CN105044689A - Frequency-controlled array-based RF stealth method and device - Google Patents

Abstract

The invention discloses a radio frequency stealth method based on a frequency control array, comprising: transmitting a carrier signal sequence to a target object, each carrier signal in the carrier signal sequence has a low gain, and each adjacent carrier signal has a specific frequency difference; receiving the echo signal sequence of the target object; and synthesizing the echo signal sequence into a high-gain antenna pattern through beamforming. The invention also discloses a radio frequency stealth device based on the frequency control array. The radio frequency stealth method and equipment based on the frequency control array of the present invention replace the traditional high-gain antenna pattern covering the desired monitoring area with a series of low-gain antenna pattern, because the peak power of the low-gain antenna pattern is relatively low, Therefore, the radar visibility is reduced while the radar monitoring performance remains unchanged, that is, better low probability of intercept (LPI) performance is provided.

Description

A radio frequency stealth method and device based on frequency control array

technical field

The invention relates to the technical field of electronic countermeasures, and in particular designs a radio frequency stealth method and equipment based on a frequency control array.

Background technique

With the development of modern military science and technology, electronic jamming and anti-jamming related to radar has become one of the focuses of future battlefield competition. In view of the increasingly complex situation of radar application environment, the radar's radio frequency stealth ability has a greater impact. Urgent needs. Under the premise of ensuring the detection capability of the radar, it is necessary to reduce the visibility of the radar and enhance its LPI (Low Probability of Interception) capability to gain the initiative. This is of great significance for improving the radar's anti-reconnaissance capability and self-survivability.

Currently commonly used techniques can be divided into three areas: 1) frequency domain with large bandwidth waveforms that propagate energy; 2) time domain with high duty cycle waveforms that propagate energy; 3) air domain with wide antenna beam patterns that propagate energy. These techniques are often combined to ensure LPI properties, however, the transmitted energy is limited. For example, frequency hopping techniques, Orthogonal Frequency Division Multiplexing (OFDM) and random waveforms have been studied in LPI radars.

Additionally, a method of antenna frequency hopping employs an irregular scan pattern to reduce receiver susceptibility to radar. Although the probability of being detected in the side lobe region can be reduced by specific beamforming techniques, the high-gain main lobe can still be easily detected. Therefore, it is necessary to reduce the instantaneous transmit peak power to the potential interceptor. At present, a relatively novel LPI transmit beamforming method is to use a phased array antenna. Although phased arrays are used in many fields, the beam pointing corresponding to all distances is fixed at an angle.

Contents of the invention

To this end, the present invention proposes a novel radio frequency stealth method and device based on a frequency control array that can solve at least part of the above-mentioned problems.

According to one aspect of the present invention, a radio frequency stealth method based on a frequency control array is provided, including: transmitting a carrier signal sequence to a target object, each carrier signal in the carrier signal sequence has a low gain, and each adjacent There is a specific frequency difference between the carrier signals; the echo signal sequence of the target object is received; and the echo signal sequence is synthesized into a high-gain antenna pattern through beamforming.

Optionally, according to the method of the present invention, wherein transmitting a carrier signal sequence to the target object, each carrier signal in the carrier signal sequence has a low gain, and each adjacent carrier signal has a specific frequency difference includes : According to the array elements of the frequency control array of the radar, the carrier signal sequence is transmitted; the frequency of the array element transmitting the carrier signal is obtained according to the carrier frequency and the frequency increment satisfying specific conditions; the array element is transmitted according to the frequency of the array element. The phase difference between the mth array element and the first array element that transmits the carrier signal; obtain the basic low-gain antenna pattern for transmitting the carrier signal according to the phase difference; and obtain the basic low-gain antenna pattern according to the basic low-gain antenna pattern A linear phase increase obtains a low-gain antenna pattern.

Optionally, according to the method of the present invention, the equation of the frequency at which the array element transmits the carrier signal is: f _m =f ₀ +Δf _m , m=0,1,...,M-1

Among them, Δf _m is the frequency increment, f ₀ is the carrier frequency, and f _m is the frequency at which the mth array element transmits the carrier signal;

The specified conditions are:

$\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; \{</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; .</span>$

Among them, T _P is the continuous processing time, 2ξsinθ is the length of the target object projected to the radar aiming direction, and ξ is the length of the target object.

Optionally, according to the method of the present invention, wherein, the phase difference between the mth array element and the first array element where the array element transmits the carrier signal is: $\begin{array}{c}{\mathrm{\&Theta;}}_m^{\&prime;}(r,\mathrm{\&theta;})={\mathrm{\&psi;}}_m^{\&prime;}(r,\mathrm{\&theta;})-{\mathrm{\&psi;}}_0^{\&prime;}(r,\mathrm{\&theta;})\\ =-\mathrm{\&beta;}{f}_0\mathrm{md}\sin \mathrm{\&theta;}+\mathrm{\&beta;m\&Delta;}{f}_{m}d\sin \mathrm{\&theta;}\end{array},$

Among them, r is the slant distance, θ is the azimuth angle, β=2π/c ₀ , d is the array element spacing, d=c ₀ /2f ₀ ;

The basic low-gain antenna pattern is: $a_0^{\&prime;}(r,\mathrm{\&theta;})=\underset{m=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{e}^{-\mathrm{jm\&beta;}{f}_{0}d\sin \mathrm{\&theta;}}{e}^{\mathrm{j\&beta;}{\mathrm{\&Delta;f}}_{m}r}{e}^{-j{\mathrm{\&alpha;}}_m\left(r\right)}{e}^{-\mathrm{jm\&beta;}{\mathrm{\&Delta;f}}_{m}d\sin \mathrm{\&theta;}}$

where {α _m (r)} is a distance-dependent phase set.

Optionally, according to the method of the present invention, wherein the low-gain antenna pattern is:

Wherein, a linear phase increase is performed on the basic low-gain antenna pattern, the increment of the first low-gain antenna pattern is γ=2π/N, the second increment is 2γ, and so on, Additional N-1 low-gain antenna patterns can be obtained.

Optionally, according to the method of the present invention, wherein receiving the echo signal sequence of the target object includes: the reflected carrier signal sequence is received by the elements of the phased array of the radar after being echoed by the target object and passed through The matched filter is processed and stored in memory.

Optionally, according to the method of the present invention, wherein, combining the echo signal sequence into a high-gain antenna pattern through beamforming includes: obtaining a weight coefficient of a low-gain antenna pattern of the carrier signal according to an MVDR beamforming criterion; The high-gain antenna pattern is obtained according to the linear combination of the low-gain antenna pattern.

Optionally, according to the method of the present invention, wherein the high-gain antenna pattern is:

Wherein, N represents the number of low-gain antenna patterns, w _0,n is the weight of the n-th low-gain antenna pattern to obtain w _0,N-1 is the weight of the N-1th low-gain antenna pattern.

Optionally, according to the method of the present invention, wherein,

The weight coefficients are:

in,

According to another aspect of the present invention, the present invention also provides a radio frequency stealth device based on a frequency control array, including:

a transmitting device, configured to transmit a carrier signal sequence to a target object, each carrier signal in the carrier signal sequence has a low gain, and each adjacent carrier signal has a specific frequency difference;

a receiving device, configured to receive the echo signal sequence of the target object; and

A synthesizing device is used for synthesizing the echo signal sequence into a high-gain antenna pattern through beamforming.

The radio frequency stealth method and equipment based on the frequency control array of the present invention replace the traditional high-gain antenna pattern covering the desired monitoring area with a series of low-gain antenna pattern, because the peak power of the low-gain antenna pattern is relatively low, Therefore, the radar visibility is reduced while the radar monitoring performance remains unchanged, that is, better low probability of intercept (LPI) performance is provided.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Also throughout the drawings, the same reference numerals are used to designate the same components. Wherein in the drawings, letter marks after reference numerals indicate a plurality of identical components, and when referring to these components generally, the last letter marks thereof will be omitted. In the attached picture:

Fig. 1 is the flow chart of the radio frequency stealth method based on the frequency control array of the present invention;

Figure 2 is a schematic diagram of a frequency control array;

Fig. 3 is the schematic diagram that the array element of the frequency control array of the present invention transmits the carrier signal sequence and the array element of the phased array receives the echo signal sequence;

Figure 4 is a comparative schematic diagram of a low-gain antenna pattern (dotted line) and a high-gain antenna pattern (solid line) formed in the angular domain when the slant distance r=20km;

Fig. 5 is a comparative schematic diagram of a low-gain antenna pattern (dotted line) and a formed high-gain antenna pattern (solid line) in the distance domain when the azimuth angle θ=0°;

6 is a schematic structural diagram of a radio frequency stealth device based on a frequency control array according to the present invention; and

Figure 7 shows a block diagram of a computing device that may be used to practice embodiments of the invention.

In the drawings, the same or similar reference numerals are used to refer to the same or similar elements.

Detailed ways

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the implementations shown and described in the drawings are only exemplary, intended to explain the principle and spirit of the present invention, rather than limit the scope of the present invention.

Fig. 1 shows a flow chart of the method for constructing an audio fingerprint library according to the present invention. It can be understood that the flowchart shown in FIG. 1 is only schematic, and the steps recorded therein can be executed in different orders, executed in parallel, omitted and/or added with other steps. As shown in Figure 1, the radio frequency stealth method based on the frequency control array includes: transmitting a carrier signal sequence to the target object, each carrier signal in the carrier signal sequence has a low gain, and the distance between each adjacent carrier signal is having a specific frequency difference 102; receiving the echo signal sequence 104 of the target object; and synthesizing the echo signal sequence into a high-gain antenna pattern 106 through beamforming. The radio frequency stealth method and equipment based on the frequency control array of the present invention replace the traditional high-gain antenna pattern covering the desired monitoring area with a series of low-gain antenna pattern, because the peak power of the low-gain antenna pattern is relatively low, Therefore, the radar visibility is reduced while the radar monitoring performance remains unchanged, that is, better low probability of intercept (LPI) performance is provided.

The step 102 includes transmitting the carrier signal sequence according to the array element of the frequency control array of the radar; obtaining the frequency of the array element transmitting the carrier signal according to the carrier frequency and the frequency increment satisfying the specific condition; according to the array element transmitting the carrier signal frequency Obtaining the phase difference between the mth array element and the first array element transmitting the carrier signal by the array element; acquiring the basic low-gain antenna pattern for transmitting the carrier signal according to the phase difference; and obtaining the basic low-gain antenna pattern according to the basic low-gain Antenna pattern A low-gain antenna pattern is obtained by linearly increasing the phase. Fig. 3 shows a schematic diagram of the carrier signal sequence transmitted by the array elements of the frequency control array and the echo signal sequence received by the array elements of the phased array according to the present invention.

The selection of the frequency increment in the present invention is to create a low-gain antenna pattern in the angle dimension, and a low-gain antenna pattern means to generate a wide beam. The frequency increment can be a linear frequency increment, or a nonlinear frequency increment, and a nonlinear frequency increment is preferred in the present invention.

In the present invention, the carrier frequency of the frequency control array of the radar is f ₀ , assuming that a frequency control array of M array elements uniform linear array (ULA) transmits pulses, that is, baseband waveforms, and the receiving end is a phased array of M array elements. The element spacing of both the transmitting and receiving arrays is designed as d=c ₀ /2f ₀ . Additive noise is modeled as a complex Gaussian zero-mean white noise with equal variance across the array.

Assuming that the frequency increment of the m-th array element is Δf _m , then the frequency of the m-th array element transmitting pulses is:

f _m ＝f ₀ +Δf _m , m=0,1,...,M-1

Figure 2 shows a schematic diagram of a frequency steered array (FDA). As shown in FIG. 2 , when Δf _m =mΔf, that is, when the frequency increment is a linear frequency increment, a conventional frequency-steered array is obtained.

Specific conditions for frequency increments are given below, which should satisfy in order to avoid signal de-correlation:

where T _P is the continuous processing time.

In addition, in order to avoid the de-correlation of the frequency of the target object, the frequency increment must satisfy:

Among them, 2ξsinθ is the length of the target projected to the radar aiming direction, and ξ is the length of the target.

The frequency increment further satisfies Δf _m >0, so the specific condition, that is, the optional range of Δf _m is:

$\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; \{</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>$

The optimized frequency increment satisfies: βΔf _m dsinθ=φ _m and β(Δf _{m −mΔf} )r-α _m (r)=φ _m , where the set {Δf _m } and {α _m (r)}, that is, the optimized frequency increment and the optimized distance-dependent phase set.

When the slant distance is r, the phase of the carrier signal transmitted by the mth array element can be expressed as:

ψ′ _m (r,θ)=(f ₀ +Δf _m )(r−mdsinθ)β, where β=2π/c ₀ , d=c ₀ /2f ₀ .

Then, the phase difference between the carrier signal transmitted by the mth array element and the carrier signal transmitted by the first array element is:

Θ' _m (r, θ) = ψ' _m (r, θ) - ψ' ₀ (r, θ)

=-βf ₀ mdsinθ+βmΔf _m dsinθ.

In this case, when uniform excitation is used, the low-gain antenna pattern with a slant distance of r is:

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jm\&beta;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j\&beta;</span>}{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jm\&beta;</span>}{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; .</span>$

Thus, the basic low-gain antenna pattern is obtained as:

$a_0^{\&prime;}(r,\mathrm{\&theta;})=\underset{m=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{e}^{-\mathrm{jm\&beta;}{f}_{0}d\sin \mathrm{\&theta;}}{e}^{\mathrm{j\&beta;}{\mathrm{\&Delta;f}}_{m}r}{e}^{-j{\mathrm{\&alpha;}}_m\left(r\right)}{e}^{-\mathrm{jm\&beta;}{\mathrm{\&Delta;f}}_{m}d\sin \mathrm{\&theta;}},$ where {α _m (r)} is a distance-dependent phase set.

Obtaining a low-gain antenna pattern according to the basic low-gain antenna pattern, where the low-gain antenna pattern is:

Wherein, a linear phase increase is performed on the basic low-gain antenna pattern, the increment of the first low-gain antenna pattern is γ=2π/N, the second increment is 2γ, and so on, Additional N-1 low-gain antenna patterns can be obtained.

The low-gain antenna patterns exhibit wide beams, so their peak power is significantly reduced in any direction to ensure low probability of intercept (LPI) characteristics.

In the radio frequency stealth method based on the frequency control array of the present invention, the step 104 of receiving the echo signal sequence of the target object includes: the reflected carrier signal sequence is echoed by the target object and then controlled by the phase of the radar The array elements are received and processed by a matched filter and stored in memory. After the array element of the frequency control array of the radar transmits the carrier signal sequence to the target object, it is echoed by the target object, and the echo signal sequence is received by the array element of the phased array of the radar, and the echo signal sequence is passed through a matched filter. Stored in memory after processing.

In the radio frequency stealth method based on the frequency control array of the present invention, the step 106 includes: obtaining the weight coefficient of the low-gain antenna pattern of the carrier signal according to the MVDR beamforming criterion; linearly combining the low-gain antenna pattern according to the Get high gain antenna pattern.

In order to keep the performance of the radar unchanged while ensuring the LPI characteristics, the present invention synthesizes the high-gain antenna pattern by linearly combining the basic low-gain antenna pattern.

w _0,n is the weight of the nth low-gain antenna pattern, so that the corresponding high-gain antenna pattern is obtained as:

${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>$

Similarly, high-gain antenna patterns for other scans can be obtained with appropriate weights:

Expressed in compact matrix form as:

When a signal source is received in the background of Gaussian white noise, according to the MVDR beamforming rule, the steering vector a(r, θ) and the weight vector w should satisfy w ^H a(r, θ)=1, where ^H represents the total Yoke transpose operation.

Therefore, the weighting coefficients in the high-gain antenna pattern should satisfy the following relationship:

$A.\left[\begin{array}{c}{w}_{\mathrm{0,0}}\\ w_{\mathrm{0,1}}\\ \\ \\ \\ w_{0,N-1}\end{array}\right]=\left[\begin{array}{c}1\\ 1\\ .\\ .\\ .\\ 1\end{array}\right],$ in,

A similar relationship can be obtained in the weight coefficient of A _n (r, θ):

$\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; .</span>\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; 1</span>}\\ {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; jn\&gamma;</span>}}\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; jn</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}\end{array}\right]<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; .</span>$

In this way, one can get

Among them, ^-1 represents the inverse matrix.

It can be seen from the weight coefficient that the high-gain antenna pattern is determined to be formed according to the linear combination of the low-gain antenna pattern.

According to the technical scheme of the radio frequency stealth method based on the frequency control array of the present invention, the specific implementation is as follows:

Taking an LPIFDA (frequency control array) radar with a carrier frequency of f ₀ =10GHz as an example, suppose a 32-element uniform linear array (ULA) frequency control array sends a carrier signal sequence, and the receiving end is a 32-element phased array . The element spacing of both the transmitting and receiving arrays is designed as d=c ₀ /2f ₀ =0.015m. Additive noise is modeled as a complex Gaussian zero-mean white noise with equal variance across the array.

The slant distance is r=20km, and the frequency increment is obtained by a quadratic phase change: {Δf ₁ , Δf ₂ ,...,Δf ₁₆ }={5.999kHz, 2.7659kHz, 1.5695kHz, 1.0395kHz, 686.2936kHz, 479.9675kHz, 352.2838kHz, 248.0967kHz, 177.3543kHz, 120.7485kHz, 79.9319kHz, 48.7352kHz, 28.1722kHz, 16.2372kHz, 6.5572kHz, 1.4876kHz}

Wherein, the values of Δf ₁₇ to Δf ₃₂ are the reverse order of Δf ₀ to Δf ₁₆ .

The phase equation of the carrier signal transmitted by the elements of the radar frequency control array is obtained from the frequency increment, the basic low-gain antenna pattern of the carrier signal is obtained according to the phase difference, and the basic low-gain antenna pattern is obtained by linear phase increase according to the basic low-gain antenna pattern Low gain antenna pattern.

The high-gain antenna pattern is obtained according to the calculated weighting coefficients, and the high-gain antenna pattern is generated by linearly combining 32 low-gain antenna patterns.

Fig. 4 shows a schematic diagram comparing the low-gain antenna pattern (dotted line) and the formed high-gain antenna pattern (solid line) in the angle domain when the slant distance r=20km. Fig. 5 shows a schematic diagram comparing the low-gain antenna pattern (dotted line) and the formed high-gain antenna pattern (solid line) in the distance domain when the azimuth angle θ=0°.

FIG. 6 is a schematic structural diagram of a radio frequency stealth device based on a frequency control array according to the present invention. As shown in Fig. 6, the radio frequency stealth equipment based on the frequency control array includes: a transmitting device 20, a receiving device 21 and a synthesizing device 22, wherein the transmitting device 20 is used to transmit a carrier signal sequence to a target object, and the carrier Each carrier signal in the signal sequence has a low gain, and there is a specific frequency difference between each adjacent carrier signal; the receiving device 21 is used to receive the echo signal sequence of the target object; the synthesizing device 22 It is used for synthesizing the echo signal sequence into a high-gain antenna pattern through beamforming.

Figure 7 shows a block diagram of an exemplary computing device that may be used to practice embodiments of the present invention. It can be appreciated that the client, proxy and/or server described in this disclosure can be implemented using the computing device shown in FIG. 7 . As shown in Figure 7, the computing device may include: CPU (Central Processing Unit) 401, RAM (Random Access Memory) 402, ROM (Read Only Memory) 403, system bus 404, hard disk controller 405, keyboard controller 406, Serial interface controller 407 , parallel interface controller 408 , display controller 409 , hard disk 410 , keyboard 411 , serial peripheral 412 , parallel peripheral 413 and display 414 . Among these components, coupled to the system bus 404 are a CPU 401 , a RAM 402 , a ROM 403 , a hard disk controller 405 , a keyboard controller 406 , a serial interface controller 407 , a parallel interface controller 408 and a display controller 409 . Hard disk 410 is coupled with hard disk controller 405, keyboard 411 is coupled with keyboard controller 406, serial peripheral device 412 is coupled with serial interface controller 407, parallel peripheral device 413 is coupled with parallel interface controller 408, and display 414 is coupled with display control device 409 coupling.

The radio frequency stealth method and equipment based on the frequency control array of the present invention replace the traditional high-gain antenna pattern covering the desired monitoring area with a series of low-gain antenna pattern, because the peak power of the low-gain antenna pattern is relatively low, Therefore, the radar visibility is reduced while the radar monitoring performance remains unchanged, that is, better low probability of intercept (LPI) performance is provided.

Several embodiments of the invention have been described above by way of example. At least some of the various blocks, operations, and techniques described above may be performed using hardware, a processor executing firmware instructions, a processor executing software instructions, or any combination thereof. When executed with a processor executing firmware and software instructions, the software or firmware instructions may be stored in any computer-readable storage, such as a magnetic disk, optical disk or other storage medium, in a RAM or ROM or flash memory, processor, hard disk , discs, disks and more. Likewise, software and firmware instructions may be transmitted to the user or system by any known or desired transmission means including, for example, on a computer readable disk or other portable computer storage mechanism or via a communication medium. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism. By way of example, and not limitation, communication media includes wired media such as a wired network or a single-wire connection, and wireless media such as acoustic, radio frequency, infrared and other wireless media. Thus, software and firmware instructions may be transmitted to a user or system over a communication channel, such as a telephone line, DSL line, cable television line, fiber optic cable, wireless channel, the Internet, etc. (providing such software via a portable storage medium, are considered the same or interchangeable). Software or firmware instructions may include other readable instructions which, when executed by a processor, cause the processor to perform various actions.

It should be noted that the embodiments of the present invention can be realized by software, hardware, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in memory and executed by a suitable instruction execution system such as a microprocessor or specially designed hardware. Those of ordinary skill in the art will understand the methods and systems described above and may implement them using computer-executable instructions and/or contained in processor control code, for example on a carrier medium such as a disk, CD or DVD-ROM, such as a read-only Such code is provided on a programmable memory of memory (firmware) or on a data carrier such as an optical or electronic signal carrier. The device and its modules in this embodiment can be implemented by hardware circuits such as VLSI or gate arrays, semiconductors such as logic chips and transistors, or programmable hardware devices such as field programmable gate arrays and programmable logic devices. , can also be implemented by software executed by various types of processors, or can be implemented by a combination of the above hardware circuits and software, such as firmware.

The communication network mentioned in the description may include various types of networks, including but not limited to local area network ("LAN"), wide area network ("WAN"), network based on IP protocol (such as Internet) and peer-to-peer network (such as adhoc peer-to-peer network).

In addition, while operations of the methods of the present invention are depicted in the figures in a particular order, there is no requirement or implication that these operations must be performed in that particular order, or that all illustrated operations must be performed, to achieve desirable results. Conversely, the steps depicted in the flowcharts may be performed in an altered order. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, or one step may be broken down into multiple steps.

While the invention has been described with reference to several specific embodiments, it is to be understood that the invention is not limited to the specific embodiments disclosed. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the appended claims is to be accorded the broadest interpretation thereby encompassing all such modifications and equivalent structures and functions.

Claims (10)

1. A radio frequency stealth method based on frequency control array, comprising: transmitting a sequence of carrier signals to the target object, each carrier signal in the sequence of carrier signals having a low gain and having a specific frequency difference between each adjacent carrier signal; receiving a sequence of echo signals of the target object; and The echo signal sequence is synthesized into a high-gain antenna pattern through beamforming. 2. The method according to claim 1, wherein a sequence of carrier signals is transmitted to the target object, each carrier signal in the sequence of carrier signals has a low gain, and each adjacent carrier signal has a specific frequency difference include: The carrier signal sequence is transmitted according to the elements of the frequency control array of the radar; obtaining the frequency at which the array element transmits the carrier signal according to the carrier frequency and the frequency increment satisfying a specific condition; Acquiring the phase difference between the mth array element and the first array element of the array element transmitting the carrier signal according to the frequency of the array element transmitting carrier signal; obtaining a basic low-gain antenna pattern for transmitting carrier signals according to the phase difference; and obtaining a low-gain antenna pattern through linear phase increase according to the basic low-gain antenna pattern. 3. The method according to claim 2, wherein, the equation of the frequency of the array element transmitting the carrier signal is: f _m = f ₀ +Δf _m , m=0, 1, ..., M-1 Among them, Δf _m is the frequency increment, f ₀ is the carrier frequency, and f _m is the frequency at which the mth array element transmits the carrier signal; The specified conditions are: $\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; \{</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; .</span>$ Among them, T _P is the continuous processing time, 2ξsinθ is the length of the target object projected to the radar aiming direction, and ξ is the length of the target object. 4. The method of claim 2, wherein, The phase difference between the mth array element and the first array element transmitting the carrier signal by the array element is: Θ′ _m (r, θ)=ψ′ _m (r, θ)-ψ′ ₀ (r, θ) ＝-βf ₀ mdsinθ+βmΔf _m dsinθ Among them, r is the slant distance, θ is the azimuth angle, β=2π/c ₀ , d is the array element spacing, d=c ₀ /2f ₀ ; The basic low-gain antenna pattern is: $a_0^{\&prime;}(r,\mathrm{\&theta;})=\underset{m=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{e}^{-\mathrm{jm\&beta;}{f}_{0}d\sin \mathrm{\&theta;}}{e}^{\mathrm{j\&beta;\&Delta;}{f}_{m}r}{e}^{-j{\mathrm{\&alpha;}}_m\left(r\right)}{e}^{-\mathrm{jm\&beta;\&Delta;}{f}_{m}d\sin \mathrm{\&theta;}}$ where {α _m (r)} is a distance-dependent phase set. 5. The method of claim 2, wherein, The pattern of the low-gain antenna is: Wherein, a linear phase increase is performed on the basic low-gain antenna pattern, the increment of the first low-gain antenna pattern is γ=2π/N, the second increment is 2γ, and so on, Additional N-1 low-gain antenna patterns can be obtained. 6. The method according to claim 1, wherein receiving the echo signal sequence of the target object comprises: the reflected carrier signal sequence is received by an array element of a phased array of radar after being echoed by the target object and Processed through a matched filter and stored in memory. 7. The method according to claim 1, wherein synthesizing the echo signal sequence into a high-gain antenna pattern through beamforming comprises: Obtaining the weight coefficient of the low-gain antenna pattern of the carrier signal according to the MVDR beamforming criterion; The high-gain antenna pattern is obtained according to the linear combination of the low-gain antenna pattern. 8. The method of claim 7, wherein, The pattern of the high-gain antenna is: Among them, N represents the number of low-gain antenna patterns, w 0 is obtained by w _{0, n} is the weight of the nth low-gain antenna pattern _{, and N-1} is the weight of the N-1th low-gain antenna pattern. 9. The method of claim 7, wherein, The weight coefficients are: in, 10. A radio frequency stealth device based on a frequency control array, comprising: The transmitting device is used to transmit a carrier signal sequence to the target object, each carrier signal in the carrier signal sequence has a low gain, and each adjacent carrier signal has a specific frequency difference; a receiving device, configured to receive the echo signal sequence of the target object; and A synthesizing device is used for synthesizing the echo signal sequence into a high-gain antenna pattern through beamforming.