Abstract
We carried out radar cross-section (RSC) measurements of ice particles in a microwave anechoic chamber at Nanjing University of Information Science and Technology. We used microwave similarity theory to enlarge the size of particle from the micrometer to millimeter scale and to reduce the testing frequency from 94 GHz to 10 GHz. The microwave similarity theory was validated using the method of moments for single metal sphere, single dielectric sphere, and spherical and non-spherical dielectric particle swarms. The differences between the retrieved and theoretical results at 94 GHz were 0.016117%, 0.0023029%, 0.027627%, and 0.0046053%, respectively. We proposed a device that can measure the RCS of ice particles in the chamber based on the S21 parameter obtained from vector network analyzer. On the basis of the measured S21 parameter of the calibration material (metal plates) and their corresponding theoretical RCS values, the RCS values of a spherical Teflon particle swarm and cuboid candle particle swarm was retrieved at 10 GHz. In this case, the differences between the retrieved and theoretical results were 12.72% and 24.49% for the Teflon particle swarm and cuboid candle swarm, respectively.
Highlights
Cirrus clouds, which are globally distributed, reflect or scatter short-wave radiation of the sun while absorbing the long-wave radiation from the atmosphere and the earth’s surface
The measured S21 parameters of the vector network analyzer were converted to RCS values by means of calibrators, and RCS values of particles at 10 GHz can be further retrieved to RCS values of particles at 94GHz
Ice particles used to model cirrus clouds can be increased to the centimeter scale
Summary
Cirrus clouds, which are globally distributed, reflect or scatter short-wave radiation of the sun while absorbing the long-wave radiation from the atmosphere and the earth’s surface. There are a variety of numerical algorithms to calculate the scattering properties of non-spherical particles: for example, T-matrix,[4] the finite-difference time domain,[5] the discrete dipole approximation,[6] finite element methods,[7] and the method of moments.[8] using these methods, it is not possible to determine the scattering properties of irregular-shaped particles, which can not be described by mathematical language To overcome this limitation, experimental techniques for measuring scattering properties of irregular-shaped particles have been proposed: for example, the microwave analog light-scattering facility at the University of Florida, which can. The measured S21 parameters of the vector network analyzer were converted to RCS values by means of calibrators, and RCS values of particles at 10 GHz can be further retrieved to RCS values of particles at 94GHz
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