Abstract: Apparatus useful for mapping fields in the range of infrasonic to ultraso, comprising a distributed electrostatic transducer, functioning as a strip transmission line, which includes a flat, substantially rectangular, metal plate, one surface of which is rough, the plate having a length generally in the range of 10 to 100 wavelengths of the frequency at which the mapping is to be done. A rectangular strip of dielectric foil is disposed under tension on the rough surface of the metal plate so that the foil touches only the most protruding parts of the surface. A long, narrow, rectangular, metallic strip is disposed on and attached to the dielectric foil, the strip being exposed to, and therefore defining, an acoustic pressure field.A duplexer is electrically connected to the metallic strip and to the flat plate, and is connectable to a source of input signals, and has output terminals at which the output signal may be measured.

Abstract: An apparatus for the generation of a two-dimensional discrete Fourier transform of an input signal developed from data within a data block, or field, having a size of N.sub.1 by N.sub.2 data points, N.sub.1 and N.sub.2 being relatively prime with respect to each other, the transforms being in a form suitable for subsequent electronic processing. The apparatus comprises an input scan apparatus connectable to the N.sub.1 by N.sub.2 two-dimensional data field comprising the input signal, such as a television viewing field. The apparatus receives and scans in proper order, or sequence, the N.sub.1 by N.sub.2 input data so that the subsequently generated one-dimensional Fourier transform of the length N.sub.1 N.sub.2 serial data string is identical to an N.sub.1 by N.sub.2 two-dimensional discrete Fourier transform of the N.sub.1 by N.sub.2 input data samples.