Non-contact type wave signal observation apparatus takes measurements of electromagnetic waves received on an observation plane and performs hologram reconstruction calculations to reconstruct characteristics of the corresponding electromagnetic wave information at points in the observed space. A first aspect of the invention provides apparatus for measuring transfer functions (and, if desired, waveforms) at any point on a network containing a transmission line having distributed properties but no internal signal sources. A second aspect of the invention provides apparatus for measuring transfer functions (and, if desired, waveforms) at any point on a network containing a transmission line having distributed properties and having internal signal sources - the processing takes into account fluctuations occurring in the electromagnetic radiation given off by the network. A third aspect of the invention provides apparatus for analysis of spatial electromagnetic waves so as to determine properties such as those related to polarization of the radiation, one or more pairs of mutually orthogonal antennas having figure-of-eight beam patterns are used in the observation plane. A fourth aspect of the invention provides holographic radar apparatus in which the high frequency radiation illuminating the observation space is pulse modulated and the holographic reconstruction calculations are simplified. A fifth aspect of the invention provides a display for displaying complex three-dimensional data such as interference data of electromagnetic waves produced by the apparatus according to the other aspects of the invention. The complex data is converted from orthogonal co-ordinates to polar co-ordinates, the phase information is converted to hue information in a hue converter and the amplitude information is used to modulate the brightness of the displayed signal; corresponding colour signals are displayed on a colour display unit. <IMAGE>
Non-contact type wave signal observation apparatus