LLCC68 datasheet(35/111 Pages) SEMTECH

35 / 111 page

LLCC68

Data Sheet

Rev. 1.1

DS.LLCC68.W.APP

Dec 2024

35 of 111

Semtech

LLCC68

www.semtech.com

The capability to receive signals with negative SNR increases the sensitivity, link budget and range of the LoRa receiver.

A higher spreading factor provides better receiver sensitivity at the expense of longer transmission times (time-on-air).

With a knowledge of the key parameters that can be selected by the user, the LoRa symbol rate is defined as:

where BW is the programmed bandwidth and SF is the spreading factor. The transmitted signal is a constant envelope signal.

Equivalently, one chip is sent per second per Hz of bandwidth.

6.1.1.2 Bandwidth

An increase in signal bandwidth permits the use of a higher effective data rate, thus reducing transmission time at the expense of reduced

sensitivity improvement.

The LoRa modem operates at a programmable bandwidth (BW_L) around a programmable central frequency fRF

Figure 6-1: LoRa® Signal Bandwidth

An increase in LoRa signal bandwidth (BW_L) permits the use of a higher effective data rate, thus reducing transmission time at the expense

of reduced sensitivity improvement. There are regulatory constraints in most countries on the permissible occupied bandwidth. The LoRa

modem bandwidth always refers to the double side band (DSB). The range of LoRa signal bandwidths available is given in the table below:

For BW_L up to 250kHz, the receiver performs a double conversion. A first down conversion to low- IF is performed inside the RF chain, a

second conversion to baseband is performed digitally inside the baseband modem. When the 500kHz bandwidth is used, a single

down-conversion to zero-IF is performed in the RF part.

Table 6-1: Range of Spreading Factors (SF)

Spreading Factor (SF)1

1. Not all SF are available for any bandwidth with the LLCC68

2^SF (Chips / Symbol)

128

256

512

1024

2048

Typical LoRa Demodulator SNR [dB]

-2.5

-5

-7.5

-10

-12.5

-15

-17.5

Table 6-2: Signal Bandwidth Setting in LoRa® Mode

Signal Bandwidth

BW_L [kHz] 0

1250

250 1

1. For RF frequencies below 400MHz, there is a scaling

between the frequency and supported BW, some BW

may not be available below 400MHz

500 1

2SF

---------

fRF

fRF BWL

------------

fRF BWL

------------

–

BW_L

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