# A Polarization Independent Quasi-TEM Metamaterial Absorber for X and Ku Band Sensing Applications
## 3 Absorption and Pressure Sensor Results and Discussion
### Pressure Sensor on Simulation Environment
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Polarization** **Angle (\(\varphi\))**} & \multirow{2}{*}{**Resonance** **Frequency (GHz)**} & \multirow{2}{*}{**Max Absorption (\%)**} & \multirow{2}{*}{\(\epsilon\)} & \multirow{2}{*}{\(\mu\)} & \multirow{2}{*}{\(\
u\)} & **EM** **Mode** & **Substrate** &
\begin{tabular}{c} **Dielectric** **Constant (\(\epsilon\)\(\epsilon\)\(\epsilon\))** \\ \end{tabular} \\ \hline
0 & 13.78 & 99.6 & \(-1.484\) & \(-0.361\) & \(-0.887\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.3 & 99.14 & 0.002 & \(-1.054\) & \(-0.460\) & & & \\ \hline
10 & 13.74 & 99.52 & \(-1.601\) & \(-0.343\) & \(-0.885\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.27 & 99.1 & 0.073 & \(-1.114\) & \(-0.4466\) & & & \\ \hline
20 & 13.78 & 99.6 & \(-1.484\) & \(-0.361\) & \(-0.887\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.3 & 99.14 & 0.002 & \(-1.054\) & \(-0.460\) & & & \\ \hline
30 & 13.78 & 99.6 & \(-1.484\) & \(-0.361\) & \(-0.887\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.3 & 99.14 & 0.002 & \(-1.054\) & \(-0.460\) & & & \\ \hline
40 & 13.78 & 99.6 & \(-1.484\) & \(-0.361\) & \(-0.887\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.3 & 99.14 & 0.002 & \(-1.054\) & \(-0.460\) & & & \\ \hline
50 & 13.78 & 99.6 & \(-1.484\) & \(-0.361\) & \(-0.887\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.3 & 99.14 & 0.002 & \(-1.054\) & \(-0.460\) & & & \\ \hline
60 & 13.78 & 99.6 & \(-1.484\) & \(-0.361\) & \(-0.887\) & \multirow{2}{*}{TEM} & FR-4 (lossy) & \multirow{2}{*}{4.6} \\  & 15.3 & 99.14 & 0.002 & \(-1.054\) & \(-0.460\) & & & \\ \hline
60 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & \\ \hline
10 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & & \\ \hline
20 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & & \\ \hline
30 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & & \\ \hline
40 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & & \\ \hline
50 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & & \\ \hline
60 & 12.95 & 91.39 & \(-1.327\) & \(-4.437\) & \(-1.515\) & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parametric characteristics study of proposed MM absorber at the resonance frequency. millimeter wave applications, space satellite transceivers, etc. Waveguide ports 1 and 2 are used for field excitation. To evaluate the unit cell for pressure sensitivity through simulation, the sensor layer thickness was considered to start from 0.0 mm and gradually increased by 0.1 mm/observation up to 0.9 mm. Figure 11 depicts that the sensor layer thickness change is inversely proportional to the resonance frequency shift. It is notable to mention that, for simplicity of shifting sequence representation data plotting was performed with 0.2 mm/observation and data extraction from the simulation was based on 0.1 mm/observation. Hence, this unit cell shows an average shifting of resonance frequency approximately 52 MHz/observation for Rogers RT 5880 sensor layer material. Similar steps have been followed for RT 5870 and RT 6202 as sensing layer materials and the results are plotted in Figure 11b. Additionally, a comparison with other sensing applications of MM absorbers is shown in Table 4. Despite using the same widely used substrate (FR-4) this unit cell absorber has a reduced size with significant absorption and a notable sensitivity to thickness changes. Comparing this unit cell with others, it would be useful for sensing applications for satellite communication and radar systems. Figure 11: Unit cell absorber for pressure sensitivity in simulation (**a**) Absorption (%) amount and Resonance frequency shift w.r. to sensor layer thickness (**b**) Sensor layer relationship with Resonance frequency. Figure 10: Simulation setup for a pressure sensor using metamaterial absorber unit cell.