Antenna and associated measurement sensor
An antenna which comprises four elementary IFA antennae, each elementary IFA antenna comprising a ground plane ( 1 ), a roof ( 2 ), a short-circuit ( 3 ) between the ground plane and the roof and an excitation means ( 4 ), the four elementary IFA antennae being distributed around an axis (Oz) in a first set of two IFA antennae having substantially equivalent elementary radiations and a second set of two IFA antennae having equivalent elementary radiations, the excitation means ( 4 ) of the four elementary IFA antennae being fed by radiofrequency signals of like amplitude whereof the phases follow a law which is substantially progressive in quadrature by rotation around the axis.
1. A device including an antenna operative at a wavelength λ, comprising four elementary IFA antennas, each elementary IFA antenna comprising a ground plane, a roof, a short-circuit between the ground plane and the roof and an excitation means, the four elementary IFA antennas being distributed around an axis in a first set of two IFA antennas having substantially equivalent far field elementary radiations and a second set of two IFA antennas having substantially equivalent far field elementary radiations,
the excitation means of the two IFA antennas of the first set being aligned along a first alignment axis substantially perpendicular to the axis and the excitation means of the two IFA antennas of the second set being aligned along a second alignment axis substantially perpendicular to the axis, the first alignment axis and the second alignment axis crossing at a right angle at one point of the axis,
the excitation means of the four elementary IFA antennas being fed by radiofrequency signals of like amplitude whereof the phases follow a law which is substantially progressive in quadrature by rotation around the axis (0°, 90°, 180°, 270°), and
the diameter of the device including the antenna being less than λ/4.
2. The antenna according to claim 1 , in which the two elementary IFA antennas of a same set of two antennas are identical and symmetrical relative to the axis.
3. The antenna according to claim 2 , in which the four elementary IFA antennas are all identical.
4. The antenna according to claim 1 , in which the roofs of the four elementary IFA antennas are distributed on a flat surface substantially perpendicular to the axis.
5. The antenna according to claim 4 , in which the roofs of the four elementary IFA antennas are substantially inscribed in a circle.
6. The antenna according to claim 4 , in which the roofs of the four elementary IFA antennas are substantially inscribed in an ellipsis.
7. The antenna according to claim 1 , in which the roofs of the four elementary IFA antennas are distributed on a substantially conical closed surface.
8. The antenna according to claim 1 , in which the roofs of the four elementary IFA antennas are distributed on a surface whereof the generatrix is parallel to the axis (Oz).
9. The antenna according to claim 8 , in which the surface is a cylindrical surface having a cross-section in the form of a circle, or a square, or a rectangle.
10. The antenna according to claim 1 , in which the roofs of the four elementary IFA antennas are formed by metallizations realized on a same substrate (S).
11. The antenna according to claim 1 , in which the ground planes of the four elementary IFA antennas are formed by a same conductive layer.
12. The antenna according to claim 1 which comprises means for switching the progressive law in quadrature between a first direction of rotation around the axis and a second direction of rotation around the axis, opposite the first direction.
13. The antenna of claim 1 , said antenna being coupled to transmitter and a sensor for measuring a measurable quantity, the antenna configured to transmit a measurement of the measurable quantity in the form of a modulation of an electromagnetic wave emitted by the transmitter.
14. Device according to claim 1 , in which the size of an antenna is less that λ/5.
15. Device according to claim 1 , in which the roofs of the antennae are distributed on a surface perpendicular to the axis, and in which the patterns forming the roofs of the antennae are folded, the short-circuit of each antenna being place at the periphery of the surface and the open-circuit of each antenna being place near the axis.