User's Manual

ManualsBrandsPowerwave Technologies ManualsElectronicsMulticarrier PCS Power Amplifier

044-05077 Rev. A

4-1

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 table

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 G3S-1900-80 amplifier is a linear, feed-forward power amplifier that operates in the 60 MHz

frequency band from 1930 MHz to 1990 MHz. It is designed to operate in a maximum of two

continuous frequency blocks in the PCS band or an instantaneous bandwidth of 20 MHz. A typical

two-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 module. 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 70 watts

(one amplifier module in a subrack unit) to 140 watts (two amplifier modules), with -65 dBc third

order intermodulation distortion (IMD).

The output from each amplifier is an amplified composite signal of approximately 80 watts before

combiner losses. All phase and gain corrections are performed on the signal(s) in the individual

amplifier modules. In a two-module system, the amplifier outputs are fed to a power combiner and

combined to form a composite RF output of up to 140 watts. 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.

4-5. G3S-1900-80 AMPLIFIER MODULE

The amplifier module, figure 4-2, has an average output of 80 watts power (800 watts peak

power) with intermodulation products suppressed to better than -65 dBc below carrier levels. The

amplifier provides an amplified output signal with constant gain and phase by adding approximately

25 dB of distortion cancellation on the output signal. Constant gain and phase is maintained by

continuously comparing active paths with passive references, and correcting for small variations

through the RF feedback controls. All gain and phase variations, for example those due to

temperature, are reduced to the passive reference variations. The amplifier module is comprised

of:

Section

Summary of content (4 pages)

PAGE 1
Section PRINCIPLES OF OPERATION 4 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 table 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.
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Preamplifiers Main amplifier Error amplifier Two feed-forward loops with phase-shift and gain controls DC/DC power regulator Alarm monitoring, control, and display panel VVA 2 ACTIVE POWER COMBINER RF IN J9 POWER SPLITTER SPLITTER & SIGNAL DIST. ASSY. 500-01435 MCA 1 17 MCA 2 17 5 100 COUPLER BPF RF OUT J2 4 SIGNAL DISTRIBUTION 500-01467 5 COMBINER ASSY 500-01434 12 30 IN-RUSH RMS DET.
PAGE 3
The primary function of the first loop is to provide an error signal for the second loop. The primary function of the second loop is to amplify the error signal to cancel out spurious products developed in the main amplifier. The input signal is amplified by a preamplifier and fed to a coupler and delay line. The signal from the coupler is fed to the attenuator and phase shifter in the 1st loop.
PAGE 4
range of the loop control, a loop fault will occur. The alarms are displayed on the front panel indicators and output via a 21-pin connector on the rear of the module to the subrack summary board for subsequent remote monitoring via the ALARMS connector. Refer to paragraph 2-5.1 as well as figure 2-2 and table 2-1 for a description of the ALARMS connector. 4-5.4. AMPLIFIER MODULE COOLING Although each amplifier module contains its own heat sink, it is cooled with forced air.