Aerospace and Electronic Systems Magazine September 2017 - 40

Feature Article:

DOI. No. 10.1109/MAES.2017.160243

Expert System CFAR: Algorithm Development,
Experimental Demonstration, and Transition to
Airborne Radar Systems
Michael C. Wicks, University of Dayton, Dayton, OH, USA
William J. Baldygo, US Air Force Research Laboratory, Wright Patterson Air Force
Base, OH, USA

INTRODUCTION
The genesis of the Expert System Constant False Alarm Rate (CFAR) processing arose in 1984 from insight gained
during earlier experiments performed
at the Air Force Research Laboratory's
Rome Research Site, then known as
Rome Air Development Center (RADC)
(Figure 1). Measured data analysis from
the low altitude detection (LAD) experiments conducted in RADC's Surveillance
Laboratory was instrumental in gaining
insight into detecting weak signals (airborne target returns) embedded in strong
nonhomogeneous clutter. This challenging problem, investigated by Signal ProFigure 1.
cessing Chief, Mr. Clarence Silfer in the US Air Force ground-based radar test bed in Rome, NY.
late 1970s, was studied to improve cruise
timing, and control implemented via programmable emitter coumissile detection by unattended short-range ground-based radars.
pled logic) operated with up to 60 MHz of signal bandwidth at
The LAD experiments were performed in support of the Enhanced
L-Band, employing a 150 KW traveling wave tube for the final
Defense Early Warning (EDEW) project [1]. Dr. Russell Brown and
stage of high-power amplification on transmit and superheteroMr. David Mokry conducted measurements in the summer of 1981,
dyne down conversion on receive. This type of radio receiver
and Mr. Paul van Etten performed analysis. The first author assisted
uses stages of frequency mixing, amplification, and filtering to
in these early endeavors, focusing on data analysis.
convert a microwave signal of interest to a fixed intermediate
A track-while-scan (TWS) instrumentation radar was used
frequency (IF). The resulting IF signal, a fully coherent yet frefor data collection. This coherent radar (waveform generation,
quency-shifted replica of the received microwave signal, is more
conveniently down-converted to baseband, digitized, processed,
Authors' addresses: M. C. Wicks, Dept. of Electrical and
and/or recorded.
Computer Engineering, University of Dayton, 341 Kettering Laboratory, 300 College Park, Dayton, OH 45469. E-mail:
This L-Band instrumentation radar, integrated in 1981 with
(mwicks1@udayton.edu). W. J. Baldygo, US Air Force Research
an AMPEX Corp HBR-3000 digital data recorder and interfaced
Laboratory, 2241 Avionics Circle, Wright Patterson Air Force
via a buffer memory to a Floating Point Systems AP-120B array
Base, OH 45433-7320.
processor, was under the control of a Hewlett-Packard HP 1000
Public Approval: Approved for Public Release, Case Number
L-Series computer. This made data collection, quick-look calibraRY-16-0671.
tion, and in-depth postmission signal and data processing possible.
Manuscript received November 2, 2016, revised December 21,
An embedded four-channel sidelobe canceller was instrumental in
2016, and ready for publication December 27, 2016.
mitigating in-band sidelobe interference in the LAD radar data colReview handled by W. Walsh.
lection experiments.
0885/8985/17/$26.00 © 2017 IEEE
40

IEEE A&E SYSTEMS MAGAZINE

SEPTEMBER 2017

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine September 2017