Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 191

The incident linearly polarized wave on a slab at 45° has two in‐phase E‐field components. After traveling a distance d, the field components develop a phase difference Δφ. So, for the case E_oy = E_oz = E₀ and a phase difference Δφ = 90° at the output of the slab of thickness x = d, the uniaxial anisotropic dielectric slab converts linearly polarized incident waves into the circularly polarized waves. It is shown below:

(4.7.8)

The electric components of the extraordinary and ordinary waves and also the total E‐field at the output of the slab are

(4.7.9)

The wave at the output of the slab is a left‐hand circularly polarized wave. Such a slab converting the incoming linearly polarized wave to the circularly polarized waves is called the quarter‐waveplate. A waveplate with , i.e. the half‐waveplate rotates the 45° linearly polarized waves by 90° and output electric field component is . The phase of the outgoing waves could be controlled by changing the thickness of a slab. The waveplate acts as a phase shifter. In the case of uniaxial anisotropic plasma medium, the permittivity components are ε_r‖ = ε_r and ε_r⊥ = 1.

The above characteristics of a slab are also realized by thin metasurfaces discussed in subsections (22.5) and (22.6) of chapter 22.