## 1 Introduction
suggested a metamaterial absorber unit cell assembly with magnitudes 10.92 \(\times\) 10 mm\({}^{2}\) that was used in a microwave system that showed the highest absorbance 99.6% at a resonance frequency of 2.38 GHz [21]. To analysis the absorption properties, [PERSON] et al. designed a multi-band split S-shaped metamaterial absorber which absorbed a maximum of 55% of incident electromagnetic radiation [22]. A broadband perfect metamaterial absorber of dimension 10 \(\times\) 10 mm\({}^{2}\) on the basis of electric split ring resonator (ESRR) loaded with lumped resistors presented by [PERSON] et al. It showed the absorption rates of 99.3%, 97.1% and 98.6% at the resonance frequencies 5.45 GHz, 15.46 GHz, and 19.48 GHz, respectively [23]. In 2015, [PERSON] et al. [24] recommended a design scheme of absorbing metamaterial which absorbed nearly full incident EM radiation on it. It was measured, characterized, and finally recognized as a perfect metamaterial absorber (PMA) with an outstanding absorbance of 99.99% at 5.48 GHz and 99.92% at 0.865 THz. A terahertz dual band MA was proposed by [PERSON] et al. that showed two distinct absorptions of nearly 81% and 63% at 0.45 THz and 0.92 THz, respectively [25]. A multilayer dual band metamaterial absorber was presented by [PERSON] et al. in megahertz area [26]. It showed average absorptions of 96% in the 4 to 6 GHz frequency range. [PERSON] (2015) proposed a variable terahertz absorber [27]. Its characteristics were analyzed numerically, and it absorbs 96-99% at the resonance frequency range of 2.14-9.94 GHz. A Jerusalem cross metamaterial of dimension 24 \(\times\) 24 mm\({}^{2}\) with roamed load absorber represents absorptions of more than 95% at resonance frequencies of 14.75 GHz and 16.1 GHz [28]. [PERSON] et al. [29] designed a new metamaterial-based absorber for multiple applications at Gigahertz and Terahertz frequencies. In the numerical simulation at the resonance frequencies of 2.8 GHz, 4.1 GHz and 5.8 GHz, it showed absorbance of 99%, 99% and 89%, respectively. It exhibits maximum absorbance of 99.46% at 265.8 THz and 99.40% at 556.4 THz. A cross shape design of metamaterial absorber in 2017 was presented by [PERSON] et al. [30] with a size of 500 \(\times\) 500 nm\({}^{2}\). It absorbed a high rate of absorbance, 98.40% of incidental EM waves. A triple hexagonal SRR-based metamaterial sensor was reported in [31] to detect fuel (petrol, kerosene, and grease) contaminants which are used for real time applications. Moreover, [PERSON] et al. developed a broadband metamaterial absorber which is based on square shaped water metamaterial [32]. A newly improved version of C shaped SRR metamaterial with artificial neural network was designed to show improved quality factors because of using ANN on the design and determine dimension of the MTM structure [33]. In this paper, a dual band (C- and Ku-) octagonal close ring resonator (OCRR)-based dumbbell-shaped tuning fork metamaterial absorber is presented. It exhibits dual resonance (C, Ku) at 6.45 GHz and 14.89 GHz with an absorption rate of 99.15% and 99.76% respectively. Additionally, an attempt has been made to investigate the performance of the proposed PMAs by alternating the polarization angle and oblique incidence angle in the transverse electric (TE) mode of unit cell, array combination, and different widths of octagonal ring resonator and split gap of double tuning fork. The dimension of proposed unit cell is 8 \(\times\) 8 mm\({}^{2}\) which is very compact compared to the PMAs as stated in [19; 22; 34; 35; 36; 37]. Moreover, the proposed design is very simple and highly symmetric structure that can be operated easily. The pluses of the designed structure are FR-4 substrate and insensitive to polarization angle up to 30\({}^{\circ}\).