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2.0 CIRCUIT DESCRIPTIONS
The ITX02-2000 Transmitter consists of the following circuits or modules:
1.
MMDS Transmitter Driver
2.
Power Amplifier
3.
Power Supply System (three +12 VDC current sharing modules and one +24 VDC
power supply)
4.
Monitoring and Diagnostic Circuits - connectors and switches.
5.
On-Delay Timer Assembly.
6.
Internal Downconverter.
In addition, microwave isolators and filters are used as necessary to ensure the stability and
purity of transmitted signals.
2.1 MMDS Transmitter Driver
The MMDS Driver is comprised of the following major functional circuits or modules:
1.
Local Oscillator (LO)
2.
Upconverter/Mixer
3.
Filter Assembly
4.
Microwave Low Noise Amplifier
5.
DC Diagnostics
6.
Power Supply
Local Oscillator (LO)
The microwave local oscillator is a crystal oscillator and frequency multiplier encapsulated in a
single enclosure. The output of the LO provides pump power to the signal upconverter. The LO
is powered by a +12 VDC power supply. The long-term frequency stability of the oscillator is 5
parts per million per year.
Upconverter Mixer
The translation from VHF to microwave frequencies takes place here. The mixer is also called
an "upper sideband upconverter".
frequency, which is the sum of the local oscillator and VHF input frequencies. The upconverter
also generates unwanted signals which have to be filtered out, among them the "lower
sideband", LO leakage, and others.
Filter Assembly
There are two filters. The group bandpass filter is tuned to pass the upper sideband. The notch
filter is tuned to attenuate the local oscillator leakage without affecting the output signal.
IM402513-10 Rev –
Indoor Broadband Transmitter – ITX02-2000
The desired output of the upconverter is a signal at a
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