Integration Manual

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6 CHIP RADIO
The chip radio used is the SX1280 of SEMTECH company. The SX1280 are half-duplex transceivers capable
of low power operation in the worldwide 2.4 GHz ISM band. The radio features a high efficiency
transmitter and a high linearity receive chain that are both accessed via a common antenna port pin.
Frequency conversion between RF and baseband (low-IF) is governed by a digital PLL that is referenced to a
52 MHz crystal. Both transmit and receive chains are interfaced by data converters to the ensuing digital.
The analog front end features a single antenna port connection to an integrated matching circuit that
permits half- duplex operation of the radio without external RF switching.
Transceiver Block Diagram:
The modem uses spread spectrum modulation and Forward Error Correction (FEC) techniques to increase
the range and robustness of radio communication links.
In this modulation the spreading of the spectrum is achieved by generating a chirp signal that
continuously varies in frequency. An advantage of this method is that timing and frequency offsets
between transmitter and receiver are equivalent, greatly reducing the complexity of the receiver design.
The frequency bandwidth of this chirp is equivalent to the spectral bandwidth of the signal.
The wanted data signal is chipped at a higher data rate and modulated onto the chirp signal.
The relationship between the wanted data bit rate, symbol rate and chip rate for the modulation can
be expressed as follows:
We can define the modulation bit rate, Rb, as: Rb = SF * 1 / [2
SF
/BW] bits/sec
Where:
Rb = Raw Data Rates
SF = spreading factor (7..12)
BW = modulation bandwidth (Hz)
Below principal parameters configured in the radio chip SX1280:
- Type of modulation: spread spectrum modulation
- Raw Data Rates: 44 kb/s (SF7)
- Bandwidth: 812 kHz