118
5 Performance Characteristics of Radar Location …
come to matched filter, parameters of which differ from a nominal, then this filter
already becomes mismatched with all consequent particularities: a minimum value
of output signal reduces (a signal power to noise ratio at output reduces), a response
function at output of signals processing unit extends. Output signal extension in delay
and Doppler frequencies axes leads, as it is obvious, to degradation of resolution in
corresponding coordinates.
Concentrate on a set of factors, effecting on resolution probability of radar systems
and typical for the most type of radar systems.
Signals distortion at its forming in radar transmission path. Signals parameters
change will lead to its mismatching with processing unit that was mentioned above. At
forming of high-frequency pulses, for example, random changes of carrier frequency
are possible. Additional random modulation appears and spectrum structure changes.
These factors will lead to degradation of targets resolution both in range and in
Doppler frequencies. If frequency modulation, for example, is used in signals, then
distortions in transmitter will lead to FM deviation from a given modulation law that
in its turn also will lead to distortion of output signal at processing of signals and,
consequently, to degradation of resolution capability.
Errors at arrangement of antenna systems. Different manufacturing faults in
antenna structure, e.g., in scatterer profile generation, lead to distortions of antenna
DP, to main beam width spread and to side-lobes level increase. All these errors will
lead to degradation of radar resolution capability in angular coordinates.
Huge effect on radar resolution capability can be done due particularities arising
at signals propagation in space. For instance, atmospheric inhomogeneity can lead,
at radio waves travel, to appearance of signals phase fluctuations and as a result—to
wave fronts structure distortion, that in its turn will change antenna DP at receiving
and degrade targets resolution in angular coordinates.
Irregularities in target moving or radar platform (in case of onboard radars) create
distortions in a form of signal, in its spectrum structure, in change of modulation
laws. In all cases, it is arguably that to limiting value of resolution magnitude δξ lim
in some coordinate ξ some “increment” is added ξ, which defines a degradation
of targets resolution. Real resolution capability, evaluating by a value δξ r , can be
written as follows:
δξ r = δξ lim +
Resolution degradation is numerically can be evaluated by resolution degradation
coefficient:
α r =
δξ r
δξ lim
= 1 +
δξ lim
δξ lim
.
(5.87)
Influence of indicator (displaying) units parameters on resolution capability of
radar location systems. Radar indicator units have a largest effect on targets resolution
quality. This refers to almost all types of radars.
5 Performance Characteristics of Radar Location …
come to matched filter, parameters of which differ from a nominal, then this filter
already becomes mismatched with all consequent particularities: a minimum value
of output signal reduces (a signal power to noise ratio at output reduces), a response
function at output of signals processing unit extends. Output signal extension in delay
and Doppler frequencies axes leads, as it is obvious, to degradation of resolution in
corresponding coordinates.
Concentrate on a set of factors, effecting on resolution probability of radar systems
and typical for the most type of radar systems.
Signals distortion at its forming in radar transmission path. Signals parameters
change will lead to its mismatching with processing unit that was mentioned above. At
forming of high-frequency pulses, for example, random changes of carrier frequency
are possible. Additional random modulation appears and spectrum structure changes.
These factors will lead to degradation of targets resolution both in range and in
Doppler frequencies. If frequency modulation, for example, is used in signals, then
distortions in transmitter will lead to FM deviation from a given modulation law that
in its turn also will lead to distortion of output signal at processing of signals and,
consequently, to degradation of resolution capability.
Errors at arrangement of antenna systems. Different manufacturing faults in
antenna structure, e.g., in scatterer profile generation, lead to distortions of antenna
DP, to main beam width spread and to side-lobes level increase. All these errors will
lead to degradation of radar resolution capability in angular coordinates.
Huge effect on radar resolution capability can be done due particularities arising
at signals propagation in space. For instance, atmospheric inhomogeneity can lead,
at radio waves travel, to appearance of signals phase fluctuations and as a result—to
wave fronts structure distortion, that in its turn will change antenna DP at receiving
and degrade targets resolution in angular coordinates.
Irregularities in target moving or radar platform (in case of onboard radars) create
distortions in a form of signal, in its spectrum structure, in change of modulation
laws. In all cases, it is arguably that to limiting value of resolution magnitude δξ lim
in some coordinate ξ some “increment” is added ξ, which defines a degradation
of targets resolution. Real resolution capability, evaluating by a value δξ r , can be
written as follows:
δξ r = δξ lim +
Resolution degradation is numerically can be evaluated by resolution degradation
coefficient:
α r =
δξ r
δξ lim
= 1 +
δξ lim
δξ lim
.
(5.87)
Influence of indicator (displaying) units parameters on resolution capability of
radar location systems. Radar indicator units have a largest effect on targets resolution
quality. This refers to almost all types of radars.