Motorola F2265A, Owner'S Manual

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Theory of Operation
3-2
3.2 BLOCK DIAGRAM DESCRIPTION
The ATU block diagram is shown in Figure 3-1 and
described in the following sections.
3.2.1 RF MATCHING NETWORK
The RF signal from the radio is applied to the RF
Matching Network via the RF Sensor. The RF
matching network is a combination of inductors and
capacitors. The ATU changes the network parameters
by switching the inductors and capacitors in and out of
the network.
The quality of the network and its components
determines the effectiveness of the energy transfer
between the radio and the antenna. Therefore, the
network components have high-Q (quality factor) and
the tuning algorithm is very sophisticated.
3.2.2 RF SENSOR
The RF sensor samples the RF signal, converts the
samples to analog levels (between 0-5 V) and transfers
the data to the Tuner Logic. The following data is
provided on the RF signal:
•
PH-L and PH-C signals indicate whether the load is
inductive or capacitive.
•
V
g
signal indicates on which G circle on the Smith
Chart the load is located (G=
R
1
).
•
V
f
signal indicates the forward power.
•
V
r
signal indicates the reverse power.
•
An RF sample for calculating the signal frequency.
3.2.3 TUNER LOGIC
The Tuner Logic circuit performs the following
functions:
•
Detects channel change in the radio (based on DC
interrupting on the RF cable while the channel is
changed).
•
Calculates the frequency of the RF signal sample
provided by the RF sensor.
•
Controls the tuning process: it implements the
tuning algorithm and sends commands to the relay
drivers that control the matching network
components.
•
Stores the tuning state for each frequency.
•
Shorts the RF sensor outputs to the ground after
completing the tuning process. This grounding is
required for protecting the Tuner Logic circuits and
the sensor components from high power during the
normal radio transmission.
When the tuning is completed, the Tuner Logic circuit
deactivates the relay control commands and enters an
idle state.