Demodulation and regulation concept for IR receivers
View Patent ↗A method and circuit for amplifying and demodulating amplitude-modulated signals is disclosed that amplifies a primary signal into an amplified signal, bandpass filters the amplified signal into a filtered signal, compares the filtered signal with a regulation threshold and regulates the gain of the primary signal such that peak values of the filtered signal approach the regulation threshold, compares the filtered signal with a signal threshold, and demodulates the result of the comparison. Whereby a value of the signal threshold is smaller than a value of the regulation threshold.
1. A method for amplifying and demodulating amplitude-modulated signals, the method comprising the steps of:
amplifying a primary signal into an amplified signal;
bandpass filtering of the amplified signal into a filtered signal;
comparing the filtered signal with a regulation threshold;
regulating a gain of the primary signal such that peak values of the filtered signal approach the regulation threshold;
comparing the filtered signal with a signal threshold, a value of the signal threshold being smaller than a value of the regulation threshold; and
demodulating a result of the comparison.
2. The method according to claim 1 , wherein the step of regulating the gain further includes, a step of an averaging of the peak values.
3. The method according to claim 1 , wherein the step of demodulation further includes digital filtering with discrimination and integration steps.
4. The method according to claim 3 , wherein the step of digital filtering and discrimination includes steps of measuring time periods of predetermined values of the comparison result, steps of a comparing the measured periods with an interval of permissible values, and steps of a generating output pulses for periods within an interval.
5. The method according to claim 4 , wherein the output pulses are integrated in the integration steps, the integration result is compared with a first integration threshold and/or a second integration threshold, an output signal is set in an event that the first integration threshold is exceeded and is cleared in an event that a value thereof falls below the second integration threshold.
6. The method according to claim 5 , wherein the output pulses are prolonged in a predefined fashion prior to their integration.
7. A circuit for processing amplitude-modulated signals, the circuit comprising:
an amplifier that provides an amplified signal from a primary signal;
a bandpass filter that provides a filtered signal from the amplified signal;
a regulation comparator that compares the filtered signal with a regulation threshold;
a regulator that regulates a gain of the amplifier such that peak values of the filtered signal approach the regulation threshold;
a signal comparator that compares the filtered signal with a signal threshold a value of the signal threshold being smaller than a value of the regulation threshold; and
a demodulator that demodulates a result of the comparison.
8. The circuit according to claim 7 , wherein the regulator digitally averages the peak values in simulation of a rectifying peak detector and provides the averaged peak values as control signals for the amplifier.
9. The circuit according to claim 7 , wherein the demodulator includes a digital filter with a discriminator and an integrator.
10. The circuit according to claim 9 , wherein the digital filter with the discriminator determines periods of predefined values of the comparison result and compares them with a lower threshold and an upper threshold and generates an output pulse when a period lies between the lower and upper thresholds.
11. The circuit according to claim 10 , wherein the integrator integrates the output pulses, and wherein the integrator sets a signal when the integration result exceeds a first integration threshold and clears the signal when the integration result falls below a second integration threshold.
12. The circuit according to claim 11 , wherein the integrator prolongs its input pulses prior to the integration.