Antenna impedance in a reentry environment

Abstract

In-flight measurements of the impedance of Cand S-band waveguides radiating into a reentry plasma are compared with computed data. The vehicle utilized for the experiment was the Trailblazer II. The measurements were made during the reentry portion of the flight and received by X-band telemetry.The computed data are obtained from the variational formulation for aperture admittance of waveguides radiating into an inhomogeneous plasma medium. The dominant TElo mode is assumed to exist over the aperture. The form employed here utilizes the piecewise solution of Riccatti equations which permits rapid evaluation of the resulting equation for the admittance.

A Low SNR Signal-Sensing Method Based on a Multiple-Antenna Covariance Matrix

“…Compute the variables of T 1 (N s ), T 2 (N s ) (or T 3 (N s ), T 4 (N s ) for multiple antennae). (6) Step 6…”

“…Moreover, the fluctuation of the electron density will lead to a significant level of signal uncertainty. To evaluate the attenuation of the signal, conventional methods usually use microwave diagnostics, including microwave reflectometry [2][3][4][5], antenna impedance [6][7][8], and/or transmission coefficient [9] diagnostics. These methods are based on reflection and/or transmission coefficients measurements.…”