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Circuit Descriptions, Abbreviation List, and IC Data Sheets
both the transmitter and receiver side. There are frequency
executions available in different frequency bands:
•
433 MHz (some EU countries).
•
864 MHz (EU).
•
914 MHz (US).
In each particular frequency band, there is a choice between
four different channels or frequencies.
9.7.2
System Considerations
The Wireless system uses a very high performance audio
processing that allows up to 100 dB dynamic range to be
transmitted over a classic analogue link, through the
compressing effect at the transmitter (reducing the dynamic
range by a factor of 2 in dB) and the expanding effect in the
receiver (increasing the dynamic range by a factor of 2 in dB).
9.7.3
Transmitter
Block Diagram
R
TRANSMITTER
- COMPANDER -
7113
1101
F140
NJM4565M
R
L
1
2
3
2
V
F141
L
R
6
3
5
4
11V_S
V
5
7112
SA572D
TO TV
6
CONNECTION
5
I2C-CLOCK
7
TO1103
11
B14B
8
I2C-DATA
7117
LD1117DT
F124
3
2
+8V
F126
7119
+5V
6105, 7118
POWER DOWN
PD
DETECTOR
Audio Compander
The audio compressor uses a SA572 (7112), which is intended
for high-end applications. It is used together with a low noise
OpAmp (7113). There is no audio input filtering ahead of the
compressor. Therefore, it can only be used when the source is
having no frequency components above 20 kHz, otherwise the
compander's linearity will be at risk. This is realised with a
digital filter on the SSP.
Graphically the operation of a "compressing and expanding"
(=companding) system can be understood from following
figure:
1
2
V
RMS
COMPRESSION
IN
INPUT TO ∆G
3.0V
AND RECT
547.6MV
400MV
100MV
10MV
1MV
100µV
10µV
Figure 9-12 Compressing/Expanding graphics
- STEREO ENCODER -
MULTIPLEXED
7111
2165, 3160, 3190
74HC4053HD
F145
1
PRE-EMPHASIS
5
4
2166, 3161, 3191
F144
3
7
PRE-EMPHASIS
V
9
6
7
∆G
9
SUBC
7110
46,875kHz
74HC4060
OSCILLATOR
F131
3
14
RECTI-
256
13
FIER
F130
13
PILOT
23,4375kHz
512
10
1106
12
12MHz
ENABLE
11
(Low)
VPIL
PD
Figure 9-11 Block diagram transmitter
2
REL LEVEL
ABS LEVEL
EXPANDOR
dB
dBM
OUT
+29.54
+11.76
+14.77
–3.00
+12.0
–5.78
0.0
–17.78
–20
–37.78
–40
–57.78
–60
–77.78
–80
–97.78
CL36532008_073.eps
130503
In addition, the system has the possibility to maintain the high
S/N up to low RX field strengths by applying sliding stereo (this
means reducing the stereo effect at low signal field strengths).
Pre-emphasis (at TX) / de-emphasis (at RX) technique is
with15 us time constant.
Since the signal processing is analogue, there is a low latency
in the system of < 15 us between input TX and output RX.
The receiver part has a power save mode that will be initiated
automatically when no signal to reduce power consumption.
The system uses normal FM modulation/demodulation and
also uses the Zenith stereo system. However, the frequencies
used are different in this respect: the sub carrier frequency= 3
* 15.625 kHz = 46.875 kHz (chosen because interference zero-
beats with the TV line freq). Consequently, the pilot frequency
is 23.4375 kHz (half of sub carrier).
The transmitter amplifier has an output power of 10 mW and
drives it into an internal printed antenna (the 433 MHz version
uses an external antenna).
- PLL -
7116-B
NJM4565M
7116-A
MODULATION
3177
F149
LEVEL ADJ.
6
F147
2
1
MPX
7
3
5
V
3174
3179
6102
LIMITER
LOW-PASS
BB151
(VARICAP)
7102
SDA
SCL
+6V
3105
VERSION
SELECTION
433MHz
or
3106
864MHz
3140
L
1K0
3141
R
1K0
3158
10K
2159
3156
22n
3K3
2160
3157
22n
3K3
3159
10K
Basically, the circuit comes down to following simple circuit:
EM6E AB
7104
F113
+8b
7103
BFR92A
7105
X2
LOCAL
FREQUENCY
FILTER
OSCILLATOR
MULTIPLIER
OSC
7101
TSA5060A
VOSC
16
(ENABLE)
14
7
X2 (ENABLE)
5
9
F110
6
8
SYNTHESIZER
VFIL
2
(ENABLE)
1105
4MHz
11
ADC
VPIL
2143
F140
3146
3144
1u
47K
15K
2145
4n7
2144
F141
3147
3145
47K
15K
1u
+8V
2146
4n7
F142
COMPANDER
3154
1K0
7112
SA572D
16
VCC
2163
7 GIA
GOA
5
G
50V 2u2
2164
9
GIB
GOB
11
2149
50V
2u2
2 RCA
THTA
6
10u
16V
2150
3155
14 RCB
THTB
10
BUFFER
2147
10u 16V
1K0
4 ACA
TRTA
1
F143
1u
2148
12 ACB
TRTB
15
2161
1u
3 RIA
RECT
50V
2u2
2162
13 RIB
50V 2u2
GND
8
Figure 9-13 Companding circuit
9.
EN 157
7106
BFG520
5112
F114
OUTPUT
CL36532008_069.eps
220403
3150
3152
18K
18K
2151
22p
2155
4
F145
2
270p
1
7113-A
8
3
NJM4565M
+8V
+8V
2176
470p
5
8
F144
7
3168
6
4 7113-B
2K2
NJM4565M
2152
22p
3151
3153
18K
18K
CL36532008_074.eps
130503
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