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KX-F910BX
CIRCUIT OPERATION
(6) Electric Field Detect in Circuit
The electric field detection circuit comprises a noise amplifier and a noise detection circuit. If the output from
the circuit is high level, the information "no signal detected" is sent to MPU IC501. If the output is low level,
the information "signal detected" is sent to MPU IC501.
The AF output from the RF unit is amplified by Q503 and, at pins 55 and 54 of IC502, noise signal only are
extracted by an approximately 10KHz band-pass Filter. Wave detection is performed by the noise detection circuit
built into IC502, and the result is output as logical output to pin 48 of IC502.
(1) PLL Circuit
IC201 includes two PLL circuits for transmission frequency and reception local frequency.
The frequency in the band of 900 MHz supplied from TX VCO and RX VCO, and Ref. OSC frequency (12.8
MHz) are divided into 12.5 kHz frequency controlled by the CPU. The phases of the frequency from TX and RX
and the reference frequency are compared each other, the control voltage is supplied to the VCO circuit from
pins 7 and 18 so that the desired TX and RX frequencies are provided. The VCO control signal (TX, RX fre-
quency setting) of the PLL circuit is supplied to CPS pin 15, SI pin 16 and RST pin 17 from the CPU circuit.
Also, the locked oscillation frequency of the VCO circuit is supplied to the CPU from pin 14 at "L".
13-5. CIRCUIT OPERATION OF RF UNIT
Circuit Diagram
TX VCO
from VCO201
C208
R209
X201
VC201
Ref. OSC. 12.8MHz
1
2
3
4
5
6
7
8
9
10
11
12
NC
TXO
Vcc
TXB
TXE
GND
PD1
Vcc
XIN
XOUT
XB
GND
Frequency TX
Demultiplication
Phase Comparator
OSC+1/2
Divider
Frequency Ref
Demultiplication
Frequency RX
Demultiplication
Phase Comparator
MIXR 24
MIXIN 23
Vcc 22
RXB 21
RXE 20
GND 19
PD2 18
RST 17
SI 16
CPS 15
LD 14
MIXO 13
C240
C241
R222
C243
RX VCO
from VCO202
Control voltage
to RX VCO
LPF (RX)
CPU circuit
C242
IC201
to TX VCO
LPF (TX)
R202 R203
C236
C237
R223
C238
C239
R231
R225
C202
C203
R204
C204
Control
voltage
C215
C216
C214
AMP
IC502
DET 2
NOISE
SQ 2
55
54
52
48
R517
C509
R519
R518
49
R520
IC501
(68pin)
C507
C508
R513
C504
R514
R515
C505
Q503
R516
VR
501
C502
R512
C503
R511
IC502
(1pin)
AF
C501
Circuit Diagram
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