Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
  • H01Q9/0421—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with a shorting wall or a shorting pin at one end of the element
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/56—Details of data transmission or power supply, e.g. use of slip rings
  • A61B6/563—Details of data transmission or power supply, e.g. use of slip rings involving image data transmission via a network
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment

Definitions

• the present invention relates to a mixed antenna comprising a wire-plate antenna and a PIFA antenna.
• One of the antennas is connectable to an electrical generator, the other antenna being coupled to the first by capacitive coupling.
• the invention applies in particular in the field of telecommunications, WiFi antennas for example.
• a digital radiological cassette makes it possible to store one or more digital images of a patient illuminated in transparency by X-rays, without necessarily having to place the patient in a strictly delimited mechanical environment, the cassette being portable and therefore easily manipulable. If moreover this cassette is wireless, mobility and ease of use are increased. But the removal of the wire requires transmitting the digital image to the hospital information system via a transmitting radio antenna. This poses practical difficulties.
• a certain mechanical robustness of the cassette is necessary to ensure reliability in case of fall or shock, as well as for protection against external electromagnetic disturbances.
• the antenna is placed inside, it is the worst case electromagnetic, or outside, it is the worst case for the mechanical protection, the influence of this metal mass prevents the use of antennas flat on PCB. Since the radio constraints are considered to be stronger with respect to the mechanical stresses, the antenna must necessarily be placed outside the metal shell. However, the space available on the outside is very small and defines a surface rather than a volume. The antenna must also be protected from shocks and fluids commonly used in hospitals to clean instruments.
• the IEC 60601-1-2 standard limits the instantaneous radiation power emitted (EIRP) at a maximum of 1 milliwatt.
• EIRP instantaneous radiation power emitted
• This power limitation makes it difficult to use a commercial antenna such as a "WiFi” type antenna, whose nominal power is generally of the order of 10O mW. They can easily be limited to 1 milliwatt, but then the metal environment constituted by the cassette causes a critical mismatch of the antenna at this power level.
• the "WiFi" antennas of commerce are therefore definitely not suitable for use in a digital radiological cassette. But to make a "WiFi" antenna dedicated to use in a digital radiological cassette is not without posing many technical difficulties.
• WiFi Wired fidelity
• IEEE 802.1 1a, IEEE 802.1 1b, IEEE 802.1 1g or IEEE 802.1 1 n standards known under the trade name of "WiFi" have emerged, for example, IEEE 802.1 1a, IEEE 802.1 1b, IEEE 802.1 1g or IEEE 802.1 1 n.
• the IEEE 802.1 1b and IEEE 802.1 1g standards provide multiple communication channels between 2.4 and 2.5 GHz.
• the IEEE 802.1 1 standard has provided several channels between 5 and 6 GHz.
• a generally versatile WiFi link compatible with at least the three IEEE 802.1 1a, IEEE 802.1 1b and IEEE 802.1 1g standards, requires the use of a multi-band antenna capable of sending and receiving information on several frequency bands. Many constraints arise for such an antenna.
• the antenna must be omnidirectional, or at least it must have a radiation pattern as uniform as possible in space. Because the user does not have to worry about the relative position or the orientation of the cassette with respect to the receiving WiFi terminal.
• the antenna must have a certain transmission range, the range often depending on the context of use. For example, WiFi cards from Commerce to install on laptops or desktops are variable scope, the user can choose his card (and the budget he wants to devote to it) depending on the conditions of use as the area to cover, the number of floors or the thickness of the walls.
• the range of an antenna is directly proportional to its transmission power, which we know is subject to a regulatory limitation of 1 milliwatt in hospital. Under such conditions, meeting both the range requirements and both the antenna power limitation is complicated. Although this is essentially a problem of medical standard, it should also be remembered that the antenna must be an integral part of a portable device powered by a rechargeable battery system and therefore limited power .
• the antenna must therefore have excellent performance, that is to say, to return in the form of radiation a maximum of the energy supplied to it by the battery.
• the antenna must be multi-band, at least adapted to different frequencies of WiFi standards. Now, in general, an antenna is adapted to a given frequency. At this given frequency, if the antenna is powered by a cable, it must radiate a maximum of this energy and return a minimum in the cable. Thus, if the power system has for example an impedance of 50 ohms, the antenna must also have an impedance of 50 ohms. This is easy to achieve for an antenna to work in a single frequency band, especially a narrow band. But it is much more difficult to achieve when the antenna has to work in several bands, possibly wide bands like the standard IEEE 802.1 1 a allowing large data rates.
• the antenna must also have a small footprint in order to be integrated into a portable device.
• antennas are particularly adapted to be integrated in various systems. But a digital radiological cassette is externally in the form of a metal shielding shell. If the 2D antenna is placed inside, it does not radiate outside. If placed outside, the metal shell disrupts its radiation considerably, rendering it ineffective.
• An alternative solution that could be considered is the use of an antenna mounted on a ground plane, also called “3D antennas". More bulky, such antennas are usually used to illuminate large volumes, an entire building for example. These are, for example, antennas known under the Anglo-Saxon antenna designation "PIFA" (Planar Inverted F Antenna). But to obtain a multi-band operation with a PIFA antenna, it must have sufficient dimensions so that its radiating plane can include slots. These dimensions are incompatible with the width, length and thickness available on the outside of a digital radiological cassette. In the volume allocated to the antenna, only a single-band PIFA antenna could hold.
• Another alternative solution that could be envisaged is the use of a 3D antenna according to patent EP 0 667 984 B1. Indeed, a wire-plate antenna with several radiating planes according to this patent can cover several frequency bands. But it has a size too large, especially in thickness, to be assembled outside a digital radiological cassette.
• a technical problem to which the present invention proposes to respond is to provide an antenna having similar characteristics in terms of radiation to known 3D antennas, but offering a much smaller footprint.
• the invention is in particular to provide a multiband antenna with a very small footprint.
• the subject of the invention is a mixed antenna comprising a wire-plate antenna and a PIFA antenna.
• One of the antennas is connectable to an electric generator.
• the other antenna is coupled to the first by capacitive coupling.
• the antenna can be multiband frequency.
• the wire-plate antenna and the PIFA antenna may each comprise a radiating plate, the two plates may each be arranged on a radiating element and the two elements may each be arranged on a ground plane.
• the two radiating plates can be in the same plane separated by a slot of constant width, the slot ensuring the capacitive coupling of the two plates.
• the two radiating elements can be arranged on the same ground plane.
• the slot between the two plates can form a pattern, the pattern increasing the length of the slot and its capacity.
• the pattern formed by the slot between the two plates may form a rectangular projection of one of the plates in the other plate.
• a central strand of a coaxial cable may be connected to one of the radiating plates and the peripheral braid of the coaxial cable may be connected to the ground plane.
• the central strand can connect the plate to the electrical generator and the peripheral braid can connect the ground plane to the electrical ground.
• the central strand of the coaxial cable can connect the radiating plate of the PI FA antenna to the electric generator.
• the antenna can be encased in a plastic frame, the frame can be attached to the outside of a digital radiological cassette, the plastic frame isolating the antenna disturbances caused by the metal casing of the cassette.
• the main advantages of the invention are that it requires the implementation of standard techniques for manufacturing 3D antennas. Its final cost is quite comparable to that of a PIFA antenna or a conventional wire-plate antenna.
• FIG. 1 by an exploded view, an example of a mixed antenna according to the invention intended to be integrated on a digital radiological cassette;
• FIG. 2 a perspective view of the same example of a mixed antenna according to the invention;
• FIG. 4 by a graph, the radiation diagram of the same example of a mixed antenna according to the invention.
• FIG. 1 illustrates, by an exploded view, an example of a mixed antenna according to the invention, intended to be integrated on a digital radiological cassette. It comprises for example a radiating plate Pi of conductive material of rectangular shape and comprising for example a projection S forming a square pattern on one of its short sides.
• the plate Pi is mounted for example on a radiating element E 3 in conductive material and in the form of a block, the element E 3 supporting the plate Pi via a conductive connection.
• the element E 3 is arranged for example on a metal ground plane P 3 , in direct contact.
• the plate Pi, the element E 3 and the metal ground plane P 3 form a wire-plate antenna.
• the mixed antenna according to the invention comprises, for example, a radiating plate P 2 made of conducting material of rectangular shape and comprising, for example, an indentation E forming a rectangle pattern on one of his little sides.
• the long sides of the rectangle forming the notch E are slightly larger than the sides of the square forming the projection S.
• the plate P 2 is mounted for example on a radiating element Ei in conductive material and in the form of a cube, the element Ei supporting the plate P 2 via a conductive connection.
• the element Ei is for example disposed on the metal ground plane P 3 , in direct contact. But a separate mass plan could have been considered.
• a radiating element E 2 in conductive material and shaped block is fixed under the plate P 2 , it is not in contact with the ground plane P 3 .
• the plate P 2 , the elements E 1 and E 2 , and the metal ground plane P 3 form a PIFA antenna.
• a coaxial cable of suitable section may for example supply the PIFA antenna electric current through the element E 2 .
• a hole is then drilled in the ground plane P 3 opposite element E 2 , the diameter of the hole being substantially equal to the section of the cable.
• the central strand of the cable passes through the hole without making contact with the ground plane P 3 . It is welded by its end to the element E 2 .
• the braided sheath of the coaxial cable can be advantageously welded at the edges of the hole in the ground plane P 3 .
• the central strand then provides electric current, the braided sheath being connected to the electrical ground.
• the mixed antenna according to the invention performs a coupling of the wire-plate antenna and the PIFA antenna.
• the dimensions of the elements E 1 and E 3 are such that the plates Pi and P 2 are in the same plane, the element E 1 and the element E 3 being arranged in such a way that the plates Pi and P 2 are separated by a slot F.
• the projection S fits noncontact into the notch E, the slot F being of low and constant width. In this way, as soon as the PIFA antenna is supplied with electric current by the central strand of the coaxial cable, induced currents appear in the wire-plate antenna.
• the wire-plate antenna is coupled to the PIFA antenna by capacitive coupling.
• a PIFA antenna or a wire-plate antenna are not characterized by their feeding mode. They can indifferently be powered by electrical contact or by capacitive coupling. What characterizes them is rather their mode of resonance. Indeed, the resonance mode of a wire-plate antenna is of electric type, the currents concentrating rather on the ground wire, that is to say on the radiating element E 3 supported by the ground plane P 3 in the present embodiment.
• the radiation of a wire-plate antenna is omnidirectional in azimuth.
• the antenna behaves like a single vertical polarization radiating monopole, the polarization of the radiated field being perpendicular to the so-called "short-circuit" wire of the antenna, that is to say perpendicular to the radiating element E 3 in the present embodiment.
• the resonance mode of a PIFA antenna is of the electromagnetic type, the currents are dispersed over the entire structure of the antenna.
• the antenna behaves like a radiant dipole in a uniform total field throughout the space. This uniformity is due to the sum of the two polarizations radiated by this antenna, a horizontal polarization resulting from the currents flowing on the plate P 2 and a vertical polarization from the so-called "short-circuit" plate of the antenna.
• the slot F between the two antennas does not have a resonance role, but that it advantageously provides the coupling function.
• the pattern that it forms advantageously makes it possible to increase its capacity with respect to a straight slot without a pattern.
• the slot F of the mixed antenna according to the invention can not be assimilated to the resonant slot of a conventional PIFA antenna.
• the two types of antennas therefore differ by their very principle of operation. It should also be noted that the position of the elements E 1 and E 3 relative to their respective radiating plates P 2 and Pi plays a decisive role in the resonance mode of the antenna formed.
• the element Ei To make a PIFA antenna, the element Ei must be rather eccentric with respect to the radiating plate P 2 .
• the element E 3 To make a wire-plate antenna, the element E 3 must be rather centered with respect to the radiating plate Pi. Incidentally, this relative position determines the function of the element in the antenna formed, the function of the element Ei of the antenna PIFA not being at all comparable to the role of the element E 3 of the wire-plate antenna.
• the cumulative area of the plates Pi and P 2 and the adjacent terraces is substantially identical in width to the surface of the ground plane P 3 on which they rest and slightly shorter in length.
• Bi, B 2 , B 3 and B 4 blocks of a dielectric material are sandwiched between the plates Pi and P 2 , the blocks Bi and B 2 being on either side of the element Ei, the blocks B 2 and B 3 being on either side of the element E 2 , the blocks B 3 and B 4 being on either side of the element E 3 .
• the blocks Bi, B 2 , B 3 and B 4 do not exceed the sandwich formed by the plates Pi and P 2 and the ground plane P 3 .
• the mixed antenna according to the invention for a digital radiological cassette is advantageously encased in a molded plastic chassis C.
• the plastic chassis C makes it possible, on the one hand, to fix the hybrid antenna according to the invention to the outer shield of a digital radiological cassette, not shown in FIG. 1.
• the plastic chassis C also makes it possible to isolate the antenna of the large metal mass that constitutes the shielding shell, it thus prevents the radiation of the antenna is disturbed. Its role is therefore decisive in the application to a digital radiological cassette. It also seals the antenna and protects it against shocks.
• FIG. 2 illustrates in a perspective view the example of a mixed antenna according to the invention for a digital radiological cassette already illustrated in FIG. 1.
• the antenna is completely assembled. Only the radiating plates Pi and P 2 are visible, flush with the plastic frame C and separated by the slot F.
• the mixed antenna according to the invention is ready for assembly on a cassette via the frame C.
• FIG. 3 illustrates, by a design diagram, the dimensions of the mixed antenna according to the invention for a digital radiological cassette already illustrated in FIGS. 1 and 2.
• the diagram shows the very small size of the mixed antenna according to the invention.
• the radiating plates Pi and P 2 In the top view appear the radiating plates Pi and P 2 , the protrusion S and the notch E are separated by the slot F, and the elements Ei, E 2 and E 3 .
• the profile view appear not only the radiating plates Pi and P 2 and the elements E 1 , E 2 and E 3 , but also the ground plane P 3 .
• the ground plane P 3 has a length of only 71.4 millimeters.
• the plates Pi and P 2 and the ground plane P 3 have a width of only 15 millimeters.
• the projection S and the notch E the plates Pi and P 2 have a length of 39 and 22 millimeters respectively.
• the projection S has the shape of a square of 3 millimeters of side.
• the notch E extends 5 millimeters in the width of the plate P 2 , it penetrates 3 millimeters in the length of the plate P 2 .
• the gap F between the plates Pi and P 2 is only 1 millimeter wide.
• the plates Pi and P 2 are spaced only 5 millimeters from the ground plane P 3 , these 5 millimeters corresponding to the height of the elements E 1 and E 3 supporting the plates P 2 and Pi respectively. Since the element E 2 only has a height of 4 millimeters, it is spaced 1 millimeter from the ground plane P 3 .
• each of the elements E 1 , E 2 and E 3 has a surface in the horizontal plane which is negligible compared to the plate that it supports (this is the case of E 1 and E 3 ), or with respect to the plate that supports it (this is the case of E 2 ).
• each of the elements E 1 and E 3 is positioned substantially in the middle of the width of the plate that it supports, E 2 is positioned substantially in the middle of the width of the plate that supports it.
• the element Ei is 6 millimeters from each of the two lateral edges of the plate P 2 .
• Element E 2 is 4 millimeters from each of the two lateral edges of plate P 2 .
• Element E 3 is 2 millimeters from each of the two edges
• neither the element Ei nor the element E 2 are positioned near the middle of the length of the plate. P 2 .
• the element Ei is positioned at 4 millimeters from the edge of the plate P 2 opposite the plate Pi
• the element E 2 is positioned at 3 millimeters from the other edge of the plate P 2 adjacent to the plate Pi at the edge of the notch E.
• the element E 3 is positioned relatively close to the middle of the length of the plate Pi.
• the element E 3 is positioned 21 millimeters from the edge of the plate Pi opposite the plate P 2 , the plate Pi being 39 millimeters long in total.
• FIG. 4 illustrates the radiation pattern of the example of mixed antenna according to the invention for a digital radiological cassette already illustrated in FIGS. 1, 2 and 3.
• the abscissa represents the frequency in gigahertz.
• the ordinate represents the reflection coefficient of the antenna in decibels, commonly called S1 1.
• An antenna is considered adapted to a given frequency if, at this frequency, its reflection coefficient S11 is less than -6 decibels. It appears that the dimensions of the wire-plate antenna formed by the radiating plate Pi, the radiating element E 3 and the ground plane P 3 enable it to radiate effectively at a frequency fb, g of the order of 2, 4 to 2.5 gigahertz, the coefficient S1 1 having at the frequency f b , g a minimum at almost -25 decibels.
• the antenna is therefore adapted to the frequency f b , g ., which corresponds to the wavelength of the WiFi standards 802.1 1b and 802.11g.
• the smaller dimensions of the PIFA antenna formed by the radiating plate P 2 , the element E 1 and the ground plane P 3 enable it to radiate effectively in a much higher frequency range f a of the order of 5 and 6 gigahertz, the coefficient S1 1 having at the frequency f has a minimum at almost -30 decibels.
• the antenna is therefore adapted to the frequency f a , which corresponds to the WiFi standard 802.1 1a waveband.
• the mixed antenna according to the invention is particularly suitable for portable applications of various WiFi standards, such as a digital radiological cassette for example.

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• 2007
  • 2007-03-20 FR FR0753933A patent/FR2914113B1/fr active Active
• 2008
  • 2008-03-11 US US12/531,991 patent/US20100177013A1/en not_active Abandoned
  • 2008-03-11 CA CA002681307A patent/CA2681307A1/en not_active Abandoned
  • 2008-03-11 WO PCT/EP2008/052865 patent/WO2008125399A1/fr active Application Filing
  • 2008-03-11 JP JP2009553999A patent/JP2010521913A/ja active Pending
  • 2008-03-11 CN CN200880008816A patent/CN101682118A/zh active Pending
  • 2008-03-11 EP EP08717612A patent/EP2143168A1/de not_active Withdrawn

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