Design and Investigation of Characteristic Structure Split Ring Resonator Circular of Microwave Metamaterial Absorber Parameter in X-band Frequency

This paper explained the design and investigation of the characteristic structure of split ring resonator circular in the parameter of microwave metamaterial absorber in X-band frequency. The result showed that bigger value of inner radius circular geometry obtained the resonance frequency shifted to bigger such as 9.20 GHz to 9.30 GHz, and maximum absorption rate increased from 88.9% to 93,35%. When the inner radius smaller and the outer higher, represented the resonance frequency shifted to lower, 11.13 GHz to 9.94 GHz, and the maximum absorption rate decreased from 85% to 78,27%. In another condition, the lower gap variation affected resonance frequency shifted to lower 9.30 GHz to 9.13 GHz but maximum absorption rate increased 88.64% to 89,2%, thus opposite. Keywords—Absorption rate, Resonance frequency, a split ring resonator, Gap width, geometrical radius circular, X band


I. INTRODUCTION
For last years, the microwave metamaterial absorber technology was interested in the researcher, actually in the microwave field. This reason indicated that microwave has an advantage and unique feature in many applications, such as microwave, terahertz, infrared and optic [1] [2], and [3]. In 1968, a physicist, who named Victor Vaselago pioneered in electrodynamic isotropy research field also obtained dielectric constant and magnetic permeability which negative, so metamaterial began [4]. I 1999, a physicist from Great Britain, John Pendry, proved metamaterial theory from Vaselago to make a combination between coal wire and structure split ring resonator, which basically to obtain negative dielectric constant, thus resonator ring to make negative permeability [4].
Metamaterial absorber is an artificial composite structure which consists of two metal layers of the electric resonator, another side is a ground plane, and the middle is dielectric layer [5]. Split ring resonator is a structure represented electrical circuit about resonance frequency shifted [6] [7], and [8]. In this research, will explain a design and characteristic investigation of structure split ring resonator circular in microwave metamaterial absorber parameter, which means to know about the effect of wide radius characteristic in geometrical circular and also gap width of microwave metamaterial absorber parameter such as resonance frequency absorption rate.
This research is expected that the result of an investigation between characteristic circular radius width and a gap width of microwave metamaterial absorber can be applied in any research fields, such as to apply microwave, mutual coupling, radar cross section, airborne and chamber room. From the background that presented, this research will purpose "Design and Investigation of Characteristic Split Ring Resonator Circular in Microwave Metamaterial Absorber Parameter in X-band".

A. Calculation of Structure Unit Cell Split Ring Resonator Circular
In this chapter explaining the dimensional calculation of structure unit cell split ring resonator circular used equivalent circuit approach [9]. The Sub-wavelength of structure unit cell split ring resonator circular characterized in inductance (L) and capacitance (C). The geometrical circular structure unit cell is shown in Figure 1.
The inductance can be approximated in that of a closed ring [9].

C. Unit Cell Structure Split Ring Circular Design of Microwave Metamaterial Absorber
In this chapter, processing unit cell structure design split ring resonator circular used software Computer Simulation Technology (CST) studio. The material specification in this research is decided in Table 1. Simulation design of structure unit cell split ring circular is shown in Figure 2. From Table 2, presenting some dimensional specifications of the structure unit cell split ring circular is established in the resonance frequency, therefore the simulation design in this process will be taken in two X-band frequency samples, 9.23 GHz, and 10.14 GHz. In Table 3, the validation calculating of dimensional structure unit cell split ring circular used LC method which noticed about radius dimension, thick substrate, wide radius and wide gap are equal with dimension in Table 2.

D. Absorption rate
Basically, the absorption rate chart can be obtained from the correlation among scattering parameters which are determined by 11 and 21 . The absorption values will work well in 80% required by 11 < -5 dB and magnitude 21 is 0 which assumes power blocked [11]. The result of 11 graph and absorption rate from each resonance frequency is shown in Figure 3. 11 parameter rate chart in resonance frequency 9.21 GHz with minimum value -9.5 dB is shown in Figure 3.

International Conference on Engineering, Advance Science and Industrial Application (ICETESIA) 2018
September 6-7 2018, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 11 parameter rate chart in resonance frequency 9.21 GHz with minimum value -8.92 dB is shown in Figure 4. Absorption rate chart for each resonance frequency is referred in 5 and 6. Maximum absorption rate chart in frequency 9.21 GHz is 88.9% shown in Figure 5 and in frequency 10.1 GHz is 87.22% as shown in Figure 6.

IV. PARAMETRIC ANALYSIS OF THE PROPOSED UNIT CELL STRUCTURE SPLIT RING RESONATOR CIRCULAR
In this chapter, the design of unit cell split ring resonator circular is investigated in a characteristic parameter such as the width of the inner and outer geometric circular and gap width.

A. Inner Radius Variation (Ri) in Geometrical Circular
The effect of characteristic inner radius width (Ri) in a geometrical circular in microwave metamaterial absorber parameter is analyzed. There are two conditions, increasing and reducing the value of the inner radius. The former in 9.2 GHz and the later 8.4 GHz. For the specification, dimensional and various inner radius (Ri) in the geometrical circular are shown in Table 4 and 5. Absorption rate chart 11 and parameter shown in Figure 7 and 8.   Absorption rate chart 11 and parameter shown in figure 9 and 10.

B. Variation value of outer radius in (Ro) geometrical circular
In this chapter, the effect of characteristic outer radius (Ro) width in a geometrical circular in microwave metamaterial absorber parameter is analyzed. There are two conditions, such as increasing outer radius (Ro) of the resonance frequency of 11.1 GHz, and decreasing 10.1 GHz. The dimensional specifications of various outer radius (Ro) in the geometrical circular are shown in Table 6 and 7.  Absorption rate chart 11 and parameter shown in Figure 11 and 12.  Absorption rate chart 11 and parameter shown in Figure 13 and 14.

C. Various Values of Geometrical Circular Gap Width
By this chapter, the effect of characteristic gap width in unit cell structure split ring circular in microwave metamaterial absorber parameter. The specification of gap width unit cell structure circular shown in Table 8.

V. CONCLUSIONS
The design and characteristic investigation of structure split ring circular in microwave metamaterial absorber parameter in X-band frequency are established. From table IV, various values of increasing inner radius (Ri) resulted in higher resonance frequency and shifted to the higher frequency and maximum absorb rate increased. Nevertheless, from table V showed that decreasing inner radius (Ri) resulted in opposite. Table VI informed that various values of increasing outer radius (Ro) resulted resonance frequency shifted to a lower frequency and maximum absorption rate decreased, so did opposite in table VII. Moreover, table VIII showed that various values of decreasing gap width resulted in resonance frequency shifted to lower frequency but maximum absorption rate increased. We can obtain that the results of the investigation between structure split ring resonator circular and LC equivalent circuit resulted in frequency shifted higher in smaller L and bigger C, and opposite.