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Mojix Takes Passive UHF RFID to a New Level

The startup draws on RF expertise from deep-space signal processing to create a system that it says will offer improved performance, new capabilities and lower deployment costs.
By Mark Roberti
Apr 14, 2008 Newly emerged from stealth mode, Mojix, a startup company based in Los Angeles, plans to launch a new type of RFID system at this week's RFID Journal LIVE! 2008 conference in Las Vegas. The system uses techniques developed for deep-space communication to significantly boost the read range of passive UHF tags, as well as identify their precise location in three dimensions.

The Mojix STAR system reads passive ultrahigh-frequency (UHF) RFID tags based on EPCglobal's second-generation air-interface protocol. According to the company, a single STAR receiver can cover an area of up to 250,000 square feet, pinpointing tags in 3-D space.

"This is a breakthrough that renders all applications in the supply chain more economical," says Ramin Sadr, Mojix's founder and CEO. "The technology is based on signal-processing techniques developed to detect communication from deep space. We use a completely new architecture. This is the first time that anyone has been able to read tags at 600 feet or more, and identify their location in three-dimensional space with great precision."

The signal-processing techniques employed by Mojix center on an antenna technology known as phased array, which uses a group of antennas that are able to focus on the signals being received, thereby strengthening desired signals and canceling out noise. Sadr, a former NASA scientist and telecommunications industry entrepreneur, formed Mojix in 2004 and assembled a team of scientists and engineers to apply steerable phased-array antenna technology to RFID interrogator antennas, enabling them to pick up faint backscatter transmissions from passive tags that would be missed by conventional RFID systems.

In addition, Mojix's system takes a different approach to powering an RFID tag. Most conventional RFID systems are monostatic, using the same reader antenna to transmit energy to power up a tag and receive its signals back. This makes it difficult to read the signal reflected back from the tag, since that signal is much weaker than the one emitted by the reader antenna. Even bistatic systems, which transmit energy to power up a tag with one set of antennas and receive the signal back from the tag with another, typically place the send and receive antennas in the same general location.

Mojix has separated the transmit and receive functions geographically. Its system consists of a distributed network of transmitters, known as eNodes, to power up the tags, and a single STAR receiver to pick up the tags' signals. The STAR receiver has four patch antennas, designed to form an RF beam that can be electronically steered and adjusted in width, depending on the area of coverage required. The STAR receiver also controls the eNodes, which are connected to the receiver by coaxial cable (the eNodes can be daisy-chained, and the company plans to create a version that can be linked wirelessly via a standard Wi-Fi network).

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