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

HIGH-RESOLUTION ATMOSPHERIC PROFILING USINGSIMULTANEOUS MULTIPLE RECEIVERS AND MULTIPLEFREQUENCIESTian-You Yu 1 and William O.J. Brown 21 School of Electrical and Computer Engineering, University of Oklahoma,Norman, Oklahoma 73019, USA2 Atmospheric Technology Division, National Center for Atmospheric Research,Boulder, Colorado 80307, USA1 IntroductionRange imaging (RIM) has been recently developed to improve the range resolutionof pulse radar by transmitting a set of slightly shifted frequencies [Palmer etal., 1999]. The capability of RIM for making high resolution observations of thebackscatter profile of atmospheric structures have been demonstrated by severalauthors [e.g., Palmer et al., 1999; Chilson et al., 2003]. However, no Doppler informationof these structures was shown. Therefore, one of the goals for this workis to demonstrate application of RIM to obtain high-resolution profile of radialvelocity.Furthermore, measuring horizontal wind at the same resolution as the resolutionof echo power and radial velocity in RIM is of primary interest. A newtechnique, based on a hybrid use of RIM and spaced antenna (RIM-SA), is developedto improve the range resolution of horizontal wind measurements. As aresult, RIM-SA has the potential to resolve not only fine reflectivity structures,but also fine-scale wind shears.2 Theory of RIM-SA62In order to implement RIM-SA technique, a minimum of three spatially separatedreceivers and two shifted transmitting frequencies are needed. The radar beampoints vertically for both transmitting and receiving in a RIM-SA configurationand typically, multiple frequencies are transmitted on a pulse-by-pulse basis. RIM-SA exploits the concept of RIM to generate synthesized time series at severalsubgates within one range gate for each receiver independently. A high-resolutionprofile of wind field is estimated using a SA algorithm on synthesized time seriesdata from spaced receivers at every subgate.In general, signals from M frequencies and N receivers are considered. Lets ij (t) represent the signals from the ith receiver and the jth transmitting frequencyat a given gate. In RIM, only signals from M frequencies at a given receiver i areof interest. The synthesized signals y i (r I , t) at range r I and receiver i are definedas a weighted summation of signals from M frequencies and the i receiver [Palmeret al., 1999].y i (r I , t) = w(r I ) † s i (t) (1)where the column vector s i (t) consists signals from M frequencies, the dagger is aHermitian operator, and the column vector w(r I ) represents a weighting function.The complex weighting function is designed to modulate signals from M differentfrequencies to create a constructive interference at a given range r I . In thiswork, the Capon weighting function was employed because it can provide betterresolution than the Fourier weighting function [Palmer et al., 1999].In previous work, the range brightness was estimated using the correlation matrixmade up by s i (t) (e.g., (2) in Palmer et al. [1999]); Therefore, no synthesizedsignals (1) were needed. The range brightness represents backscattered power at