DETECTION OF SMALL AIRCRAFT WITH DOPPLER WEATHER RADAR

ABSTRACT We present a method that can be performed in parallel to reflectivity estimation in weather radar and that allows one to detect small aircraft. Though small aircraft and large birds might produce comparable reflectivity signals their spectral signatures are considerably different. A small aircraft with propellers can be recognized from its spectrum via modulations produced by Doppler shifts from rotating parts. Generally such a spectrum has an elevated spectral floor compared to the spectrum of a resolution volume without an airplane. The spectral floor level is used for detection. The method is demonstrated on a clear air case observed with Doppler weather radar on March 6, 2007 at elevation 0.5°. Index Terms -frequency domain analysis, noise measurement, adaptive signal processing

Investigating EM Dipole Radiating Element for Dual Polarized Phased Array Weather Radars

Dual‐polarized antenna radiating element is a critical component in the Multi‐function Phased Array Radar (MPAR). This paper studies the dual‐polarized radiating element based on the EM dipole concept. Two different geometries, i.e., loop approximated as magnetic dipole and a printed electric dipole, are used to form a single dual‐polarized radiating element. Radiation patterns based on Ansoft HFSS (High Frequency Structural Simulator) simulation software and measurements carried out in anechoic chambers are presented. Initial array design based on these elements will also be discussed

Stabilization of the Rayleigh-Taylor Instability With Magnetic Feedback

119 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1969.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Two Methods of Ambiguity Resolution in Pulse Doppler Weather Radars

A comparison is made of the performance of a weather Doppler radar with a staggered pulse repetition time and a radar with a random (but known) phase. As a standard for this comparison, the specifications of the forthcoming next generation weather radar (NEXRAD) are used. A statistical analysis of the spectral momentestimates for the staggered scheme is developed, and a theoretical expression for the signal-to-noise ratio due to recohering-filteringrecohering for the random phase radar is obtained. Algorithms for assignment of correct ranges to pertinent spectral moments for both techniques are presented

Sensors and Systems to Enhance Aviation Safety Against Weather Hazards

Weather-related factors are among major causes of aviation hazards, passenger discomfort, poor airline schedule-keeping, and poor operating economy. A variety of new high-technology electronic sensors and systems for aviation weather are being developed and installed across the US. The aviation weather monitoring system of the future will be centered around Doppler weather radars which offer the best combination of coverage, resolution, and agility for this purpose, and are able to detect and estimate the severity of atmospheric air motion, including wind shear and turbulence, directly. Three major new Doppler radar systems are pertinent: the Next Generation Weather Radar, the Terminal Doppler Weather Radar, and the Airport Surveillance Radar with a dedicated weather channel. Other relatively simple new instruments for aviation weather support include the Low Level Wind Shear Alert System, the Doppler Wind Profilers, the Automated Weather Observation System, and the Automated Surface Observation System. These systems are designed to perform higher level functions such as detection, characterization, and hazard potential estimation of aviation-significant weather phenomena, as well as their communication and display automatically. Together with conventional information sources and data from improved satellite imagers and sounders, the modern dedicated weather surveillance systems hold the potential of being powerful tools in enhancing the quality of aviation well into the next century

Practical Algorithms For Mean Velocity Estimation In Pulse Doppler Weather Radars Using A Small Number Of Samples

Doppler weather radars with fast scanning rates must estimate spectral moments based on a small number of echo samples. This paper concerns the estimation of mean Doppler velocity in a coherent radar using a short complex time series. Specific results are presented based on 16 samples. A wide range of signal-to-noise ratios are considered, and attention is given to ease of implementation. It is shown that FFT estimators fare poorly in low SNR and/or high spectrum-width situations. Several variants of a vector pulse-pair processor are postulated and an algorithm is developed for the resolution of phase angle ambiguity. This processor is found to be better than conventional processors at very low SNR values. A feasible approximation to the maximum entropy estimator is derived as well as a technique utilizing the maximization of the periodogram. It is found that a vector pulse-pair processor operating with four lags for clear air observation and a single lag (pulse-pair mode) for storm observation may be a good way to estimate Doppler velocities over the entire gamut of weather phenomena

Electromagnetic Simulation and Alignment of Dual-Polarized Array Antennas in Multi-Mission Phased Array Radars

Electromagnetic (EM) simulation of dual-polarized antennas is necessary for precise initial alignments, calibration and performance predictions of multi-function phased array radar systems. To achieve the required flexibility and scalability, a novel Finite-Difference Time-Domain (FDTD) solution is developed for rectangular, cylindrical and non-orthogonal coordinate systems to simulate various types of array antenna manifolds. Scalable array pattern predictions and beam generations are obtained by combining the FDTD simulation solutions with the Near-Field (NF) chamber measurements. The effectiveness and accuracy of this approach are validated by comparing different simulations and comparing simulations with measurements