RFM31 Datasheet, PDF (10/137 Pages) –

RFM31
2. Functional Description
The RFM31 is ISM wireless receiver module with continuous frequency tuning over the complete 240–960 MHz band.
The wide operating voltage range of 1.8–3.6 V and low current consumption makes the RFM31 and ideal solution for
battery powered applications.
The RFM31 uses a single-conversion, image-reject mixer to downconvert the 2-level FSK/GFSK/OOK modulated
receive signal to a low IF frequency. Following a programmable gain amplifier (PGA) the signal is converted to the
digital domain by a high performance △∑ ADC allowing filtering, demodulation, slicing, error correction, and packet
handling to be performed in the built-in DSP increasing the receiver‘s performance and flexibility versus analog
based architectures. The demodulated signal is then output to the system MCU through a programmable GPIO or via
the standard SPI bus by reading the 64-byte RX FIFO.
A high precision local oscillator (LO) is generated by an integrated VCO and △∑ Fractional-N PLL synthesizer. The
synthesizer is designed to support configurable data rates, output frequency, frequency deviation, and Gaussian
filtering at any frequency between 240–960 MHz.
The RFM31 is designed to work with a microcontroller to create a very low cost system. Voltage regulators are
integrated on-chip which allow for a wide range of operating supply voltage conditions from +1.8 to +3.6 V. A
standard 4-pin SPI bus is used to communicate with the microcontroller. Three configurable general purpose I/Os
are available for use to tailor towards the needs of the system. A more complete list of the available GPIO functions
is shown in "8. Auxiliary Functions" but just to name a few, microcontroller clock output, Antenna Diversity, Antenna
SwitchPOR, and specifc interrupts. The RFM31application shown in Figure 1.
Figure 1. RFM31 Application Example
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