## 2 System Overview  
All components of our instrument were primarily designed and constructed using 3D CAD software, specifically Autodesk Fusion 360 Academic License. These components were then fabricated using a GLC-1490 laser cutter from Glorystar Laser Technology Company and a GTMax 3D Core A1 3D printer, using acrylic and ABS materials, respectively. The instrument parts were assembled with different sizes of M3 screws and nuts. Figure 1a depicts the 3D design of the instrument, while Figure 1b displays a photograph of the fully assembled instrument.  
We used a Rohde & Schwarz (R&D) ZVA-40 vector network analyzer (VNA) as a signal generator and produced a signal with a power of +15 dBm and a frequency of 30 GHz. This equipment has the capability to produce signals within the frequency range of 10 MHz to 40 GHz. The signal power varies based on frequency, with the typical signal power range for frequencies of 20 GHz to 32 GHz being \(-\)40 dBm to +15 dBm [21]. The signal was transmitted using a WR-34 horn antenna from Pasternack, which has a nominal gain of 20 dBi and a 17\({}^{\circ}\) (17.4\({}^{\circ}\)) vertical (horizontal) half-power beamwidth (HPBW) [22]. A schematic representation of the system overview utilized to characterize metasurfaces using the instrument described in Figure 1 is shown in Figure 2.  
After being transmitted by the metasurface, the signal is received by a helical antenna [23]. This type of antenna was selected for the prototype due to its ease of design and fabrication and its reduced dimensions, which allow for a higher spatial resolution. Figure 3 presents the design specifications for the helical antenna used in this research.  
Figure 1: _Cont._  
Figure 1: (**a**) The three-dimensional design of the instrument created in Autodesk Fusion 360 Academic License. (**b**) A photograph of the assembled instrument and its components.  
Figure 3: Helical Antenna Design. The helical antenna was fabricated with a copper wire and welded in a SMA connector base. This antenna was designed to operate at a frequency of 30 GHz. It consists of four turns, measuring one wavelength in length, with a spacing of one-quarter wavelength between the turns. The diameter of the helices measures 3.18 mm.  
Figure 2: Entire system overview, with the representation of all main components. The VNA ZVA40 works as a 30 GHz signal generator, connected with the WR-34 horn antenna emitting the signal. The signal generated and emitted passes through the metasurface, interacting with the manufactured structures, and reaching the helical antenna installed in the instrument. The received signal is then processed, and the intensity in XYZ is stored for later analysis.  
The fabricated antenna was designed to have low return loss at 30 GHz, with a length equal to the operating wavelength (10 mm), an inter-helix spacing (S) equal to \(\lambda\)/4, and a diameter (D) of 3.18 mm, as shown in Figure 3. A photo of the antenna can be seen in the inset of Figure 4a. Figure 4a shows the measured return loss of the antenna as a function of the operating frequency obtained with the VNA. Note that the return loss minimum actually occurred at a slightly higher frequency of 30.88 GHz, as shown by Figure 4b. This is probably due to small deviations in the fabricated antenna length.