Comtech EF Data PCB-4300 - Manual (Page 37)

PCB-4300 1:2 Phase Combiner Revision 2
Operation and Adjustment Procedures MN/PCB4300.IOM
3–7
3.4 Single Frequency Alignment (as necessary)
IMPORTANT
This alignment procedure should be attempted only if there has been a
replacement of one of the SSPAs or other critical component (such as the
PCB-4300) since the time that the system was aligned at the factory.
This particular procedure is for an application that requires operation only over a small fraction of
the possible amplifier bandwidth. The alignment procedure for narrow band operation is less
complex than alignment for full bandwidth – see Section 3.5 for the Full Bandwidth Alignment
procedure.
The equipment required for this procedure is identical to that as described in Section 3.3; the
exception being that this procedure also requires use of the Phase Shifter Adjustment Tool Kit
(screwdriver and socket) provided with the system.
The procedure is basically divided into two parts: Gain Equalization and Phase Equalization. It is
recommended that the user first review Section 3.3 for details of the test methods and remote
control commands and queries that will be utilized in this procedure.
3.4.1 Gain Equalization
The gains of the individual SSPAs will be equalized by use of the “offline” or “standby” test
coupler and AOF settings. The offline port is used because it will give a reading of the output of
an individual amplifier.
Observe the following:
Step Procedure
1 Select the frequency at which it is desired to align the system. Apply a CW signal to
the input of the PCB-4300 at a level that will give a system output power of
approximately 10 dB below the combined P1dB. For example, for a 14-14.5 GHz
system with a combined Prated of 53dBm (individual SSPA=50 dBm) and a system
gain of 65 dB, the input source would be set to a level of 53dBm – 65 – 10 = -22 dBm.
2 Attach one channel of the power meter to the Offline Power Test Coupler (refer to
Figure 3-1). Make sure the power meter has been appropriately calibrated.
3 Execute remote serial command ATT=0.00 to the PCB-4300. This ensures the
system attenuation is set to 0 dB.
4 Execute serial remote command AGI= to the PCB-4300. This command performs a
coarse equalization of the gains according to a factory calibration value stored in each
individual SSPA; reads this value from each of the three SSPAs; then adjusts the
Amplitude Offset (AOF1, AOF2, and AOF3) levels of the two SSPAs with the higher
gain to match the unit with the lowest gain.
For example, if the factory calibrated gains were SSPA#1=75 dB, SSPA#2=73dB,
and SSPA#3=76dB, the AGI= command would result in the following offsets:
AOF1=2.00, AOF2=0.00, and AOF3=3.00.
5 Measure the gain (or output level) of each individual SSPA at the desired frequency by
using serial remote command FRC= to alternately send the output of each SSPA to the
Offline Test Port Coupler.
The table that follows is intended as a worksheet to help equalize the gains. (Note that
the AOF level can be queried via serial remote command (where X=PCB-
4300 address, and Y=1, 2, or 3 – the individual SSPA offset in question.)