A graphene aided rectangular dielectric resonator antenna is designed for 5G application and results are measured with different parameters. Silicon made dielectric resonator is containing four graphene rectangular layers is made for measuring the changes in the frequency response. By changing the chemical potential of graphene rectangular plates placed on the silicon rectangular dielectric resonator antenna the resonance THz frequency can be changed accordingly. The measured results for an RDRA show an impedance bandwidth of 69.81% between the frequency range 3.89 THz to 8.062 THz, and the gain of 5.082 dB.
The Sample model of RDRA is shown in Figure 1. Which is involving a silicon dioxide substrate with dielectric constant (ϵs=4) with the dimensions 42(LSUB) × 42(WSUB) × 8(HSUB) um3 which is kept on top of the ground plane. The ground plane made of silver with dielectric constant (ϵs=1) has dimension 42(LG) × 42(WG) × 8(HG) um3. A silicon dielectric resonator (ϵr=11.9) having dimensions 3.5(LR) × 3.5(BR) × 3(HR) um3 is placed on top of the substrate.
Silicon distributing profile is constant over the band of guiding frequency. Afterward, the size of the antenna has been optimized for getting the desired result. The mode of excitation of the dielectric resonator depends upon the value feeding technique and aspect ratio of the antenna. The rectangular resonator provides the distribution of field at 5.535 THz resonance frequency. The dielectric resonator is mounted above the slot of width 3.4 mu and length of 3.4 mu and it is located on the backside of the dielectric resonator. Figure 2 shows the dielectric resonator. The excitation applied to the dielectric resonator by microstrip feedline made of silver material (ϵf=1) having a thickness of 1 mu shown in Figure 3, for the lower frequency range, the constructive and dispersive properties of silver material used as antenna parameter. For getting the tunabilit in result of antenna ,The graphene layer having properties define by parameters like relaxation time, chemical potential at temperature=300k is deposited on the dielectric resonator clarified in Figure 4.The structure of the antenna is implemented by the CST microwave studio.
For understanding antenna operation, the authors analyzed the result of two structures, one is implemented without the graphene layers and another is implemented with graphene layers. Figure 5 indicating the result of S11 for both the antenna at a resonance frequency. The graphene rectangular layer is placed on three sides and top of the dielectric resonator. The impedance of the antenna is nonreactive and its real parts lie in the resonance frequency. The graphene layer having properties i.e., chemical potential (μc = 0 eV) and relaxation time (τ=1ps) at temperature (300 K) causes frequency response and resonant frequency to shift in the forward direction. The new resonant frequency of the antenna becomes 5.535 THz after the graphene layer is being placed on the top of the dielectric resonator. The displacement in the resonant frequency is responsible for the changes in the medium and material properties at the linking of silicon dielectric resonator and graphene boundaries placed on resonator’s outer surface. Also, it denotes that changing the electrical properties of materials placed on the dielectric resonator can tune the antenna response. The rectangular graphene layer remains nonresonator over the frequency range. The impedance bandwidth of the antenna is observed to be approximately the same in both cases. A rectangular cut on a dielectric resonator gives the desired result of the antenna.
The comparison of the S11 parameter is shown in Figure 5 with and without the graphene layer. S11 represents how much power is reflected from the antenna. It is observed that the DR with graphene layer has return loss (S11) of -37.29 dB at frequency 5.53 THz, and the DR without graphene layer has return loss (S11) of -32.475 dB at frequency 5.62 THz. Hence the RDRA with graphene layer has a better S11 parameter as compare to the RDRA without graphene layer.
Figure 8 illustrates the Cross-polar plot of the RDRA with the graphene layers and without the graphene layers. Figure 8(a) shows the Cross-polar plot of RDRA with the graphene layers and Figure 8(b) shows the Cross-polar plot of RDRA without the graphene layers. Cross polarization means when the polarization of both the antennas is different. The angular width is 35.5 degree in the RDRA with graphene layer and 33.7 degree in the RDRA without graphene layer.
The Directivity at E-plane is shown in Figure 10. Directivity of an antenna is defined as the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. The E-plane is defined as the plane containing the electric field vector and the direction of maximum radiation. The observation of H-field and E-field distribution helps in recognizing the tunability of the antenna the value of main lobe magnitude of directivity at E-plane with the graphene layer is 9.86dB shows in Figure 10(a), and 9.95dB in the RDRA without graphene layer as shows in Figure 10(b).
Figure.11 illustrates the VSWR (voltage standing wave ratio) and also refers to the standing wave ratio. VSWR is the function of the reflection coefficient, which describes the power reflected from the antenna. VSWR depends on the reflection coefficient (return loss) of the RDRA means the higher the reflection coefficient better the VSWR.
Figure 11(a) clearly shows the VSWR value as 1.027 at 5.535 THz frequency for the rectangular dielectric resonator antenna with rectangular graphene layer, and Figure 11 (b) shows the VSWR value as 1.047 at 5.62 THz for the rectangular dielectric resonator antenna without rectangular graphene layer. VSWR shows that the antenna perfectly matches with desired result and the desired application. (b) Figure 12: Z11 parameter of RDRA (a) with graphene layer (b) without graphene layer
Figure 13 shows the 3D radiation pattern of the rectangular dielectric resonator antenna. Figure 13(a) shows the 3D radiation pattern of the rectangular dielectric resonator antenna with a rectangular graphene layer, Figure 13(b) shows the 3D radiation pattern of the rectangular dielectric resonator antenna without a rectangular graphene layer.
3-D radiation pattern plot with and without the graphene layer is showing in Figure 13. Directivity of the antenna with graphene layer is 9.79 dB and without the graphene layer is 9.95 dB. This shows that the antenna transmits and receives information from all directions. The top shows the mandate example of a horn radio antenna, the base shows the omnidirectional example of a basic vertical receiving antenna. Radiation pattern are diagrammatical portrayals of the circulation of emanated energy into space, as an element of bearing.
The E-field and H-field distribution is shown in Figure 14 and Figure 15 which shows the radiation mechanism of DRA can be obtained by observing the E-Field and H-Field distribution. Generation of hybrid modes is also obtained by observing it. E-field distribution show there are eight quadruple of Efield in the RDRA. H-Field distribution shows vertical electrical quadruple surrounded by the horizontal rectangular layer. After observing it is concluded that there are four vertical electrical dipoles is generated which shows that antenna operates in desire mode (HEM41δ).
In this paper, the authors analyze and simulate RDRA (rectangular dielectric resonator antenna) for 5G application. The Frequency response of RDRA is improved by changing the chemical potential of the rectangular graphene layer placed on the sides of the rectangular dielectric resonator. THZ rectangular dielectric resonator antenna without rectangular graphene layer has 4.998 dB gain 75% radiation efficiency. The performance parameter is increased in the RDRA with graphene layer, it provides 5.082 dB gain and radiation efficiency up to 78% -89% with the tunable THz frequency response.
The authors are thankful to Galgotia’s College of Engineering and Technology for supporting this work. And also like to thank Mr. Atul Kumar, under whose guidance this work is done, they taught us the new concepts related to our word and various methods of improving the parameters .and also thank Mr. Saurabh katiyar for suggesting various improvement in our work.