Receivers bring diversity to low-power radio

Highly integrated RF receivers are specifically designed for low-cost antenna diversity applications in the unlicensed ISM and SRD frequency bands.

The MLX71120 and MLX71121 are two new members of a highly integrated RF receiver family.

Both automotive qualified ICs with dual RF inputs have been specifically designed for low-cost antenna diversity applications in the unlicensed ISM and SRD frequency bands.

The MLX71120 and MLX71121 RF receiver ICs are tailored for low-power and low-cost fixed-frequency applications.

They can address the European 863-870MHz SRD bands or the ISM bands at 902-928MHz in North America.

At the same time the new receiver chips are applicable for the lower frequency bands at 315MHz (eg in the USA) or at 433MHz (Europe and China).

Manufacturers of worldwide equipment for automotive remote keyless entry and tyre pressure monitoring systems as well as consumer and industrial system makers will benefit through the simplification of their production logistics and the indirect reduction in cost.

A simple crystal change adapts the system for different application frequencies.

One of the outstanding features of the two new receivers is their dual RF input.

This allows the user to very easily set up an antenna diversity scheme previously found only in high-end wireless systems.

This can significantly improve the reliability of the RF communications link by selecting the RF input with the best signal quality.

Another interesting feature of both receivers is the dual-band approach.

This allows switching the RF inputs between two applications, one at 433MHz and a second at 868MHz.

The MLX71120 receiver features a fully integrated FSK and ASK demodulator.

The IC provides the freedom to select an external intermediate frequency filter, operating at one of the two common frequencies 455kHz or 10.7MHz.

This way the receiver can be easily adapted to very narrowband or medium bandwidth applications.

The MLX71121 also features a fully internal demodulator, and it comes additionally with an on-chip IF filter offering a 230kHz bandwidth.

This means no external IF filter is required for the MLX71121.

The small 32-lead QFN package with a footprint of 5 x 5mm and the fact that no bulky external ceramic filter and discriminator components are necessary to make the MLX71120 and MLX71121 the optimum choice for systems requiring the smallest PCB footprint and the lowest circuit cost.

Both devices operate over a wide supply voltage range from 2.1 to 5.5V with a typical current consumption of 6.5 to 11mA.

In standby mode the current draw is below 50nA.

The receiver input sensitivity is as low as -113dBm for ASK and -112dBm (MLX71120) and -107dBm (MLX71121) for FSK signals, respectively.

The receivers combine flexibility with high levels of circuit complexity.

They dramatically reduce system costs thanks to the internal IF filter and FM/FSK demodulator.

The receivers' AFC feature can tolerate frequency uncertainties of the input signal.

Dr Andreas Laute, Manager of Melexis' Business Unit Wireless Communication, states: "With the introduction of these new devices of our highly integrated RF receiver family, we provide tools for our customers to ease the development of state-of-the-art receiver systems".

"The MLX71120/71121 with their antenna diversity feature will be a revolution in the low-cost RF receiver segment".

The extended operating temperature range of -40 to +125C makes the parts ideal for automotive applications such as remote keyless entry, tyre pressure monitoring or car alarm systems.

Other typical applications for the receivers include security systems, home automation, garage door openers, wireless door bells, baby monitors and wireless headsets.

The MLX71120 and MLX71121 are Eur 1.16 each in quantities of 100,000.

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