User's Manual

P.G. TM0040AE
2-1
SECTION 2. THEORY OF OPERATION
2.0 GENERAL
As explained in Section 1, the A289 is a bidirectional amplifier, which provides 20 dB of
gain in both the cellular and PCS wireless transmit and receive bands. The block diagram
of the amplifier is shown in Figure 2-1.
2.1 DESCRIPTION
2.1.1
- The unit is composed of two diplexers, two independent bidirectional amplifiers and
alarm and voltage regulation circuits.
2.1.2
- The diplexers U1 and U2 combine the cellular and PCS bidirectional amplifiers. In
each bidirectional amplifier additional bandpass diplexers separate signals for the uplink
and downlink amplifiers.
2.1.3
- The bias condition of devices in the amplifiers is monitored. If the bias changes
outside certain limits a fault condition is indicated. The downlink RF output power in each
band is also monitored. If the power in either band drops below established limits a FAULT
condition is indicated.
When a FAULT condition occurs the unit transmits the unit identification (or "Fault Code")
by two level amplitude modulation of a low frequency carrier placed on the cable center
conductor. The signal is transmitted as a short burst repeated at approximately 80 second
intervals while the fault condition persists. The fault code can be reprogrammed as
described in Section 4.6. While a NORMAL condition exists the amplifier transmits an OK
code at intervals of approximately 80 minutes.
2.1.4
- The voltage regulators take 15 - 24 VDC input and provide 12 VDC and 10 VDC
outputs. A zener diode provides transient protection against voltage spikes.
2.1.5
- The unit provides DC continuity from J1 to J2 to allow downstream cable powered
amplifiers to receive their power from upstream power sources such as the PS212 and
PS213. In addition, status signals from downstream cable powered amplifiers are passed
through the amplifier from J1 to J2.