Patent Description:
Knowledge of wind conditions is important for a number of human activities, both in professional and in recreational fields. In this regard, accurate and reliable measurement of wind speed and wind direction is essentially important for example in aviation and marine operations as well as in industrial contexts such as energy production by wind turbines. One of the techniques currently applied for measurement of wind speed and wind direction in such professional contexts involves measurement of time of flight of a sound signal using a dedicated measurement apparatus that comprises one or more pairs of a transmitter and a receiver. In such a measurement apparatus each pair of a transmitter and receiver may serve to provide a respective measurement path, whereas three or more measurement paths are typically considered as a requirement for reliable measurement of the wind speed and wind direction. Typically, increasing number of measurement paths results in increased accuracy and reliability of the measurement, whereas increasing the number of measurement paths typically also increases the number of components required for the measurement apparatus, which in turn typically result in increasing structural complexity and increasing manufacturing cost of the measurement apparatus.

In related art, <CIT> discloses a supersonic wind speed measuring device which comprises a seat and at least one measurement unit. The seat comprises at least one ventilation space, the measurement unit is arranged in the ventilation space correspondingly, and comprises supersonic sensing members and one supersonic emitter, the supersonic sensing members surround one central point, and include multiple micro electromechanical energy transducers, the position of the supersonic emitter corresponds to the central point, and the supersonic emitter also comprises multiple micro electromechanical energy transducers; and the micro electromechanical energy transducers of the supersonic emitter and those of each supersonic sensing member are the same in structure.

Further in related art, <CIT> discloses an airflow parameter measuring device and method. The airflow parameter measuring device comprises a processor, an ultrasonic transmitting head serving as a center and at least three receiving ends which are annularly arranged, surround the center and have an ultrasonic receiving function. On one hand, the receiving end with the ultrasonic wave receiving function is adopted, the receiving end is sensitive in response to weak airflow such as breeze and the like, airflow parameters in the breeze and strong wind range can be measured, the measurement range is large, the measurement precision is high, and measurement can be conducted in the low-temperature environment and the rainy and snowy weather environment; in addition, a receiving end with an ultrasonic wave receiving function, such as a silicon microphone, is adopted, and the cost and the size can be greatly reduced, so that the airflow parameter measuring device disclosed by the invention greatly reduces the cost and the size under the condition of ensuring the measuring precision and the measuring range.

Further in related art, <CIT> discloses an ultrasonic wind gauge and a method for determining at least one property of incident wind, having at least one transmitter for emitting sound waves and at least one receiver for at least partially receiving the emitted sound waves and having an evaluation unit which determines the at least one property of the incident wind on the basis of a recorded transit time of the sound waves between the transmitter and the receiver. The technical solution described is distinguished by the fact that the transmitter and the receiver are arranged in such a manner that at least two receivers at least partially receive the sound waves emitted by a transmitter and the simple transit time of the sound waves between the one transmitter and the at least two receivers is taken as a basis in each case for determining at least one property of the incident wind in the evaluation unit.

Further in related art, <CIT> discloses a reflection type ultrasonic anemograph and a wind speed detection method. The reflection type ultrasonic anemograph comprises a base, transducers, supporting columns, a reflector and an analysis unit. The transducers are arranged on the base, and the reflector is located on the upper side of the base and is provided with a concave reflecting surface; the supporting columns are arranged between the base and the reflector, and the supporting columns are arranged between the adjacent transducers; the four transducers and the four supporting columns are arranged on the base, the supporting columns and the energy converters are alternately arranged, and on the base, the corresponding central angles of the adjacent supporting columns and transducers are all <NUM> degrees; and the calculation unit is used for obtaining corrected wind speed according to the calculated wind speed output by the analysis unit.

It is an object of the present invention to provide a wind measurement apparatus that is relatively simple in structure but that yet enables accurate, reliable and robust measurement of wind speed and wind direction.

According to an example embodiment, a wind measurement apparatus is provided, the apparatus comprising: a cover portion and a base portion arranged at a distance from each other to allow for an airflow therebetween; an arrangement of N receivers disposed on a base-portion-facing side of the cover portion in respective positions that serve as respective vertices of a convex regular polygon of order N, where N is at least three; a transmitter disposed on the base-portion facing side of the cover portion in a position that is at a substantially equal distance from each of the N receivers; and a reflector assembly arranged on a cover-portion-facing side of the base portion, wherein the reflector assembly is divided into N concave reflector portions, wherein each receiver is associated with one of the reflector portions and wherein the reflector assembly and the base portion are disposed with respect to each other such that the transmitter is spatially aligned with a center point of the reflector assembly and that each receiver is spatially aligned with the associated reflector portion, wherein the transmitter is arranged to transmit an ultrasonic measurement signal in a transmitter beam, TX beam, towards the reflector assembly such that the TX beam meets each of the reflector portions, wherein each of the receivers is arranged to receive, via the associated reflector portion, a reflection of a TX beam portion that meets the respective reflector portion, wherein said measurement signal comprises an ultrasonic measurement signal and wherein the apparatus further comprises a control portion arranged to: operate the transmitter to transmit the measurement signal in the TX beam, operate each of the N receivers to capture the respective reflected measurement signal received in the reflections of the respective TX beam portions, and derive one or more wind characteristic based on respective propagation times of the respective reflected measurement signals captured at the N receivers.

The exemplifying embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" and its derivatives are used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features described in the following description of some example embodiments of the present invention may be used in combinations other than the combinations explicitly described unless explicitly stated otherwise.

Some features of the invention are set forth in the appended claims. Aspects of the invention, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of some example embodiments when read in connection with the accompanying drawings.

<FIG> schematically illustrate some components of a wind measurement apparatus <NUM> according to a first example. The wind measurement apparatus <NUM> comprises a cover portion <NUM> and a base portion <NUM> arranged at a distance from each other to form a gap that allows for an airflow through a measurement volume provided between the cover portion <NUM> and the base portion <NUM>. In the first example, the cover portion <NUM> comprises an arrangement of a single transmitter <NUM> and three receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> disposed on its base-portion-facing side (e.g. on its base-portion-facing surface), whereas the base portion <NUM> comprises a reflector assembly <NUM> arranged on a cover-portion-facing side (e.g. on the cover-portion-facing surface) of the base portion <NUM>. In operation of the wind measurement apparatus <NUM>, the transmitter <NUM> may transmit a measurement signal towards the reflector assembly <NUM> and each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may receive respective reflections of the measurement signal originating from the transmitter <NUM> from the reflector assembly <NUM>, thereby enabling measurement of characteristics (such as speed and direction) of the airflow passing through the gap between cover portion <NUM> and the base portion <NUM>. The wind measurement apparatus <NUM> may be also referred to as an anemometer apparatus and it may be applicable for measuring one or more wind characteristics, such as wind speed and wind direction, via usage of acoustic measurement signals transmitted from the transmitter <NUM> and received at the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, thereby implementing acoustic wind measurement.

The schematic illustration of <FIG> provides a `side view' to the wind measurement apparatus <NUM> according to the first example, showing the cover portion <NUM> and the base portion <NUM> together with the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> arranged on the base-portion-facing side of the cover portion <NUM>. The illustration of <FIG> does not show the transmitter <NUM> since it is located behind the receiver <NUM>-<NUM> in the illustration. The base portion <NUM> may be attached to the cover portion <NUM> via a plurality of support elements (not shown in the illustration of <FIG>). The distance between the cover portion <NUM> and the base portion <NUM> is dependent on a spatial arrangement of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in consideration of characteristics of the reflector assembly <NUM>. This aspect of the wind measurement apparatus <NUM> is described in further detail in the examples provided in the following.

<FIG> schematically illustrates the base-portion-facing side of the cover portion <NUM> according to the first example, showing the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> arranged in the cover portion <NUM> such that their respective front faces are substantially facing the reflector element <NUM> provided on the cover-portion-facing side of the base portion <NUM>. The receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be disposed at respective positions that correspond to respective vertices of a (conceptual) equilateral triangle arranged on the base-portion-facing side of the cover portion <NUM>, thereby constituting a trilaterally symmetrical arrangement of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> on the base-portion-facing side of the cover portion <NUM>, where respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> define a reference plane. The transmitter <NUM> may be arranged in a position that is at a substantially equal distance from each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. In this regard, the transmitter <NUM> may be disposed on an axis that meets the reference plane in a normal angle substantially at the center point of the (conceptual) equilateral triangle formed by the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. As an example, the transmitter <NUM> may be disposed substantially on the reference plane, whereas in other examples the transmitter <NUM> may be (sightly) offset from the reference plane, either towards the base portion <NUM> or further away from the base portion <NUM>.

As another way of specifying the arrangement of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be disposed at respective positions that are evenly spread (i.e. evenly spaced) on a (conceptual) circle on the base-portion-facing side of the cover portion <NUM>, whereas the transmitter <NUM> may be disposed on an axis that meets the reference plane defined by the respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in a normal angle substantially at the center point of said circle.

The distances between the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be chosen in view of the intended usage of the wind measurement apparatus <NUM> and/or on any requirements or constraints set for the size of the wind measurement apparatus <NUM>. In non-limiting examples, the diameter of the (conceptual) circle at which the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are located may have a diameter from a few centimeters to a few tens of centimeters.

The transmitter <NUM> may be arranged to transmit a transmitter (TX) beam that conveys a measurement signal towards the reflector assembly <NUM> for reflection therefrom and for subsequent reception at the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be arranged to receive, from the direction of the reflector assembly <NUM>, respective partial reflections of the TX beam conveying the measurement signal transmitted from the transmitter <NUM> towards the reflector assembly <NUM>. Aspects related to transmission, reception and characteristics of the measurement signal are described in the examples provided in the following.

<FIG> schematically illustrates the cover-portion-facing side of the base portion <NUM> according to the first example, showing the reflector assembly <NUM> that is divided into three identical reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> that form a trilaterally rotationally symmetrical reflector element. In other words, the reflector assembly <NUM> exhibits rotational symmetry of order three. Hence, the trilaterally symmetrical arrangement of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> on the base-portion-facing side of the cover portion <NUM> and the transmitter <NUM> arranged substantially at the center of the (conceptual) equilateral triangle formed by the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM> together with the trilaterally symmetrical reflector assembly <NUM> arranged on the cover-portion-facing side of the base portion <NUM> constitute a trilaterally symmetrical wind measurement arrangement. Each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may comprise a respective concave surface for reflecting a respective portion of the measurement signal transmitted from the transmitter <NUM> for reception by a respective one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Due to the concave surfaces of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, a respective boundary between each pair of two adjacent reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> forms a respective ridge, whereas the respective ridges between the adjacent reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> meet at a center point of the reflector assembly <NUM> and from an apex. In an example, the reflector assembly <NUM> may be a separate element that is embedded or otherwise attached to the cover-portion-facing side of the base portion <NUM>, whereas in another example the reflector assembly <NUM> may be provided as an integral part of base portion <NUM> e.g. such that the cover-portion-facing surface of the base portion <NUM> or at least part thereof is shaped such that it forms the reflector assembly <NUM>.

In various examples, the measurement signal conveyed in the TX beam transmitted from the transmitter <NUM> may comprise a signal that is characteristic of the transmitter <NUM> or the measurement signal conveyed in the TX beam transmitted from the transmitter <NUM> may comprise a measurement signal supplied to the transmitter <NUM> for transmission therefrom. The TX beam originating from the transmitter <NUM> may be divergent to an extent that depends on characteristics of the transmitter <NUM>.

The measurement signal conveyed in the TX beam transmitted from the transmitter <NUM> may comprise an ultrasonic signal and, hence, the transmitter <NUM> may comprise an ultrasonic transmitter or an ultrasonic transducer arranged to transmit the ultrasonic signal, whereas each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may comprise a respective ultrasonic receiver or a respective ultrasonic transducer arranged to receive at least a portion of the ultrasonic signal transmitted from the transmitter <NUM>. As a non-limiting example in this regard, each of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be provided as a respective piezoelectric transducer, e.g. as respective cylindrical piezoelectric transducers that radiates a relatively wide TX beam and receive a relatively wide receiver (RX) beam or as respective linear piezoelectric transducers that radiates a relatively narrow TX beam and receive a relatively narrow RX beam. Usage of the linear piezoelectric transducers may be advantageous in that they provide a cost-effective solution while providing TX and RX beams of sufficient width in view of certain advantageous characteristics of the reflector assembly <NUM> that includes the concave reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (which are described in further detail in the following).

Along the lines described in the foregoing, each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> is arranged to reflect a respective portion of the TX beam originating from the transmitter <NUM> towards a respective one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. In this regard, the reflector portion <NUM>-<NUM> may be provided for reflecting the respective portion of the TX beam towards the receiver <NUM>-<NUM> and hence the reflector portion <NUM>-<NUM> may be referred to as a reflector portion that is associated with the receiver <NUM>-<NUM> and, conversely, the receiver <NUM>-<NUM> may be referred to as a receiver that is associated with the reflector portion <NUM>-<NUM>. Similar relationship applies for the reflector portion <NUM>-<NUM> and the receiver <NUM>-<NUM> as well as for the reflector portion <NUM>-<NUM> and the receiver <NUM>-<NUM>, mutatis mutandis.

The schematic illustration of <FIG> further shows a projected position of the transmitter <NUM> on the reflector assembly <NUM> and respective projected positions <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in relation to the arrangement of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> of the reflector assembly <NUM>. As shown in the illustration, the center point of the arrangement of receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the center point of the reflector portion <NUM> are spatially aligned with each other, thereby also spatially aligning the transmitter <NUM> with the center point of the reflector element <NUM>. Moreover, each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be spatially aligned with the reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated therewith, e.g. such that the each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> is spatially aligned with a respective (conceptual) radial line segment that extends from the center point of the reflector assembly <NUM> towards the perimeter of the reflector assembly <NUM> and that bisects the reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated therewith. In the present text, the term 'bisect' is applied to mean division into two parts of substantially equal size. As an example in this regard:.

Consequently, each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> gets spatially aligned with a respective reference position that is at a predefined distance from the center point of the reflector assembly <NUM> and located on the (conceptual) radial line segment that bisects the reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated therewith, where the predefined distance is substantially the same as the distance between any of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the center point of the (conceptual) equilateral triangle formed by respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. In other words, such alignment of each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> with respect to the associated one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> results in spatially aligning each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> with a respective reference position that is substantially at an equal distance from the boundaries of the associated reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in circumferential direction. In various examples, the respective (conceptual) radial line segment that bisects the respective one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> lies on a respective (conceptual) bisecting plane, which is substantially perpendicular to the reference plane defined by the respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, which meets the center point of the reflector assembly <NUM> and which bisects the respective reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated therewith. Consequently, each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be symmetric with respect to the respective (conceptual) bisecting plane (and with respect to the respective (conceptual) bisecting radial line segment).

In this regard, the spatial alignment between one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the respective (conceptual) line segment bisecting the associated reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> therewith implies that a projection of the position of the respective receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> along a line that is perpendicular to the reference plane defined by respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> coincides with the respective (conceptual) line segment that bisects the associated one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Along similar lines, the spatial alignment between the transmitter <NUM> and the center point of the reflector assembly <NUM> implies that a projection of the position of the transmitter <NUM> along a line that is perpendicular to said reference plane coincides with the center point of reflector assembly <NUM>.

The transmitter <NUM> may be disposed in the cover portion <NUM> such that a respective portion of the TX beam transmitted therefrom meets respective sub-areas on surfaces of each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. In other words, the TX beam may be transmitted from the transmitter <NUM> such that its 'footprint' on the reflector assembly <NUM> overlaps the apex at the center point of the reflector assembly <NUM>. Consequently, a first portion of the divergent TX beam transmitted from the transmitter <NUM> meets a first sub-area on the surface of the reflector portion <NUM>-<NUM>, a second portion of the TX beam meets a second sub-area on the surface of the reflector portion <NUM>-<NUM>, and a third portion of the TX beam meets a third sub-area on the surface of the reflector portion <NUM>-<NUM>.

According to an example, the TX beam transmitted from the transmitter <NUM> may have its center axis directed at a predefined TX target position within the reflector assembly <NUM>. As an example in this regard, the TX target position may coincide with the center point of the reflector assembly <NUM> (e.g. the apex therein), whereas in another example the TX target position may be another position of the reflector assembly <NUM> in proximity of the center point of the reflector assembly <NUM>. As an example in this regard, the hatched circular area in the schematic illustration of <FIG> depicts the 'footprint' of the TX beam on the reflector assembly <NUM>, also showing the respective (first, second and third) sub-areas on the surfaces of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> met by the TX beam transmitted from the transmitter <NUM>. Hence, with the center axis of the TX beam directed at the TX target position located at or close to the apex at the center of the reflector assembly <NUM>, the ridges formed at the respective boundaries between the adjacent reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> serve to split the TX beam into the first, second and third portions of substantially equal size for reflection from the reflector assembly <NUM>, respectively, to the reflector portions <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>.

It is worth noting that the schematic illustration of <FIG> serves as a conceptual example regarding the (first, second and third) sub-areas of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> met by the TX beam transmitted from the transmitter <NUM> with respect to the apex provided at the center of the reflector assembly <NUM>. In various implementations of the wind measurement apparatus <NUM> the (first, second and third) sub-areas of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> met by the TX beam may have a size that is different (e.g. larger) in comparison to that shown in the illustration of <FIG>, depending e.g. on the distance between the cover portion <NUM> and the base portion <NUM>, on characteristics of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, on respective characteristics of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, on the distances between the transmitter <NUM> and each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and/or on the TX target position applied for the TX beam transmitted from the transmitter <NUM>.

Respective orientations of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> with respect to the cover portion <NUM> depend e.g. on the TX target position applied for the TX beam, on respective RX target positions applied for the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and/or on characteristics of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Since the TX target position is at or close to the apex at the center of the reflector assembly <NUM>, the (substantially planar) front face of the transmitter <NUM> is typically substantially parallel with the reference plane defined by respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> is oriented such that its (substantially planar) front face is substantially perpendicular to a (conceptual) line connecting the center point of the front face of the respective receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and a respective RX target position located within the reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated with the respective receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, thereby steering the center axis of a RX beam of the respective receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> towards the respective RX target position. In this regard, the respective RX target positions preferably reside within the respective (first, second and third) sub-areas of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> met by the TX beam transmitted from the transmitter <NUM>. Consequently, at least in some examples the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be arranged in the cover portion <NUM> in orientations where their respective front faces are inclined with respect to the reference plane defined by respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

If considering the reflection of the TX beam transmitted from the transmitter <NUM> towards the TX target position, along the lines described in the foregoing, a first TX beam portion may meet the first sub-area on the surface of the reflector portion <NUM>-<NUM>, a second TX beam portion may meet of the second sub-area on the surface of the reflector portion <NUM>-<NUM> and a third TX beam portion may meet the third sub-area on the surface of the reflector portion <NUM>-<NUM>. Consequently, due to the respective ridges formed at the respective boundaries between the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the apex formed at the center point of the reflector assembly <NUM>, the first TX beam portion may be reflected from the reflector portion <NUM>-<NUM> towards the receiver <NUM>-<NUM>, the second TX beam portion may be reflected from the reflector portion <NUM>-<NUM> towards the receiver <NUM>-<NUM>, and the third TX beam portion may be reflected from the reflector portion <NUM>-<NUM> towards the receiver <NUM>-<NUM>, each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> thereby receiving via the reflector assembly <NUM> a respective partial reflection of the TX beam transmitted from the transmitter <NUM>. Hence, the ridges at the respective boundaries between the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the apex formed at the center point of the reflector assembly <NUM> serve to split the TX beam into three TX beam portions of substantially equal size, thereby also splitting the signal power conveyed in the TX beam originating from the transmitter <NUM> into three substantially equal portions and transferring each third of the signal power towards the respective one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

Still referring to the first example, if considering reflection of the first TX beam portion from the reflector portion <NUM>-<NUM> towards the receiver <NUM>-<NUM>, the concave shape of the reflector portion <NUM>-<NUM> facilitates converging reflection of the first TX beam portion towards the receiver <NUM>-<NUM> from a relatively large sub-area of the reflector portion <NUM>-<NUM> (in comparison to a reflector having a substantially planar surface), whereas similar considerations apply to reflection of the second TX beam portion from the reflector portion <NUM>-<NUM> towards the receiver <NUM>-<NUM> and to reflection of the third TX beam portion from the reflector portion <NUM>-<NUM> towards the receiver <NUM>-<NUM>, mutatis mutandis. Therefore, the concave shape of the reflector portions <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> may further allow for some freedom in orientation of the transmitter <NUM> with respect to the reference plane and/or exact location of the TX target position in relation to the apex at the center point of the reflector assembly <NUM> while still ensuring reception of the measurement signal conveyed in the respective one of the first, second and third TX beam portions at a sufficient signal power at the respective one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to enable uncompromised measurement performance.

As described in the foregoing, each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be provided as a respective concave reflector, where each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may have, for example, a substantially ellipsoidal shape. In this regard, the respective surface of each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may have a substantially ellipsoidal curvature that is defined by a portion of an underlying ellipsoid, and hence the surfaces of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may have a shape of a predefined ellipsoidal cap of the underlying ellipsoid or a part thereof. In the present disclosure, in the interest of clarity and brevity of description, such shape of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be also referred to as an ellipsoidal shape, even though only a portion of the underlying ellipsoid is meant. While the present disclosure frequently applies a substantially ellipsoidal reflector shape as an example of the concave reflector surface, the substantially ellipsoidal shape serves as a non-limiting example and in other examples a different concave reflector shape may be applied instead, such as a substantially spherical shape defined via a portion of a sphere or a substantially paraboloidal concave shape defined via a portion of a paraboloid. Further exemplifying characteristics of the concave shape of any of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and its position with respect to associated one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are described in the following with references to the reflector portion <NUM>-<NUM> and its position with respect to the position of the receiver <NUM>-<NUM>. Similar considerations are valid also for the concave shape of the reflector surface of reflector portion <NUM>-<NUM> and its position with respect to the position of the receiver <NUM>-<NUM> as well as for the concave shape of the reflector surface of reflector portion <NUM>-<NUM> and its position with respect to the position of the receiver <NUM>-<NUM>, mutatis mutandis.

In an example, the dependency between the concave shape and position of the reflector surface of the reflector portion <NUM>-<NUM> and the respective positions of the transmitter <NUM> and the receiver <NUM>-<NUM> may be defined as follows: the center points of the respective front faces of the transmitter <NUM> and the receiver <NUM>-<NUM> may be positioned at respective locations that are at a substantially equal distance from a reference axis that is normal to the reference plane defined by respective locations of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and that intersects and bisects a (conceptual) reference line segment connecting the center points of the respective front faces of the transmitter <NUM> and the receiver <NUM>-<NUM>, whereas the reference axis meets the reflector surface at a normal angle (i.e. the reference axis is perpendicular to a tangent plane of the reflector surface at the point where the reference axis intersects the reflector surface). In the present disclosure, the point of the reflector surface at which the reference axis meets the reflector surface is also referred to as a zero-gradient point. In a variation of such a reflector surface design, the reference axis may intersect the (conceptual) reference line segment in a position that is offset from its midpoint that is at substantially the same distance from respective positions of the transmitter <NUM> and the receiver <NUM>-<NUM>.

According to an example, the reflector surface may be symmetrical with respect to a plane defined by the above-described reference axis and the (conceptual) reference line segment. In this regard, the said plane may coincide with or define the respective (conceptual) bisecting plane described in the foregoing, thereby resulting in the reflector surface that is symmetrical with respect to the respective (conceptual) bisecting plane that bisects the reflector portion <NUM>-<NUM> and, consequently, symmetrical with respect to the respective (conceptual) radial line segment that bisects the reflector portion <NUM>-<NUM>.

According to an example, the reflector surface may be defined as a concave cap of the underlying concave surface, separated from the underlying concave surface by a surface normal of its center axis. As non-limiting examples in this regard, the underlying concave surface may comprise a surface that is symmetrical with respect to its center axis, whereas the above-described reference axis may coincide with the center axis of the underlying concave surface. Examples of such symmetrical surfaces include an ellipsoid, a spheroid, or a paraboloid, whereas the transmitter <NUM> and the receiver <NUM>-<NUM> are preferably positioned within the underlying concave surface.

Such shape and positioning of the reflector surface with respect to the respective locations of the transmitter and the receiver <NUM>-<NUM> (and/or such positioning of the transmitter <NUM> and the receiver <NUM>-<NUM> with respect to the shape and position of the reflector surface) provides a consistent path between the transmitter <NUM> and the receiver <NUM>-<NUM> via reflection from the reflector portion <NUM>-<NUM> substantially regardless of the distance between the above-described reference plane and the zero-gradient point of the reflector surface. In measurement conditions where the general direction of the airflow through the measurement volume is substantially parallel to the reference plane (as in case of the wind measurement apparatus <NUM>), the consistent path substantially guarantees that, regardless of the speed and direction of the airflow and regardless of the shape of the reflector surface around the zero-gradient point, a measurement signal originating from the transmitter <NUM> that meets the zero-gradient point is received at the receiver <NUM>. Moreover, due to the concave shape of the reflector portion also the measurement signals originating from the transmitter <NUM> and that meet a sub-area of the reflector surface around the zero-gradient point (e.g. the first sub-area described in the foregoing) are likewise received at the receiver <NUM>, where the size of the sub-area is dependent on the curvature of the reflector surface.

The spatial relationship between the respective positions of the transmitter <NUM> and the receiver <NUM>-<NUM> and the shape of the concave reflector surface of the reflector portion <NUM>-<NUM> described above generalizes into defining the concave reflector surface of a given one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to follow the shape of a portion of an underlying concave surface such that a respective refence axis meets the reflector surface at a normal angle, where the respective reference axis is substantially perpendicular to the reference plane defined by the respective locations of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and it intersects (e.g. bisects) the (conceptual) reference line segment connecting the transmitter <NUM> to the receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> that is associated with the given one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> at a position that is substantially at an equal distance from respective positions of the transmitter <NUM> and said receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Herein, the reflector surface may be defined as a concave cap of the underlying concave surface, where the concave cap is separated from the underlying concave surface by a surface normal of its center axis. As an example in this regard, the underlying concave surface defining the shape of a given one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may comprise a surface that is symmetrical with respect to its center axis, such as an ellipsoid, a spheroid, or a paraboloid, whereas the transmitter <NUM> and the receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated with the respective one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are preferably positioned within the underlying concave surface.

The portion of the underlying concave surface that defines the shape of the respective reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be chosen in consideration of characteristics and direction of the TX beam transmitted from the transmitter <NUM>, e.g. in consideration of the extent of divergence of the TX beam and further in consideration of the TX target position applied for the TX beam and the respective RX target position applied for the respective RX beams of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. In this regard, the reflector surfaces may be made sufficiently large to ensure receiving the TX beam substantially in its entirety at the chosen distance between the cover portion <NUM> and the base portion <NUM>, possibly further accounting for any spatial shifting of the TX beam that may occur due to wind at wind speeds of interest.

In an example where the reflector surface has a substantially ellipsoidal shape, the reflector portion <NUM>-<NUM> may be defined as a portion of a (conceptual) underlying ellipsoid having its first principal axis connecting the center points of the respective front faces of the transmitter <NUM> and the receiver <NUM>-<NUM> and having its center point at a position that is substantially at an equal distance from the center points of the respective front faces of the transmitter <NUM> and the receiver <NUM>-<NUM>. Consequently, the zero-gradient point may comprise an endpoint of a second principal axis of the underlying ellipsoid whereas a plane defined by the first principal axis and a third principal axis of the underlying ellipsoid coincides with the reference plane defined by (the center points of the respective front faces of) the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and a plane define by the first principal axis and the second principal axis define the respective (conceptual) bisecting plane for the reflector portion <NUM>-<NUM> to be spatially aligned with the receiver <NUM>-<NUM>.

Considering the relationship between the shape of the ellipsoidal surface of the reflector portion <NUM>-<NUM> and the respective positions of the transmitter <NUM> and the receiver <NUM>-<NUM> in view of the ellipsoid illustrated in <FIG>, the center points of the respective front faces of the transmitter <NUM> and the receiver <NUM>-<NUM> may be positioned on the principal axis b at a distance D from the center point of the underlying ellipsoid (shown as a dot where the principal axes a, b and c meet) at opposite sides of the center point, whereas the zero-gradient point may be one of the endpoints of the principal axis c, the plane defined by the principal axes a and b may be the one that coincides with the reference plane, and the plane defined by the principal axes b and c may be the one that defines the respective (conceptual) bisecting plane. In a variation of this example, the center points of the respective front faces of the transmitter <NUM> and the receiver <NUM>-<NUM> may be offset by a predefined distance from the plane defined by the principal axes a and b (i.e. along the principal axis c). In both these examples the portion of the underlying ellipsoid that defines the shape of ellipsoidal surface of the reflector portion <NUM>-<NUM> may be chosen in consideration of respective characteristics and direction of the TX beam of the transmitter <NUM> and/or the RX beam of the receiver <NUM>-<NUM>. Similar considerations apply to defining respective ellipsoidal concave surfaces for the reflector portions <NUM>-<NUM> and <NUM>-<NUM> as well, mutatis mutandis.

It should be noted that the relationship between the substantially ellipsoidal shape of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the respective positions of the associated receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in relation to the position of the transmitter <NUM> described above is a non-limiting one and in other examples the spatial relationship between the respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in relation to the position of the transmitter <NUM> and the shape and position of the ellipsoidal reflector surface may be defined in a different manner while still providing advantageous reflection characteristics described in the present disclosure.

The examples above (implicitly) define the structure of the trilaterally symmetrical wind measurement arrangement and hence the structure of the wind measurement apparatus <NUM> in this regard via first defining the respective positions of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> on the base-portion-facing side of the cover portion <NUM> and applying the respective positions chosen for the transmitter <NUM> and for the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to define the concave shapes of the reflector surfaces of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and their positions with respect to the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in accordance with the relationship described above, thereby also (at least indirectly) defining the distance between the cover portion <NUM> and the base portion <NUM>. According to another example, the design procedure of the of the trilaterally symmetrical wind measurement arrangement and, consequently, the structure of the wind measurement apparatus <NUM>, may involve first defining the concave shapes of the reflector surfaces of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and subsequently defining the respective positions of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> with respect to their associated reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in accordance with the relationship described above, thereby also (at least indirectly) defining the distance between the cover portion <NUM> and the base portion <NUM>. The design of the wind measurement arrangement in terms of respective positions of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the respective positions and shapes of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated therewith may be carried out e.g. by an experimental procedure via usage of suitable simulation tool(s) in order to find the respective positions of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, their orientation with respect the reflector assembly <NUM> and the shapes for the concave reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> that provide a desired performance in consideration of any design constraints e.g. in terms of size of the wind measurement apparatus <NUM>.

<FIG> illustrates a block diagram of some (logical) elements of the wind measurement apparatus <NUM> according to the first example. In this regard, <FIG> illustrates the transmitter <NUM>, the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and a control portion <NUM>. The control portion <NUM> may control at least some aspects of operation of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, e.g. transmission of the measurement signal from the transmitter <NUM> in form of the TX beams and capturing of reflected measurement signals based on reflections of the (first, second and third) TX beam portions received at the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Moreover, the control portion <NUM> may derive one or more wind characteristics based on respective propagation delays of the measurement signal from the transmitter <NUM> to the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, e.g. based on time delays between transmission of the measurement signal from the transmitter <NUM> and its reception at the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, thereby providing a time-of-flight based wind measurement. The control portion <NUM> may receive control input (CTRL) via a user interface or from another apparatus and the control portion <NUM> may output at least part of the derived wind characteristics via the user interface or to another apparatus.

As described in the foregoing, the measurement signals conveyed in the TX beam may comprise ultrasonic signals that may be characteristic to the applied transmitter <NUM> or that may be supplied for transmission in the TX beam by the transmitter <NUM>. In the former scenario, the control portion <NUM> may operate the transmitter <NUM> to transmit the measurement signal according to a predefined schedule, whereas in the latter scenario, the control portion <NUM> may provide the transmitter <NUM> with the respective measurement signal for transmission therefrom according to the predefined schedule. In this regard, the measurement signals conveyed in the TX beam may convey a certain waveform, e.g. a pulse or a sequence of pulses, at ultrasonic frequencies and, consequently, the propagation time of the measurement signal from the transmitter <NUM> to one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be conveniently determined at the control portion <NUM> via matching the respective pair of the certain waveform in the measurement signal transmitted from one of the transmitter <NUM> and its 'copy' in the measurement signal captured at the respective one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Such an approach for measurement of wind characteristics such as wind speed and/or wind direction in general is known in the art and hence further details in this regard are not provided in the present disclosure.

The trilaterally symmetric wind measurement arrangement of the wind measurement apparatus <NUM> according to the first example enables substantially simultaneous measurement on three measurement paths via usage of the single transmitter <NUM> and the three receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. This aspect is schematically illustrated via <FIG> that shows measurements paths P<NUM>, P<NUM>, P<NUM> from the transmitter <NUM> to each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, where Pm denotes a transmission path from the transmitter <NUM> to the receiver <NUM>-m via the associated reflector portion <NUM>-m (i.e. one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>).

Along the lines described above, the aspect of the reflector assembly <NUM> serving to split the measurement signal transmitted from the transmitter <NUM> for reception by each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> enables simultaneous measurement from three measurement paths via usage of only single transmitter, thereby enabling accurate, reliable and robust arrangement for wind measurement via usage of a relatively small number of components and, consequently, providing a cost-effective approach for wind measurement. Moreover, the concave shape (e.g. substantially ellipsoidal shape) of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> enables a relatively short measurement distance (i.e. the distance between the cover portion <NUM> and the base portion <NUM>), thereby allowing for relatively small size of the wind measurement apparatus <NUM>, which is advantageous in a majority of usage scenarios.

Another advantage of the trilaterally symmetrical wind measurement arrangement applied in the wind measurement apparatus <NUM> according to the first example is simultaneous focusing and amplification of the measurement signal conveyed in the TX beam and automatic directional correction, which both are consequences of the concave shape of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>:.

<FIG> schematically illustrate some components of a wind measurement apparatus <NUM> according to a second example. As in the first example described in the foregoing, also in the second example the wind measurement apparatus <NUM> comprises the cover portion <NUM> and the base portion <NUM> arranged at a distance from each other to form a gap that allows for an airflow between the cover portion <NUM> and the base portion <NUM>. The wind measurement apparatus <NUM> according to the second example is similar to the first example in operational characteristics and structure, apart from the different number of receivers and the different number of reflector portions: in the second example the base-portion-facing side (e.g. on the cover-portion-facing surface) of the cover portion <NUM> is provided with an arrangement of the single transmitter <NUM> and four receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>, whereas the reflector assembly <NUM> on the cover-portion-facing side (e.g. the cover-portion-facing surface) of the base portion <NUM> includes four substantially identical concave reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> and it exhibits rotational symmetry of order four, thereby constituting a quadrilaterally symmetrical wind measurement arrangement.

<FIG> schematically illustrates the base-portion-facing side of the cover portion <NUM> according to the second example, showing the transmitter <NUM> together with the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> that are arranged at respective positions that correspond to respective vertices of a (conceptual) square arranged on the cover-portion-facing side of the cover portion <NUM>, thereby constituting a quadrilaterally symmetrical arrangement of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> on the base-portion-facing side of the cover portion <NUM>. The transmitter <NUM> may be arranged in a position that is at a substantially equal distance from each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. As an example in this regard, the transmitter <NUM> may be disposed on an axis that meets the reference plane defined by the respective positions of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in a normal angle substantially at the center point of the (conceptual) square formed by the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, e.g. substantially on the reference plane or (slightly) offset from the reference plane, either towards the base portion <NUM> or further away from the base portion <NUM>.

As another way of specifying the arrangement of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> on the base-portion-facing side of the cover portion <NUM>, the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be disposed at respective positions that are evenly spread (i.e. evenly spaced) on a (conceptual) circle on the base-portion-facing side of the cover portion <NUM>, whereas the axis on which the transmitter <NUM> is disposed may be a normal of the reference plane that meets the reference plane substantially at the center point of the (conceptual) circle.

As described in the foregoing, in the second example the reflector assembly <NUM> includes a quadrilaterally symmetrical arrangement of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, where each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may comprise a respective concave surface for reflecting measurement signals transmitted from the transmitter <NUM> for reception by the receiver <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated therewith. As in the case of the first example, also in the second example a respective boundary between each pair of two adjacent reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> forms a respective ridge due to the concave shapes of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, whereas the ridges meet at a center point of the reflector assembly <NUM> and from an apex.

As in case of the first example, also in the second example each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be spatially aligned with a respective (conceptual) radial line segment that extends from the center point of the reflector assembly <NUM> towards the perimeter of the reflector assembly <NUM> and that bisects the reflector portion <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> associated with the respective one of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. In other words, each of the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be spatially aligned with respect to a respective (conceptual) bisecting plane that is substantially perpendicular to the reference plane, that meets the center point of the reflector assembly <NUM> and that bisects the associated one of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

Still referring to the second example, the transmitter <NUM> may be arranged to transmit the TX beam such that its center axis is directed at the TX target position located at or in proximity of the apex in the reflector portion <NUM>, which results in respective portions of the TX beam meeting respective sub-areas in each of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>. Consequently, the arrangement of ridges and the apex on the surface of the reflector assembly <NUM> results in splitting the TX beam into first, second, third and fourth TX beam portions for reflection, respectively, from the respective reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> towards the associated receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

Aspects that relate to other characteristics of structure and operation of the wind measurement apparatus <NUM> according to the second example, e.g. ones related to general structure of the reflector assembly <NUM> and the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> therein, to the concave shape (e.g. the substantially ellipsoidal shape) of the reflector portions <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in dependence of the respective positions of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (or vice versa), to respective orientations of the transmitter <NUM> and the receivers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> with respect to the cover portion <NUM> as well as to general operation of the wind measurement apparatus <NUM> under control of the control portion <NUM> may be provided in a manner described in the foregoing in context of the first example, mutatis mutandis.

The quadrilaterally symmetric wind measurement arrangement of the wind measurement apparatus <NUM> according to the second example enables substantially simultaneous measurement on four measurement paths of substantially equal length. Hence, an advantage of the wind measurement apparatus <NUM> according to the second example over the wind measurement apparatus <NUM> according to the first example is further improved accuracy and reliability of the wind measurement due to increased number of measurement paths, while on the other hand introduction of the fourth receiver increases the number of components required for the wind measurement apparatus <NUM> and hence results in a slightly more complex design.

The first example that relies on the trilaterally symmetrical wind measurement arrangement and the second example that relies on the quadrilaterally symmetrical wind measurement arrangement readily generalize into a wind measurement apparatus <NUM> according a third example that applies a symmetrical wind measurement arrangement of order N (i.e. a N-laterally rotationally symmetrical wind measurement arrangement), where the order N is larger than or equal to three. Hence, the third example implicitly encompasses the first and second example. The wind measurement apparatus <NUM> according to the third example has the advantageous characteristics described in the foregoing for the trilaterally symmetrical wind measurement arrangement according to the first example while providing further improvement in terms of accuracy and reliability of the wind measurement with increasing value of N. Such a measurement arrangement includes an arrangement of the single receiver and N receivers together with the reflector assembly <NUM> that is divided into N substantially identical reflector portions. In this regard, the N receivers may be jointly referred to via a refence number <NUM>, any of the N receivers may be referred to via a reference number <NUM>-n, while any of the N reflector portions may be referred to via a reference number <NUM>-n. The arrangement of the N receivers <NUM> arranged in the cover portion <NUM> with respect to the N reflector portions <NUM>-n of the reflector assembly <NUM> provided in the base portion <NUM> (or vice versa) may be characterized e.g. in the following manner:.

As described in the foregoing in context of the first and second examples, also in the third example the alignment of the receivers <NUM>-n with respect to the respective (conceptual) bisecting line segments may be also defined via alignment with respect to respective (conceptual) bisecting planes, i.e. each of the receivers <NUM>-n may be spatially aligned with respect to a respective (conceptual) bisecting plane that is substantially perpendicular to the reference plane, that meets the center point of the reflector assembly <NUM> and that bisects the associated one of the reflector portions <NUM>-n.

Still referring to the third example, the transmitter <NUM> may be arranged to transmit the TX beam such that its center axis is directed at the TX target position located at or in proximity of the apex in the reflector portion <NUM>, which results in respective portions of the TX beam meeting respective sub-areas in each of the reflector portions <NUM>-n. Consequently, the arrangement of ridges and the apex on the surface of the reflector assembly <NUM> results in splitting the TX beam into N TX beam portions for reflection from the respective reflector portions <NUM>-n towards the associated receivers <NUM>-n.

Aspects that relate to other characteristics of structure and operation of the wind measurement apparatus <NUM> according to the third example, e.g. ones related to general structure of the reflector assembly <NUM> and the reflector portions <NUM>-n therein, to the concave shape (e.g. the substantially ellipsoidal shape) of the reflector portions <NUM>-n in dependence of the respective positions of the transmitter <NUM> and the receivers <NUM>-n (or vice versa), to respective orientations of the transmitter <NUM> and the receivers <NUM>-n with respect to the cover portion <NUM> as well as to general operation of the wind measurement apparatus <NUM> under control of the control portion <NUM> may be provided in a manner described in the foregoing in context of the first and/or second examples, mutatis mutandis.

In general, increasing N, i.e. increasing the number of the receivers <NUM>-n and the number of reflector portions <NUM>-n in the reflector assembly <NUM>, basically results in further improvements in accuracy and reliability of the wind measurement via increasing the number of measurement paths, while on the other hand it results in increasing the number of components required for the wind measurement apparatus <NUM> and in more complex design. Consequently, the most expedient number of the receivers <NUM>-n and the reflector portions <NUM>-n to be applied in the wind measurement arrangement of the wind measurement apparatus <NUM> may depend on the intended usage of the wind measurement apparatus <NUM> and/or on requirements and/or constraints set for the accuracy and reliability of the wind measurement, for the size of the wind measurement apparatus <NUM>, for the manufacturing cost of the wind measurement apparatus <NUM>, etc..

The examples described in the foregoing generally refer to substantially simultaneous measurement carried out on multiple measurement paths, which enables accurate and reliable wind measurements. In the course of operation of the wind measurement apparatus <NUM>, the control portion <NUM> may operate the transmitter <NUM> to periodically transmit the measurement signal in the TX beam. In this regard, the transmission of the measurement signals from the transmitter <NUM> may be carried out according to a predefined schedule, typically at predefined time intervals, where the time delay between two successive transmissions of the measurement signal from the transmitter <NUM> may be referred to as a measurement interval. In this regard, the shorter measurement interval may result in improved measurement performance in terms of the ability to track any changes in wind characteristics without undue delay while it may result in increasing the computation required in operation of control portion <NUM> to derive the one or more wind characteristics.

The examples described in the foregoing refer to the arrangement of the receivers <NUM>-n and the associated reflector portions <NUM>-n of the reflector assembly <NUM> such that each of the receivers <NUM>-n is spatially aligned with the respective (conceptual) bisecting plane (or the respective (conceptual) bisecting line segment), which may also serve as a symmetry plane for the respective reflector portion <NUM>-n. In other examples, the plane that defines the alignment between the receiver <NUM>-n and the associated reflector portion <NUM>-n may not be the one that bisects (i.e. divides into two parts of substantially equal size) but a (conceptual) dividing plane that is substantially perpendicular to the reference plane defined by the respective positions of the receivers <NUM>, that meets the center point of the reflector assembly <NUM> and that divides the respective reflector portion <NUM>-n into two parts of substantially unequal size. In this regard, each of the reflector portions <NUM>-n may be symmetric with respect to the respective (conceptual) dividing plane.

The examples described in the foregoing refer to the reflector assembly <NUM> being divided into N concave reflector portions <NUM>-n that are substantially identical to each other. According to another example, the reflector portions <NUM>-n may not be substantially identical to each other. As an example in this regard, the reflector portion may include a first reflector portion <NUM>-n1 and a second reflector portion <NUM>-n2 that have respective concave shapes different from each other, e.g. such that in the first reflector portion <NUM>-n1 the zero-gradient point is closer to the center point of the reflector assembly <NUM> than that of the second reflector portion <NUM>-n1 and/or such that one or more sub-areas of the first reflector portion <NUM>-n1 have a curvature different from spatially corresponding sub-areas of the second reflector portion <NUM>-n2.

The examples described in the foregoing (at least implicitly) assume symmetrical shape of the reflector portions <NUM>-n such that they are symmetrical with respective to the respective (conceptual) bisecting line segment or with respect to the respective (conceptual) bisecting or dividing plane applied as the reference point for spatial alignment between the receivers <NUM>-n and the respective associated reflector portions <NUM>-n. According to another example, at least some of the reflector portions <NUM>-n may exhibit symmetry with respect to a plane that is offset from the respective (conceptual) bisecting line segment or with respect to the respective (conceptual) bisecting or dividing plane applied as the reference point for spatial alignment between the receivers <NUM>-n and the respective associated reflector portions <NUM>-n, whereas in a further example at least some of the reflector portions <NUM>-n may not exhibit symmetry with respect to any (conceptual) bisecting or dividing plane of the kind described in the foregoing.

The examples described in the foregoing refer to concave shape of the reflector portions <NUM>-n of the reflector assembly <NUM>. In this regard, the concave shape of the reflector portion <NUM>-n implies concave shape at least in those areas of the respective reflector surfaces of the reflector portions <NUM>-n that are intended for reception and reflection of the respective TX beam portions of the TX beam originating from the transmitter <NUM>. According to an example, the reflector portions <NUM>-n in their entirety may exhibit the concave shape of the kind described in the foregoing, whereas in other examples the reflector portions <NUM>-n outside the areas intended for reception and reflection of the respective TX beam portions may exhibit concave curvature different from the kind described in the foregoing and/or they may exhibit non-concave shape. As an example of the latter, the areas of the reflector portions <NUM>-n outside the ones intended for reception and reflection of the respective TX beam portions may involve a substantially planar shape. Regardless of the curvature of the reflector portions <NUM>-n outside the areas intended for reception and reflection of the respective TX beam portions, the overall shape of the reflector portions <NUM>-n may serve as a monotonically descending 'slope' from the center of the reflector assembly <NUM> towards the perimeter of the reflector assembly <NUM> (when the wind measurement apparatus <NUM> is in its upright position with the reflector assembly <NUM> facing upwards), thereby avoiding water building up on those areas of the reflector portions <NUM>-n intended for reception and reflection of the respective TX beam portions. Further in this regard, the perimeter of the reflector assembly <NUM> may be open or it may be provided with one or more openings that allow for any water falling on the reflector portions <NUM>-n flowing away from the reflector assembly <NUM>.

<FIG> illustrates a block diagram of some components of an apparatus <NUM> that may be employed to implement operations described in the foregoing with references to the control portion <NUM>. The apparatus <NUM> comprises a processor <NUM> and a memory <NUM>. The memory <NUM> may store data and computer program code <NUM>. The apparatus <NUM> may further comprise communication means <NUM> for wired or wireless communication with other apparatuses and/or user I/O (input/output) components <NUM> that may be arranged, together with the processor <NUM> and a portion of the computer program code <NUM>, to provide the user interface for receiving input from a user and/or providing output to the user. In particular, the user I/O components may include user input means, such as one or more keys or buttons, a keyboard, a touchscreen or a touchpad, etc. The user I/O components may include output means, such as a display or a touchscreen.

The components of the apparatus <NUM> are communicatively coupled to each other via a bus <NUM> that enables transfer of data and control information between the components.

The memory <NUM> and a portion of the computer program code <NUM> stored therein may be further arranged, with the processor <NUM>, to cause the apparatus <NUM> to perform at least some aspects of operation of the control portion <NUM> described in the foregoing. Although the processor <NUM> is depicted as a respective single component, it may be implemented as respective one or more separate processing components. Similarly, although the memory <NUM> is depicted as a respective single component, it may be implemented as respective one or more separate components, some or all of which may be integrated/removable and/or may provide permanent / semi-permanent/ dynamic/cached storage.

The computer program code <NUM> may comprise computer-executable instructions that implement at least some aspects of operation of the control portion <NUM> described in the foregoing when loaded into the processor <NUM>. As an example, the computer program code <NUM> may include a computer program consisting of one or more sequences of one or more instructions. The processor <NUM> is able to load and execute the computer program by reading the one or more sequences of one or more instructions included therein from the memory <NUM>. The one or more sequences of one or more instructions may be configured to, when executed by the processor <NUM>, cause the apparatus <NUM> to perform at least some aspects of operation of the control portion <NUM> described in the foregoing. Hence, the apparatus <NUM> may comprise at least one processor <NUM> and at least one memory <NUM> including the computer program code <NUM> for one or more programs, the at least one memory <NUM> and the computer program code <NUM> configured to, with the at least one processor <NUM>, cause the apparatus <NUM> to perform at least some aspects of operation of the control portion <NUM> described in the foregoing.

The computer program code <NUM> may be provided e.g. a computer program product comprising at least one computer-readable non-transitory medium having the computer program code <NUM> stored thereon, which computer program code <NUM>, when executed by the processor <NUM> causes the apparatus <NUM> to perform at least some aspects of operation of the control portion <NUM> described in the foregoing. The computer-readable non-transitory medium may comprise a memory device or a record medium that tangibly embodies the computer program. As another example, the computer program may be provided as a signal configured to reliably transfer the computer program.

Claim 1:
A wind measurement apparatus (<NUM>) comprising:
a cover portion (<NUM>) and a base portion (<NUM>) arranged at a distance from each other to allow for an airflow therebetween;
an arrangement of N receivers (<NUM>) disposed on a base-portion-facing side of the cover portion (<NUM>) in respective positions that serve as respective vertices of a convex regular polygon of order N, where N is at least three; and
a transmitter (<NUM>) disposed on the base-portion facing side of the cover portion (<NUM>) in a position that is at a substantially equal distance from each of the N receivers (<NUM>);
characterized in that the apparatus (<NUM>) comprises a reflector assembly (<NUM>) arranged on a cover-portion-facing side of the base portion (<NUM>), wherein the reflector assembly (<NUM>) is divided into N concave reflector portions (<NUM>-n),
wherein each receiver (<NUM>-n) is associated with one of the reflector portions (<NUM>-n) and wherein the reflector assembly (<NUM>) and the base portion (<NUM>) are disposed with respect to each other such that the transmitter (<NUM>) is spatially aligned with a center point of the reflector assembly (<NUM>) and that each receiver (<NUM>-n) is spatially aligned with the associated reflector portion (<NUM>-n),
wherein the transmitter (<NUM>) is arranged to transmit a measurement signal in a transmitter beam, TX beam, towards the reflector assembly (<NUM>) such that the TX beam meets each of the reflector portions (<NUM>-n),
wherein each of the receivers (<NUM>-n) is arranged to receive, via the associated reflector portion (<NUM>-n), a reflection of a TX beam portion that meets the respective reflector portion (<NUM>-n), and
wherein said measurement signal comprises an ultrasonic measurement signal and wherein the apparatus (<NUM>) further comprises a control portion (<NUM>) arranged to:
operate the transmitter (<NUM>) to transmit the measurement signal in the TX beam and operate each of the N receivers (<NUM>) to capture the respective reflected measurement signal received in the reflections of the respective TX beam portions, and
derive one or more wind characteristic based on respective propagation delays of the respective reflected measurement signals captured at the N receivers (<NUM>).