JP2011220824A - Radar device - Google Patents

Abstract

A radar apparatus capable of extracting a target signal with high accuracy even when an observation signal is acquired in a relatively strong clutter environment.
An average value in each range bin is calculated by a moving average process using a radar signal acquisition unit for acquiring an observation signal by transmitting and receiving radio waves and a target size window to be extracted based on the observation signal. The moving average processing unit 40, the average value of each range bin calculated by the moving average processing unit 40 are compared, and the target signal extraction processing unit 50 that extracts the region where the target signal is located, and the target signal extraction processing unit 50 And an output storage unit 60 for storing the output result.
[Selection] Figure 1

Description

  The present invention relates to a radar apparatus having a function of detecting and extracting a stationary target on the ground or the sea, and in particular, is mounted on a platform such as an aircraft and observes the vicinity of the ground surface and the sea surface by transmitting and receiving radio waves from the sky. The present invention also relates to a radar apparatus that detects and extracts a target existing near the ground surface or the sea surface.

  In general, in radar equipment, when observing the ground surface and sea surface by transmitting and receiving radio waves from the sky, in addition to the target signal (the reflected wave from the target), ground clutter or sea clutter (hereinafter referred to as the ground clutter) In some cases, an unnecessary reflected wave from the “clutter” is observed.

  In particular, as shown in FIG. 15, when observing the ground target T from the radar apparatus 100 mounted on the aircraft, not only the reflected signal Wt from the target T but also a strong reflected signal from the clutter (ground) C. Since Wc is observed, there is a problem that the extraction accuracy in detecting the target T from the observation signal (referred to as a range profile or power range profile) indicating the received signal strength in the range (distance) direction is lowered. .

Note that even in the environment of FIG. 15, if the target T is moving, the Doppler frequencies of the reflected signal Wc from the clutter C and the reflected signal Wt from the target T are different from each other. Thus, the clutter C and the target T can be separated.
However, when the target T is stationary, the Doppler frequencies of the target T and the clutter C are not different from each other, making it difficult to detect and extract the target T.

  Therefore, in order to prevent erroneous detection of the target T when the reflected signal Wc from the clutter C shows a high power value, a technique for extracting the target signal using a window and a threshold value has been conventionally proposed ( For example, see Patent Document 1).

  FIG. 16 is a functional block diagram showing a target signal extraction procedure by the conventional radar apparatus described in Patent Document 1. In FIG. In FIG. 16, the conventional radar apparatus 100 includes a radar signal acquisition unit 1, a window processing unit 2, a target signal determination processing unit 3, and an output storage unit 4.

15 and 16, first, the radar signal acquisition unit 1 performs observation using a radar device 100 mounted on an aircraft, and acquires an observation signal (range profile).
Subsequently, the window processing unit 2 performs signal processing based on a comparison with a preset threshold for the range profile included in the predetermined window. Specifically, the window processing unit 2 determines that a signal indicating power (amplitude) higher than the threshold is a signal from the target T.

Next, the target signal determination processing unit 3 determines whether the observation signal in the window is a signal from the target T using the threshold processing result from the window processing unit 2.
Here, when the range profile (observation signal) included in the window is detected as a target signal in all the range bins, it is determined that “the observation signal included in the window is a signal from the target T”. If the target signal is not detected in some range bins in the window, it is determined that the signal is from the clutter C.
Finally, the output storage unit 4 stores the output result from the target signal determination processing unit 3.

Japanese Patent Laid-Open No. 61-280586

  When the conventional radar apparatus described in Patent Document 1 extracts a target signal from an observation signal, the target signal is extracted by signal processing based on a threshold value that is reduced by a predetermined power (or a predetermined amplitude) from the maximum value of the observation signal. Since the signal is extracted, if the observation signal is acquired in an environment where the reflected signal level from the clutter is relatively high, there is a problem that the extraction accuracy of the target decreases because the clutter is erroneously extracted. .

  The present invention has been made to solve the above problems, and by using power range profiles (or polarization information) observed at different angles and target information to be extracted, It is an object of the present invention to obtain a radar apparatus that can extract a target signal with high accuracy even when an observation signal is acquired in a relatively strong environment of clutter.

  A radar apparatus according to the present invention includes a radar signal acquisition unit that transmits and receives radio waves to acquire an observation signal, and a moving average process using a window of a target size to be extracted based on the observation signal. A moving average processing unit that calculates a value, an average value of each range bin calculated by the moving average processing unit, and a target signal extraction processing unit that extracts a region where the target signal is located, and an output from the target signal extraction processing unit And an output storage unit for storing the result.

  According to the present invention, even when an observation signal is acquired in an environment where the reflection signal level from the clutter is relatively high, the target signal can be extracted with high accuracy.

It is a functional block diagram which shows schematic structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the specific structure of the radar signal acquisition part in FIG. It is explanatory drawing which shows the power range profile by the target detection process part in FIG. It is explanatory drawing which shows notionally the operation | movement of the target detection process part in FIG. It is explanatory drawing which shows the search range by the search range setting process part in FIG. It is explanatory drawing which shows the window in the search range by the moving average process part in FIG. It is a functional block diagram which shows schematic structure of the radar apparatus which concerns on Embodiment 2 in this invention. It is a block diagram which shows the specific structure of the multi-polarization observation signal acquisition part in FIG. It is explanatory drawing which shows the determination process of the target signal extraction range by Embodiment 2 of this invention. It is explanatory drawing which shows the determination process of the target signal extraction range by Embodiment 2 of this invention. It is a functional block diagram which shows schematic structure of the radar apparatus based on Embodiment 3 in this invention. It is a block diagram which shows the specific structure of the multiple radar signal acquisition part in FIG. It is explanatory drawing which shows typically the relationship between the radar apparatus and target in Embodiment 3 of this invention. It is explanatory drawing which shows the beam pattern of the reflected signal in Embodiment 3 of this invention. It is explanatory drawing which shows the relationship between the conventional radar apparatus and a target typically. It is a functional block diagram which shows the target signal extraction procedure by the conventional radar apparatus.

Embodiment 1 FIG.
FIG. 1 is a functional block diagram showing a schematic configuration of the first embodiment of the present invention. In the first embodiment of the present invention, the relationship between the radar apparatus 100 and the target T is as shown in FIG.

  In FIG. 1, a radar apparatus according to Embodiment 1 of the present invention includes a radar signal acquisition unit 10, a target detection processing unit 20, a search range setting processing unit 30, a moving average processing unit 40, and a target signal extraction process. Unit 50 and an output storage unit 60.

The radar signal acquisition unit 10 performs observation using a radar mounted on an aircraft and acquires a range profile (observation signal).
The target detection processing unit 20 detects the target T in the range profile stored in the reception signal storage unit 15 (described later together with FIG. 2) in the radar signal acquisition unit 10.

The search range setting processing unit 30 uses the detection result of the target detection processing unit 20 to set a search range for target extraction in the range profile (described later with reference to FIG. 5).
The moving average processing unit 40 includes a window determination processing unit, and determines a window size for extracting a target signal based on information such as a target size to be extracted.

  The moving average processing unit 40 performs a moving average process using the window set by the window determination processing unit in the search range set by the search range setting processing unit 30.

The target signal cutout processing unit 50 extracts an area including the target in the observation signal (power range profile) using the average value of the observation signal at each position calculated by the moving average processing unit 40 as an index.
The output storage unit 60 stores the output result of the target signal extraction processing unit 50.

FIG. 2 is a block diagram showing the configuration of the radar signal acquisition unit 10 in FIG.
In FIG. 2, a radar signal acquisition unit 10 includes a transmitter 11 that generates a pulse signal, a transmission / reception switch 12 that switches a transmission / reception direction of the pulse signal from the transmitter 11, a transmission / reception antenna 13, a receiver 14, and a reception. The reception signal storage unit 15 stores the digital reception signal (observation signal) from the machine 14.

  The transmission / reception antenna 13 radiates a pulse signal input from the transmitter 11 via the transmission / reception switch 12 to the space and receives a reflected signal scattered by the observation target.

The receiver 14 stores the scattered wave (reflected signal) received from the transmission / reception antenna 13 via the transmission / reception switch 12 in the reception signal storage unit 15 as a digital reception signal.
The reception signal storage unit 15 temporarily stores the digital reception signal (observation signal) subjected to reception processing by the receiver 14.

Next, the processing operation according to the first embodiment of the present invention shown in FIG. 1 will be described with reference to FIGS. 3 to 6 together with FIGS.
First, the operation of the radar signal acquisition unit 10 shown in FIG. 2 will be described.
In FIG. 2, the pulse signal generated by the transmitter 11 is sent to the transmission / reception antenna 13 via the transmission / reception switch 12. The transmission / reception antenna 13 radiates the pulse signal generated by the transmitter 11 to space.

  The pulse signal radiated to the space is scattered by the observation target (target T, clutter C), and the reflected signals (Wt, Wc) scattered by the observation target are received by the transmission / reception antenna 13. Further, the scattered wave (reception signal) from the observation target received by the transmission / reception antenna 13 is input to the receiver 14 via the transmission / reception switch 12.

  The receiver 14 performs a phase detection process and an A / D conversion process on the received signal, generates a digital received signal indicating the amplitude and phase of each received signal, and temporarily stores it in the received signal storage unit 15 as an observation signal Let

The reception signal (observation signal) stored in the reception signal storage unit 15 can be represented by S (n) corresponding to the range bin n. Here, n (= 1, 2,..., N) is an observation bin number in the range direction, and N is the number of range bins.
The received signal S (n) stores the amplitude and phase in each range bin n.

Next, as shown in FIG. 1, the observation signal (received signal from the observation target) acquired by the radar signal acquisition unit 10 is sent to the target detection processing unit 20.
The target detection processing unit 20 calculates the received power in each range bin n using the received signal S (n) (range profile), and obtains the distribution (power range profile) of the received power in the range direction. Although the power value is used here, the amplitude may be used.

FIG. 3 is an explanatory diagram showing a power range profile. In FIG. 3, the horizontal axis indicates a range, and the vertical axis indicates power (power) P.
The power P (n) in each range bin n is expressed as the following equation (1).

Next, the target detection processing unit 20 searches for a range bin n ^tgt _max indicating the power maximum value P _max from the power P (n) calculated as in Expression (1) as in Expression (2) below. .

は、ある関数ｆ（ｎ）を最大にする「ｎ」を求める演算子である。
図４は目標検出処理部２０の動作を概念的に示す説明図であり、電力最大値Ｐ_ｍａｘを示すレンジビンｎ^ｔｇｔ _ｍａｘを示している。 In equation (1),

Is an operator for obtaining “n” that maximizes a certain function f (n).
FIG. 4 is an explanatory diagram conceptually showing the operation of the target detection processing unit 20, and shows the range bin n ^tgt _max indicating the power maximum value P _max .

  Here, the target observed in the range profile is a single target, and the maximum value in the power range profile is based on the assumption that the maximum value of the target received signal is also the maximum in the observed range profile. This is explained as a signal from the target.

  Although detailed explanation here is omitted, in the case where there are multiple targets in the power range profile, the following target signal extraction procedure is performed after extracting the number of points of the assumed target. May be repeatedly executed.

Returning to FIG. 1, subsequently, the search range setting processing unit 30 cuts out a schematic search range Z for extracting a target signal from the received signal S (n) in advance.
FIG. 5 is an explanatory diagram showing the search range Z. The same reference numerals as those described above are assigned to the same components as those described above (see FIGS. 3 and 4).

In FIG. 5, the search range Z cut out by the search range setting processing unit 30 is an area centered on the detected target maximum bright spot (range bin n ^tgt _max ).
The search range Z is extracted as in the following expression (3) according to the target size R _tgt to be observed.

When the radar apparatus has sufficient memory and calculation functions, the following target signal extraction processing of the following moving average processing unit 40 and target signal extraction processing unit 50 is immediately performed on the acquired power range profile. Therefore, the processing of the target detection processing unit 20 and the search range setting processing unit 30 is not necessarily required and can be omitted.
However, under the environment of the radar device 100 (FIG. 15) mounted on an aircraft or the like, it is expected that there is a limitation on the capacity of the memory or the arithmetic device. Can be saved.

  Returning to FIG. 1, next, the moving average processing unit 40 uses a window of an arbitrary size set in advance for the power range profile in the search range Z extracted by the search range setting processing unit 30. The average value of the power range profiles included in the window in each range bin n is calculated.

The size of the window set at this time may be any size, but here it is assumed to be the target size R _tgt to be observed.
If there are multiple types of targets to be observed, it is possible to prepare a window with the maximum size for each target and a window with the size of each target, and perform moving average processing, etc. . Even when a plurality of windows are used, the following processing is executed for the size of each window, and expansion is easy.
The averaging process in the moving average processing unit 40 is expressed as the following expression (4).

Here, the average value calculated by the moving average processing unit 40 will be described with reference to FIG.
FIG. 6 is an explanatory diagram showing the windows in the search range Z, and shows the first average calculation position Z1, the second average calculation position Z2, and the third average calculation position Z3 corresponding to each window.
In FIG. 6, first to third average calculation positions Z1 to Z3 are areas for calculating the average value of the power range profile at different positions.

The target signal Zo is an area where the target signal to be observed is located in the power range profile.
Therefore, the average value at the second average calculation position Z2 in FIG. 6 is the result of calculating the average value of the target signal Zo.

Of the average values calculated at each of the average calculation positions Z1 to Z3, since the signal at the first average calculation position Z1 is a clutter signal, the average value calculated at the first average calculation position Z1 is the average value of the clutter. It is expected that
Similarly, the average value calculated at the third average calculation position Z3 is also expected to be an average value of clutter.

On the other hand, the average value calculated at the second average calculation position Z2 is expected to be the average value of the target signal.
That is, if “the signal power from the target shows a slightly higher value than the signal power from the clutter”, the second average calculation position is obtained when the average values at the positions Z1 to Z3 are compared. The average value calculated by Z2 indicates the highest value.

Returning to FIG. 1, next, the target signal cutout processing unit 50 specifies the range in which the target signal to be observed is located, using the average value of each position Z1 to Z3 calculated by the moving average processing unit 40 as an index. Then, a target signal included in the area is extracted.
Positions Z1 to Z3 (for example, width 7 m) corresponding to each window are larger than the range bin (for example, width 1 m) and each include a plurality of range bins. Further, the number of windows is not limited to three and can be set to an arbitrary number.

The extraction of the target signal at this time is performed by comparing the average value calculated in each window (each position Z1 to Z3) and extracting the signal included in the window position where the average value is maximum.
Therefore, the target signal S _tgt (n) is extracted as in the following equation (5).

N ^tgt in equation (5) represents a range bin whose average value is maximum, and is given by equation (6) below.

Finally, the output storage unit 60 stores the target signal S _tgt (n) extracted by the target signal cutout processing unit 50.

  As described above, the radar apparatus according to Embodiment 1 (FIGS. 1 and 2) of the present invention is based on the radar signal acquisition unit 10 that transmits and receives radio waves to acquire an observation signal (range profile), and the observation signal. The moving average processing unit 40 that calculates the average value in each range bin by the moving average process using the target size window to be extracted is compared with the average value of each range bin calculated by the moving average processing unit 40, and the target A target signal extraction processing unit 50 that extracts a region where a signal is located, and an output storage unit 60 that stores an output result from the target signal extraction processing unit 50 are provided.

In addition, the radar apparatus according to Embodiment 1 of the present invention includes a target detection processing unit 20 that detects a target signal based on an observation signal from the radar signal acquisition unit 10 and a target signal detected by the target detection processing unit 20. A search range setting processing unit 30 that cuts out the periphery of the target position and sets the search range Z of the target signal is provided.
The moving average processing unit 40 calculates an average value in each range bin based on the search range Z from the search range setting processing unit 30.

Thereby, after detecting a target using an observation signal (power range profile), based on information (size) of a target to be observed, a power range profile is subjected to a moving average process using a preset window, By comparing the calculated average values at the respective positions, it is possible to extract a signal included in the window at the position indicating the maximum average value as a target signal.
Therefore, even when all of the received power of the target signal does not indicate a value higher than that of the clutter, it is possible to extract the target signal with high accuracy.

Embodiment 2. FIG.
In the first embodiment (FIGS. 1 to 6), a single-polarized pulse signal is transmitted / received using a single transmitting / receiving antenna 13. However, as shown in FIGS. A pulse signal may be transmitted and received for each of a plurality of polarization channels using the dual polarization transmission / reception antennas 13a and 13b. In the second embodiment of the present invention, the relationship between the radar apparatus 100 and the target T is as shown in FIG.

FIG. 7 is a functional block diagram showing a schematic configuration of the second embodiment of the present invention. The same parts as those described above (FIG. 1) are denoted by the same reference numerals and detailed description thereof is omitted.
FIG. 8 is a block diagram showing a specific configuration of the multi-polarization observation signal acquisition unit 10A in FIG. 7, and the same parts as those in FIG. Is omitted.

  7, the radar apparatus according to Embodiment 2 of the present invention includes a multi-polarization observation signal acquisition unit 10 </ b> A in addition to the processing units 20 to 50 and the output storage unit 60 described above (FIG. 1), A signal processing unit 20A and a power range profile selection unit 50A are provided.

The multi-polarization observation signal acquisition unit 10A performs transmission / reception with a plurality of polarization channels, and stores the obtained range profile for each polarization channel.
Further, the polarization signal processing unit 20A applies polarization signal processing to range profiles in a plurality of polarization channels obtained by multi-polarization observation.
Further, the power range profile selection unit 50A selects a power range profile used for extracting the target signal from the results of the plurality of power range profiles.

  In FIG. 8, the multi-polarization observation signal acquisition unit 10A includes a first polarization transmission / reception antenna 13a and a second polarization transmission / reception in addition to the transmitter 11, the transmission / reception switch 12 and the receiver 14 described above (FIG. 2). An antenna 13b, a received polarization signal storage unit 15A, and a polarization switch 16 are provided.

The processing operation according to the second embodiment of the present invention shown in FIG. 7 will be described below with reference to FIGS. 9 and 10 together with FIG.
First, the operation of the multi-polarization observation signal acquisition unit 10A shown in FIG. 8 will be described.

In FIG. 8, when a pulse signal is input from the transmitter 11 via the transmission / reception switch 12, the polarization switch 16 drives only the first polarization transmitting / receiving antenna 13 a so that the first polarization pulse is transmitted. A signal is radiated into the space from the first polarization transmitting / receiving antenna 13a.
Further, the polarization switch 16 drives both the first and second polarization transmitting / receiving antennas 13a and 13b, and the scattered waves from the observation target are respectively transmitted to the first and second polarization transmitting / receiving antennas 13a and 13b. Receive.

Here, the polarization characteristics of the first and second polarization transmitting / receiving antennas 13a and 13b are orthogonal to each other.
Note that combinations of the polarization characteristics of the first and second polarization transmitting / receiving antennas 13a and 13b orthogonal to each other include combinations of vertical polarization and horizontal polarization, right-handed circular polarization and left-handed circular polarization. A combination with can be considered.

  Subsequently, the polarization switch 16 irradiates the observation target from the second polarization transmission / reception antenna 13b with the pulse signal input again from the transmitter 11 via the transmission / reception switch 12, and is scattered by the observation target. A wave is received by both the first and second polarization transmitting / receiving antennas 13a and 13b.

The received signal of the first polarization channel is defined as a signal transmitted by the first polarization transmitting / receiving antenna 13a and received by the first polarization transmitting / receiving antenna 13a.
Further, the received signal of the second polarization channel is a signal transmitted by the first polarization transmitting / receiving antenna 13a and received by the second polarization transmitting / receiving antenna 13b, and the received signal of the third polarization channel is the second polarized signal. It is defined as a signal transmitted by the wave transmitting / receiving antenna 13b and received by the second polarization transmitting / receiving antenna 13b.
Further, the received signal of the fourth polarization channel is defined as a signal transmitted by the second polarization transmitting / receiving antenna 13b and received by the first polarization transmitting / receiving antenna 13a.

Here, when the radar apparatus has a monostatic configuration and the positions of the polarization transmitting / receiving antennas 13a and 13b are equal, the signals of the second polarization channel and the fourth polarization channel are equal.
This is well-known in public literature (for example, Yamaguchi's "Radar Polarimetry Fundamentals and Applications-Remote Sensing Using Polarized Waves", The Institute of Electronics, Information and Communication Engineers, 2007).

Therefore, in the following description, the signal of the first polarization channel is used instead of the signal of the fourth polarization channel. Note that expansion is easy when the number of polarization channels is three or more.
The reception signals of the three polarization channels acquired as described above are temporarily stored in the reception polarization signal storage unit 15A via the transmission / reception switch 12 and the receiver 14.

  The received polarization signal storage unit 15A stores the scattering vector k (n) in each range bin n, and the scattering vector k (n) is expressed by the following equation (7).

In Expression (7), S _p (p = 1, 2, 3) is a complex number representing the signal of the p-th polarization channel.
As in equation (7), the signal in each range bin n is represented by a three-dimensional complex vector quantity. This complex vector expresses the polarization characteristics of the scattering in each range bin n, the direction of which is the polarization characteristics and the length represents the scattering intensity.

Next, in FIG. 7, the polarization signal processing unit 20A applies polarization signal processing to the range profile of each polarization channel acquired by the multi-polarization observation signal acquisition unit 10A.
As the polarization signal processing, calculation processing of total power that is the sum of all polarization power, clutter suppression processing, or the like can be considered.
Regarding clutter suppression processing, publicly known documents (for example, Suwa, Yamamoto, Nonaka, Imamura, Kirimoto, et al. “Target detection method using polarimetric notch filter”, IEICE (B) Vol. J87-B, no. 1 Pp 60-69, Jan. 2004).

Any of the above-described polarization signal processing techniques is well known, and any one or more of the polarization signal processing techniques may be applied as the polarization signal processing unit 20A. Does not matter here.
For example, the former calculation processing of the total power P ^all (n) is expressed by the following equation (8).

As shown in Expression (8), the total power P ^all (n) is a value defined by the square of the length of the scattering vector k (n), and is a value used as an index representing the scattering intensity.
P ^all (n) obtained by Expression (8) is a power range profile having a value of total power for each range bin n.

  Hereinafter, the power range profile selection unit 50A includes the power range profile in each polarization channel obtained by the multi-polarization observation signal acquisition unit 10A and the power range after the polarization signal processing calculated by the polarization signal processing unit 20A. Based on a plurality of power range profiles such as a profile, the final output is selected from each target position extraction result obtained by the target signal cutout processing unit 50.

FIG. 9 is an explanatory diagram showing a final determination method of the target signal extraction range Zo1, and shows a power range profile of the first polarization channel after the search range Z is set.
FIG. 10 is an explanatory diagram showing the final determination method of the target signal extraction range Zo2, and shows the power range profile of the second polarization channel after the search range Z setting processing.

  Here, a method of selecting a final result from a comparison of the results of two types of power range profiles of the reception signal of the first polarization channel and the reception signal of the second polarization channel will be described. Even when two or more power range profile results are input, the expansion is easy.

  In FIG. 9, the target signal cutout range Zo1 is a region where the target signal estimated from the power range profile observed in the first polarization channel is located, and the background signal range Zc1 is a region estimated to be clutter. is there.

  In FIG. 10, the target signal extraction range Zo2 is a region where the target signal estimated from the power range profile observed in the second polarization channel is located, and the background signal range Zc2 is a region estimated to be clutter. is there.

  In this case, as shown in FIG. 9, the signal clutter ratio SCR (Signal to Clutter Ratio) of the power range profile observed in the first polarization channel is high, and as shown in FIG. 10, in the second polarization channel. The signal clutter ratio SCR of the observed power range profile is assumed to be low.

Since the target signal extraction accuracy depends on the signal clutter ratio SCR, it is expected that the result estimated from the power range profile having a low signal clutter ratio SCR has low accuracy.
Therefore, the power range profile selection unit 50A selects a result to be finally output from the results of the two power range profiles shown in FIGS. 9 and 10 using the signal clutter ratio SCR as an index.

  The signal clutter ratio SCR of each power range profile used as an evaluation index is an area where the target signal is determined to be located (target signal extraction range Zo1, Zo2) and an area where the clutter is determined in each power range profile. It is calculated from the ratio of the average value to (background signal range Zc1, Zc2).

  Therefore, the signal clutter ratio SCRp of the power range profile is expressed as the following equation (9).

は、各パワーレンジプロフィールにおける目標領域の平均値である。
また、式（９）の分母

は、クラッタと判定された領域の平均値を表す。 In equation (9),

Is the average value of the target area in each power range profile.
Also, the denominator of equation (9)

Represents an average value of regions determined to be clutter.

  The power range profile selection unit 50A compares the signal clutter ratio SCRp of each power range profile calculated by Expression (9), and stores the maximum power range profile result in the output storage unit 60.

  As described above, the radar apparatus according to Embodiment 2 (FIGS. 7 and 8) of the present invention acquires a multipolarization observation signal that transmits and receives for each of a plurality of polarization channels and generates a multipolarization range profile. 10A, a polarization signal processing unit 20A that performs polarization signal processing on the multi-polarization range profile observed by the multi-polarization observation signal acquisition unit 10A, and a processing result from the polarization signal processing unit 20A. The moving average processing unit 40 that calculates an average value in each range bin by moving average processing using a window having a target size is compared with the average value of each range bin calculated by the moving average processing unit 40, and the target signal is positioned. A target signal extraction processing unit 50 for extracting a region to be processed, and a power level for selecting a final output result from the output results of a plurality of power range profiles from the target signal extraction processing unit 50 And a di-profile selection unit 50A.

The radar apparatus according to Embodiment 2 of the present invention includes a target detection processing unit 20 that detects a target signal based on a processing result from the polarization signal processing unit 20A, and a target signal detected by the target detection processing unit 20. A search range setting processing unit 30 for cutting out the periphery of the target position and setting the search range of the target signal.
The moving average processing unit 40 calculates an average value in each range bin based on the search range from the search range setting processing unit 30.

  In this way, by using the scattering vector k (n) observed by the multi-polarization radar device, the polarization characteristics of the target and the clutter can be compared with the comparison of only the scattering intensity by the single polarization described above. Differences and the like can be used, and the target signal can be extracted with high accuracy even in an environment that cannot be extracted by target detection according to the first embodiment (single polarization).

Embodiment 3 FIG.
In the first embodiment (FIGS. 1 to 6), the reception signal obtained by one transmission / reception is stored in the reception signal storage unit 15 in the radar signal acquisition unit 10, but FIG. 11 and FIG. As shown in FIG. 4, the reception signals obtained by a plurality of transmissions / receptions may be stored in the plurality of reception signal storage units 15B in the plurality of radar signal acquisition units 10B.

FIG. 11 is a functional block diagram showing a schematic configuration of the third embodiment according to the present invention. The same parts as those in FIG.
FIG. 12 is a block diagram showing a specific configuration of the multiple radar signal acquisition unit 10B in FIG. 11. The same parts as those described above (FIG. 2) are denoted by the same reference numerals and detailed description thereof is omitted. To do.

11, a radar apparatus according to Embodiment 3 of the present invention includes a plurality of radar signal acquisition units 10B, a plurality of data processing units, in addition to the processing units 20 to 50 and the output storage unit 60 described above (FIG. 1). 20B and a power range profile selection unit 50B.
The multiple radar signal acquisition unit 10B observes a plurality of transmission / reception signals, and the multiple data processing unit 20B processes observation signals obtained by multiple observations.

In FIG. 12, the multiple radar signal acquisition unit 10B includes a multiple reception signal storage unit 15B in addition to the transmitter 11, the transmission / reception switch 12, the transmission / reception antenna 13, and the receiver 14 described above (FIG. 2).
The multiple reception signal storage unit 15B temporarily stores multiple transmission / reception signals input from the receiver 14.

  Here, a case will be described in which a plurality of signals observed by a single-polarization radar apparatus are applied to the configuration of the first embodiment (FIGS. 1 and 2). The result of further observing the scattering matrix obtained by multi-polarization observation a plurality of times may be used by applying to the configuration of No. 2 (FIGS. 7 and 8). In this case, the received polarization signal storage unit 15A in the multi-polarization observation signal acquisition unit 10A described above (FIG. 8) may be changed to a multiple received polarization signal storage unit (not shown).

The processing operation according to the third embodiment of the present invention shown in FIG. 11 will be described below with reference to FIGS. 13 and 14 together with FIG.
First, the operation of the multiple radar signal acquisition unit 10B shown in FIG. 12 will be described.
In FIG. 12, a plurality of radar signal acquisition units 10B perform observation by transmitting and receiving a plurality of pulse signals, and temporarily store the reception signals obtained by each observation in the plurality of reception signal storage units 15B.

In FIG. 11, the multiple data processing unit 20 </ b> B processes a plurality of reception signals obtained by the multiple radar signal acquisition unit 10 </ b> B and inputs the processing result to the target detection processing unit 20.
Here, a specific example of target signal extraction will be described using a case where a ground stationary target is observed by a radar apparatus 100B mounted on a moving platform.

FIG. 13 is an explanatory diagram schematically showing the relationship between the radar apparatus 100B and the target T according to the third embodiment of the present invention. Components similar to those described above (see FIG. 15) are denoted by the same reference numerals. Detailed description is omitted.
In FIG. 13, the resolution cell 100a is related to the azimuth resolution of the radar apparatus 100B.

  As shown in FIG. 13, when observing a far target T with the radar apparatus 100B, the width of the resolution cell 100a on the ground surface is substantially widened due to the influence of the size limitation of the transmission / reception antenna 13, and the azimuth. The resolution becomes smaller.

  In addition, since the intensity of the reflected signal from the distribution target of the clutter C (such as the ground) is determined by the irradiation area of the beam, even if the resolution in the range direction is improved by applying pulse compression processing or the like, the azimuth direction When the resolution of is not sufficient, the reflection intensity from the clutter C shows a large value.

  On the other hand, the reflection signal from the distributed target as shown in FIG. 13 is observed as a superposition of the scattered waves from the scattering points included in the resolution cell 100a. The state of matching (speckle pattern: Speckle Pattern) changes.

It is known that the correlations ρ _sp and ρ _rot of signals between observation positions when the distribution target is observed at different observation positions are expressed by the following expressions (10) and (11).

  The above formula is described in public literature (for example, Howard A. Zebker, and John Villasenor, “Decoration in Interferometric Radar Echos”, IEEE TRANSACTION ON GEOSCIENCE AND NO. 92. REMOTE SENSE. Is well known.

In equations (10) and (11), θ is the radar incident angle, R _y is the range bin resolution, R _x is the azimuth resolution, and λ is the observation wavelength. Further, | dθ | is a change amount of the incident angle in two observations, and | dφ | is a change amount of the azimuth angle.

Expression (10) represents the correlation ρ _sp when the incident angles at the two observation positions are different, and Expression (11) represents the correlation ρ _rot when the azimuth angles are different.
According to equation (10), the decrease in correlation ρ _sp due to different incident angles depends on the range bin resolution R _y .
On the other hand, according to the equation (11), the decrease in the correlation ρ _rot due to the different azimuth angles depends on the azimuth resolution R _x .

In FIG. 13, the radar apparatus 100B mounted on the moving platform has a sufficient range bin resolution _Ry , but has a low azimuth resolution _Rx , and a plurality of radar apparatuses 100B moving in the azimuth direction (the width direction of the resolution cell 100a). It is assumed that the received signal is obtained by performing observations once.

In the case of a distribution target such as the ground surface, when the azimuth resolution _Rx of the radar apparatus 100B is low, it is expected that the correlation ρ _rot between the observation signals is greatly reduced due to a slight change in the observed azimuth angle.

On the other hand, regarding the target T, compared with the clutter C, it is expected that the amount of decrease in the correlation ρ _sp when observed at a different azimuth angle is small.
This is because, for the target T and the clutter C, as in the reflected signals Wt and Wc shown in FIG. 14, the beam pattern when the radio wave radiated from the radar device 100B is re-radiated from the target T and the clutter C. It ’s easy to understand.

  In FIG. 14, the reflected signal Wc indicates a virtual beam pattern when re-radiated from the clutter C, and the reflected signal Wt indicates a virtual beam pattern when re-radiated from the target T.

It is known that the beam pattern in the radar apparatus 100B becomes sharper as the aperture surface from which radio waves are emitted is larger.
Since the clutter C is directly irradiated with radio waves spread in the azimuth direction, the virtual aperture plane of the radio waves (reflected signal Wc) re-radiated from the clutter C is equivalent to the azimuth resolution.

On the other hand, the irradiation surface of the target T is determined by the size of the target T. In general, the target size is sufficiently smaller than the azimuth resolution (the width direction of the resolution cell 100a), so the virtual opening surface of the target T is smaller than the opening surface of the clutter C.
Therefore, as shown in FIG. 14, if each beam pattern of the radio wave (reflected signal Wc) re-radiated by the clutter C and the radio wave re-irradiated by the target T (reflected signal Wt) is compared, the reflected signal of the target T The reflected signal Wc of the clutter C is sharpened more than Wt.

In the sharpened beam pattern like the reflected signal Wc, when the azimuth angle changes, the observed signal changes greatly.
On the other hand, when the beam pattern is not sharpened like the reflected signal Wt, the signal change due to a slight azimuth angle change is small.

  In this way, a plurality of observation signals observed at different azimuth angles are processed using the property that the correlation of the reflection signal Wc of the clutter C is lower than the reflection signal Wt of the target T between signals observed at different azimuth angles. By doing so, it is possible to suppress the reflected signal Wc of the clutter C.

The clutter C suppression process includes, for example, a process of incoherently averaging signals observed at different angles, a method of calculating a correlation profile for each range bin n, and the like.
For example, the process of averaging incoherently is represented by the following formula (12).

In Expression (12), S _k (n) is a range profile observed at each azimuth angle, k is an observation number, and K is the number of observations.
By performing the above processing, it can be expected that the reception intensity of the clutter C is reduced, and the clutter C can be suppressed.

  In addition, if the radar apparatus 100B has a high memory capacity and high calculation performance, or if it is possible to acquire the observation position in each observation with high accuracy by GPS or the like, the observation at different azimuth angles is sufficiently performed. be able to.

For example, by applying synthetic aperture processing and DBS (Doppler Beam Sharpening), the Doppler frequency due to radar movement can be subdivided with a filter and divided into narrower beams than the actual beam to obtain high resolution, and also in the azimuth direction Data generation with high resolution becomes possible.
Synthetic aperture processing is described in publicly known literature (for example, “Kashio Ouchi“ Basics of Synthetic Aperture Radar for Remote Sensing ”) and is well known.

  As described above, the radar apparatus according to Embodiment 3 (FIGS. 11 and 12) of the present invention performs a plurality of times of radio wave transmission / reception and receives a plurality of observation signals, and a plurality of radar signal acquisition units 10B. Based on the processing results from the multiple data processing unit 20B that combines a plurality of observation signals and the multiple data processing unit 20B, an average value in each range bin is calculated by moving average processing using a window of a target size to be extracted. The moving average processing unit 40, the average value of each range bin calculated by the moving average processing unit 40 are compared, and a target signal extraction processing unit 50 that extracts a region where the target signal is located, and a plurality of targets from the target signal extraction processing unit 50 And a power range profile selection unit 50B for selecting a final output result from the output results of the power range profile.

  The multiple radar signal acquisition unit 10B includes an observation position acquisition unit that accurately measures each observation position in multiple observations performed at different angles, and the multiple data processing unit 20B acquires multiple observation signals and observation positions. A high-resolution processing unit that improves the resolution of a plurality of observation signals based on the measurement results of the unit.

  Furthermore, the radar apparatus according to Embodiment 3 of the present invention includes a target detection processing unit 20 that detects a target signal based on a processing result from the multiple data processing unit 20B, and a target signal detected by the target detection processing unit 20. A search range setting processing unit 30 that cuts out the periphery of the target position and sets a search range of the target signal, and the moving average processing unit 40 is based on the search range from the search range setting processing unit 30 in each range bin. The average value is calculated.

  As described above, by extracting the target signal using a plurality of observation signals, particularly in the case where the resolution is low, the difference in the amount of decrease in the correlation between the target T and the clutter C due to the difference in the observation position is obtained. Since the used clutter can be suppressed, the accuracy of target signal extraction can be improved as compared with the first embodiment.

  DESCRIPTION OF SYMBOLS 10 Radar signal acquisition part, 10A Multi-polarization observation signal acquisition part, 10B Multiple radar signal acquisition part, 11 Transmitter, 12 Transmission / reception switch, 13 Transmission / reception antenna, 13a First polarization transmission / reception antenna, 13b Second polarization transmission / reception antenna , 14 Receiver, 15 Received signal storage unit, 15A Received polarization signal storage unit, 15B Multiple received signal storage unit, 16 Polarization switch, 20 Target detection processing unit, 20A Polarized signal processing unit, 20B Multiple data processing unit , 30 Search range setting processing unit, 40 Moving average processing unit, 50 Target signal extraction processing unit, 50A, 50B Power range profile selection unit, 60 Output storage unit, 100, 100B Radar device, 100a Resolution cell, C clutter, T target , Wc reflected signal from clutter, Wt reflected signal from target, Z search range, Z1 first average Calculation position, Z2 second average calculation position, Z3 third average calculation position, Zc1, Zc2 background signal range, Zo target signal, Zo1, Zo2 target signal extraction range.

Claims (7)

A radar signal acquisition unit that transmits and receives radio waves to acquire observation signals;
Based on the observation signal, a moving average processing unit that calculates an average value in each range bin by a moving average process using a target size window to be extracted;
A target signal extraction processing unit that compares the average value of each range bin calculated by the moving average processing unit and extracts a region where the target signal is located;
A radar apparatus comprising: an output storage unit that stores an output result from the target signal extraction processing unit. A target detection processing unit for detecting a target signal based on the observation signal from the radar signal acquisition unit;
A search range setting processing unit for cutting out the periphery of the target position from the target signal detected by the target detection processing unit and setting a search range of the target signal;
The radar apparatus according to claim 1, wherein the moving average processing unit calculates an average value in each range bin based on a search range from the search range setting processing unit. A multi-polarization observation signal acquisition unit that performs transmission and reception for each of multiple polarization channels and generates a multi-polarization range profile;
A polarization signal processing unit that performs polarization signal processing on the multi-polarization range profile observed in the multi-polarization observation signal acquisition unit;
Based on the processing result from the polarization signal processing unit, a moving average processing unit that calculates an average value in each range bin by a moving average process using a target size window to be extracted;
A target signal extraction processing unit that compares the average value of each range bin calculated by the moving average processing unit and extracts a region where the target signal is located;
A radar apparatus comprising: a power range profile selection unit that selects a final output result from output results of a plurality of power range profiles from the target signal cutout processing unit. A target detection processing unit for detecting a target signal based on a processing result from the polarization signal processing unit;
A search range setting processing unit for cutting out the periphery of the target position from the target signal detected by the target detection processing unit and setting a search range of the target signal;
The radar apparatus according to claim 3, wherein the moving average processing unit calculates an average value in each range bin based on a search range from the search range setting processing unit. A plurality of radar signal acquisition units that perform transmission and reception of a plurality of radio waves and receive a plurality of observation signals;
A plurality of data processing units for combining the plurality of observation signals;
Based on the processing results from the plurality of data processing units, a moving average processing unit that calculates an average value in each range bin by moving average processing using a target size window to be extracted;
A target signal extraction processing unit that compares the average value of each range bin calculated by the moving average processing unit and extracts a region where the target signal is located;
A radar apparatus comprising: a power range profile selection unit that selects a final output result from output results of a plurality of power range profiles from the target signal cutout processing unit. The multiple radar signal acquisition unit includes an observation position acquisition unit that accurately measures each observation position in multiple observations performed at different angles,
The said multiple data processing part contains the high-resolution process part which improves the resolution | decomposability of these several observation signal from the observation signal of several times and the measurement result of the said observation position acquisition part. Radar equipment. A target detection processing unit for detecting a target signal based on processing results from the plurality of data processing units;
A search range setting processing unit for cutting out the periphery of the target position from the target signal detected by the target detection processing unit and setting a search range of the target signal;
The radar apparatus according to claim 5, wherein the moving average processing unit calculates an average value in each range bin based on a search range from the search range setting processing unit.

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