Tuesday, 29 August 2023
Boundary Waters (Hyatt Regency Minneapolis)
This study evaluates the performance of the improved Progressive Pulse Compression (PPC) technique, referred to as PPC+. It is a novel signal processing technique designed to mitigate the so-called “blind range” observed in pulse compression radar systems. The blind range results from using pulse compression, and it is generated by a strong leak from the transmitter into the receiver during transmission. PPC+ mitigates the blind range without requiring a fill pulse or hardware modifications. Compared to other solutions that use fill pulses, PPC+ has better sensitivity within the blind range and requires less bandwidth, making it a more cost-effective solution.
PPC+ utilizes the uncontaminated vestige of the received signal inside the blind range, pulse compressed with an optimized mismatched filter (in contrast to the original PPC). The PPC+ technique can be divided into three steps. In the first step, the contamination is subtracted from the received signal. For this end, a window (the same size as the received signal) is designed and multiplies the received signal. The window starts with as many zeroes as the number of contaminated samples in the received signal. Then, a smooth taper is applied in a small group of samples exactly after the zeroes for a continuous transition from zero to one, and the rest of the window is populated with ones. The second step is designing a mismatched filter that mitigates the limitations observed when modifying the received signal (using an amplitude modulation approach). Then the modified received signal will be pulse compressed using the mismatched filter. Finally, the third step is to calibrate the compressed signal to properly compensate for the incomplete return signal and use the mismatched filter so the proper reflectivity values can be estimated for the weather inside the old blind range.
Fig. 1 illustrates the improvements of PPC+ over the original PPC in a group of polarimetric variables calculated from IQ data gathered with PX-1000, an X-band software-defined solid-state radar system designed and operated by the Advanced Radar Research Center (ARRC) at the University of Oklahoma (OU). The IQ data was collected during a tornado event in central Oklahoma on 20 April 2023, using a plane-position indicator (PPI) scan. The tornado was located approximately 9 km away from the radar and within its blind range (~15 km, black dashed lines). Both PPC and PPC+ can accurately observe the tornado inside the blind range. However, the original PPC produces visible shoulders that cause the weather to appear smeared. This effect can be mitigated by using the mismatched filter in PPC+.
https://sooners-my.sharepoint.com/:i:/g/personal/cesar_salazar_ou_edu/EcpVIO3lqOZPm3y5FwApcxsBxrUdfGcsDMPW0AN8N2A4cQ?e=DNH8Vz
Fig. 1. Improvements of PPC+ over the original PPC in a group of polarimetric variables calculated from IQ data gathered during a tornado event in central Oklahoma on 20 April 2023. The IQ data was processed using either PPC (panels a, c, and e) or PPC+ (panels b, d, and f). The polarimetric products calculated are the radar reflectivity factor from the horizontal channel (panels a and b), the differential reflectivity (panels c and d), and the correlation coefficient (panels e and f).
To evaluate the PPC+ technique, the authors collected data from the PX-1000 radar. The radar was operated back-to-back with a long pulse (compressed using PPC+) and a short pulse (no pulse compression or blind range). The echoes inside the blind range from PPC+ are expected to provide accurate weather observations, similar to those from a short pulse but with better sensitivity due to pulse compression.
PPC+ utilizes the uncontaminated vestige of the received signal inside the blind range, pulse compressed with an optimized mismatched filter (in contrast to the original PPC). The PPC+ technique can be divided into three steps. In the first step, the contamination is subtracted from the received signal. For this end, a window (the same size as the received signal) is designed and multiplies the received signal. The window starts with as many zeroes as the number of contaminated samples in the received signal. Then, a smooth taper is applied in a small group of samples exactly after the zeroes for a continuous transition from zero to one, and the rest of the window is populated with ones. The second step is designing a mismatched filter that mitigates the limitations observed when modifying the received signal (using an amplitude modulation approach). Then the modified received signal will be pulse compressed using the mismatched filter. Finally, the third step is to calibrate the compressed signal to properly compensate for the incomplete return signal and use the mismatched filter so the proper reflectivity values can be estimated for the weather inside the old blind range.
Fig. 1 illustrates the improvements of PPC+ over the original PPC in a group of polarimetric variables calculated from IQ data gathered with PX-1000, an X-band software-defined solid-state radar system designed and operated by the Advanced Radar Research Center (ARRC) at the University of Oklahoma (OU). The IQ data was collected during a tornado event in central Oklahoma on 20 April 2023, using a plane-position indicator (PPI) scan. The tornado was located approximately 9 km away from the radar and within its blind range (~15 km, black dashed lines). Both PPC and PPC+ can accurately observe the tornado inside the blind range. However, the original PPC produces visible shoulders that cause the weather to appear smeared. This effect can be mitigated by using the mismatched filter in PPC+.
https://sooners-my.sharepoint.com/:i:/g/personal/cesar_salazar_ou_edu/EcpVIO3lqOZPm3y5FwApcxsBxrUdfGcsDMPW0AN8N2A4cQ?e=DNH8Vz
Fig. 1. Improvements of PPC+ over the original PPC in a group of polarimetric variables calculated from IQ data gathered during a tornado event in central Oklahoma on 20 April 2023. The IQ data was processed using either PPC (panels a, c, and e) or PPC+ (panels b, d, and f). The polarimetric products calculated are the radar reflectivity factor from the horizontal channel (panels a and b), the differential reflectivity (panels c and d), and the correlation coefficient (panels e and f).
To evaluate the PPC+ technique, the authors collected data from the PX-1000 radar. The radar was operated back-to-back with a long pulse (compressed using PPC+) and a short pulse (no pulse compression or blind range). The echoes inside the blind range from PPC+ are expected to provide accurate weather observations, similar to those from a short pulse but with better sensitivity due to pulse compression.
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