Data Demodulation and Crystal Selection for the
AT86RF211S
1. Introduction
This document gives an overview of the receiver chain of the AT86RF211S and its
associated embedded features:
• Discriminator: Demodulation of the RF signal (principle, measurement/tuning of
output voltage)
Data slicer:From analog to digital world (different modes of functioning, how to set
up the data slicer threshold)
It also emphasizes the new possibilities of the AT86RF211S
Selection of lower cost crystal
Data rate up to 128 kbps
Frequency deviation wider than ±100 kHz
2. From Analog to Digital
2.1 Demodulation
2.1.1 Principle
The FSK modulation used by the AT86RF211S consists in coding each bit as follows:
“0”: transmission of an RF signal at a frequency F0
“1”: transmission of an RF signal at a frequency F1
The channel frequency (or carrier) is the middle frequency Fc = (F0 + F1)/2
F1 - Fc = Fc - F0 is called the frequency deviation
The receiver therefore has the overall task to:
Down-convert the signal at lower frequencies (for filtering purposes): 10.7 MHz
and 455 kHz
Convert the frequencies into voltages (= discriminator)
Make a decision to separate “0” from “1” levels (= data slicer)
AT86RF211S
FSK
Transceiver for
ISM Radio
Applications
Application Note
Rev. 5418A–WIRE–04/05