Instruction Manual

6X Series Liquid-Cooled Transmitter Chapter 4, Circuit Descriptions
Instruction Manual, Rev. 0 4-2
A 1 GHz LO1 signal, typically -15 dBm, which is generated externally on the Frequency
Agile Upconverter Board is connected to the downconverter board at J12. The 1 GHz
LO is amplified by U9 and applied to a high pass filter, amplified by J10 and connected
to a low pass filter. The filters are designed to eliminate any other interfering signals
that might be coupled into the 1 GHz LO. The LO1 is split with one part connected to
the LO input on the U11 mixer. The other part of the LO1 signal is connected to the
LO1 sample jack J13. Also connected to the U11 mixer is the first conversion IF of
1044 MHz. The output of the U11 mixer is the 44 MHz second IF signal. This 44 MHz
second IF signal is then applied to a low pass filter to remove any out of band energy,
amplified by U12 and U15 and connected to a frequency response correction circuit
intended to compensate for any linear distortions in the downconversion path.
Adjustments R50-R52 and C79-C81 are used to control the frequency response of the
downconverter. The resulting signal is then amplified by U14 and applied to a
cascaded high pass low pass filter, which removes any out of band products that are
generated in the demodulation process. The filtered output is connected through U16
a coupler to J15 the IF output jack of the board. Typical level is -6 dBm. The coupler
provides a sample that is split. One sample output, -20 dBm, is connected to J16 the
output sample Jack of the board. The other sample output connects to a detector IC
U17 that provides a detected output level that is used in the Mute circuitry of the tray.
4.1.3 Button Board (1311306)
The Button Board provides the front panel accessed push button switch which is
illuminated by multicolored LEDs. The switch lit Blue indicates normal operation.
When the switch is lit Red, it indicates a malfunction has occurred. Pushing the
button will cause the front panel LCD on the system controller tray to display the
operating parameters of the selected power controller and/or the malfunction which
has occurred.
4.1.4 Pre-Driver Amplifier Board, Exciter, 6X (1313190)
The Pre-Driver Amplifier Board provides up to 22 dB of gain. The RF output of the
upconverter board, ≈-3dBm in level, connects to J1 the RF input jack on the pre-
driver board. The RF is connected to DS1 and DS2 and associated components
which make up a pin diode attenuator circuit that controls the output level of the
board. A gain adjust voltage, from the Exciter Controller Board, connects though L3
to the pin diodes and increases or decreases the level through the circuit and
therefore the output drive level of the exciter, upconverter, driver tray. The output
of the pin diode level control circuit is amplified by U3 and connected to the IC U2
which is a 1 Watt driver amplifier with approximately 17 dB of gain. The amplified
output of U2 is connected through a directional coupler IC U5 to the RF output jack
J2 of the board. The RF output, ≈19 dBm maximum, is cabled to the RF output jack,
J2, mounted on the rear panel of the exciter, upconverter, driver tray. A sample of
the RF from the coupler connects to U6 that generates a DC output level based on
the RF level, which is amplified by the IC U1B and fed, output level, to the Exciter
Controller Board, for metering and level control.