JPH03249587A - Non-carrier pulse radar - Google Patents

Abstract

PURPOSE:To improve the detection distance resolution and the shortest detection distance capacity by setting so that the continued time in the rise direction of a square wave and the continued time in the fall direction become longer than the reciprocating time of a radio wave corresponding to the maximum distance in a measuring range. CONSTITUTION:When a square wave signal is applied to a transmitting antenna 2, since a rise characteristic and a fall characteristic of this square wave are set so as to be steep, a frequency component of a wide band is generated at the time of rise and at the time of fall of this square wave, and this wide band frequency component is radiated as a transmitting wave from the transmitting antenna 2. In this case, when a measuring range is switched successively from a range whose probing distance is short to a range whose probing distance is long, transmitting timing of transmitting waves is monitored by the processing section 5 and a first measuring range which detects a receiving wave while two transmitting waves are radiated is set as an optimal measuring range at that time, probing can always be executed with high resolution.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a pulse radar, and particularly to a non-carrier pulse radar that is most suitable for short-distance exploration, such as ice radar and underground exploration radar. .

(Prior Art) A general pulse radar that sends a pulse into which a high-frequency carrier is inserted toward a target object cannot narrow the pulse width of the pulse due to the necessity of carrier insertion.
It is difficult to detect echoes (reflected waves) from a short distance (when the round trip time of the radio waves to the target is less than the pulse width of the pulse transmitted from the radar, it is difficult to detect echoes (reflected waves) from a short distance). Therefore, the transmitted and received waves will be mixed, making it impossible to search for the target.)

For this reason, in ice radar and underground exploration radar, which aim at short-distance exploration, a pulse wave is amplified to a high level and directly fed to the antenna, and a wide band generated at the rising and falling parts of the pulse wave is generated. The frequency component of (
(high frequency), and the transmission pulse width is substantially very short. This type of radar is generally called a non-carrier pulse radar.

In such a non-carrier pulse radar, in order to increase detection range resolution and minimum detection range capability (so that targets close to the antenna can be detected), for example, i in
Very narrow pulses of 5 sec to 10 n5 ec width are used.

[Problems to be Solved by the Invention] In the conventional non-pulse radar described above, great efforts have been made to narrow the pulse width of the pulses used in order to increase the detection range resolution and minimum detection range capability. , not only is there a limit to narrowing the pulse width (pulse width 1
(It is difficult to realize a pulse oscillator of n5ec or lower), since broadband frequency components are generated in both the rising and falling parts of the pulse, this is a fundamental solution to maximize detection distance resolution and minimum detection distance capability. It is not a strategy.

In other words, as shown in Figure 3, when the pulse shown in A is directly applied to the transmitting antenna, wideband frequency components (high frequencies) are generated in the rising and falling parts of the pulse as shown in B. , this is radiated from the transmitting antenna as a transmitted wave (probing radio wave). This exploration radio wave is reflected by the target object and becomes a received wave as shown in C or D.
When the distance to the target object is sufficiently long compared to the pulse width τ of the pulse, as shown in C, there will be no confusion in the search for the received wave to be received after the emission of the two transmitted waves shown in B. However, if the target is located at a location where the round trip time of the radio wave is less than or equal to the pulse width τ of the above pulse, the received wave will be reflected during the presence of the pulse shown in A, as shown in B.
In other words, the radio waves generated at the falling edge of the pulse are received before they are radiated, causing confusion in exploration. For this reason, it is necessary to keep the radar receiver inactive while the pulse shown in A is present, and therefore it is impossible to search for a target at a distance where the round trip time of the t-wave corresponds to less than the pulse width τ. be.

In this way, in conventional non-carrier pulse radar,
The detection distance resolution and the minimum detection distance capability cannot be increased below the distance that the radio waves travel back and forth within the time of the pulse width τ.

The present invention is proposed to solve the above-mentioned problems of the conventional non-carrier pulse radar, and aims to provide a novel non-carrier pulse radar that enables the exploration of targets located at extremely close distances. This is an issue to be addressed.

[Means for Solving the Problems] To solve the above problems, the present invention uses a rectangular wave having a much longer time span than the conventional pulse, instead of the conventional pulse, and uses a rectangular wave whose time width is much longer than that of the pulse. time (duration time in the rising direction of the square wave) and time from falling time to rising time (duration time in the falling direction of the square wave)
is set so that it is longer than the round trip time of the radio wave corresponding to the maximum distance within the measurement range, and the wideband frequency components generated at the rise and fall of the rectangular wave are used as exploration radio waves (transmission waves). .

[For production]

1 for each of the rising and falling directions of the square wave
! The duration time is set to be longer than the time equivalent to the maximum distance within the measurement range, so after the exploration radio waves (transmitted waves) are emitted, only reflected waves exist within the measurement range, and transmitted waves are mixed. Therefore, even if a reflected wave is received immediately after the radio wave for exploration is emitted, target detection becomes possible, and detection distance resolution and minimum detection distance capability are dramatically improved.

〔Example〕

FIG. 1 is a block diagram of a non-carrier pulse radar according to an 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, the non-carrier pulse radar of the embodiment includes a transmitter 1 including a trigger circuit 101 and a square wave oscillator 102, and is powered by a rectangular wave from the transmitter 1.
A transmitting antenna 2 that emits exploration radio waves, a receiving antenna 3 that receives the reflected waves of the exploration radio waves emitted from the transmitting antenna 2 at a target, and detecting and sampling the reflected waves received by the receiving antenna 3. A receiving unit 4 detects the target using the method described above, a processing unit 5 performs target object exploration data processing based on the received signal of the reflected wave detected by the receiving unit 4, and a target object is detected based on the processing data of the processing unit 5. It is composed of a display unit 6 etc. that displays exploration data. Note that each of the receiving section 4, the processing section 5, and the display section 6 can be constructed using conventionally known techniques in the field of radar technology, and therefore will not be described in detail.

Furthermore, the rise and fall characteristics of the rectangular wave output from the rectangular wave oscillator 102 are required to be steep so that the exploration radio waves, which will be explained later, have frequency components over a wide VR range. According to the above, a square wave oscillator having a steepness sufficiently compatible with the implementation of the present invention can be easily obtained.

As shown in FIG. 2, the trigger circuit 101 of the transmitter 1 generates trigger pulses at a period T.

The period T of this trigger pulse is the maximum distance within the measurement range 1i
It is set to be longer than the time it takes for radio waves to travel back and forth over the exploration distance of X m. Further, the rectangular wave oscillator 102 is connected to the trigger circuit 1
By inverting the output every time a trigger pulse is input from 01 onwards, a rectangular wave (a rectangular wave with a period of 2T) that is inverted every time T is oscillated.

The rectangular wave signal sent out from the transmitting section 1 as described above is directly applied to the transmitting antenna 2. In addition, here "
"Directly applying" means applying the rectangular wave signal without any processing that changes the waveform itself, such as modulation.If the signal is simply amplified and then applied to the transmitting antenna 2 through a capacitor, "directly applying" is within the range of

When the rectangular wave signal is applied to the transmitting antenna 2, since the rising and falling characteristics of the rectangular wave are steep, wideband frequency components ( This broadband frequency component is transmitted to the transmitting antenna 2 as shown in Figure 2.
It is emitted as a transmission wave (prospecting radio wave) from

The period of the transmission wave radiated from the transmission antenna 2 is equal to the period T of the trigger pulse (half the period of the rectangular wave),
As mentioned above, this period T is the maximum distance within the measurement range [l
Since iX m is set to be longer than the time required for the radio waves to travel back and forth, the received wave (reflected wave) from which the transmitted wave is reflected from the target object is always within the above period 1, as shown in Figure 2. The next cycle of transmission waves that are incident on the reception antenna 3 and sent from the transmission antenna 2 are not radiated before the reception wave is received.

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

Next, processing 5 performs exploration data processing based on the sending timing of the transmitted wave based on the trigger pulse from the transmitting unit 1 and the receiving timing of the received wave based on the received wave detection signal from the receiving unit 4, and performs exploration data processing on the display unit 6. The exploration data will be displayed.

By the way, since it is necessary to maintain the above-mentioned relationship between the measurement range and the period of the rectangular wave, it is necessary to switch the period of the rectangular wave to a different time by switching the measurement range. This is easily possible by changing the period of the trigger pulse from . In this case, the trigger circuit is controlled based on the received wave detection information in the processing unit 5 (control in the direction indicated by the dotted line in FIG. 1),
It is also possible to automatically switch the measurement range. That is, the measurement range is sequentially switched from a short range to a long range, and the period of the trigger pulse is sequentially switched in a direction that increases the number of crucian carp. ), the transmission timing of the transmission wave can be monitored by the processing unit 5 by monitoring the trigger pulse. ), if the first measurement range where the received wave is detected between the two transmitted waves is set as the optimal measurement range at that time, exploration can be performed with high resolution at all times.

In addition, the output characteristics of the rectangular wave oscillator 102 are
It is also possible to invert twice with one trigger pulse from 01 (that is, one period of the square wave output is sent out with one trigger). In this case, depending on the characteristics of the square wave oscillator 102, the duration time in the rising direction and the duration time in the falling direction of the square wave are different while maintaining the relationship between the measurement range and the period of the square wave. This suggests the possibility of simultaneous exploration with two measurement ranges.

Effects of the Invention) As explained above, the present invention provides a rise direction duration time and a rise direction duration time (usually 1/2 period).
is used to explore the wideband frequency components that occur at the rise and fall of a rectangular wave set so that the maximum distance within the measurement range is longer than the time equivalent to the round trip of the radio wave and applied to the transmitting antenna. Since it is a radio wave, and unlike conventional non-carrier pulse radar, a second transmitted wave that interferes with the received wave is not emitted, the detection distance resolution and shortest detection distance capability are dramatically improved. Furthermore, both the high frequency components generated at the rise and fall of the rectangular wave can be used as radio waves for exploration, resulting in very high exploration efficiency.

Furthermore, it is very easy to make the rising and falling characteristics of a square wave steeper than narrowing the pulse width, and it is very easy to make the rising and falling characteristics of a square wave steeper than narrowing the pulse width. The non-carrier pulse radar according to the present invention can be constructed very simply compared to the conventional non-carrier pulse radar which requires both of the following.

Furthermore, the present invention has extremely significant effects, such as being able to easily switch the measurement range by variable setting of the period of the rectangular wave signal.

[Brief explanation of 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 explaining the operation of the non-carrier radar shown in Fig. 1, and Fig. 3 is a diagram illustrating the operation of the conventional non-carrier radar. FIG. 1... Transmission section 101... Trigger circuit 10
2... Square wave oscillator 2... Transmission antenna 3...
Receiving antenna 4... Receiving section 5... Processing section
6...Display section 0m x m 0m 0m on

Claims (1)

[Claims] 1. A rectangle that is set so that the time from the rise to the fall and the time from the fall to the rise are longer than the time required for the radio wave to travel back and forth over the maximum distance within the measurement range. A non-carrier pulse radar in which a wave is applied to a transmitting antenna, and broadband frequency components generated at the rising and falling times of the rectangular wave are emitted from the transmitting antenna as exploration radio waves. 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 of the rectangular wave and the time from the fall to the rise of the rectangular wave are set to different times. 4. The method according to claims 1 to 3, wherein the period of the rectangular wave is changed in accordance with the time from the transmission of the exploration radio wave to the reception of the reflected wave of the exploration radio wave, thereby automatically switching the measurement lens. Non-carrier pulse radar described in any of the above.