62
4 Measuring Principles and Techniques …
D max =
λ 0
2
1 +
ϕ rfl
2π
.
(4.11)
Formula (4.11) demonstrates that by phase method we can measure ranges
comprising only fractions of operating wavelength. To obtain a single-valuedness,
it is required by some means to narrow a band of simultaneously measured ranges
in such way that maximum possible phases shift will not exceed 360° in this band.
Another disadvantage of the method connects with difficulties of influence exclusion
of unknown reflection phase from a target ϕ OTP .
From the other hand, the phase method is distinguished by a high accuracy and a
possibility to directly measure a radial velocity of targets based on Doppler effect.
It is interesting to mention a principal difference in a technique of dwell time
reading (countdown) between pulse method from one hand, and a frequency and a
phase one—from another hand. At pulse method, for dwell time reading, the reflected
oscillations are compared in time with those which were radiated t D before. At
frequency and phase methods, the reflected oscillations are compared with those
which are generated at this moment of time, i.e., in a moment of reading.
4.2 Angular Coordinates Measurement Methods
All types of measurement methods of angular coordinates (azimuth and elevation
angle) of a target are based on creation using an antenna, a directional reception
of radio waves, radiated, reradiated or scattered by an object. In radar location and
radar navigation, the three base methods of angular coordinates measurement are
widely used: maximum method, when an angle is registered by the maximum signal
amplitude at passing of radiofrequency beam (directional pattern) through an object;
minimum method, when a direction to an object is registered by the smallest amplitude in a receiver; target amplitudes comparison method, obtained from two mixed
in a space radio rays.
Amplitude angular coordinates measurement methods. Fundamental distinctive feature of amplitude methods of angular coordinates measurement in radar location and radar navigation concludes in a cause (source) of electromagnetic emission
of an objects. In radar navigation, an object itself is a source of electromagnetic radiation, in radar location, in the most cases, an electromagnetic radiation of an object
is a consequence of sounding oscillations sending.
Functional measurement diagram of a target-bearing α relatively to selected direction via maximum method is given in Fig. 4.6. In radar location and radar navigation,
an angular coordinates of an object are counted from some reference direction, e.g.,
a direction to the north or direction of an object longitudinal axis.
As we can see on a diagram, a target angular coordinate at maximum method
is an angle between a reference direction and direction of antenna peak pattern
to a target (beam angle). The purpose is to fix the last direction. This is achieved
by rotating of directional pattern in space via mechanical rotation of antenna or
4 Measuring Principles and Techniques …
D max =
λ 0
2
1 +
ϕ rfl
2π
.
(4.11)
Formula (4.11) demonstrates that by phase method we can measure ranges
comprising only fractions of operating wavelength. To obtain a single-valuedness,
it is required by some means to narrow a band of simultaneously measured ranges
in such way that maximum possible phases shift will not exceed 360° in this band.
Another disadvantage of the method connects with difficulties of influence exclusion
of unknown reflection phase from a target ϕ OTP .
From the other hand, the phase method is distinguished by a high accuracy and a
possibility to directly measure a radial velocity of targets based on Doppler effect.
It is interesting to mention a principal difference in a technique of dwell time
reading (countdown) between pulse method from one hand, and a frequency and a
phase one—from another hand. At pulse method, for dwell time reading, the reflected
oscillations are compared in time with those which were radiated t D before. At
frequency and phase methods, the reflected oscillations are compared with those
which are generated at this moment of time, i.e., in a moment of reading.
4.2 Angular Coordinates Measurement Methods
All types of measurement methods of angular coordinates (azimuth and elevation
angle) of a target are based on creation using an antenna, a directional reception
of radio waves, radiated, reradiated or scattered by an object. In radar location and
radar navigation, the three base methods of angular coordinates measurement are
widely used: maximum method, when an angle is registered by the maximum signal
amplitude at passing of radiofrequency beam (directional pattern) through an object;
minimum method, when a direction to an object is registered by the smallest amplitude in a receiver; target amplitudes comparison method, obtained from two mixed
in a space radio rays.
Amplitude angular coordinates measurement methods. Fundamental distinctive feature of amplitude methods of angular coordinates measurement in radar location and radar navigation concludes in a cause (source) of electromagnetic emission
of an objects. In radar navigation, an object itself is a source of electromagnetic radiation, in radar location, in the most cases, an electromagnetic radiation of an object
is a consequence of sounding oscillations sending.
Functional measurement diagram of a target-bearing α relatively to selected direction via maximum method is given in Fig. 4.6. In radar location and radar navigation,
an angular coordinates of an object are counted from some reference direction, e.g.,
a direction to the north or direction of an object longitudinal axis.
As we can see on a diagram, a target angular coordinate at maximum method
is an angle between a reference direction and direction of antenna peak pattern
to a target (beam angle). The purpose is to fix the last direction. This is achieved
by rotating of directional pattern in space via mechanical rotation of antenna or