JPH05126943A - High-resolution radar equipment - Google Patents

Abstract

PURPOSE:To obtain a high distance-resolution acquiring ability and antidisturbance ability by arranging radar transmitting frequencies without following the increasing or decreasing order of the frequencies so that the frequencies cannot overlap upon another and a fixed frequency range can be covered without omission. CONSTITUTION:A target is irradiated with transmitting signals from an antenna 4, with their radar transmitting frequencies being ranked and the reflected waves of the signals are inputted to a signal processor 6 after the waves are received and demodulated by means of a receiver 5 as radar echoes from the target. The processor 6 immediately reproduces a radar echo about the target by performing high-speed inverse Fourier transformation on the signals. The reproduced result is displayed on an indicator 7. Thus the target is irradiated with transmitting signals at every pulse in such a state that, for example, their radar transmitting frequencies being ranked so that the frequencies cannot overlap upon another and a fixed frequency range can be covered without omission. Therefore, the disturbance of the transmitting signals becomes hard, because the content of the transmitting signals is not easily predicted from the target side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high resolution radar device for reproducing a radar echo having a high range resolution, and more particularly to a stepped frequency.
The present invention relates to an implementation of a device that can improve the high range resolution acquisition method called the ncy system) and acquire a high range resolution for a target more safely.

[0002]

2. Description of the Related Art The stepped frequency system, which has been conventionally adopted as a radar device to obtain a high range resolution with respect to a target, is basically (1) at the time of transmission, a constant level as shown in FIG. Multiple radar transmission frequencies f0 to f assigned at equal frequency intervals of
While n is switched for each pulse, they are transmitted according to the ascending order or the descending order of the values of the radar transmission frequencies. (2) At the time of reception, inverse Fourier transform is applied to the signals sequentially received corresponding to these transmission signals, Play this.

This is a method for obtaining a desired radar image by repeating the procedure described above, whereby a high range resolution for the target can be obtained.

Since the inverse Fourier transform executed at the time of reception is usually a so-called FFT (Fast Fourier Transform), all of the received signals are appropriately used for the implementation. It is usual that the signals are once recorded in a storage means, and then these received signals are rearranged in an order called a bit reverse order and an inverse Fourier transform process is executed.

[0005]

It is certainly possible to obtain a high range resolution for the target by adopting such a stepped frequency system, but for that purpose, as described above, equal frequency is obtained. Since it is necessary to transmit a plurality of radar transmission frequencies f0 to fn assigned at intervals in ascending order or descending order of the values of the radar transmission frequencies, on the contrary, the target side or the target by such a radar device. From the side of making echo acquisition inconvenient, this radar transmission frequency can be easily predicted, and it is easy to interfere with such radar processing by the device.

As described above, although the radar device adopting the stepped frequency system can obtain a high range resolution with respect to the target, it cannot be denied that it is vulnerable to interference.

The present invention has been made in view of the above circumstances, and solves the above-mentioned drawbacks of the stepped frequency system and is excellent not only in the distance resolution acquisition performance for the target but also in the anti-jamming performance. An object is to provide a high resolution radar device.

[0008]

In order to achieve such an object, according to the present invention, a plurality of radar transmission frequencies assigned at a constant equal frequency interval are switched for each pulse and transmitted, and these transmission signals are handled at the time of reception. Assuming a high-resolution radar device by the above-mentioned stepped frequency system that reproduces a radar echo having a high distance resolution by performing an inverse Fourier transform, the transmission order of a plurality of radar transmission frequencies switched and transmitted for each pulse. Is an array that does not follow the ascending order or the descending order of the frequency values that does not overlap the radar transmission frequencies and includes a certain fixed frequency range.

[0009]

According to the stepped frequency system, basically, as long as a plurality of radar transmission frequencies do not overlap with each other and a condition including a certain frequency range is completely satisfied, an array of these transmitted signals and The array of received signals when the inverse Fourier transform is executed is associated with a predetermined rule that corresponds to, for example, the bit reverse order, so that the radar based on high distance decomposition for the target. Reproduction of echo is realized. Therefore, the transmission order of the plurality of radar transmission frequencies to be transmitted is "an array that does not follow the ascending order or the descending order of the frequency values, which does not overlap the radar transmission frequencies and fully includes a certain frequency range". In other words, even if the transmitted signals are rearranged under the condition that "their radar transmission frequencies do not overlap and completely cover a certain frequency range", after the reception, the inverse Fourier transform is performed. If such correspondence is properly made when the step (1) is executed, the radar echo reproduction performance with the high range resolution as the stepped frequency system is maintained. And it becomes difficult to interfere with this.

When the selected number of the radar transmission frequencies is a power of 2, the transmission order is particularly the bit reverse order when the binary code is sequentially assigned from the low frequency side or the high frequency side. By complying with the above, it becomes unnecessary to temporarily store the received signals and rearrange the received signals at the time of the inverse Fourier transform by the above-mentioned FFT (Fast Fourier Transform), and it is possible to obtain excellent distance resolution acquisition performance and anti-interference. It is possible to more efficiently reproduce the radar echo while maintaining the performance.

Incidentally, in the case where the transmission is performed in the bit reverse order in this way, the intermediate calculation result by the FFT can be obtained at the time when the signal corresponding to, for example, half the total frequency is transmitted. Therefore, it is not necessary to delay the start of calculation until all transmissions are completed.

Further, although the intermediate calculation result here means that the processable range, that is, the observation range is half, the resolution itself is no different from the resolution finally obtained. This means that when the target to be targeted is small, the radar echo with high resolution for the target is reproduced without waiting for the final result of the FFT.

[0013]

1 shows an embodiment of a high resolution radar device according to the present invention.

That is, in the radar device of this embodiment, 1 is a high-frequency oscillator that oscillates a highly stable high-frequency signal that serves as a reference for a transmission signal, and 2 is defined in FIG. 4 based on the oscillated high-frequency signal. A transmitter for transmitting and outputting a plurality of (in this case, a power of 2) radar transmission frequencies assigned at constant frequency intervals within a certain frequency range for each pulse.
Is a transmission / reception switcher composed of a circulator or the like, 4 is an antenna for irradiating the transmission signal supplied via the transmission / reception switcher 3 toward a target, and 5 is an antenna for taking the reflected wave into the radar device. A receiver 6 which receives and demodulates a high-frequency reception signal, which is taken in by the radio frequency converter 1 and is input via the transmission / reception switch 3, in a predetermined manner based on the high-frequency signal oscillated from the high-frequency oscillator 1. The signal processor that reproduces the radar echo for the target by applying the above-described inverse Fourier transform by the FFT to the signal, 7 is an indicator that displays the reproduced radar echo in a predetermined manner, and 8 is the transmission Machine 2
The frequency control for controlling the high-frequency oscillator 1 so that the transmission order of the radar transmission frequencies consisting of powers of 2 according to the order follows the bit reverse order when binary codes are assigned in order from the low frequency side or the high frequency side. It is a vessel.

The rearrangement control of the frequency controller 8 in the reverse bit order will be described with reference to FIGS. 2 and 3.

For simplification, FIG. 2 shows four binary codes, which represent "0" to "3", that is, 2 squared binary codes, in which the codes are rearranged in a bit-reverse order. It is shown as a table.

That is, as shown in FIG. 2, in the frequency controller 8, (1) for the binary number "00" indicating the decimal number "0", the respective bits are rearranged in the reverse order. 00 ”, and the corresponding decimal number“ 0 ”is newly assigned.

(2) Binary number "0" indicating the decimal number "1"
For "1", rearrange each bit in reverse order and
0 ”, and the corresponding decimal number“ 2 ”is newly assigned.

(3) Binary number "1" indicating the decimal number "2"
For "0", rearrange the bits in reverse order and
1 ”, and the corresponding decimal number“ 1 ”is newly assigned.

(4) Binary number "1" indicating the decimal number "3"
For "1", rearrange each bit in reverse order and
1 ”, and the corresponding decimal number“ 3 ”is newly assigned.

The rearrangement as described above is performed by a power of 2 transmitted from the transmitter 2 (here, a power of 2 = 4).
The transmission order of the radar transmission frequency of is performed.

As a result, from the transmitter 2, for example, f0 to
If the four radar transmission frequencies of f3 are normal (conventional), as shown in FIG. 3 (a), those that were repeatedly output in the order according to the ascending order of the frequency values are shown in FIG.
As shown in (b), the data will be rearranged and output in the order of f0->f2->f1->f3-> f0 ... within the same repetition period.

Therefore, according to the radar apparatus of this embodiment, the antenna 4 irradiates the target with the transmission signals in which the respective radar transmission frequencies are ordered in the manner shown in FIG. 3B. Further, the reflected wave is received and demodulated by the receiver 5 as a radar echo from the same target, and is input to the signal processor 6.

The signal processor 6 receives this signal as described above.
This is a well-known circuit that reproduces the radar echo for the target by subjecting the demodulated signal to the inverse Fourier transform by FFT, but in this embodiment, as described above, a plurality of pulses are transmitted by switching for each pulse. Since the transmission order of the radar transmission frequencies is rearranged in advance in this example in the bit reverse order when the binary code is assigned in order from the low frequency side, it is possible to perform the inverse Fourier transform by the FFT, but it is different from the conventional one. ◆ All of the received signals are temporarily recorded in an appropriate storage means.

After that, these recorded reception signals are rearranged in the reverse order of the bits.

It is not necessary to perform preprocessing such as. That is, in the signal processor 6, the inverse Fourier transform operation by FFT can be immediately executed on the input signal.

The radar echo reproduced through the inverse Fourier transform calculation by the signal processor 6 has a high distance resolution as described above and is displayed on the indicator 6.

As described above, according to the radar apparatus of the above-described embodiment, the target is irradiated with the transmission signals in which the respective radar transmission frequencies are ordered in the manner shown in FIG. 3B for each pulse. Therefore, it is difficult to predict the content of the transmission signal from the side of the target side or from the side that makes it inconvenient to obtain the target echo by such a radar device, and thus it is difficult to interfere with it.

Further, according to the radar apparatus of the embodiment, when the selected number of the radar transmission frequency is a power of 2, when the binary code is assigned in order from the low frequency side, the transmission order thereof is particularly low. Since it is made to follow the reverse order of the bits, it becomes unnecessary to temporarily store the received signals and rearrange the received signals at the time of the inverse Fourier transform by the FFT, and it is possible to more efficiently reproduce the radar echo.

Further, by rearranging the radar transmission frequencies in the reverse bit order and transmitting the signals, for example, when the signal corresponding to half the total frequency is transmitted, the FFT is performed.
Thus, the intermediate calculation result can be obtained, and it is not necessary to delay the start of the calculation until all transmissions are completed.

Further, although the intermediate calculation result here means that the processable range, that is, the observation range is half, the resolution itself is no different from the resolution finally obtained. Therefore, when the target target is small, the radar echo with high resolution for the target is reproduced without waiting for the final result by the FFT, and in some cases, the intermediate calculation result is obtained. After that, it becomes possible to terminate the subsequent transmission or processing. In other words, the scale of radar processing can be controlled according to the size of the target.

In the above embodiment, for the sake of convenience, the transmission order of the radar transmission frequencies is "followed by the bit reverse order when binary codes are sequentially assigned from the low frequency side".
However, this may of course be made to “follow the bit reverse order when binary codes are assigned in order from the high frequency side”.

Further, in the above embodiment, in order to shorten the reception signal processing as well, the transmission order of a plurality of radar transmission frequencies to be transmitted from the transmitter 2 by switching for each pulse through the frequency controller 8 is set as follows. Although the bits are rearranged in the reverse order when the binary code is assigned from the low frequency side (or the high frequency side), the transmission order of such radar transmission frequencies does not necessarily have to be the reverse bit order.

That is, the bit reverse order is certainly appropriate when the number of radar transmission frequencies is a power of 2, but in view of the characteristics of FFT, rearrangement not based on 2 is also possible. Therefore, the point is that the transmission order of the plurality of radar transmission frequencies switched and transmitted for each pulse does not overlap the radar transmission frequencies and includes a certain constant frequency range without fail, in ascending order of frequency values,
Alternatively, it suffices as long as the arrangement does not follow the descending order. And if these conditions are met,
The anti-jamming performance of this high resolution radar device is maintained well.

In this case, however, the information regarding the transmission order of the radar transmission frequencies rearranged and controlled by the frequency controller 8 is expressed by the broken line arrow added to FIG.
Based on the transmission order information of the radar transmission frequency transmitted to the signal processor 6, preprocessing for inverse Fourier transform by FFT, such as rearrangement of reception processing signals, is executed in the signal processor 6. Will be done.

[0036]

As described above, according to the present invention, it is possible to greatly improve the anti-jamming performance while keeping the radar echo reproducibility by the high distance resolution as the stepped frequency system at a minimum. Like

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a high resolution radar device according to the present invention.

FIG. 2 is a conversion table diagram showing an example of rearrangement processing in reverse bit order.

FIG. 3 compares the transmission order of a plurality of radar transmission frequencies transmitted by the stepped frequency system with a method based on ascending frequency values that has been conventionally used and a method based on the reverse bit order used in the above-described embodiment. Is a time chart shown by.

FIG. 4 is a graph illustrating definitions of a constant frequency interval and a constant frequency range for radar transmission frequencies adopted in the stepped frequency system.

[Explanation of symbols]

 1 High Frequency Oscillator 2 Transmitter 3 Transmit / Receive Switcher 4 Antenna 5 Receiver 6 Signal Processor 7 Indicator 8 Frequency Controller

Claims (2)

[Claims] 1. A radar having a high range resolution by switching a plurality of radar transmission frequencies assigned at constant and equal frequency intervals for each pulse and transmitting and performing an inverse Fourier transform corresponding to these transmission signals at the time of reception. A high-resolution radar device that reproduces echoes, the transmission order of a plurality of radar transmission frequencies that are transmitted by switching for each pulse, the radar transmission frequencies do not overlap, including a certain fixed frequency range, A high-resolution radar device characterized by an array that does not follow the ascending order or the descending order of frequency values. 2. The selected number of radar transmission frequencies is two.
The high-resolution radar device according to claim 1, wherein the transmission order is in the reverse order of bits when binary codes are assigned in order from the low frequency side or the high frequency side.