claim 1, wherein the sampler comprises an analog-digital-converter and a 1-to-4 multiplexer, wherein the analog-digital-converter is triggered by a sampling signal comprising a frequency equal to four times the constant sampling frequency to obtain and provide a plurality of amplitude values of the modulated carrier signal to the 1-to-4 multiplexer, wherein the 1-to-4 multiplexer is configured to select every fourth amplitude value of the plurality of amplitude values to obtain and provide the plurality of first amplitude values and to select every fourth plus one amplitude value of the plurality of amplitude values to obtain and provide the plurality of second amplitude values.

6. A demodulator according to claim 5, wherein the sampler comprises a 2-bit counter triggered by the sampling signal and configured to control the 1-to-4 multiplexer.

7. A demodulator according to claim 1, comprising a down-sampler configured to obtain and provide a first down-sampled digital signal with a predefined bit rate by selecting first amplitude values from the plurality of first amplitude values with a down-sampling frequency according to the predefined bit rate and configured to obtain and provide a second down-sampled digital signal with the predefined bit rate by selecting second amplitude values of the plurality of second amplitude values with the same down-sampling frequency.

8. A demodulator according to claim 7, wherein the predefined bit rate is equal to a bit rate of a modulation of the modulated carrier signal or an integer multiple of the modulation of the modulated carrier signal.

9. A demodulator according to claim 7, comprising a second down-sampler configured to obtain and provide a third down-sampled digital signal with the predefined bit rate by selecting first amplitude values different from the first amplitude value selected by the first down-sampler with the same down-sampling frequency and configured to obtain and provide a fourth down-sampled digital signal with the predefined bit rate by selecting second amplitude values different from the second amplitude value selected by the first down-sampler with the same down-sampling frequency.

10. A demodulator according to claim 9, wherein the first and the second down-samplers are configured to select amplitude values so that a time a first amplitude value is selected by the first down-sampler and a time a first amplitude value is selected by the second down-sampler comprises a down-sampling time difference and so that a time a second amplitude value is selected by the first down-sampler and a time a second amplitude value is selected by the second down-sampler comprises the same down-sampling time difference, wherein the down-sampling time difference depends on the predefined bit rate.

11. A demodulator according to claim 9, comprising a digital signal processor configured to obtain and provide a digital bitstream based on the plurality of first amplitude values and the plurality of second amplitude values based on the first down-sampled digital signal and the second down-sampled digital signal of the first down-sampler or based on the third down-sampled digital signal and the fourth down-sampled digital signal of the second down-sampler.

12. A demodulator according to claim 1, comprising a first and a second analog-digital-converter, a phase shifter, a first and a second down-sampler and a digital signal processor, wherein the first analog-digital-converter is connected to the first down-sampler and the second down-sampler, wherein the second analog-digital-converter is connected to the first down-sampler and the second down-sampler, wherein the first down-sampler and the second down-sampler are connected to the digital signal processor, wherein the phase shifter is connected to the second analog-digital-converter, wherein the modulated carrier signal is provided to the first and the second analog-digital-converter, wherein a sampling signal comprising the constant sampling frequency is provided to the first analog-digital-converter and the phase shifter, wherein the first analog-digital-converter is configured to provide the plurality of first amplitude values to the first and the second down converter, wherein the second analog-digital-converter is configured to provide the plurality of second amplitude values to the first and the second down-sampler, wherein the first down-sampler is configured to provide a first down-sampled digital signal and a second down-sampled digital signal to the digital signal processor, and wherein the second down-sampler is configured to provide a third down-sampled digital signal and a fourth down-sampled digital signal to the digital signal processor.

13. A demodulator according to claim 1, comprising an analog-digital-converter, a 1-to-4 multiplexer, a 2-bit counter, a first down converter, a second down converter and a digital signal processor, wherein the analog-digital-converter and the 2-bit counter are connected to the 1-to-4 multiplexer, wherein the 1-to-4 multiplexer is connected to the first and the second down-sampler, wherein the first and the second down-sampler are connected to the digital signal processor, wherein the modulated carrier signal is provided to the analog-digital-converter, wherein a sampling signal comprising a frequency of four times the constant sampling frequency is provided to the first analog-digital-converter and the 2-bit counter, wherein the analog-digital-converter is configured to provide a plurality of amplitude values to the 1-to-4 multiplexer, wherein the 1-to-4 multiplexer is configured to provide the plurality of first amplitude values to the first and the second down-sampler and provide the plurality of second amplitude values to the first and the second down-sampler, wherein the first down-sampler is configured to provide a first down-sampled digital signal and a second down-sampled digital signal to the digital signal processor and wherein the second down-sampler is configured to provide a third down-sampled digital signal and a fourth down-sampled digital signal to the digital signal processor.

14. A demodulator according to claim 1, wherein the modulated carrier signal is a load modulated carrier signal.

15. A demodulator comprising:

a means for sampling a modulated carrier signal configured to sample a plurality of first amplitude values of a modulated carrier signal using a constant sampling frequency and a plurality of second amplitude values of the modulated carrier signal at different times using the same constant sampling frequency,

wherein the time a first amplitude value of the plurality of first amplitude values is determined and the time a temporal directly following a second amplitude value of the plurality of second amplitude values is determined comprises a time difference so that for each pair of first and second amplitude values, at least an absolute value of the first amplitude value or an absolute value of the temporal directly following the second amplitude value is equal to or larger than 50% of a maximal absolute value of an amplitude of the modulated carrier signal between the first amplitude value and a temporal directly following the first amplitude value or between the first amplitude value and a temporal directly preceding the first amplitude value.

16. A transceiver comprising:

a demodulator comprising a sampler configured to sample a plurality of first amplitude values of a modulated carrier signal using a constant sampling frequency and a plurality of second amplitude values of the modulated carrier signal at different times using the same constant sampling frequency, wherein a time a first amplitude value of the plurality of first amplitude values is determined and a time a temporal directly following a second amplitude value of the plurality of second amplitude values is determined comprises a time difference so that for each pair of first and second amplitude values at least an absolute value of the first amplitude value or an absolute value of the temporal directly following the second amplitude value is equal to or larger than 50% of a maximal absolute value of an amplitude of the modulated carrier signal between the first amplitude value and a temporal directly following the first amplitude value or between the first amplitude value and a temporal directly preceding the first amplitude value; and

an oscillator unit configured to provide an oscillator signal comprising a carrier frequency, wherein the transceiver is configured to transmit a signal with the carrier frequency and to receive the modulated carrier signal, wherein the constant sampling frequency is equal to the carrier frequency of the oscillator signal with a tolerance of +/−

1% of the carrier frequency.

17. A transceiver according to claim 16, wherein the transceiver is a part of a proximity-coupling device or a contactless proximity reader.

19. A method according to claim 17, further comprising:

selecting first amplitude values from the plurality of first amplitude values with a down-sampling frequency according to a predefined bit rate to obtain and provide a first down-sampled digital signal with the predefined bit rate;

selecting second amplitude values from the plurality of second amplitude values with the down-sampling frequency according to the predefined bit rate to obtain and provide a second down-sampled digital signal with the predefined bit rate;

selecting first amplitude values different from the first amplitude values selected for the first down-sampled digital signal with the same down-sampling frequency to obtain and provide a third down-sampled digital signal with the predefined bit rate; and

selecting second amplitude values different from the second amplitude values selected for the second down-sampled digital signal with the same down-sampling frequency to obtain and provide a fourth down-sampled digital signal with the predefined bit rate.

18. A method for demodulating a modulated carrier signal, comprising:

sampling a plurality of first amplitude values of the modulated carrier signal using a constant sampling frequency; and

sampling a plurality of second amplitude values of the modulated carrier signal at different times using the same constant sampling frequency,

wherein a time a first amplitude value of the plurality of first amplitude values is determined and a time a temporal directly following a second amplitude value of the plurality of second amplitude values is determined comprises a time difference so that for each pair of first and second amplitude values, at least an absolute value of the first amplitude value or an absolute value of the temporal directly following the second amplitude value is equal to or larger than 50% of a maximal absolute value of an amplitude of the modulated carrier signal between the first amplitude value and a temporal directly following the first amplitude value or between the first amplitude value and a temporal directly preceding the first amplitude value.