JP2760625B2 - Non-carrier pulse radar - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse radar, and more particularly to a non-carrier pulse radar most suitable for exploring a short distance such as an ice radar or an underground exploration radar.

[Conventional technology]

A general pulse radar that transmits a pulse with a high-frequency carrier inserted toward a target object cannot reduce the pulse width of the pulse due to the necessity of carrier insertion,
It is difficult to detect an echo (reflected wave) from a short distance. (When the round-trip time of the radio wave to the target is equal to or less than the pulse width of the pulse transmitted from the radar, the reflected wave is received during the duration of the transmitted wave. Therefore, it is impossible to search for the target object due to a mixture of the transmission wave and the reception wave.)

For this reason, for example, in an ice radar or an underground exploration radar for the purpose of short-range exploration, a pulse wave is amplified to a high level and fed directly to the antenna, and a wide band generated at the rising portion and the falling portion of the pulse wave. A frequency component (high frequency) is transmitted, and the transmission pulse width is substantially very short. Such a radar is generally called a non-carrier pulse radar.

In such a non-carrier pulse radar, for example, in order to improve the detection range resolution and the minimum detection range capability (so that a target approaching the antenna can be detected), for example, 1 nSs
A very narrow pulse with a width of ec to 10 nSec is used.

[Problems to be solved by the invention]

In the above conventional non-pulse radar, great efforts have been made to reduce the pulse width of the pulse used in order to increase the detection distance resolution and the minimum detection distance capability,
Not only is there a limit to the narrowing of the pulse (pulse width
It is difficult to realize a pulse oscillator of 1nSec or less), and since the broadband frequency component is generated at both the rising and falling parts of the pulse, a fundamental solution for maximizing the detection distance resolution and the minimum detection distance capability Not a solution.

That is, as shown in FIG. 3, when the pulse shown in A is directly applied to the transmitting antenna, a broadband frequency component (high frequency) is generated in the rising part and the falling part of the pulse as shown in B. This is the transmitted wave (exploration radio wave)
Radiated from the transmitting antenna. This exploration radio wave is reflected by the target and becomes a received wave as shown in C or D. When the distance to the target is sufficiently longer than the pulse width τ of the pulse, as shown in C, , B, there is no confusion in the search for receiving the received wave after the emission of the two transmitted waves, but if the target is located at a place where the round-trip time of the radio wave corresponds to the pulse width τ of the pulse or less, As shown in B, the received wave is in a state where the reflected wave is received in the presence of the pulse shown in A, that is, before the radio wave generated at the falling portion of the pulse is radiated, and confusion occurs in the search. For this reason, it is necessary to keep the receiver of the radar inactive while the pulse indicated by A is present. Therefore, it is impossible to search for a target whose reciprocation time of the radio wave is equal to or less than the pulse width τ. .

As described above, in the conventional non-carrier pulse radar, the detection distance resolution and the initial detection distance capability cannot be increased below the distance that radio waves reciprocate within the time of the pulse width τ.

The present invention proposes to solve the above-mentioned problems of the conventional non-carrier pulse radar, and has an object to provide a novel non-carrier pulse radar capable of searching for a target at an extremely short distance. It is assumed that.

[Means for solving the problem]

Due to the above problems, the present invention provides an alternative to the conventional pulse,
Use a rectangular wave whose time width is much longer than the pulse,
The time from the rise to the fall of the rectangular wave (the duration in the rising direction of the square wave) and the time from the fall to the rise (the duration in the fall direction of the rectangular wave) are the maximum distances in the measurement range. Are set so as to be longer than the round trip time of the radio wave corresponding to, and the broadband frequency components generated when the rectangular wave rises and falls, respectively, are used as search radio waves (transmitted waves).

[Action]

Each of the rising time and the falling time of the rectangular wave is set to be equal to or longer than the maximum distance corresponding to the maximum distance within the measurement range. Since only reflected waves exist and transmitted waves cannot coexist, it is possible to search for a target even if the reflected waves are received immediately after the emission of the radio waves for detection, and the detection distance resolution And the minimum detection distance ability will be dramatically improved.

〔Example〕

FIG. 1 is a block diagram of the non-carrier pulse radar according to the embodiment of the present invention, and FIG. 2 is a time chart showing the operation of the non-carrier pulse radar shown in FIG.

As shown in FIG. 1, a non-carrier pulse radar according to an embodiment includes a transmitting unit 1 including a trigger circuit 101 and a rectangular wave oscillator 102, and a transmitting antenna that is fed by the transmitting unit 1 with a rectangular wave and emits a search radio wave. 2. A receiving antenna 3 for receiving a reflected wave of an exploration radio wave emitted from the transmitting antenna 2 at a target, and a receiving unit 4 for detecting the reflected wave received by the receiving antenna 3 by a technique such as detection and sampling. A processing unit 5 for performing search data processing of a target based on the reception signal of the reflected wave detected by the reception unit 4; a display unit for displaying search data of the target based on the processing data of the processing unit 5 6 and so on. Note that each of the receiving unit 4, the processing unit 5, and the display unit 6 can be configured by a conventionally known technique in the field of radar technology, and thus will not be described in detail.

Further, the rising and falling characteristics of the rectangular wave output from the rectangular wave oscillator 102 are required to be steep so that the exploration radio wave described later has a frequency component over a wide band. According to this, a rectangular wave oscillator having steepness that can sufficiently cope with the implementation of the present invention can be easily obtained.

As shown in FIG. 2, the trigger circuit 101 of the transmitting unit 1 generates a trigger pulse at a period T. The cycle T of the trigger pulse is set to be equal to or longer than the time during which the radio wave reciprocates the search distance of the maximum distance Xm within the measurement range. Further, the rectangular wave oscillator 102 oscillates a rectangular wave (a rectangular wave having a period of 2T) reflected every time T by reflecting an output every time a trigger pulse is input from the trigger circuit 101.

The rectangular wave signal transmitted from the transmitting unit 1 as described above is directly applied to the transmitting antenna 2. Here, "direct application" refers to application without performing processing such as modulation or the like that changes the rectangular wave signal waveform itself, and when applied to the transmitting antenna 2 through a capacitor after simple amplification, It is within the range of “directly apply”.

When the rectangular wave signal is applied to the transmission antenna 2, the rising and falling characteristics of the rectangular wave are set to be steep, so that a wideband frequency component ( A high frequency is generated, and this broadband frequency component is radiated from the transmitting antenna 2 as a transmission wave (exploration radio wave) as shown in FIG.

The period of the transmission wave radiated from the transmitting antenna 2 is equal to the period T of the trigger pulse (1/2 of the period of the rectangular wave), and the period T is, as described above, the maximum distance Xm within the measurement range. Since the reciprocating time is set to be equal to or longer than the time, the received wave (reflected wave) from which the transmitted wave is reflected by the target object always enters the receiving antenna 3 within the period T as shown in FIG. Therefore, the transmission wave of the next cycle from the transmission antenna 2 is not radiated before receiving the reception wave.

The receiving unit 4 detects the received wave, receives a trigger pulse from the transmitting unit 1, and detects the received wave incident on the receiving antenna 3 by a known method such as sampling.

Next, process 5 performs exploration data processing based on the transmission timing of the transmission wave based on the trigger pulse from the transmission unit 1, the reception timing of the reception wave based on the reception wave detection signal from the reception unit 4, and the like. To display the exploration data.

By the way, since the measurement range and the cycle of the rectangular wave need to maintain the relationship described above, the cycle of the rectangular wave also needs to be switched to a different time by switching the measurement range. This can be easily achieved by changing the period of the trigger pulse from. In this case, it is also possible to control the trigger circuit based on the received wave detection information in the processing unit 5 (control in the direction indicated by the dotted line in FIG. 1) and automatically switch the measurement range. It is. That is, the measurement range is sequentially switched from the short search range to the long search range (the cycle of the trigger pulse is sequentially switched to a longer direction), and the transmission timing of the transmission wave is monitored by the processing unit 5 (trigger pulse). If the first measurement range in which a received wave is detected while two transmitted waves are radiated is set as the optimum measurement range at that time, a search can always be performed with high resolution.

Further, the output characteristic of the square wave oscillator 102 is
It is also possible to make two inversions by one trigger pulse from (i.e., to send one cycle of rectangular wave output by one trigger). In this case, the rising time and the falling time of the rectangular wave are different depending on the characteristics of the rectangular wave oscillator 102 while maintaining the relationship between the measurement range and the period of the rectangular wave. Time, which suggests the possibility of exploration with two measurement ranges at the same time.

〔The invention's effect〕

As described above, according to the present invention, the duration in the rising direction and the duration in the rising direction (usually a half cycle) are longer than the time corresponding to the reciprocation of the radio wave in the maximum distance within the measurement range. The broadband frequency component generated when the rectangular wave rises and falls when the rectangular wave set in the above is applied to the transmitting antenna is used as an exploration radio wave.As in the conventional non-carrier pulse radar, the Since the disturbing second transmission wave is not radiated, the detection distance resolution and the shortest detection distance capability are greatly improved, and the high-frequency components generated at the time of rising and falling after the rectangle are both reduced. Both can be used as search radio waves, and the search efficiency is very good.

Also, it is very easy to sharpen the rising and falling characteristics of a rectangular wave as compared with narrowing the pulse width, and it is very easy to narrow the pulse width and the sharpness of the rising and falling characteristics of the pulse. The non-carrier pulse radar according to the present invention can be configured very easily as compared with the conventional non-carrier pulse radar which requires both.

Further, the present invention has an extremely remarkable effect, for example, the measurement range can be easily switched by variably setting the period of the rectangular wave signal.

[Brief description of the drawings]

FIG. 1 is a block diagram of a non-carrier radar according to an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of the non-carrier radar shown in FIG. 1, and FIG. It is a time chart shown. DESCRIPTION OF SYMBOLS 1 ... Transmission part, 101 ... Trigger circuit 102 ... Square wave oscillator, 2 ... Transmission antenna 3 ... Reception antenna, 4 ... Reception part 5 ... Processing part, 6 ... Display part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (4)

(57) [Claims] 1. A rectangular wave set so that the time from rise to fall and the time from fall to rise are longer than the time corresponding to the reciprocation of the radio wave within the maximum distance within the measurement range. A non-carrier pulse radar which is applied to a transmission antenna and emits a wideband frequency component generated at the time of rise and fall of the rectangular wave as a search radio wave from the transmission antenna. 2. The non-carrier pulse radar according to claim 1, wherein the time from the rise to the fall of the rectangular wave is set equal to the time from the fall to the rise. 3. The non-carrier pulse radar according to claim 1, wherein the time from the rise to the fall and the time from the fall to the rise of the rectangular wave are set to different times. . 4. The method according to claim 1, wherein the period of the rectangular wave is changed in accordance with the time from the transmission of the search radio wave to the reception of the reflected wave of the search radio wave, thereby automatically switching the measurement range. 4. The non-carrier pulse radar according to any one of 1 to 3.