Outdoor Broadband Repeater – Model: OAR02-010
IM456313-05 Rev –
1
1.0 INTRODUCTION
The OAR02-010 repeater is a solid-state broadband multi-channel linear amplifier
designed to operate as an on-frequency repeater in the ITFS/MMDS/OFS frequency band
of 2.5 GHz to 2.686 GHz. The function of the repeater is to amplify a microwave input
signal for re-transmission at the same frequency but at higher power.
The repeater is comprised of a low noise pre-amplifier followed by a power amplifier, the
function of which is to amplify the signal to the maximum level consistent with the C/CTB
(Carrier to Composite Triple Beat) specification.
The per-channel output power of the unit decreases as the number of channels at the
input increases, so as to ensure that the output CTB distortion stays within specification.
This is accomplished by setting the AGC circuit to the correct value.
The power amplifier includes an output RF detector that serves an indicator of the total
average power output of the repeater. This amplifier is protected from failure by
overheating by an external temperature sensor. The sensor circuit automatically switches
off the amplifier input power when the amplifier temperature exceeds 158
°
F (70
°
C).
The repeater operates at 120/240 VAC, 50/60 Hz or 60 VAC. The microwave modules
are powered from a 12 volt 8.3 amp power supply.
To facilitate operational monitoring and diagnostics, the repeater has two internal
microwave-to-VHF downconverters, one connected to a sample of the repeater’s input
and to the output. The downconverted input and output signals can be continuously
monitored with a Field Strength Meter or a TV set without interruption of service.
The OAR02-010 transmitter consists of four assemblies (refer to Figure 2):
1.
Input LNA and AGC Assembly
- Input signal is band passed and fed to a Low
Noise Amplifier (LNA) with an internal microwave pin diode attenuator. It’s
purpose is to minimize the repeater noise figure (and thus obtain the best
Carrier to Noise Ratio) by providing enough gain to compensate for the losses
of circuit elements in front of the power amplifier. The Composite AGC Module
feeds the pin diode in the LNA. The purpose of the AGC is to maintain
constant average output power with varying channel loads or fades. The AGC
is implemented by a feedback loop comprised of an RF detector with an output
voltage proportional to the total average power at the repeater output. This
voltage is amplified in the Composite AGC module and then fed to the voltage
controlled pin attenuator in the LNA.
2.
Power Amplifier
- Input signal is amplified to a maximum level consistent with
the Carrier to Composite Triple Beat (C/CTB) specification by a state of the art
GaAs FET microwave power amplifier. The power amplifier is protected from
failure due to overheating by an external temperature sensor. The sensor
circuit automatically switches off the amplifier’s input power when the amplifier
temperature exceeds 158
°
F (70
°
C).
3.
Monitoring and Diagnostic Circuits
- The input and output signal can be
monitored via two ‘F’ connectors. The signals are downconverted to VHF thru
two internal downconverters. These VHF signals can then be measured with a
Field Strength Meter or a TV set. Diagnostic DC voltages can also be
continuously monitored via a 15-pin connector on the bottom of the repeater.
