11 Radar Systems of Air Transport
201
Fig. 11.12 Detection
method of “wind shear”
The “wind shear” (WS) detection method is based on principle of Doppler frequencies allocation reflected from a signal of moving moisture targets; this phenomenon is
directly connected with moving of air volumes in air space, containing microparticles.
The purpose consists in measuring in each element of resolution in range (in range
channel) of Doppler frequency and comparing of measured values in neighboring
elements. If values of Doppler frequencies are differed, that corresponds to different
moving speed of air masses in air space, this testifies on WS at distance, corresponding
to a channel number, and difference magnitude of Doppler frequencies—on WS value
(Fig. 11.12).
The turbulence detection method is based on Doppler frequencies allocation from
a reflected (from moving moisture targets) signal. This phenomenon is directly
connected with moving of air volumes in air space, containing microparticles. The
purpose consists in measuring in each element of Doppler frequency resolution and
determination of a distribution law nature of obtained values. If distribution character is a random process, then a decision on turbulence presence in this resolution
element is taken, where a distribution character has a normal law of distribution.
Normal law of distribution is characterized by zero mathematical expectation, and
maximum spread in values is in confidence interval 3σ.
If in resolution element a phenomenon of turbulence is absent, then accumulation
function will have an increasing character with further exceeding of threshold value
(Fig. 11.13). At presence of turbulence, the threshold will not be exceeded. Threshold
value is defined according to a rule 3σ, where a threshold can have several values,
which characterize a value of turbulence current (flow).
WNRS with wind shear and turbulence detection functions is referred to pseudocoherent radars. An example of such WNRS is a system installed on medium-range
aircraft. In Fig. 11.14, an example of information indication on wind shear presence
in the direction of an aircraft flight is presented.
201
Fig. 11.12 Detection
method of “wind shear”
The “wind shear” (WS) detection method is based on principle of Doppler frequencies allocation reflected from a signal of moving moisture targets; this phenomenon is
directly connected with moving of air volumes in air space, containing microparticles.
The purpose consists in measuring in each element of resolution in range (in range
channel) of Doppler frequency and comparing of measured values in neighboring
elements. If values of Doppler frequencies are differed, that corresponds to different
moving speed of air masses in air space, this testifies on WS at distance, corresponding
to a channel number, and difference magnitude of Doppler frequencies—on WS value
(Fig. 11.12).
The turbulence detection method is based on Doppler frequencies allocation from
a reflected (from moving moisture targets) signal. This phenomenon is directly
connected with moving of air volumes in air space, containing microparticles. The
purpose consists in measuring in each element of Doppler frequency resolution and
determination of a distribution law nature of obtained values. If distribution character is a random process, then a decision on turbulence presence in this resolution
element is taken, where a distribution character has a normal law of distribution.
Normal law of distribution is characterized by zero mathematical expectation, and
maximum spread in values is in confidence interval 3σ.
If in resolution element a phenomenon of turbulence is absent, then accumulation
function will have an increasing character with further exceeding of threshold value
(Fig. 11.13). At presence of turbulence, the threshold will not be exceeded. Threshold
value is defined according to a rule 3σ, where a threshold can have several values,
which characterize a value of turbulence current (flow).
WNRS with wind shear and turbulence detection functions is referred to pseudocoherent radars. An example of such WNRS is a system installed on medium-range
aircraft. In Fig. 11.14, an example of information indication on wind shear presence
in the direction of an aircraft flight is presented.