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6 Detection of Radio Signals and Its Parameters Measuring
6.2 Coordinates and Movement Parameters Measuring
of Radar Targets
The previous chapters stated that at reflection from a target there is an essential
modulation of radio signal. Reflected signal parameters carry information on object,
its coordinates and movement parameters. This information can be placed in amplitude, frequency, phase, signal delay time, direction of arrival, etc. In order to obtain
an information on coordinates and movement parameters of an object (target), it is
necessary to measure values of the mentioned parameters, i.e., conduct its evaluation.
Targets surveillance process is followed by noises of different nature, i.e., obtained
during radar receiving evaluations of signal parameters are not necessarily precisely
correspond to true values. Besides, signal parameters, which do not carry useful
information, can much effect on measurements and thus are called non-informative
parameters. For instance, the delay time carries information on distance to a target
in radar signal, and amplitude and phase of signal have almost no information on
distance and, consequently, amplitude and phase of radar signal in this case are
non-informative parameters. Further, parameters of radar signal, which carry useful
information on an object, we will call as informative parameters. Such parameters,
for example, are: delay time t dly , arrival angle of reflected wave γ , Doppler frequency
shift f Dp in reflected signal, since they permit to obtain information correspondingly
on distance (range), angular coordinates and approaching velocity.
We will assume that desired (useful) signal S(t) and noise n(t) are additively
included in receiving oscillation y(t). Then receiving oscillation can be written as
follows:
y(t) = S
t, α(t), α ni p (t)
+ n(t); t ∈ [0, t obs ]
(6.27)
where α(t)—in general case a vector of informative parameters, the components of
which are: t d , f Dp , γ etc.; α ni p (t)—vector of non-informative parameters; n(t)—
noise, the nature of which can be widely differing; t obs —time of observation y(t).
By analyzing the receiving oscillation (7.44), it is necessary to make a decision on
what values are for informative parameters α of signal S
t, α(t), α ni p (t)
in current
time moment t. If during observation time t obs , the components α i (t) are constant
(α i (t) = const = α; t ∈ [0, t obs ]), then the described procedure is called parameters
evaluation, when it is prohibited to disregard the signal parameter change α i (t) per
t ∈ [0, t obs ] time and it is required the tracking of changing informative parameters
values, then it is called as parameters filtering of radar signal.
Due to the fact that measuring process of informative parameters of radar signal is
accompanied with noises, then random measuring errors are inherent to this process.
Enumerate the primary reasons leading to errors in measurement of informative
parameters α i (t) of radar signal.
At first, availability of internal noises of radar receiver and external noises lead to
random change of signal shape depending on measured parameter. Errors, stipulated
6 Detection of Radio Signals and Its Parameters Measuring
6.2 Coordinates and Movement Parameters Measuring
of Radar Targets
The previous chapters stated that at reflection from a target there is an essential
modulation of radio signal. Reflected signal parameters carry information on object,
its coordinates and movement parameters. This information can be placed in amplitude, frequency, phase, signal delay time, direction of arrival, etc. In order to obtain
an information on coordinates and movement parameters of an object (target), it is
necessary to measure values of the mentioned parameters, i.e., conduct its evaluation.
Targets surveillance process is followed by noises of different nature, i.e., obtained
during radar receiving evaluations of signal parameters are not necessarily precisely
correspond to true values. Besides, signal parameters, which do not carry useful
information, can much effect on measurements and thus are called non-informative
parameters. For instance, the delay time carries information on distance to a target
in radar signal, and amplitude and phase of signal have almost no information on
distance and, consequently, amplitude and phase of radar signal in this case are
non-informative parameters. Further, parameters of radar signal, which carry useful
information on an object, we will call as informative parameters. Such parameters,
for example, are: delay time t dly , arrival angle of reflected wave γ , Doppler frequency
shift f Dp in reflected signal, since they permit to obtain information correspondingly
on distance (range), angular coordinates and approaching velocity.
We will assume that desired (useful) signal S(t) and noise n(t) are additively
included in receiving oscillation y(t). Then receiving oscillation can be written as
follows:
y(t) = S
t, α(t), α ni p (t)
+ n(t); t ∈ [0, t obs ]
(6.27)
where α(t)—in general case a vector of informative parameters, the components of
which are: t d , f Dp , γ etc.; α ni p (t)—vector of non-informative parameters; n(t)—
noise, the nature of which can be widely differing; t obs —time of observation y(t).
By analyzing the receiving oscillation (7.44), it is necessary to make a decision on
what values are for informative parameters α of signal S
t, α(t), α ni p (t)
in current
time moment t. If during observation time t obs , the components α i (t) are constant
(α i (t) = const = α; t ∈ [0, t obs ]), then the described procedure is called parameters
evaluation, when it is prohibited to disregard the signal parameter change α i (t) per
t ∈ [0, t obs ] time and it is required the tracking of changing informative parameters
values, then it is called as parameters filtering of radar signal.
Due to the fact that measuring process of informative parameters of radar signal is
accompanied with noises, then random measuring errors are inherent to this process.
Enumerate the primary reasons leading to errors in measurement of informative
parameters α i (t) of radar signal.
At first, availability of internal noises of radar receiver and external noises lead to
random change of signal shape depending on measured parameter. Errors, stipulated