Extremely high frequency is the highest radio frequency band. EHF runs the range of frequencies from 30 to 300 gigahertz, above which electromagnetic radiation is considered to be low (or far) infrared light, also referred to as Terahertz radiation. This band has a wavelength of ten to one millimeter, giving it the name millimeter band or millimeter wave.

A team of researchers at the UCLA Henry Samueli School of Engineering and Applied Science have achieved a new world record in high-frequency submillimeter waves. The record-setting 324-gigahertz frequency was accomplished using a voltage-controlled oscillator in a 90-nanometer complementary metal-oxide semiconductor (CMOS) integrated circuit, a technology used in chips such as microprocessors.

The new frequency is 70 percent faster than that obtained by any other CMOS (Complementary metal-oxide-semiconductor) oscillator and virtually impossible to generate with traditional circuits, because conventional oscillator circuits are nonlinear systems in which increases in frequency are accompanied by a corresponding loss in gain or efficiency and an increase in noise, making them unsuitable for practical applications.

To obtain it the researchers first generated a voltage-controlled CMOS oscillator, or CMOS VCO, operating at a fundamental frequency of 81GHz with phase-shifted outputs at 0, 90, 180 and 270 degrees, respectively. By linearly superimposing these four (or quadruple) rectified phase-shifted outputs in real time, they ultimately generated a waveform with a resultant oscillation frequency that is four times the fundamental frequency, or 324 GHz.

This new frequency generation method, in principle, has high DC-to-RF conversion efficiency (up to 8 percent) and has low phase noise, comparable to that of the constituent fundamental oscillation signal.

The measurement test of the 324-GHz signal was conducted by engineers Lorene Samoska and Andy Fung of NASA's Jet Propulsion Laboratory in Pasadena, which has facilities to test these high-frequency ranges.

No wonder JPL and NASA are particularly interested in submillimeter technology, since the applications have high commercial and scientific value.

The new frequency is ideal for deep-space remote sensing, since there is no atmosphere in space to dampen the signals. Higher frequency signals, in turn, produce higher resolution images.

It could pave the way for a new generation of submillimeter devices that could someday be used in high-resolution sensors on spacecraft, and here on Earth in a new class of highly integrated and lightweight imagers that could literally cut through fog and see through clothing fabrics.

For example, it would be possible to remotely view if some civilian walking into a building or just passing in the street has plastic explosives hidden under his coat.

And because frequency ultimately means bandwidth, the higher frequency increases the available bandwidth. That greater bandwidth translates into faster communication speeds.