The world’s first fully digital radio transmitter promises to improve the wireless communications capabilities of everything from 5G mobile technologies to the multitude devices aimed at supporting the Internet of Things, or IoT (a proposed development of the Internet in which everyday objects have network connectivity that allows them to send and receive data).
Dubbed Pizzicato, the prototype radio consists of an integrated circuit that outputs a single stream of bits, an antenna, and not much else. It has no conventional radio parts or digital-to-analogue converter. Algorithms perform the necessary ultra-fast computations in real time, thus enabling standard digital technology to generate high frequency radio signals directly.
"Our first trial of the technology has created 14 simultaneous cellular base station signals," says Monty Barlow, director of wireless technology with Cambridge Consultants, the product development and technology consultancy firm which created Pizzicato.
But it’s the digital technology of the Pizzicato-based radio that excites Barlow. Like mainstream processing, he explains, the device should benefit from Moore’s Law (the observation that processor speeds, or overall processing power for computers will double every two year), thus shrinking in cost, size and power consumption with each new generation of silicon fabrication.
“We believe that, in the same way that microprocessors went from being expensive to being cheap enough to be installed in many everyday items, our technology can do the same for radio systems,” he adds.
The implication looms large because of the limited availability of radio spectrum bands, particularly in the more popular lower frequency ranges (less than 1 GHz). Good radio spectrum is a scarce resource. Only low frequencies (1GHz or lower) propagate well over distance or through walls, so they are in great demand. Analog circuits or even the more advanced analog-digital amalgams used in software-defined radio (SDR) are rapidly approaching their limits.
“Crowding 50 analogue radios together on one chip, switching their operational parameters every few microseconds and expecting them to work at 60GHz is an analogue designers nightmare,” Barlow says.
One way to improve efficiencies at these frequencies is the employment of dynamic switching capabilities to sense the radio environment and switch various settings as required, in real time. In other words, by using a type of "cognitive wireless" technique to intelligently control the way that signals are sent and received, therefore, make maximum use of the available spectrum. Cognitive radios are an evolution of software-defined radios. They implement baseband processing functions in software and use agile radio frequency (RF) front ends that can operate across a wide range of frequencies.
Barlow adds finally, "if we’re going to get high-speed broadband to every mobile phone in the world, we’ll need lots of tiny, high-performance radios in those phones. The radios will be squashed together in a way that analog just doesn’t tolerate, whereas a Pizzicato-like digital radio could also be programmed to generate almost any combination of signals at any carrier frequencies, nimbly adapting its behavior in a way that is impossible in conventional radios.”
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