Radio-wave transparent surface containing lines loaded with impedance at regular intervals

The vector effective length of a half wavelength-dipole becomes almost zero when a reactance of about 500 ohm is loaded to its center. Since the current integral is almost zero when the vector effective length is zero, the electric influence on other antennas and to the radiation field is smaller than an open-circuited dipole. On the other hand, although other antennas affect the amplitude of the current distribution, the shape of the distribution does not change. Therefore, the vector effective length should be kept to zero. Accordingly, not only the influence on other antennas but also the influence by other antennas can be neglected. Dipoles are, therefore, thought to be almost electrically invisible. Lines composed with electrically invisible dipoles joined in series with a connector of open stubs are also thought to be electrically invisible. A surface containing such lines arranged in parallel is thought to be electrically transparent for radio waves at the same frequency at which the dipoles become electrically invisible. In this paper, we examine analytically the transparency of such surfaces.