IEEE Aerospace and Electronic Systems Magazine - November 2020 - 32

Evolution of Quantum Radar Concept to Noise Radar Concept

Figure 1.
Block diagram of CW NR with coherent frequency down-conversion and coherent reception and processing of radar returns: LNA-low
noise amplifier; LO-local oscillator; LPF-low-pass filter; IF-intermediate frequency; VCO-voltage controlled oscillator; ADC-analogue-to-digital converter; DAC-digital-to-analogue converter; NG-noise generator; CW-continuous waveform; PA-power amplifier;
D-C-directional coupler; PC-personal computer; FPGA-field programmable gate array.

contrast, we conclude that ultrashort-range applications look
most promising for the QR concept, especially for such working frequencies and PSD widths where digital sampling is not
available nowadays.

NOISE RADAR
NR is a radar that uses classical noise/random/chaotic continuous waveform (CW) or pulsed waveform (PW) as a radar
signal and coherent reception (analogue or digital) of radar
returns via estimation of cross-correlation Rðt; t 0 ; T Þ
between the reference signal, i.e., properly delayed copy of
sounding signal Xðt À tÞ and radar return Xðt À t 0 Þ [9]-
[12]. Figure 1 shows simplified block-diagram of CW NR
with analogue coherent frequency down-conversion and
with digital reception and processing of radar returns. It is
seen that NR uses the illumination of an area of interest by
random signals and coherent (both amplitude and phase)
detection of radar returns, i.e., the sounding signals back scattered from targets met in the observed area of interest.
Assuming that in NR, we use stationary (in wide
sense) and ergodic random signals, we may substitute the
averaging over an ensemble of random signal realizations
by averaging over time when estimating cross-correlations
between reference and radar returns:
32

1
T !1 2T

Rðt; t 0 ; T Þ ¼ lim

Z

T
ÀT

Xref ðt À t d Þ X ðt À t0 Þdt

(1)

where t 0 is a time delay of sounding signal due to its
propagation toward a target and back; t d is delay of a reference signal in a " delay line " of the correlator. In modern NR, the delay of the reference signal is performed
digitally in a computer provided fast enough ADC is
available [11], [12].
Assuming infinite integration time and applying
Khinchin-Wiener theorem, we may rewrite (1) as follows:
1
T !1 2T

Rðt Þ ¼ lim

Z

T
ÀT

Xref ðtÞ Xðt À t Þdt ¼

1
2p

Z

1

À1

S ðvÞ eivt dv

(2)
:
1
where SðvÞ ¼ limT !1 2pT
jXðvÞj2 ;
:
Àivt
XðtÞ e
dv; t ¼ t d À t 0 .

:
XðvÞ ¼

R
1 1
2p À1

Here, SðvÞ stands for PSD of random signal XðtÞ.
Range resolution of NR, i.e., its capability of detecting
two closely placed targets as two targets rather than one,
is dependent on PSD bandwidth B of sounding noise signal as follows:
Dr ¼ c=2B ¼ ctc =2

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