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New Tunable Dielectric May Resolve Wireless Device Antenna Issues

As wireless carriers slowly move towards gobbling up all usable spectrum, manufacturers of devices that have to operate over a wide range of frequencies are having trouble finding room for antennas for all of these frequencies in device sizes that people want to purchase.

One way of solving this problem is to use tunable antennas or antenna matching networks to provide coverage over a wide frequency range. Thanks to the work of researchers at Cornell University, this may become easier and more efficient.

A five-year multidisciplinary collaborative research effort based at that school has resulted in what the researchers call “the world's best material [dielectric] for tunable capacitors.

“This is a radically different material compared to what people have been using for decades,” said Darrell Schlom, the Herbert Fisk Johnson Professor of Industrial Chemistry at Cornell who led the international team. “What we have discovered is the world’s lowest-loss tunable dielectric.”

The tunable dielectric is made from layer strontium titanium oxide--a material not found in nature--that's created through molecular beam epitaxy. A “materials by design” method was used to give the material have the desired properties.

Schlom explained that the tunable dielectric and its properties were first envisioned on paper, tested on the computer, created in the lab atom by atom, patterned into a capacitor device and, finally, verified with electrical measurements. The result is a tunable dielectric capacitor with at least five times the performance of commercial tunable capacitors available today.

Schlom commented, “It is clear that we have discovered a killer material, but it is likely that even better tunable dielectrics can be found using our approach.”

The research was published in the paper “Exploiting Dimensionality and Defect Mitigation to Create Tunable Microwave Dielectrics” in the Oct. 16 issue of the journal Nature. The Cornell University press release Tunable antenna could end dropped cell phone calls has additional information.

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.