The present invention relates to an apparatus and method for observing a radio hologram by a two-input interference observation method.
The inventor of this application has proposed an apparatus and method for observing a radio hologram in Japanese Patent Application Laid-Open Gazette No. 11-65405 entitled "Circumference Scanning Type Hologram Observation Apparatus and Method Therefor" (laid open Mar. 5, 1999, corresponding German Patent Application Laid-Open DE19838052A-1). As depicted in FIG. 1, a fixed antenna Ar and a rotary scanning antenna Am which is driven by a motor M are used, and the received signal from the antenna Am is received by a receiver Rm via a rotary joint J.sub.R, whereas the received signal from the fixed antenna Ar is received by a receiver Rr. The receivers Rm and Ar select and amplify signals of a preset frequency f, and output IF signals Sr(f) and Sm(.phi., f) (where .phi. is azimuth). These output signals Sr(f) and Sm(.phi., f) are applied to interference means 11, wherein they are caused to interfere with each other to obtain .intg.Sr*(f).multidot.Sm(.phi., f) (where * indicates a complex conjugate), which is detected by a complex detector 12 to obtain measured data E(.phi.). This data is stored in a buffer memory 21 for the rotational angle (horizontal azimuth) of the rotary scanning antenna Am. For the stored result a calculation/display part 22 performs a computation to reconstruct a hologram and displays the result of computation.
By carrying out the hologram measurement as described above, it is possible to obtain a viewing angle over the entire range of 360 degrees with no blind spots.
Because of mechanical driving of the antenna Am for rotary scanning, the above apparatus is incapable of making fast hologram observations. Another disadvantage is susceptibility to unstable reflected and/or diffracted waves.
It is therefore an object of the present invention to provide a radio hologram observation apparatus and method that permit fast hologram observation.
Another object of the present invention is to provide a radio hologram observation apparatus and method that permit stable measurements unaffected by fading.
Still another object of the present invention is to provide a dipole antenna which is simple-structured and suitable for mass production and a manufacturing method which permits easy fabrication of dipole antennas of uniform characteristics.