Can't beat the clock

摘要

Interference from locally generated sources of unwanted RF energy is the absolute bane of low power wireless implementations, limiting operating range and causing a whole host of awkward customer issues. Usually the interferer originates from the customer's own digital equipment (the dreaded "fog" - see the October issue of EW). This is easy to diagnose (if not necessarily to fix), but it is not the whole subject: sometimes the interferer is generated by the radio module itself. This may seem surprising: one might expect a competently designed radio module to be pretty much without any potentially problem-causing emissions, but this is not necessarily so: in a typical radio design there will usually be several oscillators integral to the architecture.