## 3 Measurements and Results  
To obtain the measured range profile, a millimeter-wave FMCW radar made by TI Co., Ltd. was used. An FMCW radar is an ideal choice for short and medium-range applications, being low-cost and easy to use. The AWR1243 radar we used operates at 77 GHz. For our case, the most important factor was range resolution, which is affected by the bandwidth swept by the chirp and the sampling rate. A better range resolution can differentiate between two targets at a smaller distance but also shortens the range in view for the radar because of the limited sampling rate. A range resolution of 5.02 cm and a range of 6.4 m were obtained using the following parameters: operating frequency of 77 GHz, bandwidth swept by 2987 MHz, A/D sampling rate of 3 MHz, chirp rate of 70.006 MHz/us, 128 chirps per frame, and 24 frames per burst.  
The five different stages of enclosed printer paper quantity are shown in Table 1. For each stage, the target box was placed at the same spot to avoid any discrepancies from changing the target location and orientation. The target box's front end was 3 m from the radar for each stage. The distance between the two ends of the box, 56 cm, was confirmed by the distance between the two peaks in the range profile. Each stage of the box was entirely filled with crumpled paper. The increasing density of paper per stage was achieved by crumpling the papers into smaller wads. Figure 3 shows the placement of the box in front of the radar, and Figure 4 shows a top view of the five different stages of paper density.  
After the target box was placed, the mmWave Studio provided by TI Co. Ltd (Dallas, TX, USA). was used to input the discussed parameters to obtain the radar data. As all data were captured for every stage, the data were then processed in MATLAB to obtain each range profile. Zero-padding was used in the FFT process to obtain a detailed range profile.  
Figure 4: Visual of the five different stages of paper quantity; (**a**) Stage I, (**b**) Stage II, (**c**) Stage III, (**d**) Stage IV, and (**e**) Stage V.  
Figure 3: (**a**) The measurement setting with radar and (**b**) an empty box.  
The resulting plot formulates the two peaks of reflection magnitudes required to obtain an attenuation ratio, which is obtained by comparing the magnitudes of the two peaks. The magnitude of the first peak is roughly in the same range for all stages, but we are only focusing on the attenuation for the two peaks because the second peak will be affected by the paper density of the box. Figure 5 presents the results obtained for the empty box as well as the five stages.  
The empty stage, presented in Figure 5a, shows both reflection magnitudes roughly equal to each other because the attenuation of the electromagnetic wave inside the box is negligible. The only effect of power dissipation occurs from the two thin layers of the cardboard box, which introduce complex permittivity. Each of the following five stages shows power dissipation with increased paper quantity. Stage V was packed with the highest amount of paper for almost 100% power dissipation, with the second peak absent. Table 2 shows the attenuation ratio between the two peaks for every stage. It is noted that adding permittivity in between shifts the second peak due to the different propagation time delay. However, the amount is so small that we could not observe it in our experiments.  
The results obtained for measurements and calculations were close for most stages. Differences in attenuation might result from the general makeup of the material, including factors relating to humidity and the specific species of wood used, which produce unique degrees of permittivity and conductivity. However, both datasets agree in demonstrating the concept of material classification based on power dissipation as a result of the material makeup, with similar trends in attenuation.