Patent Description:
Conventionally, as apparatuses which acquire wave information as information related to a wave, wave observation radars (radar apparatus) as disclosed in Patent Document <NUM> are known. In such a radar apparatus, with reference to <FIG> of Patent Document <NUM>, echo signals acquired from echoes from a given range on the sea are two-dimensionally fast Fourier transformed (FFT), and with reference to <FIG> of Patent Document <NUM>, a two-dimensional Fourier transformed signal Sf is derived. Then, the radar apparatus calculates wave information (a wave direction, a wavelength, etc.) based on the two-dimensional Fourier transformed signal Sf.

[Patent Document <NUM>] <CIT>
<CIT> teaches a device and method for obtaining oceanographic and meteorological data, whereas an over-the-horizon HF radar includes transmitting a plurality of signals by using two HF radar units located on different points of a seashore to a remote geographic location, generating a family of Doppler clutter. In other words, the device may detect heights and directions of ocean waves, and performs a one-dimensional FFT (1D FFT) to time domain data for a small area to calculate the radial velocity of tide in that small area. Echoes from ships (and aircrafts) are discarded. Using two radial velocities at the same point obtained by the two HF radar units, two-dimensional tidal velocities are calculated. <CIT> relates to a method of detecting a sea surface wind field through S-waveband radar, wherein 3D FFT is performed as to the entire area about the radar apparatus. Filtering steps are applied with regard to the relationship between the frequency-wave-number and the direction-wave-number, with the ultimate goal to obtain a final filtered small area that satisfies the requirements. <CIT> discloses a radar ocean wave analysis device that performs two-dimensional FFT processing, extended to the entire area around the radar apparatus except an area that does not suit to be subject of calculation. <CIT> refers two a surface tidal-current estimation device, detecting speed vectors of wave crests on the water surface, namely by dectecting the relative velocity between the tide in the area near the own ship and the tide in the area far from the own ship. From <CIT>, a radar system capable of highly accurately estimating the speed of an observation target is known, selecting one specific analysis frequency bin (for example, a frequency bin having maximum amplitude value) from among a plurality of frequency bins in the search region. <CIT> relates to an echo signal processing device and method that, for avoiding a large computational load, obtains echo images and determines a position of an analysis area which is a position of each echo image, based on a wind direction, computes the echo signal function using echo data within the analysis area included in each of the multiple echo images.

Meanwhile, when calculating the wave information as described above, the wave information may not be calculated accurately.

The present disclosure is to solve the problem, and one purpose thereof is to calculate the wave information accurately.

The above problems are solved by the subject-matter of the independent claims.

According to the present disclosure, the wave information is accurately calculated.

Hereinafter, one embodiment of a signal processor as a signal processing device according to the present disclosure and a radar apparatus provided with the signal processor is described with reference to the drawings. The present disclosure may be widely applicable to signal processing devices which acquire wave information, and radar apparatuses provided with the signal processing device.

<FIG> is a block diagram of a radar apparatus <NUM> according to one embodiment of the present disclosure. The radar apparatus <NUM> according to this embodiment may calculate wave information (specifically, a wave height, a wavelength, etc.) which is information related to a wave, based on an echo obtained by a transmission wave transmitted being reflected on the wave and coming back. Moreover, the radar apparatus <NUM> may be configured to be capable of detecting ships which exist within a detection area. The radar apparatus <NUM> of this embodiment may be provided to, for example, a ship (hereinafter, referred to as "the ship" to be distinguished from other ships), such as a fishing boat.

As illustrated in <FIG>, the radar apparatus <NUM> may include an antenna unit <NUM>, a signal processor <NUM>, and a display unit <NUM>.

The antenna unit <NUM> may include an antenna <NUM> which functions as both transmitter and receiver, a receiving part <NUM>, and an A/D converter <NUM>.

The antenna <NUM> may be a radar antenna which is capable of transmitting a pulse-shaped radio wave as a transmission wave with a strong directivity. Moreover, the antenna <NUM> may be configured to receive a reflection wave from a target object (in this embodiment, the wave or another ship). The radar apparatus <NUM> may measure a period of time after a transmission of the pulse-shaped radio wave to a reception of the reflection wave. Thus, the radar apparatus <NUM> may be capable of detecting a distance r to the target object. The antenna <NUM> may be configured to be capable of rotating <NUM>° in a horizontal plane. The antenna <NUM> may be configured to repeat the transmission and reception of the radio wave, while changing the transmitting direction of the pulse-shaped radio wave (e.g., changing an antenna angle). With the above configuration, the radar apparatus <NUM> may be capable of detecting the target object in the plane around the ship over <NUM>°.

Note that, in the following description, operation after the transmission of the pulse-shaped radio wave until a transmission of a subsequent pulse-shaped radio wave may be referred to as a "sweep. " Moreover, operation of a <NUM>° rotation of the antenna while transmitting and receiving the radio wave may be referred to as a "scan.

The receiving part <NUM> may detect and amplify the echo signal acquired from the echo received by the antenna <NUM>. The receiving part <NUM> may output the amplified echo signal to the A/D converter <NUM>. The A/D converter <NUM> may sample the echo signal of an analog format, and convert it into digital data comprised of multiple bits. This digital data may be echo data. The echo data may include data to identify an intensity of the echo signal acquired from the reflection wave received by the antenna <NUM>. The A/D converter <NUM> may output the echo data to the signal processor <NUM>.

<FIG> is a block diagram of the signal processor <NUM> illustrated in <FIG>. The signal processor <NUM> may include an other-ships detecting module <NUM> (unnecessary target object detecting module), a frequency area spectrum generating module <NUM>, an integrating module <NUM>, and a wave information calculating module <NUM>.

The signal processor <NUM> may be comprised of devices, such as a hardware processor <NUM> (e.g., a CPU, an FPGA, etc.), and a nonvolatile memory. For example, the CPU may read and execute a program from the nonvolatile memory to function the signal processor <NUM> as the other-ships detecting module <NUM>, the frequency area spectrum generating module <NUM>, the integrating module <NUM>, and the wave information calculating module <NUM>.

The other-ships detecting module <NUM> may extract echo images resulting from other ships (unnecessary target objects). For example, the other-ships detecting module <NUM> may group, among sampling points having the echo intensity greater than a given threshold, sampling points of which a mutual distance is below a given distance because they are able to be considered as echoes from the same ship. Then, the other-ships detecting module <NUM> may detect an echo image comprised of a plurality of grouped sampling points, as an echo image from the same ship.

<FIG> is a view illustrating positions etc. of analysis areas Z1-Z5 where classified-by-analysis-area echo data is extracted, the classified-by-analysis-area echo data being extracted by a classified-by-analysis-area data extracting module <NUM> provided to the frequency area spectrum generating module <NUM>. The frequency area spectrum generating module <NUM> may carry out a frequency analysis of the echoes obtained from waves included in each range of the plurality of analysis areas Z1-Z5 and generate a directional frequency spectrum (frequency area spectrum) for each of the plurality of analysis areas Z1-Z5.

Note that, in this embodiment, the analysis areas Z1-Z5 may have the same shape and size. Moreover, the analysis areas Z1-Z5 may be disposed at the same distance with respect to the ship S. Moreover, the analysis areas Z1-Z5 may be provided as areas surrounded by straight lines parallel and perpendicular to a straight line which connects the ship S and a central point of each analysis area. By setting the analysis areas Z1-Z5 as described above, the positions and shape of the analysis areas Z1-Z5 when seen from the ship may be unified. Thus, since, as coordinate axes of the analysis areas Z1-Z5, axes which are substantially parallel to directions from the ship S toward the central points of the analysis areas Z1-Z5 are set, resolutions of the echo data in the axis directions of the analysis areas may become almost the same. Therefore, more accurate wave analysis results may be obtained.

Note that, when the analysis areas are set as described above, since directions of coordinate axes of kxky spectrums (spectrums generated by a wave component extracting module <NUM> described later) differ, the kxky spectrums obtained from the analysis areas Z1-Z5 cannot be integrated simply as they are. However, by converting the kxky spectrums into ωθ coordinates described later to align the θ-axis, an echo spectrums obtained from the analysis areas Z1-Z5 (e.g., the directional frequency spectrums obtained from the analysis areas Z1-Z5) can be integrated.

The frequency area spectrum generating module <NUM> may include the classified-by-analysis-area data extracting module <NUM>, a frequency analysis module <NUM>, the wave component extracting module <NUM>, a ωθ converting module <NUM>, and a directional frequency spectrum converting module <NUM>.

The classified-by-analysis-area data extracting module <NUM> may extract the classified-by-analysis-area echo data included in the analysis areas Z1-Z5. In this embodiment, the number, the positions, and size of the analysis areas Z1-Z5 may be determined beforehand. In this embodiment, the five analysis areas Z1-Z5 may be disposed at the positions with the same distance with respect to the ship S. For example, with reference to <FIG>, the analysis area Z1 may be disposed in the bow direction of the ship S, the analysis area Z2 may be disposed in the <NUM>° direction to the right with respect to the bow direction of the ship S, the analysis area Z3 may be disposed in the <NUM>° direction to the right with respect to the bow direction of the ship S, the analysis area Z4 may be disposed in the <NUM>° direction to the left with respect to the bow direction of the ship S, and the analysis area Z5 may be disposed in the <NUM>° direction to the left with respect to the bow direction of the ship S.

<FIG> illustrates one example in which comparatively high waves moving in the incoming direction toward the ship S or the outgoing direction from the ship S exist in the analysis areas Z2 and Z5. In <FIG>, these waves are indicated as apparent wave crest lines w. Note that, although comparatively low waves also exist in areas other than the analysis areas Z2and Z5 in <FIG>, illustration of these waves are omitted. <FIG> also illustrates one example in which other ships S1 and S2 exist in the analysis areas Z3 and Z4.

The classified-by-analysis-area data extracting module <NUM> may extract for every scan the classified-by-analysis-area echo data as the echo data included in the plurality of analysis areas Z1-Z5 included in an echo image P in a detection area Z0 obtained by one scan. Thus, the classified-by-analysis-area data extracting module <NUM> may extract the classified-by-analysis-area echo data for a plurality of scans (e.g., <NUM> scans) for each of the analysis areas Z1-Z5.

Note that the number, positions and size of the analysis areas Z1-Z5 illustrated in <FIG> may be merely examples, and the number, positions, and size of the analysis areas are not limited to the number, positions, and size illustrated in <FIG>, and may be other numbers, positions, and sizes.

The frequency analysis module <NUM> may carry out the frequency analysis of the <NUM> sheets of the classified-by-analysis-area echo data for the analysis areas Z1-Z5. For example, the frequency analysis module <NUM> may perform a three-dimensional Fast Fourier Transform (3D FFT) processing using the <NUM> sheets of classified-by-analysis-area echo data for each of the analysis areas Z1-Z5. Thus, the 3D data may be generated for every analysis area, where the units of x-axis and y-axis are rad/m, and the unit of z-axis is rad/sec. The x-axis in the 3D data may be a wave number kx in the east-west directions, the y-axis may be a wave number ky in the north-south directions, and the z-axis may be an angular frequency ω. The frequency analysis module <NUM> may generate the 3D data for each of the analysis areas Z1-Z5.

The wave component extracting module <NUM> may extract wave components resulting from the waves from the 3D data obtained by the frequency analysis module <NUM>. For example, the wave component extracting module <NUM> may extract from the 3D data, the wave components by using only information on a spectrum close to a dispersion relation of a wave expressed by the following Formulas (<NUM>) and (<NUM>). The wave component extracting module <NUM> may extract the wave components for each of the analysis areas Z1-Z5. <MAT><MAT>.

Here, ω is an angular frequency, k is a wave number, g is a gravitational acceleration, and d is a water depth. Formula (<NUM>) may be used when the water depth is deep enough, particularly when the water depth is greater than a half-wavelength, and Formula (<NUM>) may be used when Formula (<NUM>) is not used.

The ωθ converting module <NUM> may convert the spectrums of the wave components extracted by the wave component extracting module <NUM> into rectangular coordinates (ωθ coordinates) where the x-axis corresponds to a wave direction θ with respect to the ship S and the y-axis corresponds to the angular frequency ω, to generate ωθ spectrums. The ωθ converting module <NUM> may generate the ωθ spectrum for each of the analysis areas Z1-Z5.

<FIG> are views illustrating the directional frequency spectrums generated by the directional frequency spectrum converting module <NUM>. For example, <FIG> is a view illustrating the directional frequency spectrum obtained from the analysis area Z1, <FIG> is a view illustrating the directional frequency spectrum obtained from the analysis area Z2, and <FIG> is a view illustrating the directional frequency spectrum obtained from the analysis area Z5.

The directional frequency spectrum converting module <NUM> may convert the ωθ spectrums generated by the ωθ converting module <NUM> into directional frequency spectrums SZn (n= <NUM>, <NUM>,. In this embodiment, since the five analysis areas are set, N=<NUM>, and the number of directional frequency spectrums SZn generated corresponding to the analysis areas Z1-Z5 may also be five.

The directional frequency spectrums SZn are spectrums obtained by performing a coordinate conversion of the positions of the respective sampling points which constitute the ωθ spectrums generated by the ωθ converting module <NUM> at polar coordinates where the ship provided with the radar apparatus <NUM> is used as the origin, the circumferential directions correspond to the direction θ of the wave with respect to the ship S, and the radial direction corresponds to a frequency f of the wave. The directional frequency spectrums SZn may have the echo intensity (corresponding to the height of the wave) at each sampling point which constitutes each location of the polar coordinates, as information. Note that in <FIG>, the echo intensity at each sampling point is illustrated corresponding to the density of hatching comprised of dots. That is, the echo intensities at the sampling points which constitute the dense part of the dot hatching may be higher than the echo intensities at the sampling points which constitute the thin part of the dot hatching.

<FIG> is a view illustrating an integrated directional frequency spectrum Stotal generated by the integrating module <NUM>.

The integrating module <NUM> may integrate the directional frequency spectrums SZn generated by the directional frequency spectrum converting module <NUM>, and calculate the integrated directional frequency spectrum Stotal(i, j). For example, the integrating module <NUM> calculates the integrated directional frequency spectrum Stotal(i, j) by using the following Formula (<NUM>).

Here, Stotal represents the integrated directional frequency spectrum, where Stotal(i, j) is a spectral power (echo intensity) in an arbitrary direction i (<NUM>° to <NUM>° with respect to the ship) and at an arbitrary frequency j. As apparent from Formula (<NUM>), the directional frequency spectrums SZn may be integrated where their directions are unified. For example, weight coefficients βZn may be added to the spectral powers at the same frequency which are obtained from the same direction in the directional frequency spectrums SZn, and they may be then summed up to be integrated. Note that βZn may be the weight coefficients set corresponding to the analysis areas Z1-Z5, and a method of setting βZn is described below.

In this embodiment, a calculation of the integrated spectrum Stotal(i, j) may be performed as follows. For example, as for the directional frequency spectrum SZ3(i, j) obtained from the analysis area Z3 (see <FIG>) where another ship is detected, <NUM> may be used as the weight coefficient βZ3. Similarly, as for the directional frequency spectrum SZ4(i, j) obtained from the analysis area Z4 where another ship is detected, <NUM> may be used as the weight coefficient βZ4. On the other hand, the directional frequency spectrums SZn(i, j) obtained from the analysis areas Z1, Z2 and Z5 where other ships are not detected, <NUM> may be used as the weight coefficients βZn. That is, the directional frequency spectrums SZ3(i, j) and SZ4(i, j) included in the analysis areas where other ships are detected may be excluded from the candidates for the integration of the integrated directional frequency spectrum Stotal(i, j).

The wave information calculating module <NUM> may calculate the wave information, such as the wave height and the wavelength of the wave, based on the integrated directional frequency spectrum Stotal calculated by the integrating module <NUM>. For example, the wave height and the wavelength of the wave at a selected location, which is selected by a user using an external device, in the integrated directional frequency spectrum Stotal may be calculated. The wave height may be calculated based on the echo intensity at the selected location. The wavelength may be calculated based on the frequency f at the selected location. These values calculated by the wave information calculating module <NUM> may be notified to the display unit <NUM>. The display unit <NUM> may display these values.

Meanwhile, when calculating the wave information, if another ship is included in the analysis area for which the wave information is calculated, echoes related to another ship, a wake of another ship, etc. may exist in the analysis area. Thus, accurate information cannot be acquired even the wave information is calculated using the echo data in the analysis area. In this embodiment, with reference to <FIG>, the accurate wave information cannot be acquired from the analysis area Z3 where another ship S1 is included, and the analysis area Z4 where another ship S2 is included.

Regarding this, in the signal processor <NUM> of the radar apparatus <NUM> according to this embodiment, with reference to <FIG> and <FIG>, only the directional frequency spectrums SZn obtained from the analysis areas Z1, Z2 and Z5, among the plurality of analysis areas Z1-Z5 other than the analysis areas Z3 and Z4 where other ships are included, may be integrated. Thus, the wave information may be accurately calculated.

As described above, in the signal processor <NUM> of the radar apparatus <NUM> according to this embodiment, the spectral powers (echo intensities) of the directional frequency spectrums SZn generated corresponding to the analysis areas Z1-Z5 may be integrated where their directions are unified, as shown in Formula (<NUM>). Then, in the radar apparatus <NUM>, the wave information, such as the wave height and the wavelength, may be calculated based on the integrated directional frequency spectrum Stotal integrated as described above.

For example, conventionally, only one analysis area is set, and wave information is calculated based on echo data obtained from the analysis area. However, if an unnecessary target object (e.g., another ship) different from a wave exists in the analysis area, the wave information on the analysis area cannot be calculated accurately due to the target object.

Regarding to this, according to the radar apparatus <NUM>, the wave information may be calculated based on the integrated directional frequency spectrum Stotal obtained by integrating the directional frequency spectrums SZn generated for the plurality of analysis areas Z1-Z5 as described above. Thus, for example, it is possible to exclude the directional frequency spectrums SZ3 and SZ4 of the analysis areas where the unnecessary target objects are entered (in this embodiment, Z3 and Z4), from the candidates for which the integrated directional frequency spectrum Stotal is generated. Alternatively, it is possible to reduce the degree of influences by the directional frequency spectrums SZ3 and SZ4 obtained from the analysis areas Z3 and Z4 where the unnecessary target objects are entered. That is, according to the radar apparatus <NUM>, it may be possible to reduce the influences by the directional frequency spectrums SZ3 and SZ4 from the analysis areas Z3 and Z4 which are low in the reliability when calculating the wave information. Thus, it may be possible to calculate the wave information based on the directional frequency spectrums SZ1, SZ2 and SZ5 obtained from other analysis areas, i.e., the analysis areas Z1, Z2 and Z5 which are high in the reliability when calculating the wave information.

Therefore, according to the signal processor <NUM>, the wave information may be accurately calculated.

Moreover, in the signal processor <NUM>, the directional frequency spectrums SZn obtained by multiplying the plurality of directional frequency spectrums SZn by the respective weight coefficients βZn determined corresponding to the plurality of directional frequency spectrums SZn may be integrated to generate the integrated directional frequency spectrum Stotal(i, j). Thus, since it becomes possible to set the values of the weight coefficients βZn according to the reliability of the directional frequency spectrums SZn when calculating the wave information, the wave information may be calculated more accurately.

Moreover, like the signal processor <NUM>, the values of the weight coefficients βZn may be determined according to the unnecessary target objects which give adverse influences when calculating the accurate wave information to appropriately set the values of the weight coefficients βZn.

Moreover, like the signal processor <NUM>, the values of the weight coefficients βZ3 and βZ4 of the directional frequency spectrums SZ3 and SZ4 obtained from the analysis areas Z3 and Z4 where the unnecessary target objects are detected may be set to zero to significantly reduce the adverse influences which the unnecessary target objects when calculating the wave information give to the wave information.

Moreover, like the signal processor <NUM>, the values of the weight coefficients βZn of the directional frequency spectrums SZ3 and SZ4 obtained from the analysis areas Z3 and Z4 where other ships are detected is set to zero to prevent that the echoes of other ships or the echoes resulting from the wakes of other ships give influences to the wave information.

Moreover, according to the signal processor <NUM>, since the directional frequency spectrums are generated based on the wave components extracted by the wave component extracting module <NUM>, the echoes resulting from the unnecessary target objects may become difficult to be reflected in the wave information. Thus, the wave information may be calculated more accurately.

Moreover, according to the radar apparatus <NUM>, the radar apparatus provided with the signal processor <NUM> which is capable of calculating the wave information accurately may be configured.

Moreover, according to the radar apparatus <NUM>, the echoes from other ships as the unnecessary target objects may be received using the antenna <NUM> which receives the echoes from the waves, and other ships may be detected based on the echoes. That is, according to the radar apparatus <NUM>, since other ships are detectable using the antenna <NUM> provided to the radar apparatus <NUM> for calculating the wave information, it may become unnecessary to provide other special equipment in order to detect other ships. Therefore, according to the radar apparatus <NUM>, the configuration of the apparatus may be simplified.

As described above, although the embodiment of the present disclosure is described, the present disclosure is not limited to the embodiment and various changes may be possible without departing from the scope of the present disclosure.

The signal processor 10a of this modification may have a land detecting module <NUM> and a waterfall detecting module <NUM> as the unnecessary target object detecting modules, other than the components which the signal processor <NUM> of the above embodiment has.

The land detecting module <NUM> may detect land included in a detection area. For example, the land detecting module <NUM> may compare the position of the land included in a nautical chart stored in the radar apparatus <NUM> according to this modification with the position of the echo obtained by the radar apparatus <NUM> to determine whether the echo is an echo from the land.

The waterfall detecting module <NUM> may detect an area where rain or snow falls within the detection area. An echo from the rain or snow may have a more gradual inclination of the rising part and the falling part than those of ships and land. The waterfall detecting module <NUM> may determine whether the echo is an echo from the rain or snow based on such a feature of the rain or snow, i.e., based on the degree of the inclination of the rising part and the falling part described above.

The integrating module <NUM> may calculate the integrated directional frequency spectrum Stotal by using Formula (<NUM>), substantially similar to the above embodiment. Note that, unlike the above embodiment, the integrating module <NUM> may use <NUM> as the weight coefficients βZn of the spectral powers at locations included in the analysis areas where the land and the rain or snow are detected. That is, the integrating module <NUM> may also exclude the spectral powers at the locations included in the analysis areas where the land and the rain or snow are detected, from the candidates for the integration of the integrated directional frequency spectrum.

As described above, according to the signal processor 10a of the radar apparatus according to this modification, the directional frequency spectrums obtained from the analysis areas where the land or the rain or snow is detected may be also excluded from the candidates for the integration of the integrated directional frequency spectrum, as well as the directional frequency spectrums obtained from the analysis areas where other ships are detected. Thus, the wave information may be calculated more accurately, compared with the case where only the directional frequency spectrums obtained from the analysis areas where other ships are detected is excluded from the candidates for the integration of the integrated directional frequency spectrum.

The integrating module 17a may integrate the directional frequency spectrums generated by the directional frequency spectrum converting module <NUM>, similar to the above embodiment, to calculate the integrated directional frequency spectrum Stotal(i, j). However, the integrating module 17a of this modification may perform a simple summing-up of the directional frequency spectrums generated corresponding to the analysis areas, without performing the weighted addition. That is, the integrating module 17a of this modification may calculate the integrated directional frequency spectrum Stotal(i, j) by setting all the weight coefficients βZn(s) in Formula (<NUM>) to <NUM>.

As described above, according to the signal processor 10b according to this modification, even if the unnecessary target objects are included in some analysis areas among the plurality of analysis areas, the echo data resulting from the unnecessary target objects may be removed by the wave component extracting module <NUM>. That is, like this modification, even if the simple addition is performed without performing the weighted addition of the directional frequency spectrums generated corresponding to the analysis areas, since the unnecessary echoes have already been removed by the wave component extracting module <NUM>, the wave information may be calculated accurately similar to the above embodiment.

Claim 1:
A signal processing device (<NUM>) configured to process echoes from sea waves included in a detection area of a ship radar apparatus having an antenna unit (<NUM>) with an antenna (<NUM>) configured to receive echoes from sea waves included in a plurality of analysis areas (Z1-Z5) set within the detection area, such that as coordinate axes of the analysis areas (Z1-Z5), axes which are substantially parallel to directions from the ship (S) toward the central points of the analysis areas (Z1-Z5) are set;
the signal processing device (<NUM>) comprising:
a frequency area spectrum generating module (<NUM>) configured to carry out a frequency analysis of the echoes received by the antenna and generate 3D FFT directional frequency spectrums SZn for the plurality of analysis areas (Z1-Z5), respectively, each directional frequency spectrum being defined along the respective coordinate axis of the respective analysis area (Z1-Z5);
an integrating module (<NUM>) configured to integrate echo intensity indicated by each sampling point that constitutes each of the directional frequency spectrums while unifying directions included in coordinates of the directional frequency spectrum, and generate an integrated frequency area spectrum, the integrated frequency area spectrum being provided as spectral power Stotal (i,j) in an arbitrary direction i and at an arbitrary frequency j; and
a sea wave information calculating module (<NUM>) configured to calculate sea wave information that is information related to the sea waves included in the analysis areas (Z1-Z5) based on the integrated frequency area spectrum, respectively, wherein the integrating module (<NUM>) integrates the directional frequency spectrums SZn obtained by multiplying the echo intensities at the sampling points by weight coefficients determined for the plurality of directional frequency spectrums, respectively.