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40
Fig. 4-4 ACPR Measurement
k) Limit setting:
The limit test function can be applied so as to easily observe whether the adjacent channel power is beyond the set
range. Press [Measure], [ACPR] and [More 1/2] to enter the ACPR limit test setting menu.
Press [Upper Limit] and enter the upper limit with number keys.
Press [Lower Limit] and enter the lower limit with number keys.
l) Enable the limit test function:
Press [Limit Test Off On] to enable the limit test function. If the adjacent channel power is beyond the set limits, the
screen background will become red for indication.
4 Third-order IM distortion measurement
1) Definition of third-order IM distortion
Mutual interference between equipment in common in crowd operating environment of the communications system.
For example, second-order and third-order IM distortion is common in narrow-band systems. When there are two
signals (F
1
and F
2
) in one system, they and second harmonic distortion signals generated by them (2F
1
and 2F
2
)
mix and become third-order IM products 2F
2
-F
1
and 2F
1
-F
2
very close to original signals, thus resulting in high-order
