InfraRed carrier frequency?
manzana
Posts: 24
I have been playing with the Parallax Infrared receiver as the "weekend project". I got a universal remote which worked great as promised. I assumed it would have a carrier frequency (which is the frequency the IR beam gets modulated at) of around 38 Khz since this is what the passband of the receiver module is designed at. I put it on the scope here and was quite surprised to find the carrier frequency of the remote to be 57.27 khz!! I dont see how a harmonic or subharmonic of 57 khz can wind up in the 38 khz band. Perhaps the filter in the receiver module is a high pass? This would still make since since such IR signals could not occur naturally and would work fine for data transmission. Again, the remote worked fine and had a range exceeding 20 feet. Thanks for any clarification! APPLE
Comments
The only commonality that 'might' get through would be 19kHz which is 1/2 of 38kHz and 1/3 of 57kHz ...
... but that's a big stretch. I always thought that the detectors had a notch filter with an allowable bandpass of a few Khz either way, but in your case you are right, it sounds like it's only using a high-pass filter. Honestly that is surprising to me.