Aerospace and Electronic Systems Magazine December 2017 - 32

Feature Article:

DOI. No. 10.1109/MAES.2017.170013

Spectrum Utilization: Sense and Adapt: Operation on a
Noninterference and Nonprotected Basis
Rick McKerracher, Raytheon Canada Limited
Peter Moo, Defence R&D Canada
Tony Ponsford, Maerospace Corporation

INTRODUCTION
The objective of this article is to outline the sense-and-adapt capabilities of Canada's Third-Generation High Frequency Surface
Wave Radar (3rd Gen HFSWR). This system is an evolution of
Raytheon's pioneering SWR503 radar.
HF radars depend on the detection of scattered radio waves and
are therefore vulnerable to attack by both intentional and unintentional jammers. A couple of defenses have been incorporated into
the 3rd Gen System to counter jamming. First, the system uses an
active spectrum monitoring system, whereby the radar scans the
background radio spectrum and chooses to operate in frequency
channels where it does not detect another HF user. In this manner,
the system will automatically respond to an in-channel jammer by
changing carrier frequency. However, even in the absence of jammers, the radar can be set to change carriers at periodic intervals to
help evade detection by jammers as well as minimizing impact on
other HF band users.
The 3rd Gen system, previously described in [1], was developed
based on Software Definable and Cognitive Radar principles such
as sense-and-adapt. This capability is made available by incorporating digital waveform generation and reception. The system is a
mono-static pulse Doppler radar. The radar site consists of colocated transmit and receive sites. The radar electronics are based on a
software radar design concept and utilizes direct conversion receiver-exciter technology that eliminates much of the analog hardware
associated with traditional radar. The 3rd Gen radar incorporates
an ultra linear HF power amplifier specifically designed for pulsed
operation. The HF power amplifier design results in very low spectral side-lobe levels and consequently minimal spectral leakage that
otherwise would result in adjacent channel interference.
The radar operates simultaneously on two independent frequencies in an interleaved pulse mode. The data collected on each
frequency thread is processed in multiple parallel paths optimized
Authors' address: Raytheon Canada Limited, Engineering, 440
Phillip St., Waterloo, Ontario, N2L 6R7 Canada, E-mail: (am.
ponsford@gmail.com).
Manuscript received January 6, 2017, revised May 4, 2017, and
ready for publication June 19, 2017.
Review handled by D. O'Hagan.
0885/8985/17/$26.00 © 2017 Crown
30

for different categories of vessels. The data from the two frequencies and multiple processing paths are consolidated prior to the
input of the multitarget tracker.
There is no portion of the 3-30 MHz spectrum allocated to radiolocation as a primary service. Therefore, HFSWR's must operate on a Noninterference and Nonprotected Basis (NIB and NPB)
with respect to allocated users. Industry Canada is the responsible
agency in Canada for the licensing of the radio frequency (RF)
spectrum and was actively involved in the development of stringent specifications for the 3rd Gen HFSWR to ensure operation
on a NIB/NPB while remaining available 24 hours a day, 7 days a
week. Background information related to operational requirements
for operating on a NIB/NPB can be found in [2]. The paper details
the challenge faced by the radar design engineer as HFSWR technology migrates from experimental to operational status.
These challenges are met in the 3rd Gen HFSWR by the addition of an integrated Proactive Remote Spectrum Management
(PRISM) system. The system builds on a cognitive radio Dynamic
Spectrum Access (DSA) spectrum sharing scheme that allows NIB/
NPB users access to portions of the spectrum that are not being utilized by licensed primary users. DSA enables significant improvement in efficient use and maximizes the number of users of the
spectrum compared to traditional fixed spectrum access [3].
To meet Industry Canada's requirements, the system had to
identify other users of the spectrum that were just above the background noise level. To meet this requirement, it was necessary to
implement an impulsive noise detection and removal algorithm in
the wideband data channel that was considerably more sensitive
than its narrow-band radar counterpart. In developing the algorithm, it was observed that corrupted pulses identified in the wideband data could be readily identified and removed from the narrow
band radar data.

SENSE AND ADAPT
The PRISM system, illustrated in Figure 1, continuously monitors
the authorized part of the HF spectrum for other users. It generates
and maintains a database of historical frequency use of this band.
From the database, the system generates a list of open channels
and the bandwidths of these channels along with a probability of
the channel remaining open. This probability being derived based
on the bandwidth and past use of the frequency channel. This list is

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DECEMBER 2017

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