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takyon [soylentnews.org] writes:

DARPA is seeking to build very low frequency [wikipedia.org]/ultra low frequency [wikipedia.org] transmitters that are also very small [networkworld.com]:

Wireless transmitters that operate at very or ultra low frequencies (0.3‐30 kHz) typically require some big antenna complexes to handle their communications. Scientists at the Defense Advanced Research Projects Agency (DARPA) said they are interested looking to eliminate that issue and develop smaller physical structures that could handle new long-distance communication applications.

In a Request for Information, DARPA wrote: "At these frequencies, free‐space electromagnetic (EM) field wavelengths are measured in tens of kilometers, resulting in very large transmitter structures when employing conventional antenna approaches. Electrically‐small antennas are defined as having dimensions much smaller than the EM wavelength, with examples in the literature of antenna‐sizes as small as 1/10th of the EM wavelength. DARPA is seeking innovation to bring that size below 1/10,000 of the EM wavelength or by at least a factor of 10³ smaller than the current state of the art (SOA)."

Such a tremendous reduction in size is impossible to achieve through traditional antenna design so DARPA said it is looking to gather information "in the areas of materials, mechanical actuation, and overall transmitter architectures to address impedance matching, power handling, signal modulation, scalability, and other system level considerations."

The article mentions other wireless research that DARPA is involved in, including the XPRIZE-like Spectrum Collaboration Challenge [spectrumcollaborationchallenge.com].

Original Submission