Tuesday, December 29, 2009

Samsung Creates Viable RF Nanoswitches with Carbon Nanotubes by Tuning Capacitance of Dialectic Materials


Using a MEMS (Micro Electro Mechanical Systems) manufacturing technique, MEMS RF nanoswitches have been developed by Samsung Electronics scientists, and in addition, practical and commercial nanometer sized RF nanoswitches are on the way to being developed.

FIG. 2 is a perspective schematically showing a RF nanoswitch according to an exemplary embodiment in Samsung’s U.S. Patent 7,638,790

 Samsung Electronics Co., Ltd. (Suwon-si, KR)  researchers have created an RF nanoswitch which easily transmits RF signals through carbon nanotubes, overcoming the problem of signal loss encountered in previous attempts to create nanoswitches for RF signals.  The achievement is detailed in U.S. Patent U.S. Patent 7,638,790.

The Samsung RF nanoswitch includes a first electrode unit connected to one terminal of a driving power supply, a second electrode connected to the other terminal of the driving power supply, and a dielectric material selectively coming into contact with at least one of the first electrode unit and the second electrode, depending on whether or not power is applied from the driving power supply.

Samsung RF Nanoswitch inventors Dong-ha Shim, Kuang-woo Nam, Seok-chul Yun and In-sang Song developed the nanometer-sized subminiature RF nanoswitch which solved the loss in RF signal power experienced in previous attempts to create RF nanoswitches

In prior art RF nanoswitches generated electric resistance of several tens to several hundreds k.OMEGA. at a contact portion between the  carbon nanotube and the drain. Due to such electric resistance, an RF signal could not be transmitted to the drain even if the RF nanoswitch is in the ON state or an increased loss in RF signal is caused even if the RF signal is transmitted. Thus it was difficult to commercialize such an RF nanoswitch

In Samsung RF nanoswitch, the driving power supply is a DC power supply and applies a power to the first electrode unit  and the second electrode  to produce an electrostatic force. On each circuit for connecting the driving power supply, the first electrode unit  and the second electrode  with each other, an inductor  is connected, which has inductance sufficiently high to prevent the transmission of an RF signal to the driving power supply. As the impedance of each circuit connected to the driving power supply is increased by the corresponding inductor, the RF signal could not be transmitted to the driving power supply.

According to the Samsung researchers, by tuning the RF switch capacitance by means of a dielectric material, it is possible to reduce the impedance in the RF nanoswitch in which an increased loss in RF signal is caused due to contact resistance produced by a contact between an existing nanotube and a drain, making it possible to stably transmit an RF signal without any loss. In addition, by tuning the impedance by means of capacitance, it make it possible to commercialize a nanometer-sized subminiature RF nanoswitch.

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