infrared receiver ir rx output waveform

Posted on Feb 5, 2014

In the picture above, Oscium`s iMSO-104 oscilloscope is measuring the output waveform of an infrared receiver (IR Rx). The iPad and iMSO are functioning as the oscilloscope for measuring the receiver`s output signal as the relative alignment between transmitter and receiver varies. There are two waveforms captured on the oscilloscope screen. Trace 1, the Reference trace (in grey)

infrared receiver ir rx output waveform
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is the full scale Rx output from a 0 degree, on axis Rx/Tx alignment. The active measurement trace (in green) is being measured as the IR transmitter is rotated off axis with the receiver. You can witness this action in this short video clip complete with audio. Turn up your speakers! The infrared transmitter and receiver are set 12-18  apart from each other on a flat, horizontal surface. When you think about signal strength for wireless devices like cell phones, radios, televisions, and satellites, you think of how the antennas on the receiver and transmitter units are aligned. For this application, however, we don`t have antennas. Instead of parabolic dishes, weird metal shapes etched in a circuit board, or telescoping wands that are mechanical structures obviously functioning as antennas, the infrared receiver and transmitter units rely on a special class of diodes for their antennas. The figure below shows the oscilloscope screen displaying the strongest and weakest signals measured at the receiver`s output without triggering the alarm. When the transmitter is perfectly aligned with the receiver, the output waveform`s peak-to-peak voltage is at its maximum value. I used the oscilloscope`s reference capture function to save the trace and preserve it for display on the screen. As demonstrated in the video clip, I can rotate the transmitter about thirty degrees off axis from the receiver before tripping the receiver`s...

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