TECHNICAL NOTE – OPERATION OF MT4400 TWTA
08/10/2004
TN4400-3
MCL, INC.
18 of 36
4.5
HPA Gain Control (Optional)
There are a couple of ways to control the HPAs output power; they are detailed in the following
paragraphs.
4.5.1
Manual Attenuation Adjustment
On the Computer and Remote Interfaces this can be accomplished in two ways. First, a Set
Attenuator command has been provided which directly sets the level of HPA input attenuation.
Second, Increase Attenuation and Decrease Attenuation commands have been provided. These
commands adjust the attenuator from the current setting by the specified amount.
Since the attenuator is in the input side of the HPA, there is not a direct correlation between
input attenuation and output power in dBm or dBW. The difference is due to the gain
compression of the HPA. For example, a 3.0 dB change of the input attenuator will not
necessarily produce a 3.0 dB change at the HPA output.
4.5.2
Auto Power Function (Not available on some Multi-Band HPA—Please Consult MCL)
Auto Power function will regulate the RF output power within a window around the Auto
Power set level. There are several conditions that can prevent turn on of Auto Power or can
turn it off when it is on.
4.5.2.1 Initializing Auto Power (Not available on some Multi-Band HPA—Please Consult MCL)
On the Computer and Remote Interfaces an Auto Power command has been provided which
turns on Auto Power and sets the regulation level.
4.5.2.2 Conditions that will Prevent Turn On of Auto Power (Not available on some Multi-Band
HPAs—Please Consult MCL)
The HPA will refuse to perform an Auto Power command if any of the following conditions are
present.
•
If the TWTA is not in Transmit.
•
If the Forward power sample is 0000W.
•
If the Computer or Remote Interface were to set the Auto Power level to 0006W
or less.
•
If RF is Off.
