China Electronics Technology Instruments AV3672 Series, Руководство пользователя

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Appendix
Appendix 5 Amplifier Gain Compression Measurement
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DeltaGain21 Compression point gain--linear gain (logarithmic format)
5.2.4 Compression Method
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Compression from linear gain
The reference gain is the gain of the linear zone. The target gain is calculated by subtracting the specific
compression level (1dB) from the linear gain. Example: 8.3dB-1dB=7.3dB.
➢
Compression from maximum gain
The linear zone of amplifier gain may not be fully linear. The maximum gain measured at various frequency points
is used as the reference gain (S21). The target gain is calculated by subtracting the specific compression level (1dB)
from the maximum gain.
➢
Compression in the saturated state
If the amplifier is measured in the nonlinear zone, this method can be used to better display the compression point,
as shown in the following figure.
Fig. 5.2 Schematic Diagram of Calculation of Compression in Saturated State
The maximum output power can be found at each frequency*. Then the input power is decreased until the output
power decreases by the specific value (1dB). This point is known as the compression point.
➢
Compression from return point and X/Y compression
The two compression methods are similar to each other.
The difference of the linear zone and compression point of the input power (X-axis) are utilized in the two methods.
For the Y axis:
The gain is displayed on the Y axis in the compression from the return point.
The output power is displayed on the Y axis in the X/Y compression.
The methods to search the compression point are different in two-dimensional sweep and intelligent sweep.
The following figure shows the calculation at the same frequency in the method of compression from the return
point and X/Y compression.