# A Miniaturized Design for a Terahertz Tri-Mirror CATR with High QZ Characteristics
## 3 Simulation and Measurement Results
To verify this inference and accurately evaluate \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Cross-Polar of** & **Simulation or** & **Co-Pol Amp.** & **Co-Polar Pha.** & **Cross-Polar** \\
**Feed (dB)** & **Measurement** & **(dB)** & **(\({}^{\circ}\))** & **Amp. (dB)** \\ \hline \(-50\) & Simulation & 1.36 & 7.45 & \(-44.52\) \\ \(-29\) & Measurement & 1.64 & 10.1 & \(-25.30\) \\ \(-29\) & Re-simulation & 1.40 & 8.30 & \(-28.10\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The QZ characteristics of the developed miniaturized tri-mirror CATR at 183 GHz when fed by feeds with different cross-polarization characteristics. Figure 13: The experimental far-field pattern of the corrugated horn feed with a center operating frequency of 183 GHz. the cross-polarization performance of the designed CATR system, the measured radiation pattern data of the corrugated horn feed with the center operating frequency of 183 GHz, shown in Figure 13, were substituted for the data of the ideal Gaussian feed pattern used in the previous simulations. The designed tri-mirror CATR system was then re-simulated at 183 GHz, and the newly obtained simulation results were compared with the system's measured results to validate the correctness of the above inference. Figure 14 shows the simulated and measured QZ field distribution curves of the system when fed by the corrugated horn feed with a center operating frequency of 183 GHz. According to the simulation results in Figure 14, when the CATR system is fed by the corrugated horn with a center operating frequency of 183 GHz, the simulated QZ co-polarization amplitude and phase ripples are 1.4 dB and 8.3\({}^{\circ}\), respectively, with a cross-polarization amplitude of \(-\)28.1 dB. The measured results show corresponding values of 1.64 dB, 10.1\({}^{\circ}\), and \(-\)25.3 dB, demonstrating excellent agreement between the simulation results and the measured results. Furthermore, comparing the simulated QZ characteristics using the corrugated horn feed (cross-polarization amplitude: \(-\)29 dB) in Figure 14 with that using the ideal Gaussian feed (cross-polarization amplitude \(<-\)50 dB) in Figure 4b reveals that the system's other QZ characteristics metrics (e.g., amplitude/phase uniformity) remain essentially consistent, except for the significant deviation in cross-polarization. This confirms that the elevated cross-polarization levels in the measured results are directly attributable to the inherent higher cross-polarization of the corrugated horn feed. Table 4 summarizes the simulated QZ results with the ideal Gaussian feed (cross-polarization amplitude \(<-\)50 dB), the measured QZ results with the corrugated horn feed (cross  
Figure 14: The simulated and measured QZ field distribution curves of the system when fed by the corrugated horn feed with a center operating frequency of 183 GHz: (**a**) the co-polarization amplitude of the QZ field; (**b**) the cross-polarization amplitude of the QZ field; (**c**) the co-polarization phase of the QZ field. polarization amplitude: \(-29\) dB), and the re-simulated QZ results using the corrugated horn's measured pattern (cross-polarization amplitude: \(-29\) dB) at 183 GHz. According to the experimental results in Table 4, when the system is fed by feeds with identical taper profiles but different cross-polarization characteristics, the co-polarization amplitude and phase in the QZ remain consistent in the above three different cases. Minor deviations (<0.3 dB/2.6\({}^{\circ}\) in co-polarization) between re-simulation and measurement arise from un-modeled test-environment effects (e.g., stray waves and calibration uncertainties). Regarding cross-polarization, the measured QZ cross-polarization amplitude of the designed CATR system deviates significantly from the simulated results obtained with the ideal Gaussian feed (cross-polarization amplitude: \(<-50\)).