DOI: 10.57760/sciencedb.space.00550
title: A CNC-machined WR-2.2 Band Orthogonal Mode Transducer for a Radiometer
title: A CNC-machined WR-2.2 Band Orthogonal Mode Transducer for a Radiometer

description: This paper presents a WR-2.2 band waveguide orthogonal mode transducer (OMT) for an ice cloud remote sensing radiometer. A holistic approach is proposed to the design and manufacturing. Given the difficulties of using computer numerically controlled (CNC) milling techniques to fabricate the OMT and its assembly, both the design and fabrication processes are optimized to reduce the possibility of error, which could affect OMT performance. In the design, the OMT utilizes a side-arm structure, with a compact 90° waveguide twist designed in the side-arm path to reduce insertion loss and achieve two symmetric and opposing output ports in the radiometer. Regarding the challenges in CNC milling technology for such high frequencies, a comprehensive sensitivity analysis is performed following the OMT design to identify the design parameters with high sensitivity. Then, an acceptable tolerance range for CNC milling is obtained. To control fabrication uncertainty and minimize tolerance, an effective fabrication refinement strategy is proposed for accessible CNC machining, reducing the range of fabrication errors to −3 μm to 2 μm within 3 iterations. Comprehensive measurements and analyses are performed on the fabricated OMT as well as the one with an antenna and a receiver. The measured insertion losses of the H and V copolarization of the OMT are better than 1.4 dB and 2 dB, respectively. The isolation is better than 40 dB. The measured H and V cross-polarizations are better than 25 dB. They demonstrate the OMT with a good performance for radiometer system.
description: This paper presents a WR-2.2 band waveguide orthogonal mode transducer (OMT) for an ice cloud remote sensing radiometer. A holistic approach is proposed to the design and manufacturing. Given the difficulties of using computer numerically controlled (CNC) milling techniques to fabricate the OMT and its assembly, both the design and fabrication processes are optimized to reduce the possibility of error, which could affect OMT performance. In the design, the OMT utilizes a side-arm structure, with a compact 90° waveguide twist designed in the side-arm path to reduce insertion loss and achieve two symmetric and opposing output ports in the radiometer. Regarding the challenges in CNC milling technology for such high frequencies, a comprehensive sensitivity analysis is performed following the OMT design to identify the design parameters with high sensitivity. Then, an acceptable tolerance range for CNC milling is obtained. To control fabrication uncertainty and minimize tolerance, an effective fabrication refinement strategy is proposed for accessible CNC machining, reducing the range of fabrication errors to −3 μm to 2 μm within 3 iterations. Comprehensive measurements and analyses are performed on the fabricated OMT as well as the one with an antenna and a receiver. The measured insertion losses of the H and V copolarization of the OMT are better than 1.4 dB and 2 dB, respectively. The isolation is better than 40 dB. The measured H and V cross-polarizations are better than 25 dB. They demonstrate the OMT with a good performance for radiometer system.