New dual‐beam leaky‐wave radiations based on spoof surface plasmon polariton (SSPP) waveguide, in which the amplitude, radiation, angle and polarization of each beam can be designed independently, is proposed. The proposed SSPP waveguide is made of a corrugated metallic strip with bilateral 45°‐tilted grooves, whose surface impedance is flexibly designed by changing the depth of grooves. To realize dual‐beam leaky‐wave radiations, the surface impedance of SSPP waveguide is modulated periodically based on the superposition theory of aperture fields. By simply adjusting the modulation factors, modulation periods, and initial phase differences of the modulated surface impedance, the amplitude, radiation angle, and polarization of each beam can be further controlled independently as well. The results have been validated by both numerical simulations and experimental measurements, which show good agreement with the theoretical predictions.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adpr.202100313

Dual‐Beam Leaky‐Wave Radiations with Independent Controls of Amplitude, Angle, and Polarization Based on SSPP Waveguide

In this article, a periodic leaky‐wave antenna (LWA) with wide‐angle beam scanning and stable gain is proposed based on the meandering microstrip line. Due to the meandering property of the microstrip line, the longitudinal dimension of the antenna is reduced. Firstly, the radiation characteristic of the meandering microstrip line is analyzed in detail. Each corner of the meandering microstrip line is modeled by a shunt capacitance and shunt radiation conductance to acquire the equivalent circuit. Then, the frequency balanced condition is investigated based on the established equivalent circuit to realize continuous beam scanning through broadside. Subsequently, the method of open‐stop band (OSB) suppression is studied by introducing asymmetric perturbation on the LWA unit cell, which actually can be applied to eliminate the OSB effect in arbitrary symmetric LWAs. Finally, an antenna prototype is simulated and measured. The measured results agree well with the simulated results, validating the proposed method of OSB suppression. The measured results show that the designed antenna exhibits the beam scanning capacity of −47° to +76° with the frequency varying from 5.0 to 7.8 GHz and gain variation of 2.9 dB.

A periodic meandering microstrip line leaky‐wave antenna with consistent gain and wide‐angle beam scanning

In this work, a polarization independent and wideband electromagnetic (EM) waves absorbing frequency selective surface (FSS) structure is presented. The unit cell of the proposed FSS consists of an assembly of cross arrow resonators with four SMD resistors mounted on it, to enhance the absorbance bandwidth. This unit cell also possesses a four‐fold symmetry which makes it polarization insensitive. The designed unit cell is compact with the length and width dimensions as 0.19λL × 0.19λL, and thickness of 0.13λL, where λL is the guided wavelength corresponding to the lowest operating frequency. The proposed absorber is theoretically and experimentally tested for its absorbance, cross‐polarization level, and radar cross section (RCS) characteristics. The computer‐aided simulation and practical measurements indicate that the proposed absorber offers more than 90% (with a fractional bandwidth of 93%) absorbance for normal incidence at 4.5–12.4 GHz frequency band. The cross‐polarization reflection coefficient analysis indicates that the proposed FSS configuration behaves as an absorber and not a polarization convertor. The input impedance plot, surface current distribution, and E‐field distribution of the unit cell were also analyzed and presented to understand the absorbance mechanism. The RCS of the proposed FSS is compared with the RCS of a reflective (metallic) sheet to analyze its suitability for practical applications (RCS reduction) within the working band. The 3D simulated and 2D calculated RCS results indicate that the proposed FSS is suitable for wideband EM wave absorber applications.

Wideband, polarization independent electromagnetic wave absorber using cross arrow resonator and lumped SMD resistors for C and X band applications

This paper presents a dual-band polarization-insensitive, highly angular stable and flexible EM wave absorber with low cross-polarization reflection. The proposed unit cell has two resonators C and D which offers absorptions at two distinct frequencies at 8.7 and 11.5 GHz frequency in the X band. This FSS unit cell structure has four-fold symmetry make it polarization-insensitive. The absorbance mechanism of the proposed structure is explained with the help of electric and magnetic coupling along with effective impedance plot. The simulation results reveal that for both bands, the proposed absorber is polarization insensitive and angular stable up to 60 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> . Along with this study, reflection due to cross-polarization is also analyzed and included in the absorbance equation, confirming that the proposed design is an absorber, not a polarization converter. Finally, the absorber prototype is fabricated and tested under different conditions, and the measurement results perfectly match the simulation result, which verified that it is working. 

Dual-Band, Polarization Insensitive, and Flexible EM Wave Absorber with High Angular Stability and Low Cross Reflection Level

A multi-functional metasurface structure is presented in this paper. This metasurface consists of two resonating structures printed on two FR-4 substrates, while the bottom side of the structure is completely laminated with copper. The proposed design offered absorption at 6.1 GHz frequency with 200 MHz bandwidth and polarization conversion in the X band from 7.8 to 11.9 GHz frequency band. The presented unit cell is compact with a length and width of $0.31\lambda\times 0.31\lambda$ while thickness is $0.081\lambda$, where $\lambda$ is the free-space wavelength at 6.1 GHz. The simulation results show that the proposed structure absorbs EM wave at 6.1 GHz in the C band with angular stability of up to 70° for both TE and TM polarization. Whereas the four-fold symmetry inside the resonator provides polarization insensitivity in nature. Along with this absorption phenomenon, this proposed structure also provides a polarization conversion phenomenon in the X band from 7.8 −11.9 GHz with angular stability of up to 50°. The absorbance mechanism in the proposed structure is further explicated with the help of surface current distribution, E-field distribution, and impedance plot, whereas the polarization conversion mechanism has been explained with the help of reflection due to cross-polarization.

Multifunction Metasurface Structure for Absorption and Polarization Conversion Application

This work presents dual band, polarization insensitive and angular stable radar absorber structure Here, proposed absorber unit cell has two resonator structures M and N Each resonator provides absorption at distinct frequencies in X and Ku band Simulation results in different cases show that the structure is polarization insensitive and angular stable up to 600 Calculated effective impedance plot and surface current distribution at the top and bottom surface supports the absorption mechanism at the resonance frequencies To verify the simulations, a prototype of absorber is fabricated on FR-4 substrate and tested in an anechoic environment

Dual Band Polarization Insensitive Frequency Selective Surface Absorber

In this work, a flexible radar absorber structure is presented which offers high absorbance within X band. The proposed structure is designed by integrating two different resonators which provides high angular-stability properties. The theoretical and experimental results indicate that the proposed absorber is polarization insensitive and angular stable up to 60° in both the TE and TM polarization cases. Apart from conventional absorptivity analysis, the cross-polarization reflection of the proposed absorber is also calculated. The simulated results indicate that the proposed FSS configuration behaves as proper absorber and not a polarization convertor. The Radar Cross Section (RCS) of the proposed absorber is also calculated and compared with the RCS of a reflective sheet to analyze its suitability for practical applications at 10.95 GHz frequency in X band. The fabricated absorber is also tested for different angle of bend to test the effects of its flexibility on absorption. The simulation and measurement results indicate that the proposed absorber is highly suitable for absorption application within X-band.

Awanish Kumar

Papers

Dual Band Polarization Insensitive Frequency Selective Surface Absorber

Flexible EM Wave Absorber with High Angular Stability and Low Cross Polarization Reflection Level

Asymmetric meander line slot-based X-band leaky wave antenna