RU2348945C1 - Method of increase of resolution ability of radar-tracking ultrabandwidth sounding - Google Patents

Abstract

FIELD: physics, measuring.

SUBSTANCE: invention concerns field of radar-tracking sounding with use single ultrabandwidth (UBW) pulsing signals and can be used at sounding of several, approximate objects, for example, stratums of an asphalt coat. The method consists that radiate N - a petal sounding radio-frequency pulse, continuously accept the reflected signal, integrate it N-1 time in the chosen temporary window, find out and estimate signals from objects of examination.

EFFECT: increase of accuracy of the UBW resolution ability of sounding.

6 dwg

Description

The invention relates to the field of radar sensing using ultra-wideband (UWB) pulsed signals of duration T and can be used to probe several objects whose distance L is comparable to cT, where c is the speed of light in the medium, i.e. in conditions when the signals reflected from several objects of study overlap each other. Such a problem arises, for example, when probing subsurface soil layers, in particular multilayer asphalt roads.

в том числе одиночный многолепестковый зондирующий радиолокационный СШП сигнал.It is known [1], p.24, that any signal S (t) that can be emitted by the antenna must satisfy the condition:

including a single multi-lobe probing radar UWB signal.

In UWB radar sensing of several closely located objects of research, the problem of resolving signals received from one and the other objects arises. This problem is exacerbated by the presence of interference, imperfect transceiver equipment and many other factors.

The traditional method of preliminary processing of the radar signal reflected from the object of study is its detection - the allocation of the low-frequency function - the amplitude (complex) envelope of the radio pulse. When working with UWB signals, the amplitude envelope of the UWB signal obtained using the Hilbert transform does not always correctly reflect the features of its shape [1] p. 17. In this case, a potentially high resolution of UWB signals is not realized.

Known [2] Patent RU 2141674 - a method of radar ultra-wideband sounding, which consists in emitting a pulse with one antenna, receiving this pulse with another - with a remote antenna, the received pulse is delayed, re-emitting and receiving an antenna located in the place of the primary radiation. This method allows to spread in time the signals received from the antenna and from the surrounding structural elements. With this method, the resolution problem is solved by temporarily diversity of the reflected signals.

The disadvantage of this method is the limited scope, due to the fact that the possibility of artificial diversity in time of reflected signals from several objects of study is rare.

Closest to the claimed method is [3], which consists in the fact that they emit an N-lobe, probing radio pulse, continuously receive a reflected signal in a selected time window, detect and evaluate signals from objects of study. To solve the problem, permissions determine:

- a direct signal from the radiating to the receiving antenna (when probing the open space), which is subtracted from the received signal during subsequent soundings of the medium;

- a signal of total reflection during sounding of a metal sheet, which is used to calibrate subsequent soundings.

The direct signal is subtracted from the signal received from the objects of research. Then, in turn, the closest response is detected, and taking into account the attenuation of the known signal of total reflection, it is subtracted from the received signal. Thus, it is theoretically possible to resolve the received signals.

The disadvantage of this method is the low accuracy. Firstly, the signal passing through the medium changes the frequency spectrum, and therefore, not only the amplitude, but also its shape. As a result, it turns out to be inappropriate to use the full reflection signal as a calibration signal. Secondly, the recursive nature of the processing, in which each new object is detected by the results of the previous one, leads to the accumulation of errors.

The problem solved by this invention is to increase the resolution of UWB soundings reflected from nearby objects, and therefore, to obtain more and better information from radar sensing.

To solve the problem in a method of increasing the resolution of radar ultra-wideband sounding, which consists in emitting an N-lobe probing radio pulse, continuously receiving a reflected signal in a selected time window, detecting and evaluating signals from objects of study, integrating the reflected signal in a selected time window N -1 times, and use the results of integration to detect and evaluate signals from objects of study.

A significant difference of the proposed method from the prototype is that when archiving the N-lobe radio pulse integrate the reflected signal in the selected time window N-1 times.

The prototype uses the operation of subtracting known responses from the received signal.

Using N-1 multiple integration - a linear method of converting received signals, allows you to convert their multi-lobe time structure into a single-lobe. Figure 1 shows that a three-petal radio pulse after a single sounding becomes two-petal, and after the second integration - single-petal. If such an impulse could be emitted by the antenna, then the task of resolving nearby objects was greatly simplified. Integrating the received signal for a linear system is equivalent to integrating the input signal. Thus, the integration of the output signal greatly simplifies the resolution of nearby objects.

The inventive method is illustrated by the following graphic materials.

Figure 1 - the results of the sequential integration of the three petal signal.

Figure 2 - partial signals reflected from three objects.

Figure 3 - the total signal reflected from three objects.

4 is a result of a single integration of the reflected signal.

Figure 5 - the result of double integration of the reflected signal.

Consider the possibility of implementing the proposed method.

When radar sensing can be used single radio pulses with a small number of time lobes N = 2-5, for example, a three-pulse pulse S (t), shown in figure 1. Such signals have a UWB spectrum. Their processing is possible in the frequency or time domain. In both cases, it is necessary to detect signals reflected from the objects of study, to assess their amplitude, polarity, time position and other parameters. Such soundings are used, for example, in the study of pavement layers. In this case, the objects of study are the boundaries of the coating layers, reflecting the probing signal and possessing different permittivities ε. Depending on the ratio of permittivities ε of the media, the reflected signals can have different polarity.

If the objects of study (pavement layers) are located close to each other, then the reflected signals overlap each other. Figure 2 shows the partial signals S _3i (t), (i = 1, 2, 3), reflected from three different layers. Each of them has its own amplitude and shape. The signal S ₃₂ (t) has the opposite polarity. The total reflected signal S ₃ (t) = S ₃₁ (t) + S ₃₂ (t) + S ₃₃ (t), figure 3, is unsuitable for analysis. To solve the resolution problem, it is possible to reduce the duration of the probe signal S (t), however, this will lead to an unjustified increase in the development cost or to technical unrealizability.

фиг.4 не решает проблему разрешения, а повторное интегрирование

фиг.5, позволяет достаточно точно оценить, как временное положение, полярность и амплитуду отраженных сигналов. Указанная оценка может быть получена визуально или с использованием компьютера.Single integration of signal reflected from objects

4 does not solve the resolution problem, but reintegration

figure 5, allows you to accurately assess how the temporary position, polarity and amplitude of the reflected signals. The specified assessment can be obtained visually or using a computer.

Note that using the proposed linear transformation, the restoration of the ratio of the amplitudes of the partial signals and the distance between them is possible even in the case when the signals are delayed relative to each other for a time shorter than the length of the period of the central harmonic of the signal spectrum, i.e. in terms of the implementation of potential resolution in range [4].

Thus, the inventive method allows for UWB radar sensing to detect objects of study, approaching the potential resolution.

Consider the possibility of practical implementation of the proposed method. Figure 6 shows a diagram of a device that implements the inventive method, where:

1. UWB signal generator.

2. Transmitting antenna.

3. The receiving antenna.

4. The investigated multilayer medium.

5. Stroboscopic receiver.

6. Managed delay line.

7. An analog-to-digital converter (ADC).

8. The computer.

The signal from the computer 8 starts the UWB signal generator 1, which is emitted by the antenna 2. The UWB signal reflected from the studied multilayer medium 4 enters the antenna 3. The delay line 6 controlled by the computer 8 starts the stroboscopic receiver 5, which emits one instantaneous amplitude of the reflected signal. An analog-to-digital converter 7 converts this value into a code that is read by computer 8. The start frequency of the generator 1 can be tens of kilohertz, which does not require high speed ADC 7. The delay value 6 sets the reception window and the position of the reference point in it. Repeating the measurements many times, it is possible to average the values of this sample of the reflected signal, and by changing the delay value, we can obtain the entire implementation of the reflected signal in the selected time window accurate to the time-scale transformation. Thus, as a result of repeated sounding, the instantaneous amplitudes of the reflected signal are stored in the memory of the computer 8 in the reception window. Integration of the received digital samples is carried out by sequentially summing the samples, and multiple - by the sequential application of this procedure. In Fig.1-5, the abscissa axis shows the numbers of the UWB signal samples. The obtained integration results can be processed visually by the operator, or by known processing methods in computer 8.

Thus, the proposed method is technically feasible and allows you to increase the resolution of radar ultra-wideband sounding.

List of references

1. Astanin L.Yu., Kostylev A.A. Basics of ultra-wideband radar measurements. - M .: Radio and communications, 1989 .-- 192 p .: ill.

2. Patent RU 2141674.

3. Patent FR 2626666.

4. Theoretical Foundations of Radar / Ed. V.E.Dulevich. - M .: Owls. Radio, 1978.- 608 p.

Claims (1)

A way to increase the resolution of ultra-wideband radar sensing, which consists in emitting an N-lobe probing radio pulse, where N = 2, 3, 4, 5 ... continuously receive reflected signals in a selected time window, detect signals from objects of study, measure and evaluate parameters of signals reflected from objects of study, characterized in that the sounding of the object of study with an N-lobe radio pulse is carried out repeatedly, when receiving reflected signals of a controlled magnitude of a delay set a reception window with the ability to get the entire implementation of the reflected signal in the selected time window and the position of the reference point in it, integrate the received samples of the reflected signal in the selected time window for receiving N-1 times, converting the N-lobed temporal structure of the signal into a single-lobe, providing resolution nearby objects of study, use the results of integration to detect objects of study, measure and evaluate the parameters of signals from objects of study.

Images