RU1840913C - Pulse radar - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: pulse radar includes a receiver and a transmitter, two threshold circuits, a range-measuring device, a constant unit, a reference pulse generator, an AND element, a counter, a multiplier, an adder, a device for measuring the duration of the leading edge of the probing pulse with memory, connected to each other in a certain manner.

EFFECT: faster determination of target coordinates.

3 dwg

Description

The invention relates to the field of radar and radio navigation and can be used in active radar systems.

Known active radar systems designed to determine the coordinates of moving and stationary objects. Pulse radar equipment includes an antenna receiving and transmitting device, an antenna switch, a transmitter, a receiver, a synchronizer, a threshold circuit, a range measuring device, and a block of constant constants. The position r / l of the target (mobile or stationary) in relation to the radar is determined by:

three coordinates - in space,

two coordinates - on the plane.

One of the coordinates is the range to r / l of the target.

The measurement of the range to the radar target is made by measuring the time interval between the sending of the probe pulse and the arrival of the reflected pulse.

This system has a significant drawback:

- deterioration in the accuracy of determining the range to the target due to changes in the duration of the leading edge of the pulse as it passes through the medium and the receiver.

The deterioration in the accuracy of determining the range occurs due to the fact that the distance to the target is determined by the leading edge of the reflected pulse (at some specific level).

Changing the duration of the leading edge of the reflected pulse (in the medium, in the receiver with a matched band) leads to a significant error in determining the range.

Errors especially increase when using wide probing pulses without intrapulse modulation.

The aim of the invention is to remedy these disadvantages; increasing the accuracy of determining the range when changing the duration of the leading edge of the pulse.

This goal is achieved by the fact that in a known pulsed radar containing an antenna receiving and transmitting device, an antenna switch, a transmitter, a receiver, a synchronizer, a threshold circuit, a range measuring device, a unit of constant constants, a second threshold circuit, a reference pulse generator, a circuit are additionally included And ", counter, multiplier, adder, power coupler, device for measuring the leading edge of the probe pulse, memory device for the leading edge of the probe th pulse.

The input of the second threshold circuit is connected to the input of the first threshold circuit, the outputs of the threshold circuits and the reference pulse generator are connected to the outputs of the circuit "I", the output of which is connected via a counter to the multiplier. The outputs of the range measuring device, multiplier, constant constants block, and the leading edge code of the probe pulse are connected to the adder. The transmitter is connected through a power coupler to a measuring circuit of the leading edge of the probe pulse, which is connected to a memory device of the leading edge code of the probe pulse.

In this case, the duration of the leading edge of the pulse normalized by the amplitude of the pulse reflected from the target is measured, then the leading edge of the reflected pulse is corrected by the duration of the leading edge of the probe pulse and the true distance to the target is determined.

The duration of the front reflected pulse is determined by the operation of two threshold circuits.

When the first threshold circuit is triggered, the "I" circuit opens and through it from the reference pulse generator quartz signals pass to the counter. At the moment the second threshold circuit is triggered, the AND circuit closes. Multiplying the multiplier code in the counter by a constant correction, we get the code value of the leading edge of the reflected pulse.

The duration code of the leading edge of the probe pulse is determined as follows. The probe pulse is fed through a power coupler to the measuring circuit of the leading edge of the probe pulse. The resulting leading edge code of the probe pulse is recorded in the memory device of the leading edge code of the probe pulse. From the code of the leading edge of the reflected pulse, it is necessary to subtract the code of the leading edge of the probe pulse. The found correction, equal to the difference between the leading edge codes of the pulse reflected from the target and the probe pulse, must be subtracted from the range code in the adder. In addition, in the adder, a code equal to the value of the constant delay in the circuits of the receiver and transmitter of the pulsed radar is subtracted from the adjusted value of the range code.

The block diagram of a pulsed radar is shown in figure 1, where indicated:

1 - antenna receiving and transmitting device;

2 - antenna switch;

3 - transmitter;

4 - receiver;

5 - power coupler;

6 - a device for measuring the duration of the leading edge of the probe pulse;

7 - memory device code leading edge of the probe pulse;

8 - device for measuring range;

9 - synchronizer;

10 - device for measuring the duration of the leading edge of the reflected pulse;

11 - block of constant constants;

12 - adder;

13, 14 - threshold circuit;

15 - reference pulse generator;

16 - scheme "And",

17 - counter;

18 - multiplier device;

19 - receiver output;

20 - transmitter output;

21 - input of the receiver;

22 - input device range measurement;

23 - input device range measurement;

24 - adder input;

25 - adder input;

26 - adder input;

27 - adder input;

28 - adder output.

The timing diagram of the operation of a pulsed radar is shown in figure 2 ((Fig. 2A) is an ideal rectangular pulse; Fig. 2b) is a real rectangular pulse), where are indicated:

19 - reflected pulse from the target at the output of the receiver;

20 - probe pulse at the output of the transmitter;

21 - reflected pulse at the input of the receiver;

22 - start pulse of a ranging device;

- время распространения электромагнитной энергии от передатчика до цели и обратно; $$T_{\mathrm{one}}=\frac{2D}{c}$$

- the propagation time of electromagnetic energy from the transmitter to the target and vice versa;

D is the distance between the pulse locator and r / l target;

c is the propagation velocity of electromagnetic energy;

- постоянная задержка в передатчике импульсного локатора; $$\Delta t_n^{\text{'}\text{'}}$$

- constant delay in the transmitter of the pulse locator;

- постоянная задержка в приемнике импульсного локатора; $$\Delta t_n^{\text{'}\text{'}\text{'}\text{'}}$$

- constant delay in the receiver of the pulse locator;

T _pov. - the pulse repetition period of the transmitter;

ΔT ₁ is the duration of the leading edge of the probe pulse at the output of the transmitter;

- длительность переднего фронта отраженного импульса на входе приемника; $$\Delta {\dot{T}}_2$$

- the duration of the leading edge of the reflected pulse at the input of the receiver;

ΔT ₂ - the duration of the leading edge of the reflected pulse at the output of the receiver:

The probe pulse at the output of the transmitter and the reflected pulse at the output of the receiver are shown in figure 3, where indicated:

OB ₃ D ₃ D ₁ - reflected pulse at the output of the receiver;

OA ₃ C ₃ C ₁ - probe pulse at the output of the transmitter;

d ₁ , d ₂ - known levels in amplitude;

Δt ₁ is the duration of the leading edge of the probe pulse between two known levels in amplitude;

Δt ₂ is the duration of the leading edge of the reflected pulse between two known levels in amplitude;

ΔТ ₁ - the duration of the leading edge of the probe pulse between the reference point and level d ₂ , which determines the time of arrival of the signal;

ΔТ ₂ - the duration of the leading edge of the reflected pulse between the origin and level d ₂ , which determines the time of arrival of the signal;

ΔT is the delay between the reflected pulse at the output of the receiver and the probe pulse at a given level d ₂ in amplitude.

The proposed pulsed radar consists of an antenna receiving and transmitting device 1, an antenna switch 2, a transmitter 3, a receiver 4, a power coupler 5, a device for measuring the duration of the leading edge of the probe pulse 6, a memory device for the code of the leading edge of the probe pulse 7, a measuring device for range 8, synchronizer 9, the measuring device of the leading edge of the reflected pulse 10, a block of constant constants 11, the adder 12.

The measuring device of the leading edge of the reflected pulse 10 consists of threshold circuits 13, 14, the generator of the reference pulses 15, the circuit "And" 16, the counter 17, the multiplier 18.

Antenna receiving and transmitting device 1 through the antenna switch 2 is connected to the transmitter 3 and the receiver 4.

The transmitter 3 through a power coupler 5 is connected to a device for measuring the duration of the leading edge of the probe pulse 6, the output of which is connected to a memory device for the code of the leading edge of the probe pulse 7.

The transmitter 3, the receiver 4, the measuring device range 8, connected to the synchronizer 9.

The output of the receiver 4 is connected to the threshold circuits 13, 14 of the device for measuring the duration of the leading edge of the reflected pulse 10. The reference pulse generator 15 and the outputs of the threshold circuits 13, 14 are connected to the inputs of the circuit "And" 16.

The output of the threshold circuit 14 is connected to a range measuring device 8.

The output of the circuit "And" 16 through the counter 17 is connected to the multiplying device 18.

The outputs of the multiplying device 18 of the device for measuring the duration of the leading edge of the reflected pulse 10, the memory device for the code for the duration of the leading edge of the probe pulse 7, the device for measuring range 8, the constant constant block are connected to the adder 12.

The change in the duration of the leading edge of the pulse at the output of the receiver is corrected by a correction ΔT equal to the difference between the leading edges of the pulse at the output of the receiver and the probe pulse. To do this, we compare the pulses at the output of the receiver and the probe according to FIG. 2b). Why combine the origin of these pulses.

и $$(t_n^{\text{'}}+t_n^{\text{'}\text{'}})$$

.In this case, constant values are excluded from consideration $$T_{\mathrm{one}}=\frac{2D}{c}$$

and $$(t_n^{\text{'}\text{'}}+t_n^{\text{'}\text{'}\text{'}\text{'}})$$

.

Figure 3, which shows the pulse at the output of the receiver and the probe pulse of the transmitter, found the values that must be determined to obtain the correction ΔT.

From the similarity of triangles OA ₂ M and A ₁ A ₂ K (see figure 3) we find

$$\frac{A_2{K}_{\mathrm{one}}}{A_2{M}_{\mathrm{one}}}=\frac{A_{\mathrm{one}}{K}_{\mathrm{one}}}{O{M}_{\mathrm{one}}}\left(\mathrm{one}\right)$$

From figure 3 we determine

A ₂ K ₁ = d ₂ -d ₁ ;

A ₂ M ₁ = d ₂ ;

A ₁ K ₁ = Δt ₁ ;

OM ₁ = ΔT ₁ .

Substituting the found values in expression (1), we obtain

; $$\frac{d_2-d_{\mathrm{one}}}{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">d</figure-callout>}}_2}=\frac{\Delta t_{\mathrm{one}}}{\Delta T_{\mathrm{one}}}$$

;

Where from

; $$\Delta T_{\mathrm{one}}=\frac{d_2}{d_2-d_{\mathrm{one}}}\Delta t_{\mathrm{one}}=K\Delta t_{\mathrm{one}}$$

;

From the similarity of the triangles OB ₂ M ₂ and B ₁ B ₂ K ₂ we find

$$\frac{B_2{K}_2}{B_2{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">M</figure-callout>}}_2}=\frac{B_{\mathrm{one}}{K}_2}{O{M}_2}\left(2\right)$$

From figure 3 we determine

B ₂ K ₂ = d ₂ -d ₁ ;

B ₂ M ₂ = d ₂ ;

B ₁ K ₂ = Δt ₂ ;

OM ₂ = ΔT ₂ .

Substituting the found values in expression (2), we obtain:

, откуда $$\Delta T_2=\frac{d_2}{d_2-d_1}\Delta t_2=K\Delta t_2$$

. $$\frac{d_2-d_{\mathrm{one}}}{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">d</figure-callout>}}_2}=\frac{\mathrm{<figure-callout\; id="2"\; label="\Delta \; t"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">\Delta \; </figure-callout>}{t}_{}{}_2}{\mathrm{<figure-callout\; id="2"\; label="\Delta \; T"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">\Delta \; </figure-callout>}{T}_{}{}_2}$$

from where $$\mathrm{<figure-callout\; id="2"\; label="\Delta \; T"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">\Delta \; </figure-callout>}{T}_{}{}_2=\frac{d_2}{d_2-d_{\mathrm{one}}}\mathrm{<figure-callout\; id="2"\; label="\Delta \; t"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">\Delta \; </figure-callout>}{t}_{}{}_2=\mathrm{<figure-callout\; id="2"\; label="K\; \Delta \; t"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">K\; </figure-callout>}\Delta t_{}{}_2$$

.

The delay between the pulse at the output of the receiver and the probe pulse at a given level d ₂ is determined by the expression

$$\Delta T=\Delta T_2-\Delta T_{\mathrm{one}}=K(\Delta t_2-\Delta t_{\mathrm{one}})\left(3\right)$$

, который равен константе и определяется двумя уровнями сигнала d₁ и d₂ и измерять интервалы времени Δt₁ и Δt₂. Δt₁, Δt₂ - интервалы времени между точками на переднем фронте зондирующего импульса и импульса на выходе приемника, когда их амплитуды достигают определенных значений (уровни d₁ и d₂).Thus, to calculate the correction ΔT, it is necessary to know the correction coefficient $$K=\frac{d_2}{d_2-d_{\mathrm{one}}}$$

, which is constant and is determined by two signal levels d ₁ and d ₂ and measure the time intervals Δt ₁ and Δt ₂ . Δt ₁ , Δt ₂ - time intervals between points on the leading edge of the probe pulse and the pulse at the output of the receiver when their amplitudes reach certain values (levels d ₁ and d ₂ ).

The correction value ΔT ₂ = ΔT ₂ -ΔT ₁ , equal to the change in the duration of the leading edge of the pulse, must be subtracted from the measured range value, which corresponds to the time interval between the sending of the probe pulse and the arrival of the pulse reflected from the target.

The measurement of the range to the target by a pulse locator is as follows.

The start pulse from the synchronizer is fed to the input of the transmitter 3 and input 22 of the range measuring device 8.

The probe pulse from the output 20 of the transmitter 3 through the antenna switch 2 is fed to the antenna of the receiving-transmitting device 1 and is emitted. The pulse reflected from the target through the antenna of the receiving and transmitting device 1 and the antenna switch 2 is fed to the input 21 of the receiver 4.

The pulse from the output 19 of the receiver 4 is fed to the inputs of the threshold circuits 13, 14 of the device for determining the duration of the leading edge of the reflected pulse 10. The signal from the output of the threshold circuit 14 corresponding to the moment of arrival of the reflected pulse is fed to the input 23 of the range measuring device 8, which determines the distance by measuring the time interval between the radiation of the probe pulse and the arrival of the reflected pulse.

The range code from the output of the range measuring device 8 is fed to input 24 of the adder 12.

, из этого значения кода вычитается поправка, формируемая блоком постоянных констант 11 и поступающая на вход 25 сумматора 12.To eliminate the constant correction ΔD proportional to the constant delay $$(\Delta t_n^{\text{'}\text{'}}+\Delta t_n^{\text{'}\text{'}\text{'}\text{'}})$$

, from this code value is subtracted the correction generated by the block of constant constants 11 and fed to input 25 of adder 12.

After that, in adder 12, the correction ΔT = ΔT ₂ -ΔT ₁ is subtracted from the resulting code, caused by a change in the duration of the leading edge of the reflected pulse (when passing through the medium and the receiver).

The value of ΔT ₁ is determined as follows.

The signal from the output of the transmitter 3 through the power coupler 5 is fed to the device for measuring the duration of the leading edge of the probe pulse 6 and the measured code value is entered into the memory device of the code for the duration of the leading edge of the probe pulse 7. From the device 7, the code value ΔT ₁ is input to the adder 26.

The value ΔT ₂ enters the adder 12 from the device for determining the duration of the leading edge of the reflected pulse and is determined as follows.

When the first threshold circuit 13 is triggered, through the "AND" 16 circuit, quartz signals are received at the input of the counter 17 from the reference pulse generator 15. When the second threshold circuit 14 is triggered, the AND circuit 16 closes.

Due to the fact that the input of the threshold circuits 13, 14 receives a signal normalized in amplitude from the output of the receiver, the duration of the leading edge of the pulse Δt ₂ between the levels d ₁ and d _{2 is} determined from the time interval between the triggering times of the two threshold circuits 13, 14, the measured value Δt ₂ goes to the input of the multiplier 18 and from its output the value of the leading edge of the reflected pulse at the output of the receiver ΔT ₂ goes to the input 27 of the adder 12. From the output 28 of the adder 12, the true value of the range code D _ist .

The time interval between the formation of the trigger pulse of the transmitter and the arrival of the reflected pulse from the output of the receiver to the range measuring device is determined by the expression

$$T_{\Sigma }=T_{\mathrm{one}}+(\Delta t_n^{\text{'}\text{'}}+\Delta t_n^{\text{'}\text{'}\text{'}\text{'}})+\Delta T\left(\mathrm{four}\right)$$

T ₁ is the time between the radiation of the probe pulse and the arrival of the pulse reflected from the target;

- постоянная задержка в цепях передатчика; $$\Delta t_n^{\text{'}\text{'}}$$

- constant delay in the transmitter circuits;

- постоянная задержка в цепях приемника; $$\Delta t_n^{\text{'}\text{'}\text{'}\text{'}}$$

- constant delay in the receiver circuits;

ΔT is the delay between the pulse at the output of the receiver and the probe pulse

ΔT = ΔT ₂ -ΔT ₁

where ΔT ₁ is the duration of the leading edge of the probe pulse;

ΔT ₂ - the duration of the leading edge of the reflected pulse at the output of the receiver.

Expression (4) can be converted to expression

$$T_{\Sigma }=T_{\mathrm{one}}+(t_n^{\text{'}\text{'}}+t_n^{\text{'}\text{'}\text{'}\text{'}})+(\Delta T_2-\Delta T_{\mathrm{one}})\left(5\right)$$

The range to r / l of the target is determined by the expression

$$D=\frac{c{T}_{\mathrm{<figure-callout\; id="2"\; label="\Sigma "\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">\Sigma </figure-callout>}}}{2}=\frac{2[T_{\mathrm{one}}+(t_n^{\text{'}\text{'}}+t_n^{\text{'}\text{'}\text{'}\text{'}})+(\Delta T_2-\Delta T_{\mathrm{one}})]}{2}\left(6\right)$$

The true range to r / l of the target is determined by the expression

$$D_{\mathrm{and}\mathrm{from}t}=\frac{c{T}_{\Sigma }{}_{{}_{\mathrm{and}\mathrm{from}\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">t</figure-callout>}}}}{2},\left(7\right)$$

- истинное время распространения электромагнитной энергии от локатора до р/л цели и обратно;Where $$T_{{\Sigma }_{\mathrm{and}\mathrm{from}t}}$$

- the true propagation time of electromagnetic energy from the locator to the target r / l and vice versa;

$$\begin{array}{l}{T}_{{\Sigma }_{\mathrm{and}\mathrm{from}t}}=T_{\Sigma }-(t_n^{\text{'}\text{'}}+t_n^{\text{'}\text{'}\text{'}\text{'}})-(\Delta T_2-\Delta T_{\mathrm{one}})=\\ =[T_{\mathrm{one}}+(t_n^{\text{'}\text{'}}+t_n^{\text{'}\text{'}\text{'}\text{'}})+(\Delta T_2-\Delta T_{\mathrm{one}})]-(t_n^{\text{'}\text{'}}+t_n^{\text{'}\text{'}\text{'}\text{'}})-(\Delta T_2-\Delta T_{\mathrm{one}})=T_{\mathrm{one}}\left(8\right)\end{array}$$

из уравнения (8) в уравнение (7), получимSubstituting the value $$T_{{\Sigma }_{\mathrm{and}\mathrm{from}t}}$$

from equation (8) to equation (7), we obtain

$$D_{\mathrm{and}\mathrm{from}t}=\frac{c{T}_{\mathrm{one}}}{2}\left(9\right)$$

those. the distance from the pulsed locator to the target r / l is determined only by the propagation time of electromagnetic energy and does not depend on the change in the duration of the leading edge of the probe pulse and the reflected pulse when it passes through the medium and the receiver.

Thus, the accuracy of measuring the range on the leading edge does not depend on the change in the duration of the leading edge of the pulse.

The introduction of schemes for determining the duration of the leading edge of the reflected and probing pulses makes it possible to increase the accuracy of determining the distance to the target when changing the duration of the leading edge of the pulse when passing through the medium and the receiver. The use of correction of the duration of the leading edge of the pulse makes it possible to increase the accuracy of measuring the time interval proportional to the distance by an amount equal to the change in the duration of the leading edge of the pulse. In known receivers, the instability of the passband is 10-20%, which is equivalent to a 10-20% change in the duration of the leading edge of the pulse when passing through a receiver whose passband is consistent with the pulse duration. This construction of a pulsed radar is most appropriate when using long pulses without intrapulse modulation.

Claims (1)

A pulsed radar containing a receiving and transmitting device, a threshold circuit, a range measuring device, a constant constant unit, while the input of the threshold circuit is connected to the output of the receiving device, and the output is connected to the input of the range measuring device, characterized in that, in order to increase the accuracy of determination range to the target, a second threshold circuit, a reference pulse generator, an And element, a counter, a multiplier, an adder, a device for measuring the duration of the leading edge of the probe pulse are introduced into it ca with memory, while the input of the measuring device of the leading edge of the probe pulse with memory is connected to the output of the transmitting device, and the output is connected to the adder, the inputs of which are also connected to a constant constants block, the outputs of the multiplying device and range measuring device, the input of the second threshold circuit is connected with the output of the receiving device, and the output is connected to one of the inputs of the And element, the second input of which is connected to the output of the first threshold circuit, and the third input is connected to the output of the support generator pulses, the input of the counter is connected to the output of the AND element, and the output is connected to the input of the multiplying device.

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