Ideal magnetic wall

 

A microstrip periodic structure behaves like a magnetic screen near resonance. Defined as a ratio of strength of a reflected to strength of an incident electric field, a reflection coefficient value equals +1 at a resonance. Far from resonance the reflection coefficient is close to –1 and a microstrip structure behaves like a dielectric-coated ideal metal screen. It is possible to design a microstrip periodic structure formed of curved narrow particles which when stretched are much longer than the structure periods. As a result resonance occurs on the wavelength that is much longer than the array periods.

 

The frequency dependence of reflection coefficients of a microstrip array formed by C-shaped metal particles near the lowest resonance frequency is shown in the Figure below as an example. The parameters of the strip are a=4 mm, f =15 degrees, 2w=0.5 mm. Array periods are identical and are 10 mm long, substrate permittivity is 3 and substrate thickness equals to 1.5 mm.

 

The surface admittance

 

 

where  Ohm tends to zero at the resonant frequency. Thus the surface of array is a high impedance surface. A linear polarized along y-direction normal incident wave is reflected by microstrip array of C-shaped particles at resonant frequency in the same way as a surface of ideal magnetic.

 


 

 


References

Prosvirnin S.L., Analysis of electromagnetic wave scattering by plane periodical array of chiral strip elements, Proceedings of 7-th Intern. Conf. on Complex Media “Bianisotropics-98”, Technische Universitat Braunschweig, Germany, 3-6 June 1998, p. 185-188.

Prosvirnin S.L., Transformation of polarization when waves are reflected by a microstrip array made of complex-shaped elements, Journal of Communications Technology and Electronics, 1999, vol. 44, no. 6, p. 635-639.

Russian version:

Просвирнин С.Л., Преобразование поляризации при отражении волн микрополосковой решеткой из элементов сложной формы, Радиотехника и электроника, 1999, т.44, 6, 681-686.

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