JP2681638B2 - Direct spread spectrum radar system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of spread spectrum communication technology. More specifically, the present invention relates to a method of widening (spreading) and modulating a spread spectrum signal with some kind of signal. Digitally modulated signal (carrier) with relatively high bit rate
The present invention relates to a radar apparatus using a direct spread (DS) modulation scheme using the same. [Summary of the Invention] A direct sequence spread spectrum radar to which the present invention is applied includes a transmitter that generates a radio wave modulated using the first pseudo noise, and a receiver that receives the reflected echo wave. The received signal is demodulated by using the second pseudo noise having the same code or the code having the same inverse code time series as each other with respect to the first pseudo noise and having the independent phase series. . The above first and second
The intensity of the reflected wave from a specific position is sequentially measured as a demodulation output while changing the code phase of the pseudo noise. The present invention, in such a direct diffusion radar device,
The function of identifying the position of a transponder having a frequency conversion function is provided. 2. Description of the Related Art A conventional radar apparatus generally uses an extremely short time pulse signal to repeatedly receive an echo signal from an object existing on a propagation path of the signal, thereby visually recognizing a surrounding situation. A method of expressing is used. Although this method can be realized with a relatively simple receiving device, it is necessary to transmit a microwave of an instantaneous but non-negligible level to secure a certain measurement range. Radar is legally regulated so that only certain operators can use it, for example, certain qualifications are set. Further, although the conventional radar device can generally display the existing position of the object on the site, the user often determines the identification of which one of them is the target. Even if special marking is done to assist the judgment, it is not easy to identify this on the image, and even if a dedicated device is installed for positioning, it will be in parallel with the conventional radar device. The unified expression of the result of the performed positioning requires a high degree of technical handling, especially in applications requiring high precision, and thus complicates the apparatus. [Problems to be Solved by the Invention] In consideration of such a situation, the invention of the “direct spread spectrum type radar device” of the same applicant has a very low level generated by the direct spread spectrum spread technique, but is extremely wide. A radar that can be widely used by general users by configuring a system that creates a radar image without disturbing the surroundings by investigating echo signals from the surroundings over a relatively long time using radio waves having a signal band Provide a scheme. In this direct spread spectrum radar device, a method of sequentially detecting the reflectance from the amount of the same code component contained in the reflected wave using a radio wave code-modulated by pseudo noise with a relatively long period as a medium. However, the pseudo noise used here can be very effectively used for measuring the distance between the transmission source and the transponder by using a proper transponder device as already generally known. However, in order to clarify the mere reflection of an object in the radar system and the response from the transponder, frequency conversion is always performed in the transponder, and the center frequency of the received signal and the center frequency of the transmission are intentionally constant. The amount of deviation is given, and when viewed from the radar side, this response signal receives the same response as if it had transmitted at a different center frequency. [Means for Solving the Problems] The present invention makes it possible to simultaneously know the response position of a specific transponder from different frequency bands by installing a receiver for this transponder signal in addition to the original radar receiver, It makes it possible to centrally process these data and display their exact position on the radar screen. [Operation] According to the present invention, it is possible to easily individually identify a plurality of transponders by the code signal or tone signal added to the transponders. FIG. 1 shows an embodiment of a direct-spread spectrum radar apparatus according to the present invention. This radar system uses two pseudo noise generators (1) and (2) 10 and 12. The pseudo noise generators 10 and 12 generate pseudo noises N1 and N2 belonging to the M series according to the same code, but their phases are generally not coincident with each other. In this embodiment, the pseudo noise N1 is used for code modulation of a transmission signal, and the pseudo noise N2 is used as a reference signal for echo detection on the receiving side. That is, the pseudo noise N1 is mixed or modulated with the carrier F _TX and then with transmission information such as a tone signal, given to the transmitter 14 and transmitted by the antenna 16. The signal transmitted from the antenna 16 with this F _TX as the center frequency can be demodulated using the same center frequency F _RX as the reflected wave from the reflector along the transmission direction. That is, the reflected wave received by the antenna 18 is given to the receiver 20. A correlator for performing a correlation analysis between the pseudo noise N2 from the second pseudo noise generator 12 and the received reflected wave, a convolver, or a demodulator for demodulating the received signal by the second pseudo noise is provided. In this embodiment, as described above, the pseudo noise N ₂ has the same code or a code in the inverse time series relationship of the same code with respect to the pseudo noise N ₁ .
Since the chip rate of N ₂ is set to be slightly slower than that of N 1, a phase shift gradually occurs after initialization by the phase difference detection and initialization control circuit 22 that receives pseudo noise N1 and N2. In other words, the observation points are gradually becoming farther away. The demodulated signal is supplied to the memory device and the image processing device 30 via the level measuring circuit 26 and the A / D converter 28. That is,
The received signal is demodulated by the reference noise N2 through a mixer, that is, a balanced modulator, etc., but if there is no reflected wave generated at the observation point in the received signal, generally no transmission information is included. Therefore, the demodulation result is only noise. On the contrary, when some reflected wave is included, the demodulation result mainly includes the transmission information of the level related to the reflection intensity and the distance. This is measured by the level measuring circuit 26, the output of which is provided to the display device 34 via the conversion circuit 28, device 30 controlled by the sampling control circuit 32. Therefore, the spot brightness of the display device 34 such as a CRT which performs time scanning from the center in the radial direction with the antennas oriented in substantially the same direction is modulated by modulating the spot luminance with a signal including this demodulation signal. The amount of reflection on the line can be displayed, and a radar image can be obtained by executing this in the forward direction as in the conventional radar system. For this,
The antenna direction control circuit 36 provides a signal representing the full scan to the sampling control circuit 32, and the control circuit 32 receives the signal representing the radial scan from the phase difference detection circuit 22 described above,
The output is output to the device 30. The above is the outline of the direct spread spectrum radar device disclosed in the above-mentioned another patent application. In the present invention, the center frequency of the response from the transponder device with frequency converter is shifted by F _TX + f, resulting in (F _RX
+ F) = F _RX ′ is demodulated by a demodulation operation assuming the center frequency. For this purpose, an additional structure, that is, a transponder receiver 40 is provided as a portion surrounded by a dotted line. That is, the transponder receiver 40 includes a balanced modulator 42 that receives pseudo noise N2 and the above-mentioned F _RX ′, a balanced modulator 44 that receives this output and the output of the receiver 20 and provides a demodulated signal, and the above-mentioned level. It includes a level measuring circuit 46 similar to the measuring circuit 26, and an A / D converter 48 receiving this output. The memory control circuit 50 is connected to the output of the level measuring circuit 46 and controls the converter 48 and the memory device / image processing device 30. Therefore, the two demodulated signals associated with F _RX and F _RX ′ are A /
Digitally sampled by D converters 28, 48,
Display device via memory device and image processing device 30
Create an image on 34. [Effects of the Invention] The data of the two types of screens captured in this way are sampled at approximately the same time point, so their mutual positional relationship is extremely stable, and complicated processing is not required. Highly accurate observation results can be obtained. INDUSTRIAL APPLICABILITY The present invention can be used particularly effectively for applications such as a fishery radar device, for example, when it is desired to grasp the exact arrangement of each fellow ship from a mother ship.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, 42,4
Reference numeral 4 is a two-phase balanced modulator, 46 is a level measuring circuit, 48 is an analog-to-digital converter, and 50 is a memory control circuit.

Claims (1)

(57) [Claims] A first pseudo noise generator, transmitting means for transmitting a transmission signal obtained by spread spectrum modulating a carrier according to transmission information by the first pseudo noise from the first pseudo noise generator, and a second Of the same pseudo-noise generator and a code from the second pseudo-noise generator to the first pseudo-noise generator in the same code or in the inverse time series relation of the same code, and the chip rate is slightly slower. A first pseudo-demodulated signal that is subjected to despread spectrum demodulation of a received signal having the same center frequency as that of the carrier obtained by receiving a reflected signal in response to the transmitted signal by the second pseudo noise, and outputting a first demodulated signal. Receiving means, a phase difference detection circuit for detecting a phase difference between the first pseudo noise and the second pseudo noise, and a phase difference detection from the phase difference detection circuit. Initialization control circuit for initializing the second pseudo noise generator for each predetermined phase difference according to the signal, and first sampling means for measuring the level of the first demodulated signal and sampling the measurement output. And a second demodulated signal that is obtained by receiving the reflected signal due to the second pseudo noise and that has the same center frequency as the carrier of the transponder device and then performs a despread spectrum demodulation to output a second demodulated signal. An image for generating an image on the display device according to each output of the receiving means, the second sampling means for measuring the level of the second demodulated signal and sampling the measurement output, and the output of the first and second sampling means. Processing means, and a sump for controlling the first sampling means and the image processing means in accordance with the radial scanning signal and the all-round scanning signal corresponding to the phase detection signal. Direct spread spectrum type radar apparatus characterized by comprising a ring control means.