New-Tech Europe Magazine | July 2017

IoT Special Edition

Acceptance Range (CFAR) is not dependant on the AFC setting. The AFC simply enables the carrier recovery to converge to a given value after each and every packet. This allows the preamble length to be reduced, if the application can tolerate losing a few packets at the start. Fig. 4 illustrates the packet error rate (PER) against CFAR. The example here is given for a DR of 55.6kbps with a ±50kHz FSK deviation. As can be seen, there is a trade-off between the preamble length (which is the part of the packet during which the carrier recovery tries to converge) and the PER. Conclusion Undoubtedly, as the demand for IoT devices grows substantially, consumers and users will put manufacturers of these devices under price pressure, requiring them to reduce costs with each generation of product. This will inevitably lead to greater use of low- cost crystals with wider frequency tolerances in the sensor nodes to achieve this goal. As designers search for elegant solutions to this cost / performance trade-off, the MLX73290-M RF transceiver with its large carrier frequency acceptance range will become a popular solution for IoT data collectors as well as bidirectional network nodes.

Fig. 4: MLX73290-M CFAR (Δf) at different preamble lengths

modulation schemes are supported. 2 RF power detectors provide augmentation of radiated power performance during transmission. An energy harvesting interface allows battery-less power supply by using a solar cell in combination with a super capacitor. This accentuates the transceiver’s value in remote locations where power lines are impractical. Evaluation boards and software tools are also available. The MLX73290-M is supplied in 5mm x 5mm 32-lead QFN package. It has an operational temperature range of

-40°C to 105°C and operates from a supply voltage in the range 2.1 to 3.6V DC. The device includes a PLL synthesizer with 60Hz resolution, a 256byte FIFO that can be split 128/128 for RX/TX use and a total of 4 programmable GPIO ports for interfacing with other system elements. With its carrier recovery feature the MLX73290-M transceiver is able to tolerate a carrier frequency deviation of up to twice the raw data rate (DR) usually expressed as ±2 x DR. The Carrier Frequency

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