User's Manual

9 0 0 M H Z B I D I R E C T I O N A L A M P L I F I E R T E C H N I C A L M A N U A L
4
Block Diagram Details
- The 900 MHz Amplifier module contains a (Low Noise Amplifier) LNA designed to detect a very
weak signal. This stage is bypassed if the signal level at the input is higher than -20dBm
- The LNA is followed by an Automatic Gain Control (AGC). The AGC circuit measures composite
power level at the VGA input and adjusts the gain automatically, in order to maintain a constant
signal level at the VGA output delivered to the Power Amplifier (PA). Channel filters are inserted, in
order to reject adjacent channel signals and to improve the signal quality.
- The PA provides good performance for both linearity and efficiency. This amplifier has a heat sink
mounted to it and it has a high compression point and 3
rd
order Intercept point.
- The unit can operate with AC or DC power supplies. The main AC input accepts 50/60 Hz with a 115
to 220 V AC power source. The Power Supply Unit (PSU) converts AC to DC voltages to supply DC
power to the amplifiers, monitoring and control units. The unit can be fed directly with DC power, by
selecting the DC option on the AC/DC switch and connecting +24 to 27 V to the DC input connector.
The operator must ensure that this external DC power supply is compliant with FCC limits on radiated
and conducted emissions.
- The unit does not have a built-in UPS/Battery system. In case of inconsistency in the AC line power,
surge protection, short blackouts, high crossover time from the line AC to generator power, circuit
breaker for short circuit and overload protection, etc., an external UPS/Battery system is
recommended.
- The unit has two duplexers; one at the BTS port allowing the use for only one donor antenna for both
UL and DL. The second duplexer is mounted at the Service DAS antenna port. These duplexers
provide at least 100 dB isolation at each end between the two paths.
- A set of manual gain controls (MGC), ranging from 0 to 30 dB in 1 dB steps are also added in the
chain for additional attenuation if it is needed.