Motorola F2265A, Owner'S Manual

Page: 21 / 24

Theory of Operation
3-3
Figure 3-1. ATU Block Diagram
3.2.4 LATCHES AND RELAY DRIVERS
The Latches and Relay Drivers control the components
of the matching network. The relay drivers activate the
RF relays that switch inductors and capacitors in and
out of the network. The latches keep the relays
activated after the tuning has been completed and the
relay commands have been removed.
3.3 DETAILED CIRCUIT
DESCRIPTIONS
Throughout the detailed circuit description you are
referred to the Antenna Tuner Board.
3.3.1 RF SENSOR CIRCUIT
The RF input is applied to transformer T101 via
connector J101. T101 includes two current
transformers, each of which generates a sample of the
RF input, as follows:
•
One sample is used for sensing the phase of the
input signal.
•
The other sample is used for sensing the V
g
, V
f
and
V
r
(the G circle in the Smith Chart, forward power
and reverse power, respectively).
3.3.1.1 Phase Sensor
The phase sensor measures the phase difference
between the input signal voltage and the input signal
current. A capacitor network made up of C204, C203
and C184 samples the voltage. The voltage sample is
applied to pin 6 of the T101 phase sensing transformer
and is thus added to the current sample generated in the
transformer. Pin 7 of T101 provides a vector sum of the
input signal voltage and current, while pin 5 provides
the vector difference.
Both outputs are applied to peak detectors (one is made
up of CR101, R108, R112 and C132, and the other is
made up of CR102, R109, R113 and C133). The peak
detectors generate DC voltages PH-C and PH-L, which
are proportional to the amplitudes of the above
mentioned vector sum and vector difference. The input
signal phase characteristics is determined as follows:
- If PH-C > PH-L, the input signal has capacitive
characteristics.
- If PH-C < PH-L, the input signal has inductive
characteristics.