阅读说明：本技术 具有海平面波特性确定的风力涡轮机 (Wind turbine with sea level wave characteristic determination ) 是由 E·纳格尔 J·妞文豪曾 于 2020-03-13 设计创作，主要内容包括：本发明涉及一种风力涡轮机(1),其被配置为设置在海床(S)中或海床(S)上方。风力涡轮机(1)包括：塔架(2),其被配置为从海平面(S)突出,并且具有被配置为传送要在海平面(S)上反射的电磁波(100)的传送器(20,20A；30),和被配置为接收反射电磁波(200)的接收器(20,20B；40),其中传送器(20,20A；30)和接收器(20,20B；40)中的至少一个包括泄漏馈送部(20)；和处理单元(7),其与接收器(20,20B；40)进行通信并且被配置为分析反射电磁波(200),使得确定海平面(S)的波特性。(The invention relates to a wind turbine (1) configured to be arranged in or above a seabed (S). The wind turbine (1) comprises: a tower (2) configured to protrude from the sea level (S) and having a transmitter (20, 20A; 30) configured to transmit electromagnetic waves (100) to be reflected on the sea level (S) and a receiver (20, 20B; 40) configured to receive the reflected electromagnetic waves (200), wherein at least one of the transmitter (20, 20A; 30) and the receiver (20, 20B; 40) comprises a leakage feed (20); and a processing unit (7) in communication with the receiver (20, 20B; 40) and configured to analyze the reflected electromagnetic wave (200) such that a wave characteristic of sea level (S) is determined.)

1. A wind turbine (1) configured to be arranged in or above a seabed (S), the wind turbine (1) comprising:

a tower (2) configured to protrude from a sea level (S) and having a transmitter (20, 20A; 30) configured to transmit electromagnetic waves (100) to be reflected on the sea level (S) and a receiver (20, 20B; 40) configured to receive reflected electromagnetic waves (200), wherein at least one of the transmitter (20, 20A; 30) and the receiver (20, 20B; 40) comprises a leakage feed (20); and

a processing unit (7) in communication with the receiver (20, 20B; 40) and configured to analyze the reflected electromagnetic wave (200) such that a wave characteristic of the sea level (S) is determined.

2. Wind turbine (1) according to the preceding claim, wherein

The leakage feed (20, 20A, 20B) is shaped as an arc extending around the circumference of the tower (2).

3. Wind turbine (1) according to any of the preceding claims, wherein

The transmitter (20A, 30) comprises a first leak feed (20A) and the receiver (20B, 40) comprises a second leak feed (20B).

4. Wind turbine (1) according to any of the preceding claims, wherein

The processing unit (7) is configured to determine at least one of a wind speed, a wind direction, a wind forecast, and a vessel approach condition from the determined wave characteristics of the sea level (S), wherein the vessel approach condition is a condition allowing a vessel to approach the wind turbine (1) or to be docked at the wind turbine (1).

5. Wind turbine (1) according to the preceding claim,

the processing unit (7) is configured to determine the vessel approach condition in dependence of the determined wave characteristics of the sea level (S) and in dependence of the load of the vessel.

6. Wind turbine (1) according to any of the preceding claims, wherein

The processing unit (7) is configured to determine a target distance between the wind turbine (1) and a vessel from the determined wave characteristics of the sea level (S).

7. Wind turbine (1) according to any of the preceding claims, wherein

The processing unit (7) is configured to determine the wave characteristic based on an angle of a reflection plane (R) of the sea level (S) with respect to a horizon (H).

8. Wind turbine (1) according to any of the preceding claims, wherein

The processing unit (7) is configured to use Bragg's law in determining the wave characteristicsWherein

d is the distance between two peaks or the peak-to-peak height of the waves at sea level (S),

theta is the scattering angle of the reflected electromagnetic wave (200) with respect to the horizontal line (H),

is the wavelength of said electromagnetic wave (100, 200), and

n is a positive integer.

9. A method of determining wave characteristics of sea level (S), the method comprising the steps of:

providing a tower (2) of a wind turbine (1), the tower (2) protruding from a sea level (S), having a transmitter configured to transmit electromagnetic waves (100) to be reflected on the sea level (S) and a receiver configured to receive reflected electromagnetic waves (200), wherein at least one of the transmitter and the receiver comprises a leakage feed (20);

analyzing the reflected electromagnetic wave (200); and

determining wave characteristics of the sea level (S) based on the analyzed reflected electromagnetic waves (200).

10. The method according to the preceding claim, further comprising the step of:

determining at least one of a wind speed, a wind direction, a wind forecast and a vessel approach condition from the determined wave characteristics of the sea level (S), wherein the vessel approach condition is a condition allowing a vessel to approach the wind turbine (1) or to be docked at the wind turbine (1).

11. The method according to the preceding claim, wherein

Determining the vessel approach condition based on the determined wave characteristics of the sea level (S) and based on the load of the vessel.

12. The method according to any of the preceding claims 9 to 11, further comprising the step of:

determining a target distance between the wind turbine (1) and the vessel from the determined wave characteristics of the sea level (S).

13. The method according to any of the preceding claims 9 to 12, wherein

Determining the wave characteristic based on an angle of a reflection plane (R) of the sea level (S) with respect to a horizon (H).

14. The method according to any of the preceding claims 9 to 13, wherein

By using Bragg's lawTo determine said wave characteristics, wherein

d is the distance between two peaks or the peak-to-peak height of the waves at sea level (S),

theta is the scattering angle of the reflected electromagnetic wave (200) with respect to the horizontal line (H),

is the wavelength of said electromagnetic wave (100, 200), and

n is a positive integer.

15. The method according to any of the preceding claims 9 to 14, wherein

The signals of wave characteristics are directly measured by radar to obtain a 360 ° image around the wind turbine (1) and/or its supporting structure, in particular by using synthetic aperture radar SAR and/or inverse synthetic aperture radar ISAR algorithms.

16. The method according to any of the preceding claims 9 to 15, wherein

The radar SDR is defined using software.

Technical Field

The present invention relates to the field of wind turbines. In particular, the invention relates to a wind turbine capable of determining wave characteristics of the sea level in which the wind turbine is placed.

Background

In the above defined technical field, some radar applications, such as LIDAR (light detection and ranging) and conventional weather measuring stations around wind turbines are used for measuring and predicting wind conditions. However, the accuracy and robustness of conventional solutions can still be improved.

Disclosure of Invention

It is an object of the invention to provide a wind turbine and a method of determining sea level wave characteristics which are more accurate and more robust. This object is achieved by the subject matter of the independent claims. The invention is further developed as defined in the dependent claims.

According to a first aspect of the invention, a wind turbine is configured to be arranged in or above a sea bed and comprises a tower configured to protrude from sea level and having a transmitter configured to transmit electromagnetic waves to be reflected on the sea level and a receiver configured to receive the reflected electromagnetic waves, wherein at least one of the transmitter and the receiver comprises a leakage feed. The wind turbine further comprises a processing unit in communication with the receiver and configured to analyze the reflected electromagnetic waves such that sea level wave characteristics are determined. The sea level wave characteristic may be the height or velocity of the wave in the sea level.

There is a significant advantage of the wind turbine of the present invention in that the side lobes of the antenna gain pattern can be reduced by the leakage feed at the turbine tower. Conventionally, side lobes cause problems in signal processing. In addition to this, the coverage of the leakage feed may extend to about 360 ° around the turbine tower.

The leakage feed is easy to install, robust, sensitive and cheap. For example, the leak feed may be made of a cable, which is a commercially available cable and is easy to handle and install. There are no optical parts that can be contaminated.

In addition to this, the closed loop control of the wind turbine may be influenced by the determined sea level wave characteristics, in particular if the wind turbine is floating and not ground based.

Preferably, the leakage feed is shaped as an arc extending around the circumference of the tower. The arc may extend over a range of at least 360 °. Preferably, the transmitter comprises a first leak feed and the receiver comprises a second leak feed.

Preferably, the processing unit is configured to determine at least one of a wind speed, a wind direction, a wind forecast, and a vessel approach condition from the determined sea level wave characteristics, wherein the vessel approach condition is a condition allowing the vessel to approach or dock at the wind turbine. More preferably, the processing unit is configured to determine a vessel approach condition based on the determined sea level wave characteristic and based on a load of the vessel. Furthermore, the processing unit is configured to determine a target distance between the wind turbine and the vessel from the determined sea level wave characteristics.

With respect to the vessel access condition, a determination may be made, for example, with maintenance/service personnel, as to whether the vessel is able to access or land near the wind turbine. This determination may avoid inefficient docking of the vessel with the wind turbine when the situation is not good.

Preferably, the processing unit is configured to determine the wave characteristics based on an angle of a reflection plane of the sea level with respect to a horizon. Preferably, the processing unit is configured to use bragg's law in determining the wave characteristicsWhere d is the distance between two peaks or the peak-to-peak height of the sea plane wave, θ is the scattering angle of the reflected electromagnetic wave with respect to the horizontal line,is the wavelength of the electromagnetic wave, and n is a positive integer.

The leakage feed may provide a full 360 ° image around the wind turbine and its support structure, such as a mono pile, a floating support structure or any other support structure. For example, SAR (synthetic aperture radar) and/or ISAR (inverse synthetic aperture radar) algorithms may be used to obtain a 360 ° sea level high resolution image. Particularly by ISAR techniques, the movement of individual waves in sea level can be tracked and used to generate images.

The following parameters can be derived: basic sea level height, individual wave height, wave distance from the tower, wave speed, wave direction, wave size, wave shape, wave acceleration and deceleration, wave breaking on the wind turbine support structure, number of waves per distance, etc.

The following radar parameters/principles may be used: TOF (time of flight), doppler information, ultra wideband radar, and other radar technologies.

Furthermore, by using SDR (software defined radar), a complete sensing of the volume surrounding the wind turbine and/or its supporting structure can be achieved. SDR is a multifunctional radar system in which most of the processing (e.g., signal generation, filtering, up-and down-conversion, etc.) can be performed and adjusted by software. The SDR may produce any desired modulation scheme optimized for the application. The output power of the SDR may be dynamically adjusted to optimize range and spatial resolution. Such data capture may support the prediction and calculation of the mechanical load of the wave forces towards the wind turbine and its supporting structure. With knowledge of these loads, the integration of data can be applied in the regulation of the wind turbine. Furthermore, the generated data is used as an auxiliary data source for the condition monitoring system, for example by means of sensor fusion, wherein the sensing data or data derived from different sources are combined to reduce uncertainty.

According to a second aspect of the invention, a method of determining sea level wave characteristics comprises the steps of: providing a tower of a wind turbine protruding from sea level, the tower having a transmitter configured to transmit electromagnetic waves to be reflected on sea level and a receiver configured to receive the reflected electromagnetic waves, wherein at least one of the transmitter and the receiver comprises a leakage feed; analyzing the reflected electromagnetic wave; and determining a sea level wave characteristic based on the analyzed reflected electromagnetic wave.

Preferably, the method further comprises the step of determining at least one of a wind speed, a wind direction, a wind forecast, and a vessel approach condition from the determined sea level wave characteristics, wherein the vessel approach condition is a condition allowing the vessel to approach or dock at the wind turbine. More preferably, the vessel approach condition is determined from the determined sea level wave characteristic and from the load of the vessel.

Preferably, the method further comprises the step of determining a target distance between the wind turbine and the vessel from the determined sea level wave characteristics.

Preferably, the wave characteristics are determined based on the angle of the reflection plane of the sea level with respect to the horizon. Preferably by using Bragg's lawTo ensureA stationary wave characteristic, where d is the distance between two peaks or the peak-to-peak height of a sea plane wave, θ is the scattering angle of the reflected electromagnetic wave with respect to the horizontal line,is the wavelength of the electromagnetic wave, and n is a positive integer.

Preferably, the signals of wave characteristics are directly measured by radar to obtain a 360 ° image around the wind turbine and/or its supporting structure, in particular by using synthetic aperture radar SAR and/or inverse synthetic aperture radar ISAR algorithms.

Preferably, a software defined radar SDR is used.

The above method may achieve the same advantages as the wind turbine according to the invention.

Drawings

The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

FIG. 1 shows a schematic cross section of a wind turbine according to an embodiment of the invention.

Fig. 2 shows a schematic view of an unfolded leak feed according to an embodiment of the invention.

FIG. 3 shows a cross-sectional view of a tower and a leakage feed according to an embodiment of the invention.

Fig. 4 shows a schematic view of an unfolded leak feed according to an embodiment of the invention, where a plurality of leak feeds are used.

Fig. 5 shows a configuration of a leak feeder and a processing unit according to an embodiment of the present invention.

Fig. 6 shows details of a processing unit according to another embodiment of the invention.

Fig. 7 illustrates the principle of analyzing reflected electromagnetic waves so as to determine sea level wave characteristics according to an embodiment of the present invention.

Detailed Description

The illustration in the drawings is schematically. Note that in different figures, similar or equivalent elements are provided with the same reference signs.

Fig. 1 shows a schematic cross section of a wind turbine 1 according to an embodiment of the invention. The wind turbine 1 is configured to be arranged in or above the seabed (offshore). The wind turbine 1 is supported by a support structure (not shown), such as a mono pile or a floating support structure. Any other support structure may be used. The wind turbine 1 comprises a tower 2, which tower 2 is mounted on a not depicted foundation to protrude from the sea level S. The wind turbine 1 may also be arranged above the seabed S in a floating manner. The nacelle 3 is arranged on top of the tower 2. Between the tower 2 and the nacelle 3 a yaw angle adjustment device (not shown) is provided, which is capable of rotating the nacelle around a vertical yaw axis z. The wind turbine 1 further comprises a wind rotor 5 with one or more rotating blades 4 (in the perspective view of fig. 1 only two blades 4 are visible). The wind rotor 5 is rotatable about an axis of rotation Y. In general, when not indicated differently, the terms axial, radial and circumferential are made hereinafter with reference to the axis of rotation Y. The blades 4 extend radially with respect to the rotation axis Y. The wind turbine 1 comprises a generator 6 with a stator 11 and a rotor 12. The rotor 12 is rotatable about a rotation axis Y with respect to the stator 11 to generate electric power. The generator 6 and the generation of electricity by the present invention are not a specific object of the present invention and are therefore not described in further detail.

Basically, the tower 2 has transmitters 20, 30 configured to transmit electromagnetic waves 100 to be reflected on the sea level S and receivers 20, 40 configured to receive the reflected electromagnetic waves 200, wherein at least one of the transmitters and receivers comprises a leakage feed 20. In the embodiment of fig. 1, the tower 2 has a leakage feed 20, in which the functions of both a transmitter and a receiver are realized. Other embodiments may use a first leakage feed for transmitting electromagnetic waves and a second leakage feed for receiving reflected electromagnetic waves, which will be described later.

The wind turbine 1 further comprises a processing unit 7 (fig. 5), the processing unit 7 and the receivers 20, 40Communicating and configured to analyze the reflected electromagnetic wave 200 such that wave characteristics of the sea level S are determined. The wave characteristic of the sea level S may be the height or velocity of the waves in the sea level S. The processing unit 7 may determine the altitude and movement (velocity) of the wave at sea level S due to or by the time of flight, the angle of flight and/or the doppler effect of the reflected electromagnetic wave 200. For example, the time of flight of the reflected electromagnetic wave 200Can be calculated asWherein c is₀Is the speed of light. The distance d between the receivers 20, 40 to the wave at sea level S where the electromagnetic wave 200 has been reflected is then calculated as。

The leakage feed 20 is an elongated member that leaks the electromagnetic wave 100 along the member. The leaky feeder 20 may be constituted by a leaky coaxial cable or a leaky waveguide or a leaky stripline. The leakage feed 20 is connected to the electromagnetic transmitter drive 30 for transmitting the first electromagnetic signal 100 along the leakage feed 20 towards sea level. The electromagnetic transmitter driver 30 may comprise or be an HF amplifier. The leakage feed 20 comprises a plurality of slots to allow the first electromagnetic signal 100 to leak out of the leakage feed 20 along the entire length of the leakage feed 20 towards the sea level S. According to a possible embodiment, the slots may be regularly distributed along the length of the leakage feed 20. According to other possible embodiments of the invention, the leakage feed 20 is a normal coaxial cable with a low optical coverage of the outer conductor (mesh or slot/aperture), which also leaks electromagnetic waves.

The leak feed 20 may be provided with a heating system (not shown) if severe over-icing conditions are possible. The heating may be provided by air flowing between the inner and outer conductors or by current running in the inner or outer conductor of the leakage feed 20.

According to a possible embodiment, the first electromagnetic signal 100 may be a radar signal, such as a multi-frequency radar or LIDAR or an ultrasound signal. In case the first electromagnetic signal 100 is a radar signal or an ultrasonic signal, the leakage feed 20 is preferably configured as a coaxial leakage cable.

According to other embodiments, especially in case the first electromagnetic signal 100 has a higher frequency, the leaky feeder 20 is preferably configured as a leaky waveguide. In general, first electromagnetic signal 100 may have any frequency, as long as it can be transmitted to and reflected by sea level S, according to various embodiments of the present invention.

When the first electromagnetic signal 100 hits the sea level S, the reflected second electromagnetic signal 200 is transmitted towards the leakage feed 20.

The plurality of slots of the leakage feed 20 allow the second electromagnetic signal 200 to leak into the leakage feed 20 towards the electromagnetic converter 40.

The processing unit 7 in communication with the electromagnetic converter 40 analyses the second electromagnetic signal 200 (and, if necessary, the first electromagnetic signal 100) for determining the wave characteristics of the sea level S.

Fig. 2 shows a schematic view of an unfolded leak feed according to an embodiment of the invention. This embodiment uses only one leak feed 20. The leak feed 20 extends between a first end 21 and a second end 22. The first end 21 is connected to an electromagnetic transceiver 45, the electromagnetic transceiver 45 comprising an electromagnetic transmitter driver 30 and an electromagnetic transducer 40. The second terminal 22 is connected to a final resistor 50. According to an embodiment of the invention, both the electromagnetic transmitter driver 30 and the electromagnetic converter 40 may be connected to the first end 21 or the second end 22 via a signal splitter or a y-adapter. According to other embodiments of the present invention, an electromagnetic transmitter driver 30 is connected to the first end 21 and an electromagnetic converter 40 is connected to the second end 22.

In some cases, if a single leakage feed 20 is used, the determined wave characteristics of the sea level S may have uncertainty if the electromagnetic transmitter 30 and the electromagnetic receiver 40 are at the same end 21 or 22. Therefore, it is preferred if the electromagnetic transmitter 30 is at one end of the leakage feed 20 and the electromagnetic receiver 40 is on the other end of the leakage feed 20.

The leaky feeder 20 may not be directly connected to the electromagnetic transmitter driver 30 and the electromagnetic receiver converter 40, for example, a non-leaky feeder cable (i.e., a common coaxial cable) may be interposed between the leaky feeder 20 and the electromagnetic transmitter driver 30 and/or the electromagnetic receiver converter 40. A common coaxial cable may be directly connected to electromagnetic transmitter driver 30 and electromagnetic receiver transducer 40, or it may be used for interconnection.

The leak feeder 20 shown in a developed state in fig. 2 is geometrically practically configured in an arc shape of approximately 360 ° or more.

Fig. 3 shows a cross-sectional view of the tower 2 and the leakage feed 20 according to an embodiment of the invention. The leakage feed 20 is shaped as an arc extending around the circumference of the tower 2, i.e. the leakage feed 20 is geometrically configured as a circular ring around the tower 2 or the wind turbine support structure. The leakage feed 20 can thus transmit the electromagnetic wave 100 or receive the reflected electromagnetic wave 200 around an angle of 360 °.

According to other embodiments of the invention, any other geometrical configuration is possible as long as the first electromagnetic signal 100 may be transmitted towards the sea level S and the second electromagnetic signal 200 may be reflected by the sea level S towards the leakage feed 20.

The leakage feed 20, the electromagnetic transmitter drive 30 and the electromagnetic receiver transducer 40 are mounted on the tower 2. According to other embodiments of the invention, the leakage feed 20, the electromagnetic transmitter driver 30 and the electromagnetic receiver converter 40 may not be mounted directly on the wind turbine 1, i.e. remote from the wind turbine 1.

Fig. 4 shows a schematic view of an unfolded leak feed 20A, 20B according to an embodiment of the invention, wherein a plurality of leak feeds 20A, 20B are used. The embodiment of fig. 4 uses two leak feeds 20A, 20B, which are parallel to each other and extend between the respective first and second ends 21, 22, respectively, adjacent to each other. The two leakage feeds 20A, 20B are configured according to an anti-parallel configuration, wherein the first leakage feed 20 extends between the electromagnetic transmitter driver 30 connected to the first end 21 and the final resistance 50 connected to the second end 22; while the second leakage feed 20 extends between a final resistor 50 connected to the first end 21 and the electromagnetic receiver transducer 40 connected to the second end 22.

In such embodiments, the first leakage feed 20A connected to the electromagnetic transmitter driver 30 is dedicated to the transmission of the first electromagnetic signal 100, while the second leakage feed 20B connected to the electromagnetic receiver transducer 40 is dedicated to the reception of the first electromagnetic signal 200.

Fig. 5 shows the configuration of the leak feeders 20A, 20B and the processing unit 7 according to an embodiment of the present invention. The receiver converter 40 may be an analog-to-digital converter (a/D). The reflected and analog second electromagnetic signal 200 may be received from the leakage feed 20A and converted to a digital signal by the a/D converter 40. The digital signal is then transmitted to a Central Processing Unit (CPU) 71. The CPU 71 actually analyzes the received second electromagnetic signal 200 and determines the wave characteristics of the sea level S based on the analyzed second electromagnetic signal 200. The CPU 71 is further connected to storage devices such as a RAM 72 and a hard disk (HDD) 73. The CPU 71 is further connected to a communication unit (not shown) by means of which the determined wave characteristics of the sea level S can be transmitted to a control and/or monitoring system (not shown). Preferably, the communication is via wire, optical fiber or wireless.

Fig. 6 shows details of the processing unit 7 according to another embodiment of the invention. The CPU 71 includes a filter 711 and a fast fourier transform unit (FFT unit) 712, the filter 711 filtering the digital signal from the receiver converter 40, and the fast fourier transform unit 712 performing, for example, one or two fast fourier transform operations on the filtered signal. The CPU 71 is further connected to the storage device 75 and the electromagnetic transmitter driver 30 of the leak feeder 20A that performs transmission, to control it.

In addition to or as an alternative to the FFT unit 712, a signal processing unit may be provided by which the time and frequency domain data may be analyzed to determine wave characteristics of the sea level S.

Preferably, the processing unit 7 is configured to determine at least one of a wind speed, a wind direction and a wind forecast from the determined wave characteristics of the sea level S.

Preferably, the processing unit 7 is configured to determine a vessel approach condition from the determined wave characteristics of the sea level S, wherein the vessel approach condition is a condition allowing the vessel to approach the wind turbine 1. A determination may then be made, for example together with maintenance/service personnel, as to whether the vessel is able to dock or land close to the wind turbine 1. For example, if the determined wave characteristic (such as wave height, wave speed or wind speed) exceeds a predetermined threshold, a determination is made that the vessel is not allowed to approach the wind turbine 1, dock or land near the wind turbine 1. More preferably, the processing unit 7 is configured to determine the vessel approach condition from the determined wave characteristics of the sea level S and further from the load of the vessel. The processing unit 7 may be configured to determine a target distance between the wind turbine 1 and the vessel from the determined wave characteristics of the sea level S. Based on the determined target distance between the wind turbine 1 and the vessel, an automatic control of the distance between the wind turbine 1 and the vessel may be achieved. Alternatively, the crew of the vessel may be supported in navigating the vessel by communicating the determined target distance between the wind turbine 1 and the vessel to the crew.

Fig. 7 illustrates the principle of analyzing the reflected electromagnetic wave 200 such that the wave characteristics of the sea level S are determined, according to an embodiment of the present invention. The wave characteristics of the sea level S are indirectly measured by the wave height of the sea level S around the wind turbine 1. The wind induces waves in the sea level S. The stronger the wind, the higher the wave and the distance between the peaks increases. It has been found that there is a correlation between the wind speed/direction and the direction of the reflected electromagnetic wave 200. In more detail, the electromagnetic wave 100 (e.g., radar signal 100) is reflected by waves in the sea level S. In fig. 7 is schematically shown the use of bragg's lawWhere d is the distance between two peaks of the sea level S and theta is the reflected electromagnetic wave200 relative to the horizontal line H,is the wavelength of the electromagnetic wave 100, 200 and n is a positive integer generally indicating a diffraction order.

The top view in fig. 7 shows a low wind condition, while the bottom view in fig. 7 shows a high wind condition. The top view in fig. 7 shows the reflection plane R of the sea level S with a smaller angle with respect to the horizontal H, whereas the top view in fig. 7 shows the reflection plane R of the sea level S with a larger angle with respect to the horizontal H. The scattering angle θ changes based on the angle of the reflection plane R.

The reflection angle of the reflected electromagnetic wave 200 with respect to the horizontal line H is different depending on the distance d of the wave. This effect is known as the bragg effect or bragg reflection and can be used in the field of meteorology to make calculations of wind speed or wind direction.

To calculate wind speed and direction, first and second order bragg peaks must be studied. The leakage feed 20 itself operates in a frequency band in which the wavelengths areIn the range d, this range d is either the distance between two peaks or the peak-to-peak height of the waves at sea level S. Multi-frequency radar and also the doppler effect of moving waves in the sea level S can be used. For calculating the wind speed, first-order backscatter is used, whereinAs the wavelength. To estimate wind direction, two first order scatterings may be used. Typical frequencies of the electromagnetic wave 100 are 7.5 to 25 Mhz. This provides an electromagnetic (radar) transmitter driver 30 in the range of several kilometres with sufficient power.

Frequency modulated discontinuous continuous wave (FMIC) radar may be used for this type of weather radar.

The "Wind direction measurement using HF ground radial base on a circular receiver array" by C, ZHAO et al, published in 2017 Progress in electromagnetic Research Symposium (Singapore, 2017), discloses some more advanced measurement algorithms. For example, the wind direction may be calculated by the ratio of two first order bragg reflections.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.