# A Miniaturized Design for a Terahertz Tri-Mirror CATR with High QZ Characteristics
## 4 Conclusions  
In this paper, a design methodology for a miniaturized tri-mirror CATR system with high QZ characteristics is proposed. By employing cross-polarization cancelation conditions based on beam mode analysis theory, dynamic ray tracing based on geometric optics, shaped mirror surface reconstruction techniques, and a method of adding rolled-edge structures on the primary mirror, a miniaturized tri-mirror CATR system operating in the 100-500 GHz band is designed and numerically simulated. The system features a primary mirror with a 0.2 m diameter and two shaped mirrors with diameters of 0.06 m and 0.07 m. The overall physical structure dimensions of the miniaturized tri-mirror CATR are 0.61 m \(\times\) 0.2 m \(\times\) 0.66 m. Simulation results indicate that the cross-polarizations are less than \(-40\) dB along the major cuts of the QZ, with a co-polarization amplitude and phase ripples of 1.6 dB and \(10^{\circ}\), respectively. The CATR achieves a QZ utilization ratio of 70%, collectively demonstrating superior QZ characteristics. To further validate the correctness and effectiveness of the design methodology and simulation results, the miniaturized  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & **Upper Fre.** & **QZ Usage** & **Size of QZ** & **Size of CATR** & **Number of** & **Cross-Polar** \\  & **Limit (GHz)** & **(\%)** & **(m \(\times\) m)** & **(m \(\times\) m \(\times\) m)** & **Mirrors** & **(dB)** \\ \hline
[19] & 110 & 50 & 0.3 \(\times\) 0.3 & \(2.8\times 1.6\times 2\) & 1 & \(-29\) \\
[20] & 110 & 50 & 0.3 \(\times\) 0.3 & \(2.1\times 0  
CATR has been fabricated and experimentally tested. Measurement results indicate that at operational frequencies of 183 GHz and 275 GHz, the co-polarization amplitude ripples and phase ripples within a 0.14 m diameter QZ are within 1.8 dB and 11\({}^{\circ}\), respectively. The experimental results exhibit excellent agreement with simulations, confirming the feasibility and validity of the proposed methodology. This approach not only provides a theoretical foundation for achieving high QZ characteristics designs in CATR systems but also offers technical support for constructing a flexible, portable, and miniaturized terahertz CATR system under spatially constrained conditions. These advancements hold significant potential for both academic research and practical engineering applications.  
Conceptualization, Z.L. and Y.Y.; methodology, Z.L. and Y.Y.; software, Z.L. and H.X.; validation, Z.L., Y.Y., H.X., and D.X.; formal analysis, Z.L. and H.X.; investigation, Z.L.; resources, Z.L., Y.Y., H.X., and D.X.; data curation, Z.L.; writing--original draft preparation, Z.L.; writing--review and editing, Y.Y., H.X., and D.X.; visualization, Z.L.; supervision, Y.Y. and H.X.; project administration, Z.L. and D.X.; funding acquisition, H.X. and D.X. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
Author [PERSON] is an employee of Qilian Microwave Technology Co., Ltd. The authors declare no conflicts of interest.