
December 2000 TOKO, Inc.
Page 13
TK83361M
APPLICATIONS INFORMATION (CONT.)
Figure 9. Active BPF
Eq. (3) is formularized, where G
0
is the gain at center
frequency f
0
, and 3dB bandwidth Q=f
0
/BW.
Figure 10. Frequency Response
Figure 11. Squelch Output versus Squelch Input
i) Pin 13 Output
ii) Pin 14 Output
Figure 12: Application Example Block Digram
12-7. Attentions to Layout Design
As this product is considered for stable operation, the mixer
block and the other block that includes IF stage, OP amp
and squelch are independent from each other. However in
order to realize stable operation, please pay attention to the
following, because of high frequency operation.
(1) Bypass Capacitor
A bypass capacitor must be connected with minimum
distance between the V
CC
pin and the GND pin.
(2) V
/GND Pattern
In order to make low impedance V
CC
/GND lines, please
keep the pattern as wide as possible.
(3) Pattern near Demodulator
Pattern layout around the phase shifter for demodulator:
please keep as short as possible.
12-5. Squelch Section
The output, which is controlled in accordance with the noise
level from the rectifier, is injected into the squelch input pin.
There is about 45mV of hysteresis at the Squelch Input to
prevent jitter.
+
-
~
R3
VOUT
C
C
R1
R2
VIN
VCC = 4.0V
Vin = 50mV
R1 = 18k
R2 = 750
R3 = 390k
C = 0.001
μ
F
20
15
10
5
0
1k 10k 100k
fin, FILTER AMPLIFIER INPUT FREQUENCY (Hz)
G
R1 = R3
2G0
Q
π
f0C
R1R3
4Q2R1-R3
S
VTH
S
VTL
VSQ(V)
VTH
VTL
VSQ(V)
LPF
N
R
X
N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
RF
INPUT
SCAN CONTROL
to PLL
V
OSC
MIXER
L
A
10pF
QUAD DET
VCC
SQUELCH
GND
FILTER
AMP
N
B
B
P
S
0.1
μ
F
0.1
μ
F
AF
OUTPUT
MUTE
V
indicates the Hi threshold voltage, V
TL
indicates the Lo
threshold voltage in Fig. 11.
12-6. Application Example