RU2519911C2 - Recirculating radar altimeter - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to radar engineering and can be used at development of on-board flight altitude measuring devices of aircrafts. A recirculating radar altimeter includes a start-pulse oscillator, a clock-pulse oscillator, two AND elements, two OR elements, three delay lines, a transmitter, a directional coupler, an isolating unit, an antenna unit, an amplitude detector, an UHF switch, a trigger, a receiver, a tracking unit and an altitude calculation unit, which are connected to each other in a certain way.

EFFECT: simplifying radar altimeter design and improving its reliability, as well as enlarging functional capabilities owing to providing the possibility of routine control of measurement accuracy.

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Description

The invention relates to radar technology and can be used in the development of on-board means of measuring the flight altitude of aircraft.

A recirculation radio altimeter is known according to the USSR author’s certificate No. 326528, G01S 9/10, 1970, containing a transmitter, a receiver, an electronic tracking unit, a clock generator, a clock generator, a matching circuit, a trigger, an adjustable delay device, a control unit, a reversible pulse counter , counter for the number of recirculation periods.

All of the listed elements of this analogue, except for the control unit and counters, are also included in the inventive radio altimeter.

In this radio altimeter, the principle of recirculation is used, and an adjustable delay device and a control unit for this device are introduced to protect against height-leading interference.

The reason that impedes the achievement of the technical result provided by the invention in this analogue is a large systematic error of height measurement due to the instability of the signal delay in the internal elements of the radio altimeter (transmitter, receiver, etc.).

Free from this drawback is a pulsed recirculation radio altimeter protected by RF patent No. 2176382, G01F, 23/00, 2000. It contains a pulse shaper, a start-pulse generator, three delay devices, an OR circuit, a transmitter, a receiver, an antenna unit, a tank, a reflector reference signal, delayed pulse switch, selector pulse shaper, selector and processor.

In common with the claimed radio altimeter, this analogue is a pulse shaper, a start-pulse generator, a delay device, an OR circuit, a transmitter, a receiver, and an antenna unit.

In this analogue, the problem of increasing the accuracy of level measurement is solved by dividing the cycle of measuring the level of a substance in a tank in two stages. At the first stage, the systematic level measurement error is determined, caused by the instability of the signal delay time in the internal circuits of the device and the recirculation units. At this stage, recirculation is carried out during operation of the device by a reference signal generated by a special reflector, the distance to which from the antenna post is known with high accuracy. According to the results of recirculation by the processor unit, the time T _o is determined, which includes the instability of the signal delay time t _o in the internal circuits of the device, the signal delay time t _p in the recirculation circuits (selector, pulse shaper, delay device, OR circuit) and the signal propagation time t _on from the antenna unit to the reflector and vice versa. In the second stage, the recirculation occurs when the device is operating according to the signal reflected from the surface of the substance in the tank, and the time T _u is measured by the processor unit, which includes the same time intervals t _o and t _p as in the first mode, and in addition, the time interval t _{h the} propagation of the signal from the antenna unit to the surface in the tank and vice versa. Then, in the processor unit, the difference T _u -T _o is determined, which is then converted to the substance level in the tank to be measured.

Thus, the errors of level measurement caused by the instability of the time intervals t _o and t _p are excluded.

The reason that impedes the achievement of the technical result provided by the invention in this analogue is the rather high probability of disruption of the recirculation process as a result of fluctuations in the level of the signal reflected from the earth's surface when using this analogue as an onboard measuring instrument for the flight altitude of an aircraft. Another reason that impedes the achievement of the technical result in this analogue provided by the invention is the rather limited clock frequency of the processor unit, which leads to a significant increase in the required number of recirculation and, consequently, to an increase in measurement time and a dynamic error in height measurement.

The closest in technical essence to the claimed device (prototype) is a radar pulse recirculation radio altimeter, protected by RF patent No. 2273862, G01S 13/34, 2004. It contains the first OR element in series and the first delay line, the second delay line in series, the transmitter , directional coupler and decoupling unit, antenna unit, start-pulse generator, first and second AND elements, second OR element, trigger, microwave switch, amplitude-connected in series a detector and a third delay line, a receiver, a tracking unit, and a clock. In addition, the prototype includes a controlled delay unit, a timer, a third OR element, a second trigger, a fourth, fifth, sixth and seventh AND element, an inverter, a counter for the number of recirculation periods, a height pulse counter, a random access memory, a subtractor, an encryption block and code converter.

In common with the claimed radio altimeter, the prototype has the first and second AND elements, the first and second OR elements, the first, second and third delay elements, a trigger, a directional coupler, an isolation unit, an antenna unit, a microwave switch, a start-pulse generator, a clock pulse generator , transmitter, receiver, tracking unit, amplitude detector and their communication.

In the prototype, as in the radio altimeter according to the USSR author's certificate No. 326528, the principle of recirculation is used, and an encryption block, a controlled delay unit and a control unit for this unit are introduced into the radio altimeter to protect against height-leading interference. To ensure the absence of fluctuation of the pulse at the output of the controlled delay unit, the start-pulse generator is based on dividing the frequency of a stable generator. A tracking unit has been introduced into the prototype, providing tracking of the leading edge of the pulse taken from the output of the receiver, and recirculation both in the time measurement mode T _o and in the height measurement mode in the process of measuring time T _u = T _o + T _h , where T _h = 2H / C, here H is the flight altitude of the aircraft to be measured; C is the speed of light. Finally, the height is determined by determining the difference T _u -T _o and its corresponding conversion to the required height H.

The reasons that impede the achievement of the technical result in the prototype provided by the invention are the complexity and relatively low reliability due to the large number of elements included in the prototype and the difficulty of implementing a controlled delay unit to provide recirculation with a variable pulse repetition period.

The implementation of recirculation with a variable pulse repetition period significantly increases the variance of this period, that is, the variance of the period T _o (or T _u ), the average value (or expectation) of which is determined during the recirculation process. Therefore, the alternating period of the recirculation pulses leads to a sharp increase in the number of recirculation both in the control mode (when measuring the parameter T _o ) and in the mode of measuring the parameter T _u .

It should be noted that in the prototype the evaluation of the statistical accuracy of the measurement of parameters T _o and T _{u is} not conducted. The choice of the recirculation number is determined in advance by a large one, guaranteed to be sufficient to ensure a given statistical accuracy, which makes the measurement process unreasonably long. This, in turn, leads to an increase in the dynamic measurement error in the process of determining the height.

The technical problem to which the invention is directed is to simplify and increase the reliability of the radio altimeter, as well as expand the functionality of the device by providing the ability to monitor the accuracy of measurement.

To achieve the technical result, in a known recirculation radio altimeter comprising the first OR element in series and the first delay line, the second delay line in series, a transmitter, a directional coupler and an isolation unit, an antenna unit, the input-output of which is connected to the input-output of the isolation unit, start-pulse generator, the first and second AND elements, the first inputs of which are combined, and the second are connected to the input of the second delay line and the output of the start-them generator pulses, respectively, the second element OR, the first inputs of the first and second elements OR are connected to the outputs of the second and first elements AND, the trigger, the first and second inputs of which are connected to the outputs of the second and first elements OR, the microwave switch, the signal input of which is connected to the output of the decoupling unit, and the control input - to the output of the trigger, a series-connected amplitude detector, the input of which is connected to the second output of the directional coupler, and a third delay line, the output of which oh connected to the second input of the second OR element, a receiver, the first input of which is connected to the output of the microwave switch, a tracking unit, the first input of which is connected to the input of the second delay line, the second to the output of the receiver, the first output to the second input of the first OR element, and the second output is to the second input of the receiver and the clock pulse generator, a height calculation unit is introduced, the first input of which is connected to the first inputs of AND elements and is the control input of the radio altimeter, the second and third inputs are connected respectively to the third and the first outputs of the tracking unit, and the fourth input with the output of the clock generator, while the reset input of the start-pulse generator is connected to the first output of the tracking unit, and the output of the first delay line is connected to the input of the second delay line.

There are no sources of information in which the totality of the newly introduced block for calculating altitude and new communications in conjunction with the remaining elements of the proposed radio altimeter would be described. Therefore, the inventive radio altimeter should be considered new and inventive.

The invention is illustrated in the drawing, which shows:

- figure 1 is a structural diagram of the proposed radio altimeter;

- figure 2 is a structural diagram of a tracking unit;

- figure 3 is a flowchart of the algorithm for calculating the height.

The proposed recirculation radio altimeter comprises a start pulse generator 1, a clock pulse generator 2, AND elements 3 and 4, OR elements 5 and 6, delay lines 7, 8 and 9, a transmitter 10, a directional coupler 11, an isolation unit 12, an antenna unit 13, amplitude detector 14, microwave switch 15, trigger 16, receiver 17, tracking unit 18 and height calculation unit 19.

The tracking unit 18 includes a time discriminator 20, a low-pass filter 21, a time modulator 22, a capture signal driver 23, and an automatic gain control signal generator 24.

OR element 5, delay line 7, delay line 8, transmitter 10, coupler 11, decoupling unit 12 and antenna unit 13 are connected in series. The input of the detector 14 is connected to the second output of the coupler 11, and the output to the input of the delay line 9, the output of which is connected to the second input of the element 6. The first input of the element 6 OR is connected to the output of the element 3 AND, and the output to the first input of the trigger 16, the second the input of which is connected to the output of the OR element 5, and the output to the first input of the switch 15. The radio altimeter control input is connected to the first input of the block 19 and to the first inputs of the elements 3 and 4 AND, the second input of the element 3 AND is connected to the output of the delay line 7 and the first input of block 18, the second input of element 4 AND is connected to the output of the generator 1, and the output is connected to the first input of the OR element 5, connected by its second input to the first output of block 18, the third input of block 19 and the reset input of generator 1. The first input of the receiver 17 is connected to the output of the calculator 15, the second to the second the output of block 18, and the output with the second input of block 18. The second input of block 19 is connected to the third output of block 18, and the fourth with the output of generator 2.

The discriminator 20, the filter 21 and the modulator 22 are connected in series. The input of the driver 23 is connected to the output of the discriminator 20, the first input is the third output of the block 18, and the second output is connected to the third input of the driver 24. The first input of the driver 24 is connected to the output of modulator 22, the first input of discriminator 20 and the first output of block 18, the second input is combined with the second input of discriminator 20 and is the second input of block 18, and the output is the second output of block 18. The second input of modulator 22 is the first input of block 18.

The operation of the radio altimeter is as follows. Generator 1 is designed to ensure the beginning of recirculation or its resumption if it was interrupted unauthorized. The radio altimeter has two operating modes. In the first mode, the recirculation is carried out by a signal penetrating due to a specially created insufficient isolation between the transmitter 10 and the receiver 17 directly into the receiver 17 of the probing signal of the transmitter 10. At this stage, the delay time T _o in the recirculation circuits of the transmitter 10 and the receiver 17 is measured.

In the second mode, recirculation is carried out in conditions of sufficient isolation between the transmitter 10 and receiver 17. In this mode, the height measurement is actually carried out. Recirculation is carried out by a sounding signal reflected from the earth's surface. In this mode, the recirculation method measures the time interval T _u associated with the time interval T _{o by the} ratio:

T _u = T _o + T _h ,

where T _h is the transit time of the probe signal from the antenna unit 13 to the Earth and vice versa.

The time interval T _{h is} converted into the height H to be measured by the formula:

. $$H=\frac{C\cdot T_h}{2}$$

.

Generator 2 is designed to create a frequency-stable clock with a high repetition rate, providing measurement of short periods of time by block 19.

Logic elements 4 ÷ 9 and trigger 16 serve to organize the recirculation loop in each of the modes. The basis of the recirculation loop is the delay line 7 in the feedback circuit.

The delay line 8 is designed to provide a delay in the start of the transmitter 10 relative to the start of the block 18, which is necessary to start the block 18 when measuring small heights of the radio altimeter in the second mode.

The transmitter 10 is intended for the formation of probing microwave pulses of short duration of the order of ten nanoseconds.

The directional coupler 11 is designed to output part of the power of microwave oscillations generated by the transmitter 10.

The decoupling unit 12 is designed to ensure the operation of the transmitter 10 to the antenna unit 13 and the transmission of the pulses received at its input-output from the output of the antenna unit 13 to the input of the receiver 17.

The antenna unit 13 is designed to emit sounding pulses of a microwave transmitter and receive signals reflected by the earth's surface. When using unit 13 of narrowly directed antennas, it may include devices providing radiation of signals normal to the Earth's surface using control signals that carry information about the roll angles and pitch of the aircraft.

The detector 14 is designed to generate a video pulse at the time of the appearance of the probe signal of the transmitter 10.

The microwave switch 15 is designed to ensure the passage of the probe signal of the transmitter 10 to the input of the receiver 17 when the radio altimeter is in the first mode and when the attenuation of the switch 15 is reduced in the second mode.

The delay line 9 is designed to delay the pulse at the output of the detector 14 for a time exceeding the pulse duration of the transmitter 10.

The trigger 16 is designed to create a pulse, during which the attenuation of the switch 15 is minimal.

The receiver 17 is designed to amplify and convert received at its input pulses.

The tracking unit 18 is designed to highlight the reflected signal against the background of interference and generate a search pulse that monitors the leading edge of the pulse taken from the output of the receiver 17. It generates a "Capture" signal when the reflected pulse coincides with the search pulse, generates a voltage that regulates the gain of the receiver 17 in order to ensure a constant pulse amplitude at the output of the receiver 17.

Block 19 performs the measurement of parameters T _o , T _u and height H, while the measurement of parameters T _o and T _{u is} carried out in the recirculation process. With each step of recirculation, the achieved measurement accuracy is determined, and upon reaching the required measurement accuracy, the recirculation process is terminated, the result and measurement accuracy are fixed.

To set the radio altimeter in the first mode, a signal with a logic level is supplied to the first inputs of elements 3 and 4 and to the first input of block 19 to the control input.

The generator 1 generates pulses with a period exceeding the maximum possible period of recirculation. These pulses through the open element 4 and element 5 are fed to the second input of the trigger 16 and bring it into a state of logical zero, in which the switch 15 has a large attenuation.

The pulse of the generator 1 through elements 4 and 5, the delay line 7 also goes to the input of the delay line 8, to the first input of the block 18 and to the second input of the element 3. Since the level of the logical unit is applied to its first input in this mode, the pulse from the input of the element 3 passes to its output and through element 6 it enters the first input of trigger 16 and puts its output in the state of a logical unit, in which the attenuation of the switch 15 is small. The pulse passed through the delay line 8 starts the transmitter 10, forming a microwave pulse. This pulse, passing through the coupler 11, block 12 and the switch 15, is fed to the input of the receiver 17.

In the receiver 17, the pulse received at its input is amplified, converted into a video pulse arriving at the second input of block 18, a time modulator 22, which generates a search pulse at its first output and first output of block 18. The search pulse from the first output of block 18 is fed to the third input of block 19, to the reset input of generator 1, preventing its premature operation, and through element 5, to the input of the delay line 7.

The following process is repeated.

The delay of the search pulse relative to the pulse at the input of the delay line 7 and the first input of block 18 increases with each new pulse until its trailing edge coincides with the leading edge of the video pulse at the output of the receiver 17.

After several search pulses coincide with the video pulses of the receiver 17 at the input of the tracking unit 18, the voltage appears at the output of the temporary discriminator 20 of the tracking unit 18, which puts the unit 18 into the tracking mode of the video pulses of the receiver 17. Since the pulses reflected from the Earth go to the second output of the block 12 after the transmitter pulses , and block 18 performs a search, starting with a minimum delay, the capture of these pulses does not occur. Under the influence of this voltage, the driver 23 is triggered, and the block 18 at the third output generates a Capture signal with a logic unit level, which is fed to the second input of block 19. The driver 24 maintains a constant level of the video pulse at the output of the receiver 17, controlling its gain.

Thus, in the first mode, recirculation is carried out along the circuit: element 5, delay lines 7.8, transmitter 10, coupler 11, block 12, switch 15, receiver 17, block 18, element 5. In this case, the first pulse (trigger pulse) is formed generator 1 and from its output through element 4 is fed to the first input of element 5. Recirculation is carried out with a period T _about , determined from the ratio

T _o = τ ₇ + τ ₈ + τ ₁₀ + τ ₁₇ + τ _18,

where τ ₇ , τ ₈ , τ ₁₀ , τ ₁₇ , τ ₁₈ are the delay times of the elements of the radio altimeter having the corresponding numbers according to the structural diagram.

The remaining elements of the recirculation loop can be considered as inertialess.

For operation of the altimeter in the second mode, a signal with a logic zero level is supplied to the control input, to the first inputs of elements 3 and 4 and to the first input of block 19.

Elements 3 and 4 are closed, therefore, the pulse of the generator 1 does not pass to the output of element 4, and the pulses from the output of the delay line 7 do not pass to the output of element 3. Therefore, trigger 16 is in a state of logical zero, at which the attenuation of switch 15 is large, the level of probing the signal at the input of the receiver 17 is below the threshold of its sensitivity, and its capture by the tracking unit 18 does not occur. The pulses removed from the output of the delay line 7 trigger the transmitter 10, the microwave pulses of which through the coupler 11 and block 12 are fed to block 13 and are emitted in the direction of the Earth. Removed from the second output of the coupler 11, microwave pulses are detected by the detector 14 and through the delay line 9 and the second input of the element 6 are fed to the first input of the trigger 16, translating it into a state of logical unit, in which the attenuation of the switch 15 becomes minimal, which ensures passage to the input of the receiver 17 signals reflected from the earth's surface and received by block 13. These signals are amplified, converted by the receiver 17 and from its output are fed to the second input of block 18, in which they are processed in the same way as in the first mode. After the trailing edge of the search pulse of block 18 coincides with the leading edge of the video pulse of the receiver 17, block 18 generates a Capture signal at its third output, and at the second, a voltage of automatic gain control that maintains a constant amplitude of the video pulse.

Thus, in the second mode, recirculation is carried out along the circuit: element 5, delay lines 7, 8, transmitter 10, coupler 11, block 12, block 13, ground surface, block 13, block 12, switch 15, receiver 17, block 18, element 5. Recirculation is carried out with a period T _u exceeding the period T _o recirculation in the first mode for a time T _h , probing signal passing from the aircraft - carrier of the radio altimeter to the Earth and back.

Strictly speaking, the recirculation periods T _o and T _u are random values representing the time intervals between two adjacent search pulses of block 18. Block 19 determines the mathematical expectations of the values of T _o and T _u by the method of statistical tests. At its first input, a signal of a logical unit in the mode of measuring the expectation of the period T _o and a logic zero signal in the mode of measuring the expectation of the period T _u are received, at the second input, the signal "Capture" from block 18, indicating the establishment of the recirculation mode, at the third input - search pulses from block 18, and to the fourth input - counting clock pulses of the generator 2 stable frequency. In block 19, the statistical error of determining the expectation of periods T _o and T _{u is} also evaluated. In addition, it carries out the recalculation of the expectation periods T _o and T _u in the measured flight altitude of the aircraft.

The block diagram of the algorithm of operation of block 19 contains four operators (operators 25 ÷ 28 in figure 3).

The operator 25, upon receipt of a search pulse to the third input of block 19 from block 18, counts the number T _{i of} clock pulses (in nanoseconds) received at the fourth input of block 19 from generator 2 in the interval between adjacent search pulses in the current ith recycling cycle. Then, the counting result T _i and control are transferred to the operator 26.

The operator 26 determines the intermediate auxiliary parameters in the i-th recirculation cycle:

- the current expectation m _{i of the} period T _o (or T _u ):

$$m_i=\{\begin{array}{l}{T}_{\mathrm{one}}\text{,}e\mathrm{from}l\mathrm{and}i=\mathrm{one};\\ \frac{m_{i-\mathrm{one}}\cdot \left(i-\mathrm{one}\right)+T_i}{i},e\mathrm{from}l\mathrm{and}i>\mathrm{one};\end{array}$$

- the current sum of a _i squares of the time intervals between the search pulses:

$$a_i=\{\begin{array}{l}{T}_{{}_{\mathrm{one}}}^2\text{,}e\mathrm{from}l\mathrm{and}i=\mathrm{one};\\ a_{i-\mathrm{one}}+T_i^2,e\mathrm{from}l\mathrm{and}i>\mathrm{one};\end{array}$$

- the current amount b _i time intervals between the search pulses:

$$b_i=\{\begin{array}{l}{T}_{\mathrm{one}}\text{,}e\mathrm{from}l\mathrm{and}i=\mathrm{one};\\ b_{i-\mathrm{one}}+T_i,e\mathrm{from}l\mathrm{and}i>\mathrm{one};\end{array}$$

- the current error ξ _{i of the} estimate of the expectation m _i :

. $${\xi }_i=2t_{\alpha }\sqrt{\left(\frac{a_i}{b_i^2}-\frac{\mathrm{one}}{i}\right)\cdot \frac{i}{i-\mathrm{one}}}$$

.

here t _α is the quantile of the normal distribution corresponding to a given confidence probability of finding the expectation of the measured period in the interval m _i ± ξ _i .

Next, the calculation results m _i and ξ _i and control are transferred to the operator 27, which checks the conditions ξ _i > Δ, where Δ is the specified statistical error in estimating the expected m _i . The fulfillment of this condition means that the error ξ _{i of the} estimate is still quite large and recycling should continue. In this case, control returns to the operator 25, and the described process continues with increasing the number i of the recirculation cycle. The fulfillment of the condition ξ _i ≤Δ means that the statistical error in estimating the expectation m _i does not exceed a given one. In this case, control is transferred to the operator 28, which stops the recirculation, displays the obtained calculation results m _i and ξ _i as final:

m is m _i ;

ξ = ξ _i .

In addition, the operator 28 recounts the calculated expectation of periods T _u and T _i in the final result - the flight height H of the carrier of the radio altimeter. The calculation is carried out according to the formula:

, $$H=\frac{C\cdot \left(m_u-m_o\right)}{2}$$

,

where C = 3 · 10 ⁸ m / s is the speed of light;

m _u - expectation of the period T _u in seconds;

m _o is the expectation of the period T _o in seconds.

The result of the conversion is displayed and, if necessary, recorded along with the current time using the display tools included in block 19 (not shown in the drawing).

This completes the measurement process. Block 19 and the radio altimeter as a whole are ready to measure the new value of the flight height of the aircraft.

It is easy to see that the proposed radio altimeter, unlike the prototype, does not contain a difficult to implement and operate a controlled delay unit with an encryption block, pulse counters, memory and subtractors, a timer, a code converter and a large number of logic elements. This makes the claimed radio altimeter simpler and more reliable. The presence in the prototype of the controlled delay unit and the related ability to control the pulse repetition period do not give it advantages over the claimed radio altimeter. The fact is that the presence of a controlled pulse repetition period is indirectly a sign of the presence in the radio altimeter of protection against interference leading in height and stimulates the adoption of appropriate effective countermeasures that do not require accurate knowledge of the pulse repetition period.

The proposed radio altimeter monitors the accuracy of calculating the expectation of the recirculation period, and the recirculation process stops immediately when sufficient calculation accuracy is achieved. This allows us to reduce the recirculation process in the proposed radio altimeter compared to the prototype, where such control is absent, and you have to recycle with unwarranted accuracy of the result or deliberately overestimate the number of recirculation, which makes the calculations unreasonably long and leads to an increase in the dynamic error of height measurement.

The proposed radio altimeter is quite easy to implement. The newly introduced block 19 can be implemented on the basis of programmable logic integrated circuits such as FLEX firm ALTERA. In principle, the functions of this unit can also be performed by the on-board computer of the radio altimeter carrier when programming this computer to perform the corresponding functions and establish the appropriate connections with the remaining elements of the radio altimeter.

The remaining components of the proposed radio altimeter (generators 1 and 2, logic elements 3-6, delay lines 7 ÷ 9, transmitter 10, directional coupler 11, decoupling unit 12, antenna unit 13, detector 14, microwave switch 15, trigger 16, receiver 17 and the tracking unit 18) can be implemented based on the corresponding constituent elements of the prototype.

Claims (1)

A recirculating radio altimeter containing a first OR element and a first delay line connected in series and a second delay line connected in series, a transmitter, a directional coupler, an isolation unit, an antenna unit, the input-output of which is connected to the input-output of an isolation unit, a start-pulse generator, the first and the second AND elements, the first inputs of which are combined, and the second are connected to the input of the second delay line and the output of the start-pulse generator, respectively, the second OR element, the first inputs of the first о and the second OR element are connected to the outputs of the second and first OR elements, respectively, a trigger, the first and second inputs of which are connected to the outputs of the second and first OR elements, respectively, a microwave switch, the signal input of which is connected to the output of the decoupling unit, and the control input to trigger output, an amplitude detector connected in series to the second output of the directional coupler, and a third delay line, the output of which is connected to the second input of the second OR element, receiver, p the first input of which is connected to the output of the microwave switch, a servo unit, the first input of which is connected to the input of the second delay line, the second to the output of the receiver, the first output to the second input of the first OR element, and the second output to the second input of the receiver, and the generator clock pulses, characterized in that a height calculation unit is introduced into it, the first input of which is connected to the first inputs of the first 3 and second 4 AND elements and is the control input of the radio altimeter, the second and third inputs are connected respectively to the third and first output the tracking block, and the fourth input is with the output of the clock generator, while the reset input of the start pulse generator is connected to the first output of the tracking block, and the output of the first delay line is connected to the input of the second delay line.

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