JN516X Datasheet, PDF (29/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

8.2 Modem
The modem performs all the necessary modulation and spreading functions required for digital transmission and
reception of data at 250kbps in the 2450MHz radio frequency band in compliance with the IEEE802.15.4 standard.
Gain
IF Signal
AGC
RX
Demodulation
Symbol
Detection
(Despreading)
RX Data
Interface
VCO
Sigma-Delta
Modulator
TX
Modulation
Spreading
TX Data
Interface
Figure 17: Modem Architecture
Features provided to support network channel selection algorithms include Energy Detection (ED), Link Quality
Indication (LQI) and fully programmable Clear Channel Assessment (CCA).
The Modem provides a digital Receive Signal Strength Indication (RSSI) that facilitates the implementation of the
IEEE 802.15.4 ED function and LQI function.
The ED and LQI are both related to receiver power in the same way, as shown in Figure 18. LQI is associated with a
received packet, whereas ED is an indication of signal power on air at a particular moment.
The CCA capability of the Modem supports all modes of operation defined in the IEEE 802.15.4 standard, namely
Energy above ED threshold, Carrier Sense and Carrier Sense and/or energy above ED threshold.
Figure 18: Energy Detect Value vs Receive Power Level
© NXP Laboratories UK 2013
JN-DS-JN516x v1.1 Production
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