JP3389127B2 - Radar signal processing apparatus and signal processing method for radar signal processing apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a method of suppressing a transient response of a filter to remove an unnecessary signal by the filter, suppresses deterioration of performance, and improves a detection probability of a target. And a signal processing method of a radar signal processing device.

[0002]

2. Description of the Related Art Conventionally, in a signal processing device in a radar device, a filter is used from various received signals to suppress echoes reflected from a fixed object having a speed of 0, such as a building or the ground surface, to prevent rainfall. There is a method of extracting a reception signal of a moving target such as a cloud, an aircraft or the like. The above-mentioned filter is an MTI that separates a signal containing an unnecessary signal having no velocity from a target signal having a Doppler velocity.
(Moving Target Indicator:
There is a moving target indicating device) filter. This MTI filter is a high-pass filter composed of digital filters.

FIG. 4 is a circuit diagram showing a digital filter circuit in a conventional radar signal processing device. In the figure, 120 is a delay circuit for delaying an input value for a predetermined time and outputting them in order, 105, 106, 107 and 108 are amplifier circuits having amplification factors of a1, b1, c1 and d1, 109, 110, 111 and 112 are a
An amplifier circuit having an amplification factor of 2, b2, c2, d2, 10
1, 102, 103, 104 are state variables, 114, 11
5, 117 and 118 are variables. In addition, a complex number sample including a real number and an imaginary number is input to the input.

Next, the operation will be described. FIG. 5 is an explanatory diagram for explaining the operation of the digital filter circuit in the conventional radar signal processing device. The value of the variable 114 before the predetermined time is output to the state variable 101, and the state variable 102
The value of the state variable 101 before the predetermined time is output to. Therefore, as shown in FIG. 5, the variable 114 and the state variable 101,
The numerical value of 102 changes. In addition, the state variable 103 includes
The value of the variable 115 before the predetermined time is output, and the state variable 10
In 4, the value of the state variable 103 before a predetermined time is output.
The variable 114 includes the variable 117, the amplification circuit 105,
The difference between the outputs of 106 is output, and the variable 115 is set to the variable 1
The difference between the outputs of 18 and the amplifier circuits 109 and 110 is output. Next, for the variable 118, the variable 114 and the amplifier circuit 10 are set.
The sum of the outputs of 7 and 108 is output, and the output 116 outputs the sum of the variable 115, the amplification circuit 111, and the amplification circuit 112. The frequency characteristics of the digital filter can be variously set by setting the amplification factors of the amplifier circuits 105 to 113.

FIG. 6 is an explanatory diagram showing the amplitude of an input / output signal when a received signal of a digital filter circuit in a conventional radar signal processing device is continuously input, and schematically shows an echo from a fixed target. It is a thing. Doppler radar uses multiple samples to determine Doppler velocity. To calculate the Doppler speed, N samples are input to the digital filter from the received signal and N samples are output. Although the echo from the fixed target has a velocity of 0, it is received as a strong echo with almost no change in phase and amplitude because it is affected by the beam pattern of the antenna. Regarding the state in which the filtering of the received signal is started, there are cases where the received signal is continuously input before the filtering of the received signal of N samples and cases where the received signal immediately before the input N samples is unknown.

FIG. 7 is an explanatory diagram showing the amplitudes of input / output signals when the received signal N samples of the digital filter circuit in the conventional radar signal processing device are input, and FIG. 8 shows the received sample before the received sample in the conventional radar signal processing device. It is explanatory drawing which shows the amplitude of the input / output signal of a digital filter when the sample of 0 is extrapolated. In the conventional radar clutter suppression apparatus, the received signal N samples are input to the filter after the internal state variable of the filter is set to zero. Input the received signal in the state where the internal state variable is 0, and input the received signal N samples after all the internal state variables become 0 in the steady state where the input value is 0 as shown in FIG. Are equivalent.

Then, when the received signal is input after the input of the value 0 continues and becomes a steady state, the received signal is input from the value 0 as shown in FIG. 8 at time T = 0 when the received signal is input. Due to a large change when the output signal starts to be generated, a transient response occurs in which the output signal undulates with the same width as the change of the input signal. This is the IIR (Infinite Impulse) shown in FIG.
Response) A characteristic of a filter that has a feedback circuit such as a filter, and can be seen when the input changes greatly in an instant.

When the filter has a transient response, the spectrum of the output signal is distorted, and the performance of extracting the speed / speed range (= speed estimation accuracy) of the target also deteriorates. on the other hand,
If not only the received signal N samples are processed but the received signals continuously obtained before that are input to the filter,
It is ideal because no transient response occurs. However, there are cases where the sample before the N samples of the received signal cannot be obtained due to the conditions of the specifications and design of the radar. Even under these conditions, in order to suppress the transient response, it is preferable to extrapolate the pseudo signal before the received signal of N samples. This can reduce spectral distortion due to transient response.

Conventionally, there has been a method of setting a state variable inside the filter by inputting a DC input that repeats the first sample of the received signal as the external signal. With this method, the input cannot change significantly at the start of filtering the received signal, so that no transient response occurs.

[0010]

Since the conventional radar signal processing device and the signal processing method of the radar signal processing device are configured as described above, the method of using the DC input as the pseudo signal also includes the components of the received signal. Similar to the pseudo signal, this is an effective method in the case where the DC component, that is, the phase change at a speed of 0 is extremely small. However, the phase of the ground surface echo to be suppressed may change and have a velocity component of only about 1 m / s, and such a signal is input after the pseudo signal of DC and has the same effect as the transient response. However, there was a problem that the performance of the filter was deteriorated.

The present invention has been made in order to solve the above-mentioned problems. For a received signal limited to N samples due to the conditions of radar specifications, design and operation, it is generated from the received signal before that. Extrapolating the simulated signal
Or, by using the method of setting the state variable of the digital filter in the steady state assuming a DC input before this pseudo signal setting, suppressing the transient response of the filter and removing the unnecessary signal by the filter, An object of the present invention is to obtain a radar signal processing device and a signal processing method of the radar signal processing device, which can suppress deterioration of performance and improve the detection probability of a target.

[0012]

A radar signal processing apparatus according to the present invention receives a received signal and then receives the received signal.
Generate a pseudo signal that repeats part or all of the
The signal is added before the received signal to the digital filter.
It is designed to be output.

The radar signal processing device according to the present invention is
When the received signal is input , the pseudo received signal adding means
Before the received signal with signal is output, digital fill
State variables that represent the steady state when a pseudo signal is input to
The initial value of is calculated and the initial value of the state variable is
This is set to the filter.

In the signal processing method of the radar signal processing device according to the present invention, when a received signal is input , the received signal
Generate a pseudo signal that repeats some or all of the
Signal that is output by adding the signal before the received signal
It has an additional step.

A signal processing method for a radar signal processing device according to the present invention is such that when a received signal is input , a pseudo received signal is added.
Before the reception signal with the pseudo signal is output from the adding step
When inputting a pseudo signal in the filtering step
Calculate the initial value of the state variable that represents the steady state of
State in which the initial value of the variable is set in the filtering step
A variable initial value calculation step is provided.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. 1 is a block diagram showing a clutter suppressing device using a pseudo reception signal in a radar signal processing device according to a first embodiment of the present invention. In the clutter suppressing apparatus of FIG. 1, the pseudo reception signal adding device 160 which is a pseudo reception signal adding means is provided.
Then, a pseudo signal is added to the front of the received signal and is input to the digital filter 161. As a method of giving the pseudo signal, the pseudo signal is A (N) in order to make the phase change of the signal continuous at the points where the pseudo signal and the received signal S (n) are continuous.
expj (-φ (N) + φ (1)) to A (2) expj
(-Φ (2) + φ (1)), and the received signal is A (1) e
xpj (0), A (2) expj (φ (2) −φ
(1)) to A (N) expj (φ (N) −φ (1)) can be considered. Where A (n) and φ (n)
Are the amplitude and phase components of S (n), respectively, and j means an imaginary number (j ² = −1).

By this method, at the start of input (T = 0)
Of the received signal S (0) = A (0) exp (0) is symmetrical in amplitude and phase. That is, when the input of the received signal is started, the phase change does not change suddenly, and the transient response due to the phase change can be suppressed. further,
As a method of giving a pseudo signal which is an improvement of this method, A
There is also a method of adding a DC signal in which (N) expj (−φ (N) + φ (1)) continues. Accordingly, it is possible to suppress the influence of the transient response that occurs when the input of the pseudo signal is started.

Next, the operation will be described. FIG. 2 is a block diagram showing a clutter suppressing device for provisionally mounting a pseudo received signal and setting an initial value of a state variable in the radar signal processing device according to the first embodiment of the present invention. The way of giving this pseudo signal is as follows. First, in FIG. 2, after receiving the received signal, the initial value of the state variable in the steady state in which the direct current pseudo signal is input by the state variable initial value calculator 170 is obtained and the state variable of the digital filter is set. To do. The method of setting the state variable in this steady state will be described later.

Next, the pseudo signal adding device is A (N) exp.
j (-φ (N) + φ (1)) to A (2) expj (-φ
(2) + φ (1)) pseudo signal is output, and the pseudo signal and the received signal are sequentially input to the digital filter 161. The state variable of the digital filter in the steady state with DC input is calculated as follows. In the case where a digital filter is constructed by the circuit of FIG.
A method of setting the initial values of 1 to 104 will be described. As a method of suppressing the transient response, a steady state in which a direct current having the same value as the first sample of the N samples of the received signal is input is created and the initial values of the state variables 101 to 104 are set. In the steady state, the output of the filter has a constant DC value, and both the output and the variable inside the filter have a constant value. These variables are uniquely determined from the filter settings and input values.

FIG. 3 is a circuit diagram showing a part of a digital filter circuit in the radar signal processing device according to the first embodiment of the present invention. Variable 1 inside the digital filter
30 (I _n ), 131 (x _n ), 132 (y _n ), 13
7 (w _n ), 138 (O _n ) and the amplifier 133
(A _n ), 134 (b _n ), 135 (c _n ), 136
The relationship of Expression (1) is established from (d _n ).

[0021] _{x n = w n-1 y} n = x n-1 w n = I n -Ax n -By n O n = w n + Cx n + Dy n ( Equation 1)

Then, in the steady state, the relationship between the equations (2) and (3) is established.

I _n = I _n-1 (Equation 2) x _n = x _n-1 = y _n = y _n-1 = w _n = w _n-1 (Equation 3)

From equations (1) to (3), equation (4) is obtained.
And equation (5) is obtained.

X _n = y _n = w _n = I _n / (1 + a _n + b _n ) (Equation 4) O _n = (1 + c _n + d _n ) I _n / (1 + a _n + b _n ) (Equation 5)

From the equation (4), the state variables 131 and 132 in the steady state shown in FIG. 3 are obtained from the amplification factors of the filter amplifiers 133 to 136 and the DC input signal. Equations (4) and (5) are applied to the circuit of FIG.

First, the signal is input to the amplifier circuit 113,
The variable 117 is obtained by the equation (6). I ₁ = h (0) I _x (Equation 6)

The signal from the variable 117 is transmitted to the first-stage digital filter, and the first-stage state variables 101 and 102 are transmitted.
And the variable 118 are obtained from the equations (7) and (8). Similarly, the first-stage state variables 103 and 104 and the output 116 are
It can be obtained from equation (9).

X ₁ = y ₁ = h (0) I _x / (1 + a ₁ + b ₁ ) (Expression 7) O ₁ = (1 + c ₁ + d ₁ ) h (0) I _x / (1 + a ₁ + b ₁ ) (Expression 8) x ₂ = y ₂ = I ₂ / (1 + a ₂ + b ₂ ) = O ₁ / (1 + a ₂ + b ₂ ) = (1 + c ₁ + d ₁ ) h (0) I _x / {(1 + c ₁ + d ₁ ) (1 + a ₂ + b ₂ )} (Formula 9)

The initial value of the steady-state state variable of the DC input thus obtained is set to 101 to 104, and the received signal N
The sample is input and the output is obtained from 116. The output of the digital filter of the signal cutout device 162 is cut out by the signal cutout device 161 of the last N samples to be the output of the clutter suppression device.

As described above, according to the first embodiment, regarding the MTI filter, the initial value of the state variable inside the MTI filter is set by extrapolating the signal before inputting N samples of the received signal. Since the transient response that occurs when the state variable is set to 0 can be suppressed, distortion of the spectrum of the output signal does not occur, and the target detection probability can be improved.

[0032]

As described above, according to the present invention, when a received signal is input , part or all of the received signal is repeated.
Generate a pseudo signal to be returned, and
Since it is configured such that it is added to the front and is output to the digital filter, there is an effect that performance degradation can be suppressed and the target detection probability can be improved.

According to the present invention, the received signal is input .
And the received signal with the pseudo signal from the pseudo received signal adding means.
Before the output of the pseudo signal in the digital filter
Calculate the initial value of the state variable that represents the steady state at the input of
Set the initial value of the state variable to the digital filter
Since it is configured like this, it occurs when starting the input of the pseudo signal.
This has the effect of suppressing the effect of transient response due to

According to the present invention, the received signal is input .
And a pseudo signal that repeats part or all of the received signal
Generate it, add the pseudo signal in front of the received signal, and output.
Since it is configured to provide a pseudo-received signal adding step of force, while suppressing deterioration of performance, such an effect can be enhanced probability of detecting a target.

According to the present invention, the received signal is input .
And the reception with the pseudo signal from the pseudo reception signal addition step
Before the signal is output, go through the filtering step.
Initial value of the state variable that represents the steady state when a pseudo signal is input
Is calculated and the initial value of the state variable is filtered.
Set up a step for calculating the initial value of the state variable
Since it is configured like this, it occurs when starting the input of the pseudo signal.
This has the effect of suppressing the effect of transient response due to

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a clutter suppressing device using a pseudo reception signal in a radar signal processing device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a clutter suppressing device that temporarily sets a pseudo received signal and sets an initial value of a state variable in the radar signal processing device according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a part of a digital filter circuit in the radar signal processing device according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a digital filter circuit in a conventional radar signal processing device.

FIG. 5 is an explanatory diagram illustrating an operation of a digital filter circuit in a conventional radar signal processing device.

FIG. 6 is an explanatory diagram showing amplitudes of input / output signals when a received signal of a digital filter circuit in a conventional radar signal processing device is continuously input.

FIG. 7 is an explanatory diagram showing amplitudes of input / output signals when N samples of received signals of a digital filter circuit in a conventional radar signal processing device are input.

FIG. 8 is an explanatory diagram showing the amplitude of the input / output signal of the digital filter when the sample of 0 is extrapolated before the received sample in the conventional radar signal processing device.

[Explanation of symbols]

101-104 state variables, 105-113 amplification circuits, 114, 115, 117, 118 variables, 120
Delay circuit, 131 state variable, 132 state variable, 13
3 to 136 amplifier circuits, 137 variables, 160 pseudo reception signal addition device (pseudo reception signal addition means), 161 digital filter, 162 signal cutout device (signal cutout means), 170 state variable initial value calculator.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-103416 (JP, A) JP-A-5-203733 (JP, A) JP-A-10-197627 (JP, A) JP-A-9- 138273 (JP, A) JP 9-257911 (JP, A) Actual development 5-59374 (JP, U) Actual development 5-84885 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S ^7/ 00-7/42 G01S 13/00-13/95 H03H 17/00 601

Claims (4)

(57) [Claims] 1. When a received signal is input , the received signal
Generate a pseudo signal that repeats some or all of the
And the pseudo reception signal adding means for outputting the added before of the received signal to issue, output from the pseudo reception signal adding means
When a received signal with a pseudo signal is input,
A digital filter for outputting to remove Doppler frequency component near Luo speed 0, the output from the digital filter
A radar signal processing device comprising: a signal cutting-out unit that cuts out the same number of points of the received signal from the input when the received received signal is input . 2. A pseudo reception signal is added when a reception signal is input .
Before the reception signal with the pseudo signal is output from the adding means,
Steady state at input of pseudo signal in digital filter
The initial value of the state variable
Initial value of the state variable that sets the value in the above digital filter
The radar signal processing device according to claim 1, further comprising a calculator . 3. When a received signal is input , the received signal
Generate a pseudo signal that repeats some or all of the
Pseudo received signal to output prepends the received signal No.
Output from the adding step and the above pseudo received signal adding step
If you input the received signal with the pseudo signal
Remove the Doppler frequency component near the velocity 0 from the signal
And the filtering step
Input the received signal output from the
Shin outputting cut the same number of received signal from the input
A signal processing method for a radar signal processing device, comprising: 4. A pseudo reception signal is added when a reception signal is input .
Before the reception signal with the pseudo signal is output from the adding step
When inputting a pseudo signal in the filtering step
Calculate the initial value of the state variable that represents the steady state of
Set the initial value of the variable in the above filtering step
It is characterized in that a state variable initial value calculation step is provided.
The signal processing method of the radar signal processing device according to claim 3 .