XE1203 Просмотр технического описания (PDF) - Unspecified

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производитель

XE1203

433MHz / 868MHz / 915MHz Low-power, integrated UHF transceiver

Unspecified 

Data Sheet

XE1203

4.1.6 Barker decoder

The Barker decoder is an alternative to the bit synchronizer for a fixed data rate of 1154 bps. The barker block is

selected in receiver mode when RTParam_Barker is high. In transmission, the information data at a bit rate of 1154

bps is spread using an 11 bits barker code. The result is a bit stream at 12.7 Kilo chips per second (Kcps), which is

applied to the frequency synthesizer. At the receiver part, the signal is demodulated using the FSK demodulator (at

12.7 Kcps) and fed to the Barker decoder that provides a information data stream (1154 bps) and a synchronized

clock to sample it.

The following figure describes the coding/decoding process.

information data

1154 bps

BARKER ENCODER

11 bit barker code

encoded information

12.7 Kcps

chip rate = 12.7 Kcps

FSK

MODULATOR

FSK DEMODULATOR

Demodulated chips with some

residual jitter.

chip rate = 12.7 Kcps

BARKER DECODER

11 bit barker code

data

DCLK

data out (information recovered)

dclk = 1.145 KHz

data rate = 1.145 Kbps

Figure 3. Data encoding decoding channel.

In reception mode, the chip provides a clock (DCLK) to a microcontroller. The data can be sampled at the rising

edge of the clock. When using the barker coding decoding process, DCLK is used to detect the sync acquisition. If

there is no valid data, DCLK remains high. The first falling edge of the clock means that the sync acquisition phase

is reached and the data has became available. The next figure shows the data exchange during the reception

mode.

11

D0308-214

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