Proceedings with Extended Abstracts (single PDF file) - Radio ...

Meridional (deg)1050−5−10Echo Power ( dB )Capon302520ε = 7.930ε = 5.50315−10 −5 0 5 10 −10 −5 0 5 10Zonal (deg)FourierAverage SNR = 3 dBTrueReflectivityHorizontal Windθ oReceiveBeam Patternθ o ReflectivityθFigure 2. The left panel shows the images obtained after processing the signals from the simulation. The datasetsare processed with both the Fourier and Capon methods. The right panel is a graphical illustration of the effects ofreflectivity variation along the wind directions. The shaded regions show the weighting effects of radial velocities. Inthis example, the radial velocities are under and over weighted on the right and left of Ó, respectively. This weightingdepends on the reflectivity variations, the wind direction and the antenna beam pattern and contritubes a deterministicbias to the radial velocity estimates.10Reflectivity( dB )010Simulation, v r, est.( ms −1 )6410Reflectivity( dB )010Simulation, v r, est.( ms −1 )64Meridional (deg)50−5−10−5−1050−5−1020−2−4Meridional (deg)50−5−10−5−1050−5−1020−2−4−10 −5 0 5 10−15−10 −5 0 5 10−6−10 −5 0 5 10−15−10 −5 0 5 10−6Error: v r− v r, est.( ms −1 )2Reflectivity bias error( ms −1 )2Error: v r− v r, est.( ms −1 )2Reflectivity bias error( ms −1 )2Meridional (deg)1050−5−1010−11050−5−1010−1Meridional (deg)1050−5−1010−11050−5−1010−1−10 −5 0 5 10Zonal (deg)−2−10 −5 0 5 10Zonal (deg)−2−10 −5 0 5 10Zonal (deg)−2−10 −5 0 5 10Zonal (deg)−2Figure 3. These plots show the effects of reflectivity variations for two cases with different wind directions. The upperleft panel is the true reflectivity with horizontal wind as indicated. The upper right panel is the radial velocity estimate.The lower two panels show the radial velocity estimate error (left) and the predicted bias obtained using the knownwind field, the known reflectivity, and the Fourier beampattern.3. OPTIMAL SUBARRAY DESIGNA simple Gaussian reflectivity field pattern is used in this part of the experiment. The maingoal of this experiment is to address the bird clutter rejection issue; the model reflectivity isirrelevant. For the first few frames of the simulation, the bird moves through the main lobe ofthe antenna. Subsequently, the bird moves through a grating lobe. No known method is availableto eliminate the bird echo from the main lobe. However, the proposed array configurationshown in Figure 4 (left panel) can significantly reduce the effect of the bird as it progressesthrough the grating lobes. The quality of the wind field estimates using the original TEP arrayand proposed array configuration will be compared. Initially, the three subarrays were designedto allow spatial smoothing to mitigate the clutter. However, it was later discovered thatimaging using the Capon beamforming method outperformed the spatial averaging method.The results in this report show the performance of the newly configured array using the Caponbeamforming method. A statistical search was performed in order to find the optimal arrayconfiguration. Figure 4 shows the new array configuration with three hexagonal subarrays andthe array response of the system. The right panel shows the total beampattern of the systemwith nulls in the centers of each grating lobe allowing the mitigation of clutter effects.One of the main goals of the TEP system is to estimate the three-dimensional wind fieldwith high angular resolution. The proposed array configuration greatly benefits this goal byvirtually eliminating the effects of grating lobe echoes in the wind field estimates. Figure 551