Aerospace and Electronic Systems Magazine March 2018 - 14

Feature Article:

DOI. No. 10.1109/MAES.2018.170031

Design and Implementation of a High-Frequency
Software-Defined Radar for Coastal Ocean Applications
Khalid El-Darymli, MDA Systems, Richmond, BC, Canada
Noah Hansen, Barry Dawe, Northern Radar, St. John's, NF, Canada
Eric W. Gill, Weimin Huang, Memorial University of Newfoundland, St. John's, NF,
Canada

INTRODUCTION
In 1955, Crombie [1] identified that when an electromagnetic
wave is transmitted from a shore-based high-frequency (HF) radar, operating at 13.56 MHz, the Doppler spectrum of sea echo
yielded a resonant backscatter phenomenon known as Bragg
scattering, which results from coherent reflection of the transmitted energy by ocean surface waves (SWs) whose wavelength is
exactly half as long as the transmitted radar waves. Around 17 y
later, Barrick introduced the first- and second-order theory for
deriving the HF ocean radar cross section, paving the way for
using HF-SW radar (3-30 MHz) in remote sensing of the sea
state [2]-[4]. Since then, design and implementation of classical
HF radars have proliferated [5], with Coastal Ocean Dynamics
Applications Radar and Wellen/Wave Radar (WERA) probably
among the most popular [6], [7]. These radars use traditional,
fixed, and dedicated hardware implementations. An outcome is
that this approach limits the flexibility of these classical systems
and potentially increases their cost.
The original concept of software-defined radio (SDR) first
appeared around 30 y ago [8], but because of high cost, it has
not been available as a consumer device until recently. SDR is
a generic radio communication system in which radio frequency (RF) and other analog components that have been typically
implemented in hardware (e.g., mixer, modulator, demodulator,
and detector) are instead implemented by a means of software on
a personal computer or an embedded device through programmable signal processing, giving the radio the ability to change
its operating parameters to accommodate new features and capaAuthors' current addresses: K. El-Darymli, MDA Systems,
13800 Commerce Parkway, Richmond, BC V6V 2J3, Canada, Email: (keldarymli@mdacorporation.com). N. Hansen, B. Dawe,
Northern Radar, 25 Anderson Avenue, St. John's, NF A1B 3E4,
Canada. E. W. Gill, W. Huang, Electrical and Computer Engineering, Memorial University of Newfoundland, St. John's,
NF A1B 3X5, Canada. This work was completed when K. ElDarymli was with Northern Radar, St. John's, NF, Canada.
Manuscript received January 30, 2017, revised March 25, 2017,
June 8, 2017, and ready for publication July 4, 2017.
Review handled by D. O'Hagan.
0885/8985/18/$26.00 © 2018 IEEE
14

bilities. This implies that the architecture is inherently flexible,
such that the radio may be configured to adapt to various requirements, including waveforms, frequency bands, bandwidths, and
modes of operation, while providing a low-cost, power-efficient
solution [9], [10].
In this article, the development of a multichannel HF radar
(HF-SDR) system for coastal ocean applications by Northern Radar (NRI) is described.

SYSTEM ARCHITECTURE
In this section, the overall architecture of NRI's HF-SDR is addressed. First, a general description of the hardware is provided.
Then, the software used in the system is discussed.

HARDWARE
Figure 1 depicts the overall architecture of NRI's HF-SDR system.
Primarily, commercial off-the-shelf universal software radio peripherals (COTS-USRPs), connected to a host computer, function
as the transceiver of the system. The COTS-USRPs are equipped
with custom-made front ends for the HF band. These front ends are
equipped with the necessary filters, power amplifier (PA) for transmission, and low noise amplifiers (LNAs) for reception. To provide for long-term clock stability and to synchronize the receive
(Rx) and transmit (Tx) channels across multiple SDRs, a global

Figure 1.

Overall architecture of NRI's HF-SDR.

IEEE A&E SYSTEMS MAGAZINE

MARCH 2018

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