The explosion in wireless technologies over the past ten years has been nothing short of staggering. WiFi, Bluetooth, ZigBee, ultrawideband, GPS, wireless HDMI, 60 GHz, and 2/3/4G cellular, along with mainstays such as FM radio and broadcast television, have become ubiquitous in consumer devices. The presence of multiple RF transceivers within a single device is now the norm, not the exception. Over the next ten years, the key challenge will shift from simply enabling wireless connectivity to enabling multiple wireless technologies to coexist at the same time in the same device, along with surviving the electromagnetic interference issues caused by the increasing complexity of such devices. While today's devices already feature several transceivers operating simultaneously, over the next ten years the problem will grow exponentially. It is projected that up to 10 RF transceivers may be active at any one time in a cellular handset, covering a frequency range anywhere from 100 MHz up to 3 GHz. This swath of spectrum is also broad enough that these radios will need to reject interference from a plethora of sources, such as microprocessors, switching regulators, LCD backlights, and touch panels. Likewise, the continuing march toward further integration will result in RF coexistence issues not only within devices, but within a single piece of silicon. To effectively deal with this issue, many techniques will need to be developed and deployed to attack the problem in a disciplined fashion. Active interference mitigation, currently an area of research, will become a mainstay in devices and silicon. Time synchronization between radios of different standards, will become standard practice. Local oscillator and frequency planning between multiple radios will become a necessary design methodology. While currently uncommon, such techniques represent a major aspect in the development of RF technologies over the next decade.
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