Easing the challenge of RF design

The very mention of RF design is usually enough to scare all but the most confident designer. But it needn’t be a nightmare if the engineer follows the guidelines described in this white paper.

RF design is not trivial. However, Nordic Semiconductor has worked hard to ensure it’s no longer solely the domain of the RF expert. Performance optimized transceivers, and the availability of development kits and reference layouts, makes it possible for a competent electronics design engineer to incorporate wireless hardware into their latest product.

Nonetheless, although the availability of commercial off-the-shelf (COTS) components and reference designs has made wireless system design a little easier, the engineer still needs to acquire some fundamental knowledge about the parameters that influence a wireless link’s performance.

A critical issue is communication reliability; how will parameters such as sensitivity, output power, adjacent channel selectivity, and operating frequency influence system performance? In other words, what is the probability of transmitting/receiving an error free data packet in the presence of other radio sources that could interfere with the signal.

A second equally critical issue is range. The designer has to ensure that the radio can operate over its stated range in a number of different operating environments. Given output power and sensitivity, what other parameters affect range? Environmental factors such as air humidity, obstacles such as people and furniture, building materials, and metal film sun-screened windows limit useful range and choice of antenna implementation.

The designer should also be very wary of taking the data sheets of some wireless component vendors as gospel. For example, if sensitivity is measured for a lower data-rate than the stated maximum then it’s worth asking why. Checking just a few fundamental characteristics such as these first may save much time and frustration later when realising that the circuit chosen does not comply with the system specifications.

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