Rf Signal Path - Tait TM8100 mobiles Service Manual

11.4

RF Signal Path

Introduction
Figure 11.20 Measurement points for diagnosing faults in the RF signal path
SIGNAL TYPES
RF
ANALOG
TEST
CAPACITOR
W
50 TEST
LEAD TO
TEST SET
RECEIVER
TEST
CAPACITOR
W
50 TEST
LEAD TO
TEST SET
RF CON-
NECTOR
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
The RF signal path extends from the output of the frequency synthesizer to
the LPF. This section of circuitry will require investigation either following
certain checks in "Transmitter RF Power"
"Biasing of PA Driver and PAs"
into ten tasks grouped as follows:
Task 26 to Task 30: initial RF signal path
■
Task 31 and Task
■
Task 33 and Task
■
Task 35: LPF
■
The initial signal path includes the exciter and PA driver. The directional
coupler, PIN switch, and LPF make up the final signal path.
The measurement points for diagnosing faults in the signal path are
summarized in Figure
PAs
L314
GATES OF
Q309, Q310
DIREC-
TIONAL
COUPLER
PIN
SWITCH
LPF
reveal no fault. The procedure is divided
32: directional coupler
34: PIN switch
11.20.
STAGE 3
EXCITER
OUTPUT
DRIVER
PA DRIVER
OUTPUT AT
DRAIN OF Q306
Transmitter Fault Finding (>25W)
or if the biasing checks of
SYNTHESIZER
OUTPUT
SYN TX LO
EXCITER
C307
C3500
(C300 for
K5 band)
STAGE 2 STAGE 1
OUTPUT OUTPUT
AT C3509 AT C3505
QUENCY
SYNTHE-
SIZER
FRE-
315