JP5139725B2 - Radar equipment - Google Patents

Description

  The present invention transmits radio waves a plurality of times, receives a plurality of reflected waves from a target corresponding to the plurality of transmitted waves, and receives the object from a plurality of received signal values corresponding to the plurality of reflected waves. The present invention relates to a radar device that measures the distance and direction to a target, and more particularly to a radar device that is suitable for use in ships.

  FIG. 8 is a block diagram illustrating a configuration example of the radar apparatus 1 according to the related art.

  In the radar apparatus 1, a transmission signal from the transmitter 6 is transmitted as a radio wave through the duplexer 8, the rotary joint 4, and the antenna 10 to the antenna 10 that is rotated in the horizontal direction through the motor 2 and the rotary joint 4. The reflected wave from the target with respect to is received by the antenna 10. The reflected wave received by the antenna 10 is converted into a reception signal by the receiver 12 through the rotary joint 4 and the duplexer 8, envelope-detected by the logarithmic detector 14, and then quantized and digitized by the A / D converter 16. The received signal value (sweep data) is stored in the sweep memory 18 according to the distance R (using the distance R as an address). The sweep memory 18 stores sweep data related to one sweep (related to one transmission / reception).

  On the other hand, the rotation of the antenna 10 is detected by the encoder 20 and the direction counter 22, and an angle signal indicating the direction θ of the antenna 10 is supplied to the coordinate converter 24.

  The coordinate converter 24 is a circuit that transfers and stores the sweep data stored on the sweep memory 18 to the radar image memory 26, and generates a write address at that time according to the azimuth θ and the distance R. Thereby, the data concerning the radar image is converted from the polar coordinate format to the orthogonal coordinate format.

  The data for one scan stored in the radar image memory 26 (the data for 360 ° of the sweep memory 18) is converted into a video signal through the display readout circuit 28 and supplied to the display unit 30, and is displayed on the screen of the display unit 30. The radar image is displayed in the PPI method.

  By the way, in the radar apparatus 1 mounted on a ship or the like, in general, the resolution in the azimuth direction (azimuth resolution) depends on the horizontal beam width of the antenna, and the resolution in the distance direction (distance resolution) depends on the transmission pulse width. (Patent Document 1).

  For example, when the horizontal beam width (half-value angle of the radiation characteristic) is 3 °, it is difficult to obtain an azimuth resolution of 3 ° or more, and when the transmission pulse width is 100 ns, a distance of 20 m or more can be obtained. It is difficult.

  In order to increase the azimuth resolution, it is necessary to increase the antenna length and reduce the horizontal beam width. In order to increase the distance resolution, it is necessary to shorten the transmission pulse width.

Japanese Patent Laying-Open No. 2005-147834 (paragraph [0002])

  However, increasing the length of the antenna increases the weight of the antenna and the size of the antenna. Therefore, it is necessary to strengthen the structure of the antenna driving device that supports and rotates the antenna. The cost increases and it becomes difficult to mount on a small ship. Further, if the transmission pulse width is shortened, it is necessary to increase the frequency of the transmission pulse generating circuit, which increases the cost including measures against heat.

The present invention has been made in consideration of such problems, and can easily improve the azimuth resolution , or the azimuth resolution and the distance resolution without changing the antenna structure, the structure of the antenna driving device, and the transmission pulse width. An object of the present invention is to provide a radar device that can be made to operate.

  It is another object of the present invention to provide a radar device that can shorten the length of an antenna if the azimuth resolution is the same.

The radar apparatus according to the present invention transmits a plurality of radio waves, receives a plurality of reflected waves from a target corresponding to the plurality of transmitted waves, and receives a plurality of received signals corresponding to the plurality of reflected waves. In a radar apparatus that measures the distance and direction from a value to the target, formed by a plurality of received signal values from the target , along the azimuth direction, or along the azimuth direction and distance direction , the maximum value detecting means for obtaining the maximum value of the response characteristic of the convex upwardly (maximum value), without changing the maximum value of the response characteristic of the convex along the azimuth direction or the azimuth A calculation process is performed in which the received signal values in the vicinity of both of the maximum values along the direction and the distance direction gradually become smaller values , along the azimuth direction, or along the azimuth direction and the distance direction. Te, the convex shape steeper A shape, the lateral resolution, or, characterized in that it comprises, a resolution enhancement computation means for improving the lateral resolution and axial resolution.

According to this invention, it is formed by a plurality of received signal values from the target obtained by the maximum value detecting means , along the azimuth direction, or along the azimuth direction and the distance direction, and protrudes upward. The maximum value of the response characteristic of the shape is calculated by the resolution improvement calculation means, and the received signal values in the vicinity of both of the maximum values are gradually changed to smaller values without changing the maximum value, and the azimuth direction The azimuth resolution or the azimuth resolution and the distance resolution can be improved by making the convex shape steeper along the azimuth direction and the distance direction .

  Here, it is possible to improve the azimuth resolution by the inter-sweep process and the distance resolution by the distance direction process.

  Since the present invention can be applied to a radar that can obtain distance data for each transmission direction, it can be applied not only to a pulse radar system but also to an FMCW radar system as an applicable radar system.

Here, the resolution improvement calculation means sets the maximum value as Max, the constant as K (K> 0), the exponent as n (n> 0), the output value after the calculation process as Y, and has a certain azimuth direction. When one received signal value constituting each of the plurality of received signal values from the target at a distance is X, the equation Y = X−K × (Max−X) ⁿ (when X is Max, Y = X = Max)
To obtain the output value Y.

  As can be understood from this equation, by increasing the value of the constant K, the received signal values in the vicinity of both of the maximum values are gradually reduced to a smaller value without changing the maximum value of the response characteristic having an upward convex shape. And the convex shape upward can be made steeper. In addition, when the value of the index n is large, the value near the maximum value can be changed by the value of the index n because the value of Max-X is less than 1 and becomes a smaller value.

For example, the formula Y = X−0.5 × (Max−X) ² with K = 0.5 and n = 2, or the formula Y = X−2 × (K = 2 and n = 1. It was confirmed that a certain resolution improvement effect can be obtained by using (Max-X). It was confirmed that the value of K was 0.5 to 2 and the value of n was 1 to 2 within a preferable balanced range.

  Note that variable means for changing at least one of the constant K and / or the exponent n and the number of received signal values to be used for calculation may be provided.

According to the present invention, the azimuth resolution or the azimuth resolution and the distance resolution can be improved by calculation without changing the structure of the antenna, the structure of the antenna driving device, and the transmission pulse width.

  In addition, the present invention can use a short antenna with the same azimuth resolution.

In other words, since the azimuth resolution , or the azimuth resolution and the distance resolution can be improved by calculation, the azimuth resolution can be improved at a low cost without changing the length of the antenna.

  In addition, if the azimuth resolution is the same, the length of the antenna can be shortened, so that the antenna can be reduced in size and weight. Furthermore, since the rotational moment of the antenna is reduced, the structure of the antenna driving device can be simplified and at the same time the power consumption of the circuit of the antenna driving device can be reduced. Including the rotary joint, mechanical and electrical reliability can be improved. A small and lightweight antenna can be easily mounted on a small ship.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings to be referred to below, those corresponding to those shown in FIG. 8 are given the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a block diagram showing a configuration of a radar apparatus 50 according to an embodiment of the present invention.

  The radar apparatus 50 is basically different from the radar apparatus 1 shown in FIG. 8 in that it includes a resolution improvement calculation unit 70. The resolution improvement calculation unit 70 includes an azimuth direction delay circuit 52, a maximum value detector 54, and a resolution improvement calculation unit 64.

  In FIG. 1, a radar apparatus 50 includes an antenna 10 provided at a place with a good view such as a ship. The antenna 10 rotates at a predetermined speed in the horizontal direction through the motor 2 and the rotary joint 4, and transmits a transmission wave as a radio wave by a transmission signal supplied from the transmitter 6 through the duplexer 8 and the rotary joint 4 for each predetermined angle (predetermined direction). Radiates to. That is, the transmission wave is radiated many times by one rotation of the antenna 10. In addition, the reflected wave from the target with respect to each transmission wave is received by the antenna 10, received by the receiver 12 through the rotary joint 4 and the duplexer 8, and envelope-detected by the logarithmic detector 14. The detection signal is quantized and digitized by the A / D converter 16 and supplied to the azimuth delay circuit 52 as a received signal value (sweep data). The logarithmic process may be performed by numerical calculation after A / D conversion.

  The azimuth delay circuit 52 refers to a plurality of sweep memories 56 corresponding to an azimuth angle to be calculated by referring to the azimuth at a time, for example, an azimuth angle in a range covering a horizontal beam width (hereinafter referred to as an azimuth angle range). It is configured. In this embodiment, since the horizontal beam width is assumed to be 2.7 [deg], the azimuth direction for storing a plurality of received signal values to be referred to in order to detect the maximum value by the maximum value detector 54 at the next stage is stored. Thus, a sweep memory 56 for storing received signal values (20 pieces of sweep data) for an azimuth angle range of 2 [deg] is connected in series. Since the reception signal value (sweep data) directly supplied from the A / D converter 16 to the maximum value detector 54 is also referred to at the same time, 21 reception signal values (sweep data) are referred to. .

  For each transmission trigger, the received signal value (sweep data) is transferred to the next-stage sweep memory 56 and overwritten.

  The maximum value detector 54 receives the received signal value X from the sweep memory 56c at the center (the center of a reference range p + q + 1 described later), in other words, from the direction (referred to as the direction) from which the received signal value is to be obtained. A reception signal value X and a reception signal value X from each direction in the vicinity of the direction are supplied.

  The maximum value detector 54 detects the maximum value Max for each equidistance of the reception signal value (sweep data) from the plurality of reception signal values X, and supplies the maximum value Max to the subtractor 57 constituting the resolution improvement calculator 64.

In this embodiment, the resolution improvement computing unit 64 includes a subtracter 57, a squarer 58, and a multiplier 60 that is a constant (resolution improvement coefficient) K (K> 0, where K = 0.5). As a sweep data output value Y obtained by processing (calculating) the received signal value X, which is each sweep data, on the output side of the subtractor 62, the following equation (1) is formed. The output value Y calculated by (resolution improvement formula) is obtained.
Y = X−K × (Max−X) ² {When X is Max, Y = X = Max}
= X-0.5 × (Max-X) ² (1)

  The output value Y is supplied to one input port of the coordinate converter 24.

Actually, the equation (1) is obtained by using the received signal value X (i, j) at a certain distance in a certain azimuth direction {data at the i-th distance of the j-th sweep}, and its maximum value Max (i, j). , The front side p sweep and the rear side q sweep of the central sweep, and a total of p + q + 1 (here, p = q = 10 and 21 in total as described above) is referred to, and the maximum value Max ( (1a) is used to obtain the output value Y (i, j) using i, j). The general formula is shown in (1b).
Y (i, j) = X (i, j) −0.5 × {Max (i, j) −X (i, j )} ²
... (1a)
Y (i, j) = X (i, j) −K × {Max (i, j) −X (i, j )} ⁿ
... (1b)

  On the other hand, rotation of the antenna 10 is detected through the rotary joint 4 and the encoder 20, and an angle signal indicating the transmission / reception azimuth θ of the antenna 10 is input from the azimuth counter 22 having the gyrocompass to the other input of the coordinate converter 24 for each sweep. Supplied to the port.

  The coordinate converter 24 performs a write address operation on the sweep data related to the output value Y (i, j) corresponding to the received signal value X (i, j) of the central sweep memory 56c, and polar coordinates polar coordinates The data is converted from the format into a rectangular coordinate format and stored in the radar image memory 26.

  The sweep memory 56 is a memory that stores sweep data related to one sweep, and the radar image memory 26 is a frame memory that has a storage space corresponding to the screen of the display unit 30.

  The data written in the radar video memory 26 is read by the display reading circuit 28 on the raster scan type display unit 30 so that the PPI display by the raster scan method is suitably performed.

  That is, the data for one scan (360 ° data) stored in the radar video memory 26 is converted into a video signal through the display readout circuit 28, supplied to the display unit 30, and on the screen of the display unit 30, Radar video is displayed in PPI format.

  Next, the resolution improvement method by the resolution improvement calculation unit 70 will be described in detail using simulation results.

  Two targets A and B (both targets A and B are point targets) exist at the same distance from the ship and at an interval of 2.5 [deg] in the direction, and the S band. (3 [GHz]), the length of the antenna 10 is assumed to be 8 ft (≈2.4 [m]), and the horizontal beam width is assumed to be 2.7 [deg].

  At this time, since the horizontal beam width is not 0 [deg] but finite as 2.7 [deg] (becomes wide), the response characteristic 100 indicated by the dotted line in FIG. For the target B, the response characteristic 102 indicated by the one-dot chain line in FIG. 2 is obtained. The response characteristics 100 and 102 are formed by a plurality of received signal values, and are upwardly convex characteristics with the positions of the targets A and B being the maximum values (maximum values).

  In FIG. 2, the maximum value Max of the target A exists at the standardized position of the azimuth angle 0 [deg], and the maximum value MAX of the target B exists at the position of the azimuth angle 2.5 [deg].

  FIG. 3 shows a response characteristic 104 obtained by synthesizing the response characteristic 100 and the response characteristic 102 when the processing by the resolution improvement calculation unit 70 is not performed. In this response characteristic 104, the amount of drop from the maximum value Max at the intersection in the vicinity of the intermediate angle 1.25 [deg] between the azimuth angles of the targets A and B is about −5 [dB].

  In general, in the radar device 50, it is found that the amount of drop is required to be about −10 [dB] or more in order to distinguish and display the adjacent targets A and B on the screen of the display unit 30 by luminance modulation or the like. When the processing by the resolution improvement calculation unit 70 is not performed, the targets A and B adjacent to each other with the azimuth angle difference 2.5 [deg] applied to the response characteristic 104 in FIG. The targets A and B cannot be distinguished from each other on the screen of the display unit 30.

  On the other hand, in this embodiment, when the output value Y is obtained in the reference range p + q + 1 = 2 [deg] using the above equation (1) as the resolution improvement by the resolution improvement computing unit 64, the target A, The maximum value Max of B does not change. {When X = Max, the second term on the right side of the above equation (1) has a zero value, so the output value Y becomes Y = Max. } The convex shape above the characteristics 100 and 102 can be made a steeper convex shape.

  FIG. 4 shows a response characteristic obtained by synthesizing the response characteristic 100 and the characteristic after the calculation process of the response characteristic 102 (a characteristic of a steeper convex shape) when the processing by the resolution improvement calculation unit 70 is performed using the expression (1). 106 is shown.

  In the synthesized response characteristic 106, the drop amount from the maximum value Max at the intersection in the vicinity of the angle 1.25 [deg] between the adjacent targets A and B is as large as about −18 [dB]. Since the amount becomes a value of −10 [dB] or more, the adjacent targets A and B can be clearly identified on the screen of the display unit 30, and the horizontal resolution is improved.

  As a specific numerical example, when the resolution improvement calculation is performed using the equation (1), even if the horizontal beam width is 2.7 [deg], the resolution is at least an azimuth difference of 2.5 [deg] or more. Can be obtained.

  As described above, in the embodiment described above, by performing the calculation process in the resolution improvement calculation unit 70, the azimuth resolution is improved, the S band (3 [GHz]), and the length of the antenna 10 is 8 ft (≈2.4). [M]), when the horizontal beam width is 2.7 [deg], the adjacent targets A and B can be sufficiently identified with an azimuth difference of 2.5 [deg].

  FIG. 5 is a simulation view illustrating a comparative example (an example in which resolution improvement processing is not performed) in which the antenna length necessary to recognize adjacent targets A and B with an azimuth difference of 2.5 [deg] is calculated. is there. In the example of FIG. 5, when the length of the antenna is increased by about 50% to 12 ft (≈3.6 [m]) and the horizontal beam width is 1.9 [deg], The drop amount from the maximum value Max at the intersection near the angle 1.25 [deg] is −10 [dB], and the azimuth difference 2.5 [dB] can be identified on the screen of the display unit 30.

  Considering the results of the above embodiment (response characteristic 106 in FIG. 4) and the comparative example (response characteristic 108 in FIG. 5), the length of the antenna 10 is set to 12 ft in order to ensure the same horizontal resolution of 2.5 [deg]. (Comparative example in FIG. 5) can be shortened to 8 ft (the embodiment in FIG. 4) and 2/3, so that the antenna 10 can be reduced in size and weight. Further, since the rotational moment is reduced due to the shortening of the length of the antenna 10, the structure of the antenna driving device can be simplified and the power consumption of the circuit of the antenna driving device can be reduced. The mechanical and electrical reliability including the rotary joint 4 can be improved. The small and lightweight antenna 10 can be easily mounted on a small ship.

  In the embodiment of FIG. 4, since the azimuth difference between the maximum values Max of the targets A and B is 2.5 [deg], the reference range (the number of sweep memories 56 + 1) is 2.5 [deg]. It can be seen that the targets A and B cannot be distinguished unless the value is less than.

  In this embodiment, the reference range (the number of a plurality of received signal values used for the calculation) is about 0.75 times the horizontal beam width 2.7 [deg] (2 / 2.7≈0.75). However, it may be about 1 time (2 [deg]) to 0.5 times (1 [deg]) of the horizontal beam width.

  If the reference range is too narrow, there is a possibility that the targets A and B, which are signals, and noise cannot be distinguished. The reference range may be variable between 0.5 times and horizontal beam width times.

  In the general formula (1b), the constant K of the multiplier 60, the exponent n of the power generator substituted for the squarer 58, and the reference range are variable means (input volume or switch that can be operated by the user). Etc.), it is possible to make the configuration variable by the user. In this embodiment, the resolution improvement calculation unit 70 can be configured by a microcomputer or a digital signal processor.

  FIG. 6 shows that there are two targets A and B ′ having an amplitude difference (response difference) of 20 [dB] at intervals of 4.0 [deg] at the same position from the ship, and a horizontal beam. When the width is 2.7 [deg], the S band (3 [GHz]), the length of the antenna 10 is 8 ft (≈2.4 [m]), and the reference range is p + q + 1 = 2 [deg], the above equation (1) The other example at the time of performing resolution improvement calculation using is shown.

  In this case, in the response characteristics 100 and 108 when the processing by the resolution improvement calculation unit 70 according to the expression (1) is not performed, the drop amount at the intersection is about −6 [dB], which is difficult to identify. When the resolution improvement calculation processing is performed, the response characteristics 110 and 112 enable the targets A and B ′ to be more clearly identified. However, in the example of FIG. 6, if the reference range m + n + 1 is set to 4 [deg] or more, the target B ′ disappears due to the arithmetic processing, so the reference range is less than the horizontal beam width 2.7 [deg]. Set to the value of.

  In the above-described embodiment, the resolution improvement process in the azimuth direction has been described. However, the resolution improvement process in the distance direction can be performed in the same manner.

  FIG. 7 shows a configuration of a radar apparatus 150 in which the azimuth direction resolution improvement calculation unit 70 in FIG. 1 is replaced with a distance direction resolution improvement calculation unit 170. In this case, the azimuth direction delay circuit 52 in FIG. 1 is replaced with a distance direction delay circuit 152, and the sweep memory 56 is replaced with a register 156 that sequentially stores received signal values related to reflected waves in the distance direction. The If the reference range is substituted from the azimuth range to the distance range, the distance resolution can be similarly improved using the above equation (1).

  Of course, by referring to the two dimensions (distance direction and azimuth direction), the resolution in both the azimuth direction and the distance direction can be improved simultaneously.

  Further, the present invention can be applied not only to a pulse radar device as a radar device but also to an FM-CW radar device. In the FM-CW radar device, if a continuous wave is frequency-modulated and transmitted, and a part of the transmitted wave is mixed with a received wave reflected from an object, a beat wave proportional to the delay time that the radio wave reciprocates Occurs. When the beat signal is subjected to frequency analysis, the frequency corresponds to the distance to the object, and the amplitude (intensity) corresponds to the scattering intensity of the object. In this FM-CW radar apparatus, the resolution improvement processing according to the above equation (1) can be applied to the distance.

  Thus, for example, the radar apparatus 50 according to the above-described embodiment transmits a radio wave a plurality of times, receives a plurality of reflected waves from the targets A and B corresponding to the plurality of transmission waves, and receives the plurality of times. A radar apparatus for measuring the distance and direction from a plurality of received signal values X corresponding to the reflected wave of the target to the targets A and B, and formed above by the plurality of received signal values X from the targets A and B The maximum value detector 54 (maximum value detecting means) for obtaining the maximum value Max of the convex response characteristics 100 and 102, and the maximum value Max without changing the maximum value Max of the convex response characteristics 100 and 102. A resolution improvement computing unit 64 (resolution improvement computing means) is provided that performs computation processing for gradually decreasing the received signal value X in the vicinity to make the convex shape steeper and improve the resolution.

  That is, the maximum value Max of the response characteristics 100 and 102 having an upwardly convex shape formed by the plurality of received signal values X from the targets A and B, which is obtained by the maximum value detector 54, is used as the resolution improvement computing unit 64. Thus, a calculation process is performed in which the received signal values X in the vicinity of both of the maximum values Max gradually become smaller without changing the maximum value Max, and the response characteristics having a steeper shape than the response characteristics 100 and 102 having the convex shape. By setting it to 106, the resolution can be improved. In this case, it is possible to improve the azimuth resolution by the inter-sweep process and the distance resolution by the distance direction process.

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification.

It is a block diagram which shows the structure of the radar apparatus which improves the resolution | decomposability of the azimuth | direction direction which concerns on one Embodiment of this invention. It is explanatory drawing (the 1) of the response characteristic before a resolution improvement process. It is explanatory drawing (the 2) of the response characteristic before a resolution improvement process. It is explanatory drawing of the response characteristic after a resolution improvement process. It is explanatory drawing of the response characteristic of the comparative example when antenna length is lengthened. It is explanatory drawing of the other example of a resolution improvement process. It is a block diagram which shows the structure of the radar apparatus which improves the resolution of the distance direction which concerns on other embodiment of this invention. It is a block diagram which shows the structural example of the radar apparatus which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 50, 150 ... Radar apparatus 10 ... Antenna 52 ... Azimuth direction delay circuit 54 ... Maximum value detector 56, 56c ... Sweep memory 64 ... Resolution improvement calculators 70, 170 ... Resolution improvement calculation part

Claims (2)

Transmitting radio waves multiple times, receiving multiple reflected waves from the target corresponding to the multiple transmitted waves, and the distance from the plurality of received signal values corresponding to the multiple reflected waves to the target And a radar device for measuring the direction,
Maximum value detecting means for obtaining the maximum value of the response characteristic having an upwardly convex shape along the azimuth direction, or along the azimuth direction and the distance direction, formed by a plurality of the received signal values from the target When,
Without changing the maximum value of the response characteristic of the convex shape, the received signal values in the vicinity of both of the maximum values along the azimuth direction or along the azimuth direction and the distance direction gradually increase. Perform arithmetic processing to be a small value, and make the convex shape steeper along the azimuth direction, or along the azimuth direction and the distance direction, and the azimuth resolution, or the azimuth resolution and the distance resolution. A resolution improvement calculation means for improving
Equipped with a,
The resolution improvement calculation means includes:
The maximum value is Max, the constant is K (K> 0), the exponent is n (n> 0), the output value after the arithmetic processing is Y, and a plurality of targets from a certain distance in a certain azimuth direction When each received signal value constituting the received signal value is X, an expression
Y = X−K × (Max−X) ⁿ (when X is Max, Y = X = Max)
Radar apparatus according to claim Rukoto obtains an output value Y by. The radar apparatus according to claim 1 , wherein
The resolution improvement calculation means includes:
A radar apparatus comprising: variable means for changing at least one of the constant K, the exponent n, and the number of the received signal values used for calculation.

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