Robert Palumbo , Eric Knapp, Ken Wood, David McLaughlin

Deployment Considerations and Hardware Technologies for Realizing

X-Band Radar Networks

28 June 2012

Acknowledge

P. Keith Kelly

First RF Corporation, Boulder, CO, USA

Chris McCarroll

Raytheon Company, Andover, MA, USA

Apoorva Bajaj

UMass, Amherst, USA

NSF Engineering Research Centers Program

Outline

� CASA Overview– Why radar networks?

� Network Performance Considerations� Why Phased Arrays?� Latest Hardware Technology Development:

– CASA Phase-Tilt Weather Radar System

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Weather

hazards

gap

Collaborative Adaptive Sensing of the Atmosphere (C ASA)Engineering Research Center

DataNumerous

inexpensive,

closely-spaced

radarsMultipleend users

Tasking

Solution

Observe, understand, predict and respond to hazardo us weather events

Some theoretical numbers Assumes regular grid 230km (S), 150km (C), 30 km (X )

“Blanket Coverage” 15% Coverage*

Large Radar (S/C-

Bands)

Small Radar

(X-Band)

Small Radar

(X-Band)

4

*Critical infrastructure, population centers, borders, etc…

USA / CONUS 145 8,511 1,277

Europe / OPERA 217 5,416 812

France 28 712 107

UK 11 270 41

Belgium 2 42 6

Large numbers of small radars –must be inexpensive, easy to deploy

X-Band Weather Radar TechnologiesDeployed Over Past Decade

Performance

(Resolution, Doppler,

Dual-pol, Sensitivity,

Clutter rejection)

5

Clutter rejection)

Size, Weight, Cost, Complexity

Fan beam/ Magnetron

Pencil beam/Magnetron

Coherent, dual-pol pencil beam on 2 axis pedestal

Radar nodes must be a balance between Size/Weight/Cost and Performance

Performance Considerations for X-Band Radar Networks

� Need to establish a performance baseline for X-Band radar systems to be realized in a network:– These numbers are derived from the validated performance of the CASA IP1

radar network

AttributeTop-Level System

RequirementDerived Requirement

Low Profile 1m2 X-Band (9.3 – 9.5 GHz); < 200lb

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Low Profile 1m X-Band (9.3 – 9.5 GHz); < 200lb

Scan Volume100m to 10’s of km

altitude

Azimuth: 360°

Elevation: ~0° to 60°

Range ~ 30km

Radar Sensitivity < 10dBZ at 30km 100W (w/ Pulse Compression)

Spatial Resolution

< 1.3km at 30km 2° x 2° antenna beamwidths

Dual Polarization Bias in Zdr < 0.2dBAlternate T/R (ATAR): ICPR > 20dB

Simultaneous T/R (STSR): ICPR > 40dB

Phased Array Radars have the capability to meet these performance baselines

Why Dense Networks of Phased Arrays

1. Capability of Low Level Situational Awareness– “Mind the Gap”

2. Ease of Installation– Easily installed on the sides of buildings, existing infrastructure– Low weight / low power, no large pedestals requiring dedicated land

3. Low maintenance cost– No moving parts– No moving parts

4. Enhanced reliability– Solid state, active arrays over magnetron/klystron systems

5. Multi-Mode Operation– Can support multiple missions simultaneously

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Phased Array Radars as the Next Generation Technology

� CASA has successfully demonstrated the feasibility of a phase-tilt antenna as a low-cost technology for future weather radars– University of Massachusetts’ research prototype shown

below, parts cost ~$50K (US) per antenna– Demonstrated better than 20dB cross-pol over +/- 45°

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Phase-Tilt Weather Radar� CASA Phase-tilt antenna concept

developed as a commercialized product by First RF Corp., Colorado, USA

� Radar backend (software and transceiver) developed at UMass Amherst

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Performance SpecificationsParameter

Units

PTWR

Frequency Range GHz 9.3 – 9.5

Transmit Power (Peak) W 70

Pulse Length µS .6 - 60

Pulse Compression Gain dB Up to 20

Duty Cycle (max) 30%

Unambiguous range @ max PRF km 31Unambiguous Velocity @ single

Table 1: Phase-Tilt Weather Radar system parameters.

30

35

40Phase-Tilt Weather Radar - Integrated Cross Pol. Ratio

HV

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Unambiguous Velocity @ single PRF

m/s up to 38

Unambiguous Velocity @ Dual PRF

m/s 57 @ (2:3)

Sensitivity @ 30km (@Boresight) dBZ 16

Elevation Beamwidth deg 2.8

Azimuth Beamwidth deg 1.8 -2.4

Polarization Mode Alternating

Integrated Cross Pol Ratio (max) dB -20

Power Consumption600W (average)

-40 -30 -20 -10 0 10 20 30 4015

20

25

30

Azimuth (deg, rel. to boresight)IC

PR

(d

B)

Goal: ICPR > 20dB (Met)

Phase-Tilt Weather Radar meets key performance needs

Effect of Scan Loss on Radar Sensitivity� Scan loss in a phased array degrades radar sensitivity off boresight:

– At Boresight: 16dBZ at 30km– At +/- 45°: 19.5dBZ at 30km

� Sensitivity is enhanced through X-Band network sign al processing

19.5

20Phase-Tilt Weather Radar Minimum Detectable Signal vs. Scan Angle

15

20

X: 30.06

Phase-Tilt Weather Radar Minimum Detectable Reflectivity (@Boresight)

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-45 -35 -25 -15 -5 5 15 25 35 4515.5

16

16.5

17

17.5

18

18.5

19

19.5

Azimuth Pointing Angle (deg, rel. to boresight)

Ze,

min

(dB

Z)

0 5 10 15 20 25 30 35-20

-15

-10

-5

0

5

10

15X: 30.06Y: 15.85

Range (km)

Ze,

min

(dB

Z)

X: 15.61Y: 10.16

*Assuming 40usec, 3MHz LFM Chirp

Performance ComparisonEvent on May 30, 2012 – Amherst, MA

PTWR

23:26:23

23:26:16

UMass “MA1”

23:26:16

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23:26:23

23:22:47

NEXRAD

23:26:16*No attenuation correction

Performance Comparison (movie)Event on May 30, 2012 – Amherst, MA

1/16/2013 13No moving parts were used in the making of this video!

Conclusion

� X-Band Radar networks fulfill a critical need in many government and municipality weather applications– However, development of these networks will only happen if the initial and

recurring costs of the technology is low– Phase-Tilt technology represents a key step towards driving down the

recurring cost of such networks without sacrificing performance

� Have successfully demonstrated the realization of a commercial-grade phase-tilt radar system– Continuing to collect data and study effects of phased array technology on

weather products

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Questions?

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Backup

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Performance Specifications

ParameterUnit

sPTWR

Frequency Range GHz 9.3 – 9.5

Transmit Power (Peak) W 70

Pulse Length µS .6 - 60

Pulse Compression Gain dB Up to 20

Duty Cycle (max) 30%

Unambiguous range @ max PRF km 31

Low transmit power supports the feasibility of

switches capable of supporting Integrated Cross

Pol Ratio requirements

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Unambiguous Velocity @ single PRF

m/s up to 38

Unambiguous Velocity @ Dual PRF

m/s 57 @ (2:3)

Sensitivity @ 30km dBZ 16

Elevation Beamwidth deg 2.8

Azimuth Beamwidth deg 1.8 -2.4

Polarization Mode Alternating

Integrated Cross Pol Ratio (max) dB -20

Power Consumption600W (average)

Pol Ratio requirements