Comtech EF Data XPA-200 - Manual (Page 34)

XPA200-7984-I-OPT1, X-Band SSPA Installation
XPA200-7984-I-OPT1, Rev.2 2-6
2.3.2 Combined (SSPA A and SSPA B) Operation and Setup
The full powers of SSPAs A and B can be phase combined for
increased system power output. Maximum output is obtained only if
the signals of SSPA A and B have equal or close carrier magnitude
and frequency, and the relative phase between them is adjusted.
Phase adjustment of the input signals for maximum output power is
accomplished via the screw adjustment on the front panel of the
Mitec 2723B.
A procedure to maximize output power by phase combining the
outputs of SSPA A and B is given below. The procedure first
optimizes the power off-line by using the load port, and then
switches the maximized power on-line through the antenna port.
(Note of Caution: During the phase adjustment period, it is possible
to send a significant signal level to the antenna port even though
the combiner is directed to the load. Therefore, it is recommended
to perform the phase combining adjustment at low power levels or
activate any maintenance switches which may keep unwanted signal
from the actual antenna.)
1. Connect a power meter to the Mitec calibrated load measuring
port (see 2723B test data for exact calibration data).
2. Select VPC position 1, (A to Antenna, B to Load). Adjust
SSPA B input signal level and attenuation to achieve desired
output power level from SSPA B. For example, 40.0 dBm.
3. Select VPC position 3, (B to Antenna, A to Load). Adjust
SSPA A input signal level and attenuation to achieve an output
power level within +/- .3 dB of that obtained from SSPA B in step
2 above. (It may be necessary to repeat step 2 and increase
attenuation level of SSPA B if SSPA B has more gain than SSPA A.)
4. Select VPC position 4, A&B to load. Adjust the phase trimmer
on the Mitec 2723B front panel until maximum power is reached,
typically 2.7-2.95 dB above the single unit output power level.
For this example, 42.7-42.95.
5. Select VPC position 2, A&B to load, to go on-line and route
power to the antenna port.
6. Monitor the output power through the Antenna Forward
measuring port on the Mitec unit (see 2723B test data for exact
calibration data). Perform any minor trimming of the phase
shifter to maximize output power.
7. Note: Whenever a significant change in signal frequency
occurs, it will be necessary to re-adjust the phase shifter.