Aerospace and Electronic Systems Magazine September 2017 - 51

Xu et al.

Figure 2.

Range-compressed radar echoes on PPI.

main or MTI filter [1]-[3] in the time domain, may inevitably bring
about SNR loss for target detection to some extent. So when and
where to use these methods is a key problem for a RSP designer
attempting to balance strong background suppression and weak
target detection. In addition, which method should be chosen in a
real system is always a tradeoff between required performance and
engineering realizability. Therefore, the RSP methods with high
effectiveness and efficiency are needed in many scenarios. In the
following sections, how RSP can improve radar performance is
discussed by combining some necessary aspects.

ACCURATE ENVIRONMENT SENSING FROM ECHOES
Let's look at some real measured echoes in the plane position indicator (PPI) from certain weather radar (Figure 2). Many things
can be sensed from the radar echoes, which contain much information about the environment and targets. In the near range, there are
many regions caused by fixed ground clutters, which always exist
when radar works and may be tens of decibels higher than that
of a target. In the right-hand part, there is a large patch of moving weather clutter, which is not fixed and changing with time and
space. In addition, there is some active jamming from the azimuth
of 90° from north, which distributes along the entire range and
is occasionally generated by a spectrum-shared communication
station. Besides, there are many targets to be detected, and they
may appear anywhere in the detection coverage diagram. Figures
3a and 3b give the targets in the clear region and the ground clutter region, respectively. Clutter, noise, and jamming have different
SEPTEMBER 2017

backscattering characteristics on amplitude, space, Doppler, polarization, etc., and it is possible to identify these from echoes. However, there are many difficulties in accurately sensing these components from echoes, like the band-limited information contained
in the echoes, the variable time-space-frequency distribution, the
uncertainty of multiple-component existence, and the difficulties of segmenting different components with different multiscale
distributions. Fortunately, these components are normally slowly
time variant compared with moving targets and can be sensed accordingly, as long as the proper methods are adopted. Accurate
environment sensing from echoes is the foundation for successful
resource management and target detection. In addition, apart from
the echoes, some auxiliary devices like a global position system
(GPS), geographic information system (GIS), or automatic dependent surveillance-broadcast (ADS-B) should be introduced as the
environment information supplements of radar.

EFFECTIVE RESOURCE MANAGEMENT FOR OPTIMIZATION
To accomplish a given detection task, modern radar can manage
and optimize detection resources (Figure 4) in six domains: power, aperture, time, frequency, polarization, and waveform. Each
of these can find its contribution in the radar equation [1]-[3] in
search mode as
1

Rmax


Pt Arσ
T 4
= 
× s  ,
 4π kT0 FnSNR min Ω 

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