68
4 Measuring Principles and Techniques …
pulse train is received on each of beams simultaneously and external random interferences are compensated at comparison (subtraction). To create a equisignal direction at
parallel method, it is minimally necessary to have not two, but one pulse of reflected
energy. It follows a widespread name of parallel comparison technique—singlepulsed, or, otherwise, monopulse technique of target direction-finding (lobing). Its
distinctive feature is a creation of “instantaneous” equisignal direction (it will be
recalled that at consequent technique the switching time T s is required for creation
of equisignal direction).
Monopulse direction-finding technique has important advantages before pattern
scanning (shifting) method at measuring of its angular coordinates of a target, a
reflected signal of which is grossly changes in a time (fluctuated), and at operation in
radio interference conditions as well. To create a equisignal direction simultaneously
in two mutually perpendicular planes (in azimuth and elevation angle), it is necessary
to have four (4) antennas (or four emitters in one antenna system), creating the same
intercrossing directional patterns positioned at low angle to each other.
Phase angular coordinates measurement methods. Phase methods of targets
angular coordinates measurement are based on measuring of signals phase difference,
received by antennas, spaced at distance l (Fig. 4.12) and installed the way that its
axis should be parallel to each other. Consequently, directional patterns axis will
be parallel as well. A length l of antennas diversity (spacing) is called a base. Path
(propagation) difference of radio waves will be ΔD = l sin α, i.e., will depend on
bearing angle α. Phases difference, corresponding to a distance D and picked out
in comparison circuit, is easily determined since a phase difference, equaling to 2π,
corresponds to length λ (wavelength):
ϕ =
2π
λ
ΔD =
2π
λ
l sin α.
(4.17)
Fig. 4.12 Phase angular
coordinates measurement
method
4 Measuring Principles and Techniques …
pulse train is received on each of beams simultaneously and external random interferences are compensated at comparison (subtraction). To create a equisignal direction at
parallel method, it is minimally necessary to have not two, but one pulse of reflected
energy. It follows a widespread name of parallel comparison technique—singlepulsed, or, otherwise, monopulse technique of target direction-finding (lobing). Its
distinctive feature is a creation of “instantaneous” equisignal direction (it will be
recalled that at consequent technique the switching time T s is required for creation
of equisignal direction).
Monopulse direction-finding technique has important advantages before pattern
scanning (shifting) method at measuring of its angular coordinates of a target, a
reflected signal of which is grossly changes in a time (fluctuated), and at operation in
radio interference conditions as well. To create a equisignal direction simultaneously
in two mutually perpendicular planes (in azimuth and elevation angle), it is necessary
to have four (4) antennas (or four emitters in one antenna system), creating the same
intercrossing directional patterns positioned at low angle to each other.
Phase angular coordinates measurement methods. Phase methods of targets
angular coordinates measurement are based on measuring of signals phase difference,
received by antennas, spaced at distance l (Fig. 4.12) and installed the way that its
axis should be parallel to each other. Consequently, directional patterns axis will
be parallel as well. A length l of antennas diversity (spacing) is called a base. Path
(propagation) difference of radio waves will be ΔD = l sin α, i.e., will depend on
bearing angle α. Phases difference, corresponding to a distance D and picked out
in comparison circuit, is easily determined since a phase difference, equaling to 2π,
corresponds to length λ (wavelength):
ϕ =
2π
λ
ΔD =
2π
λ
l sin α.
(4.17)
Fig. 4.12 Phase angular
coordinates measurement
method