RU2456723C1 - Multifrequency antenna array for generation of radio pulse sequence in space - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: multifrequency antenna array comprises a system of generation of a coherent grid of equidistantly misaligned frequencies, N radiation elements (N>2), N controlled phase changers, a system of phase changer control, N balance mixers, N strip filters, a voltage-controlled generator, a generator of signals of arbitrary shape. Control inlets of phase changers are connected to the outlet of the phase changer control system, the outlets of the system of generation of the coherent frequency grid are connected to inlets of controlled phase changers so that signals with various frequencies are distributed along elements of the grid in accordance with a random law. Each outlet of a microwave signal of a controlled phase changer is connected to an inlet of a microwave signal of an appropriate balance mixer, besides, the outlet of the arbitrary shaped signal generator is connected to the inlet of the voltage-controlled generator, the outlet of which is connected with the appropriate inlet of the modulating signal of balance mixers.

EFFECT: development of a multifrequency antenna array with a frequency barrier in a specified frequency band when a sequence of radio pulses is radiated with specified duration and frequency of repetition.

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Description

The invention relates to radio engineering and can be used in electronic suppression systems using frequency-blocking interference.

A known device - "Scanning antenna" [1] with a monotonic change in the frequency of the signals by elements, designed for field scanning of the antenna radiation pattern (beam), which contains a coherent frequency network (SPS) and an equidistant linear antenna array (LAR), consisting of N radiating elements. The frequencies of the signals along the lattice elements from the 1st to the Nth are arranged in increasing or decreasing frequency, and the frequency discrete (minimum interval between the frequency components) Δf for any two adjacent elements of the LAR is a constant value. In this case, the phase difference between two adjacent elements of the LAR is 2πΔft rad (where t is the time), as a result of which an autoelectronic scanning of the beam occurs.

The main drawback that does not allow the use of this grating for the formation of a noise obstructing in frequency is the line spectrum of the emitted signal with a frequency discrete Δf. It is impossible to obstruct the frequency of interference, since the frequency band of the receiver of the suppressed device may be less than the frequency discrete Δf.

Common features of the analogue and the invention: the same elements of the scheme of the system for the formation of a coherent frequency grid (SPSCH) and the multi-frequency antenna array (MCHAR), as well as the principle of signal formation - a superposition of multi-frequency signals in space.

The closest in technical essence to the achieved result is MCAF for forming a sequence of pulsed signals in space [2], which is selected as a prototype of the invention, the structural diagram of which is shown in figure 1. The prototype contains a system for the formation of a coherent grid of equidistantly detuned frequencies (1), MCAR, which consists of N radiating elements (2) (N> 2), N controlled phase shifters (3), and phase shifter control systems (4). Moreover, the inputs of the radiating elements (2) are connected to the outputs of the controlled phase shifters (3), the control outputs of the phase shifters (3) are connected to the output of the phase shifter control system (4), the outputs of the coherent frequency grid formation system (1) are connected to the inputs of the controlled phase shifters (3) so that signals with different frequencies are distributed among the elements of the grating according to a random law. Due to the random distribution of signal frequencies among the aperture elements, the direction of the maximum of the beam formed by the MCAR is fixed in space (for N> 2).

The direction of the maximum of the bottom of the MCAA, like that of traditional phased antenna arrays (PAR), is determined by the deterministic phase distribution of the signal over the elements of the aperture and can be changed using controlled phase shifters (3). In this case, the width of the MCAA bottom in one plane at half power Θ≈λ _cp / D is determined by the average wavelength λ _{cp of the} multi-frequency signal and the linear aperture size of the MCAA in this plane is D. The pulse duration generated by the MCAA - τ _u depends on the multi-frequency bandwidth Δ _Fmax

The pulse repetition period T is inversely proportional to the frequency discrete T = 1 / Δf, and the pulse repetition frequency is equal to the frequency discrete. In this case, the duration and pulse repetition rate are independent of the size of the aperture and the random law of the distribution of signal frequencies over the emitters of the MCAR.

Figure 2 shows the two-dimensional space-time distribution (TAC) of the intensity and sequence of radio pulses generated by the prototype depending on the azimuthal angle, expressed in radians, and on time, expressed in nanoseconds. The calculations were performed for the distant radiation zone of the MCAR under the following initial conditions:

- flat MCA with the number of elements N = 5 × 5 and dimensions D × D = 2.5 × 2.5 m ² ;

- the working frequency band ΔF _max = 906-1194 MHz and the corresponding duration of the generated pulse τ _u = 3 ns;

- the value of the frequency discrete Δf = 12 MHz and the corresponding pulse repetition period T ~ 83.33 ns;

- the average frequency of the emitted signal f _cf = 1050 MHz.

The intensity of the total signal generated by the MCAR, consisting of isotropic elements, at any point in space can be determined by the following relation:

,

- сигналы, излучаемые j-м и m-м элементами МЧАР, соответственно;Where

,

- signals emitted by the j-th and m-th elements of the ICAR, respectively;

,

- комплексные передаточные функции среды распространения от j-го и m-го элементов МЧАР до заданной в пространстве точки;

,

- complex transfer functions of the propagation medium from the jth and mth elements of the MCAR to a given point in space;

N is the number of elements of the ICA;

Ψ _j , Ψ _m are the initial phases of the signals emitted by the elements of the ICAR;

Ψ _Гj = k _j r _j , Ψ _Гm = k _m r _m - phase incursions on the propagation path of signals from the jth and mth elements of the MCAR to a given point in space;

k _j , k _m - wave numbers;

r _j , r _m - the distance from the j-th and m-th elements of the ICAD to a given point in space;

ω _j, ω _m are the cyclic frequencies of the signals emitted by the jth and mth elements of the MCAR, ω _j = 2πf _j .

The cross-section of the TAC at the zero point in time, the plane parallel to the aperture, is the MCHAR bottom, and the cross-section of the TAC by the plane perpendicular to the axis of the MCHAR is the shape of the pulse signal generated by this grating.

Thus, the MCAR combines the functions of a radiating system and a spatial pulse modulator. The use of the MCAR for the spatial formation of broadband and ultra-wideband signals allows, firstly, to ensure the matching of the generators with the emitters, since each element of such an antenna is narrowband, and secondly, to form almost any given form of the phase-frequency characteristic of the MCAR, for example, linear.

The main disadvantage of the prototype, from the point of view of creating a barrage in frequency interference, is that the MCAAR generates in space a sequence of pulsed signals with a linear spectrum and a frequency discrete Δf equal to the pulse repetition rate.

The creation of a noise obstructing the frequency using the prototype is impossible, since the frequency band of the receiver of the suppressed device may be less than the frequency discrete Δf.

Figure 3 shows a fragment of the spectrum of the sequence of radio pulses formed by the prototype, the calculations are performed using the Fourier transform.

Common features of the invention and prototype: a system for forming a coherent grid of equidistant frequency detuned frequencies (SPSH) (1), N radiating elements (2), N controlled phase shifters (3), phase shifter control systems (4). In addition, the inputs of the radiating elements (2) are connected to the outputs of the controlled phase shifters (3), the control outputs of the phase shifters (3) are connected to the output of the phase shifter control system (4), the outputs of the SPSK system (1) are connected to the inputs of the controlled phase shifters (3) so, that signals with different frequencies are distributed among the grating elements according to a random law.

The technical result of the invention is the creation of the MCAR with a barrage in frequency interference in a given frequency band when emitting a sequence of radio pulses with a given duration and frequency of repetition.

The technical result of the invention is achieved due to the fact that all the different frequency signals emitted by the elements of the MCAR are modulated in frequency according to the same law, which can be both regular and random (for example, modulation with white noise). As a result, the MCAR emits pulsed signals with a swinging carrier frequency, which is one of the distinguishing features of the invention.

The invention is illustrated by drawings.

Figure 4 presents a block diagram of the inventive MCAR, which introduced the notation: 1 - system for the formation of a coherent frequency grid (SPSCH); 2 - emitters; 3 - controlled phase shifters (UV); 4 - control system of phase shifters (FMS); 5 - balanced mixer (BSm); 6 - band-pass filter (PF); 7 - voltage controlled oscillator (VCO); 8 - a signal generator of a given shape (GSF) with a band of the generated signal of not more than 10% of the frequency deviation.

Figure 5 shows the spatial-temporal distribution of the intensity of the sequence of radio pulses in a rectangular coordinate system, depending on the azimuthal angle, expressed in radians and in time, expressed in nanoseconds, formed by the claimed device. The intensity is normalized to the maximum.

Figure 6 shows a fragment of the frequency spectrum of a sequence of radio pulses generated by the claimed invention, calculated in the coordinates: frequency (in megahertz) - amplitude (normalized to the maximum value for a signal without a swinging carrier), the calculations were performed using the Fourier transform.

The technical result of the invention is achieved due to the fact that the MCAR contains: a system for generating a coherent frequency network (SPSC) 1, N emitters 2, where N is more than two, N controlled phase shifters (UV) 3, a control system for phase shifters (SUF) 4, N balanced mixers ( BSm) 5, N bandpass filters (PF) 6, a voltage controlled oscillator (VCO) 7 and an arbitrary waveform generator (GSF) 8 (Fig.4).

ICA can be performed linear, flat or conformal.

SPSCH 1 can be performed on the basis of, for example, standard frequency synthesizers VMK-2401 - VMK-2403 (developed by FSUE NIIPI Quartz), operating from a common reference generator, which can be used as a typical rubidium frequency standard.

The emitters 2 can be made in the form of, for example, spiral or horn antennas.

UV 3 can be performed, for example, ferrite with the input and output of the microwave signal and the input of the control signal.

SUF 4 can be performed on a computer basis.

BSm 5 can be performed according to the well-known mixer circuit with the input and output of the microwave signal and the input of the modulation signal.

PF 6 can be performed according to known schemes of bandpass filters with input and output of a microwave signal.

VCO 7 can be performed according to known schemes of voltage-controlled generators.

The signal generator of a given shape (GSF) 8 with a band of the generated signal of not more than 10% of the magnitude of the frequency deviation can be performed according to well-known schemes of generators, for example, sinusoidal signals, random signals or signals of a special shape.

N outputs SPSCH connected to the corresponding inputs of the microwave signals UV 3 randomly.

The output of the SUF 4 is connected to the corresponding input of the control signal of each UV 3.

Each output of the microwave signal UV 3 is connected to the input of the microwave signal of the corresponding BSm 5.

The output of the GSF 8 is connected to the input of the VCO 7, the output of which is connected to the input of the modulating signal of each BSM 5.

The outputs of the microwave signals BSm 5, through their PF 6 are connected to the inputs of the respective radiating elements 2.

MCHAR according to the invention works as follows (figure 4): coherent signals with frequencies f ₀₁ -f _0N (N is the number of elements of the MCHAR) generated by SPSCH 1, through UV 3 are fed to BSM 5, which are mixed with the signal from the output of VCO 7 having a frequency f ₀ + f _hm (t). The law by which the frequency f _hm (t) changes over time is determined by GSF 8. The maximum frequency deviation should not exceed half the minimum frequency sample. As a result, at the output of the j-th balanced mixer (j = 1 ... N), a signal appears whose spectrum consists of the combination frequencies f _0j ; ± (f ₀ + f _hm (t)); ± 2 (f ₀ + f _hm (t)); ...

At the outputs of BSm 5, PF 6 is turned on, which select, depending on the technical implementation conditions, a signal with a spectrum f _0j + f ₀ + f _hm (t) = f _j + f _hm (t) or f _0j -f ₀ -f _hm (t) = f _j -f _hm (t). Further, for definiteness, we will consider the signal of the upper sideband f _j + f _hm (t).

The signals from the PF outputs are fed to the inputs of the radiating elements (2) MCAR.

If f _hm (t) changes according to the sinusoidal law ω _FM (t) = ω _Д cosΩt, the signal strength E (t) with the jth frequency ω _j = 2πf _j created by the MCAR at some point in space can be represented without phase in the form:

,

,

where m = ω _d / Ω is the angular modulation index; ω _d - frequency deviation; Ω is the modulating frequency.

Expression (1) is expanded in the Fourier-Bessel series:

E _0j cos (J ₀ (m) cosω _j t + J ₁ (m) (cos (ω _j + Ω) t-cos (ω _j -Ω) t) -

-J ₂ (m) (cos (ω _j + 2Ω) t-cos (ω _j -2Ω) t) +

+ J ₃ (m) (cos (ω _j + 3Ω) t-cos (ω _j -3Ω) t) - ...)

where J _n (m) is the first-order Bessel function of the nth order of the argument m.

Thus, the frequency discreteness of the spectrum of the signal emitted by the MCAR will in this case be determined by the modulating frequency Ω. Obviously, if f _hm (t) varies according to the periodic law, then the discrete spectrum will be inversely proportional to the period. For a non-periodic law of variation of f _hm (t), the discrete will be determined by the minimum frequency in the spectrum of f _hm (t).

, поэтому можно говорить о сигнале с качающейся несущей частотой.In this case, since all signals with frequencies f _0j, coming from SFSCH are modulated to the same frequency at the same law, signals with frequencies f _j, radiated MCHAR remain coherent and hence not destroyed form the emitted pulse. The presence of frequency modulation in the elements of the MCAR allows one to generate pulse signals in space with a signal spectrum close to a solid and with a specified interval between adjacent spectral components much lower than the pulse repetition rate generated by the grating. If the signals emitted by the elements of the grating have the same amplitude, the carrier frequency of the pulse signal generated in space can be defined as

, therefore, we can talk about a signal with a swinging carrier frequency.

The space-time distribution of the intensity of the total signal generated by the inventive MCAR with a swinging carrier frequency depending on time and spatial coordinates, calculated under the same initial conditions as in figure 2, with the frequency modulation of all signal components according to a sinusoidal law with a modulating frequency Ω / 2π = 0.3 MHz and the deviation ω _d / 2π = 6 MHz is shown in Fig.5. The frequencies f _j of the signal spectrum are equal to the frequencies in FIG. 2.

A fragment of the frequency spectrum of the barrage during sinusoidal frequency modulation is shown in Fig.6. Comparison of the spectra in figure 2 and figure 6. shows that a device whose receiver band for this particular case is less than 6 MHz can without interference operate between the spectral components of the prototype, for example between frequencies f _j = 1038 MHz and f _{j + 1} = 1050 MHz (figure 2). At the same time, for the case of the MCAR with a swinging carrier frequency at Ω / 2π = 0.3 MHz, interference with a device with a receiver band greater than 0.3 MHz but less than 6 MHz is possible. Choosing the value of the modulating frequency during design, it is possible to achieve interference in an arbitrarily narrow band.

With noise-like modulation, the spectrum of the emitted signal is close to the continuous spectrum.

Multi-frequency antenna array (MCA) according to the invention is made flat in accordance with the structural diagram of Figure 4.

The number of radiating elements of the MCAR was selected N = 5 × 5 and the dimensions of its aperture D × D = 2.5 × 2.5 m.

The operating frequency band ΔF _max = 906-1194 MHz, the duration of the generated pulse τ _u = 3 ns.

The value of the frequency discrete Δf = 12 MHz and the corresponding pulse repetition period T ~ 83.33 ns.

The average frequency of the emitted signal f _cf = 1050 MHz.

The GSF 8 generator generates a sinusoidal waveform, the band of the generated signal is 8% of the frequency deviation.

SPSCH 1 is based on VMK-2401 frequency synthesizers operating from a common reference oscillator, which is used as a typical rubidium frequency standard of type A-1050.

The emitters 2 are made in the form of horn antennas from R&S with a gain of 10-14 dB and a wave impedance of 50 Ohms.

UV 3 is made in the form of discrete 6-section phase shifters with a minimum phase discrete of 5.5 degrees with switches on p-i-n diodes of type 2A561A-3, the switches are controlled by a computer.

SUF 4 is made on the basis of a computer, while the control of the CDMAR is carried out in software.

BSm 5 can be performed according to the known scheme with the input and output of the microwave signal and the input of the modulation signal.

PF 6 with a working bandwidth of at least 12 MHz at a level of -3 dB is based on half-wave and quarter-wave coaxial loops.

VCO 7 is made according to the well-known voltage-controlled generator circuit.

GSF 8 is made according to the well-known scheme of the random signal generator.

Due to the frequency modulation, the interval between adjacent frequency components of the spectrum emitted by the MCAR is determined by the minimum frequency in the spectrum of the _FM signal f (t) and is selected to be small as much as required to set a predetermined frequency-blocking interference.

In this case, since all signals with frequencies f _0j, coming from SFCHS 1 is modulated to the same frequency at the same law, so signals emitted MCHAR remain coherent.

The technical result of the invention is achieved, since the presence of frequency modulation in the elements of the MCAF allows you to generate pulse signals in space with a swinging carrier frequency and the interval between adjacent spectral components, much lower than the pulse repetition rate generated by the array, which allows you to create a frequency-blocking noise. In this case, frequency modulation does not destroy the shape of the pulse signal and does not change the position of the maximum of the beam in space.

Features of the invention

N balanced mixers (5), N bandpass filters (6), a voltage controlled oscillator (7), an arbitrary waveform generator (8) were introduced.

Each output of the microwave signal of the controlled phase shifter (3) is connected to the input of the microwave signal of the corresponding balanced mixer (5), in addition, the output of the arbitrary waveform generator (8) is connected to the input of the voltage controlled generator (7), the output of which is connected to the input of the modulation signal appropriate balance mixer (5).

The outputs of the microwave signals of balanced mixers (5) through their band-pass filters (6) are connected to the inputs of the corresponding radiating elements (2).

Information sources

1. Scanning Antenna, Application 2153076, France, publication 1973, June 1.

2. Vorobyov N.V., Gryaznov V.A. Multi-frequency antenna array for forming a sequence of pulsed signals in space: RU patent No. 2280930 according to the application 2004101937, H01Q 21/00. Priority from 2004.01.27.

Claims (1)

A multi-frequency antenna array consisting of a coherent grid formation system of equidistantly detuned frequencies, N radiating elements, where N is more than two, N controlled phase shifters, phase shifter control systems, the inputs of the phase shifter control signals being connected to the output of the phase shifter control system, the outputs of the coherent frequency grid forming system are connected with the inputs of the microwave signal of the phase shifters so that signals with different frequencies are distributed among the elements of the antenna array according to a random law y, characterized in that N balanced mixers, N bandpass filters, a voltage controlled oscillator, an arbitrary waveform generator are introduced into it, each output of a microwave signal of a controlled phase shifter connected to an microwave signal input of a corresponding balanced mixer, in addition, an output of an arbitrary signal generator the form is connected to the input of a voltage-controlled generator, the output of which is connected to the input of the modulation signal of the corresponding balanced mixer, and the outputs of the microwave signals of the balanced mixers through their bandpass filters are connected to the inputs of the respective radiating elements.

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