User Manual

MCA9129-90-A Installation & Service Manual

044-05060 Rev. C 4-1 July 2001November 2002

Section 4 Principles of Operation

4-1 Introduction

This section contains a functional description of the Multicarrier Cellular Amplifier.

4-2 RF Input Signal

The maximum input power for all carrier frequencies should not exceed the limits specified in ta-

ble 1-2. For proper amplifier loop balance, the out of band components of the input signals should

not exceed -40 dBc. The input VSWR should be 2:1 maximum (or better).

4-3 RF Output Load

The load impedance should be as good as possible (1.5:1 or better) in the working band for good

power transfer to the load. If the amplifier is operated into a filter, it will maintain its distortion

characteristics outside the signal band even if the VSWR is infinite, provided the reflected power

does not exceed one watt. A parasitic signal of less than one watt incident on the output will not

cause distortion at a higher level than the normal forward distortion (i.e. -65 dBc).

4-4 System Functional Description

The MCA9129-90MCA9129-90-A amplifier is a linear, feed-forward power amplifier that operates

in the 25 MHz frequency band from 869 MHz to 894 MHz. A typical four-module system is shown

in figure 4-1. The power output specification is listed in table 1-2. Each amplifier is a self-

contained plug-in module and is functionally independent of the other amplifier modules. The

amplifier modules are designed for parallel operation to achieve high peak power output, and for

redundancy in unmanned remote locations. Each amplifier in the system can simultaneously

transmit multiple carrier frequencies, at an average total power output of 90 watts (1 amplifier

module in a subrack unit) to 360 watts (4 amplifier modules), with -65 dBc third order intermodula-

tion distortion (IMD). Each amplifier in the system has been FCC tested to simultaneously transmit

multiple carrier frequencies, at an average total power output of 108 watts (1 amplifier module in a

subrack unit) to 430 watts (4 amplifier modules), with -60 dBc third order intermodulation distortion

(IMD). Refer to the MCR4109-1 subrack installation and service manual (044-05061) for com-

plete system level power and IMD specifications.

The output from each amplifier is an amplified composite signal of approximately 100 watts at

–65dBc IMD (120 watts at –60dBc IMD) before combiner losses. All phase and gain corrections

are performed on the signal(s) in the individual amplifier modules. In a four -module system, the

amplifier outputs are fed to a power combiner and combined to form a composite RF output of up

to 360 watts at –65dBc IMD (430 watts at –60dBc IMD). Each amplifier module has an alarm and

display board that monitors the amplifier performance. If a failure or fault occurs in an amplifier

module, it is displayed on the individual amplifier front panel.