Demodulator and Method for Demodulating a Carrier Signal

• US 20110243200A1
• Filed: 04/02/2010
• Published: 10/06/2011
• Est. Priority Date: 04/02/2010
• Status: Active Grant

• Current Assignee: Infineon Technologies AG, Technische Universitat Munchen
• Original Assignee: Infineon Technologies AG
• Inventors: Kargl, Walter, Ehrlich, Edmund
• Granted Patent: US 8,625,727 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H03M 1/1255 Synchronisation of the sampling frequency or phase to the input frequency or phase
• CPC Class Codes: H04L 2027/0036 using a recovered symbol clock
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

A demodulator includes a sampler and a trigger unit. The sampler is configured to sample a carrier signal based on a trigger signal to obtain a demodulated signal. The trigger unit is configured to detect a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal. Further, the trigger unit is configured to provide the trigger signal based on the detected zero crossing or the detected extreme value, so that the carrier signal is sampled by the sampler with a predefined phase shift to the detected zero crossing or the detected extreme value. The predefined phase shift is larger than 30° plus an integer multiple of 90° and lower than 60° plus the same integer multiple of 90° in reference to the carrier signal.

Claims

1. A demodulator comprising:

a sampler configured to sample a carrier signal based on a trigger signal to obtain a demodulated signal; and

a trigger unit configured to detect a predefined amplitude value of the carrier signal and provide the trigger signal based on the detected predefined amplitude value, so that the carrier signal is sampled by the sampler with a predefined phase shift, wherein the predefined phase shift is such that a phase shift to a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal is larger than 30°

plus an integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal.

2. A demodulator according to claim 1, wherein the predefined amplitude value of the carrier signal is a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal, and wherein the predefined phase shift is larger than 30°

plus an integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal.

3. A demodulator according to claim 1, wherein the predefined phase shift is equal to 45°

plus an integer multiple of 90°

in reference to the carrier signal with a tolerance of 5°

.

4. A demodulator according to claim 1, wherein the sampler is configured to sample the carrier signal with a sampling frequency equal to a frequency of the carrier signal with a tolerance of 10% of the frequency of the carrier signal.

5. A demodulator according to claim 1, wherein the trigger unit is configured to detect an unmodulated state of the carrier signal and detect the zero crossing of the carrier signal or the extreme value of the amplitude of the carrier signal based on the unmodulated carrier signal.

6. A demodulator according to claim 1, wherein the sampler comprises an analog-digital-converter configured to sample the carrier signal based on the trigger signal to obtain a demodulated, digital signal.

7. A demodulator according to claim 6, wherein the analog-digital-converter of the sampler is the only analog-digital-converter of the demodulator for sampling the carrier signal.

8. A demodulator according to claim 1, wherein the trigger unit comprises a phase detector and a delay unit, wherein the phase detector is configured to detect the zero crossing or the extreme value of the carrier signal and provide the trigger signal with a trigger pulse at the time the zero crossing or the extreme value is detected, wherein the delay unit is configured to delay the trigger signal according to the predefined phase shift, so that the sampler is triggered by the delayed trigger pulse to sample the carrier signal with the predefined phase shift.

9. A demodulator according to claim 1, wherein the trigger unit comprises a phase detector and a delay unit, wherein the phase detector is configured to detect the zero crossing or the extreme value of the carrier signal and provide a trigger pulse to the delay unit at the time the zero crossing or the extreme value is detected, wherein the delay unit is configured to delay a clock signal based on the trigger pulse according to the predefined phase shift to obtain the trigger signal represented by the delayed clock signal for the sampler, so that the sampler samples the carrier signal with the predefined phase shift.

10. A demodulator according to claim 9, wherein the clock signal comprises the same frequency as the carrier signal with a tolerance of 1% of the clock signal, so that the sampler is triggered by the trigger signal periodically to sample the carrier signal.

11. A demodulator according to claim 1, wherein the trigger unit comprises a phase detector and a counter, wherein the phase detector is configured to detect the zero crossing or the extreme value of the carrier signal and provide a reset pulse to the counter, wherein the counter is configured to count periodically a predefined number of count cycles and is triggered by a clock signal comprising a frequency equal to an integer multiple of the frequency of the carrier signal with a tolerance of 1% of the frequency of the clock signal, wherein the predefined number of count cycles is equal to the integer, the frequency of the carrier signal is multiplied with, wherein the counter is reset by the reset pulse to start a counting period at a reset value depending on the predefined phase shift, wherein the counter is configured to provide the trigger signal with the trigger pulse after reaching the predefined number of count cycles or a start/stop value.

12. A demodulator according to claim 1, wherein the trigger unit comprises a phase detector, a calibration unit and a counter, wherein the phase detector is configured to detect a first zero crossing and a second zero crossing or a first extreme value and a second extreme value of the carrier signal, provide a first reset pulse at the time the first zero crossing or the first extreme value is detected and provide a second reset pulse at the time the second zero crossing or the second extreme value is detected, wherein the calibration unit is configured to determine a number of count cycles to be periodically counted by the counter based on the first reset pulse, the second reset pulse and a clock signal, wherein the clock signal comprises a frequency equal to an integer multiple of the frequency of the carrier signal with a tolerance of 1% of the frequency of the clock signal, wherein the determined number of count cycles is provided to the counter as a reset value, wherein the counter is configured to divide the number of count cycles by the integer, the frequency of the carrier signal is multiplied with, for a first counting period and after counting the divided number of count cycles, the counter is configured to provide a trigger pulse to the sampler.

13. A demodulator according to claim 1, comprising a down sampler configured to provide a down sampled signal with a predefined bit rate by selecting sample values from the demodulated signal with a down sampling frequency according to the predefined bit rate.

14. A demodulator according to claim 13, wherein the predefined bit rate is equal to a bit rate of a modulation of the carrier signal or an integer multiple of the modulation of the carrier signal.

15. A demodulator according to claim 13, comprising a second down sampler configured to provide a second down sampled signal with the predefined bit rate by selecting sample values different from the sample values selected by the first down sampler with the same down sampling frequency.

16. A demodulator according to claim 15, wherein the first down sampler and the second down sampler are configured to select sample values so that a time a sample value is selected by the first down sampler and a time a sample value is selected by the second down sampler comprise a down sampling time difference, wherein the down sampling time difference depends on the predefined bit rate.

17. A demodulator according to claim 1, wherein the demodulator is part of a proximity-coupling device or a contactless proximity reader.

18. A transceiver comprising:

a demodulator comprising;

a sampler configured to sample a carrier signal based on a trigger signal to obtain a demodulated signal; and

a trigger unit configured to detect a predefined amplitude value of the carrier signal and provide the trigger signal based on the detected predefined amplitude value, so that the carrier signal is sampled by the sampler with a predefined phase shift, wherein the predefined phase shift is such that a phase shift to a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal is larger than 30°

plus an integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal; 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 based on the oscillator signal and receive the carrier signal in a modulated state or an unmodulated state.

19. A demodulator comprising:

an analog-digital-converter configured to sample a carrier signal in a modulated state based on a trigger signal to obtain a demodulated, digital signal; and

a trigger unit configured to detect a zero crossing of the carrier signal in an unmodulated state and provide the trigger signal based on the detected zero crossing, so that the carrier signal is sampled by the analog-digital-converter with a predefined phase shift of 45°

plus an integer multiple of 90°

relative to the detected zero crossing in reference to the carrier signal with a tolerance of 5°

.

20. A demodulator comprising:

means for sampling a carrier signal based on a trigger signal to obtain a demodulated signal;

means for detecting a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal; and

means for providing the trigger signal based on the detected zero crossing or the detected extreme value, so that the carrier signal is sampled by the means for sampling with a predefined phase shift to the detected zero crossing or the detected extreme value, wherein the predefined phase shift is larger than 30°

plus and integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal.

21. A method for demodulating a carrier signal comprising:

detecting a predefined amplitude value of the carrier signal;

providing a trigger signal based on the detected predefined amplitude value; and

sampling the carrier signal based on the trigger signal to obtain a demodulated signal, wherein the trigger signal is provided, so that the carrier signal is sampled with a predefined phase shift, wherein the predefined phase shift is such that a phase shift to a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal is larger than 30°

plus an integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal.

22. A method according to claim 21, wherein detecting the predefined amplitude value comprises detecting a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal, and wherein the predefined phase shift is larger than 30°

plus an integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal.

23. Method for demodulating a carrier signal comprising:

detecting a zero crossing of the carrier signal in an unmodulated state;

providing a trigger signal based on the detected zero crossing; and

sampling the carrier signal in a modulated state based on the trigger signal to obtain a demodulated, digital signal, wherein the trigger signal is provided, so that the carrier signal is sampled with a phase shift of 45°

plus an integer multiple of 90°

relative to the detected zero crossing in reference to the carrier signal with a tolerance of 5°

.

24. A computer program product comprising a computer readable medium storing program code for performing a method of demodulating a carrier signal, when the computer program product runs on a computer or a microcontroller, the method comprising:

detecting a predefined amplitude value of the carrier signal;

providing a trigger signal based on the detected predefined amplitude value; and

sampling the carrier signal based on the trigger signal to obtain a demodulated signal, wherein the trigger signal is provided, so that the carrier signal is sampled with a predefined phase shift, wherein the predefined phase shift is such that a phase shift to a zero crossing of the carrier signal or an extreme value of an amplitude of the carrier signal is larger than 30°

plus an integer multiple of 90° and

lower than 60°

plus the same integer multiple of 90°

in reference to the carrier signal.

25. A computer program product comprising a computer readable medium storing program code for performing a method of demodulating a carrier signal, when the computer program product runs on a computer or a microcontroller, the method comprising:

detecting a zero crossing of the carrier signal in an unmodulated state;

providing a trigger signal based on the detected zero crossing; and

sampling the carrier signal in a modulated state based on the trigger signal to obtain a demodulated, digital signal, wherein the trigger signal is provided, so that the carrier signal is sampled with a phase shift of 45°

plus an integer multiple of 90°

relative to the detected zero crossing in reference to the carrier signal with a tolerance of 5°

.