© 2001 – Ericsson Amplifier Technologies Inc.
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4. PRINCIPLES OF OPERATION
4.1 Introduction
This section contains a functional description of the multi-carrier power amplifier. Refer
to the block diagram of the MCPA, Figure 5, located at the end of this section.
4.2 RF Input Signal
The maximum input signal for all carrier frequencies must not exceed the limits
specified in the electrical specifications. The input VSWR should be 2:1 maximum (or
better).
4.3 RF Output Load
The load impedance should be as close as possible to 50 ohms (VSWR of 1.5:1 or
less) over the 869-894 MHz operating frequency band to ensure maximum RF power
transfer to the load.
4.4 System Functional Description
The MCPA amplifier is a multi-carrier, feed forward power amplifier, which operates
from 869 to 894 MHz with a rated output power of 120W total (average). The amplifier
employs feed forward carrier cancellation circuitry, providing extremely low
intermodulation products, equal to or less than –63 dBc. The front panel of the
amplifier contains the DC ON/OFF switch, and the status LEDs. The amplifier operates
from a 26-28 VDC input power source, and provides a rear panel input/output (I/O)
control and status interface to report all faults and alarms. Relay dry contacts are
provided for the following fault conditions:
OVERPWR – Relay dry contact closure provided for remote notification in the event
that the MCPA output is greater than 2 dB above the nominal operating power level.
The MCPA power will need to be reset in order to clear this fault condition.
MINORFLT – Relay dry contact closure provided for remote notification in the event
that the MCPA has encountered a minor fault condition, which has not caused shut
down of the amplifier, but which will require attention as soon as possible in order to
ensure uninterrupted operation. A TEMP WARNING or FAN ALARM will result in a
MINORFLT condition and remote notification. The MCPA power will need to be reset in
order to clear this fault condition.
MAJORFLT – Relay dry contact closure provided for remote notification in the event of
a potentially damaging fault condition, which has resulted in shut down of the MCPA.
Activation of the LOOP ALARM, VSWR ALARM, POWER SUPPLY ALARM, TEMP
