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Description 1, title of the invention
Method and apparatus for aligning an antenna of an acoustic radar
3. Detailed description of the invention Local meteorological parameters such as temperature
structures (such as temperature inversion layers) or three-dimensional vertical wind speed
profiles performed by soda (SODAR) or sound (sound j 1) radar type weather stations In the case
of telemetry, there are various problems in signal processing since the signal to be picked up is
extremely weak. For these, Applied optics, il Vol. 1972, pp. 108-112, J. Em-r-'/ Jal, et al. (J, M,
Marshalletal), 1 Combined Radar Acoustic Sounding System' (CombinedRadar-AcousticSounding
System). I want to. The antenna used in the acoustic remote sensing system is generally parabolic
and consists of a paraboloid on which a hood extends with a sound absorbing material inside,
and the back reflection signal corresponds to this match. It is picked up at the exit plane of the
acoustic wrapper fitted on the axis of the plane. Although this type of antenna has a high degree
of gain, it has the disadvantage that interference fringes occur on the scale of half the wavelength
of the sound between the bottom of the paraboloid and the exit plane of the trumpet. As a result,
the transmission function of the antenna frequency is in the form of a sine wave-since the
transmission frequency is chosen as a function of the range, the focal point of the antenna is an
integer multiple of the focal length of the paraboloid half the wavelength of the sound. In some
cases the reference temperature T. For (eg 15 ° C.) it is located near the sound pressure
antinode. In such a case, the sound pressure antinode will be located at the focal point where the
exit plane of the wrapper is preferably located. For the transmission frequency, this condition is
obviously wavelength dependent at 6-EndPage: 2, and therefore at the bottom of the
parabolically shaped antenna. In other words, for the position of the pickup element along the
axis of the paraboloid, the pickup element records an amplitude that changes according to the
temperature T at that time for the signal input to the antenna, why The present invention relates
to an automatic antenna matching method as well as means for implementing it, whereby the
pattern of the interference fringes, which is then established, according to the increase or
decrease of the temperature, by means of which the antenna responds to changes in the
interference fringes It can be dependent as a function of the temperature T, so that the signal is
always recorded near the same pressure antinode.
In a preferred embodiment of the method according to the invention, the transmission frequency
is fixed and the signal is recorded at the exit plane of the moveable wrapper along the axis of the
paraboloid, the displacement of this wrapper being the theory in the standing wave pattern
Correspond to the shift-generated according to the law as a function of T2 to work. In this case,
the shift of the outlet plane of the wrapper according to this law, expressed as a function of the
relative change Δx Vi temperature change ΔT of the pressure antinode on the abscissa, is the
movement of the hydraulic jack It is preferable that the oil reservoir of this jack acts as a
temperature sensor. In another embodiment, the exit plane of the wrapper remains fixed, for
example at the focal point, and the transmission frequency changes according to the law as a
function of T1 corresponding to a theoretical shift in the fringe pattern Thus, the pressure
antinodes remain fixed in position regardless of changes in temperature. Wavelength λ.
Frequency f equal to the relative change Δλ at The relative change .DELTA.f at is expressed as
follows as a function of the change in temperature, i.e. B-. The temperature changes recorded by
the sensor, placed at the middle of the bottom of the parabolic reflector and the exit plane of the
trumpet, are converted into voltage changes by appropriate electronic circuits, these voltage
changes being the voltage of the conventional product / Converted to frequency change by
frequency converter. In this case, the pass band of the filter whose center frequency is equal to
the transmission frequency is fixed in the first embodiment, and the relative pass band Δf / fo
can filter the signal without attenuation over a predetermined temperature range, ie It is a thing.
In another embodiment, the passband of the filter is centered on the transmission frequency and
follows the change by means of a follow-up system, in which case the filter is of digital type.
While two embodiments of the present invention will be described below with reference to the
accompanying drawings, the manner in which the present invention is practiced should be
clearly understood. Referring to FIG. 1, an antenna 1 of an acoustic radar formed by a parabolic
reflector 2 extending by a hood 3 having a sound absorbing material 4 stretched inside is
diagrammatically illustrated. The transmission chamber 6, for example the compression chamber,
where the wrapper 7 extends, is held on the shaft 5 of the antenna 1 and is aligned with the
surface of the wrapper by rigid connecting means 8, for example a tripod. A theoretical beam 9
of back-reflected sound waves is shown which determines the active area 10 of the antenna 1.
The sound wave generated by the transmission room 6 theoretically runs in the reverse path.
Release! The surface portion 11, which lies on the axis 5 of the J plane, is locally covered by the
presence of the transmission and reception system, and FIG. 2 diagrammatically illustrates the
shift of the fringes 12 as a function of the temperature T. Pressure wave 1! 113 is located at the
focal point in the horizontal axis and shifts over ΔX in response to temperatures T = T, + ΔT,
and the exit plane 15 of the wrapper 7 shifts by the same theoretical quantity, ie EndPage: 3 Do.
FIG. 3 diagrammatically shows the electronic antenna matching means 1. The exit plane 15 of
the wrapper 7 is located at the focal point of the paraboloid in the horizontal axis, and the
transmission frequency f is varied to compensate for theoretical changes in the temperature of
the fringe pattern. When the pressure antinode 13 is established again in the horizontal axis
view, a frequency change Δf is caused with respect to the frequency fo as follows. The various
steps in the conversion of the presentation of the temperature T at the absolute temperature K
provided by the temperature sensor 14 are represented by a block 27. The change in
temperature T is converted as a change in voltage V by a conventional electronic circuit 27A, and
the change in voltage V is converted as a change in frequency f by a conventional voltage /
frequency converter 27B. The changes in this frequency react at the transmit level E by changing
the frequency and at the receive level R by changing the filters so that their respective central
frequencies correspond to the transmit frequency. It is processed in the computer 27C. The
mechanical system, which can be shifted according to a theoretical method of generating a
pattern of interference fringes according to temperature, comprises a hydraulic jack 16 arranged
along the axis of the paraboloid 2 and supported on a fixed base 17. The end 18 of the stud 19 is
aligned with the assembly 20 which is movable along the axis 5 of the paraboloid and includes a
transmission chamber 6 in which the trumpet 7 extends. The entire assembly is supported by a
fixed base 17-a vertical guide which is still supported by a frame formed by two parallel plates
21 and 22 sliding along a column 23 The base is rigidly connected to the parabolic structure by
means of a tripod system 8. The lower parts of the columns 23 are rigidly connected to one
another by means of a plate 24 which is provided with a circular hole 25 in which the movable
assembly 20 can pass freely. The chamber of the hydraulic jack 14 communicates with a coil 26
made of copper or other good heat-conducting material forming a temperature sensor, which is
schematically illustrated at 14 in FIG. .
The total volume of 16 and 26 is F for the rod 19 of the jack 16 F (a fixed distance, ie a movable
volume), for a temperature change ΔT at the level of the wrapper 70.
4. Brief description of the drawings Fig. 1 is a schematic axial sectional view of a conventional
antenna. FIG. 2 is a diagram of the interference fringe phenomenon that occurs between the
bottom of the paraboloid and the exit plane of the trumpet. FIG. 3 is a block diagram of an
antenna matching system using electronic means. 13-Fig. 4 is a diagram of an antenna Sengtai
system according to another embodiment using mechanical means 3, 4 I Jade j 1 person: Bertan,
Work, Compani agent: Patent attorneys Kaizu Hosomoto: Patent attorney Yamakawa Mashikima:
Patent Attorney Kurokawa Hiroma: Attorney Hirayama-Yuki 14-EndPage: 4
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