Methods for improving the noise immunity of radio circuits

Two types of small electromagnetic screens for suppression of radio noise between transmit-receiver stations in the decimeter and centimeter wavelength bands are described. The suppression of the field attained with solid screens is limited by the penetration of the field diffracted at the screen boundaries into the geometric shadow region. In the ring-type screening device a circular opening is placed in the screen, with dimensions, shape, and position relative to the edge of the screen such that the resulting field is equal in magnitude and opposite in phase to the edge-diffracted field. In the second, sector-type device, the edge shape is chosen such that the field in a certain direction from individual sections of the edge are mutually compensating. The relationships for determining screen size are derived and compared, and data on the operation of the ring-type screen are presented.