Design and simulation of graphene based linear and circularly polarized antennas with enhanced performances for terahertz applications

Abstract

Terahertz spectrum, which lies between millimeter and infrared newlineregions has received tremendous interest due to its phenomenal properties newlinesuch as non-invasive, high spectral resolution and stronger penetration depth newlinecompared to light waves. As the demand for wireless communication newlineincreases, terahertz band is expected to provide broadband services in the near newlinefuture. It also plays a vital role in other applications such as THz imaging, newlineTHz spectroscopy, sensing, bio-medical, defence and security applications. newlineTerahertz waves are non-invasive and is not harmful to humans. A major newlinerequisite component in a terahertz system is THz antenna which radiates and newlinedetects electromagnetic waves in the THz region. Polarization of an newlineelectromagnetic wave is an important property. It is crucial to understand the newlinedirection in which an antenna is polarized and the design should include newlinepolarization aspects based on applications. A microstrip fed graphene based dual linear polarized terahertz patch antenna is proposed for the first time and its detailed antenna characteristics are analyzed. It consists of a single graphene patch placed on silicon substrate newlineand it is excited by using dual ports oriented orthogonally. These ports are newlineused to provide vertical and horizontal polarized radiations in their respective newlineport directions. The antenna resonates at 3.98 THz with a peak gain of 9.6 dB. newlineThe isolation between the two orthogonal ports is greater than 45 dB and an newlineefficiency of about 90% is achieved. Axial ratio and Envelope Correlation newlineCoefficient (ECC) are calculated for the proposed antenna. newlineCompact antenna with multi-band characteristics is required to utilize newlinethe spectrum efficiently. A simple and miniaturized single element multi-band newlineterahertz patch antenna is proposed using graphene. This is achieved by newlineexciting additional resonant modes using slot-based method. Initially, a single newlineband graphene antenna is designed at 1.9 THz with a bandwidth of 50 GHz. newlineThen, a slot is introduced to the conducting graphene patch to obtain newlinedual-frequency bands. The position of the slot in the patch is adjusted to newlineradiate at dual frequencies of 1.96 THz and 4.83 THz, whose corresponding newlinebandwidths are 80 GHz and 100 GHz respectively. VSWR less than 1.5 is newlineobtained at both frequency bands. Further, the antenna is made to operate at newlinetriple bands by introducing defects in the ground plane. It resonated at of newline1.96 THz, 4.83 THz and 5.55 THz with peak gain of 4.7dBi, 5.05 dBi, 5.5 dBi newlinerespectively and efficiency greater than 92% is achieved. newlineCircular polarization increases the information processing ability of newlineterahertz waves. A compact structure for circular polarized terahertz radiation newlineis designed. Initially, a linear polarized microstrip patch antenna is developed newlineand then modified to circular polarized antenna. The linear polarized antenna newlinehas axial ratio of 40dB with a peak gain of 4 dBi. Then, the antenna geometry newlineis modified to alter the phase of electric field by blending the opposite edges newlineof the radiating patch. It resonates at 2.05 THz with an axial ratio bandwidth newlineof 0.5 THz newline newline