JPH03218486A - Pulse doppler radar equipment - Google Patents

Abstract

PURPOSE:To improve an S/N by providing a storing means for the output of a receiving means, range bin calculating means to calculate the number of a range, where a target exists, for each pulse hit, phase compensation item calculating means and sum of products calculating means. CONSTITUTION:A storing means 13 stores the digital video signal of a receiving means 12 in the shape of a two-dimensional grating based on a range bin number and a pulse hit number into a signal processing means 108. A range bin calculating means 107 calculates the number of a range bin, where the target exists, for each pulse hit. A phase compensation item calculating means 106 calculates the phase compensation item of the digital video signal with the range bin umber calculated by the means 107 by using a prescribed formula. A sum of products calculating means 105 is composed of a complex multiplier 103 and a complex adder 104. Thus, since the target under observation follows up the range bin number and a received signal is extracted, regardless of target radial velocity, the total number of pulse hits and an integration area, where the target signal exists, can be samely obtained and an integration output can be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] This invention relates to a pulse Doppler radar device that uses coherent integration to improve the signal-to-noise power ratio (hereinafter referred to as SNR).

[Prior art] As a conventional pulse Doppler radar device of this type,
For example, literature, G. V. Morris: “Airb.
ornePulsed Doppler Radar”
, Artech l{ouse, Inc. (198
There is one shown in 81. FIG. 8 is a block diagram of a conventional pulse Doppler radar device.

(11 is an antenna, (2) is a transmitting means, (3) is a transmitting/receiving switch, (12) is a receiving means, (17) is a signal processing means, and (18) is a display.

Next, an outline of the operation will be explained. The transmission pulse generated by the transmitting means (2) is radiated to the target as a radio wave via the transmitter/receiver switch (3) and the antenna (11).The radio wave reflected by the target is received by the antenna (1), and the transmitter/receiver switcher (3), the signal is input to the mixer (5) in the receiving means {l2}, multiplied by the output of the local oscillator {4}, and converted into an intermediate frequency signal.

The output of the mixer {5} is an IF (intermediate frequency) amplifier (6)
After being amplified, the signal is divided into two parts, each of which is input to a phase detector (7). In the phase detector {7), the product of the output signal of the coherent oscillator {8} and the output signal of the coherent oscillator (8)
) is multiplied by a signal obtained by delaying the phase of the output signal by 900 degrees using a 90° phase shifter {9}, and the respective phases are detected. The output of each phase detector is held by a sample holder (10) as the real part (1) and imaginary part (IQ) of the received complex video signal, and then converted into a digital complex video signal by an A/D converter {11}. converted.

The digital complex video signal is processed by signal processing means 1l7)
The pulse hit number n and the range pin number m are stored in the storage means (13) in a two-dimensional grid pattern. A digital complex video signal with the same range pin number corresponding to the coherent integral number N is extracted from the storage means (l3), and fast Fourier transform (hereinafter appropriately referred to as FFT) means {l4}
Coherent integration is performed by performing fast Fourier transform fi.

Based on the output of the FFT means (l4), the amplitude detector (
The amplitude value is calculated by the threshold detector (
16). The threshold detector (l6) determines that the output signal of the amplitude detector (l5) is a target when it exceeds a predetermined threshold level, and displays the detection signal on the display (l8).
send to The indicator (18) receives the detection signal and displays the target.

Now, assuming that the repetition period of the transmission pulse is Δt and the transmission wavelength is a circle, N filters whose center frequency fn can be expressed by the following equation are formed by FFT, and the bandwidth of each Doppler filter is . It is given by approximately 1/NΔt.

fn=n/N Δtv [n=-N/2. ++ I
B, -, (N/2) -11 The FFT calculation assumes N types of the following equation as the target radial velocity Vn, and performs integration by compensating for the temporal change in the phase of the received signal caused by this, that is, Equivalent to coherent integration.

■n=λfn/2, [n=-N/2, ・=. 0.
−． (N/2)-11 [Problem to be solved by the invention] This type of conventional pulse Doppler radar device is configured as described above, and the target being observed exists within the same range pin range. In some cases, coherent integration can improve the SNR by a factor of N. but,
When the radial velocity V of the target is large, the target under observation does not always exist within the same range pin range, which creates a restriction on the number N of coherent integrations. For example, transmission pulse repetition period Δt = Inks e range width ΔR =
Radial speed V = 4 Mach (150 m) with 15 m radar.
When observing a target of
There was a problem that the NR improvement effect could not be obtained.

N≦ΔR/VΔt (1) This invention was made to solve the above problems,
The purpose of the present invention is to obtain a pulse Doppler radar device that can obtain an SNR improvement effect by coherent integration even if a target during observation moves within a range.

[Means for Solving the Problems] In order to achieve the above object, the pulse Doppler radar device of the present invention has its signal processing means input two digital video signals output from the receiving means based on the range pin number and the pulse hit number. a storage means for storing data in a dimensional grid; a range pin calculation means for calculating the range pin number where a target exists for each pulse hit; a phase compensation term calculation means for the digital video signal of the calculated range pin number; and a product-sum calculation means for calculating the sum of products and the phase compensation term thereof.

The signal processing means also includes a first storage means for storing the digital video signal output from the receiving means in a two-dimensional grid of range pin numbers and pulse hit numbers, and a first storage means for storing the digital video signal in a two-dimensional grid of range pin numbers and pulse hit numbers. a second storage means for storing the frequency spectrum of the output of the fast Fourier transform means; and a range pin calculation means for calculating the range pin number where the target exists for each specific number of pulse hits;
A phase compensation term calculation means for a frequency spectrum selected from the second storage means based on the range pin number calculated above, and a product-sum calculation means for performing a product-sum calculation of the frequency spectrum and its phase compensation term. It is something.

[Operation] In a pulse Doppler radar device equipped with a signal processing means configured as described above, the signal processing means stores the digital video signal output from the receiving means in a two-dimensional grid pattern based on the range pin number and the pulse hit number. storage means for calculating the range pin number where the target exists for each pulse hit; means for calculating the phase compensation term of the digital video signal of the calculated range pin number; and the digital video signal and its phase compensation. Even if the target under observation moves the range pin, the received signal is extracted by tracking the range pin number where the target exists for each pulse hit. Regardless of the target radial speed, the total number of pulse hits N can be kept the same as the integral region where the target signal exists, and the integral output can be increased.

The signal processing means also includes a first storage means for storing the received output digital video signal in a two-dimensional grid of range pin numbers and pulse hit numbers, and a first storage means for storing the received output digital video signal in a two-dimensional grid of range pin numbers and pulse hit numbers; means for dividing and performing fast Fourier transform on each; second storage means for storing the frequency spectrum of the output of the fast Fourier transform means; range pin calculation means for calculating the range pin number where the target exists for each specific number of pulse hits; By comprising a phase compensation term calculation means for a frequency spectrum selected from the second storage means based on the calculated range pin number, and a product-sum calculation means for performing a product-sum calculation of the frequency spectrum and its phase compensation term. , the target being observed. Even if the range pin is moved, the range pin number where the target exists for each specific number of pulse hits is tracked and the corresponding F
Since the FT means output is selected, the total number of pulse hits N and the integral region in which the target signal exists can be made almost the same, regardless of the target radial speed, and the integral output can be made thicker.

[Embodiments of the invention] Claim 1 and Claim 2. An example of each will be described with reference to the drawings.

Figure 1 shows claim 1. FIG. 2 is a configuration block diagram showing one embodiment of the present invention.

The antenna (l), transmitting means (2), transmitting/receiving switch {3), receiving means (12), which are the same components as the conventional example shown in FIG.
Since the display device (18) has already been explained, its explanation will be omitted here.

In the figure, (13) is a storage means for storing the digital complex video signal output from the receiving means in a two-dimensional grid with pulse hit number n and range pin number m, and (103) is the output of storage means (l3) and its phase compensation. (104) is a complex adder that adds the outputs of the complex multiplier +103), (105) is the complex multiplier (
103) and a multi-accumulate adder 11041, (10G) is the above-mentioned phase compensation term calculation means,
(107) is a range pin calculation means that calculates the range pin number where the target exists for each pulse hit according to the radial speed of the target; (15) is an amplitude detector that detects the amplitude of the output of the product-sum calculation means (105); (l6) is a threshold detector that determines whether the output level of the amplitude detector (l5) exceeds a predetermined threshold level;
81 is a storage means (l3) and a product-sum calculation means (105)
, a phase compensation term calculation means (1061), a range pin calculation means (1071), an amplitude detector (15), and a threshold detector (16).

Next, the operation will be explained. FIG. 2 is a flowchart illustrating the operation of the signal processing means of FIG. 1.

In step (2051), a number i (hereinafter referred to as counter i) corresponding to the target radial speed is set to 0.

Here, the maximum value of i, that is, the number of target radial speed types, is assumed to be ■. In step (206), the counter i is counted up.

In step (2071), the range pin number h (n) where the target exists is calculated for each pulse hit number according to the target radial speed Vi.

In step (2081), the phase compensation term of the digital multiple video signals of each range pin number h(nl obtained in step (2071) is calculated.

In step (209), the digital complex video signal of the range pin number h(nl) where the target exists, and the digital complex video signal of the range pin number h(nl) where the target exists, and
Perform a product-sum operation with each phase compensation term calculated in 08),
Find the coherent integral output.

In step (2101), the amplitude value of the coherent integral output obtained in step (209) is determined, and it is determined whether the value exceeds a predetermined threshold level. If it exceeds, it is regarded as a target and the information is sent to the display (l8). send.

In step (211), the number of target radial speed types I
It is determined whether all the processes have been performed, and if the process has not been completed yet, the process returns to step (206) and the process is repeated.

Next, the processing contents of the above steps will be explained.

In step (207), the range pin number where the target exists is calculated using the second equation.

h(n)-[(Ro-nΔtVi)/ΔRl
(2) Here, Ro: Target distance Δt at 0; Transmission pulse repetition period 8R; Range pin width vi; Target radial speed 1l; Gauss word number 1 n; Pulse hit number (n=1,...,Nl The process of step (207) is executed by the range pin calculation means (107) shown in FIG.

In step (208), each CL (n) = exp[-j4x / λ((n Δt+h(n
) t ) Vi-Roll (3) Here, τ is the transmission pulse width. The process of step (208) is executed by the phase compensation term calculation means (1061) shown in FIG.

In step (2091), the digital complex video signal of the range pin number h (n) where the target exists, calculated in step (20?), is weighted for sidelobe suppression (not shown), and then in step (2081) Perform a product-sum operation with the calculated phase compensation term Ci (n),
Find the coherent integral output Si. Si can be expressed by the fourth equation.

Here, U(n-h(n)); digital complex video signal wn of pulse hit number n, range pin number hIn); weight. The process of step (209) is executed by the product-sum calculation means (105) shown in FIG.

With the above configuration, the third rule is that in coherent integration, the integration region where the target exists is larger than before.
This will be explained with reference to FIGS.

FIG. 9 is a diagram showing an example of a target signal existence region and an integral region on a memory map of a storage means in a conventional signal processing means. When the target radial speed is high. Assume that the target signal occupies the area marked O. However, in conventional coherent integration, the output is not thick. Figure (30
11 is an integral region where the target signal exists, and +3021 is an integral region where no target signal exists. In such a case, total pulse hit FIG. 3 is a diagram showing an example of the target signal existence region and integral region on the memory map of the storage means of FIG. 1. Assume that the target is moving at high speed and the target signal occupies the area marked with a circle, as in the case of FIG. 9 above. In this embodiment, since the coherent integration is performed on the shaded area, the integration region where the target signal exists is 2 orders < .
Integral output can be increased. The total number of pulse hits N and the integral region in which the target signal exists are the same.

Next, FIG. 4 shows claim 2. FIG. 2 is a configuration block diagram showing one embodiment of the present invention.

Since the same components as those of the conventional example shown in FIG. 8 have already been explained, they will not be described here.

In the figure, (131) is a first storage means which stores the digital complex video signal of the receiving means output {12) in a two-dimensional grid of pulse hit number n and range pin number m;
(SOt) is a means for dividing the digital complex video signal stored in the upper first storage means into units of a specific number of pulse hits with respect to the range pin number, and fast Fourier transforms each independently, and (502) is the FFT means mentioned above. (501) is a second storage means for storing the output of the second storage means (501), 1503) is a double-accumulate multiplier that multiplies the output selected from the second storage means (502) by its phase compensation term, and (504) is a double-accumulate multiplier ( 503
), (SOS) is a product-sum operation means composed of a double-accumulate multiplier (503) and a double-accumulate adder (504), and (506) is a phase unit for calculating the above phase compensation term. Compensation term calculation means (507) is range pin calculation means for calculating the range pin number where the target exists for each specific number of pulse hits according to the target speed Vi, (15) is the amplitude of the output of the product-sum calculation means (505). (16) is a threshold detector that determines whether the output level of the amplitude detector (l5) exceeds a certain level;
(508) is the lth storage means {l3} and the FFT means (
501), second storage means, and product-sum calculation means+5051
and. The signal processing means includes a phase compensation term calculation means (506), a range pin calculation means (507), an amplitude detector (l5), and a threshold detector (l6).

Next, the operation will be explained. FIG. 5 is a flowchart illustrating the operation of the signal processing means of FIG. 4.

Step (6011) sets a counter m indicating the range pin number to 0.

In step (602), the counter m is counted up.

In step (603), K for range pin number m is
Perform L-point FFT. FIG. 6 is a diagram illustrating partial section data on the memory map of the rainbow storage means shown in FIG. 4. FIG. The digital complex video signal is stored in the first storage means (l3) and subjected to FFT on the range input section).
Indicates when to do this. Unlike the conventional example, N-point FFT is not performed,
N points are divided into K L points, that is, partial section data each having a data length, and L point FFT is performed independently on each segment.

In step (6041), it is determined whether processing has been performed for all range pin numbers M, and if not, the process returns to step (602) and repeats the processing.

In step (6051), a number i (hereinafter referred to as counter i) corresponding to the target radial speed is set to 0.

Here, let I be the maximum value of i, that is, the number of types of target radial speeds.

In step (606), the counter i is counted up.

In step (607), the range pin number h (nl) where the target exists for each specific number of hit pulses is calculated according to the target radial speed Vi.

In step (6081), the second storage means storing the FFT means output obtained in step (603) is transferred to step (6081).
The phase compensation term of the FFT means output of the range pin number obtained in step 6071 is calculated.

In step (609), from the second storage means to step (609),
A product-sum operation is performed between the FFT output of the range pin number obtained in step 07) and its phase compensation term calculated in step (608). Obtain coherent integral output.

In step (610), the amplitude value of the coherent integral output obtained in step (609) is determined, and it is determined whether the value exceeds a predetermined threshold level. If it exceeds, it is regarded as a target and the information is displayed on the display (l8) send to

In step $611), the number of target radial speed types ■
Determine whether processing has been performed, and if not, proceed to step (
606) and repeat the process.

Next, the processing contents of the above steps will be explained.

First, in step (603), the receiving means (l2 of FIG. 4)
The output digital complex video signal is connected to the range pin number m,
After dividing the range pin number m of the first storage means stored in a two-dimensional grid of pulse hit numbers n into K partial interval data in units of specific pulse hit number L, and weighting each part for sidelobe suppression. (not shown)
, independently perform L-point FFT, and obtain the frequency spectrum using Equation 5. For example, a Taylor window is used as the weight.

Note that by taking the partial interval data (data length) at intervals of r smaller than the data length L, the data is uniformly distributed and the influence of aliasing, which is undesirable due to the characteristics of the filter, is suppressed.

k-th FFT means 1501 at range pin number m
) can be expressed by the following equation.

old α, k, +++) (5) Here, a; frequency spectrum number (FFT means (50
1) output number) (a=1,2,...,L) k; data string number (FFT means (number of 5011 (k=1.2,...κ) wL; weight U{β , k, +++l; k-th FFT means (5011 input to the k-th range pin → 4th digital complex video signal L of part t segment data input to the FFT means (5011 input data length);

The calculated frequency spectrum data is the second h (k) =
[(Ro-n ΔtVi) /ΔR] Here, target distance Δt when RO-time 1=0; pulse repetition period (6) n; specific pulse hit number n= (k-11 "+
t. /;l! , 1k=1, 2, ..., κ) []; Gaussian symbol. The process of step +6071 is executed by the range pin calculation means (507) in FIG.

Step (6081) from the second storage means to step (6081)
Phase compensation term Ci of FFT output (frequency spectrum) selected by range pin number h (k) obtained in 07)
is calculated using the seventh equation.

Ci (a, β, k) = ψ. -k・4)w ●exp(-j2πkβ/Kl (71 Here, a; FFT means (5011 output frequency spectrum number [-L/2, - (L/21 + 1,...,0
,..., (L/21-II arbitrary integer β; -K/2≦β<real number k of K/2. FFT means (501) (7) Number ψ .k; each F
This is the α-th frequency vector of the FT means.

ψα． k and φd can be expressed by the 8th and 9th equations, respectively.

ψ, ． b=exp(-j2 w ``k aru) (8)
φm =exp(-j2 ih(k)T:Vil
(9) Here, L: transmission pulse width.

The relationship between the variables α, β and the target radial speed Vi can be expressed by the 10th equation.

Vi=L (a/LΔt+(3/NΔt)
/2 (10) Here, E; transmission pulse wavelength N; total number of pulse hits. The above variables α and β can be determined using, for example, the ti equation, the first equation
Calculate by formula 2.

a=[2ViLΔt/λ] (
11) (β= ((2Vi/e)-α/(LΔtl)・N
Δt (121 here, []: Gauss symbol. The process of step (608) is executed by the phase compensation term calculation means (506) in FIG.

In step 16091, step (
6071 Select k(
k) After weighting the FFT output U (α, k, w) for sidelobe suppression (not shown), a product-sum operation is performed with the phase compensation term Ci calculated in step (608). , a coherent integral output Si is calculated. The coherent integral output Si can be expressed by the thirteenth equation.

(13) Here, Wk. It's weight. The process of step i609) is a diagram showing an example of the existence region and the integral region of the product-sum target signal in FIG. When the target radial speed is high, the target signal is O in the figure.
Assume that it occupies the area marked. In this embodiment, coherent integration is performed for the shaded area in units of a specific number of pulse hits, so if the integration region where the target LA signal exists is ancient times, it is possible to increase the integral output. In the figure, {8 old} is the integral region where the target signal exists, and (802) is the integral region where the target signal does not exist. The total number of pulse hits N and the integral region (801) where the target signal exists are almost the same. In this embodiment, N points are divided into K L points, that is, subinterval data of the data length, with respect to range pin numbers from a storage means that stores digital complex video data in a two-dimensional grid pattern, and each is independently stored. Since L-point FFT is performed, there is an advantage that the calculation processing speed is fast.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below. The signal processing means of this pulse Doppler radar device includes a storage means for storing the digital signal output from the receiving means based on the range pin number and the pulse hit number, and a range pin calculation for determining the range pin number where the target exists for each pulse hit. By providing means for calculating the phase compensation term of the digital video signal of the calculated range pin number, and means for calculating the sum of products of the digital video signal and its phase compensation term, the target being observed moves the range pin. However, the range pin number where the target exists for each pulse hit is tracked, the received signal is extracted, and coherent integration is performed, so the total number of pulse hits N and the integration area where the target signal exists can be made the same. , the integral output can be increased, and the SNR
A pulse Doppler radar device that enhances the improvement effect can be obtained.

Further, the signal processing means of this pulse Doppler radar device includes a first storage means for storing the digital video signal output from the receiving means in a two-dimensional grid pattern based on the range pin number and the pulse hit number, and a first storage means for storing the digital video signal output from the receiving means in a two-dimensional grid pattern based on the range pin number and the pulse hit number. , a means for dividing into units of a specific number of pulse hits and performing fast Fourier transform on each, a second storage means for storing the frequency spectrum of the output of the fast Fourier transform, and a range pin number where a target exists for each specific number of pulse hits is determined. Range pin calculation means. A phase compensation term calculation means for a frequency spectrum selected from the second storage means based on the range pin number calculated above, and a product-sum calculation means for performing a product-sum calculation of the frequency spectrum and its phase compensation term. As a result, even if the target under observation moves the range pin, the range pin number where the target exists for each specific number of pulse hits is tracked, the corresponding fast Fourier transform means output is selected, and coherent integration is performed. The total number of pulse hits N and the integral region in which the target signal exists can be made almost the same, and the integral output can be increased.
A pulse Doppler radar device that enhances the NR improvement effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration of =^Question 1, FIG. 2 is a flowchart explaining the operation of the signal processing means shown in FIG. 1, and FIG. 3 is a memory of the storage means shown in FIG. A diagram showing an example of the target signal presence region and integral region on the map. FIG. 4 shows claim 2. FIG. 5 is a block diagram showing an example of the configuration of an embodiment of the present invention. FIG. 5 is a diagram showing an example of the existence region and integration region of the target signal on the memory map of the storage means shown in FIG. 4. FIG. The configuration block diagram, FIG. 9, is a diagram showing an example of the target signal existence region and integral region on the memory map of the storage means of FIG. 8. In Figure 1, (131 is a storage means, (17) is a signal processing means, (105) is a product-sum calculation means. (106)
) is a phase compensation term calculation means, (107) is a range pin calculation means, in FIG. 4, (501) is an FFT means, (502) is a second storage means, (503) is a complex multiplier, (504) is a compound adder, (505) is a product-sum calculation means, (506) is a phase compensation term calculation means, (5
07) is a range pin calculation means, and 1508) is a signal processing means. In addition, the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A transmitter that generates a transmission pulse, an antenna that radiates radio waves output from the transmitter toward a target and receives radio waves reflected by the target, and after phase-detecting the received signal. , in a pulse Doppler radar device comprising a receiving means for A/D converting into a digital video signal, a signal processing means for detecting a target after coherently integrating the output of the receiving means, and a display for displaying the detected target. , the signal processing means converts the digital video signal output from the receiving means into two signals based on the range pin number and the pulse hit number.
a storage means for storing data in a dimensional grid; a range pin calculation means for calculating a range pin number where a target exists for each pulse hit; a calculation means for calculating a phase compensation term of a digital video signal of the calculated range pin number; 1. A pulse Doppler radar device comprising a product-sum calculation means for calculating the sum of products and a phase compensation term thereof. 2. A transmitter that generates a transmission pulse, an antenna that emits radio waves output from the transmitter towards a target and receives radio waves reflected by the target, and after phase-detecting the received signal, converts it into a digital video signal. In the pulse Doppler radar device, the signal processing means includes a receiving means for /D conversion, a signal processing means for detecting a target after coherently integrating the output of the receiving means, and a display for displaying the detected target. , a first storage means for storing the digital video signal output from the receiving means in a two-dimensional grid pattern based on the range pin number and the pulse hit number; means for fast Fourier transform; second storage means for storing the frequency spectrum of the output of the fast Fourier transform means; range pin calculation means for calculating the range pin number where the target exists for each specific number of pulse hits; and the calculated range pin number. a phase compensation term calculation means for a frequency spectrum selected from the second storage means based on the above, and a product-sum calculation means for performing a product-sum calculation of the frequency spectrum and its phase compensation term. Doppler radar equipment.