# Dynamic Incidence Angle Effects of Non-Spherical Raindrops on Rain Attenuation and Scattering for Millimeter-Wave Fuzes

## TL;DR

This paper studies how the angle of raindrops affects millimeter-wave fuzes' performance in rain, showing that non-spherical raindrops at 180° cause significant signal issues.

## Contribution

The study introduces a method to analyze incidence angle effects using realistic raindrop models and identifies critical angles for performance degradation.

## Key findings

- At 180° incidence angle, attenuation coefficient increases by 45.88% compared to spherical raindrop models.
- Volume reflectivity increases by 28.27% and SCNR decreases by 27.35% under worst-case conditions at 60 GHz.
- The BC model with IIM T-matrix method reveals critical angles for MMW signal propagation in rain.

## Abstract

The dynamic variation of the incidence angle between the millimeter-wave (MMW) fuzes and non-spherical raindrops significantly affects detection performance. To address this issue, the influence of incidence angle on attenuation coefficient, volume reflectivity, and the signal-to-clutter-plus-noise ratio (SCNR) is systematically analyzed by employing the realistic raindrop morphology described by the Beard and Chuang (BC) model and the invariant imbedding (IIM) T-matrix method. By integrating worst-case analysis, the critical incidence angle corresponding to the most severe performance degradation is identified, and the corresponding attenuation coefficient, volume reflectivity, and SCNR values are reconstructed. Numerical simulations demonstrate that for the BC model, the most severe impact on MMW signal propagation occurs at an incidence angle of 180°. Under this condition, the reconstructed attenuation coefficient and volume reflectivity increase by 45.88% and 28.27%, respectively, while the SCNR decreases by 27.35% at 60 GHz operating frequency and 100 mm/h rainfall rate, compared to the spherical raindrop model. This study provides a theoretical basis for calibrating design margins and optimizing anti-interference strategies for MMW fuzes operating in complex meteorological conditions.