A tiny, novel device for generating tunable microwave signals has been developed by researchers at the National Institute of Standards and Technology (NIST). Described in the Jan. 16 issue of Physical Review Letters, the device measures just a few micro-meters square and is hundreds of times smaller than typical microwave signal generators in use today in cell phones, wireless Internet devices, radar systems and other applications.
A three-dimensional plot shows how the microwave frequency (x axis) generated by a new NIST oscillator varies with changes in the current (y axis). The height of each peak represents the power of the signal produced at specific frequencies.
The device works by exploiting the fact that individual electrons in an electric current behave like minuscule magnets, each one with a “spin” that is either up or down, just as an ordinary magnet has a north and a south pole.
The NIST device consists of two magnetic films separated by a non-magnetic layer of copper. As an electric current passes through the first magnetic film, the electrons in the current align their spins to match the magnetic orientation in the film. But when the now aligned electrons flow through the second magnetic film, the process is reversed. This time the alignment of the electrons is transferred to the film. The result is that the magnetization of the film rapidly switches direction, or oscillates, generating a microwave signal. The microwave signal can be tuned from less than 5 gigahertz (5 billion oscillations a second) to greater than 40 GHz.
Fred McGehan, | NIST
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