RU2550365C1 - Method of distance determination to earth surface - Google Patents

Abstract

FIELD: radio-engineering, communication.

SUBSTANCE: current value of width of the selecting pulses Δt(i) is changes after each i detection of the reflected signals as Δt(i)≥Δt₁+2Δt_p(i-1), where Δt_p(i-1) is average error signal between received reflected signal and reference signal upon accurate tracking during previous detection of the reflected signals at third stage.

EFFECT: increased reliability of the method of distance determination to earth surface due to adaptation of selecting pulses width to speed of change of time delay of the reflected signal at second sub-stage of signal detection of third stage.

Description

The invention relates to the field of radar technology and can be used in the construction of various radar systems designed to determine the distance from a moving object to the earth's surface, using the principle of reflection of radio waves (radio rangefinders or rangefinders).

A known method for determining the distance D to the earth’s surface [1], used in radio range finders using the principle of reflection of radio waves, which consists in measuring the time delay t _RAD (time interval) from the moment of emission of the sounding signal to the moment of receiving the sounding signal reflected from the earth’s surface ( reflected signal).

The method [1] is implemented as follows.

A probe signal is emitted with a duration t of the _PROBE in the direction of the earth's surface with a period of T _C.

The front of the received reflected signal is differentiated so that the maximum of the differentiated signal is at the front of the reflected signal.

Detect (search) by the range of the signal reflected from the earth’s surface using selection pulses that move delays from minimum to maximum in the time range t _{REF. MAX} , which corresponds to a change in the distance from minimum to maximum along the distance. In this case, the selecting pulses have the same duration and amplitude.

The search (detection) process of the reflected signal ends when the maximum of the differentiated reflected signal coincides with a line at an equal distance from each breeding pulse.

Moreover, the duration of each selection pulse t _{SI is} set such that it exceeds the duration of the front t _{OTR of the} reflected signal

Tracking (tracking) of the detected signal by tracking its temporal position by maintaining a constant state when the maximum of the differentiated reflected signal coincides with the line of contact of the selecting pulses.

Measure the time interval equal to the time delay t _REFERENCE between the moment of radiation of the probing signal (pulse) and until the moment of receiving the reflected signal - the front of the reflected signal (maximum of the differentiated reflected signal).

The range D (distance) to the earth’s surface is calculated from the measured value t _REF by the formula

where c is the signal propagation speed.

The measured range value is output.

The disadvantages of the method [1] are:

- insufficient reliability of the method - the lack of detection of the reflected signal at a high rate of change of the time delay of the reflected signal;

- insufficient accuracy in determining the distance D to the earth's surface, which is determined by the duration of the selecting pulse t _SI , and it _is not possible to reduce the value of t _SI due to constraint (1), otherwise the reliability of detection and tracking of the reflected signal is reduced and signal loss may occur before it is measured parameters; the difference in the amplitudes and shape of the selection pulse also reduces the accuracy of determining the range;

- the impossibility of reliable detection of the reflected signal at signal-to-noise ratios close to unity;

- lack of accuracy in determining the range at low values of the signal-to-noise ratio, since interference increases the instability of the fronts of the selecting pulses and reduces the accuracy of determining the maximum of the differentiated reflected signal;

- a long time of detection (search) of the signal, which is determined by the time of movement of the selecting pulses in the time range t _{REAR MAX} from minimum to maximum;

- a high probability of false alarm and a low probability of correct detection of the reflected signal due to the absence of a signal when determining the range of accumulation of signals when determining the distance to the earth's surface.

There is a method of determining the distance D to the surface of the earth [2], selected as a prototype used in radio range finders using the principle of reflection of radio waves, and consisting in three-stage measurements - a rough measurement of range at the first stage, accurate measurement of range at the second stage, confirmation of the results of accurate measurement range results of rough measurement in the third stage.

The implementation of the method [2] is as follows.

The first stage is carried out in two sub-stages.

First sub-step

Emitting a probe signal _PROBE duration t in the direction of the earth's surface with a period T _C.

The time delay is measured, which determines the first rough value of the range D of the ^GRUB according to (2), by searching and preliminary detecting the signal reflected from the surface of the earth in the time interval t of the _ZAP corresponding to the time interval from the minimum value of the determined range D _MIN to the maximum value of the determined range D _MAX selects decomposed into N pulses are partial time intervals of equal duration Δt (each of which corresponds to a selectable pulse) on cat ing break interval defined range ΔR.

The search for a signal reflected from the earth’s surface is carried out by accumulating the reflected signals in N selective pulses of duration Δt.

To maintain a high probability of correct detection of the reflected signal at a given probability of false alarm, the accumulation threshold k is set.

A search for the reflected signal is carried out simultaneously for all selection pulses to reduce the time of detection (search) of the signal. The reflected signal is considered to be detected when the accumulation threshold k is exceeded in one of the selecting pulses of duration Δt.

между моментом излучения зондирующего сигнала и фронтом селектирующего импульса, в котором произошло обнаружение отраженного сигнала U_ОТР. Значение

определяет первое грубое значение дальности D^ГРУБ1 по (2).Perform the first rough range determination by measuring the time interval

between the moment of radiation of the probing signal and the front of the selection pulse, in which the detection of the reflected signal U _OTP occurred. Value

determines the first coarse value of the range D ^GRU1 according to (2).

.The first coarse value of the distance to the surface of the earth is calculated from the measured first coarse value of the time delay

.

The accuracy of obtaining the range D ^GRUB1 is determined by the duration of the selecting pulse Δt.

Thus, stable detection of the reflected signal is made at a high rate of change in the time delay of the reflected signal with low accuracy in determining the range.

Second sub-step

The second rough (preliminary) range determination is carried out in the time interval Δt ₁ corresponding to the reduced search zone, the application of which increases the noise immunity of the method of determining the distance to the earth's surface by reducing the probability of detecting a false signal while reducing the search zone.

The duration of all the selection pulses Δt ₁ is equal to the duration of the three selection pulses Δt: the selection pulse Δt, in which the reflected signal was detected, and two adjacent ones (to the right and to the left of it), into which the reflected signal can shift during the final detection of the reflected signals in the second substep . The center of the time interval Δt ₁ corresponds to the time position of the center of the selecting pulse Δt, in which a preliminary detection of the reflected signal U _OTP occurred.

The final detection of reflected signals is carried out by accumulating the reflected signals in N ₁ selection pulses Δt ₁ , which are partial time intervals of the same duration. Moreover, Δt ₁ = Δt / b, where b≥4, which increases the accuracy of measuring range with the final detection of reflected signals.

The reflected signal is considered to be detected when one of the selective pulses Δt ₁ is exceeded the accumulation threshold k _1. Moreover, k ₁ <k.

между моментом излучения зондирующего сигнала и фронтом селектирующего импульса, в котором произошло обнаружение отраженного сигнала U_ОТР. Значение

определяет второе грубое (предварительное) значение дальности D^ГРУБ2 по формуле (2).Perform a second rough range determination by measuring the time interval

between the moment of radiation of the probing signal and the front of the selection pulse, in which the detection of the reflected signal U _OTP occurred. Value

determines the second coarse (preliminary) value of the range D ^GRUB2 according to the formula (2).

задержки определяется длительностью селектирующего импульса Δt₁, что повышает точность измерения дальности при окончательном обнаружении отраженных сигналов.Time Measurement Accuracy

the delay is determined by the duration of the selecting pulse Δt ₁ , which increases the accuracy of the range measurement with the final detection of reflected signals.

Second phase

_{Set the} reference signal U _OPORN with a delay equal to the duration of the time interval corresponding to the second rough (preliminary) determination of the range.

Reset all accumulated information for all breeding pulses to zero to enable subsequent detections.

Exactly tracking (tracking) the detected signal by discriminating the received reflected U _OTP signal and the reference U _OPOR signal to generate a mismatch signal Δt _P , which is the difference in the time positions of these signals t _OTP and t _OPORH .

The mismatch signal Δt _P acts on the reference signal, changing the delay between the signals U _OTP and U _OPH so that it _tends to zero.

между излученным сигналом и временным положением опорного сигнала U_ОПОРН, осуществляют точное (окончательное) определение дальности D^ТОЧН до поверхности земли по измеренному значению

согласно выражению (2). Точность измерения временной задержки

определяется эквивалентной полосой, при которой происходит процесс дискриминации.Measure the time interval equal to the time delay

between the emitted signal and the temporary position of the reference signal U _OPORN , carry out an accurate (final) determination of the range D ^EXT to the surface of the earth from the measured value

according to the expression (2). Time delay measurement accuracy

is determined by the equivalent band in which the discrimination process occurs.

.The exact (final) value of the distance to the surface of the earth is calculated from the measured exact (final) value of the time delay

.

The third stage is the confirmation of the results of accurate range determination.

Two-stage detection of the reflected signal U _{OTP is} carried out (similar to two-stage detection of the reflected signal at the first stage), performing preliminary detection of the reflected signals and the first rough range determination in the entire range of the determined ranges with low accuracy of determining the range and conducting the final detection of the reflected signals in the second sub-stage and the second rough definition of range in a limited range of determined ranges.

After each detection of the reflected signal is completed, at the third stage, all accumulated information on all the selection pulses is zeroed to enable subsequent detections.

Two-stage detection is carried out cyclically without changing the delay of the reference signal U _OPORN .

Compare with the threshold value ΔD the difference of the results of the second rough and accurate definitions of range. The threshold value ΔD is determined by the duration of two selective pulses Δf ₁ . As a result, the results of accurate range determination are confirmed by cyclic detection of the reflected signal U _OTP , providing, with accurate range determination, probabilistic characteristics (false alarm probabilities and correct detection) obtained by rough range determination.

If the difference in the measurement results of the threshold value ΔD does not exceed, the exact value of the distance D ^EXACT to the earth's surface is calculated.

An exact determined range D ^EXCLUSIVE is given for a specific exact value of the time delay.

If the difference in the measurement results exceeds the threshold value ΔD, the exact range determination is stopped, the reference signal U _{OPORN is set} with a delay equal to the duration of the time interval corresponding to the last second rough determination of the distance to the ground surface t _OPORN , and an accurate measurement of the time interval corresponding to the last position of the selection pulse Δt ₁ , in which the detection occurred, and which is used to calculate the exact value of the distance to the surface of the earth.

Confirm the results of the accurate determination of the time delay and give the exact value of the range.

If there is no confirmation of the results of the exact determination of the range that occurs: when the signal-to-noise ratio is close to unity, when the reflected signal disappears and others, when the exact determination of the range is difficult, the calculated rough range value is given as the result of determining the distance to the earth's surface.

The disadvantage of this method [2] is the lack of reliability - the inability to detect the reflected signal at a high rate of change in the time delay of the reflected signal. The fact that the reflected signal is considered to be detected when one of the selective pulses Δt ₁ is exceeded the accumulation threshold k _1. At a high rate of change in the time delay of the reflected signal, when the earth's surface has large differences in elevation of the relief or a moving object moves at a high vertical speed (including an alternating vertical speed) and so on, the number of accumulated reflected signals in the selection pulses will not be enough to exceed the threshold accumulation k ₁ and the reflected signal will not be detected.

In addition, due to a decrease in the accumulation threshold from k to k ₁ , the probability of correct detection of the reflected signal at a given probability of false alarm decreases.

The technical result of the invention is to increase the reliability of the method of determining the distance to the earth's surface by adapting the duration of the selecting pulses to the rate of change of the time delay of the reflected signal in the second sub-step for detecting the signal of the third stage.

The technical result is achieved by the fact that in the method of determining the distance to the earth’s surface, which consists in emitting a probe signal in the direction of the earth’s surface, searching for and detecting a signal reflected from the earth’s surface, and tracking the detected reflected signal by discriminating the received reflected signal and the reference signal for generating Δt _p error signal representing a difference between the temporal positions of these signals and acting on the reference signal by changing its temporal put s so that the error signal tends to zero Δt _p → 0, measuring a time interval equal to the time delay between the emitted signal and the temporal position of the reference signal, the distance calculating D to the ground surface from the measured value of the time delay, determining distance to the ground surface is carried out in three stage. At the first stage, the search and detection of the reflected signals are carried out in two sub-stages. In the first sub-step, a search and preliminary detection of the reflected signals is carried out by accumulating the reflected signals in N selective pulses Δt, which are partial time intervals of the same duration, into which the interval of the measured range ΔR is divided, and if the accumulation threshold k is exceeded in one of the selecting pulses, and k> 1 . The first coarse (preliminary) range determination is performed by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse in which the reflected signal was detected. Search and detection of the reflected signal is carried out simultaneously for all breeding pulses. The first coarse (preliminary) value of the distance to the earth's surface is calculated from the measured first coarse (preliminary) value of the time delay. In the second sub-step, the final detection of the reflected signals in the time interval t _{ZAD1 of} constant duration is _{carried out} by accumulating the reflected signals in N ₁ selection pulses Δt ₁ , which are partial time intervals of the same duration, with Δt ₁ = Δt / b, where b≥4, and the duration of all of the selection pulses Δt ₁ is equal to the duration of the three selection pulses Δt, with the center of the time interval t _ZAD1 corresponding to the temporary position of the center of the selecting pulse Δt, in which the preliminary detection of the reflected signal and the excess in one of the selecting pulses Δt _{1 the} accumulation threshold k ₁ , and k ₁ <k. A second rough range determination is performed by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse in which the reflection of the signal was detected. Search and detection of the reflected signal is carried out simultaneously for all breeding pulses N ₁ . The second coarse value of the distance to the surface of the earth is calculated from the measured second coarse (preliminary) value of the time delay. At the second stage, the reference signal is set with a delay equal to the duration of the time interval corresponding to the second rough (preliminary) determination of the range. Reset all accumulated information for all breeding pulses. Exact tracking of the detected reflected signal is carried out by discrimination of the received reflected signal and the reference signal to generate a mismatch signal Δt _p and reduce its duration to zero. Measure the time interval equal to the time delay between the emitted signal and the temporary position of the reference signal. The exact value of the distance to the surface of the earth is calculated from the measured exact value of the time delay. At the third stage, the results of accurate range determination are confirmed by detecting the reflected signal in two sub-steps without changing the delay of the reference signal (similar to detecting the reflected signal at the first stage). In the first sub-step, a search and preliminary detection of reflected signals is carried out by accumulating the reflected signals in N selection pulses Δt, which are partial time intervals of the same duration, and exceeding the accumulation threshold k in one of the selection pulses. The first rough range determination is performed by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse in which the reflection of the signal was detected. The first coarse value of the distance to the surface of the earth is calculated from the measured first coarse value of the time delay. In the second sub-step, the final detection of the reflected signal is carried out. A second rough range determination is performed by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse in which the reflection of the signal was detected. The second coarse value of the distance to the surface of the earth is calculated from the measured second coarse value of the time delay. Reset all accumulated information for all breeding pulses. Compare with the threshold value of the difference between the results of coarse and accurate definitions of range. If the difference in the results of determining the range of the threshold ΔD values does not exceed, the exact value of the distance to the surface of the earth is calculated from the measured exact value of the time delay and an exact determined range is output. If the difference in the results of determining the range of the threshold ΔD is exceeded, the values stop the exact determination of the range. Set the reference signal with a delay equal to the duration of the time interval corresponding to the last roughly determined range, and conduct an accurate measurement of the time interval, which is used to calculate the exact value of the distance to the earth's surface. Confirm the results of an accurate measurement of the time delay and give the exact value of the range. If there is no confirmation of the results of the accurate determination of the range, the calculated rough value of the range is given as the result of determining the range to the surface of the earth. In the third stage, the first sub-step of the search and preliminary detection of the reflected signals by accumulating the reflected signals in N selective pulses Δt is carried out once. In the second sub-step of the third stage, the reflected signal is cyclically detected and the second rough value of the distance to the earth's surface is calculated and the difference between the results of the second rough and accurate range determination is compared with the threshold value. The detection of reflected signals is carried out in a limited range of determined ranges corresponding to a time interval t _{ZAD2 of} variable duration using an accumulation threshold k of N ₂ selective pulses Δt (i) of variable duration, the current value of which is changed after each i-th detection of reflected signals as Δt (i ) ≥Δt ₁ + 2Δt _P (i-1), wherein Δt _p (i-1) - the mean value of the error signal between the received echo signal and the reference signal at the exact tracking of the time of the previous detection ind ennyh signals at the third stage and the center of the time interval t _ZAD2 corresponds to i-th cycle of detection of reflected signals temporarily position the selecting pulse center Δt (i), wherein the detection of the reflected signal occurred _OTP U (i-1) -th cycle detecting reflected signals in the second sub-stage of the third stage. After each detection cycle, all accumulated information on all selection pulses is zeroed.

The method of determining the distance to the surface of the earth is as follows.

The determination of the distance to the earth's surface is carried out by determining the parameters of the reflected signal, during which coarse and accurate values of the delay of the reflected signal are measured.

The determination of the distance to the surface of the earth is carried out in three stages.

First step

At the first stage, the rough value of the range is determined. In this case, the time delay is measured, which determines the rough value of the signal range reflected from the surface of the earth - the distance to the surface of the earth according to (2). The first stage is carried out in two sub-stages.

The implementation of the first stage is as follows.

First sub-step

A preliminary detection of the reflected signals is carried out and the first rough range determination is performed in the entire range of ranges with low accuracy of range determination.

Emitting a probe signal _PROBE duration t in the direction of the earth's surface with a period T _C.

The time delay is measured, which determines the first rough value of the range D of the ^GRUB according to (2), by searching and preliminary detecting the signal reflected from the surface of the earth in the time interval t of the _ZAP corresponding to the time interval from the minimum value of the determined range D _MIN to the maximum value of the determined range D _MAX, broken into N selects pulses Δt, the partial time intervals are of equal length (each of which corresponds to a selectable pulse) on cat ing break interval defined range ΔR having the form

The search for a signal reflected from the earth’s surface is performed by accumulating the reflected signals in N selective pulses Δt.

To maintain a high probability of correct detection of the reflected signal and a low probability of false alarm, an accumulation threshold k is set. The larger the value of the accumulation threshold k, the higher the probability of correct detection and the less the probability of false triggering when a reflected signal is detected. The maximum value of the accumulation threshold k is limited by the time during which the signal reflected from the surface of the earth is within the same selection pulse.

A search for the reflected signal is carried out simultaneously for all selection pulses to reduce the time of detection (search) of the signal.

The reflected signal is considered to be detected when the accumulation threshold k is exceeded in one of the selecting pulses Δt.

между моментом излучения зондирующего сигнала и фронтом селектирующего импульса, в котором произошло обнаружение отраженного сигнала U_ОТР. Значение

определяет первое грубое значение дальности D^ГРУБ1 по (2).Perform the first rough range determination by measuring the time interval

between the moment of radiation of the probing signal and the front of the selection pulse, in which the detection of the reflected signal U _OTP occurred. Value

determines the first coarse value of the range D ^GRU1 according to (2).

.The first coarse value of the distance to the surface of the earth is calculated from the measured first coarse value of the time delay

.

The accuracy of obtaining the range D ^GRUB1 is determined by the duration of the selecting pulse Δt.

Second sub-stage The final detection of the reflected signals is carried out and the second coarse (preliminary) range determination is performed in a limited range of the determined ranges with high accuracy of the range determination.

The second rough (preliminary) range determination is carried out in the time interval t _ZAD1 , corresponding to the reduced search zone, the application of which increases the noise immunity of the method of determining the distance to the earth's surface by reducing the probability of detecting a false signal with a reduced search zone.

The time interval t _ZAD1 , divided into N ₁ selection pulses Δt ₁ , is equal to the duration of three selection pulses Δt: the selection pulse Δt, in which the reflected signal was detected, and two adjacent ones (to the right and left of it), into which the reflected signal can shift time of the final detection of reflected signals in the second sub-step. The center of the time interval t _ZAD1 corresponds to the time position of the center of the selecting pulse Δt, in which the preliminary detection of the reflected signal U _OTP occurred.

In this case, the relations

where b≥4,

Moreover, the duration of the partial time interval Δt _{1 is} set such that it corresponds to the duration of the edge t f _OTP reflected signal

The reflected signal is considered to be detected when one of the selective pulses Δt ₁ is exceeded the accumulation threshold k _1. Moreover

The larger the accumulation threshold value k ₁ , the higher the probability of correct detection at a given probability of false response when a reflected signal is detected. However, the larger the value of the accumulation threshold k ₁ , the greater the number of accumulated reflected signals in the selection pulses Δt ₁ must be accumulated to exceed the accumulation threshold in one of the selection pulses to detect the reflected signal. The value of the accumulation threshold k _{1 is} selected based on the given requirements for the probability of correct detection at a given probability of false response when a reflected signal is detected.

между моментом излучения зондирующего сигнала и фронтом селектирующего импульса Δt₁, в котором произошло обнаружение отраженного сигнала U_ОТП. Значение

определяет второе грубое (предварительное) значение дальности D^ГРУБ2 по (2).Perform a second rough (preliminary) range determination by measuring the time interval

between the moment of radiation of the probing signal and the front of the selecting pulse Δt ₁ , in which the reflection of the reflected signal U _OTP occurred. Value

determines the second coarse (preliminary) value of the range D ^GRUB2 according to (2).

задержки определяется длительностью селектирующего импульса Δt₁, величина которого определяется длительностью фронта t_{Ф ОТР} отраженного сигнала, причем Δt₁=Δt/b, согласно (4), что повышает точность измерения дальности при окончательном обнаружении отраженных сигналов.Time Measurement Accuracy

the delay is determined by the duration of the selecting pulse Δt ₁ , the value of which is determined by the duration of the front t _{ОТ OTR of the} reflected signal, and Δt ₁ = Δt / b, according to (4), which increases the accuracy of measuring the range during the final detection of reflected signals.

Second phase

At the second stage, accurate tracking of the detected reflected signal is carried out by discrimination of the received reflected signal and the reference signal to generate a mismatch signal and reduce its duration to zero and calculate the exact (final) value of the distance to the earth's surface.

The implementation of the second stage is as follows.

_{Set the} reference signal U _OPORN with a delay equal to the duration of the time interval corresponding to the second rough (preliminary) determination of the range.

Reset all accumulated information for all breeding pulses to zero to enable subsequent detections.

Exactly monitor (track) the detected signal by discriminating between the received reflected U _OTP signal and the reference U _OPOR signal to generate a signal Δt _P , a mismatch representing the difference in the time positions of these signals t _OTR and t _OPOR

The mismatch signal Δt _P acts on the reference signal, changing the delay between the signals U _OTP and U _OPOR so that it _tends to zero

между излученным сигналом и временным положением опорного сигнала U_ОПОРН, осуществляют точное (окончательное) определение дальности D^ТОЧН до поверхности земли по измеренному значению

согласно (2).Measure the time interval equal to the time delay

between the emitted signal and the temporary position of the reference signal U _OPORN , carry out an accurate (final) determination of the range D ^EXT to the surface of the earth from the measured value

according to (2).

определяется эквивалентной полосой, при которой происходит процесс дискриминации.Time delay measurement accuracy

is determined by the equivalent band in which the discrimination process occurs.

.The exact (final) value of the distance to the surface of the earth is calculated from the measured exact (final) value of the time delay

.

Third stage

At the third stage, the results of accurate range measurement are confirmed by detecting the reflected signal U _OTP and comparing with the threshold value the difference of the measurement results of the second coarse and accurate range measurements.

The third stage is carried out in two sub-stages.

The implementation of the third stage is as follows.

First sub-step

The preliminary detection of the reflected signals is carried out once and the first rough range determination is performed in the entire range of ranges with low accuracy of range determination.

Measure the time delay of the radiated probe signal, which determines the first rough value of the range D of the ^GRUB according to (2), by searching and preliminary detecting the reflected signal U _OTR , in the time interval t _REF , corresponding to the time interval from the minimum value of the determined range D _MIN to the maximum value of the determined range D _MAX, broken into N selects pulses are partial time intervals of equal duration Δt (each of which corresponds to selektiruyusch st pulse), which divide the interval defined range ΔR.

A search for the reflected signal is carried out by accumulating the reflected signals in N selective pulses simultaneously for all selective pulses.

The reflected signal is considered to be detected when the accumulation threshold k is exceeded in one of the selecting pulses Δt.

между моментом излучения зондирующего сигнала и фронтом селектирующего импульса, в котором произошло обнаружение отраженного сигнала U_ОТП. Значение

определяет первое грубое значение дальности D^ГРУБ1 по (2).Perform the first rough range determination by measuring the time interval

between the moment of radiation of the probe signal and the front of the selection pulse, in which the detection of the reflected signal U _OTP occurred. Value

determines the first coarse value of the range D ^GRU1 according to (2).

.The first coarse value of the distance to the surface of the earth is calculated from the measured first coarse value of the time delay

.

Second sub-step

In the second sub-step, the reflected signal is detected cyclically, the second rough value of the distance to the earth’s surface is calculated, and the difference between the results of the second rough and accurate range determination is compared with the threshold value.

After each detection of the reflected signal is completed, at the third stage, all accumulated information on all the selection pulses is zeroed to enable subsequent detections.

The detection of reflected signals is carried out in a limited range of determined ranges with the adaptation of the duration of the selecting pulses to the rate of change of the surface topography.

The detection of the reflected signal U _{OTP is} carried out in the time interval t _ZAD2 .

The time interval t _ZAD2 , divided into N ₂ selection pulses Δt (i), is initially equal to the duration of three selection pulses Δt: the selection pulse Δt, in which the reflected signal was detected, and two neighboring ones (to the right and to the left of it), in which the reflected signal during the detection of reflected signals in the second substep. The center of the time interval t _ZAD2 initially corresponds to the time position of the center of the selecting pulse Δt, in which the reflected signal U _OTP was detected in the first sub-stage of the third stage.

The value of the duration of the selecting pulses Δt (i) is determined as

where Δt _p (i-1) is the average value of the error signal between the received reflected signal and the reference signal during accurate tracking during the previous detection of reflected signals in the third stage (initially during the detection of reflected signals in the first sub-stage of the third stage).

The reflected signal is considered to be detected when the accumulation threshold k is exceeded in one of the N ₂ selective pulses Δt (i).

между моментом излучения зондирующего сигнала и фронтом селектирующего импульса Δt(i), в котором произошло обнаружение отраженного сигнала U_ОТР. Значение

определяет второе грубое значение дальности D^ГРУБ2 по (2).Perform a second rough range determination by measuring the time interval

between the moment of radiation of the probing signal and the front of the selecting pulse Δt (i), in which the reflection of the reflected signal U _OTP was detected. Value

determines the second coarse value of the range D ^GRUB2 according to (2).

During the second and subsequent cycles of the second sub-stage of the third stage, the detection of reflected signals is also performed in N ₂ selective pulses Δt (i).

As a result, the center of the time interval t _ZAD2 corresponds in the ith cycle of detection of reflected signals to the temporary position of the center of the selecting pulse Δt (i), in which the reflected signal U _OTR was detected in the (i-1) -th cycle of detection of reflected signals in the second sub-stage of the third stage, and after each detection cycle, zero all accumulated information for all breeding pulses.

Thus, the current value of the duration of the selecting pulses Δt (i) is changed after each i-th detection of the reflected signals, clarifying the average value of the signal Δt _p (i) of the mismatch between the received reflected signal and the reference signal during accurate tracking during the previous detection of reflected signals on third stage.

The time interval t _ZAD2 in the second sub-stage of the third stage will be of variable duration: the number of selection pulses N _{2 is} constant, and the current value of the duration of the selection pulses Δt (i) can change after each detection of reflected signals.

Cyclic detection in the third stage is carried out without changing the delay of the reference signal U _OPORN .

In each cycle of the second sub-step of the third stage, the difference between the results of the second coarse and accurate range determination is compared with the threshold value ΔD. The threshold value ΔD is determined by the duration of two selective pulses Δt (i). As a result, the results of accurate range determination are confirmed by cyclic detection of the reflected signal U _OTP , providing, with accurate range determination, probabilistic characteristics (false alarm probabilities and correct detection) obtained by rough range determination.

If the difference in the measurement results of the threshold value ΔD does not exceed, an exact, determined range D is ^EXACT for a certain exact (final) time delay value.

If the difference in the measurement results exceeds the threshold value ΔD, the exact range determination is stopped, the reference signal U _{OPORN is set} with a delay equal to the duration of the time interval corresponding to the last second rough determination of the distance to the earth's surface t _OPORN, and an accurate measurement of the time interval corresponding to the last position of the selection pulse Δt (i) in which the detection occurred, and which is used to calculate the exact value of the distance to the surface of the earth.

Confirm the results of the accurate determination of the time delay and give the exact value of the range.

If there is no confirmation of the results of the exact determination of the range that occurs: when the signal-to-noise ratio is close to unity, when the reflected signal disappears and others, when the exact determination of the range is difficult, the calculated second rough range value is given as the result of determining the distance to the earth's surface.

We indicate the features of this method.

In expression (10), before Δt _p (f), coefficient 2 is selected, since the error signal is determined by the center of the reflected signal U _OTP (this does not take into account the slice of the reflected signal), and coefficient 2 expands the selection pulse Δt (i) precisely to take into account the slice of the reflected signal.

Based on (10) we have the following. In the first step of discrimination for i = 1, we have Δt (1) = Δt ₁ . For i = 2, we obtain Δt (2) = Δt ₁ + 2Δt (1). For i = 3, there will be Δt (3) = Δt ₁ + 2Δt _p (2) and so on. Moreover, Δt _p (1) ≠ Δt _p (2), since each measure will have its own value Δt _p (i), therefore Δt _p (i) ≠ Δt _p (i + 1).

The current value Δt (i) in (10) consists of a constant equal to Δt ₁ and the variable part determined by the current value Δt _p (i).

At a low rate of change in the time delay of the reflected signal — with a smooth change in the terrain (small differences in elevation of the relief) and the absence of a vertical speed of movement of a moving object, when its rate of change is small, the duration Δt (i) is relatively small, and the change in the profile of the relief can be tracked even a small value of the partial time interval Δt (i).

At a high rate of change in the time delay of the reflected signal — with a sharp change in the terrain (large differences in elevation of elevation) and a significant vertical velocity of the moving object, its rate of change is large and the duration Δt (i) increases, since changes in the signal Δt _p (i), the mismatch track only with a long partial time interval Δt (i).

When determining the range, an adaptive change in the partial time intervals of duration Δt (i) occurs when the reflected signals are accumulated in N ₂ selective pulses. Moreover, the detection of the reflected signal in the second sub-stage of the third stage is carried out at an accumulation threshold k corresponding to the accumulation threshold in the first sub-stage of the third stage, which does not reduce the probability of correct detection of the reflected signal at a given probability of false alarm in the second sub-stage of the third stage (in the second sub-stage of the first stage of - due to a decrease in the accumulation threshold from k to k _1, there was a decrease in the probability of correct detection of the reflected signal at a given probability of false alarm).

Thus, the method of determining the distance to the earth’s surface by detecting the reflected signal with adaptation of the partial time intervals Δt (i) to the rate of change of the time delay of the reflected signal in the second sub-step of the third stage provides high reliability of detection of the reflected signal at a high rate of change of the time delay of the reflected the signal from the earth’s surface, which has large differences in elevation of the relief, a high vertical velocity of a moving object (in t number and alternating vertical speed) and other possible factors affecting the signal duration Δt _p (i) of the mismatch.

Confirmation of the results of accurate range determination occurs by cyclic detection of the reflected signal, which provides accurate characteristics for determining the range of probabilistic characteristics (false alarm probabilities and correct detection) obtained by rough range determination.

In this case, reliable determination of the distance to the earth's surface at a high rate of change in the time delay of the reflected signal occurs with high accuracy in determining the range and with a high probability of correct detection at a given probability of false alarm.

The detection of the reflected signal occurs in a limited range of determined ranges, which increases the noise immunity of the detection.

It is characteristic that due to the accumulation operation, the detection of reflected signals when determining the range can occur when the signal-to-noise ratio is close to unity.

Thus, the considered method for determining the distance to the surface of the earth has a number of significant advantages over the prototype and analogue.

LITERATURE

1. Handbook of radar / Ed. M. Skolnik. - M .: Owls. Radio, 1976.- T.1 - 456 S. (S.176-197, 309-310).

2. Patent No. 2436116, IPC G01S 13/08 (2006.01). The method of determining the distance to the surface of the earth / Khrustalev A.A., Koltsov Yu.V. // Inventions. Useful models. - 2011. - Publ. 12/10/2011. - Bull. No. 34 (prototype).

Claims (1)

The method of determining the distance to the earth’s surface, which consists in emitting a probe signal in the direction of the earth’s surface, searching for and detecting a signal reflected from the earth’s surface, and tracking the detected reflected signal by discriminating the received reflected signal and the reference signal to generate a signal Δt _p , a mismatch representing is the difference in the temporal positions of these signals and acting on the reference signal, changing its temporal position so that the mismatch signal zero Δt _p → 0, measuring the time interval equal to the time delay between the emitted signal and the time position of the reference signal, calculating the distance D to the earth's surface from the measured value of the time delay, and determining the distance to the earth's surface is carried out in three stages, at the first stage in two sub-steps, search and detection of reflected signals are performed, in the first sub-step, search and preliminary detection of reflected signals is carried out by accumulating reflected signals in N pulse selectors ax Δt, which are partial time intervals of the same duration, into which the interval of the measured range ΔR is divided, and the excess of the accumulation threshold k in one of the selecting pulses, and k> 1, performs the first rough (preliminary) determination of the range by measuring the time delay between the moment of probe radiation the signal and the front of the selection pulse in which the detection of the reflected signal occurred, and the search and detection of the reflected signal is carried out simultaneously for all the selecting impulses For pulses, the first coarse (preliminary) value of the distance to the earth’s surface is calculated from the measured first coarse (preliminary) value of the time delay, the second sub-step performs the final detection of reflected signals in the time interval t _{ZAD1 of} constant duration by accumulating reflected signals in N ₁ selection pulses Δt ₁ , which are partial time intervals of the same duration, with Δt ₁ = Δt / b, where b≥4, and the duration of all selection pulses Δt ₁ is equal to the duration of three seleks tiruyuschih pulses Δt, centered timeslot t _ZAD1 corresponding time position of the selecting pulse center Δt, which was pre-detection of the reflected signal, and the excess of one of the selecting pulse Δt ₁ threshold accumulation k _1, where k ₁ <k, operate the second rough determining the range by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse, in which the detection of the reflected signal occurred, and the search and detection is reflected signal is carried out simultaneously for all the selection pulses N ₁ , the second rough value of the distance to the earth’s surface is calculated from the measured second coarse (preliminary) value of the time delay, at the second stage, the reference signal is set with a delay equal to the duration of the time interval corresponding to the second coarse (preliminary) range determination, zero all accumulated information for all breeding pulses, accurately track the detected reflected signal by discriminating ation of the received reflected signal and a reference signal to generate Δt _p mismatch and reducing signal its length to zero, the measured time interval equal to the time delay between the emitted signal and the temporal position of the reference signal, calculating an accurate value of the range to the ground surface from the measured exact value of time delay, at the third stage, the results of accurate range determination are confirmed by detecting the reflected signal in two sub-stages without changing the delay of the reference drove, and in the first sub-step, a search and preliminary detection of the reflected signals is carried out by accumulating the reflected signals in N selection pulses Δt, which are partial time intervals of the same duration, and exceeding the accumulation threshold k in one of the selection pulses, perform the first rough range determination by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse, in which the detection of the reflected signal occurred, first e coarse value of the distance to the earth’s surface according to the measured first coarse value of the time delay, in the second sub-step the final detection of the reflected signal is performed, the second coarse determination of the distance is made by measuring the time delay between the moment of radiation of the probe signal and the front of the selection pulse in which the reflected signal was detected, calculate the second rough value of the distance to the surface of the earth from the measured second rough value of the time delay, zeroing they collect all the accumulated information for all the selection pulses, compare with the threshold value of the difference between the results of coarse and accurate range determination, if the difference between the results of determining the range of the threshold ΔD values does not exceed, calculate the exact value of the distance to the earth's surface from the measured exact value of the time delay, give the exact determined range, at exceeding the difference in the results of determining the range of the threshold ΔD values stop the accurate determination of the range, set the reference signal l with a delay equal to the duration of the time interval corresponding to the last roughly determined range, and carry out an accurate measurement of the time interval, which is used to calculate the exact value of the distance to the surface of the earth, confirm the results of the exact measurement of the time delay and give the exact value of the range, in the absence of confirmation of the results accurate range determination give the calculated rough value of the range as a result of determining the distance to the surface of ml, characterized in that in the third stage, the first sub-step of searching and preliminary detection of reflected signals by accumulating the reflected signals in N selection pulses Δt is performed once, and in the second sub-step of the third stage, the reflected signal is cyclically detected, the second rough value of the distance to the earth’s surface is calculated, and comparison with the threshold value of the difference of the results of the second rough and accurate definitions of range, and the detection of reflected signals is carried out in a limited range the range of determined ranges corresponding to the time interval t _{ZAD2 of} variable duration using the accumulation threshold k of N ₂ selective pulses Δt (i) of variable duration, the current value of which is changed after each i-th detection of reflected signals as Δt (i) ≥Δt ₁ + 2Δt _P (i-1), where Δt _p (i-1) is the average value of the error signal between the received reflected signal and the reference signal during accurate tracking during the previous detection of reflected signals in the third stage, and the center is the time interval and t _ZAD2 corresponds in the i-th detection cycle of reflected signals to the temporary position of the center of the selecting pulse Δt (i), in which the reflected signal U _OTP was detected in the (i-1) -th detection cycle of reflected signals in the second substep of the third stage, and after of each detection cycle, all accumulated information for all selection impulses is zeroed.