SX1276IMLTRT View Datasheet(PDF) - Semtech Corporation
Part Name
Description
Manufacturer
SX1276IMLTRT Datasheet PDF : 132 Pages
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SX1276/77/78/79
WIRELESS, SENSING & TIMING
DATASHEET
4. SX1276/77/78/79 Digital Electronics
4.1. The LoRaTM Modem
The LoRaTM modem uses spread spectrum modulation and forward error correction techniques to increase the range and
robustness of radio communication links compared to traditional FSK or OOK based modulation. Examples of the
performance improvement possible, for several possible settings, are summarised in the table below. Here the spreading
factor and error correction rate are design variables that allow the designer to optimise the trade-off between occupied
bandwidth, data rate, link budget improvement and immunity to interference.
Table 12 Example LoRaTM Modem Performances, 868MHz Band
Bandwidth
(kHz)
10.4
20.8
62.5
125
Spreading Factor
6
12
6
12
6
12
6
12
Coding rate
4/5
4/5
4/5
4/5
4/5
4/5
4/5
4/5
Nominal Rb
(bps)
782
24
1562
49
4688
146
9380
293
Sensitivity
indication
(dBm)
-131
-147
-128
-144
-121
-139
-118
-136
Frequency
Reference
TCXO
XTAL
Notes - for all bandwidths lower than 62.5 kHz, it is advised to use a TCXO as a frequency reference. This is required to
meet the frequency error tolerance specifications given in the Electrical Specification
- Higher spreading factors and longer transmission times impose more stringent constraints on the short term
frequency stability of the reference. Please get in touch with a Semtech representative to implement extremely low
sensitivity products.
For European operation the range of crystal tolerances acceptable for each sub-band (of the ERC 70-03) is given in the
specifications table. For US based operation a frequency hopping mode is available that automates both the LoRaTM
spread spectrum and frequency hopping spread spectrum processes.
Another important facet of the LoRaTM modem is its increased immunity to interference. The LoRaTM modem is capable of
co-channel GMSK rejection of up to 20 dB. This immunity to interference permits the simple coexistence of LoRaTM
modulated systems either in bands of heavy spectral usage or in hybrid communication networks that use LoRaTM to
extend range when legacy modulation schemes fail.
Rev. 4 - March 2015
©2015 Semtech Corporation
Page 25
www.semtech.com
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