External Leveling Used With the Optional Step Attenuator
Some external leveling applications require low output power
from the synthesizer. The synthesizer automatically uncouples the
attenuator from the ALC system for all external leveling points.
P O W E R
For example, leveling the output of a 30 dB gain amplifier to a level
of -10 dBm requires the output of the synthesizer to be around
-40 dBm when leveled. At some frequencies this level is beyond the
range of the ALC modulator alone. If so, the LOW UNLVLED warning
message is displayed. Inserting 40 dB of attenuation results in an
ALC level of 0 dBm, which is well within the range of the ALC. At
20 GHz,30 dB attenuation is a better choice as it results in an ALC
level of -10 dBm. This gives a margin for AM or other functions
that vary the power level.
For optimum display accuracy and minimum noise, the ALC
level should be greater than -10 dBm. This is achieved by using
attenuation equal to the tens digit of output power. Example:
desired output power = -43 dBm; use:
1. Press POWER (MENU).
To obtain flatness corrected power refer to "Optimizing Synthesizer
Performance, Creating and Applying the User Flatness Correction
Array," later in this section.
Note the display. It shows:
L E V E L
40 dB , ALC -3 dBm