ZigBee/802.15.4 modules have innovative antenna design

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MeshNetics, a leading ZigBee technology provider, unveiled its new ZigBee/802.15.4 modules at the Electronica show in Munich, Germany, on 14 November 2006. The key feature of these tiny half-square-inch modules is the innovative dual-chip antenna design (patent pending). This new design adds up to 2dB of antenna gain, which translates into a 1.5-times increase in operating range.

The majority of ZigBee modules on the market today feature chip antennas. Such modules already contain all necessary RF design so that no RF expertise is needed to integrate them. The chip antenna design normally requires a device called 'balun' (BALanced UNbalanced) that serves to interface a single-ended antenna to a balanced input/output. As a trade-off, however, the balun causes loss of antenna gain (power). The new dual-chip antenna design, however, eliminates the need for a balun without adding to the overall bill of materials. The new antenna design is also compact: the module's footprint of only 13.5 x 24mm (0.53 x 0.95in) is said to be among the smallest on the market.

"It was a challenging task that called for an unorthodox solution. How do you gain a few extra dB without increasing the bill of materials?" said Mr Alexey Nazarov, the Product Manager of MeshNetics. "We had to take a critical look at the conventional wisdom of using balun. The next step was to redesign the antenna in order to compensate for the absence of balun. There was no ready solution available, so we created the new design from scratch."

The new module will complement the currently offered balanced RF output version in the family of the ZigBit compact modules, based on Atmel ATmega 1281v MCU and AT86RF230 RF transceiver. All new ZigBee/802.15.4 modules will come bundled with eZeeNet stack firmware that enables the module-based wireless sensor devices to form self-healing, self-organizing mesh networks. The Evaluation Kits for the new modules, scheduled for general availability in the 1st quarter of 2007, will include evaluation boards, software, accessories, and technical support over email.

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