RU2304290C2 - Method for determining distance from upper-air radio probe - Google Patents

Abstract

FIELD: radio engineering, namely radiolocation, possible use for determining inclination distance from upper-air radio-probes by radio-impulse methods, and also possible use for tracking distance to upper-air radio-probes.

SUBSTANCE: in accordance to invention, ground-based radiolocation station is used to dispatch query signal to an upper-air radio-probe, which, by means of ultra-regenerative transmitter-receiver is amplified and reemitted towards radiolocation station, where query and response signals are compared, delay times between them are determined and, on basis of delay time, distance to upper-air radio probe is determined. As query signal, coherent query radio impulses are used, which synchronize the radio impulse phase of ultra-regenerative transmitter-receiver. Comparison of query and response signals is realized by means of a phase detector.

EFFECT: decreased power of radiolocation station query signal transmitter, increased resistance of complex to interference and increased concealment of operation of ground-based radiolocation station.

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Description

The invention relates to radio engineering, namely to radar, and can be used to determine the oblique range by a radio-pulse method, for example, to upper-air radiosondes (ARZ), can also be used to accompany ARZ in range.

The well-known radio-pulse method of determining the distance to the target, in which the distance is determined by measuring the travel time t _p = 2R _n / C by the probing radio-pulse signal of the distance from the radar to the reflecting target and vice versa, where R _n is the inclined distance to the target, C is the speed of light. The propagation time t _p can be measured directly when fixing the moments of radiation of the probing and receiving the reflected signals.

The disadvantage of this simple method is the following: a rapid decrease in the level of the reflected signal with increasing distance, a large intensity of interference at short distances created by the reflected signal from local objects, and the difficulty in ensuring the specified measurement accuracy at low levels of the response signal at large distances.

A distinctive feature of domestic radiosounding systems is the measurement by the radio-pulse method of inclined range to ARZ, equipped with a super-regenerative transceiver (SPP), which provides an active response signal. The request radio pulse from the upper-air radar causes a change in the structure of the radio pulses constantly emitted by the ARZ transceiver, expressed in the appearance of an energy maximum — the primary reaction ξ ₁ and an energy minimum in the form of a “pause” - the secondary reaction ξ ₂ (Fig. 1). The time delay from the moment the request signal is generated - the start pulse of the upper-air radar transmitter to the energy minimum in the response signal t _p received by the upper-air radar determines the value of the real slant range to the ARZ, see A.A. Efimov “Principles of operation of the aerological information and computer complex AVK -1 ", M .: Gidrometeoizdat, 1989, pp. 61-67 - prototype. The sensitivity of the super-regenerative radiosonde transceiver to the radar interrogation signal in this operating mode is about minus 86 dB / W, and the pulsed power of the radar interrogation signal transmitter with an operational radius of 200 km is 15-20 kW.

The essence of the known method is that the formation of a response pause occurs due to the reduction in the duration of the leading edge of the radio pulses (super-regenerative effect) of the SPP, which coincide in time with the requested incoherent radar pulses. (More precisely, this occurs when the requested radio pulses coincide with the receiving interval τ _pr SPP, which is close to the moment the SPP self-oscillator is turned on by super-energizing pulses. The frequency of super-generating (control) pulses F _c determines the repetition rate of the SPP radio pulses and is about 800 kHz. It should be emphasized that the repetition rate interrogation radio pulses (period T _p , see Fig. 7) determines an unambiguous range measurement and amounts to about 800 Hz with an operational radius of a radio sounding system of 200 km.). In this case, a corresponding increase in the energy of these SPP radio pulses occurs due to an increase in their duration. Figure 1 shows this as an increase in the amplitude of the radiosonde signal (primary reaction ξ ₁ ) at the output of the amplitude detector of the radar receiver. The inertial auto-bias circuit of the SPP auto-generator during generation of radio pulses having a longer duration receives an additional charge in the locking direction. Therefore, the SPP self-oscillator is locked for a short time (of the order of 0.5 μs) and stops the emission of subsequent radio pulses. A characteristic pause is formed (secondary reaction ξ ₂ ) in the received radiosonde signal, from which the delay time t _p is determined and the slant range is calculated. However, for the formation of a response pause, a certain power of the radar query signal is required, which falls on the input of the SPP, which should be at least minus 86 dB / W.

This method and the theory of SPP with a secondary reaction in the modern interpretation are described in detail in the monograph (see Radio sounding of the atmosphere. Ivanov V.E., Fridzon MB, Yesyak SP Yekaterinburg. Ural Branch of the Russian Academy of Sciences. 2004. 596 pp. ISBN 5 -7691-1513-0).

It should be emphasized that for the formation of the response signal SPP in the prototype uses only the energy of the interrogation radio pulses. Information about the phase of the high-frequency filling of the radio pulses is not used.

An object of the invention is to reduce the power of the transmitter of the interrogation signal, increase the noise immunity of the complex and increase the stealthiness of the ground radar.

The specified goal is solved as follows. A method is proposed for determining the distance to an aerological radiosonde equipped with a super-regenerative transceiver, including supplying a terrestrial radar interrogation signal to an aerological radiosonde, amplifying it and re-emitting with a super-regenerative transceiver in the radar direction, characterized in that coherent interrogation radio pulses are used as the interrogation signal, which synchronize the synchronizing phase radio pulses of a super-regenerative radiosonde transceiver, re-emit them in the direction of the radar, in determined from the received radiation superregenerative Coherent Transceiver response rf pulses, determine the time delay between the interrogation and response coherent radio pulses and the delay time determined by the distance to the radiosonde.

Figure 1 shows: U _zs - envelope of the interrogated radar pulses; U _o - the response signal in the form of a primary reaction ξ ₁ and a secondary reaction ξ ₂ - the energy minimum (pause) at the output of the radar receiver.

Figure 2 shows: (a) the spectrum of unsynchronized radio pulses G (f) emitted by the SPP of the aerological radio probe; (b) the amplitude-frequency characteristic Y (f) of the SPP in the reception mode.

Figure 3 shows the change in the density function of the distribution of the phase difference W (φ) of the harmonic signal and the noise in the circuit during the receive interval τ _pr operation SPP depending on the ratio of the level of the request signal to noise S.

Figure 4 shows the response spectrum radio pulses synchronized CPR _CPR G (f) and the spectrum of the interrogation signal _gc G (f). Carrier frequency radio pulses NGN - f _spp. The carrier frequency of the interrogation signal is f _ss .

Figure 5 shows a structural diagram of a radar with coherent-pulse processing of the response signal of a super-regenerative transceiver; which shows: 1 - radar synchronizer; 2 - coherent pulse transmitter; 3 - antenna switch; 4 - receiving device; 5 - phase comparison unit (phase detector PD); 6 - range measurement system; 7 - antenna ground radar (A _radar ); 8 - antenna ARZ (A _arz ); 9 - SPP ARZ; U _ss - request signal; U _on (t) is the reference signal; U _with (t) - signal from the output of the radio channel; U _CR - signal from the receiving unit; U _o (t) is the desired signal of useful information; U _c1 , U _c2 - signals of time synchronization of the transmitter and ranging system; U _D - signal range.

Figure 6 shows the response waveform of a super-regenerative transceiver (SPP) at the output of a phase detector U _PD radar. Here: U _oc - response signal level; U _σ = fluctuation component in the response signal, depending on the level of the request signal S.

Figure 7 shows a sequence of interrogation radio pulses U _ss and a response signal U _PD at the output of the radar PD.

The coherent pulse transmitter 2 is connected by a request signal U _ss to the signal input of the antenna switch 3, and a reference signal U _on (t) to the reference input of PD 5; the antenna switch 3 signal output U _with (t) through the receiving unit 4 is connected to the signal input of the PD, the input / output is connected to the antenna of the ground radar (A _radar ) 7, which is connected via the radio channel to the antenna ARZ 8, which in turn is connected to the input / output SPP ARZ 9; synchronizer 1 is connected to the input of the coherent transmitter 2 and to the input of the ranging system 6.

These nodes and blocks can be performed on the following ERE and IC. Coherent pulse transmitter 2 can be performed on the basis of a frequency synthesizer generating a reference coherent signal at a frequency received at atmospheric sensing radar stations f = 1680 ± 10 MHz; the phase comparison unit (PD) 5 can be performed according to the scheme, see "Radio receivers", ed. N.N. Fomina, M, P and S, 1996, pp. 325-328; antenna switch 3 can be performed according to the standard scheme of a balanced antenna switch, see "Microelectronic microwave devices", ed. G.I. Veselova, Moscow: Higher School, 1988, p. 82-83; the receiving unit 4 can be performed on a low-noise amplifier with a delayed AGC, see "Radio receivers", ed. N.N. Fomina, M, P and S, 1996, p. 229; radar antenna A _radar 5 can be made in the form of a phased antenna array, see RF Patent No. 2161847; ARZ 8 antenna system and SPP radiosonde 9 can be performed according to RF patents No. 2214614 and No. 2172965, respectively; synchronizer 1 and a range measuring system can be performed on standard microcontrollers.

The following assumptions are made in the structural diagram: the overall synchronization of the nodes and blocks of the radar from the microprocessor control system, which are also not shown, is not shown, the antenna switch control is not shown, the internal structure of the receiving unit is not shown, etc., which are not mandatory for consideration method.

The main feature of this method is the actual construction of the SPP and features of receiving radar response signals from the SPP ARZ. The essence of the proposed method is as follows.

The method for determining the range to the radiosonde proposed in the application materials is fundamentally different from the known one, since in this case the response signal of the SPP is not associated with the energy of the response radio pulses, but with the phase of their high-frequency filling imposed by the coherent signal of the radar transmitter. In this case, a pause in the radiation of the SPP (secondary reaction ξ ₂ ) is not formed and is not required to isolate the response signal of the radiosonde. Detection and tracking of the response signal occurs at the output of the phase detector (PD) of the radar, which responds to the phase of the incoming radio pulses, comparing with the phase of the interrogated radio pulses.

A fundamental feature of the operation of the SPP is the complete statistical independence of the emitted radio pulses, i.e. the phase of each radio pulse, determined by noise fluctuations in the NPS circuit at the time of its start, is completely uncorrelated with the phase of the previous radio pulse. The process of synchronizing the phase of self-oscillations occurs during the reception interval τ _pr operation of the SPP and determines the phase of the emitted radio pulses.

In the absence of a request signal, the high-frequency phase of the SPP radio pulses is formed under the influence of fluctuation noise, which is valid during the receiving interval τ _pr SPP. Since the fluctuation fluctuations in the SPI loop are close in nature to “white noise”, the initial phase of the radio pulses will be distributed uniformly in the range from 0 to 2π.

, что соответствует равномерному распределению фазы узкополосного стационарного нормального случайного процесса. Поэтому спектр радиоимпульсов излучаемых СПИ имеет сплошной шумовой характер в пределах огибающей спектра, см. фиг.2.Figure 3 shows the law of the density of the phase distribution of the random process, which obeys the phase distribution of the SPP radio pulses. When the signal is absent (s = 0, s = U _c / σ is the ratio of the signal amplitude U _c to the rms value of noise σ in the circuit), this law is represented by a straight line passing at the level

, which corresponds to a uniform phase distribution of a narrow-band stationary normal random process. Therefore, the spectrum of the radio pulses emitted by the SPI has a continuous noise character within the envelope of the spectrum, see figure 2.

The appearance of a harmonic external signal with an amplitude U _c comparable to and also above the noise level σ in the SPP loop leads to the appearance of a regular component in the phase distribution of the random process. In the general case, the phase distribution law of a random fluctuation process in a circuit when exposed to an external harmonic signal is described by an expression of the form:

,provided

,

where s = U _c / σ is the ratio of the signal amplitude U _c to the rms noise value σ in the circuit; F (scosφ) is the probability integral.

Figure 3 also shows the calculated dependences of the law of distribution of the phase difference between the random process and the external influence, depending on the signal-to-noise ratio s. From the presented dependences it is clearly seen that even with S = 3 or more, the phase of the external signal is dominant and almost completely determines the phase distribution law. Thus, an external signal, which is approximately 10-15 dB higher in power than the internal noise in the SPP loop, causes almost complete synchronization of the phase of the SPP radio pulses. This ensures a tight binding of the phase of the SPP radio pulses to the phase of the interrogation signal. Therefore, SPP can be considered as an active phase repeater with a very high sensitivity. So, with the real power of noise SPP in the range - 120-125 dB / W, the required power of the interrogation signal, providing phase synchronization, will be no more than minus 110-115 dB / W.

Thus, when a sequence of coherent interrogating radio pulses appears at the input of an NPS, the NPS responds with a sequence of synchronized coherent radio pulses, the spectrum of which has a discrete linear character G _ns (f) (see Fig. 4). In Fig. 3, the spectrum of the interrogation signal G _zs (f) is presented for simplicity as a single spectral harmonic component, since the duration of interrogation radio pulses τ _zs = 1.5-3 μs is several times greater than the duration of the SPP radio pulses τ _and = 0.25-0.35 μs and is tens times the length of the receiving interval τ _CR = 0.05 μs SPP, during which the synchronization effect occurs. Thus, a coherent radar interrogation signal, due to phase synchronization from a continuous spectrum, forms a discrete, linear spectrum of an SPP. In this case, one of the discrete components of the spectrum is related to the frequency of the external signal f _ss accurate to phase, and the other discrete components will be apart from each other at a distance equal to the value of the superimposing frequency F _c , which is set by the generator of the supporting voltage of the SPP and from the external signal depends. In general, the position of discrete spectral components f _sppi about the carrier frequency f _spp arbitrary and depend only on the current position of the interrogation signal frequency f _sc from the carrier frequency f CPR _spp.

Comparison of the phase of the response radio pulses with the phase of the reference signal in the radar receiver can in principle be carried out at the carrier frequency of the radio system or at the intermediate frequency of the radar receiver. It is necessary to explain the structure of the signal at the output of the PD. In the absence of a request signal, the sequence of SPP radio pulses at an intermediate frequency supplied to the PD input has a continuous, noise-like spectrum similar to the microwave spectrum shown in Fig. 4. In this case, the phases of the SPP radio pulses are uncorrelated and evenly distributed, and the output signal of the PD is a continuous noise stream of bipolar video pulses (see Fig. 6) uniformly distributed in amplitude over the entire range from -U _max to + U _max .

During the time of action of the interrogation coherent radio pulses at the input CPR its response spectrum RF pulse _spp G (f) at the output of the receiver, as noted, will also have a discrete structure (see FIG. 4). Therefore, the signal at the output of the PD will vary with the beat frequency F _D between the frequency of the reference signal f _os and the first matching harmonic f _{cf0 of the} synchronized radio pulses. The frequency of the beats with other harmonics of the spectrum of the SPP f _sppi increases in proportion to F _c and the number of these harmonics relative to f _op and f _spp0 (see figure 4). Therefore, the total signal at the output of the PD U U _PD is very complex. To reduce the effect of the higher components of the beats at the output of the PD, a low-pass filter is used. The passband of the low-pass filter should be selected from the condition for the formation of a response signal in range. The duration of the response signal is fundamentally equal

where τ _ss - the duration of the request signal; τ _CR - the duration of the receiving interval of the operation of the SPP; τ _and - the duration of the SPP radio pulses.

Therefore, the low-pass filter band must be chosen from the condition ΔF≥1 / τ _holes.

Ultimately, when phase-synchronized radio pulses of the SPP response signal appear at the input of the receiving device (at a constant value of the inclined range R _n ), the PD output signal is set at some certain level U _oc during the action (duration τ _ss ) of the request radio pulse (see Fig. .6) proportional to the phase difference of the reference signal and the received radio pulses. It must be emphasized that the width of the level line of the response signal U _oc is determined by the rms value of the phase distribution density σ during the operation of the interrogation signal (see FIG. 3), in other words, the power level of the interrogation signal P _ss .

Figure 6 conditionally accepted that the delay time of the request and response signals when they propagate to the radiosonde and vice versa is zero (R _n = 0). When the slant range R _n changes, the level of the response signal U _oc will shift parallel to the abscissa axis with the Doppler frequency F _D in the entire range from -U _max to + U _max . To improve the observation conditions and reduce the effect of phase noise of unsynchronized SPP radio pulses, the response signal is then extracted using the gates generated in the slant range measurement system. The duration of the gates is chosen equal to the duration of the response signal of the NGN.

It should be noted that usually the value of the (superficial) frequency of the SPP radio pulses repetition rate F _c is ten times higher than the repetition frequency of the requested radio pulses F _p In addition, the moments of arrival of the interrogated radar pulses at the input of the SPP and the launch of the SPP radio pulses are not correlated, random. Therefore, in FIG. 6, FIG. 7, the oscillogram of the output video pulses of the PD synchronized with the moment the transmitter starts the request signal and the arrival of the response signal and is not synchronized with the moment the radio pulses start SPP is perceived as an envelope with continuous filling (the shaded part in FIGS. 6, 7 )

The position of the response signal U _oc on the time axis is shifted in proportion to the slant range, which is determined by the delay time of the response signal relative to the moment of emission of the interrogation radio pulse t _p , see Fig. 7. Coherent interrogation radio pulses U _c (t) are supplied with a repetition period T _p . Thus, the separation of the response signal of the SPP from the total stream of video pulses, the measurement of the delay time t _p allows us to determine the range to the radiosonde. In general, the operation of the tracking system of the slant range measuring unit is reduced to a strobe offset within the repetition period of interrogation radio pulses, which extracts a response signal from all radiosonde radiation. In the absence of a signal, the spectrum during the gating pulse has a fluctuation character. A sign of the appearance of the response signal is a change in the spectrum of the signal U ^* _PD in the gating interval. In other words, when a response signal appears in the strobe, it acquires a regular character associated with the presence of the Doppler frequency.

From the foregoing it follows that the fundamental difference between the proposed method of measuring range from the classical analogue adopted in coherent-pulse radars is that the detection and processing of response coherent radio pulses occurs against the background of unsynchronized radio pulses, and the carrier frequency f _cfu due to the instability of the microwave oscillator SPP can significantly differ from the frequency of the interrogation (probing) signal f _ss in comparison with the Doppler frequency shift. In classical coherent-pulsed radars, a self-reflected signal is received, which can be shifted in frequency only due to the Doppler effect. Therefore, to ensure the operability of the radio system according to the proposed method under operating conditions, it is necessary to take measures to automatically adjust the frequency of the radar transmitter and receiver to the radiation frequency of the radar detector, and also to compare the phase of the interrogation and response radio pulses in order to detect and track the response signal in range against the background of unsynchronized radio pulses.

Thus, the proposed method for synchronizing the high-frequency phase of the SPP radio probe radio pulses with coherent interrogation radar pulses, extracting the response radio pulses from the total stream of non-synchronized SPP radio pulses using the phase detector of the radar receiver with the aim of measuring the oblique range to the radiosonde is significant novelty, it can significantly improve the performance of the radiosonde system namely:

- practically the value of the sensitivity of the SPP at the level of 110-115 dB / W allows to reduce the pulsed power of the radar interrogator signal transmitter to 50-100 W (average power not more than 0.1 W when the interrogation duty cycle of the radio pulses is about 1000), which significantly increases the secrecy of the operation of the radio sounding system, bringing it closer to the secrecy of the direction finding system, but provides significant superiority over the latter in accuracy of measuring range, altitude, speed and direction of the wind. The proposed method allows for the size of the aperture of the antenna system of 1.4 meters (gain of about 26 dB) to provide a maximum range of the radar system of at least 200 km.

- the proposed method allows to measure with high accuracy the instantaneous wind speed using the Doppler effect.

- When setting the active continuous interference of the SPP radio probe, the noise immunity of the radio channel for measuring the range by the phase method of extracting the response signal is higher than the noise immunity of the radio channel operating on the principle of the response of the SPI - “response pause”, by 10-15 dB.

- The stability and stability of the SPP in the phase synchronization mode is much higher than in the secondary reaction mode. Configuring NGN in a production environment is greatly simplified and boils down to adjusting the operating frequency.

- At the same time, the level of the amplitude noise of the SPP decreases, the duration of the radio pulses can be increased to the optimal value of τ _and = 0.5τ _s , which reduces the width of the spectrum by 1.5-2.0 times, the efficiency of the transceiver increases to 0.35-0.45. All these measures increase the potential of the radio channel by 2-4 dB.

Thus, the proposed method can significantly improve the technical and economic characteristics of the radio sounding system, guaranteed to ensure its competitiveness in the world market of modern meteorological radio telemetry systems.

Claims (1)

A method for determining the distance to an aerological radiosonde equipped with a super-regenerative transceiver, according to which a ground signal is supplied to the aerological radiosonde by a ground-based radar station, amplify it and re-emit in the direction of the radar, where the interrogation and response signals are compared, determine the delay time between them and, according to the delay time, determine the range to the upper-air radiosonde, characterized in that as the request signal is they use coherent interrogation radio pulses that synchronize the phase of the radio pulses of the super-regenerative transceiver, as well as the fact that the interrogation and response signals are compared using a phase detector.

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