User's Manual

EXHIBIT 2 PAGE 12 OF 17
TX RX Systems Inc. Manual 7-9257 (version 1) 11/03/00 Page 12
bands. The combline output filters suppress any IM
products that may be inadvertently generated.
OLC Assembly 3-9417
Signals that exceed the maximum input rating may
either damage the repeater amplifier or cause it to
generate intermodulation products that exceed the
maximum allowed by the FCC or other regulatory
agencies. The addition of the Output Level Control
(OLC) circuit helps prevent this from happening.
The OLC Assembly (part # 3-9417) is set to main-
tain a maximum single carrier output power from
the 6-watt amplifier of +25 dBm. The assembly
contains a signal sampling and detection section, a
DC control section and a PIN diode RF attenuator
section which is applied ahead of all amplification.
OLC circuitry should not be considered a panacea
for a poor system design. One undesirable side
affect of OLC is that the signal level of all signals
being processed by the branch will be reduced
when this circuitry is activated. This means that the
performance of the system is actually decreased
for all signals in a branch as long as gain reduction
is taking place for any one signal in that branch.
The implication is that OLC has been designed to
handle short term or transient overdrive episodes
only.
This circuitry actuates when the predetermined
maximum output level is reached. The output
power level is sensed with a signal sampler that is
built into the OLC assembly. The sampler outputs
to a detector circuit which generates a DC voltage
that is proportional to the output power level. The
proportional DC voltage from the detector is then
applied to a control circuit which develops a voltage
used to control a variable electronic attenuator. The
electronically controlled attenuator is placed at the
input end of the amplifier chain and reduces the
incoming signal by an amount necessary to keep
the power from exceeding the maximum safe level.
The gain reduction range is typically 5 - 40 dB
which is more than adequate for most real life situ-
ations.
The OLC assembly is divided into three shielded
compartments; one housing the RF/DC converter,
the second a DC control circuit, and the third con-
taining the RF attenuator circuit. A test point is pro-
vided for measuring the DC voltage applied to the
RF attenuator (see figure 6). Regulated VDC is
RF to DC
Converter
DC Control
Circuit
RF Attenuator
RF Input
RF Output
OLC
Voltage
Test Point
VDC
Input
RF Input
-50 dB
Sampler
Port
(Shown with
dustcover on)
RF Output
Figure 6: OLC Assembly 3-9417.