BEAMMULTIPLEXING PHASEDARRAY WEATHER RADAR PAR

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BEAM-MULTIPLEXING PHASED-ARRAY WEATHER RADAR
(PAR)

• MARKO ORESCANIN
• UNIVERSITY OF OKLAHOMA
• ELECTRICAL AND COMPUTER ENGINEERING

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SOMETHING ABOUT THE AUTHOR

• Graduate Research Assistant at University of
  Oklahoma, working toward master of science degree
  under guidance of Dr.Tian-You, Yu
• Graduate of the University of Belgrade, School
  of Electrical and Computer Engineering, Belgrade
  ,Serbia

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Acknowledgements

• I would like to thank the people from the NSSL
  Laboratory especially Dr.Dusan Zrnic and his
  group in particular Christopher Curtis, Igor Ivic
  and Dr. Sebastian Torres for their help and
  advices.

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CONVENTIONAL VERSUS ELECTRONIC
CONVENTIONAL
PAR
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Comparison

• WSR-88D
• Dish antenna
• Reflector diameter 28.02 feet
• AZ/El Nominal Beamwidth 1.0o
• Mechanical limits -1.0o to 60o in Elevation
• Dual Polarization
• PRFs 320Hz to 1300Hz
• Pulsewidth1.57µs,4.51µs

• PAR
• Phased-Array antenna (4352 element)
• 12 foot aperture, mounted with 10o tiltback
• AZ/El Nominal Beamwidth 1.6o(2.3o at 45o off
  broadside)
• Linear Vertical Polarization
• PRFs318Hz to 1304Hz
• Pulsewidth1.57µs,4.71µs

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BEAM-MULTIPLEXING

• In a beam-multiplexing regions of interest are
  re-sampled after weather signals become
  uncorrelated
• As a result, the statistical error of spectral
  moment estimation can be reduced optimally
  through the average of a number of independent
  measurements.

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INDEPENDENT SAMPLES

• Idea behind Beam-Multiplexing is finding a way
  to collect independent samples
• Gaussian Power Spectrum - correlation coefficient
  is given by (Doviak and Zrnic 1993)
• Correlation coefficient depends on the spectrum
  width, time between samples and wave length

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VARIANCE OF ESTIMATORS

• Power for Contiguous Pairs
• Power for Independent Pairs

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VARIANCE OF ESTIMATORS

• Velocity
• for TTs contiguous pairs case otherwise
  independent pairs case

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SPECIAL CASE

• 20 dB SNR level
• 1 dB standard deviation limit for reflectivity
• 1 ms-1 standard deviation limit for velocity

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IMPLEMENTING BEAM-MULTIPLEXING

• In order to implement beam-multiplexing three
  constraints were taken into account
• FOR SMALL SPECTRUM WIDTH OF 1ms-1 AND PRT1ms
  DECORRELATION TIME IS 20 ms
• 6o ANGULAR POSITION SEPARATION BETWEEN TWO
  SUBSEQUENT BEAM POSITIONS IN ORDER TO AVOID
  SECOND AND THIRD WAY ECHOES (CHRISTOPHER CURTIS
  2002)
• PAIR OF PULSES ARE TRANSMITTED AT EACH POINTING
  POSITION,WITH SPECIFIED PRT BETWEEN THE PULSES

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SCANING CELL PATTERN
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2
9
11
5
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1
3
12
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10
4
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EXPERIMENT

• SETUP
• PRT 1ms
• Sampling 2.5 MHz
• Pulsewidth 1.57µs
• Trans. freq.3.2 GHz

• SCANING STRATEGY
• Sector of 28o was repeatedly scanned using two
  subsequent strategies
• First strategy consisted of two
  beam-multiplexing cells with 1o separation
  between positions that formed a 28o scan
• Second strategy mimics continuous sampling, with
  fixed beam positions in space separated by 1o
  covering a 28o scan

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DEMONSTRATION OF SCANING STRATEGIES
BEAM MULTIPLEXING
CONVENTIONAL
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PPI REFLECTIVITY
BEAM MULTIPLEXING
CONVENTIONAL
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PPI VELOCITY
BEAM MULTIPLEXING
CONVENTIONAL
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RESULTS
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RESULTS
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WHITENING

• Number of independent samples from data
  oversampled in range can be increased by range
  time decorelation of data.
• Data can be decorrelated in range time with the
  help of whitening technique

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Correlation in range
Estimates from adjacent range bins can be
averaged
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(No Transcript)
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DIAGRAM
Time series data
Decorelated time series data
Whitening Matrix
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Whitening Matrix
Whitening matrix is
It has been shown that if C is positive
semidefinite, symmetric matrix then if time
series data are multiplied with white matrix
product will give time series data with samples
uncorrelated in range
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If we use matrix notation the correlation matrix
is given as
We decompose this matrix
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PRELIMINERY RESULTS
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Reference

• Doviak, R. J., and D. S. Zrnic, 1993 Doppler
  radar and weather observations. 2nd ed. Academic
  Press, Inc., 562 pp.
• Ivic, I.,2001Master Thesis Demonstration of
  Efficient Method for Estimating Spectral Moments.
• Christopher Curtis,2002 National Weather Radar
  Testbed