AValon RF Uses Blackfin® for Wireless A/V Tools
from Combat to Newsgathering
Leapfrog advances in communications, sensors, and materials technologies have transformed the equipment inventory carried by today's soldier beyond the realm of the well-oiled weapon. Included are far-flung items like video cameras, microphones, and global positioning systems (GPS) – tools that let leaders and soldiers exchange video, audio and data. The Future Combat System (FCS) contents of the new-age kitbag provide soldiers with accurate target location capabilities, enabling operation in harsh weather or close to zero light conditions, and even allowing shots to be taken around corners without exposure to enemy fire. Above all else, today's tools of the battlefield are aimed at helping soldiers survive.
In the urban combat theater, "land warriors," like police, fire fighters, medics and security guards, can also benefit from these lightweight, wireless video/audio tools. While the uses may differ, wireless systems like these must be compact, energy efficient, easy to produce, and affordable, if they are to become successfully applied in military and commercial/industrial contexts.
AValon RF, located in El Cajon, CA, develops and manufacturers such wireless products. The company's original products were based on true diversity wireless technology that allows fast video, audio, data, and telemetry communications over dial-up phone lines and wireless media ("in air," or under water).
A pioneer and innovator dedicated to the delivery of state-of-the-art wireless products at affordable prices, AValon RF set out to develop its next-generation of products based on the latest space-time wireless technology. For this, AValon RF turned to Analog Devices, Inc. (ADI) for its Blackfin® processor. Blackfin embodies a new breed of embedded processor that combines high performance and low power. Blackfin was designed specifically to meet the computational demands and power constraints of today's embedded audio, video, and communications applications.
A Stronger Signal
AValon RF products target high mobility applications for military, government, private industry, and consumers. The company's products can be used for unmanned air, ground and sea vehicles, mine sweeping, long-range video links for border patrol, covert surveillance, maintenance of nuclear power plants, electronic newsgathering, wireless TV viewing, and many other applications. To accommodate these applications, AValon RF products carry one-way video, alarm, and telemetry, two-way audio and data, and cover frequencies from 56 MHz to 2.5 GHz.
Developers of high mobility products must take care to manage signal fading, which can result when multiple signals from different paths cancel each other out at the receiver antenna, or when large objects obstruct the line of sight between the antenna/transmitter. It can also happen as a result of humidity, fog, or rain, or from an overcrowded spectrum. Signal fading is often managed by capturing the strongest signal from an array of multiple antennas (a technique called antenna diversity). There are numerous types of diversity technologies and numerous types of diversity receivers.
The most commonly used method for mobile applications is space diversity, which ensures that at least one antenna at any given time will not be subject to distortion. With multiple antennas placed at a site, one can control the proximity of the transmitter antenna to one of the receiving antennas. Signal fading is further complicated in a mobile environment in that the "nulls" are not fixed in space, but vary in time; the user is moving and so is the environment. "Developing wireless products that deliver reliable audio/video is tough," said Eli Weinstein, CTO of AValon RF. "The likelihood of unwanted interference is high when you're transferring audio/video back and forth between two moving objects."
One of the newest and best solutions to signal-fading issues in mobile environments is space-time diversity, whereby signal processing is performed on a receiver that comprises several antennas, exploiting both the spatial (space) and temporal (time) dimensions of a radio channel. AValon RF planned to update its entire product line–transmitters, lapel cameras, diversity receivers, boom cameras, and wireless digital microphones–to cutting-edge space-time diversity technology.
High Performance, Low Power, Cost
AValon RF's space-time diversity receiver is essentially a software-defined radio (SDR), which requires a processor to handle SDR functions and space-time diversity processing for the receiver. Said Weinstein, "We needed a high-performance processor that could handle the complex mathematical algorithms this application requires. It had to be low power so that we can use smaller batteries for lighter, more comfortable products our customers can wear. And it had to be cost-effective so that we can manufacture products our customers can afford to buy in volume."
"Blackfin was the best choice for us. It is the smallest chip on the market. It doesn't waste battery power," he continued. "It's very powerful. And it's affordable."
Blackfin processors combine a 32-bit RISC-like instruction set and dual 16-bit multiply-accumulate signal-processing functionality with the ease-of-use attributes found in general-purpose microcontrollers. For power savings, Blackfin processors are based on a gated clock core design that selectively powers down functional units on an instruction-by-instruction basis. Blackfin supports multiple power-down modes for periods where little or no CPU activity is required. Blackfin also features a dynamic power-management scheme whereby the operating frequency and voltage can be tailored to meet the performance requirements of the algorithm currently being executed. As such, Blackfin processors are particularly well suited for portable applications requiring extended battery life.
Weinstein says another benefit of working with ADI is that he was able to purchase a whole suite of products from the company in addition to the Blackfin processors. "ADI is one of the very few companies where you can get everything you need to build a radio under one roof."
Thanks to Blackfin, AValon RF's space-time diversity receivers offer the best possible signal-to-noise ratio, using signals from all antennas to create an output. That translates to a 6dB gain in a four-antenna system. The receivers clean up most, if not all, multi-path distortion and compensate for receiver/transmitter motion by measuring the Doppler shift and spread, and by shifting the spectrum. AValon RF's space-time receivers convert line-of-sight systems into non-line-of-sight systems by tuning in to the multi-path signals in the absence of a direct signal. And they eliminate jamming signals from unwanted directions. This adds up to high-mobility solutions that deliver audio/video data without fail, which, on the battlefield, can mean the difference between life and death.