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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
  • H01Q1/243—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
  • H01Q5/30—Arrangements for providing operation on different wavebands
  • H01Q5/307—Individual or coupled radiating elements, each element being fed in an unspecified way
  • H01Q5/342—Individual or coupled radiating elements, each element being fed in an unspecified way for different propagation modes
  • H01Q5/357—Individual or coupled radiating elements, each element being fed in an unspecified way for different propagation modes using a single feed point

Definitions

• the present invention relates, in general, to radio transmission devices, in particular portable radiotelephones, and it relates more particularly to antennas which are produced using the microstrip technique to be included in such devices.
• Such an antenna includes a patch which is typically formed by etching a metal layer. It is called in English by specialists "microstrip patch antenna” for "patch antenna of the microstrip type".
• the microstrip technique is a planar technique which is applicable both to the production of lines transmitting signals and to that of antennas realizing a coupling between such lines and radiated waves. It uses conductive tapes and / or pads formed on the upper surface of a thin dielectric substrate. A conductive layer extends over the lower surface of this substrate and constitutes a mass of the line or the antenna.
• Such a patch is typically wider than such a ribbon and its shapes and dimensions constitute important characteristics of the antenna.
• the shape of the substrate is typically that of a rectangular flat sheet of constant thickness and the pellet is also typically rectangular.
• the thickness of the substrate can widen the passband of such an antenna and that the patch can take various forms and for example be circular.
• the electric field lines extend between the ribbon or the patch and the ground layer crossing the substrate.
• This technique is distinguished from various other techniques using, also, conductive elements on a thin substrate, and in particular that of coplanar lines in which the electric field is established on the upper surface of the substrate and in a symmetrical manner between d on the one hand a central conductive tape and on the other hand two conductive pads located on either side of this tape from which they are respectively separated by two slots.
• a loop slot antenna a patch is surrounded by a continuous conductive pad from which it is separated by a slot.
• the antennas produced according to these techniques typically constitute, although not necessarily, resonant structures capable of being the seat of standing waves allowing coupling with waves radiated in space.
• each such resonance can be described as being a standing wave formed by the superposition of two progressive waves propagating in two opposite directions on the same path, these two waves resulting from the alternative reflection of the same progressive electromagnetic wave to the two ends of this path.
• this latter wave propagates in an electromagnetic line which would be constituted by the mass, the substrate and the pellet and which would define a linear path devoid of width.
• such a wave has wave surfaces which extend transversely over the entire section which is offered to them by the antenna so that this description simplifies reality in a sometimes excessive manner.
• this path can be straight or curved. It will be designated hereafter by the expression “resonance path”.
• the frequency of the resonance is inversely proportional to the time taken by the progressive wave considered above to travel this path.
• a first type of resonance can be called “half wave”.
• the length of the resonance path is typically substantially equal to half a wavelength, that is to say half the wavelength of the progressive wave considered above.
• the antenna is then called "half-wave".
• This type of resonance can be defined in general by the presence of an electric current node at each of the two ends of such a path, the length of which can therefore also be equal to said half-wavelength multiplied by an integer other than one. This number is typically odd.
• the coupling with the radiated waves is made at at least one of the two ends of this path, these ends being located in the regions where the amplitude of the electric field prevailing in the substrate is maximum.
• a second type of resonance which can be obtained within the framework of this same technique can be called "quarter wave". It differs from said half-wave type on the one hand by the fact that the resonance path typically has a length substantially equal to a quarter wave, ie a quarter of the wavelength defined above.
• the resonant structure must include a short circuit at one end of this path, the word short circuit designating a connection connecting the ground and the patch.
• this short circuit must have an impedance small enough to be able to impose such a resonance.
• This type of resonance can be defined in general by the presence of an electric field node fixed by such a short circuit in the vicinity of one edge of the patch and by an electric current node located at the other. end of the resonance path.
• the length of the latter can therefore also be equal to an integer number of half-wavelengths added to said quarter wavelength.
• the coupling with the waves radiated in space is made on an edge of the patch in a region where the amplitude of the electric field through the substrate is sufficiently large.
• Resonances of other more or less complex types can be established in antennas of this kind, each resonance being characterized by a distribution of the electric and magnetic fields which oscillate in a zone of space including the antenna and the immediate vicinity of this one. They depend in particular on the configuration of the pellets, the latter being able in particular to present slots, possibly radiative.
• the distribution of the fields in the first antenna is substantially identical to a distribution that can be induced in an identical area belonging to the patch of a second antenna.
• This second antenna is identical to this first antenna within the limits of this area except that this second antenna is free from the short circuit in question.
• the patch of this second antenna extends not only over the area already mentioned which then constitutes a main area of this second antenna, but also over a complementary area.
• the node appearing in the second antenna also constitutes a node for the resonance of the first antenna.
• a node will hereinafter be called “virtual” because it is located in an area which is situated outside the patch of this antenna and in which therefore no electric field or magnetic likely to allow direct observation of the presence of this node.
• connection assembly comprising a connection line which is external to this antenna and which ends in a system of coupling integrated into this antenna to couple this line to a resonant structure of this antenna.
• the resonances of this antenna also depend on the nature and location of this system.
• the connection assembly is often designated as being a supply line for this antenna.
• the present invention relates to various types of devices such as portable radiotelephones, base stations for the latter, automobiles and airplanes or air missiles.
• portable radiotelephone the continuous nature of the lower mass layer of an antenna produced using the microstrip technique makes it possible to easily limit the power of radiation intercepted by the body of the user of the device.
• the antenna can be conformed to this profile so as not to show any annoying additional aerodynamic drag.
• This invention relates more particularly to the case where an antenna produced using the microstrip technique must have the following qualities:
• a first such known antenna is described in patent document US-A-4,766,440 (Gegan).
• the patch 10 of this antenna has a generally rectangular shape allowing this antenna to have two half-wave resonances whose paths are established along a length and a width of this patch. Furthermore, it has a curved U-shaped slot which is entirely internal to this patch. This slit is radiative and reveals an additional mode of resonance establishing itself along another path. It also makes it possible, by a suitable choice of its shape and its dimensions, to bring the frequencies of the resonance modes to desired values which gives the possibility of emitting a wave with circular polarization thanks to the association of two modes with the same frequency and crossed linear polarizations.
• the coupling device has the form of a line which is produced according to the microstrip technique but which it is also said to be coplanar, this because the microstrip extends in the plane of the patch and enters between two notches of the latter.
• This device is provided with impedance transformation means to adapt it to the different input impedances respectively presented by the line at the different resonance frequencies used as working frequencies.
• a second known antenna differs from the previous one by the use of a single resonance path. It is described in patent document US-A-4,771, 291 (LO et al). Its patch has punctual short-circuits and slots extending along straight lines inside the patch. These slots and short-circuits make it possible to reduce the difference between two frequencies corresponding to two resonances having said path in common but two respective mutually different modes which are designated by the numbers (0,1) and (0,3), c ' that is to say that this common path is occupied by a half wave or by three half waves depending on the mode considered. The ratio between these two frequencies can thus be lowered from 3 to 1.8.
• the point short-circuits are formed by conductors crossing the substrate.
• a third known dual-frequency antenna differs from the previous ones by the use of quarter-wave resonance. It is described in an article: IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATONAL SYMPOSIUM DIGEST, NEWPORT BEACH, JUNE 18-23, 1995, pages 2124-2217 Boag et al "Dual Band Cavity-Backed Quarter-wave Patch Antenna".
• a first resonant frequency is defined by the dimensions and characteristics of the substrate and the patch of this antenna.
• a resonance of substantially the same type is obtained at a second frequency on the same resonance path through the use of an adaptation system.
• the present invention has in particular the following aims: - make it possible to simply produce a dual-frequency antenna,
• this device comprising:
• a signal processing device adapted to be tuned in frequency in two working bands extending respectively around two predetermined center frequencies for transmitting and / or receiving an electrical signal in each of these two bands
• an antenna connection assembly including electrical conductors connecting this processing member to this antenna to couple said electrical signal to radiated waves, this antenna comprising:
• the separating slot is located, over its entire length except in the vicinity of its origin, or at least over most of its length, and on both sides, at a distance from the periphery of the patch greater than the distance from the bottom of this slot at this periphery.
• the origin of the separating slit is close to said short-circuit so as to give the two said resonances two respective resonant paths, both extending from this short-circuit, one of these two paths s 'extending only in said body and the other extending in this body and in said tail.
• FIG. 1 represents the patch of an antenna produced according to a first mode of implementation of this invention.
• FIG. 2 represents the patch of an antenna produced according to a second embodiment of this invention.
• FIG. 3 represents a perspective view of a transmission device including the antenna, the patch of which is represented by FIG. 2.
• FIG. 4 represents a partial view of a rear side of an antenna produced according to a third mode of implementation of this invention.
• FIG. 5 represents the patch of an antenna produced according to a fourth embodiment of this invention, this mode being generally preferred.
• FIG. 6 represents the separating slot of the patch of FIG. 5.
• the resonant structure of an antenna according to this invention comprises the following elements:
• a dielectric substrate 2 having two mutually opposite main surfaces extending in directions defined in this antenna and constituting horizontal directions DL and DT, these directions being able to depend on the considered zone of the antenna.
• This substrate can have various shapes as previously exposed. Its two main surfaces respectively constitute a lower surface S1 and an upper surface S2.
• a lower conductive layer extending for example over the whole of this lower surface and constituting a mass 4 of this antenna.
• this patch has a length and a width extending in two horizontal directions constituting a longitudinal direction DL and a transverse direction DT, respectively, and its periphery can be considered as constituted by four edges extending two by two roughly in these two directions.
• length and width usually apply to the two mutually perpendicular dimensions of a rectangular object, the length being greater than the width, it should be understood that the patch 6 can deviate widely from the shape of such a rectangle without departing from the scope of this invention.
• One of these edges generally extends in the transverse direction DT and constitutes a rear edge including two segments 10 and 11.
• a front edge 12 is opposite this rear edge.
• Two lateral edges 14 and 16 join this rear edge to this front edge.
• this short circuit electrically connecting the patch 6 to ground 4 from segment 10 of the rear edge of this patch.
• this short circuit is formed by a conductive layer S extending over a wafer surface of the substrate 2, a surface which is typically plane and then constitutes a short plane -circuit.
• it consists of three discrete components R, L and D connected in parallel between the ground 4 and the patch 6. In each of these modes, it requires at least one resonance of the antenna to present an electric field node at least virtual in the vicinity of segment 10 and to be of the quarter wave type. This resonance and its frequency will be called hereinafter "primary resonance" and "primary frequency”.
• Said rear, front and side edges and the longitudinal and transverse directions are defined by the position of such a short circuit insofar as this short circuit is sufficiently large, that is to say in particular where its impedance is sufficiently low. to impose on the antenna the existence of a resonance having such an electric field node.
• the antenna further includes a coupling system.
• This system comprises on the one hand a main conductor constituted by a coupling strip C1 extending over the upper surface S2 of the substrate.
• This ribbon is connected to the patch 6 at a connection point 18 which can for example be located on the head edge 14. The distance from the rear edge 10 to this point constitutes a connection dimension.
• This system also comprises a ground conductor constituted by layer 4. It is part of a connection assembly which connects the resonant structure of the antenna to a signal processing device T, for example to excite one or more several resonances of the antenna from this member in the case where it is a transmitting antenna.
• the connection assembly typically includes a connection line which is external to the antenna.
• This line can in particular be of the coaxial type, of the microstrip type or of the coplanar type.
• FIG. 1 it has been symbolically represented in the form of two conducting wires C2 and C3 respectively connecting the ground 4 and the ribbon C1 to the two terminals of the signal processing member T. But it should be understood that this line would be in practice preferably performed in the form of a microstrip line or a coaxial line.
• the signal processing device T is adapted to operate at predetermined working frequencies which are at least close to the useful resonant frequencies of the antenna, that is to say which are included in passbands centered on these frequencies. resonance. It can be composite and then include an element permanently tuned to each of these working frequencies. It may also include an element that can be tuned to the various working frequencies. Said primary resonant frequency constitutes such a useful resonant frequency.
• the separating slot 17 extends from the rear edge 10, 11 of the patch to a bottom 15 of this slot, at a distance from the lateral edges 14 and 16 and from the front edge 12.
• the body 31 is therefore connected to the tail 33 by a tail connection passage 32.
• This passage has a length W2 extending in the direction DT and a width L2 extending in the direction DL between the head edge 14 and the bottom 15
• This body has a width W1 extending in the direction DT
• the slot 17 separates the rear edge on the one hand a body base 10 belonging to the body 31 and provided with the short circuit S and on the other hand, a base tail 11 belonging to tail 33, this tail base having a width W4 extending in the transverse direction DT.
• a vertex 13 of this tail is formed by the junction zone of this tail with the passage 32.
• a length of this tail extends in the direction DL from the base 11 to this vertex.
• a width of this tail is defined at each point of this length and extends in the direction DT.
• the widths of the body, of the passage and of the tail of the patch are uniform and an antenna of which the patch is thus produced can satisfy the needs generally felt in the field of radiotelephones in the sense that its primary and secondary frequencies may be in a ratio close to two.
• the width W4 of the base 11 of the tail 33 is greater than the width W2 of its apex 13.
• the width of this tail increases from its apex to its base passing through several intermediate values between the widths of this vertex and this base. More preferably, this growth in the width of the tail is continuous growth, and this tail has, for example, the shape of a trapezium whose large and small base are formed by the base and the top of this tail.
• the length L3 of the tail 33 is between 50% and 100% of the length L1 of the body 31, the ratio F2 / F1 of the secondary frequency F2 to the primary frequency F1 being between 1, 9 and 2, 1.
• the width W4 of the base 11 of the tail 33 is between 50% and 150% of the width W1 of the body 31.
• this effective width W3 is preferably between 10% and 70% of the width W4 of this base.
• the substrate 2 includes in at least part of its area two mutually distinct and superimposed layers, these two layers respectively constituting a lower dielectric layer 21 carrying the mass 4 and an upper dielectric layer 22 carrying the patch 6.
• This upper dielectric layer advantageously has a greater relative permittivity and possibly a smaller thickness than those of this lower dielectric layer and these two layers extend over the entire area of the substrate.
• Such a difference between the two layers has the advantage of increasing the efficiency of radiation at long distance.
• the antenna includes a conductive insert 23 extending in a fraction of the area of the patch 6 between the two lower dielectric layers 21 and upper 22.
• This fraction advantageously extends under the passage 32 and in the vicinity of the front edge 12.
• this same advantage could be obtained using a tongue formed by a thin sheet of copper extending in continuity with the body 31 and projecting from it and the substrate from the front edge 12.
• a tongue can be bent at will on this edge to move away from the plane of the patch and to approach more or less the vertical edge plane of the substrate. It is the choice of its inclination which then allows the desired frequency adjustment.
• the length and width of the substrate are respectively indicated in the longitudinal directions DL and transverse DT.
• the mass of the antenna covers the underside of the substrate.
• the short circuit S occupies the entire width of the base of the body 31.
• composition of the conductive layers copper, - thickness of these layers: 17 microns,
• - substrate length 30mm
• - substrate width 20mm
• composition of the substrate laminate based on fluoropolymer such as PTFE having a relative permittivity ⁇ r equal to 5 and a dissipation factor tg ⁇ equal to 0.002,
• composition of a lower layer 21 of the substrate low permittivity foam, thickness of this lower layer: 2 mm
• composition of an upper layer 22 of the substrate laminate based on fluoro-polymer such as PTFE having a relative permittivity ⁇ r equal to 5 and a dissipation factor tg ⁇ equal to 0.002
• the primary radiative edge is the front edge 12, which corresponds to a primary resonance of the quarter wave type having an electric field node on the segment 10.
• the observed value of the primary frequency suggests, however, that the path of this resonance has been somewhat lengthened by the presence of the passage 32 and the tail 33. If the length of the patch was imposed, such an extension would make it possible to give the primary frequency a more weak in the presence of the slot 17 than in its absence. In the typical case where it is the value of this primary frequency which is imposed, the presence of this slot makes it possible to reduce the length of the patch, which is an advantage generally sought after. This advantage would remain if this antenna were included in a single-band transmission device which would only use the primary resonance of this antenna.
• the secondary radiative edge is constituted by the base 11 of the tail 33.
• the observed value of the secondary frequency suggests that the path of the secondary resonance follows, from the short circuit S, not only the length of the body 31, but also that of the passage 32 and of the tail 33 and that this resonance is essentially a half-wave type resonance, the length of its path being however close to three quarters of the wavelength with two electric field nodes, one of which would be imposed by the short circuit S and the other would be close to the top 13 of the tail 33.
• the primary radiative edge is the base 11 of the tail 33 and the observed value of the primary frequency suggests that the primary resonance path of the quarter-wave type borrows, from the short-circuit S, not only the length of the body 31, but also that of the passage 32 and of the tail 33.
• the presence of the slot 17 therefore makes it possible to reduce the length of the patch more sharply than in the first embodiment. .
• the secondary radiative edge is constituted by the front edge 12.
• the observed value of the secondary frequency suggests that the path of the secondary resonance extends over the length of the body 3 and that this resonance is essentially a quarter wave type resonance.
• the body 31 is provided with a protrusion 34 extending in the plane of the patch 6, projecting from the head edge 14, in the vicinity of the front edge 12
• Such a projection 34 is also shown in FIG. 5 for the fourth embodiment of the invention, mode in which it is formed projecting from the rear edge 10 in the vicinity of the head edge 14
• the short circuit has an impedance large enough at the primary frequency for the resonance primary is significantly different from a resonance which could be induced in the antenna near this frequency if this short circuit had no impedance.
• This impedance is at the same time small enough at this frequency to fix an electric field node of this resonance in the vicinity of the base 10 of the body 31, this node being at least virtual.
• This arrangement has the drawback of complicating the creation of the short circuit.
• it sometimes has the major advantage that a suitable choice made according to this invention for the components of such an impedance allows the resonances of an antenna or its physical characteristics to be better suited to the use of this antenna than if the short circuit had no impedance.
• the impedance of this short circuit has an inductive component L.
• an inductive component makes it possible to show a resonance of the quarter wave type having a virtual electric field node located behind the base 10 , that is to say outside of the patch 6. It thus provides an advantage which is to make it possible to further reduce the length of this patch when the frequency F1 of the primary resonance is imposed.
• the impedance of the short circuit can also have a resistive component R, such a component providing the advantage of making it possible to increase the widths of the passbands of the antenna. It may also have a controlled component produced by a diode D provided with a decoupling capacitor connected in parallel and not shown. Such a component has the advantage of enabling the frequency or bandwidth of an antenna resonance to be controlled. Such components are easily produced using at least one discrete component connected between the patch 6 and the ground 4.
• the substrate 2 includes in at least part of its area two mutually distinct and superimposed layers, these two layers respectively constituting a lower dielectric layer 21 carrying the mass 4 and an upper dielectric layer 22 carrying the patch 6.
• This upper dielectric layer advantageously has a greater relative permittivity and possibly a thickness smaller than those of this lower dielectric layer and these two layers extend over the entire area of the substrate A such difference between the two layers has the advantage of increasing the efficiency of radiation at long distance. In addition it facilitates an adjustment of the resonance frequencies.
• the antenna includes a conductive insert 23 extending in a fraction of the area of the patch 6 between the two lower dielectric layers 21 and upper 22. This fraction advantageously extends under the passage 32 and in the vicinity of the front edge 12.
• the antenna produced according to the fourth embodiment of this invention differs from the previous antennas in particular in that the origin O of the separating slot 17 and the short circuit S are close to the common point at the two rear 10 and tail 16 sides, the edges of this separating slot being concave on the side of the body 31 and convex on the side of the tail 33, so as to give the two said resonances two respective resonance paths both extending from this short circuit, one of these two paths extending only in this body and the other extending in this body and in this tail.
• the antenna coupling strip C1 and the protrusion 34 are connected to the rear edge 10. This antenna has the particular advantage of having a large bandwidth.
• compositions and values will be indicated below by way of example.
• the lengths and widths are indicated respectively in the longitudinal directions DL and transverse DT.
• X-coordinates "x” and ordinates "y” are measured respectively in these same directions from the origin of the separating slot located on the periphery of the patch.
• the mass of the antenna covers the underside of the substrate.
• - primary resonance frequency: F1 910 MHz,
• - thickness of these layers 200 microns
• - composition of the substrate foam having a relative permittivity ⁇ r equal to 1 and a dissipation factor tg ⁇ equal to 0.0001
• the front edge 12 and the trailing edge 16 each constitute a primary radiative edge and the observed value of the primary frequency suggests that the primary resonance path of the quarter-wave type follows, from from the short circuit S, not only from the body 31 to the passage 32, but also a length of the tail 33.
• the head edge 14, the rear edge of the slot 17 and the rear edge 10 of the patch each constitute a secondary radiative edge and the observed value of the secondary frequency suggests that the path of the secondary resonance is contained in the body 31 and that this resonance is of a relatively complex type.
• This invention also relates to an antenna as previously described. It is particularly applicable to the realization of a radiotelephony system.
• a radiotelephony system includes base stations and portable terminals and it can be carried out within the framework of a GSM standard using frequencies close to 900 MHz and / or within the framework of a DCS standard using frequencies close to 1800 MHz.
• base stations or portable terminals may each include a transmission device according to this invention.
• the antenna is able to operate in a high frequency band in the vicinity of said secondary frequency and in a low frequency band in the vicinity of said primary frequency.
• the processing unit T is then tunable on four mutually distinct working frequencies which constitute:
• It is capable of transmitting or receiving a signal when it is tuned to a said transmit frequency or to a said receive frequency, respectively.
• This invention makes it possible to give each of these two frequency bands a sufficient width, not only to avoid crosstalk between the spectral emission and reception channels situated in this band, but also to allow to choose between several possible positions of these channels. in this band.
• the low frequency band corresponds to the GSM standard and the high frequency band to the DCS standard.
• Base stations and / or dual-mode terminals are thus produced economically, ie capable of operating within the framework of any of these standards.
• the high transmit and receive frequencies can be 1750 and 1840 MHz respectively and the frequencies transmission and reception frequencies can be 890 and 940 MHz respectively.

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