XE1202A Просмотр технического описания (PDF) - Semtech Corporation

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XE1202A

433 MHz / 868 MHz / 915 MHz Low-Power, Integrated UHF Transceiver

Semtech Corporation 

tbit

datain

no filtering

IN freq_synth

XE1202A TrueRF™

staircase filtering

trise

IN freq_synth

Figure 6: Modulation without and with pre-filtering

The characteristic of the smoothing filter is the ratio trise/tbit. The value of this ratio is programmable with the register

“RTParam_Stair”, as illustrated in Table 9:

FSParam_Stair

0

1

trise/tbit

10 %

20 %

Table 9: Smoothing filter

4.1.6 Pattern recognition

XE1202A TrueRF™ includes a pattern recognition function. When “ADParam_Pattern” (see the Configuration

register section below) is set to “1” pattern recognition is enabled, providing that the bit synchronizer is also

enabled. With the pattern recognition function enabled, the demodulated data is compared with a pattern stored in

the “Pattern” register. The length of this pattern can be 8, 16, 24, or 32 bits, as defined by “ADParam_Psize”. When

comparing the streams 0, 1, 2, or 3 errors, as defined by “ADParam_Psize” can be allowed to detect a match. The

PATTERN output is driven by the output of this comparator. It is “high” when a match is detected, otherwise “low”.

When the feature is disabled, the PATTERN output is set to “low”.

4.1.7 Frequency synthesizer

The exact frequency step of the frequency synthesizer can be obtained from the following equation:

FSTEP = FXTAL / 77 824.

As an example, if FXTAL is exactly 39 MHz, FSTEP = 501.13 Hz.

© Semtech 2006

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