Panasonic KX-F900 Service Manual page 177

KX-F900
(5) TX Power Circuit ( ): Portable Handset
After being multiplied by 2 inside IC301 (IC401) to make it a 900 MHz band frequency, the transmission signal
is amplified by Q301 and Q302 (Q401 and Q402) and frequency elements outside of the transmission fre-
quency are attenuated b_t dielectric filter F301 (F401). The signal then passes through a transmission-recep-
tion matching circuit and supplied to the antenna terminal.
Circuit Diagram
R302
cO
CD
o_E--
8:Z-
R304[-_'
/
)Q302
IC301
IN
C303 F301 C354
• ANT
(6) Second Mixer, Detector, Carrier Sense Circuit ( ): Portable Handset
The 10.7 MHz IF signal from Q305 (Q405) passes through pin 16 of IC302 (IC402) and is input to the second
mixer built into the IC. The reference oscillator frequency from IC301 (IC401) is used as the second local sig-
nal. After being converted into a 450 kHz second IF by the second mixer, the signal is wave detected and out-
put to pin 9 as a low-frequency signal. This signal is output as the AF output signal and, at the same time,
used for e(ectric field determination. The FM noise is filtered by a 10 kHz BPF comprising pins 10 and 11 and
then amplified. Then it is rectified by D301 (D401) and D302 (D402), and input to the switching block consist-
ing of pins 12 through 14.
Circuit Diagram
SQL<
AF<
i
D302
R331 C340
Carrier Sense
, 1st IF
R337
-177-
14 Pin
Enable to Electric Field "L"
Disable to Electric Field "H"
o
o
u
-I
O
"0
m
33
0
z