Patent attributes
A learning remote “learns” both a digital code carried by an infrared operational signal as well as a timing characteristic (for example, time period) of a carrier used to modulate the operational signal. When the photodiode of the learning remote is close to the transmitter of the remote to be learned from, a low frequency saturation current is superimposed on the intelligence signal. Rather than using a fixed reference voltage to detect when the carrier component of the intelligence signal transitions, an adaptive reference voltage (VAR) is used. A comparator compares a photocurrent voltage to VAR. Because VAR is maintained between the envelope of positive peaks and the envelope of negative peaks of the photocurrent voltage despite changes in the low frequency current, the comparator detects each transition of the carrier component. A microcontroller timer determines the time between transitions output by the comparator and thereby determines the timing characteristic.
