Device for measuring, at a plurality of points of a surface, the

Details Device for measuring, at a plurality of points of a surface, the Device for measuring, at a plurality of points of a surface, the

1993-01-11

1995-07-04

Wieder, Kenneth A.

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

With waveguide or long line

G01R 104

Patent

active

054303699

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The object of the present invention is a device for the measurement, at a plurality of points, of the microwave field radiated by a source, comprising: antennas, delivering a collected microwave signal, diodes, on the other hand, to each of the diodes, and least one of said diodes is polarized by said low-frequency signal and in order, in response to said low-frequency signal and to said collected microwave signal, to generate a signal representative of the microwave field at the point where said antenna charged by said polarized diode is located.
Such a device makes it possible, for instance, when the source is an antenna to be characterized, to draw up, by the method known to the person skilled in the art as the "modulated diffusion method", a map of the field radiated by the antenna. It may also be used when the source, instead of being an antenna which is to be characterized is an object diffracting a microwave field produced by an auxiliary antenna the radiation pattern of which is known. One can thus, in non-destructive manner, check industrial objects or products or else study the diffraction by a body of complicated shape or composition.
From French Applications 2 614 416 and 2 632 417 devices of the above-defined type are known in which the measurement points are aligned.
These devices are therefore suitable for the carrying out, without mechanical displacement, of one-dimensional measurements of the microwave field, that is to say, along the line or curve on which the antennas are aligned, by the electronic scanning of them.
However, these devices are not suitable for the carrying out, without mechanical displacement, of two-dimensional measurements of the field so as to know the field on a surface.
Furthermore, these one-dimensional devices cannot be simply transposed to two-dimensional devices, due to the presence of the connections which connect each of the diodes to the multiplexer and which it is necessary to make invisible vis a vis the microwave field, in order not to disturb it. Now, while it is relatively simple to make these connections invisible when the antennas are aligned, as shown by the solutions described in the aforementioned applications 2 614 419 and 2 632 417, it is much more difficult to do so in the event that the antennas are distributed over a surface, without limiting the pass band and possibly the sensitivity of the device.
Furthermore, when it is desired to measure, at each point, the components of the field along two perpendicular directions of polarization, it is necessary to have at each of the points two doublet antennas which are perpendicular to each other, for instance. This considerably complicates the preceding problem related to the connections for the feeding of the low-frequency signal towards each of the antennas.
Furthermore, in the device described in Application 2 614 419, the network of antennas is arranged in the proximity of a microwave collecting antenna, comprising for instance a waveguide having a series of slits. From this there results a relatively complicated construction and a risk of interaction between the object being tested and the detection unit formed by the antenna network and the collector waveguide.
These problems do not arise in the device described in Application 2 632 417 due to the fact that the linear network is arranged at the focal point of a reflector, itself arranged at a distance from the path of radiation coming from the source. Due to the focussing employed, such a solution, however, cannot be transferred to a two-dimensional network of antennas.
Furthermore, from French Patent 2 509 064 a device is known which permits the formation of a two-dimensional image of a microwave field, known accordingly as a "microwave camera." This camera employs a two-dimensional network of doublet antennas, for which the problem related to the feed connections of the low-frequency modulation signal is controlled in particular by the use, immediately behind the network of antennas, of a plurality of microwave coll

REFERENCES:
patent: 5006788 (1991-04-01), Goulette et al.
patent: 5177437 (1993-01-01), Henley

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