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PDF SX061 Data sheet ( Hoja de datos )
| Número de pieza | SX061 | |
| Descripción | 1 Mbit/s DQPSK/DBPSK Digital Demodulator | |
| Fabricantes | AMI | |
| Logotipo |  |
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WavePlex ™
SX061
1 Mbit/s DQPSK/DBPSK
Digital Demodulator
Table of Contents
User’s Manual
General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Functional Description of the SX061 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Description of Individual Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
The PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
The AD Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
The AGC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
The AGC in Slip Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
The NCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
The I&D Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
The Demodulating DSP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Detecting Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Carrier Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Generating RSSI1 and RSSI2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Triggering the Demodulating DSP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Designing a Link Using the SX061 and the SX043/42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Specify Link Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2. Setup the SX043 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3. Setup the Internal Clocks on the SX061 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4. Setup the AGC Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5. Setup the Internal IF Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Setup the RSSI Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7. Synchronizing the Receiver: Slip Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8. Synchronizing the Receiver: Track Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9. Setup the Carrier Tracking Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10. Setup the Data Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
11. Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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1 page  
WavePlex ™
SX061
1 Mbit/s DQPSK/DBPSK
Digital Demodulator
User’s Manual
A simple RC section can obtain the analog RSSI value
from the Pulse Width Modulator.
The SX061 also generates an AGC output. This AGC
signal is used to control the gain of the amplifier in the
Radio Unit. This guarantees an optimal quantization of
the incoming signal.
The internal registers of the SX061 are programmed by a
serial interface, which is controlled by the SX043.
The SX061 has a complete PLL inside for the generation
of the internal clock signals. Using a reference crystal
frequency of 2 MHz an internal clock signal from 1.56
MHz up to 100 MHz can be generated.
Figure 3: SX061 - SX043 Interconnections
5
5 Page 
WavePlex ™
SX061
1 Mbit/s DQPSK/DBPSK
Digital Demodulator
User’s Manual
The AGC
The AD converter works optimally when the quantization
error is minimized. The AGC makes sure that the
quantization levels of the signal are chosen optimally. The
signal is assumed to be sine shaped, and that the DC
level of the signal is exactly between the two quantization
levels.
In this case the input signal is always quantized the same
number of times as a +1 as is it quantized as –1. When
the input signal is larger the number of times that the
signal is quantized as ‘0’ is smaller than when the signal
is small. The ratio between the number of +/- 1 samples
and ‘0’ samples should be about 1/3.
The AGC pin becomes high when a ‘0’ is sampled and
low when a ‘1’ or ‘-1’ is sampled. This is a measure for the
above mentioned ratio. Therefore the AGC output should
be compared to 1/3 of VDD. When the difference between
the AGC output and the 1/3 VDD is integrated by a pure
integrator, a good signal for the AGC control is obtained
for almost any amplifying device.
The time constant of this integrator controls the speed of
the AGC loop.
Therefore a circuit to use the AGC output of the SX061,
which can control almost any AGC input of an amplifying
circuit, is suggested in Figure 7.
The AGC loop has to be slower than the dither rate.
Otherwise it would suppress the tau dither information.
However it should be faster than the fastest variations in
amplitude that the radio has to expect.
The AGC in Slip Mode
When the signal is uncorrelated (in slip mode) a
bandpass filter will probably make the input signal very
small. This will set the AGC output to its maximum value.
When a correlation peak occurs the window comparator
will act as a hard limiter. This will not influence the quality
of the quantized signal severely. However, during the time
that the AGC loop is not settled the performance of the
SX061 is not optimal. Therefore the time needed to bring
the AGC to its correct operation point should not be more
than a small part of the data message (but larger than the
dither rate). The speed of the AGC loop is largely
determined by the external time constants.
Note: For proper operation of the AGC the AGC_comp_test bit of the
COMP_SEL register has to be set to ‘0’.
Figure 7:
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11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet SX061.PDF ] | |
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