DETAILED DESCRIPTION
2-19
General Description:
The Glidepath Course Power Amplifier Assembly GPA1231A consists of the following mod-
ules mounted together as shown on Fig. 2-5.
The GPA1231A receives RF signals and LF signals from the OS1221B Oscillator (Ch. 2.3)
and LF1223A low frequency generator (Ch. 2.2) respectively. The outputs from the
GPA1231A are carrier sideband (CSB) signal and sideband only (SBO) signal. Detected sam-
ples of the CSB and SBO signals and the phase feedback signal are available on the BNC
connectors on the front panel. Information about signals and status are interfaced with the
RMS.
Block Diagram:
See Figure 2-1 and Figure 2-2.
Block Description:
The PC1225B Phase Control receives the RF signal from the oscillator OS1221B and splits
this signal into two paths (90Hz and 150Hz branch). The RF phase regulator blocks ensure
correct phase relationship between the 90Hz and 150Hz modulated RF signals prior to com-
bining them into CBS and SBO signals.
The AC1226A Amplitude Control provides and controls the required LF modulation signals
(90Hz and 150Hz) for the PA 1234A power amplifiers that keeps the output RF level and
amplitude modulation constant.
The PA1234A Power Amplifier modulates the incoming RF signal from PC1225B with a 90Hz
or a 150Hz LF signal to obtain an AM-signal and amplifies the modulated signals.
The FD1236A Feedback Detector provides feedback signals for amplitude and phase correc-
tion of the 90 and 150 Hz modulated RF signals.
The CD1238A Combiner Detector combines the 90 Hz modulated RF signal and the 150 Hz
modulated RF signal in such a way that true CSB and SBO RF signals are generated. In addi-
tion, detected and filtered CSB and SBO signals for measurement purposes are provided to
the test connectors on the front panel.
Detailed description about the individual modules are found below.
2.4.1
GPA1232A Glidepath Clearance Power Amplifier Assembly
General description:
The Glidepath Course Power Amplifier Assembly GPA1231A consists of the following mod-
2
Power Amplifiers
PA1234A
1
Amplitude Control
AC1226A
1
Phase Control
PC1225B
1
Feedback Detector
FD1236A
1
Combiner Detector
CD1238A
