1. Phased Array Radar Principles
AN/SPY - 1
Phased Array Radar Principles

2. Objectives
Understand the basic principles of electronic scanning radar
Identify advantages and disadvantages of phased array
Identify applications
Discuss methods of beam steering
Determine and calculate phase relationships between elements
Review history and specifications of AN/SPY 1

3. Basic Principles Relies on constructive interference
Point target at point P
Maximum energy on target when in phase
System may have thousands of elements

4. Basic Principle System can be used to direct beams
Phase shifting between elements
Various methods
Active and passive
Based on location of target and distance between radiating elements and target
Off boresight in elevation (greater than or less than 0 degrees) or Azimuth ( clockwise from boresight (greater than 0 degrees) or counter clockwise (less than 0 degrees))
Time delay, phase scanning, frequency scanning
Passive: Source of signal is the transmitter, Active: signal is generated at the antenna. Array of T/R modules on face of radar. Beam steering control unit (BSC) directs phase shift required to steer the beam

5. Electronic Scanning Pros and Cons
Advantages
Disadvantages
Increased data rates and reduction of system reaction time
High reliability and sidelobe control
Stealthy, low profile, and great for aircraft
Virtually instantaneous positioning of the radar beam anywhere with a set sector
Elimination of mechanical errors and failures
Increased flexibility allows for multimode operation i.e. search, track, and control in one system
High cost in comparison to traditional radar sets
Complexity
Straddle loss results in lower gain
Typically only support narrowband applications
1. Increased data rates:
a. There is a reduction of system reaction times (i.e.. don’t have to wait for
the antenna to come back around.
2. Reliability, Stealth
a. Can reduce drag on aircraft due to low profile.
2. Virtually instantaneous radar beam positioning.
a. Can change the beams and the beam axis almost instantaneously. Don’t
have to mechanically move/tilt the antenna.
b. Beam position can be changed in a matter of microseconds.
3. Elimination of mechanical errors and failures associated with mechanically scanned systems.
4. Increased flexibility:
Can develop more complex radar systems including
a. 3D Radar with only one radar
b. Multi mode operations (Search, Tracking, and Fire Control!)
Disadvantages:
5. Price driven even higher for AESA
Straddle loss results from
a. Deviating from the broadside of the antenna elemetns and results in gain degradation for both range and Doppler
b. Most significant at large scan angles
c. Can combat by increasing dwell time at off boresight axis i.e. 2T, 3T, 4T depending on angle
d. Compare with squinting in peripheral. Effective apperature lowers, therefore beamwidth grows

6. Applications Defense Weather Broadcasting In flight entertainment
AN/SPY 1 (D) Radar
Part of Aegis system developed by KU alum
Weather
National Sever Storms Laboratory Norman, OK
Broadcasting
AM Radio
In flight entertainment
Provide internet access to airliners
Multi function to handle search, track, and command functions simultaneously 
Wayne E. Meyer known as the father of Aegis was an Electrical Engineering graduate from KU in Also recipient of Distinguished Engineering Service Award in 1981
Early warning system for tornados and other dangerous weather
Simultaneously perform aircraft tracking, wind profiling, and weather surveillance with a single phased array weather radar
AM radio in order to ensure signal quality to prime listening areas
Transmitting high-speed Internet/voice data between airborne aircraft and ground stations via Ku-Band active phased array antenna or communication AESA, bringing broadband Internet access to in-flight passengers

7. Beam Steering
Adjustments to the free space propagation from various elements
Result positions interference at different locations
Implemented by altering time, frequency, or phase
Time Delay Scanning
Frequency Scanning
Phase Scanning

8. Frequency Scanning Based on frequency propagation through waveguide
At different frequencies behavior changes
Beam shifting away from boresight

9. Frequency Steering

10. Time Delay Scanning Independent of frequency
Uses time delay networks and outputs identical waveforms from each element
Periodic shifting of the waveforms producing a time delay in which the waveform generated by each element will reach the desired area

11. Phase Scanning Uses phase shifters Phase varies from 0 to 2π radians
Frequency dependent
Can calculate phase between elements

12. Phase between elements
In order to steer beam appropriately the required phase shift is needed
This can be calculated based on following equation:
ΔΦ= 2𝜋∗sin⁡(𝜀) λ where ε is the angle off bore-sight (azimuth or elevation)
Example Problem

13. AN/SPY 1
For Ticonderoga class Cruisers and Arleigh-Burke class Destroyers
Capable air defense radar
Can handle search, track, and fire control
Recently implemented in Ballistic Missle Defense
Various upgrades over its years of service
SPY-1 is the primary air search radar the Aegis Combat System. The S-band multi-function phased array radar system is designed to meet the most demanding requirements and environments. SPY-1 can automatically track multiple targets simultaneously while maintaining continuous surveillance of the sky, from the wave tops to the stratospher

14. AN/SPY 1 S-band Radar Designation SPY (Water, Radar, Surveillance)
Size: 12 ft octagon
Weight above deck (lb): 13,030 per face
Weight below deck (lb):131,584
Range (nm): 175, 45 against sea-skimming missiles
Band: S band (3.1 – 3.5 GHz)
Instantaneous bandwidth (MHz): 40
Beam (º): 1.7 x 1.7
Peak power (MW): 4 – 6
Average power (kW): 58
Gain (dB):42
Pulse compression ratio: 128:1
Sea skimming targets (reduced range mainly due to sea scatter (“clutter”)

15. Civilian conversion
National Severe Storm Laboratory in Norman, OK

16. Multi-function Phased Array Radar
1970’s repurposed Navy radar
Goal is to replace radars for
Single focus aircraft tracking
Single focus weather tracking
Why not both?

17. MPAR System Benefits 4-5 min mechanical scan reduced to under a minute
Estimated $4.8 billion in savings to the taxpayer:
$1.8 billion with single radars having multi-function capability
$3 billion in life-cycle costs projected over 30 years.
Proven to function in presence of weather and clutter
Provided a mean tornado lead-time of 20.1 minutes in real scenario
Collaborative effort through multiple schools, agencies, and corporations
In spring, 2014, engineers successfully tested aircraft detection and tracking algorithms that were robust in the presence of weather and ground clutter\
13 minute national mean tornado lead-times using current NWS radars. (8 min improvement)
NOAA NSSL and National Weather Service Radar Operations Center; the Federal Aviation Administration; Lockheed Martin, Raytheon, Northrup Grumman, Ball Aerospace, and Saab Sensis; the Department of Defense; University of Oklahoma’s School of Meteorology, School of Electrical and Computer Engineering, and Advanced Radar Research Center; Oklahoma State Regents for Higher Education; Basic Commerce and Industries; Massachusetts Institute of Technology/Lincoln Laboratory, Georgia Tech Research Institute, and the Office of the Federal Coordinator for Meteorology

18. References
Payne, Craig M. Principles of Naval Weapon Systems. Annapolis, MD: Naval Institute, Print.
Richards, Mark A., James A. Scheer, and William A. Holm. Principles of Modern Radar Basic Principles. Edison, NJ: SciTech, Print.
"AN/SPY-1." Wikipedia. Wikimedia Foundation, 22 Feb Web. 25 Apr
Fields, Glen. "Phased Array Radar At the Intersection of Military and Commercial Innovation." Microwave Journal. 14 Jan Web. 27 Apr
Phased Array Radar." NOAA National Severe Storms Laboratory. Mar Web. 27 Apr