| With the significant upgrade on informationization and intelligence of modern weapons and equipment,electromagnetic spectrum has become a resource-based element that runs through the whole field of combat and shows cross-domain influence.In the struggle for strategic advantage in the modern battlefield,the concept of electromagnetic spectrum warfare has been proposed in order to break the increasingly powerful ”anti-access/area denial” capability of the target adversary.The electromagnetic spectrum warfare is the electromagnetic wave struggle for the two sides of the warfare which is the struggle between electronic reconnaissance and anti-reconnaissance,electronic interference and anti-interference,destruction and anti-destruction around the weapons and equipment radiating electromagnetic waves,such as communication,radar,navigation,and guided weapons.The struggle is more and more fierce for electromagnetic space in modern war.Whether the electromagnetic right can be obtained will have a great influence on the process and even the outcome of war.With the emergence of electromagnetic spectrum warfare,conventional combat systems are seriously threatened and challenged,which requires more and more high electromagnetic defense capability and electromagnetic wave control capability of combat systems.The future battlefield electromagnetic environment is complex and changeable,and the weapons and equipment may be interfered and destroyed in the face of electromagnetic suppression and radar detection.This paper focuses on the urgent need to improve the survivability of weapons and equipment.The frequency selective surface(FSS)can flexibly and effectively regulate the characteristics of electromagnetic wave phase,polarization mode,propagation mode and so on.Starting from two aspects of electromagnetic anti-interference and radar stealth,the design and application of FSS for electromagnetic defense are carried out.In terms of electromagnetic anti-interference,the current design methods have some problems,such as easy interaction between elements,complex graphic design,difficult processing,sensitive to the angle of incident wave,poor tight spacing characteristics,non-independent frequency band and poor electromagnetic wave regulation ability which affect the application effect of FSS.In terms of radar stealth,FSR is proposed by adding lumped components to realize.However,the current design methods have some shortcomings,such as uneven performance,complex design,large size,and low frequency realization,which become the main factors limiting their application.In view of the above problems and in order to achieve electromagnetic control of weapons and equipment and improve electromagnetic defense capability in complex battlefield environment,the main research work of this paper can be summarized as follows:(1)Aiming at the problem of insufficient miniaturization for existing FSS structures in face of electromagnetic interference,the method of /4center rotation and branch penetration is proposed.Two new dual-passband miniaturized FSS structures applied in different scenarios are designed,which can enhance the effective transmission of in-band signals,reduce outof-band interference and improve the electromagnetic anti-interference performance.For the first structure,a new combination element is formed by improving the traditional square ring type slot and Jerusalem type slot.This structure can realize the dual band transmission at 28.1GHz and 39.5GHz,and has a large enough bandwidth to cover 27.5GHz～28.35 GHz and 38.6GHz～40GHz bands of 5G,which will help improve the anti-interference capability of future military 5G high-frequency equipment.Compared with the existing 5G-oriented FSS structure,this structure extends single-frequency filtering to dual-frequency filtering,simplifies layer design to reduce the structural complexity.In terms of stability,the incident angle can be increased from 40° to 45°.In terms of miniaturization,thickness is reduced by83.97% and unit size is reduced by 1.1%.For the second structure,a new step-type slot element is designed based on rectangular slot.The two transmission frequencies of the structure are 6.7GHz and 18.1GHz respectively,which can be applied to the satellite communication equipment in the C-band and K-band.Compared with the existing FSS structures for satellite communication,the proposed structure also extends from single frequency filtering to dual frequency filtering,and simplifies layer design.In addition,the thickness is reduced by96%,and unit size is reduced by 54.34%.(2)Aiming at the problem that the existing FSS structure has poor tightly spaced characteristics when facing multi-frequency electromagnetic interference,especially compact frequency electromagnetic interference,the method of interdigital interconnection and isometric dense arrangement is proposed.Two new FSS structures with tightly spaced dualfrequency/multi-frequency characteristics are designed,which can realize the application of dual-frequency/multi-frequency shielding devices in complex electromagnetic environment.For the first structure,a new arched ring patch element is designed which has the characteristics of double stopband and tightly spaced.Compared with the existing compact structure,it can simultaneously realize low resonant ratio,independent control of frequency band and miniaturization design.For the second structure,a new combination element is formed by improving the swastika slot,well slot,cross slot and back slot.This structure has three stopband characteristics,and the resonant points are tightly spaced that located in S,C and X bands respectively.Compared with the existing structure,this structure shows that the unit size is reduced by 39.1% and the thickness is reduced by 72.5%.(3)Aiming at the problem that the existing FSR structure can not take into account the inband transmission performance and out-of-band stealth performance when the device is powered on for a long time,the method of device center cascade loading is proposed.A novel FSR structure with balanced absorption and transmission performance is designed to achieve stealth applications in military equipment.A new type of embedded double bow resonator element is designed and its filtering characteristics are A-T-A.Compared with the existing structure,the absorption performance of both sides is balanced that the bandwidth is more than 50%,the unit size is reduced by 8% at least,and the angular stability is increased by50%.In addition,the gradient concept is introduced into FSR for the first time to define the steep drop characteristic of FSR structure,which makes the performance analysis of A-T-A FSR structure more comprehensive.(4)Aiming at the problem that existing FSR structure needs to instantly switch stealth mode in the face of frequent switching on and off of low-frequency equipment during radar detection,a new method of expanding branches and co-loading with active/passive devices is proposed.Two new active controllable A-T-A FSR structures for low frequency applications are designed,which can switch operating modes based on mission requirements to maximize stealth capability without compromising mission completion.The first structure is optimized and improved on the basis of the structure in Chapter 5,which is formed by loading PIN diode device and crimped branch of cross ring slot.The structure can control the low frequency and has large absorption bandwidth.In the communication mode,it is the normal A-T-A FSR.In the stealth mode,the structure is a full absorber structure which is a traditional CAA.In order to improve the transmittance in communication mode,a low frequency controlled FSR with high transmittance is proposed.In this structure,a new type of embedded diamond resonator element is designed.Although the performance of the proposed structure is poor in absorption bandwidth,the transmission rate can be increased by 25.4% in the communication mode and transmission frequency can be reduced while realizing the function of the first structure. |
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