CN106295038A - A kind of active frequencies selects surface method for designing - Google Patents

Abstract

One active frequencies of the present invention selects surface method for designing to belong to microwave technology and aeroplane stealthy technology field, relates to a kind of active frequencies and selects the method for designing on surface, is applied to meet the aircraft radome design of electromagnetism stealth performance.The method uses LC antiresonant circuit to describe bandpass-type wave filter, determines the inductance value in LC antiresonant circuit and capacitance.Selected frequency-selective surfaces unit, sets up the equivalent-circuit model of frequency-selective surfaces, obtains the inductance value in equivalent-circuit model and capacitance.Determining the loading position of chip inductor and patch capacitor, frequency of amendment selects surface equivalent-circuit model, obtains the parameter value of patch capacitor and the chip inductor loaded, and completes active frequencies and selects surface structure design.The active frequencies that the method efficiently solves under filtering performance constraint selects surface design problem, can be used for instructing the aircraft radome design possessing electromagnetism stealth performance, improves stealthy effectiveness and the survival ability in wartime of aircraft.

Description

A kind of active frequencies selects surface method for designing

Technical field

The invention belongs to microwave technology and aeroplane stealthy technology field, relate to a kind of active frequencies and select the design on surface Method, is applied to meet the aircraft radome design of electromagnetism stealth performance.

Background technology

Antenna house is the protection aircraft radars system electromagnetism window from extraneous adverse circumstances impact.The most do not affect system Conduction magnetic wave passes through, and enemy detects electromagnetic wave simultaneously and keeps the antenna house of high resistant characteristic, and the electromagnetism that could meet aircraft is hidden Body demand.At present, frequency-selective surfaces (FSS) technology is the main path solving the design of antenna house electromagnetism stealth.Fly stealthy In the radome design of row device, it is ensured that in 0～60 ° of sweep limits, resonant frequency f of filtering characteristic₀Keep stable.Load The active frequencies of the lamped element such as patch capacitor, chip inductor selects surface (AFSS) to be to improve filtering characteristic resonant frequency to stablize The possible strategy of property.Now, the Major Difficulties of AFSS technology is: according to the resonant frequency in filtering characteristic and bandwidth, determine Active frequencies selects the structural parameters on surface, including: the structural parameters of frequency-selective surfaces and the patch capacitor value of loading, paster Inductance value, it is achieved the active frequencies towards filtering characteristic selects surface structure design.

In recent years, Chinese scholars is around frequency-selective surfaces modelling by mechanism, Performance analysis of filtering algorithms, Optimal Structure Designing etc. Aspect has carried out theoretical and experimental study, achieves some achievements in research.Surface design aspect, high sturdy pines is selected at active frequencies Et al. the patent method for designing of surface " active frequencies select ", in publication number CN105244570A, invented a kind of automatically controlled PIN The active frequencies that diode loads selects the method for designing on surface, efficiently solves active frequencies and selects feed loading side, surface Formula and the most extendible technical barrier of technique, can be used for the design of active radar and passive radar combined guidance antenna house.But, for filtering Active frequencies under Performance Constraints selects surface structure design problem, still lacks effective method.

Summary of the invention

Present invention aim to address in prior art and cannot obtain according to the resonant frequency in filtering characteristic and bandwidth Taking active frequencies and select surface texture parameters problem, the active frequencies invented under the constraint of a kind of filtering performance selects surface design side Method.The method utilizes the resonant frequency in target filtering characteristic and bandwidth, determines the inductance value in LC antiresonant circuit and electricity Capacitance；Selected frequency-selective surfaces unit, sets up the equivalent-circuit model of frequency-selective surfaces, obtains in equivalent-circuit model Inductance value and capacitance；The structural parameters of random given frequency-selective surfaces, extract this structural parameters lower frequency and select surface Equivalent inductance value and equivalent capacitance value；Determine the loading position of chip inductor and patch capacitor, complete active frequencies and select surface Structure designs.The method is effective, improves stealthy effectiveness and the survival ability in wartime of aircraft.

The technical solution used in the present invention is that a kind of active frequencies selects surface method for designing, it is characterized in that, the method is adopted Describe bandpass-type wave filter by LC antiresonant circuit, utilize the resonant frequency in target filtering characteristic and bandwidth, determine that LC is also Inductance value in connection resonance circuit and capacitance；Selected frequency-selective surfaces unit, sets up the equivalent circuit of frequency-selective surfaces Model, is mapped to the inductance value in LC antiresonant circuit and capacitance in the equivalent-circuit model of frequency-selective surfaces, obtains Take the inductance value in equivalent-circuit model and capacitance；The structural parameters of random given frequency-selective surfaces, extract this structure ginseng Number lower frequency selects equivalent inductance value and the equivalent capacitance value on surface；Determine the loading position of chip inductor and patch capacitor, repair Positive frequency selects surface equivalent-circuit model, obtains the parameter value of patch capacitor and the chip inductor loaded, completes active frequencies Select surface structure design；It is as follows that method is embodied as step:

Step one, according to resonant frequency f in target filtering characteristic₀, bandwidth BW, determine the electricity in LC antiresonant circuit Inductance value L and capacitance C, concrete formula is as follows:

$C=\frac{1}{BW\·\mathrm{\π}\·Z_0}---\left(1\right)$

$L=\frac{1}{C\·{\left(2{\mathrm{\πf}}_0\right)}^2}---\left(2\right)$

Wherein, Z₀=377 Ω are free space wave resistance value；

Step 2, determines frequency-selective surfaces cellular construction, sets up the equivalent-circuit model of frequency-selective surfaces；Foundation The principle " possessing bandpass-type filtering characteristic ", determines frequency-selective surfaces cellular construction, sets up the equivalent electric of frequency-selective surfaces Road model.Inductance value L in equivalent-circuit model_FSSWith capacitance C_FSSBy the inductance value in LC antiresonant circuit and capacitance Determining, concrete formula is as follows:

Y_FSS(ω₀)=Y_LC(ω₀) (3)

${\stackrel{\·}{Y}}_{FSS}\left({\mathrm{\ω}}_0\right)={\stackrel{\·}{Y}}_{LC}\left({\mathrm{\ω}}_0\right)---\left(4\right)$

Wherein,For utilizing the equivalent-circuit model of frequency-selective surfaces to try to achieve, in resonant angle Frequencies omega₀Under the first derivative values of admittance value and admittance；For utilizing LC antiresonant circuit to try to achieve , in angular frequency₀Under the first derivative values of admittance value and admittance；

Step 3, the structural parameters of random given frequency-selective surfaces unit, utilize the frequency under current structure parameter to select Select coefficient of surface scattering, extract equivalent inductance value and equivalent capacitance value；Given structural parameters must satisfied retrain as follows:

p·(1+sinθ)≤λ₀ (5)

Wherein, p is that frequency-selective surfaces unit arranges the cycle, and θ is maximum incident angle degree, λ₀For resonant frequency corresponding from By space wavelength；

Employing numerical value emulation method obtains the frequency-selective surfaces under each angular frequency under current structure parameter Scattering coefficientBy scattering coefficient S₁₁(ω) the input resistance of derivation frequency-selective surfaces Anti-Z_FSS(ω):

$Z_{FSS}\left(\mathrm{\ω}\right)=\frac{Z_0(1+S_{11}(\mathrm{\ω}\left)\right)}{-2S_{11}\left(\mathrm{\ω}\right)}---\left(6\right)$

By input impedance Z_FSS(ω), derive under each angular frequency, equivalent inductance value L of frequency-selective surfaces (ω), equivalent capacitance value C (ω), concrete formula is as follows:

$L\left(\mathrm{\ω}\right)=\frac{\mathrm{Im}\left(Z_{FSS}\right(\mathrm{\ω}\left)\right)\·({\mathrm{\ω}}_0^2-{\mathrm{\ω}}^2)}{{\mathrm{\ω}}^2{\mathrm{\ω}}_0^2}---\left(7\right)$

$C\left(\mathrm{\ω}\right)=\frac{1}{{\mathrm{\ω}}_0^2\·L\left(\mathrm{\ω}\right)}---\left(8\right)$

Wherein, Im represents imaginary part, ω₀Represent resonance angular frequency；

Utilize equivalent inductance value L (ω) under each angular frequency, equivalent capacitance value C (ω), calculate equivalent circuit mould The input impedance that type is corresponding；Definition equivalent-circuit model input impedance and the input impedance Z determined by scattering coefficient_FSS(ω) between Impedance residual error r；Taking one group of minimum equivalent inductance of impedance residual error and equivalent capacity, the frequency being under current structure parameter is selected Select equivalent inductance value L on surface₁With equivalent capacitance value C₁；

$r=\frac{1}{N}\underset{i=1}{\overset{N}{\Σ}}\left(\frac{{\mathrm{\ω}}_i\·L_i\left(\mathrm{\ω}\right)}{1-{\mathrm{\ω}}_i^2\·L_i\left(\mathrm{\ω}\right)\·C_i\left(\mathrm{\ω}\right)}-\mathrm{Im}\left(Z_{FSS}\left({\mathrm{\ω}}_i\right)\right)\right)---\left(9\right)$

Wherein, ω_iFor the i-th angular frequency that frequency-selective surfaces is corresponding, N is the work frequency of frequency-selective surfaces angular frequency Count；

Step 4, determines the loading position of chip inductor and patch capacitor, and frequency of amendment selects the equivalent circuit mould on surface Type, determines the chip inductor of loading and the parameter value of patch capacitor；Chip inductor uses lateral symmetry loading side with patch capacitor Formula, arranges in periodic regularity；Load inductance value L in the equivalent-circuit model after chip inductor and patch capacitor_totalWith electricity Capacitance C_totalMeet:

L_total=L₁+L_add (10)

C_total=C₁+C_add (11)

Wherein, L₁、C₁For not loading equivalent inductance value and the equivalent electric of the frequency-selective surfaces of chip inductor and patch capacitor Capacitance；L_add、C_addFor the chip inductor loaded and the parameter value of patch capacitor；

For meeting target filtering characteristic, load the frequency-selective surfaces equivalent-circuit model after chip inductor and patch capacitor In inductance value L_totalWith capacitance C_totalShould be equal to the electricity in the frequency-selective surfaces equivalent-circuit model determined in step 2 Inductance value L_FSSWith capacitance C_FSS, and then determine the chip inductor of loading and the parameter value L of patch capacitor_add、C_addFor:

L_add=L_total-L₁=L_FSS-L₁ (12)

C_add=C_total-C₁=C_FSS-C₁ (13)

Complete active frequencies by above-mentioned steps and select surface structure design.

The invention has the beneficial effects as follows that the active frequencies of the present invention selects surface method for designing, can be special according to the filtering of target Resonant frequency in property and bandwidth, determine that active frequencies selects the structural parameters on surface, efficiently solves filtering performance constraint Under active frequencies select surface design problem, can be used for instructing the aircraft radome design possessing electromagnetism stealth performance, carry The stealthy effectiveness of high aircraft and survival ability in wartime.

Accompanying drawing explanation

Fig. 1 is to present invention determine that the flow chart that active frequencies selects surface texture parameters.

The structural representation of Fig. 2 side of being annular aperture unit, wherein: the p-frequency-selective surfaces unit arrangement cycle, g-gold Belong to strip width, d-metal patch width, w-gap width.

Fig. 3 a) it is the structural representation of square annular aperture unit that loads of lamped element, wherein: 1-chip inductor, 2-pastes Chip capacitor；Fig. 3 b) it is the equivalent-circuit model of square annular aperture unit that loads of lamped element, wherein: L_add-chip inductor is joined Numerical value, C_addThe parameter value of-patch capacitor, L₁The equivalent inductance value of-extraction, C₁The equivalent capacitance value of-extraction.

Fig. 4 is the frequency response characteristic on the active frequencies selection surface of embodiment of the present invention, wherein: 1-designs Active frequencies select the filtering curve on surface, 2-target filtering curve, axis of abscissas represents simulation frequency, single Position: GHz, axis of ordinates represents power transmission coefficient, unit: dB.

Detailed description of the invention

With technical scheme, the present invention is further elaborated with below in conjunction with the accompanying drawings.

The present invention utilizes LC antiresonant circuit to describe band filter, utilize resonant frequency in target filtering characteristic and Bandwidth, determines inductance value L in LC antiresonant circuit and capacitance C, and maps that to frequency-selective surfaces equivalent circuit In model, and then obtain inductance value L in the frequency-selective surfaces equivalent-circuit model meeting target filtering characteristic_FSSWith electric capacity Value C_FSS.Meanwhile, random given frequency-selective surfaces structural parameters, utilize parameter extracting method, extract under current structure parameter, Equivalent inductance value L of frequency-selective surfaces₁With equivalent capacitance value C₁.On this basis, the chip inductor parameter value of loading is determined L_addWith patch capacitor parameter value C_add, it is achieved the active frequencies under filtering characteristic constraint selects surface design.

Fig. 1 is to present invention determine that the flow chart that active frequencies selects surface texture parameters.The specific embodiment party of the present embodiment Formula is as follows:

Step one, according to resonant frequency f in target filtering characteristic₀With-three dB bandwidth BW, determine LC antiresonant circuit In inductance value L and capacitance C.

In the present embodiment, take resonant frequency f₀=2.5GHz ,-three dB bandwidth BW=1GHz, substitute in formula (1), (2) and ask Inductance value in the LC antiresonant circuit obtained and capacitance are respectively L=4.8nH, C=0.844pF.

Step 2, determines frequency-selective surfaces cellular construction, sets up the equivalent-circuit model of frequency-selective surfaces, by LC also Inductance value L in connection resonance circuit and capacitance C, determine inductance value L in equivalent-circuit model_FSSWith capacitance C_FSS。

According to the principle of " possessing bandpass-type filtering characteristic ", optional square annular aperture unit, annular aperture unit etc. Frequency-selective surfaces cellular construction.In the present embodiment, selecting party annular aperture type frequency-selective surfaces unit, as in figure 2 it is shown, its Equivalent-circuit model is LC antiresonant circuit.Use formula (3), (4), solving equation group, it is thus achieved that frequency-selective surfaces equivalence Inductance value L in circuit model_FSSWith capacitance C_FSSIt is respectively as follows: L_FSS=L=4.8nH, C_FSS=C=0.844pF.

Step 3, the structural parameters of random given frequency-selective surfaces unit, utilize the frequency under current structure parameter to select Select coefficient of surface scattering, extract equivalent inductance value and equivalent capacitance value.

In the present embodiment, the frequency-selective surfaces unit chosen is side's annular aperture unit, with reference to Fig. 2, meets constraint (5), random given cellular construction parameter is p=5mm, s=0.2mm, g=0.2mm, d=4.2mm.Utilize full wave analysis side Method obtains the scattering coefficient S of the frequency-selective surfaces under each angular frequency under current structure parameter₁₁(ω), formula is brought into (6) the input impedance Z of frequency-selective surfaces under each angular frequency, is asked for_FSS(ω).By formula (7)～(9), ask for Current structure parameter under equivalent inductance value L of frequency-selective surfaces₁With equivalent capacitance value C₁It is respectively as follows: L₁=1.34nH, C₁ =0.068pF.

Step 4, determines the loading position of chip inductor and patch capacitor, and frequency of amendment selects the equivalent circuit mould on surface Type, determines the chip inductor of loading and the parameter value of patch capacitor.

With reference to Fig. 3 (a), chip inductor and patch capacitor take lateral symmetry load mode.By L_FSS=4.8nH, C_FSS= 0.844pF, L₁=1.34nH, C₁=0.068pF brings formula (12), (13), the chip inductor of loading and the parameter of patch capacitor into Value is respectively L_add=3.46nH, C_add=0.776pF.

Surface texture is selected to carry out simulation analysis active frequencies determined by the present embodiment:

Fig. 4 is the frequency response characteristic on the active frequencies selection surface of embodiment of the present invention, represents in figure Active frequencies selects surface frequency response curve under the conditions of electromagnetic wave vertical incidence.Wherein, the active frequencies choosing of 1-design Select the filtering curve on surface, 2-target filtering curve.From fig. 4, it can be seen that the active frequencies of design selects surface Filtering characteristic in resonant frequency and-three dB bandwidth is higher with the target filtering characteristic goodness of fit, reaches the design effect being satisfied with. Wherein, the active frequencies of design selects the resonant frequency on surface to be 2.5GHz, identical with target resonance frequency；-three dB bandwidth is 0.99GHz, target-three dB bandwidth is 1GHz, and relative error is 1%.

Claims (1)

1. active frequencies selects a surface method for designing, it is characterized in that, it is logical that the method uses LC antiresonant circuit to describe band Mode filter, utilizes the resonant frequency in target filtering characteristic and bandwidth, determines the inductance value in LC antiresonant circuit and electricity Capacitance；Selected frequency-selective surfaces unit, sets up the equivalent-circuit model of frequency-selective surfaces, by LC antiresonant circuit Inductance value and capacitance are mapped in the equivalent-circuit model of frequency-selective surfaces, obtain inductance value in equivalent-circuit model with Capacitance；The structural parameters of random given frequency-selective surfaces, extract this structural parameters lower frequency and select the equivalent inductance on surface Value and equivalent capacitance value；Determining the loading position of chip inductor and patch capacitor, frequency of amendment selects surface equivalent-circuit model, Obtain the parameter value of patch capacitor and the chip inductor loaded, complete active frequencies and select surface structure design；Method concrete Step is as follows:

Step one, according to resonant frequency f in target filtering characteristic₀, bandwidth BW, determine inductance value L in LC antiresonant circuit With capacitance C, concrete formula is as follows:

$C=\frac{1}{BW\·\mathrm{\π}\·Z_0}---\left(1\right)$

$L=\frac{1}{C\·{\left(2{\mathrm{\πf}}_0\right)}^2}---\left(2\right)$

Wherein, Z₀=377 Ω are free space wave resistance value；

Step 2, determines frequency-selective surfaces cellular construction, sets up the equivalent-circuit model of frequency-selective surfaces, according to " possessing Bandpass-type filtering characteristic " principle, determine frequency-selective surfaces cellular construction, set up the equivalent circuit mould of frequency-selective surfaces Type.Inductance value L in equivalent-circuit model_FSSWith capacitance C_FSSTrue with capacitance by the inductance value in LC antiresonant circuit Fixed, concrete formula is as follows:

Y_FSS(ω₀)=Y_LC(ω₀) (3)

${\stackrel{\·}{Y}}_{FSS}\left({\mathrm{\ω}}_0\right)={\stackrel{\·}{Y}}_{LC}\left({\mathrm{\ω}}_0\right)---\left(4\right)$

Wherein, Y_FSS(ω₀),For utilizing the equivalent-circuit model of frequency-selective surfaces to try to achieve, in resonance angular frequency ω₀Under the first derivative values of admittance value and admittance；Y_LC(ω₀),For utilizing LC antiresonant circuit to try to achieve, Angular frequency₀Under the first derivative values of admittance value and admittance；

Step 3, the structural parameters of random given frequency-selective surfaces unit, utilize the frequency selection table under current structure parameter Area scattering coefficient, extracts equivalent inductance value and equivalent capacitance value；Given structural parameters must satisfied retrain as follows:

p(1+sinθ)≤λ₀ (5)

Wherein, p is that frequency-selective surfaces unit arranges the cycle, and θ is maximum incident angle degree, λ₀For the freely sky that resonant frequency is corresponding Between wavelength；

Numerical value emulation method is used to obtain the scattering of the frequency-selective surfaces under each angular frequency under current structure parameter CoefficientBy scattering coefficient S₁₁(ω) the input impedance Z of derivation frequency-selective surfaces_FSS (ω):

$Z_{FSS}\left(\mathrm{\ω}\right)=\frac{Z_0(1+S_{11}(\mathrm{\ω}\left)\right)}{-2S_{11}\left(\mathrm{\ω}\right)}---\left(6\right)$

By input impedance Z_FSS(ω), derive under each angular frequency, equivalent inductance value L (ω) of frequency-selective surfaces, etc. Effect capacitance C (ω), concrete formula is as follows:

$L\left(\mathrm{\ω}\right)=\frac{Im\left(Z_{FSS}\right(\mathrm{\ω}\left)\right)\·({\mathrm{\ω}}_0^2-{\mathrm{\ω}}^2)}{{\mathrm{\ω}}^2{\mathrm{\ω}}_0^2}---\left(7\right)$

$C\left(\mathrm{\ω}\right)=\frac{1}{{\mathrm{\ω}}_0^2\·L\left(\mathrm{\ω}\right)}---\left(8\right)$

Wherein, Im represents imaginary part, ω₀Represent resonance angular frequency；

Utilize equivalent inductance value L (ω) under each angular frequency, equivalent capacitance value C (ω), calculate equivalent-circuit model pair The input impedance answered；Definition equivalent-circuit model input impedance and the input impedance Z determined by scattering coefficient_FSS(ω) resistance between Anti-residual error r；Take one group of minimum equivalent inductance of impedance residual error and equivalent capacity, the frequency selection table being under current structure parameter Equivalent inductance value L in face₁With equivalent capacitance value C₁；

$r=\frac{1}{N}\underset{i=1}{\overset{N}{\Σ}}(\frac{{\mathrm{\ω}}_i\·L_i\left(\mathrm{\ω}\right)}{1-{\mathrm{\ω}}_i^2\·L_i\left(\mathrm{\ω}\right)\·C_i\left(\mathrm{\ω}\right)}-\mathrm{Im}(Z_{FSS}\left({\mathrm{\ω}}_i\right)))---\left(9\right)$

Wherein, ω_iFor the i-th angular frequency that frequency-selective surfaces is corresponding, N is the working frequency points number of frequency-selective surfaces angular frequency；

Step 4, determines the loading position of chip inductor and patch capacitor, and frequency of amendment selects the equivalent-circuit model on surface, really The fixed chip inductor loaded and the parameter value of patch capacitor；Chip inductor uses lateral symmetry load mode with patch capacitor, in Periodic regularity is arranged；Load inductance value L in the equivalent-circuit model after chip inductor and patch capacitor_totalWith capacitance C_totalMeet:

L_total=L₁+L_add (10)

C_total=C₁+C_add (11)

Wherein, L₁、C₁For not loading equivalent inductance value and the equivalent capacity of the frequency-selective surfaces of chip inductor and patch capacitor Value；L_add、C_addFor the chip inductor loaded and the parameter value of patch capacitor；

For meeting target filtering characteristic, load in the frequency-selective surfaces equivalent-circuit model after chip inductor and patch capacitor Inductance value L_totalWith capacitance C_totalShould be equal to the inductance value in the frequency-selective surfaces equivalent-circuit model determined in step 2 L_FSSWith capacitance C_FSS, and then determine the chip inductor of loading and the parameter value L of patch capacitor_add、C_addFor:

L_add=L_total-L₁=L_FSS-L₁ (12)

C_add=C_total-C₁=C_FSS-C₁ (13)

Complete active frequencies by above-mentioned steps and select surface structure design.