ATA5425-PLSW datasheet(17/100 Pages) ATMEL

17 / 100 page

4841D–WIRE–10/07

ATA5423/ATA5425/ATA5428/ATA5429

3.7

In-band Disturbers, Data Filter, Quasi-peak Detector, Data Slicer

If a disturbing signal falls into the received band or a blocker is not continuous wave, the perfor-

mance of a receiver strongly depends on the circuits after the IF filter. The demodulator, data

filter and data slicer are important, in that case.

The data filter of the ATA5423/ATA5425/ATA5428/ATA5429 implies a quasi-peak detector. This

results in a good suppression of the above mentioned disturbers and exhibits a good carrier to

Gaussian noise performance. The required useful signal to disturbing signal ratio to be received

with a BER of 10

–3 is less than 12 dB in ASK mode and less than 3 dB (BR_Range_0 to

BR_Range_2)/6 dB (BR_Range_3) in FSK mode. Due to the many different waveforms possible

these numbers are measured for signal as well as for disturbers with peak amplitude values.

Note that these values are worst case values and are valid for any type of modulation and mod-

ulating frequency of the disturbing signal as well as the receiving signal. For many combinations,

lower carrier to disturbing signal ratios are needed.

3.8

DEM_OUT Output

The internal raw output signal of the demodulator Demod_Out is available at pin DEM_OUT.

DEM_OUT is an open drain output and must be connected to a pull-up resistor if it is used (typi-

cally 100 k

Ω) otherwise no signal is present at that pin.

3.9

RSSI Output

The output voltage of the pin RSSI is an analog voltage, proportional to the input power level.

Using the RSSI output signal, the signal strength of different transmitters can be distinguished.

The usable dynamic range of the RSSI amplifier is 70 dB, the input power range P(RF

IN) is

–115 dBm to –45 dBm and the gain is 8 mV/dB. Figure 3-6 shows the RSSI characteristic of a

typical device at 433.92 MHz with VS1 = VS2 = 2.4 to 3.6 V and T

amb = –40°C to +85°C with a

matched input according to Table 3-2 on page 12 and Figure 3-1 on page 11. At 915 MHz about

3.3 dB and at 868.3 MHz about 2.7 dB more signal level, at 345 MHz about 0.8 dB and at

315 MHz about 1 dB less signal level is needed for the same RSSI results.

Figure 3-6.

Typical RSSI Characteristic versus Temperature and Supply Voltage

400

500

600

700

800

900

1000

1100

-80

-70

-60

-50

-120

-110

-100

-90

PRF_IN (dBm)

-40

max.

min.

typ.

ATA5425-PLSW Datasheet(PDF) 17 Page - ATMEL Corporation

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