Jong-Gil Lee

Bias errors of pulse pair estimation in a weather radar

High resolution wind speed profile measurements are needed in a weather radar to provide reliable information of rapidly changing weather conditions. The commonly used pulse pair method is quite attractive when processing an enormous amount of weather radar data in real time since it is considered the fastest algorithm available. The pulse pair estimator calculates the first two moments of the Doppler spectrum from estimates of the complex autocorrelation function at lag T/sub s/. The goodness of this estimator is typically determined by examination of the bias and the variance of the moment estimates. To analyze the bias in the pulse pair estimates, we consider the process autocorrelation function R(T/sub s/) expressed in terms of the true mean Doppler frequency f/sub d/. Unbiasedness of pulse pair estimates is based on the assumption that the spectrum is symmetric or narrow. However, the weather return Doppler spectrum is often broad and not symmetric thus causing a bias. This bias effect is analyzed here using a skewed Gaussian spectrum model with various spectrum widths.

Clutter cancellation in a weather radar using an adaptive array antenna

High resolution windspeed profile measurements are needed in a weather radar to provide the reliable information of rapidly changing weather conditions. The commonly used pulse pair method is quite attractive when processing an enormous amount of weather radar data in real time since it is considered the fastest algorithm available[1] [2] [3] [4]. However, it is necessary to remove both stationary and moving clutter to obtain the accurate pulse pair estimates. The use of the conventional pulse pair canceller or other high-pass Doppler filters may be effective for the removal of ground clutter but the moving clutter occurring from airplanes, vehicles or turbulent sea surfaces cannot be eliminated. To make matters worse, even the removal of stationary ground clutter is not an easy task because of Doppler spectrum spread due to antenna rotation and phase noise.

Poly-pulse pair estimation in a Doppler weather radar

Accurate wind speed profile measurements are needed in a weather radar to provide reliable information of rapidly changing weather conditions. The commonly used pulse pair method calculates the first two moments of the Doppler spectrum from estimates of the complex autocorrelation function. Unbiasedness of pulse pair estimates is based on the assumption that a spectrum is symmetric or very narrow. However, it was shown in Lee (1999) that these bias errors can be very serious since the weather spectrum is often broad and not symmetric. Therefore, the poly-pulse pair method is analyzed in this paper to reduce these bias errors using a skewed Gaussian spectrum model with various spectrum widths.