RU2696851C1 - Method of detecting objects of wireless information transmission networks - Google Patents

Abstract

FIELD: radar ranging.

SUBSTANCE: invention relates to methods and means for short-range radar ranging of nonlinear scattering radioelectronic objects, namely, to methods of detecting objects of wireless information transmission networks (WITN) hidden in near-surface layers of natural and artificial media and in passive mode. In order to improve characteristics of detecting objects of WITN against background of interference signals from inertia-free nonlinear scattering objects in a nonlinear radar, two radiation modes are used: in the first one – simultaneous emission of a pair of harmonic signals with frequencies f₁ and f₂ (fi < f₂) on time interval [0; T], and in the second one – simultaneous emission of the second pair of harmonic signals with frequencies f₁* and f₂* on time interval [T; 2T], wherein in both modes emitted frequencies are located symmetrically relative to central frequency f₀ of the input loop of the object of WITN, and their average values (f₁ + f₂)/2 and (f₁* + f₂*)/2 are selected to coincide with f₀: (f₁ + f₂)/2 = (f₁* + f₂*)/2 = f₀. Processing of reflected signal in nonlinear radar consists in separation of partial harmonic component at frequency 2f₀, determining amplitudes A and A* of said component with two radiation modes, respectively, and making a decision on detecting an object of the radio-frequency gain detector by comparing the difference of amplitudes A–A* with the threshold.

EFFECT: technical result is high efficiency of detecting objects of WITN.

1 cl, 3 dwg

Description

The invention relates to near-radar methods for searching and detecting nonlinearly scattering objects (NRA) hidden in the surface layers of natural and artificial environments. The implementation of these methods is carried out using the so-called non-linear radar (HP). Moving in the search process along the covering surface, HP gradually approaches the NRA, as a result of which an increase in the power of the reflected signal will be observed, indicating the presence of the NRA.

Many NRA can be divided into two groups:

- Inertia-free NRA, the equivalent electrical circuits of which contain only non-linear resistor elements. Typical representatives of inertia-free NRA are elements of steel structures, welded or riveted, subject to corrosion and rust;

- radio electronic NRA, the equivalent electrical circuits of which, in addition to non-linear resistor elements, also contain inertial elements - inductive and capacitive. A typical representative of electronic electronic NRAs is the objects of wireless information transmission networks (BSPI): mobile phones, electronic listening devices, receivers of radio-controlled fuses, etc., containing, in addition to the antenna, a receiver with an input frequency-selective circuit [1; p. 68, 78]. A nonlinear element in them are inertialess semiconductor devices (transistors) connected to the input circuit of the BSPI object with non-linear current-voltage characteristics (I – V characteristics). The central frequency f _{0 of the} input circuits of the BSPI objects and their bandwidth passing 2F for typical BSPI standards are known typical values [1; p. 41, 54, 71, 85]. In the proposed method, they are also considered known.

In the proposed method, it is precisely the BSPI objects that are in the passive (non-radiating) mode that represent the detection objects of interest to us, while the inertia-free LRAs are the sources of spurious interference components in the received HP signal.

Known methods for detecting inertialess NRFs [2], [3], in which the probing signal is the sum of two harmonic oscillations, and the amplitude of the reflected signal at combination frequencies is recorded in the HP receiver. The presence of combinational frequencies in the received HP signal is a consequence of the nonlinearity of the I – V characteristics of the resistor elements of inertia-free NRA. Analogue methods can in principle also be used for detecting BSPI objects.

The disadvantage of analogues is the low detection characteristics of the BSPI objects due to the high level of false alarms generated by the flow of false signals reflected from inertia-free LRAs.

Among the analogues closest to the proposed is the prototype method, in which it is carried out:

- generation and simultaneous emission of a pair of harmonic signals with frequencies f ₁ and f ₂ (f ₁ <f ₂ );

- among all possible combinational frequencies present in the spectrum of the reflected signal from the BSPI object, a harmonic signal with a combinational frequency f ₁ + f ₂ is allocated in the HP prototype receiver, which suggests the presence of a quadratic α ₂ U ² and / or other even components in the expansion of the I – V characteristic of the semiconductor element in a power row

where I and U are the current and voltage of the nonlinear element of the NRA.

The disadvantage of the prototype is the low detection characteristics of the BSPI objects against the background of a powerful stream of false signals from inertia-free NRAs.

The aim of the invention is to increase the efficiency of detection of objects BSPI.

To achieve this goal in the prototype method, in which the first radiation mode of the probe signal is implemented, which consists in simultaneously emitting a pair of harmonic signals with frequencies f ₁ and f ₂ (f ₁ <f ₂ ) for a time interval [0; T] with restriction

where F is the bandwidth of passing the input circuit of the BSPI object, receiving the reflected signal, highlighting in the spectrum of the received signal the partial harmonic component at the combination frequency f ₁ + f ₂ and determining the amplitude A of this component, an additional radiation mode of the probing signal is performed, consisting in simultaneous emission the second pair of harmonic signals with frequencies f ₁ * and f ₂ * on the time interval [T; 2T] with restriction

determining the amplitude A * of the partial harmonic component in the spectrum of the received signal at the combination frequency f ₁ * + f ₂ * in the second radiation mode, calculating the difference A-A * with its further comparison with the threshold, and in both modes the emitted frequencies are located symmetrically with respect to the center frequency f _{0 of the} input circuit of the BSPI object, and their average values (f ₁ + f ₂ ) / 2 and (f ₁ * + f ₂ *) / 2 are selected to coincide with the central frequency f _{0 of the} input circuit of the BSPI object:

In FIG. 1 shows a simplified functional diagram of HP that implements the proposed method, elements 1-4 of which carry the following technical contents: 1 - key diagram: 2 - HP receiver containing a sampling and storage unit; 3 - delay device for time T; 4 is a subtraction scheme.

In FIG. 2 shows a time-frequency diagram of an HP radiated signal.

In FIG. 3 shows the location of the emitted frequencies in two modes of HP radiation and the frequency 2f ₀ allocated in the HP receiver and the amplitude-frequency characteristic (AFC) of the input circuit of the BSPI object.

The functioning of the proposed method is as follows. For brevity, the 1st radiation mode will be called the simultaneous emission of a pair of harmonic signals with frequencies f ₁ and f ₂ respectively in the time interval [0; T], and the simultaneous emission of a second pair of harmonic signals with frequencies f ₁ * and f ₂ * in the time interval [T; 2T] - we will call the 2nd radiation mode. In FIG. 1, the signal emitted in the 1st mode is denoted as S, and the emitted in the 2nd mode is denoted as S *. In both modes, the emitted frequencies are located symmetrically relative to the center frequency f _{0 of the} input circuit of the object BSPI. In the 1st mode, both emitted frequencies f ₁ and f ₂ are located in the strip of the input circuit of the BSPI object, and in the 2nd mode, both emitted frequencies f ₁ * and f ₂ * are located outside the strip of the input circuit of the BSPI object. Therefore, with the 1st radiation mode, the amplitude A of the signal reflected from the BSPI object will be significantly larger than the amplitude A * with the 2nd radiation mode.

Switching with a period T of the radiation and reception modes is performed using the key circuit 1 of FIG. 1, which has two inputs: one signal receives the signal S, and the second signal S *. The HP receiver 2 of FIG. 1 selects from the reflected signal arriving at its input a harmonic frequency oscillation 2f ₀ with fixing the amplitude of this oscillation at the end of the corresponding radiation mode: amplitude A at time t = T for the 1st radiation mode and amplitude A * at time t = 2T for the 2nd radiation mode. To fix the amplitudes A and A *, you can use the sampling and storage units [4, p. 154], controlled by the same signals that control the key circuit 1. Key circuit 1 has two outputs: the voltage at one output is proportional to the amplitude A, and at the other - amplitude A *. In order to be able to compare the amplitudes A and A * and determine, using the subtraction scheme 4, their difference (A-A *) in the circuit of FIG. 1, a delay device 3 is included, which delays the countdown of A by time T. Another possibility of fixing the amplitudes A and A * and determining their difference (A-A *) consists in the use of microprocessors [5; p. 183] with the preliminary analog-to-digital conversion of the output signal of the HP receiver [5 p. 239].

In the difference value (A-A *), the interference components from the inertia-free NRA present in the reflected signal are compensated. In the future, the difference (AA *) is compared with the threshold for deciding on the detection of an object BSPI.

Information sources:

1. Vishnevsky V.M., Lyakhov A.I., Tailor S.L., Shakhnovich I.V. Broadband wireless data networks. Moscow: Technosphere, 2005

2. Musabekov P.M., Panychev S.N. Non-linear radar: methods, techniques and scope. Foreign radio electronics, Advances in modern radio electronics, 2000, No. 5, p. 54 ÷ 61.

3. Belyaev V.V., Mayunov A.T., Razinkov S.N. Status and development prospects of "non-linear" radar. Successes of modern radar, 2002, No. 6, p. 59-78.

4. Keleksaev B.G. Nonlinear converters and their application. Solon-R, Moscow, 1999

5. Gutnikov B.C. Integrated electronics in measuring devices. Energoatomizdat. Leningra. Department, 1988

Claims (2)

The method of radar detection of objects of wireless information transmission networks (BSPI), in which the first radiation mode of the probe signal is implemented, which consists in simultaneously emitting a pair of harmonic signals with frequencies f ₁ and f ₂ (f ₁ <f ₂ ) in the time interval [0; T] with the restriction (f ₂ -f ₁ ) ≤2 (F-1 / Т), where F is the bandwidth of the input circuit of the BSPI object, receiving the reflected signal, highlighting in the spectrum of the received signal the partial harmonic component at the combination frequency f ₁ + f ₂ and determining the amplitude A of this component, characterized in that the second radiation mode of the probe signal is additionally carried out, which consists in simultaneously emitting a second pair of harmonic signals with frequencies f ₁ * and f ₂ * in the time interval [T; 2T] with restriction 2 (F + 1 / T) ≤ (f ₂ * -f ₁ *), determination of the amplitude A * of the partial harmonic component in the spectrum of the received signal at the combination frequency f ₁ * + f ₂ * in the second radiation mode, calculation the difference A-A * with its further comparison with the threshold, and in both modes the emitted frequencies are located symmetrically with respect to the center frequency f _{0 of the} input circuit of the BSPI object, and their average values (f ₁ + f ₂ ) / 2 and (f ₁ * + f ₂ *) / 2 are chosen to coincide with the frequency f ₀ : (f ₁ + f ₂ ) / 2 = (f ₁ * + f ₂ *) / 2 = f ₀ .

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