Southern Avionics Company SD100 Manual Do Utilizador
SD SERIES TRANSMITTER
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Southern Avionics Company
SECTION 2
2.2.3 Analog I/O and Audio PCB
SLP10005 Analog I/O
The Analog I/O and PWM PCB consists of several sub sections which accomplish the following functions:
Analog Signal Input
Analog Signal Output
Modulation Detection
Analog Signal Output
Modulation Detection
The Analog Input Section is essentially a 40 channel low pass filtered analog MUX. These multiplexed
inputs are actually an expansion scheme which adds additional analog inputs to those already available to the
controller/ monitor. This allows the overall system to be expanded to control larger multi-section transmitters up to
1KW at present.
Signals such as RF Power Amplifier voltage, current and temperature, to name only a few, are sampled and read in to
the Controller / Monitor via this MUX. The multiplexing process is directly controlled by the Controller Monitor.
controller/ monitor. This allows the overall system to be expanded to control larger multi-section transmitters up to
1KW at present.
Signals such as RF Power Amplifier voltage, current and temperature, to name only a few, are sampled and read in to
the Controller / Monitor via this MUX. The multiplexing process is directly controlled by the Controller Monitor.
The Analog Signal Output Section is a smaller MUX facilitating output control expansion. As an example,
an analog control signal originating in the Controller / Monitor such as PWR_LEVEL ( a 0.0 to 4.0 volt DC level) is
sent to this Sample and Hold MUX channel 1. Via this channel the MUX outputs this particular level to the PA Power
Supply which dictates the output power level of the transmitter. The Next Channel of the MUX can control yet
another module requiring some level of control voltage if needed.
sent to this Sample and Hold MUX channel 1. Via this channel the MUX outputs this particular level to the PA Power
Supply which dictates the output power level of the transmitter. The Next Channel of the MUX can control yet
another module requiring some level of control voltage if needed.
The Modulation Detector receives a detected sample of the RF envelope form the bridge circuit and converts
it into two DC levels called Vmax and Vgref. The Controller / Monitor reads in these levels and subtracts Vgref from
Vmax to derive Vmin. Vmax and Vmin are then used in the standard modulation formula to obtain modulation
percentage in the same way as someone would calculate it manually using an oscilloscope. This circuit is intended to
free the Controller / Monitor from having to sample large amounts of envelope data to statistically calculate the
percentage thereby facilitating more of a real-time monitoring of modulation. Correction curves are embedded to
resolve linearity issues arising from the detection process.
Vmax to derive Vmin. Vmax and Vmin are then used in the standard modulation formula to obtain modulation
percentage in the same way as someone would calculate it manually using an oscilloscope. This circuit is intended to
free the Controller / Monitor from having to sample large amounts of envelope data to statistically calculate the
percentage thereby facilitating more of a real-time monitoring of modulation. Correction curves are embedded to
resolve linearity issues arising from the detection process.