IMD
The IMD measurement function is selected by pressing the
FUNCTION IMD button. It is available in both digital and analog
modes, but only if the Intermodulation Distortion Option is installed.
The ATS-1 Dual Domain can be purchased with or without this
option, or the option can be added at a later time.
The IMD measurement conforms to the SMPTE and DIN testing
standards. These standards call for a low-frequency tone to be mixed
with a high-frequency tone at a 4:1 amplitude ratio. The signal is then
sent through the device-under-test. Next the low-frequency tone is
filtered out and the high-frequency tone is sent through an AM
demodulator. After bandwidth-liming to 700 Hz, the demodulated
signal is measured. This is the intermodulation distortion. It is
measured as a percentage or dB difference between the amplitudes of
the high-frequency tone and the demodulated remainder.
Figure 4-23. Main panel in IMD function
GENERATOR
MONITORS
B
A
INPUT
RANGING
INPUT
TERMINATION
INPUT
TERMINATION
LCD DISPLAY
SECONDARY
READING
DETECTOR
INTERNAL
JUMPER
INPUT
MONITOR
SPEAKER/
HEADPHONE
READING
MONITOR
CHANNEL A
CHANNEL B
PRIMARY
READING
DETECTOR
IMD
DEMODULATOR/
FILTER
Figure 4-24. Block diagram of the IMD measurement
4 Functions
IMD Function Descriptions
4-26 ATS-1 Dual Domain User's Manual
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