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== Overview == [[SDR]] Semtech acquired the LoRa wireless technology through its acquisition of Cycleo SAS of Grenoble, France for $5M in 2012. LoRa’s modulation format is best described as a “frequency modulated (FM) chirp.” The core IP that enables LoRa is the ability to generate a stable chirp using a frac-N phase lock loop (PLL). When processing a LoRa message, additional processing gain is achieved due to the modem’s ability to filter on the constant ramp chirp signal. This is how high sensitivity is achieved. In order to achieve “lock” to the LoRa signal, a long “constant chirp” preamble is transmitted: [[文件:LoRa-Preamble-1.jpg]] Once a LoRa modem has “locked” on to the preamble signal, the end of the preamble is signaled by the “reverse chirp” seen in Figure 1. Then the data transmission begins, which has a series of “symbols” that function much like M-ARY FSK symbols, but instead happen on a chirp. See Figure 2 [[文件:LoRa-modulation-1.jpg]] <br>
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