R.V.R. Elettronica TEX1000LIGHT, User Manual

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/ 30 User Manual
Rev. 1.1 - 06/07/20
TEX1000LIGHT
7.6 Power amplifier
The RF power amplification section consists in several power modules (two on
the TEX1000LIGHT ) coupled through a Wilkinson splitter and combiner using
strip-line technology.
Each RF module provides its power share using a single active element built using
LD-MOS technology. RF modules are fed by the switching power supply via the
Bias board.
The splitter splits the incoming power input signal equally to all RF modules. The
combiner combines the power output signals available at module outputs to obtain
total amplifier power.
Splitter, amplifiers and combiner have been designed to sum amplifier output power
signals in phase, so as to keep unbalance and power dissipation to a minimum.
The whole RF section is mounted on a finned heat sink with fan cooling.
7.7 LPF Board
This board incorporates a low-pass filter to keep amplifier harmonics within
permissible limits as specified by international standards.
A directional coupler is provided at filter output to measure forward and reflected
RF output power; power readings are relayed to the Interface and Bias boards to
enable processing and display.
The LPF board incorporates an RF output (having a level about -60 dB lower than
output level) which is brought to a BNC connector. This provides a convenient test
point to check carrier characteristics, but
does not ensure accurate assessment
of higher harmonics .
The filter also has a High Pass Filter section that sends the third harmonic generated
by the final stage to a termination 50 Ohm 250 W (mounted near the driver); this
stratagem helps to maintain a sufficiently high efficiency even in case of presence
of SWR in antenna.
7.8 BIAS board
The main purpose of this board is to control and correct the bias voltage of
the RF amplification section MOSFETs.
It also provides a measure of the total current drawn by the RF modules
and incorporates a dedicated circuit for power supply fault reporting.
Under normal conditions, bias voltage is adjusted according to set output
power using feedback based on actual output power reading (AGC).