RU2042958C1 - Method for determining range to lightning discharge source - Google Patents

Abstract

FIELD: detection and ranging. SUBSTANCE: electromagnetic lightning-discharge signal (atmospheric noise) is received by vertical rod antenna, amplified, filtered off in broad frequency band, delayed in time, processed concurrently in n channels (range scale divisions), each of which is tuned to fixed range to lightning discharge source, by determining consistence of range in each scale division with recorded atmospheric noise of this range scale division; values obtained in the process are compared with each other for all range scale divisions; range division with maximum value is determined and considered as range to lightning discharge source. EFFECT: facilitated procedure. 5 dwg

Description

 The invention relates to radio engineering means of determining sources of electromagnetic radiation, in particular to methods of passive ranging of sources of electromagnetic signals, and can be used in meteorology and civil aviation for operational monitoring of thunderstorm activity at distances of 300-2000 km.

 The known method of single-point ranging of lightning radiation sources, implemented in the device [1] This method is based on the use of different dependences of the attenuation of the spectral components of the electromagnetic signal from the distance to the radiation source and consists in that they take the vertical electric component of the lightning discharge field and process the received signal in parallel in two channels, in the first of which the signal is amplified, filtered in a wide frequency band, differentiate and determine the amplitude of the field of the studied signal, in the second channel the signal is amplified, filtered in a wide frequency band, integrated and the amplitude of the received signal is determined, the distance to the lightning discharge is determined from the obtained ratio of these signals.

 The disadvantage of this method is the dependence of the range indicator on the signal spectrum in a lightning source, which leads to a significant error in the measurement of range.

The closest technical solution to the declared one, adopted as a prototype, is a one-point method for determining the distance to remote sources of pulsed electromagnetic signals, based on the use of the dependence on the distance of the time delay between the earth and the first ionospheric rays, implemented in the device [2]
This method consists in taking the vertical electrical component of a lightning discharge containing the earth and the first ionospheric rays, amplifying it, filtering it in a wide frequency band, delaying it in time, applying it to the first input of the range indicator, the filtered signal is also compared with a threshold level, when the threshold level is exceeded, a single sawtooth pulse is generated for horizontal beam scanning on the screen of the cathode-ray tube indicator, according to the image of the received signal on the display screen ora, whose time axis is graduated in units of distance from the source to visually determine the ionospheric delay of the first beam relative to earth beam and thereby determine the range to the lightning source.

 The disadvantages of this method are the low accuracy (about 20% of the true range) and the long measurement time (about 10 s) associated with a visual assessment of the range from the image of the received signal on the screen of the cathode ray tube.

 The aim of the present invention is to improve the accuracy and reduce the time of measuring the distance to the source of a lightning discharge.

 In FIG. Figure 1 shows the geometric propagation paths of the earth ray (O), as well as the first (IP 1) and second (IP 2) ionospheric rays.

 Figure 2 presents the theoretical expected estimates of the modulus of the ratio of the amplitudes of the first (A1, A2) and second (A3, A4) ionospheric rays, respectively, relative to the earth beam for daytime (A1, A3) and night (A2, A4) signal propagation conditions.

 Figure 3 presents a temporary form of the implementation of the pulsed atmospheric signal received from a distance of 2000 km under night propagation conditions.

 In FIG. 4 shows the dependence of the voltages at the outputs of the processing channels corresponding to the gradations of the range when processing the signal shown in FIG. 3 using the described method.

 Figure 5 presents a block diagram of a single-point ranging device: 1 electric antenna, 2 amplifier, 3 filter, 4 delay unit, 5 threshold unit, 6 synchronization unit, 7-9 processing channels (range gradations), 10 channel determination unit with maximum output level, 11 range indicator.

S(t-τ_i)*K_i, (1) где S(t) земной луч, S(t- τ_i) * K_i i-ый ионосферный луч, τ_i временная задержка i-го ионосферного луча относительно земного луча в принятом сигнале атмосферика ( τ_o 0), а К_i соотношение амплитуд i-го ионосферного и земного лучей с учетом их полярностей (К_о 1).The essence of the proposed method is based on the multipath propagation of a signal from the emitter to the receiver in the Earth-ionosphere waveguide channel, as a result of which it is possible to represent the received atmospheric signal as a superposition in the general case of partially overlapping earth and several ionospheric rays and using the time delays depending on the distance to the source and the ratio of the amplitudes between each of the ionospheric rays and the earth beam in the received signal for measuring the distance to a lightning discharge. At distances of 300-2000 km, the received atmospheric signal can be recorded as a superposition of similar in the form of terrestrial and ionospheric rays:
Z (t)

S (t-τ _i ) * K _i , (1) where S (t) is the earth ray, S (t-τ _i ) * K _{i is the} i-ionosphere beam, τ _{i is the} time delay of the i-th ionosphere ray relative to the earth ray in the received signal is atmospheric (τ _o 0), and K _{i is the} ratio of the amplitudes of the i-th ionospheric and terrestrial rays, taking into account their polarities (K _o 1).

2i

-L

/C, (2) где R 6370 км радиус Земли; С 3.10⁵ км/сек скорость распространения электромагнитного сигнала; h эффективная высота нижней отражающей границы ионосферы, равная 67 км для дневных условий распространения и 87 км для ночных условий распространения сигналов.The values of τ _i K _i (i = 1 ÷ q) are functions of L _{o the} distance to the lightning discharge, and the delay is obtained taking into account the sphericity of the Earth (Fig. 1) as
τ _i =

2i

-L

/ C, (2) where R 6370 km is the radius of the Earth; From 3.10 ⁵ km / s the speed of propagation of the electromagnetic signal; h is the effective height of the lower reflecting boundary of the ionosphere, equal to 67 km for daytime propagation conditions and 87 km for nighttime propagation conditions of signals.

The dependences of K ₁ , K ₂ (Fig. 2) on the range to a lightning discharge were obtained from [3] and from experimental data.

To determine the range to a lightning discharge source, according to the invention, it is proposed to check the received atmospheric signal for its correspondence to each j = th (j 1-n) range gradation tuned to the range LL _j to the radiation source, while the range gradation jb most suitable atmosphere, is taken as the distance to the source.

Z(t)-

V_j(t-τ_j,i)*K_j,iK

dt, (3) полагая, что V_j(t) ≡ 0 при t≅0 и при t>T_o.To check this correspondence, a base beam U _j (t) was introduced in each range gradation, which minimizes the residual value W _j :
W _j =

Z (t) -

V _j (t-τ _{j, i} ) * K _{j, i} K

dt, (3) assuming that V _j (t) ≡ 0 for t≅0 and for t> T _o .

Substituting the function Z (t) from (1) in the right-hand side of equation (3), we obtain that W _j 0 while conditions V (t) = S (t), τ _{j, i} = τ _i , K _{j, i} = K _i . Whence it follows that for j = b, where the b-th gradation of the range is adjusted to the range L _b L _o , which correspond to the values of τ _i and K _i (i 0 ÷ q), by choosing the corresponding function V (t) it is possible to minimize the function Wb getting W _bmin W _{min, min} .

Z_j,k-

V_j,k-r·K

, (4) здесь и далее r r_j,i= τ_j,i/Δt, M T_o/ Δt, N T_q/Δt, причем V_{j, m}=o при m ≅0 и m > M.To simplify further calculations, we represent Z (t) and V _j (t) at discrete points t _k with a step Δ t, whence we obtain
W _j = Δt

Z _{j, k} -

V _{j, krK}

, (4) hereinafter rr _{j, i} = τ _{j, i} / Δt, MT _o / Δt, NT _q / Δt, and V _{j, m} = o for m ≅ 0 and m> M.

K_j,l·K_j,lV_j,m+r-u=

K_j,i·Z_j,m+r, (5) где U τ_j, l/Δ t.To determine V _{j, m} , minimizing the value of W _j , we equate to zero the derivatives of W _{j with} respect to V _{j, m} for all m 1-M, whence we obtain the system of equations

K _{j, lK j, l} V _{j, m + ru} =

K _{j, i} · Z _{j, m + r} , (5) where U τ _j , l / Δ t.

Z_j,m+r·K_j,i-

K_j,l·K_ji·V

(6)
Так как для дальнометрии требуется знать только минимальные значения W_j,min (а не V_j,m), в дальнейшем для упрощения вычислений W_j,min производится последовательная итерационная оценка поправок V_j,k ^(d) (d=1÷p) к значениям V_j,k, при этом при каждом значении m образуются новые значения

=

-K_j,i·V $\genfrac{}{}{0ex}{}{\text{(d)}}{\text{j,K}}$ (i=0÷q). При этом на каждом шаге итерации невязка равна
W_j= Δt

Z $\genfrac{}{}{0ex}{}{\text{2}}{\text{j}}$ _,m
Так как при этом для всех m 1-M, в уравнении (6) имеем V_j,k+r-u ^(d) 0, то получаем следующую процедуру действий: положим m 1, при фиксированном m оценка V_j,m ^(d) равна
V $\genfrac{}{}{0ex}{}{\text{(d)}}{\text{j,m}}$

K

K $\genfrac{}{}{0ex}{}{\text{2}}{\text{j}}$ _,i, Переходим к (q+1) новым значениям

по правилу

=

- V $\genfrac{}{}{0ex}{}{\text{(d)}}{\text{j,r}}$ ·K_j,i(i=0÷q).Moving V _{j, m} to the left, we get
V _{j, m} =

Z _{j, m + rK j, i} -

K _{j, lK jiV}

(6)
Since long-range measurement requires only the minimum values of W _{j, min} (and not V _{j, m} ), in the future, to simplify the calculations of W _{j, min} , a sequential iterative estimate of the corrections V _{j, k} ^{(d) is} performed (d = 1 ÷ p) to the values of V _{j, k} , while for each value of m new values are formed

=

-K _{j, iV} $\genfrac{}{}{0ex}{}{\text{(d)}}{\text{j, K}}$ (i = 0 ÷ q). Moreover, at each step of the iteration, the discrepancy is
W _j = Δt

Z $\genfrac{}{}{0ex}{}{\text{2}}{\text{j}}$ _{, m}
Since in this case for all m 1-M, in equation (6) we have V _{j, k + ru} ^(d) 0, we obtain the following procedure of actions: put m 1, for a fixed m, the estimate V _{j, m} ^(d) is
V $\genfrac{}{}{0ex}{}{\text{(d)}}{\text{j, m}}$

K

K $\genfrac{}{}{0ex}{}{\text{2}}{\text{j}}$ _{, i} , We pass to the (q + 1) new values

by rule

=

- V $\genfrac{}{}{0ex}{}{\text{(d)}}{\text{j, r}}$ K _{j, i} (i = 0 ÷ q).

для последующих значений m 2, 3,M, а затем, снова повторяя всю итерационную процедуру, начиная с m=1 до m=M всего р раз, где практически достаточным оказывается ограничиться р=4, после чего остаточное значение W_j перестает уменьшаться, в результате получаем минимальное значение W_j,min.We repeat the indicated procedure for determining the estimates V _{j, m} ^(d) and

for subsequent values of m 2, 3, M, and then, repeating the entire iterative procedure again, starting from m = 1 to m = M only p times, where it is practically sufficient to limit p = 4, after which the residual value of W _j ceases to decrease, as a result, we obtain the minimum value of W _{j, min} .

K

t+

K $\genfrac{}{}{0ex}{}{\text{2}}{\text{j}}$ _,i, которую в каждый момент времени по ее получении, сдвинув ее (q+1) раз на интервалы времени τ_j,i и домножив соответственно на K_j,i (i=0÷q), вычитаем из соответствующих значений

(t+τ_j,i), переходя при этом к новым значениям по правилу

(t+τ_j,i)

(t+τ_j,i)-K_j,iV $\genfrac{}{}{0ex}{}{\text{(}}{\text{j}}$ ^d)(t+τ_j,i) (i= 0÷q). Указанная процедура пpоизводится при непрерывном изменении от 0 до Т_о и затем итерационно повторяется всего р раз (d 1÷p).Turning again to the case of continuous t, we obtain the following procedure: in the first cycle of calculation (d 1), we continuously calculate V _j ^(d) (t) as
V $\genfrac{}{}{0ex}{}{\text{(}}{\text{j}}$ ^d) (t)

K

t +

K $\genfrac{}{}{0ex}{}{\text{2}}{\text{j}}$ _{, i} , which at each time moment upon its receipt, by shifting it (q + 1) times by the time intervals τ _{j, i} and multiplying respectively by K _{j, i} (i = 0 ÷ q), we subtract from the corresponding values

(t + τ _{j, i} ), passing to the new values according to the rule

(t + τ _{j, i} )

(t + τ _{j, i} ) -K _{j, i} V $\genfrac{}{}{0ex}{}{\text{(}}{\text{j}}$ ^d) (t + τ _{j, i} ) (i = 0 ÷ q). The specified procedure is carried out with a continuous change from 0 to T _about and then iteratively repeated only p times (d 1 ÷ p).

The resulting values of Y _j 1 / W _{j, min} (j = 1 ÷ n) are indicators of the correspondence of the received atmospheric signal of the j-th range gradation. The values of Y _{j are} compared with each other, and the range L _b corresponding to the gradation of the range j = b, having the maximum output signal Y _b = Y _max = 1 / W _{b, min} = 1 / W _{min, min} , is taken as the distance to a lightning discharge.

 In FIG. Figure 3 shows the temporary form of the atmosphere, on which the Earth's and the first two ionospheric rays are visible.

1900 км.In FIG. 4 is a graph of the dependence of the values of Y _j on the corresponding ranges L _j (j 1 ÷ n). The graph is obtained as a result of digital signal processing, depicted in figure 3, in accordance with the proposed method. (For clarity, adjacent ordinates on the graph are connected by a continuous line). As can be seen from the graph, the maximum value of the output voltage Y _max = 1 / W _{min, min} processing channels was observed at L

1900 km.

 A one-point method for determining the distance to a lightning discharge source can be implemented in a device, a block diagram of which is shown in FIG.

The proposed ranging method includes the following sequence of operations: a) receive a lightning discharge signal, consisting of terrestrial and q ionospheric rays, to an omnidirectional electric antenna 1, b) amplify it in an amplifier 2, c) filter it in a wide frequency band using a filter 3 , d) delay it in time in the delay unit 4, e) carry out parallel n-channel processing of the analyzed signal in the processing channels (range gradations) 7-9, in which in each j-th (j = 1 ÷ n) channel: e ) form sequentially at every moment in belt t in the interval (0 + T _o ) the value of the auxiliary signal as a weighted average of the expected values of the rays in the analyzed signal at the expected distance L _j to the lightning source, g) form q + 1 value of the synthesized signal by (q + 1) - a multiple time shift of the value of the auxiliary signal by predetermined time intervals and multiplication of each shifted signal by predetermined coefficients, h) go to the new values of the analyzed signal by subtracting the time (q + 1) times and a signal derived from the analyzed values of the synthesized signal values, u) is repeated p times pp procedure ez, k) calculate the energy of the resulting analyzed signal at a predetermined time interval, l) in block 10 determine the range gradation corresponding to the minimum energy of the residual resulting signal, m) this range gradation is taken as the distance to the lightning discharge and displayed on indicator 11.

When implementing the proposed method of block ranging, it was established:
input filter bandwidth 5-35 kHz,
the duration of T _about equal to 140 μs,
the total duration of the signal processing interval was set to 700 μs, the used number of ionospheric rays is: q 2 at night at L _o 300 km, q 5 during the day at L _o 1500 km,
the delay time of the signal in the delay line is 70 μs,
the relative discrepancy between the range gradations to which neighboring gradations are tuned is ≈5% of the average range of these channels 2 (L _{j + 1} -L _j ) / (L _{j + 1} + L _j ) ≃ 0.05 (j 2 + n) , which leads to L ₁ L _min 300 km and L _n = L _max 2000 km to n = 40,
determination of the range gradation number having the maximum output signal is carried out according to the method described in [4]
Moreover, in the range of 300-2000 km, it was found that the relative error in the range estimate in the entire range of ranges does not exceed 10%, the time of measuring the range to the source of one atmosphere does not exceed 100 ms.

Claims (1)

METHOD FOR DETERMINING THE RANGE TO THE SOURCE OF THUNDER DISCHARGE, namely, that they receive a lightning discharge signal containing a vertical electric component, consisting of terrestrial and q ionospheric rays, onto an omnidirectional electric antenna, amplify the received signal, filter it in a wide frequency band and delay it in time, forming a signal Z (t), moreover, the filtered signal is compared with a threshold level and, when it is exceeded, the activity L to a lightning discharge source is determined, characterized in that it is delayed signal Z (t) is processed in n parallel range channels corresponding to n gradation range, wherein in each j-th (j 1 n) gradation range forming and storing an auxiliary signal _{Z j (t) Z (t} ), then sequentially to each the time t on the interval (t 0 T _o ), where T _{o the} expected duration of each of the rays, form a signal Q _j (t):

where τ _{j, i} and K _{j, i,} respectively, are the time interval known in advance and the ratio of amplitudes (taking into account their polarities) between the ith ionospheric (i 1 q) and the earth ray (τ _{j, o} = 0), (K _{j , o} 1), at a distance to the lightning discharge source corresponding to the jth gradation of the range LL _j , then the received signal Q _j (t) is shifted (q + 1) times by time intervals, respectively, τ _{j, i} (i = 0-q) multiply the obtained values by the corresponding coefficients K _{j , k} and subtract the values obtained from the corresponding values of Z _j (t) by the formula
Z _j (t + τ _{j, i} ) -K _{j, i} · Q _j (t) ⇒ Z _j (t + τ _{j, i} ),
repeat the specified processing sequence p times, using each time as the initial (at t 0) signal obtained in the previous measurement Z _j (t), the generated signal is squared, integrated over a given time interval 0 T _q , including earth and q ionospheric rays, calculate the inverse of this interval:

remember it, determine from all n channels of range gradation the one for which the value of V _{j is} maximum, and the range corresponding to this gradation is taken as the distance to the source of the analyzed lightning discharge.

Images