User's Manual
VHF UNIDIRECTIONAL AMPLIFIER TECHNICAL MANUAL
4
Class B Amplifier Module Description
Based on the philosophy of Anytime, Anywhere, and Anyplace, the unidirectional amplifier
module (UDA) is designed for an ease of use and being adaptable to various needs on the field.
Recently developed technologies are applied and with the use of modern integrated circuits and
RF components, the Comprod design ensures constant performances and reliable amplifier
unit.
Our VHF amplifier has also been designed with government agencies in mind. These are our
highest level of performance and quality for continuous duty solutions while providing
maximizing coverage.
This amplifier module is aimed for the use in buildings, tunnel, government facilities, airports,
providing the communication throughout.
The amplifier module helps to increase the coverage of RF communications in buildings or
places where RF is unable to penetrate from the base station site. The Amplifier Module can be
used in both Uplink or Downlink directions and connected to either a radiant cable, a
distributed antenna system, or to the donor antenna.
Block Diagram Details
- The VHF Amplifier module contains a Variable Gain Amplifier (VGA) followed by a fixed gain
Power Amplifier (PA). A mid-stage access allows channel filter to be inserted, in order to reject
adjacent channel signals and to improve the main signal quality.
- The VGA is basically a low noise amplifier featured Automatic Gain Control (AGC) circuit. The
AGC circuit measures composite power level at the VGA input and adjusts automatically the
gain, in order to maintain constant the signal level at the VGA output. Since the VGA output
power is constant, the PA composite output power is also maintained constant at the factory set
level.
- The VGA provides also Input Level Adjustment and Output Power Setting by mean of two
Manually Set Attenuators (MSA#1 and MSA#2).
The MSA#1 allows additional attenuation and hence maintains the VGA under linear condition
if the input signal is too strong (greater than -25dBm). It is also used for adjusting the input signal
to the optimum level (please see VGA Max Input Level and Optimum Input Level Setting).
The MSA#2 attenuator allows to adjust the VGA power, thus the PA output power can be also
changed to the desired level. An MSA#2 setting position versus VGA output power is supplied
with the unit. The PA linear gain is also provided.
- The Class-AB PA provides good performance for both linearity and efficiency. This amplifier is
heat sink mounted and produces a high compression point and 3
rd
order Intercept point.
- The unit can operate with AC or DC supplies. The main AC input accept 50/60Hz 100 to 260
Volt AC power source, then the Power Supply bloc converts AC to DC voltages for supporting