HFA3863 データシートの表示（PDF） - Intersil
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HFA3863 Datasheet PDF : 39 Pages
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HFA3863
120
RSSI
100
80
60
40
20
0
-100
-80
-60
-40
-20
0
SIGNAL LEVEL IN dBm
FIGURE 16. RSSI vs SIGNAL LEVEL
Signal Quality Estimate
A signal quality measure is available on CR51 for use by the
MAC. This measure is the SNR in the carrier tracking loop
and can be used to determine when the demodulator is
working near to the noise floor and likely to make errors.
Figure 17 shows the performance of the SQ measure versus
signal to noise level.
100
90
80
70
60
50
40
30
20
10
0
-10
PER
MEAN
STDDEV
-5
0
5
10
15
20
25
SNR IN THE SPREAD BANDWIDTH AT 1Mbps
FIGURE 17. SIGNAL QUALITY MEASURE AND PER vs SNR
ED Threshold
The performance of the ED threshold is shown in Figure 18.
Setting this threshold will effect CCA only. Using ED as part
of the CCA measure will allow deferral to large signals even
if they are not correlated to the desired spread signals.
ED can be read from CR61 bit 4. Using ED and RSSI can
assist the MAC in determining the presence of non
correlating signals such as frequency hoppers or microwave
ovens. For example, the MAC can elect to try to transmit
over microwave oven interference but not count the results in
rate shifting algorithms.
40
30
20
10
0
-10 0
STARTS MISSING
MISSING
10
20
30
40
SNR IN SPREAD BANDWIDTH
FIGURE 18. ED THRESHOLD vs SNR IN dB AT 1Mbps
A Default Register Configuration
The registers in the HFA3863 are addressed with 7-bit numbers
where the lower 1 bit of an 8-bit hexadecimal address is left as
unused. This results in the addresses being in increments of 2
as shown in the table below. Table 9 shows the register values
for a default 802.11 configuration with various rate
configurations. The data is transmitted as either DBPSK,
DQPSK, or CCK depending on the configuration chosen. It is
recommended that you start with the simplest configuration
(DBPSK) for initial test and verification of the device and/or the
radio design. The user can later modify the CR contents to
reflect the system and the required performance of each
specific application.
4-21
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