## 2 Antenna Design and Configurations
Moreover, it provides more effective excitation and directional control of the leaky modes, contributing to efficient beamsteering. In terms of polarization, the layer of air can reduce the AR effectively by making a balance between the phase and amplitudes of the modes orthogonally. It also suppresses the surface waves created by substrate loss modes, enhancing the radiation efficiency. Afterward, the antenna was stacked with a layer of cavity (Interface 4/6), followed by a rectangular ring layer with coffee bean arrays on it (Interface 5/6) and an MTS layer (Interface 6/6). It should be mentioned that Interface 6/6 has a smaller dimension using MTS arrays that are identical to those in Interface 1/6 and Interface 5/6. The cavity layer has almost the same effect as the air layer, with more impact on suppressing the back radiation and side lobes and  
\[\Delta L=0.412\;\mathrm{h}\frac{\left(\varepsilon_{eff}+0.3\right)\left(\frac{ \varpi}{h}+0.264\right)}{\left(\varepsilon_{eff}-0.258\right)\left(\frac{w}{h} +0.8\right)},L_{eff}=\sfrac{c}{2f_{0}\sqrt{\varepsilon_{eff}}},\;\mathrm{L}=L _{eff}-2\Delta,\;\;L_{g}=L+(6h) \tag{2}\]0 The reflection (a) and transmission (b) coefficient results of the proposed antenna after adding each layer of the antenna at each stage of the design. sharpening the radiation pattern towards the desired radiation constructively, since it is confined by thin layers of substrate used for layer 3. Interface 5/6 introduces a periodic subwavelength structure that acts as a frequency-selective surface (FSS) element, creating passbands and stopbands in order to enhance the bandwidth around the desired working bands. The ring structure further confines the electric field positively in proximity to the leaky-wave aperture. Last but not least, Interface 6/6, with smaller dimensions and having the same MTS arrays as layer 1, creates further phase tapering spatially by acting like a nearfield phase correcting structure and also suppresses the grating lobes towards the undesired direction. Figure 6 also illustrates the transmission coefficient results for the antenna with each layer added, as well as the stages of antenna performance improvement. It shows that cutting the slots from the patch and adding layer 1 and the vacuum layer enhanced the isolation, especially at higher bands. It provides the entire band with an isolation of more than 13 dB. After assessing and evaluating the S-parameter results for the antenna, its radiation efficiency and gains should be enhanced, keeping in mind that miniaturization is also vital for CubeSat. Considering the S-parameter results of the antenna after adding each layer, the absorption coefficient, an important factor in utilizing MTS structures, was calculated using Equation (4):  
\[\Delta L=0.412\;\mathrm{h}\frac{\left(\varepsilon_{eff}+0.3\right)\left(\frac{ \varpi}{h}+0.264\right)}{\left(\varepsilon_{eff}-0.258\right)\left(\frac{w}{h} +0.8\right)},L_{eff}=\sfrac{c}{2f_{0}\sqrt{\varepsilon_{eff}}},\;\mathrm{L}=L _{eff}-2\Delta,\;\;L_{g}=L+(6h) \tag{2}\]1  
It defines a \"perfect absorber\" when \(A(f)>99\%\) (i.e., absorption coefficient \(\approx 1.0\)). It shows that this can be achieved when both reflection and transmission are minimized through impedance matching and resonant loss mechanisms [36]. For practical RF energy harvesting, absorption values above 70-80% are considered excellent, while 60% and above is workable when compensated by matching circuits and rectifier efficiency. Multi-band metamaterial absorbers are often designed to achieve >80% absorption at multiple discrete frequencies, and >60% across broader bands are acceptable, especially when balancing design trade-offs [37]. Considering all this information, the proposed antenna provides a quantitative measure of the amount of incident RF power absorbed by the structure.