User's Manual

12 68P80801E35-B 5/1/2002

Power Amplifier (PA) EBTS System Manual - Vol 2

PA Theory of Operation

DC/Metering Board (QUAD PA Only)

The DC/Metering Board in the QUAD Radio serves the same function as it does

in other radios. However, its circuitry is modiﬁed for compatibility with the

QUAD Station. As a result, its logic circuitry is operated at 3.3 VDC.

In addition to the functions listed for non-QUAD versions above, the following

meter points are ported to the SPI bus:

❐ A and B Currents

❐ Thermistor (for PA temperature sensing circuit on the DC/Metering Board)

❐ Voltage Variable Attenuator Circuit (900 MHz QUAD version)

❐ PA Bias Enable Circuitry (900 MHz QUAD version)

Linear Driver Module

40W-800 MHz, 70W-800 MHZ and 800 MHZ QUAD PAs

The Linear Driver Module (LDM) ampliﬁes the low-level RF signal from the

Exciter. The LDM consists of a two-stage cascaded Class AB ampliﬁer, with the

ﬁnal stage in a parallel conﬁguration.

See Table 2 for the approximate input and output levels of the various LDMs. The

LDM output is fed to the RF Splitter/DC Distribution Board via an Interconnect

Board.

900 MHz PA

The Linear Driver Module (LDM) ampliﬁes the low-level RF signal from the

Exciter. The LDM consists of a three-stage, cascaded, Class AB ampliﬁer, with the

ﬁrst two stages conﬁgured as distributed ampliﬁers and the ﬁnal stage in a

push-pull conﬁguration. This output is fed directly to the RF Splitter/DC

Distribution Board.

See Table 2 for the approximate input and output power of the 900 MHz LDM.

The LDM output is fed to the RF Splitter/DC Distribution Board via the

Interconnect Board.

1500 MHz PA

The Linear Driver Module (LDM) takes the low level RF signal and ampliﬁes it.

The LDM consists of a four stage, cascaded, Class AB ampliﬁer, with the ﬁnal

stage conﬁgured in push-pull conﬁguration. This output is fed directly to the RF

Splitter/DC Distribution Board.

See Table 2 for the approximate input and output power of the 1500 MHz LDM.