=Paper= {{Paper |id=Vol-3654/paper26 |storemode=property |title=Method of Binary Detection of Small Unmanned Aerial Vehicles |pdfUrl=https://ceur-ws.org/Vol-3654/paper26.pdf |volume=Vol-3654 |authors=Denys Bakhtiiarov,Bohdan Chumachenko,Oleksandr Lavrynenko,Serhii Chumachenko,Vitalii Kurushkin |dblpUrl=https://dblp.org/rec/conf/cpits/BakhtiiarovCLCK24 }} ==Method of Binary Detection of Small Unmanned Aerial Vehicles== https://ceur-ws.org/Vol-3654/paper26.pdf
                         Method of Binary Detection of Small Unmanned Aerial
                         Vehicles
                         Denys Bakhtiiarov1, 2, Bohdan Chumachenko2, Oleksandr Lavrynenko2,
                         Serhii Chumachenko2, and Vitalii Kurushkin2
                         1 State Scientific and Research Institute of Cybersecurity Technologies and Information Protection, 3 Maksym

                         Zaliznyak, Kyiv, 03142, Ukraine
                         2 National Aviation University, 1 Kosmonavta Komarova ave., Kyiv, 03058, Ukraine



                                          Abstract
                                          This research offers a method for detecting Small Unmanned Aerial Vehicles (sUAVs) in
                                          binary using state-of-the-art technology and signal processing techniques. The proposed
                                          method combines machine learning and signal analysis techniques to reliably determine
                                          the presence of sUAVs in a particular airspace. Pattern recognition, real-time data
                                          processing, and spectral analysis are the three primary phases of the approach.
                                          Qualitative characteristics of sUAV signals can be identified by spectral analysis. The
                                          system can learn and identify these properties and make judgments regarding the
                                          presence or absence of sUAVs thanks to the application of machine learning methods.
                                          Furthermore, the system’s ability to recognize common patterns of sUAV activity is
                                          improved by the integration of pattern recognition. Processing data in real-time
                                          guarantees system responsiveness and lowers the number of false signals. The efficiency
                                          of the suggested sUAV detection system is strongly demonstrated by experimental results
                                          acquired in a variety of environmental circumstances. This highlights how the system can
                                          improve airspace monitoring measures’ effectiveness and safety.

                                          Keywords 1
                                          Binary detection, signal processing, spectral analysis, detection accuracy, airspace
                                          monitoring.

                         1. Introduction                                                                                        by processing a set of n amplitude beat signals in
                                                                                                                                an FMCW radar, determined for each probing
                         Let’s consider the task of binary detection of                                                         FMCW radio signal over a specific observation
                         small-sized targets against the background noise                                                       interval t = [0; T].
                         of the receiving channel of an active radar system                                                        The amplitude of the ith beat signal
                         from the perspective of the statistical hypothesis                                                     corresponds to the ith probing FMCW radio
                         testing theory in the presence of interference.                                                        pulse in the series [5].
                         Initially, let’s assume that the movement
                         parameters of the UAV are known [1–3], hence                                                           2. Problem Statement
                         the form of the useful signal is known. Similar
                         tasks were addressed by many authors when                                                              The formulation of this task is determined by the
                         developing algorithms to detect signals of a                                                           specific nature and technical implementation of
                         known form, which comprise a bunch of received                                                         receiving channels in typical ground-based short-
                         radio pulses, against the backdrop of additive                                                         range active radars with probing FMCW radio
                         Gaussian noise [4]. In this section, we examine                                                        signals. In such contemporary digital radars, for
                         the task of detecting a small-sized moving target                                                      each probing FMCW radio signal, signal beat

                         CPITS-2024: Cybersecurity Providing in Information and Telecommunication Systems, February 28, 2024, Kyiv, Ukraine
                         EMAIL: bakhtiiaroff@tks.nau.edu.ua (D. Bakhtiiarov); bohdan.chumachenko@npp.nau.edu.ua (B. Chumachenko);
                         oleksandrlavrynenko@tks.nau.edu.ua (O. Lavrynenko); serhii.chumachenko@npp.nau.edu.ua (S. Chumachenko);
                         vitaliy.kurushkin@npp.nau.edu.ua (V. Kurushkin)
                         ORCID: 0000-0003-3298-4641 (D. Bakhtiiarov); 0000-0002-0354-2206 (B. Chumachenko); 0000-0002-3285-7565 (O. Lavrynenko); 0009-
                         0003-8755-5286 (S. Chumachenko); 0009-0000-4411-0509 (V. Kurushkin)
                                      ©️ 2024 Copyright for this paper by its authors.
                                      Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).

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Workshop      ISSN 1613-0073
Proceedings
                                                                                                                      312
samples from the output of the analog-digital           approximation, we’ll describe the correlation
converter are processed [6]. This processing            function of the Gaussian random process using
involves calculating the Fast Fourier Transform,        a delta function. As can be inferred from
followed by delineating the amplitude spectrum          expression (1), random variations in the
to determine the distance to relevant objects [7,       background’s RCS lead to a multiplicative
8]. Such objects could be a background surface of       transformation of the useful signal A (t ) ,
a particular type. Hence, a distinctive feature of      meaning they act as multiplicative interference.
the method discussed in this subsection is the          The background’s RCS,  f (b 2  b 2 ) , is
processing of a set of amplitude samples of
signals reflected from background surfaces or           nonlinearly incorporated into the amplitude
objects included in a burst of radio pulses.            expression of the reflected signal, as described
    First, let’s determine the probability density of   by expression (1) (through the square root).
instantaneous signal values at the detector’s               Let’s determine the density distribution of
input both in the presence and absence of UAVs          the square root of the RCS and subsequently
[9].                                                    the density distribution of the amplitude of the
    During the observation time t =  0; T  , such     reflected signal.
                                                            It’s well-known that a nonlinear
amplitude variation of the radio signal is              transformation of a random variable results in
represented by the time function A (t ) . This time    the alteration of its distribution law in the
function A (t ) contains information about the         following way [11]:
presence of UAVs. Therefore, we’ll consider                                                     d ( B) ,
                                                                  W ( B) = W [ X = ( B)]                                (2)
 A (t ) it as the useful signal at the detector’s                                                dB

input. Let’s first address the task of detecting        where W ( X ) is the normal probability density
UAVs for a specific set of model parameters,            distribution of the random variable X.
described by expression (1).                               W ( B ) is the sought-after probability density
    Let’s assume that the detector’s input receives     distribution of the random variable A.
an additive mixture of the useful signal A (t ) and        ( B ) is the function inverse to the function
the noise of the receiving path, which we will          B = ( X ) .
consider as Gaussian and delta-correlated. As              In this context, X =  f (b 2  b 2 ) represents a
inferred from the materials presented earlier, the
power of the useful signal exceeds the power of         stationary random process, B =  f (b 2  b 2 ) ,
the additive noise of the receiving path by 25–30       and the density distribution of instantaneous
dB [6]. Under these conditions, the density             RCS values at a certain point in time is
distribution of the envelope of the observed radio      described by a Gaussian law:
signal follows a normal law with an average value                                                                 2
                                                                                              1   f − m f 
equal to the instantaneous value of the useful                                    1
                                                                                             − 
                                                                                              2   f        
signal envelope. Let’s represent the observed                   W ( f ) =              e                          ,   (3)
                                                                                 2 f
signal Y(t) as the sum of the useful signal A (t )
and the receiving path noise n(t):                      where     m f    is the average RCS of the
               Y (t ) = A (t ) + n(t ) .        (1)    background ( m =  f 0 ), in square meters; σ
                                                                             f

   In [10], it is demonstrated that the effective       represents the root mean square deviation of
scattering surface of the background during the         instantaneous RCS values of the background
observation of the useful signal acts as a              over the observation time of the useful signal,
stationary Gaussian random process. The                 in square meters [12].
temporal correlation interval of this process is            In this expression, to simplify the notation,
considerably shorter than the duration of the           bi-static angle designations b 2 and b 2 have
observed useful signal. As a first




                                                    313
been omitted. In general, they are functions of                                                                                 2      
                                                                                                                             1 B − m f 
                                                                                                                                            2

                                                                                                                            − 
time during the observation of the useful signal                                                        2 B                 2   f 
                                                                                                                                                .           (7)
                                                                                     W ( B) =                          e              
 A (t ) . However, in the context discussed,                                                           2  f
variations of the mentioned bi-static angles do
                                                                         The useful signal A (t ) is the product of the
not result in changes to the background RCS as
described by expression (2).                                         deterministic function f (t ) and the square root
     The random variations in the background                         of the random variable  f :
RCS  f over the observation time of the useful                                                             1 + k A (t ) + 2  k A (t )  cos  (t ) 
                                                                                                       
                                                                       A (t ) =  f  f (t ) =  f  AOTR  (8)
signal can be represented as the sum of the
                                                                        It’s known that multiplying a stationary
average value  f 0 and the fluctuation
                                                                     random process  f by a non-random time
component  f :                                                      function f (t ) results in a non-stationary
                                                                    random process with the same distribution law
             f = f 0 +f .                             (4)
                                                                     W (  f ) over the observation [14] interval of
   The multiplicative nature of interference                         the useful signal. Note that the multiplier AOTR
about the useful signal arises from fluctuations                     also varies over time as the UAV moves due to
in the RCS (Radar Cross-Section) of the                              changes in distances RAB , RBC , RAC , and the
background. However, the average value of the                        antenna gain factor. We consider these changes
background’s RCS doesn’t distort the shape of                        to be insignificant compared to the influence of
the useful signal.                                                   the oscillating multiplier f (t ) . In this case, the
   The probability density distribution of the
fluctuating component of the background RCS                          non-stationary process is the result of the
can be written as [13]:                                              product of the useful signal A (t ) and the
                                      
                                             2                       multiplicative interference  f . The non-
                                  1  f 
                                 − 
             
                                         
                                  2                              stationarity of the random process A (t ) is due
        W ( f ) =
                      1
                           e
                                     f 
                                               .       (5)
                     2                                            to the variability of the variance D(  f ) by
                            f
                                                                      f 2 (t ) times, leading to a change in the scale of

  Expressing the random variable X through B                         the probability density distribution W (  f ) .
and calculating the derivative, we obtain:                               The change in dispersion over time,
                           d ( B)                                   described by expression (8), according to the
       X = ( B) = B 2 ,           = 2 B .              (6)
                             dB                                      law of the useful signal can be written as
                                                                     follows:
   From this, we derive the sought distribution
law of the square root from RCS:
                                                                                                                                 2
                                                                                                             1   f − m f 
                                                                                                            − 
                                                                               
                                                                                           f                2   f        
             DA (t ) = AOTR
                         /
                              1 + k A (t ) + 2  k A (t )  cos  (t )                           e                   
                                                                                                                                     d f                   (9)
                                                                              −      2    f


    The probability distribution density of                             Regrettably, the integrals in formulas (7)–
instantaneous values of the useful signal over                       (9) cannot be expressed in terms of elementary
the observation period can be written as                             functions and can only be determined by
follows [15]:                                                        numerical integration.




                                                                314
                                                                                                                                                                2
                                                                                                                            A 2 − m f                    
                                                                                                       −  /                                                
                                                                                                        1
                                                        2  A                                            
                                                                                                        2  AOTR  1+ k A ( t ) + 2k A ( t )cos   
       W ( A , t )                                                                              e                                                     f 
                                                                                                                                                                    (10)
                        /
                        A
                        OTR    1 + k A (t ) + 2  k A (t )  cos  (t )   2   f


3. Method of Binary Detection of                                                       Where σn is the root mean square deviation of
                                                                                   the noise measurements in the receiving system.
   SUAV
                                                                                       The random process A (t ) is independent of
The useful signal A (t ) , modulated by                                           the receiving system noise. The probability
                                                                                   density function of the instantaneous values of
multiplicative interference, is observed against
                                                                                   the process Y (t ) from formula (1), represented as
the backdrop of additive Gaussian noise in the
reception path. The noise correlation interval                                     the sum of two independent random processes, is
of the reception path does not exceed one                                          determined by the convolution of the probability
microsecond. The duration of the useful signal                                     density of the receiving system noise, described
is in the order of seconds [16]. Hence,                                            by expression (11), and the probability density of
disregarding the correlated noise samples n(t),                                    the useful signal, described by expression (10), as
we regard it as white Gaussian noise with a                                        follows:
                                                                                                             
zero mean value and a probability distribution
density of instantaneous values:                                                           W (Y , t ) =  WA (Y − n, t ) Wn (n)dn .                                (12)
                                                                                                            −
                                               2
                                      1 n 
                    1         −  
                                                                                      Or, taking into account (10) and (11), we
                            e  n  .                           (11)
                               2 
          Wn (n) =
                   2   n                                                        obtain:

                                                                  
                                                                      2
                                                                            2                                     
                                                                                                                       2
                                                                                                                             2
                                                1  (Y − n ) − m f   n                      1  (Y − n ) − m f   n  
                                                             2                                                2

                                              −                      +                   −                      +  
                                                2   f ( t ) f   n                      2   f ( t ) f   n  
                                  Y  e          
                                                                                 dn −  n  e
                                                                                                                         
                                                                                                                                         dn                          (13)
                  W (Y , t ) =        −                                              −
                                                                       f (t )    f  n


    The density function described by formula                                      signal Y (t ) at the detector’s input characterizes a
(13) of the instantaneous values of the observed                                   non-stationary random process with time-
signal Y (t ) at the input of the detector                                         varying variance due to the target’s movement
characterizes a non-stationary random process                                      relative to the background surface.
with time-varying variance due to the motion of                                        It is known that the detection of small targets
the target relative to the background surface [16].                                is based on the processing of the observed signal.
    It is known that the detection of small targets                                In this case, the samples of such a signal are the
is based on the processing of the observed signal.                                 amplitudes of the LFMC radio pulse batch
In this case, the samples of such a signal are the                                 observed over the time interval t   0, T  . The
amplitudes of LFM radio pulses observed over a                                     optimal algorithm for detecting the useful signal
time interval t   0, T  . The optimal signal                                    will be sought based on the minimization of the
detection algorithm will be sought based on the                                    average risk, the consideration of which leads to
minimum average risk criterion, taking into                                        the determination of a specific expression for the
account which leads to the determination of a                                      likelihood ratio [17].
specific expression of the likelihood ratio.                                                                           W (Y / H1 ) .
                                                                                                        L(Y ) =                                                     (14)
   The density distribution described by formula                                                                       W (Y / H 0 )
(13) of the instantaneous values of the observed




                                                                            315
Hypothesis H₁ corresponds to the case of the                               signal observed at the detector’s input under
UAV’s movement in front of the background                                  the assumption of the validity of the hypothesis
surface, where the radio signal reflected from                             H1 is described by the following expression:
the background is modulated by the reflected
radio signal from the UAV. The model of the
    Y (t ) = AOTR
              /
                    f (b 2  b 2 )  1 + k A (t ) + 2  k A (t )  cos  (t )  = AOTR
                                                                                         /
                                                                                               f (b 2  b 2 )  f (t )                  (15)


    The randomness of the process Y (t ) is caused                         condition of UAV movement. Assuming that the
by fluctuations in the Radar Cross-Section (RCS)                           correlation interval of RCS fluctuations is much
 f (b 2  b 2 ) of the background. The modulation                       smaller than the duration of the useful signal, we
                                                                           can express the density distribution of sample
law Y (t ) is determined by the function f(t), which
                                                                           values Y under the presence of a moving UAV as
accounts for the non-stationary nature of the                              follows:
sample distribution density Y under the
                                                                                                                                        2
                                                                                                                     n  Y 2 −m     
                                                                                                                               f
                                                                                                                                  
                                                                                                    1                     i
                                                                                            −
                                                                                                      2 f i =1         f ( ti ) 
                                                           n
                                               2               Yi                             2 AOTR
                                                          
                                                                                                  /2

               W (Y / H1 , t ) =                                     e                                                                  (16)
                                         /
                                        AOTR  2   f i =1 f (ti )

    Hypothesis H₀ corresponds to the case of                               the validity of the hypothesis H1 is described
receiving a radio signal reflected from the
                                                                           by the following expression:
background. The model of the signal observed
at the detector’s input under the assumption of
                              Y (t ) = AOTR
                                        /
                                              f (b 2  b 2 ) = AOTR
                                                                    /
                                                                          f (b 2  b 2 )                                                (17)

   The density distribution of the sample Y                                pattern to expressions (10) and (11), it is
under the assumption of hypothesis H₀, in this                             expressed as follows:
case, is stationary, and, following a similar
                                                                                                n
                                                                                       (Yi2 −m f )2
                                                                                        1
                                                             n       −
                                                  2
                                                            Yi  e
                                                                       2 AOTR
                                                                           /2
                                                                               2 f i=1
                             W (Y / H 0 ) = /                                                                                               (18)
                                           AOTR  2  f i =1


   Substituting the conditional probability
density functions (16) and (17) into (18), we
obtain:
                                                                                                                 2
                                                                n                               n  Y 2 −m   
                                                                                                          f
                                                       n Y                                 f (ti ) 
                                                                                        1            i
                                                                         −
                                              2                            2 A/2 2
                                      /                  i  e OTR  f i=1                          
                                      AOTR  2    i =1 f (ti )
                             L(Y ) =                                                                                                      (19)
                                                     f

                                                            n                           n
                                                          n                           (Yi2 − m f )2
                                                                              1
                                                                     −
                                                2
                                        AOTR  2    
                                                                       2 AOTR
                                                                           /2
                                                                                2 f i=1
                                        /                  Yi  e
                                                       f 
                                                              i =1




   The obtained expression describes the
desired likelihood ratio for the problem of




                                                                      316
detecting UAVs in the case of multiplicative                                                             certain threshold  0 . We simplify the optimal
interaction between a known useful signal and
                                                                                                         detection algorithm described by formula (19)
amplitude fluctuations of the background.
                                                                                                         through logarithmization.
   The algorithm for detecting UAVs involves
comparing the expression (19), L (Y ) , with a
                                                                                             2
                                                         n  m
                                                                  
                                                                      2
                                           Yi 2 
                                                n
                                                                        n                                n
                                                                                                                        1 
                                         
                                     i =1 
                                                    +   f  −  (Yi 2 ) 2 + n  m2 f  + 2  m f   Yi 2  1 −
                                                                        i =1                                            ti )                     (20)
                                            f (ti 
                                                 )     i =1  f (t  )
                                                                   i                                                 f (
                    n
    ln  L(Y ) =  ln  f (ti )  −
                                −1                                                                       i =1

                  i =1
                                                                           2  AOTR
                                                                                  /2
                                                                                       2 f


   Therefore, the optimal algorithm for UAV                                                              between a known useful signal and amplitude
detection based on the Bayesian criterion,                                                               fluctuations of the background, takes the
considering the multiplicative interaction                                                               following form [17]:
                                  n                  n
                                                           Yi 4                          n
                                                                                                              1 
                                  Y −  f (t ) − 2  m   Y  1 − f (t ) 
                                        i
                                            4
                                                           2                    f               i
                                                                                                     2
                                                                                                                            
                                                                                                                             z 1 (ti )
                                                                                                                                H

                            z=
                                 i =1               i =1          i                  i =1                      i    where 
                                                                                                                             z (ti )
                                                                                                                            
                                                                                                                                H0
                                                                      2  AOTR
                                                                           /2
                                                                                2 f
                              A1 − B1       n
                                         −  ln f (ti ) + ln  0 —the modified threshold of the detector,
                                                       −1
             z (ti ) =
                          2  AOTR   f i =1
                               /2     2


                                                                                                         2
                                                                               n m 
                                                                      A1 =   f 
                                                                           i =1 
                                                                                             .                                                       (21)
                                                                                 f (ti ) 
                                                                      B1 = n  m2 f

    In the case of discrete sampling of                                                                     The structure of the optimal detector for
observations Y (t ) at the detector’s input, it                                                          detecting a moving UAV under the considered
follows from expression (21) that to decide the                                                          conditions is depicted in Fig. 1.
presence of a signal caused by UAV at the
detector’s input, a series of operations
involving the summation of nonlinearly
transformed samples from the observed
realization Y (t ) and the multiplication of the
square of the realization Y (t ) with a copy of the
expected useful signal, followed by summation
of the obtained results and comparison with a
threshold, should be performed [16].
    A distinctive feature of the modified
detector threshold         z (ti ) is its time                                                          Figure 1: Structural diagram of the optimal
                                                                                                         detector for UAV with known motion parameters
dependency proportional to the expected
signal due to the non-stationary nature of the                                                           The structural diagram of the optimal detector
random process. When the threshold level is                                                              does not show the synchronization device
exceeded, the presence of the moving UAV is                                                              responsible for clocking the detector blocks.
confirmed; otherwise, a decision is made about                                                           Since the additional phase shift during the
its absence [17].                                                                                        reflection of the radio signal by the target and the
                                                                                                         background surface is random, it is necessary to
                                                                                                         add a second quadrature channel to the




                                                                                             317
structural diagram presented in Fig. 2.16, where                                      background” line of sight is unknown. In the
the function f (t ) is defined with a phase shift of                                  conditions of a priori uncertainty about these
π/2 relative to the initial phase of the f (t )                                       parameters, the application of known
                                                                                      approaches to eliminate this uncertainty
function.
                                                                                      significantly complicates the above algorithm
The detection algorithm for UAV (21) is
                                                                                      and the structural diagram of the optimal
expedient to implement in the digital processing
                                                                                      detector [18]. To obtain a practically
block of the amplitude signals received in the
                                                                                      implementable UAV detection algorithm, we will
pulse     sequence.        However,     for     the
                                                                                      make a series of simplifications relative to the
implementation of this algorithm, including
                                                                                      observation model Y (t ) . These simplifications
setting the threshold, precise knowledge of
parameters such as the coordinates (angular                                           will lead to the implementation of a quasi-
position) of the phase center (point) of the                                          optimal detection algorithm.
background surface reflection, the values of                                             We will consider the model of the observed
current bistatic angles, the three-dimensional                                        input signal of the detector on the interval [0, T]
shape of the bistatic RCS of the target and                                           as an additive sum of a non-random useful signal
background, is required. Furthermore, the start                                       and Gaussian noise limited to  f b in bandwidth:
time of the UAV flight relative to the “radar-
                                      Y (t ) = AOTR 1 + k A (t ) + 2  k A (t )  cos  (t )  + n(t )                                           (22)

   For such an observation model, the detector                                           For the likelihood ratio (22), the probability
design has been explored by numerous authors                                          density in the presence of a signal H1 is
[19, 20]. Let’s briefly outline the results of
                                                                                      expressed as follows:
solving this problem. We will assume that the
data observation sampling interval is t = 1 .
                                                                           2  fb
                                                                                                                  n
                                                                                                                  (Yi2 −m f )2
                                                                                                        1
                                                                                      n       −
                                                                        2
                                                                                   Yi  e
                                                                                                  2 AOTR
                                                                                                      /2
                                                                                                          2 f i=1
                            W (Y / H1 ) =                                                                                                          (23)
                                                                /
                                                                A
                                                                OTR    2   f i =1


                                                1 n 
                                                            2                            Instead of comparing it to the threshold of
                           −  
                  1         2                                                        the likelihood ratio or function, we can
        Wn (n) =          e  n .                                         (24)
                                                                                      compare the logarithms of expressions (25) or
                 2   n
                                                                                      (26). Thus, we obtain the following decision
    Where σn is the root mean square deviation                                        rule for the considered detection problem [21]:
of the noise samples in the receiving path.                                                                  T                      zH1 (t )
    Under these conditions, the expression for                                                   2
                                                                                                 N 0 0
                                                                                              z=        Y (t ) A(t )dt               H0 .         (26)
the likelihood ratio will be written in a known                                                                                      z (t )
manner [19]:
                         t
                             n
                                           2 t
                                                 n                                        The formula z (t ) = ln  0 + E y represents the
                     −         Ai2              Yi  Ai
                                                                           (25)                                                        N0
         L(Y ) = e                    e
                         N0 i=1            N0 i=1
                                                            .
                                                                                      modified threshold. Therefore, the detection
  The formula can be alternatively expressed                                          device for a moving small-sized target under
as a likelihood ratio functional, which                                               these conditions corresponds to the well-
N 0 =  2n  f b represents the spectral power                                        known correlation receiver scheme depicted in
density of the noise in the receiving system.                                         Fig. 2.




                                                                                    318
    The synchronization device ensures coordinated             In this case, the reference signal of the
operation between the reference generator and the              correlation detector should be time-shifted
integrator, facilitating the comparison of its output          relative to the observed signal, and a procedure
signal z (t ) with the threshold. To ensure the                for searching and capturing the useful signal
functionality of the correlation detector, it is               should be performed. To simplify this
necessary to multiply the reference and observed               procedure, instead of a correlation detector for
signals at coincident time points. However, the                the useful signal, its version with matched
arrival time of the observed signal is unknown.                filters should be used. When the useful signal’s
                                                               time coincides with the impulse response of the
                                                               matched filter, the value of the correlation
                                                               integral will match the amplitude of the output
                                                               signal of the matched filter. The impulse
                                                               response of the matched filter h() for the
                                                               useful signal A(t ) is its mirrored copy, shifted
                                                               in time by t₀. The structural diagram of the UAV
Figure 2: Structural diagram of the correlation
                                                               detector with known parameters of its motion
detector for UAV with known parameters of its
                                                               using matched filters is shown in Fig. 3.
motion and initial phase



Figure 3: Structural diagram of the UAV detector using a matched filter with known parameters
of its motion and initial phase
The reference signal A(t ) has a random initial                contains two quadrature generators                  of
                                                               reference signals, A0 (t ) and A0s (t ) :
                                                                                   c
phase due to the reflection of radio waves from
the target, underlying surfaces, and
background. When radio waves are reflected                            A0 (t ) = ( A0c ) 2 + ( A0s ) 2 = const.   (27)
from these objects, an additional phase shift                     Similarly to how the envelope of a harmonic
becomes random.                                                signal    expressed     through     quadrature
   To eliminate the dependence of the                          components does not depend on time:
reference signal on the influence of random
phase shifts during the reflection of radio                        E0 (t ) = E 2 cos() 2 + E 2 sin() 2 = E .   (28)
waves, we use a structural scheme of a detector                    In this case, processing the observed signal
for a signal of known shape with a random                      in the small-sized target detection task will
initial phase. In this scheme, the detector                    involve comparing it to a threshold using the
                                                               following decision statistic:
                                                           2                            2
                                                                                   
                         z (t ) =   Y (t ) A0c (t − )d  +   Y (t ) A0s (t − )d  ,                      (29)
                                   −                       −                       

where Y (t ) is the observed realization of the                    A0s (t ) is the sine component of the reference
signal at the input of the detector.                           signal for the matched filter hs (t ) .
    A0c (t ) is the cosine component of the
                                                                   The structural diagram of the quadrature
reference signal for the matched filter hc (t ) .              detector for the UAV with known parameters
                                                               of its motion using matched filters is shown in
                                                               Fig. 4 [5].




                                                          319
Figure 4: Structural diagram of the quadrature detector for UAV with known parameters of its
motion
                                                       Technology             (2020).        doi:
4. Conclusions                                         10.1109/picst51311.2020.9467886.
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