Cable AML ITX02-2000, Operation Installation Maintenance Manual

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Indoor Broadband Transmitter – ITX02-2000
8
IM402513-10 Rev –
Microwave Low Noise Amplifier
A Low Noise Amplifier accomplishes the amplification with minimum distortion.
DC Diagnostics Circuit
Certain test points in the transmitter can be monitored externally at the Remote Monitor output
multi-pin connector on the front panel. These DC diagnostics are connected to the output
connector through a signal conditioning circuit. The signal conditioning circuit is a network of
resistors that provides short circuit protection for the transmitter diagnostic sources. The output
connector is designed for use with diagnostic test boxes such as the Cable AML DTB - 1, the
WRM-2, or the RM-2A. The test points and corresponding connector pin connections are shown
in the Transmitter Block Diagram.
Power Supply
The power supply for the MMDS Driver is +12 VDC.
2.2 Power Amplifier Chains
The power amplifier consists of four GaAs FET microwave power amplifier that amplifies the
input signal to a maximum level consistent with the Carrier to Composite Triple Beat (C/CTB)
specification. The power amplifier is protected from failure due to overheating by an internal
temperature sensor. The sensor circuit automatically switches off the amplifier input power
when the amplifier temperature exceeds 167
°
F (75
°
C). The power amplifiers are arranged in a
quadruple power configuration which results in an overall IP3 increase of 5 dB. The gain of the
amplifiers is 56 dB with an IP3 of 69.5 dBm. The amplifiers have a TTL circuit, which enables
the user to shut down the amplifiers for testing purposes. +5VDC = “ON”
2.3 Power Supply Assembly
The transmitter has a 12 VDC redundant power supply system consisting of three current-
sharing modules with hot-plug replacement capability. Each module has an 84 Amp capability.
Only two modules in each mainframe are needed to run the transmitter. A 24 VDC power
supply powers the internal downconverter and also supplies voltage to a 5 VDC voltage
regulator, which is used with the Transistor-Transistor-Logic (TTL) of the power amp. A
se12 VDC power supply is used for the Driver.
2.4 Diagnostic Circuits1
The ITX02-2000 transmitter has several connectors and switches.
Connectors - there are "test point" and "monitor" output connectors on the front panel. Their
position in the circuitry is shown in Figure 3.
1See Data Manual for nominal values of diagnostic signals.