Outdoor Broadband Repeater – Model: OAR02-010
IM456213-10 Rev –
5
2.0 CIRCUIT DESCRIPTION
The OAR02-010 Repeater consists of the following circuits or modules:
1.
Input low noise amplifier (LNA) and AGC circuit.
2. Power
Amplifier
3.
Monitoring and Diagnostic Circuits.
4.
Power Supply Circuits.
Microwave isolators and filters are used as necessary to ensure the stability and purity of
transmitted signals.
2.1 Low Noise Amplifier and AGC Circuit
The input signal to the repeater is amplified by a low noise amplifier (LNA). The purpose of
the amplifier is to minimize the repeater noise figure (and thus obtain the best possible
output Carrier to Noise ratio) by providing enough gain to compensate for the losses of the
circuit elements in front of the power amplifiers (filters, attenuators, etc.).
The Microwave AGC Circuit consists of an AGC driver circuit and the microwave voltage
controlled attenuator included in the input LNA.
The repeater's output signal is sampled and fed to the AGC circuit, where it is detected by
a coaxial tunnel diode detector. The detector output is then amplified and conditioned to
drive the LNA attenuator.
The microwave detector is temperature compensated to minimize output level variation
with temperature.
The AGC module has one switch and three adjustments.
The AGC/MGC switch located near the middle of the module has three positions:
1.
AGC. In this position the microwave AGC is on.
2.
OFF. In this position the attenuation is at a minimum.
3.
MGC. In this position the Manual AGC is on.
The three adjustments are as follows:
1.
The "AGC ADJUST" is a potentiometer that adjusts the AGC threshold voltage.
2.
The "MGC ADJUST" is a potentiometer that controls the microwave attenuation
when the switch is in the MGC position.
The "DETECTOR BALANCE" is a potentiometer that allows you to set the voltage at the
detector test point to zero when there is no input signal.
2.2 Power
Amplifier
The power amplifier is powered by +12 VDC. The temperature of the power amplifier is
controlled by a heat sink. The gain of the amplifier is 55 dB and the current draw is 4.5 A.
