JN5148 NXP Semiconductors, JN5148 Datasheet - Page 29

• Manufacturer Part Number: JN5148
• Description: The JN5148 is an ultra low power, high performance MCU combined with an IEEE802
• Manufacturer: NXP Semiconductors

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. It
also provides a high data rate modes at 500 and 667kbps.
RX
Gain
Symbol
RX Data
AGC
Demodulation
Detection
Interface
(Despreading)
IF Signal
TX
VCO
Modulation
Spreading
TX Data
Interface
Sigma-Delta
Modulator
Figure 18 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 Fig19. 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 19 Energy Detect Value vs Receive Power Level
© NXP Laboratories UK 2011
JN-DS-JN5148-001 1v7
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