(Nano Telecommunications) Nano antennas need to have a very high operating frequency in order to be usable.

Researcher  and author: Dr.   (   Afshin Rashid)



Note: In general, in order to receive the electromagnetic wave in space, the dimensions of the antenna must be in the order of the size of the input wavelength to its surface. Due to the very low dimensions of nano-sensors, nano-antennas need a very high operating frequency to be usable. 

The use of graphene greatly helps to solve this problem. Wave propagation velocities in CNTs and GNRs can be up to 100 times slower than vacuum velocities, depending on the physical structure, temperature and energy. Accordingly, the resonant frequency of graphene-based nano-antennas can be twice as low as nano-carbon nano-antennas. It has been mathematically and theoretically proven that quasi-metallic carbon nanotubes can emit terahertz radiation when a time-varying voltage is applied to their sides.

One of the most important parameters of any nano-antenna is the current distribution on it. This  characteristic determines the radiation pattern, the resistance and reactance of the radiation and many  important characteristics of the antenna.  Despite the possibility of making nanotubes with a length of several centimeters, it is possible to  make electrical conductors with a length to width ratio of 7 ^ 10  . Nanotube antennas at first glance  give us the impression that it is similar to the dipole antenna, which is designed in  small dimensions. But this is not  the case in the main theory of dipole antennas for determining the current distribution on the antenna,  where the dipole radius is greater than the skin depth and also  the resistance losses are so small that they can be ignored.  Due  to the fact that the L / d nano-dipole is significantly reduced, it is impossible is used. In single-dimensional electrical conductors such as nanotubes, the  skin depth state is completely eliminated. Because here electrons are only allowed to move They have conductors along the strand and therefore the current distribution is effectively one-dimensional. In addition to the electrons moving in only one dimension, two other important issues occur, inductance and large resistance. These properties make nanotube antennas behave very differently from classical antennas. The main difference is that the current distribution is alternating with a wavelength that is 100 times smaller than the open space wavelength for a given thermal frequency. The wavelength of the current distribution depends on the wave velocity in that mode. If the wavelength is the same as the speed of light, the wavelength of the current distribution is the wavelength of the electromagnetic waves in the open space. On the other hand, the wave velocity in nanotubes is about one hundred times slower than the speed of light. This is because in circuit theory, the wave velocity is equal to the inverse of the square root of the capacitive capacity per unit length multiplied by the inductive capacity per unit length.



Conclusion : 

Nano-antenna is considered as the primary tool for absorbing electromagnetic nanowaves in space and nano-telecommunications and has its own engineering knowledge that is very developed and extensive.

Researcher  and author: Dr.   (   Afshin Rashid)

PhD in Nano-Microelectronics