EP1699108B1 - Antenna with switchable radiating planes and terminal comprising the same - Google Patents

Description

The present invention relates to a switchable plane radiant surface type antenna (s) and a mobile communication terminal comprising this antenna.

In the field of mobile telephony, several standards exist. The most widely distributed at the moment is the GSM mobile system (Global System for Mobile Communication). It was established under the ETSI (European Telecommunications Standards Institute). With regard to the present invention, it provides in particular the transmission on a frequency band between 880 and 960 MHz (for the GSM system called GSM 900) and on a frequency band between 1710 and 1880 MHz (for the so-called system). GSM1800 or DCS as Digital Communication System: mobile communication system). This standard is especially used in Europe, Africa, the Middle East and Asia.

Two variants of the GSM 1800 and GSM 900 of this standardized GSM system, mainly used on the North American continent, exist respectively, the first under the name of GSM1900 or PCS (Personal Communication System) because it provides for transmission on a frequency band between 1850 and 1990 MHz and the second under the name of GSM 850 or GSM 800 for transmission over a frequency band between 823 and 894 MHz.

There is also a standard called 3 ^rd generation and called UMTS (Universal Mobile Telecommunications System: universal mobile communication system). Its transmission frequency band is higher than those of the GSM standard.

Due to the multiplicity of these standards and to the very strong demand of the users to be able to communicate from their mobile terminal whatever their location on the planet, the radio equipment of today's mobile terminals allow to send and receive according to many of these standards. Thus, the radio equipment of the so-called dual-band terminals make it possible to send and receive in the frequency bands of the GSM 900 and GSM 1800, those of the so-called tri-band terminals make it possible to send in the frequency bands of the GSM 900 , the GSM1800 and GSM1900 and those so-called quad-band terminals in the four frequency bands mentioned above.

For the same reasons as those mentioned above, the terminals that support the UMTS 3 ^rd generation must include radio equipment that can transmit and receive in both the frequency bands of the GSM mobile telephone system and those of UMTS telephone system. Thus, they must include, inter alia, radio frequency equipment capable of transmitting and receiving low frequencies located in the frequency bands of GSM 800 and GSM 900, respectively, of the high frequencies located in the frequency bands of GSM 1800 and GSM, respectively. 1900 as well as very high frequencies in the UMTS frequency band.

Among the radio frequency equipment used in mobile terminals, the antenna is an element whose characteristics are essential to the proper functioning of the rest of the terminal. It is known to use antennas of PIFA type (Planar Inverted Folded Antenna: folded and inverted plane antenna) which offer good far-field radiation performance as well as a decrease in local near-field radiation compared to that of conventional antennas. whip or helicoidal. In general, a PIFA type antenna consists of a ground plane and a radiation surface located at a distance from this ground plane. The surface is generally hollowed out in one or more places so as to form slots. Such an antenna resonates according to one or more frequencies whose value or values are determined by the dimensions of the radiating surface, by the position and by the dimensions of the slot or slots, by the positioning of these slots relative to one another. etc.

For a PIFA-type antenna to be efficient over several frequency bands, it is known to use switching elements that make it possible to adapt its topology according to whether it operates in a band of frequencies, for example low frequencies, or in another, for example high. Such an antenna, in a known embodiment, has a slot which opens on an edge of its radiating surface and which is short-circuited at a point of its length by a switching element. As a result, depending on the open or closed state of this switching element, the effective length of the slot, that is to say the length of the slot involved in determining the resonance frequencies of the antenna, can take two distinct values. For example, such a switching element will make it possible to modify, by switching, the high resonant frequencies of the antenna.

The prior art US 6,501,427 describes a multi-frequency patch antenna having a plurality of peripheral zones that can be switched to a central power zone.

Fig. represents the example of a switchable multiband PIFA antenna as just described. This antenna AE1 comprises a ground plane PLM and a so-called radiation surface S located parallel to and away from the ground plane PLM. This radiation surface S is split by a gap space OP, opening into an edge of the radiation surface S. The radiation surface S is connected to the ground potential of the ground plane PLM via a point PM said ground point and at a PE excitation point to be excited by an RF radio frequency signal. The gap space OP is shunted, at a predetermined distance from the edge opening of the slot OP, by a switching element SW having two operating states: an open state where the impedance at its terminals is high and a closed state where the impedance at its terminals is weak creating a shunt, at its level, of the slot OP.

In the open state, the switching element SW has no effect, so that the equivalent topology of the antenna AE1 is that represented by the Fig. 1b . The antenna AE1 then resonates at a low frequency defined in particular by the surface delimited by the longest path PA1 connecting the excitation point PE to the mass point PM, that is to say by the path delimiting the radiation surface S and the slot space OP of total length L1. For example, the defining elements this topology, in particular the length of the slot space and the dimensions of the radiation surface S, are determined so that this low frequency is between 823 and 894 MHz, thus covering the GSM 800 mode. The AE1 antenna also resonates at a high frequency defined mainly by the slot space OP of length L1. For example, the elements defining this topology are determined so that this high frequency is between 1710 and 1880 MHz, thus covering the GSM1800 mode.

In the closed state, the switching element SW shunts the slot space OP to the length L2 of the edge of the radiating surface S, so that the equivalent topology of the antenna AE1 is now that represented in FIG. Fig. 1 C . In this case, the antenna AE1 then resonates at a low frequency defined in particular by the surface delimited by the longest path PA2 connecting the PE excitation point to the mass point PM shorter than the path PA1, so that this frequency is higher than previously: it is now between 880 and 960 MHz thus covering the GSM 900. The antenna AE1 also resonates at a high frequency defined mainly by the slot space OP of effective length L2 shorter than the length L1 so that the high frequency is now higher, for example between 1850 and 1990 MHz, thus covering the GSM1900 mode.

Thus, the antenna AE1 as represented in FIG. Fig. 1a resonates in two low frequency bands, for example, around 800 and 900 MHz and two high frequency bands around 1800 and 1900 MHz.

Moreover, to evaluate the performance of an antenna, it is common to measure the Stationary Wave Rate (TOS), that is to say the ratio of the amplitude of a wave emitted by this antenna to a frequency given by the amplitude of this same wave reflected on an external body. The measurement of the TOS makes it possible to know the losses by power mismatch of the antenna. For example, a TOS of - 4 decibels (dB) at the edge of bands corresponds to a loss of 40% of the power of the antenna. In this case, the operation of the antenna is greatly disturbed by the nearby environment, such as the approximation of a finger of the antenna. A TOS is considered suitable for a given frequency as soon as it is lower in absolute value than - 5 dB (30% loss).

The Fig. 1d represents, as a function of frequency, the standing wave ratio (TOS) of a quad-band AE1 antenna such as that shown in FIG. the. It can be noted that this antenna covers the four GSM modes. However, the TOS at the edge of the high and low bands is of the order of -4 dB. This significant loss is the result of the design of the antenna where each mode of operation given by a state of the switching element is such that a low frequency is associated with a high frequency, association requiring a compromise between the definition of the the topology of the antenna and the value of the TOS of this antenna. Indeed, in the example of the antenna given to the Fig. 1a the gap space OP is positioned near the excitation point PE, which favors a proper adjustment of the high frequency values. On the other hand, this arrangement is detrimental to the width of the bandwidths for the low frequencies which would require that this slot space OP be as far as possible away from this excitation point PE.

Thus, the aim of the invention is to define a switchable multi-band antenna whose structure is such that it makes it possible to decouple the adjustment of its low resonant frequencies from the adjustment of its high resonance frequencies but also of decouple the tunings of the high resonant frequencies between them while maintaining a value of the band edge TOS which is relatively high in absolute value.

To do this, the present invention relates to an antenna comprising a ground plane intended to be at a ground potential and a radiation surface intended to be subjected to a radiofrequency signal at an excitation point and to be connected to said ground plane. in a mass point. It is characterized in that said radiating surface consists of a first zone including said mass point, a second zone including said excitation point and at least one other additional zone, said zones being isolated from each other. others continuously and coupled to the operating frequency of said antenna at spaces formed therebetween with the exception of at least one slot space, and in that said antenna comprises a first polarization switching element whose a first terminal is connected to said first zone and the second terminal to said second zone and at least one other polarization switching element whose first terminal is connected to said first zone and the second terminal to one of the other zones; said second zone and said further one or more other zones being intended to be respectively subjected to polarization potentials desdi ts switching elements for controlling the switching state of said elements of corresponding switching, each switching element passing through said one or more slot spaces.

According to one embodiment, said switching elements are diodes, the terminals of said switching elements connected to said first zone being the cathode and the other terminals connected to said second zone or to one of said other additional zones being the anode .

Advantageously, the arrangement of the zone relative to the said or each additional zone is such that the point of application of the polarization potential of the corresponding switching element is geographically close to the said ground point.

According to a first embodiment of the present invention, the slot space opens at one of its ends on an edge of the radiation surface, said first switching element passes through said slot space at said end, and a second switching element traverses said space away from said end.

According to a second embodiment of the present invention, the slot space opens at both ends on two edges of the radiation surface, said first switching element and a second switching element passing through said space respectively at said ends.

Advantageously, at least one of said zones is subdivided into at least two sub-zones separated from each other by a space forming a slot or a slot portion and interconnected by a DC link element.

According to a third embodiment of the present invention, an area other than the first area is subdivided into a first sub-area and a second sub-area separated from each other by a slot space or a slot portion and interconnected. by a DC component, said first area is recessed from another slot space opening into said slot space and said second subarea of said sub-area adjoins said slot, and a switching element passes through said other space forming a slot, its anode being connected to the second sub-area of said subdivided zone and its cathode to said first zone.

According to a variant of one of the embodiments of the present invention, each of the switching elements is a diode and an impedance element tuned to the parasitic diode impedance is associated in parallel with each of the switching elements.

According to another variant of one of the embodiments of the present invention, the control point of the or each additional zone is connected to the ground potential via a capacitive element.

According to another variant of one of the embodiments of the present invention, the polarization signal applied to the second zone is superimposed on the radio frequency signal.

According to one embodiment of the invention, said zones are coupled to the operating frequency of said antenna by capacitors made by partially overlapping without contact of said zones.

The present invention also relates to a mobile communication terminal which is characterized in that it comprises an antenna defined above.

• La Fig. 1a représente une antenne quadri-bandes de l'état de la technique.
• Les Fig. 1b-c représentent les deux modes de fonctionnement d'une antenne quadri-bandes de l'état de la technique.
• La Fig. 1d représente le TOS d'une antenne quadri-bande de d'état de la technique.
• La Fig. 2 représente une antenne multi-bande commutable selon l'invention.
• La Fig. 2a représente une réalisation d'un élément de couplage radiofréquence entre deux zones.
• La Fig. 3a représente une antenne multi-bande commutable selon un premier mode de réalisation de l'invention.
• Les Fig. 3b-d représentent les quatre modes de fonctionnement de l'antenne représentée à la Fig. 3a.
• La Fig. 3e représente le TOS de l'antenne multi-bande représentée à la Fig 3a.
• La Fig. 4a représente une antenne multi-bande commutable selon un deuxième mode de réalisation de l'invention.
• Les Fig. 4b-d représentent les quatre modes de fonctionnement de l'antenne représentée à la Fig. 4a.
• La Fig. 4e représente le TOS de l'antenne multi-bande représentée à la Fig 4a.
• La Fig. 5a représente une antenne multi-bande commutable selon un troisième mode de réalisation de l'invention.
• Les Fig. 5b-d représentent quatre modes de fonctionnement de l'antenne représentée à la Fig. 5a.
• La Fig. 5e représente le TOS de l'antenne multi-bande représentée à la Fig 5a.
• La Fig. 6 représente une variante de l'un des modes de réalisation de la présente invention.
• La Fig. 7 représente un élément de commutation associé à un élément d'impédance accordée.

The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being given in relation to the attached drawings, among which:

• The Fig. 1a represents a four-band antenna of the state of the art.
• The Fig. 1b-c represent the two modes of operation of a quad-band antenna of the state of the art.
• The Fig. 1d represents the TOS of a state-of-the-art quad-band antenna.
• The Fig. 2 represents a switchable multi-band antenna according to the invention.
• The Fig. 2a represents an embodiment of a radiofrequency coupling element between two zones.
• The Fig. 3a represents a switchable multi-band antenna according to a first embodiment of the invention.
• The Fig. 3b-d represent the four modes of operation of the antenna shown in Fig. 3a .
• The Fig. 3rd represents the TOS of the multi-band antenna represented in Fig 3a .
• The Fig. 4a represents a switchable multi-band antenna according to a second embodiment of the invention.
• The Fig. 4b-d represent the four modes of operation of the antenna shown in Fig. 4a .
• The Fig. 4th represents the TOS of the multi-band antenna represented in Fig 4a .
• The Fig. 5a represents a switchable multi-band antenna according to a third embodiment of the invention.
• The Fig. 5b-d represent four modes of operation of the antenna shown in Fig. 5a .
• The Fig. 5th represents the TOS of the multi-band antenna represented in Fig 5a .
• The Fig. 6 represents a variant of one of the embodiments of the present invention.
• The Fig. 7 represents a switching element associated with a tuned impedance element.

The Fig. 2 represents a switchable multiband antenna AE2 according to the invention. It comprises a radiation surface S intended to be subjected to an RF radiofrequency signal at a PE excitation point and a PLM ground plane intended to be connected to a ground potential at a mass point PM and located parallel and at a distance of the radiation surface S. The radiation surface S consists of a first zone Z ₁ including the mass point PM, a second zone Z ₂ including the excitation point PE and at least one other zone additional (here n-2 zones respectively denoted Z ₃ , ..., Z _n ). The zones Z ₁ , Z ₂ , Z ₃ ,..., Z _n are isolated from each other continuously and coupled to the operating frequency of the antenna AE 2 at the spaces between them E ₁ , E ₂ , ..., E _n-2 and E _n-1 , with the exception of at least one space forming at least one slot (here, only a slot space OP). The radiofrequency coupling between two zones Z _i and Z _j separated from each other by a space E _i-1 is achieved by radiofrequency coupling elements C ₁ , C ₂ , C ₃ , C ₄ ,..., C _p , C _q , ... C _n-1 , C _n , C _{n + 1} , and C _{n + 2} , ... such as capacitors, shunting the spaces E ₁ , E ₂ , ..., E _n-2 and E _n-1 . The values of these capacitors are such that, at the operating frequencies of the antenna, the impedance of these capacitors is very low and it can be considered that two zones Z _i and Z _j separated by a space E _k are interconnected at the level of the capacitors shunting the space E _k . On the other hand, continuously, the zones Z _i and Z _j are isolated from one another.

We have shown Fig. 2a a radiofrequency coupling element C _k of two zones Z _i and Z _j partly overlapping and spaced apart from one another by a space E. The zones Z _i and Z _j are formed on the same substrate SU.

The antenna AE2 also comprises (n-1) polarization switching elements SW ₁ ,..., SW _n-1 crossing the space OP. Each of these elements of Polarization switching may for example be a PIN diode. It is recalled that when a positive potential difference is applied between the two terminals called anode and cathode of a diode, the diode is said to be forward biased and the diode is then equivalent to a very low resistance of the order of 1 Ohm . In a dual manner, when this potential difference is negative, the diode is said to be reverse biased and is then equivalent to a very low value capacitance, of the order of 0.1 pF, that is to say, a very high impedance for the operating frequencies of the antenna.

The cathode of each of the (n-1) polarization switching elements SW ₁ , ..., SW _n-1 is connected to the first zone Z ₁ while the anode is connected to one of the zones Z ₂ , ..., Z _n . The zones Z _2, ..., Z _n are intended to be respectively subjected to polarization potentials Si _1, ..., _n-1 If in the respective points called control points PC _1, ..., PC _{n -1 of} said switching elements for controlling the switching state (closed state or open state) of said switching elements SW ₁ , ..., SW _n-1 . Thus, each of the potentials Si ₁ , ..., Si _n-1 is applied to the anode of a switching element SW ₁ , ..., SW _n-1 and the cathode of the latter is at the potential of the mass via zone Z ₁ . Therefore, each of the (n-1) polarization switching elements SW _i is in a closed state as soon as the bias potential Si _i is greater than the ground potential and in an open state as soon as this bias potential is lower than mass potential.

According to an alternative mode, the anode of each of the (n-1) polarization switching elements SW ₁ ,..., SW _n-1 is connected to the first zone Z ₁ while the cathode is connected to one zones Z ₂ , ..., Z _n . Thus, each of the potentials Si ₁ , ..., Si _n-1 is applied to the cathode of a switching element SW ₁ , ..., SW _n-1 and the anode thereof is at the potential of the mass via zone Z ₁ . Therefore, each of the (n-1) polarization switch elements SW _i is in a closed state as soon as the bias potential Si _i is lower than the ground potential and in an open state as soon as this bias potential is greater than mass potential.

Embodiments of the present invention are described below in the case where each of the (n-1) polarization switching elements SW _i is in a closed state as soon as the bias potential Si _i is greater than the ground potential and in an open state as soon as this bias potential is lower than the ground potential. However, it will be understood that the invention also relates to embodiments in which at least one or each polarization switching element SW _i is in a closed state as soon as the bias potential Si _i is less than the ground potential and in an open state as soon as this bias potential is greater than the ground potential.

It will be noted that the bias potentials Si ₁ ,..., Si _n-1 have extremely low variation frequencies to be compared to the operating frequencies of the antenna so that it is possible to consider that they are continuous.

The Fig. 3a represents a switchable multi-band antenna according to a first embodiment of the invention. The antenna AE3 comprises a radiation surface S intended to be subjected to an RF radiofrequency signal at a PE excitation point and a PLM ground plane intended to be connected to a ground potential at a mass point PM and located in parallel. and away from the radiation surface S. The radiation surface S is substantially rectangular in shape and consists essentially of three zones Z ₁ Z ₂ and Z ₃ (n = 3). The zone Z ₁ has a recess, for example of rectangular shape, in which are housed the zones Z ₂ and Z ₃ , for example substantially of rectangular shape. The zones Z ₁ , Z ₂ and Z ₃ are spaced apart from one another and this results in the formation of a gap OP forming a single slot opening at one of its ends between, on the one hand, a side of the recess of the zone Z ₁ and, on the other hand, the two zones Z ₂ and Z ₃ , the formation of a space E ₁ between the zones Z ₂ and Z ₃ , as well as the formation of a space E ₂ between the second side of the recess of the zone Z ₁ and the zone Z ₃ . The zone Z ₁ is intended to be connected to the ground potential at a mass point PM and the zone Z ₂ is subjected to an RF radiofrequency signal which is applied at a PE excitation point.

The zone Z ₃ is radially coupled, on the one hand, to the zone Z ₂ by radiofrequency coupling elements C ₁ and C ₂ , shunting the space E ₁ and, on the other hand, at the zone Z ₁ by radio frequency coupling elements C ₃ and C ₄ , shunting the space E ₂ .

The space OP is crossed by two polarization switching elements SW ₁ and SW ₂ whose cathodes are connected to the zone Z ₁ . The anode of the polarization switching element SW ₁ is connected to the zone Z ₂ and the anode of the polarization switching element SW ₂ is connected to the zone Z ₃ .

Zone Z ₂ is subjected to a bias potential Si ₁ at a control point PC ₁ , which, in the embodiment shown, is superimposed on the excitation point PE. As for the zone Z ₃ , it is subjected to a bias potential Si ₂ at a control point PC ₂ which is, from a radio frequency point of view, connected to the potential of mass via a capacitor C _m ¹ and which is geometrically close to the mass point PM.

The bias potentials Si ₁ and Si ₂ of the switching elements SW ₁ and SW ₂ are distinct, so that four operating modes of the antenna AE 3 can be obtained by combining their respective open / closed states.

The first of these four modes of operation corresponds to the case where the two switching elements SW ₁ and SW ₂ are in an open state, so that the equivalent topology of the antenna AE 3 is that represented in FIG. Fig. 3b . The antenna AE3 then resonates at a high frequency defined mainly by the slot space OP of length L1. For example, the elements defining this topology are determined so that this frequency is between 1710 and 1880 MHz, thus covering the GSM1800 mode. The antenna AE3 also resonates at a low frequency defined in particular by the surface delimited by the longest path PA3 connecting the excitation point PE to the mass point PM, that is to say by the radiation surface S recessed from a slot space OP of length L1.

The second of these four modes of operation corresponds to the case where the switching element SW ₁ is in a closed state while the switching element SW ₂ is in an open state. The equivalent topology of the AE3 antenna is that represented by the Fig. 3c . The antenna AE3 then resonates at a low frequency defined in particular by the surface delimited by the longest path PA4 connecting the excitation point PE to the mass point PM, that is to say by the radiation surface S. By for example, the elements defining this topology are determined so that this low frequency is included in the bandwidth of frequencies between 823 and 960 MHz, thus covering the GSM 800 and the GSM 900.

The third of these four operating modes corresponds to the case where the two polarization switching elements SW ₁ and SW ₂ are in a closed state. The equivalent topology of the antenna AE3 is then that which is represented at the Fig. 3c described above, identical to the previous case.

The fourth and last mode of operation corresponds to the case where the switching element SW ₁ is in the open state and the switching element SW ₂ is in a closed state. The equivalent topology of the antenna AE ₂ is that represented by the Fig. 3d . The antenna AE3 then resonates at a high frequency defined mainly by the slot space OP of length L2 shorter than the L1 length so that the high frequency is now higher than the high frequency obtained according to the first mode, for example between 1850 and 1990 MHz, thus covering the GSM 1900. The antenna AE3 also resonates at a low frequency defined in particular by the surface delimited by the longest path PA5 connecting the excitation point PE to the mass point PM, that is to say by the radiation surface S recessed from the slot space OP of length L2.

The Fig. 3rd represents, as a function of frequency, the TOS of this quad-band antenna AE3 shown in FIG. Fig. 3a . It can be noted that this antenna covers the four GSM modes. The TOS at the edge of low frequency bands is high in absolute value, of the order of -6 dB. On the other hand, the TOS at the edge of the high frequencies is low in absolute value, of the order of -4 dB.

As we have just seen, an antenna such as the antenna AE3 shown in FIG. Fig. 3a operates in four modes. The first and fourth modes decouple the adjustment of the high frequencies from each other and the second (or third) mode allows decoupling the adjustment of the low frequencies from the adjustment of the high frequencies. In addition, because of the geographical proximity of the control point PC ₁ and the mass point PM, the setting to the ground potential of the point PC ₁ , and the arrangement of the zones Z ₁ , Z ₂ and Z ₃ , the TOS rate bordering low frequency bands is excellent.

The Fig. 4a represents a switchable multi-band antenna according to a second embodiment of the invention. Like the previous antenna, the antenna AE4 comprises a radiation surface S intended to be subjected to an RF radiofrequency signal at a PE excitation point and a PLM ground plane intended to be connected to a transmission potential. mass at a mass point PM and situated parallel to and at a distance from the radiation surface S. The radiation surface S is of substantially rectangular shape and is also composed of three zones Z ₁ , Z ₂ and Z ₃ (n = 3 ). Zone Z ₁ is now subdivided into a first subarea Z ₁₁ and a second subfield Z ₁₂ . The zones Z ₂ and Z ₃ are located respectively on either side of the subzone Z ₁₁ . The zones Z ₁ , Z ₂ , Z ₁₁ and Z ₁₂ are substantially rectangular in shape and are spaced apart from one another. This results in the formation of a gap OP forming a single opening slot at its two ends between, on the one hand, the sub-zone Z ₁₂ and, on the other hand, the two zones Z ₂ and Z ₃ and the sub-zone Z _12. -zone Z ₁₁ . This also results in the formation of a space E ₁ between the zone Z ₂ and the sub-zone Z ₁₁ and a space E ₂ between the zone Z ₃ and the subfield Z ₁₁ . In addition, another space OP1 forming a slot opening on the OP space is practiced in the sub-area Z ₁₂ .

Furthermore, the Z sub-zone ₁₁ is radiofrequency-coupled to the zone Z ₂ by radiofrequency coupling elements C ₁ and C ₂ , shunting the space E ₁ and is coupled to the zone Z ₃ by radiofrequency coupling elements C ₃ and C ₄ , shunting the space E ₂ . From a continuous point of view, these zones Z ₂ , Z ₁₁ and Z ₃ are isolated from each other.

Zone Z2 is subjected to an RF radiofrequency signal which is applied at a PE excitation point while Z sub-zone ₁₁ is connected to the ground potential at a mass point PM.

The space OP is traversed by two polarization switching elements SW ₁ and SW ₂ at each of its ends. The cathode of each of them is connected to the subzone Z ₁₂ . The anode of the polarization switching element SW ₁ is connected to the zone Z ₂ and the anode of the polarization switching element SW ₂ is connected to the zone Z ₃ .

The subfield Z ₁₁ is connected to the sub-area Z ₁₂ by a continuous connection element IE ₁ passing through the slot OP space, for example of the inductive type, the function of which is to put the two sub-zones Z ₁₁ and Z ₁₂ at the same DC potential (or very low frequency compared to the operating frequency of the antenna), and isolate them from each other in the operating frequencies of the antenna. Thus, the cathode of each of the polarization switching elements SW ₁ and SW ₂ is at a continuous potential whose value is equal to that of the continuous potential of the sub-area Z ₁₂ , ie to the potential of mass to which Subfield Z ₁₁ is subject.

Zone Z ₂ is subjected to a bias potential Si ₁ at a control point PC ₁ , which, in the embodiment shown, is superimposed on the excitation point PE. Zone Z ₃ is itself subjected to a bias potential Si ₂ at a control point PC ₂ , which is, from a radio frequency point of view, connected to the ground potential via a capacitor C _m ¹ and which is geometrically close to the mass point PM.

It will be noted that the fact that the zones Z ₂ and Z ₃ are on both sides of the zone Z ₁₁ implies that the points PC ₁ and PC ₂ (PE) are close to the point PM, allowing better impedance matching. of the antenna.

The polarization potentials Si1 and Si2 of the switching polarization elements SW ₁ and SW ₂ are distinct, so that four operating modes of antenna AE4 can be obtained by combining their respective open / closed states.

The first of these four modes of operation corresponds to the case where two switching elements SW ₁ and SW ₂ are in the closed state, so that the equivalent topology AE4 antenna is that which is shown in Fig. 4b . The antenna AE4 then resonates at a low frequency defined in particular by the surface delimited by the longest path PA6 connecting the excitation point PE to the point of mass PM, that is to say by the radiation surface S. For example, the elements defining this topology are determined so that this frequency is between 823 and 960 MHz, thus covering GSM 800 and 900.

The second of these four modes of operation corresponds to the case where the switching element SW ₁ is in the open state and the switching element SW ₂ is in the closed state, so that the equivalent topology of the antenna AE4 is the one represented at Fig. 4c . The antenna AE4 then resonates at a high frequency defined mainly by the slot OP space L1 length and slot OP1 space. For example, the elements defining this topology are determined so that this high frequency is between 1710 and 1910 MHz, thus covering the GSM 1800 and the transmission part of the GSM1900. The antenna AE4 also resonates at a low frequency defined in particular by the surface delimited by the longest path PA7 between the excitation point PE and the mass point PM, that is to say by the radiation surface S recessed of the gap space OP of length L1 and slot space OP1.

The third of these four operating modes corresponds to the case where the switching element SW ₁ is in the closed state and the switching element SW ₂ is in the open state, so that the equivalent topology of the antenna AE 4 is substantially symmetrical to that which is represented at Fig. 4c in that the slot space OP is now shunted at the switching element SW ₁ and no longer at the switching element SW ₂ .

The fourth and last mode of operation corresponds to the case where the two switching elements SW ₁ and SW ₂ are in the open state, so that the equivalent topology of the antenna AE 4 is that represented by the Fig. 4d . The antenna AE4 then resonates at a high frequency defined in particular by the surface delimited by the longest path PA8 between the excitation point PE and the mass point PM, that is to say by the area constituted by the zones Z ₁₁ , Z ₂ and Z ₃ . By for example, the elements defining this topology are determined so that this frequency is between 1920 and 2170, thus covering the UMTS and the reception part of the GSM 1900.

The Fig. 4th represents, as a function of frequency, the Rate of Standing Waves (TOS) of an AE4 antenna such as that represented in FIG. Fig. 4a . It can be noted that this antenna covers the four GSM modes and the UMTS mode. The TOS rate at the edges of high frequency bands is high in absolute value, of the order of -6 dB, and of the order of -5 dB at the edge of the low frequency bands.

An antenna such as the antenna AE4 shown in FIG. Fig. 4a operates in four modes. The second (or third) and fourth modes decouple the adjustment of the high frequencies between them and the first mode allows to decouple the adjustment of the low frequencies of the adjustment of the high frequencies. In addition, the separation of the zone Z ₁ into two sub-zones Z ₁₁ and Z ₁₂ and the introduction of a slot space OP 1 situated close to the edge of the radiation surface S makes it possible to obtain a high TOS in absolute value, of the order of -6 dB for low frequencies and a TOS of moderately high value in absolute value, of the order of -5 dB for high frequencies.

The Fig. 5a represents a switchable multiband antenna AE5 according to a third embodiment of the invention. In the same way as the previous embodiments, the antenna AE5 comprises a radiation surface S intended to be subjected to an RF radio frequency signal at a PE excitation point and a PLM ground plane intended to be connected to a potential of a weight mass PM and located parallel to and at a distance from the radiation surface S. The radiation surface S is of substantially rectangular shape and consists essentially of a first zone Z ₁ subdivided, like the preceding embodiment, in two sub-zones Z ₁₁ and Z ₁₂ , of a second zone Z ₂ which, now itself is subdivided into a sub-zone Z ₂₁ and a second sub-zone Z ₂₂ , and of a third zone Z ₃ . The Z ₂₁ subzone and the Z ₃ zone are located on either side of the Z ₁₁ sub-zone, producing the same advantage as that mentioned above in relation to the zones Z ₁₁ , Z ₂ and Z ₃ of the previous embodiment. Subzone Z ₁₂ is U-shaped within which subzone Z _{22 is located} . Areas Z _11, Z _12, Z _21, Z ₂₂ and Z ₃ are substantially rectangular and are spaced from each other. This results in the formation of a slot OP opening at its two ends between, on the one hand, the sub-area Z ₁₂ and the sub-area Z ₂₂ and, on the other hand, the zone Z ₃ and the sub-areas Z ₁₁ and Z ₂₁ , the formation of a space E ₁ between the sub-zone Z ₁₁ and the subfield Z ₂₁ , the formation of a space E ₂ between the sub-zone zone Z ₁₁ and the zone Z ₃ , and the formation of a space E ₃ between the sub-area Z ₂₂ and two of the three sides of the U-shape of the sub-area Z ₁₂ . In addition, the subzone Z ₁₂ is hollowed out of another gap OP1 forming slot opening on the slot space OP and along the third side of the U-shaped sub-area Z ₁₂ .

Subzone Z ₁₁ is radiofrequency coupled to sub-area Z ₂₁ by radio frequency coupling elements C ₁ and C ₂ , shunting space E ₁ , and is coupled to zone Z ₃ by radiofrequency coupling elements C ₃ and C ₄ , shunting the space E ₂ . Subfield Z ₁₂ and subfield Z ₂₂ are radiofrequency coupled by radiofrequency coupling elements C ₅ , C ₆ and C ₇ , shunting the space E ₃ .

Subfield Z ₂₁ is subjected to an RF radiofrequency signal which is applied at a PE excitation point while subfield Z ₁₁ is connected to the ground potential at a mass point PM.

Subfield Z ₁₁ is connected to sub-area Z ₁₂ by a continuous connection element IE ₁ passing through slot space OP. Subfield Z ₂₁ is connected to sub-area Z ₂₂ by a continuous connecting element IE ₂ also passing through slot space OP. Thus, the two sub-zones Z ₁₁ and Z ₁₂ are at the same DC potential (or very low frequency compared to the operating frequency of the antenna) and are isolated from each other in the operating frequencies of the antenna. It is the same zones Z ₂₁ and Z ₂₂ .

The space OP is crossed at one of its emergent ends by a polarization switching element SW ₂ whose anode is connected to the zone Z ₃ and the cathode is connected to the subarea Z ₁₂ . The open end of the space OP1 is crossed by another polarization switching element SW ₁ whose anode is connected to the Z sub-zone ₂₂ and the cathode is connected to the sub-zone Z ₁₂ .

Subfield Z ₂₁ is subjected to a bias potential Si ₁ at a control point PC ₁ , which, in the embodiment shown, is superimposed on the excitation point PE. This polarization potential is thus applied to the anode of the switching element SW ₁ and, through the connecting element IE ₂ , the cathode of said switching element SW ₁ being at the ground potential, through the sub-zone Z ₁₂ , the connecting element IE ₁ and the sub-zone Z ₁₁ as explained previously in FIG. Fig. 4a . Similarly, zone Z ₃ is subject to a potential of polarization Si ₂ at a control point PC ₂ which is therefore applied to the anode of the switching element SW ₂ , the cathode of which is at a ground potential via the sub-area Z ₁₂ , of the link element IE ₁ and subfield Z ₁₁ . The point PC ₂ is, from a radio frequency point of view, connected to the ground potential via a capacitor C _m ¹ and is geometrically close to the mass point PM.

The polarization potentials Si ₁ and Si ₂ of the switching polarization elements SW ₁ and SW ₂ are distinct, so that four operating modes of the antenna AE 5 can be obtained by combining their respective open / closed states.

The first of these four operating modes corresponds to the case where the two switching elements SW ₁ and SW ₂ are in the closed state, so that the equivalent topology of the antenna AE5 is that represented in FIG. Fig. 5b . The antenna then resonates at a low frequency defined in particular by the surface delimited by the longest path PA9 connecting the excitation point PE to the mass point PM, that is to say by the radiation surface S recessed from the OP gap forming slot L1 length. For example, the elements defining this topology are determined so that this frequency is between 823 and 960 MHz, thus covering the GSM 800 and 900. The antenna AE5 also resonates at a high frequency defined mainly by the OP space forming a slot of length L1. For example, the elements defining this topology are determined so that this frequency is between 1850 and 1990 MHz, thus covering the GSM 1900.

The second of these four modes of operation corresponds to the case where the switching element SW ₁ is in the open state and the switching element SW ₂ is in the closed state, so that the equivalent topology of the antenna AE5 is the one represented at Fig. 5c . The antenna AE5 then resonates at a high frequency defined mainly by the slit consisting of the slot OP space and the slot space OP1 L2 length longer than the length L1 of the gap OP space so well. that the high frequency is now lower than the high frequency obtained according to the first mode, for example between 1710 and 1880 MHz, thus covering the GSM 1800. The AE5 antenna also resonates at a low frequency defined in particular by the surface delimited by the longest path PA10 between the excitation point PE and the mass point PM, that is to say by the surface of radiation S recessed from the slot space OP and slot space OP1.

The third of these four modes of operation corresponds to the case where the two switching elements SW ₁ and SW ₂ are in the open state, so that the equivalent topology of the antenna AE5 is that represented in FIG. Fig. 5d . The antenna AE5 then resonates at a high frequency defined by the area delimited by the longest path PA11 between the excitation point PE and the mass point PM, that is to say by the surface constituted by the sub- zones Z ₂₁ and Z ₁₁ and zone Z3. For example, the elements defining this topology are determined so that this frequency is between 1920 and 2170 MHz, thus covering the UMTS mode.

The fourth and last mode of operation corresponds to the case where the polarized switching element SW ₁ is in the closed state and the polarization switching element SW ₂ is in the open state, so that the equivalent topology of the AE5 antenna is the one equivalent to that represented in Fig. 5d already commented previously.

The Fig. 5th represents, as a function of frequency, the Stationary Waveband Rate (TOS) of this AE5 straight-band antenna shown in FIG. Fig. 5a . It can be noted that this antenna covers the four GSM modes and the UMTS. In addition, the fact that the slot-forming space OP is crossed by only one polarization switching element, namely SW _1, the TOS edge of frequency bands is higher in absolute value, of the order -6 dB, whether for low frequencies or for high resonance frequencies.

As we have just seen, an antenna such as the antenna AE5 shown in FIG. Fig. 5a operates in four modes. The first, second and third (or fourth) modes are used to decouple the adjustment of the high frequencies from one another and the first mode makes it possible to decouple the adjustment of the low frequencies from the adjustment of certain high frequencies.

As can be seen in the ally of the preceding embodiments, it is the principle of the invention to subdivide an area into two sub-areas so as to form between them a space which can then form a slot or a part of a slot, said two sub-areas being connected to each other by a continuous connection element, such as an inductor, so that they are at the same DC potential. Zone Z ₁ subdivided into two subzones Z ₁₁ and Z ₁₂ constitutes a first mode of application of this principle. The same is true of zone Z ₂ subdivided into two sub-zones Z ₂₁ and Z ₂₂ . It will be understood that the subdivision in question could be done in more than two sub-areas.

According to a variant of one of the embodiments of the antenna described above, another gap-forming space OP2 is advantageously made in the zone Z ₁ according to the first embodiment of the antenna described in connection with FIG. Fig. 3a , where in the subzone Z ₁₂ according to the two other embodiments described in relation to the Figs. 4a and 5a . The slot space OP2 makes it possible to adjust resonant frequencies belonging to frequency bands having a high band edge TOS. The Fig. 6 represents this slot space OP2, in the case of the first embodiment of the antenna AE1 described in connection with the Fig. 3a .

According to another variant of one of the embodiments described above, each polarization switching element SW ₁ or SW ₂ is associated with an element, generally inductive, whose impedance is given to the parasitic impedance of the element. polarization switching when the latter is in a closed state. The Fig. 7 represents a polarization switching element SW _i associated with a tuned impedance element A consisting of an inductor 1 in series with a capacitive element CA. The impedance of this inductance 1 is given to the impedance of the parasitic capacitance of the switching element SW _i when the latter is in its open state. The AC capacitance, generally of greater value than that of the switching element, continuously decouples the tuned impedance element A.

Claims (12)

1. Aerial comprising an earth plane (PLM) intended to be at an earth potential and a radiation surface (S) intended to be subjected to a radiofrequency signal at an excitation point (PE) and to be connected to said earth plane (PLM) at an earth point (PM), the said radiation surface (S) being made up of a first zone (Z₁) including said earth point (PM), a second zone (Z₂) including said excitation point (PE) and at least one other supplementary zone (Z₃, Z_n), the said zones (Z₁, Z₂, Z₃, Z_n) being continuously isolated from one another and coupled to the operating frequency of said aerial at the level of spaces formed between them, the said aerial comprising a first polarisation switching element (SW₁) a first terminal of which is connected to said first zone (Z₁) and the second terminal to said second zone (Z₂) and at least one other polarisation switching element (SW₂, SW_n-1) a first terminal of which is connected to said first zone (Z₁ and the second terminal to one of the other supplementary zones (Z₃, Z_n), the second zone (Z₂) and the said other supplementary zone or zones (Z₃, Z_n) being intended to be respectively subjected to polarisation potentials of said switching elements in order to control the switching state of said corresponding switching elements (SW₁, SW₂, SW_n-1) , characterised in that the first zone (Z₁) has a recess which accommodates said second zone (Z₂) and said at least one other supplementary zone (Z₃, Z_n), and in that at least one space forming an opening slot not coupled to the operating frequency is delimited by at least one edge of said first zone and at least one edge of each supplementary zone and in that each switching element (SW₁ SW₂, SW_n-1) crosses said slot-forming space or spaces.
2. Aerial according to claim 1, characterised in that the said switching elements are diodes, the terminals of said switching elements connected to said first zone (Z₁) being the cathode, and the other terminals connected to said second zone (Z₂) or to one of said other supplementary zones (Z₃, Z_n) being the anode.
3. Aerial according to claim 1 or 2, characterised in that the arrangement of the zone (Z₁ relative to the or each supplementary zone (Z₃, Z_n-1) is such that the point of application of the polarisation potential of the corresponding switching element (SW) is geographically close to said earth point (PM).
4. Aerial according to one of the preceding claims, characterised in that the slot-forming space (OP) opens at one of its ends onto an edge of the radiation surface (S), and in that said first switching element (SW₁) crosses said slot-forming space (OP) at said end, and a second switching element (SW₂) crosses said space (OP) at a distance from said end.
5. Aerial according to one of claims 1 to 3, characterised in that the slot-forming space (OP) opens at both its ends onto two edges of the radiation surface (S), and in that said first switching element (SW₁) and a second switching element (SW₂) respectively cross said space (OP) at the said ends.
6. Aerial according to one of the preceding claims, characterised in that at least one of said zones (Z₁, Z₂, Z₃, Z_n) is subdivided into at least two sub-zones (Z₁₁, Z₁₂, Z₂₁, Z₂₂) separated from one another by a space forming a slot or part of a slot and connected to one another by a continuous component connecting member.
7. Aerial according to one of the preceding claims, characterised in that a zone (Z₂, Z₃, Z_n) other than the first zone (Z₁) is subdivided into a first sub-zone (Z₂₁) and a second sub-zone (Z₂₂) separated from one another by a space forming a slot or part of a slot and connected to one another by a continuous component connecting member, in that the first zone (Z₁) is recessed in another slot-forming space (OP1) opening onto said slot-forming space (OP) and said second sub-zone of said subdivided zone adjacent to said slot (OP1), and in that a switching element crosses said other slot-forming space (OP1), its anode being connected to the second sub-zone (Z₂₂) of said subdivided zone and its cathode to said first zone (Z₁).
8. Aerial according to any one of the preceding claims, characterised in that each of the switching elements is a diode and in that an impedance element tuned to the parasitic diode impedance is associated in parallel with each of the switching elements.
9. Aerial according to any one of the preceding claims, characterised in that the control point (PC) of the or each supplementary zone (Z₃, Z_n) is connected to the earth potential via a capacitive element.
10. Aerial according to any one of the preceding claims, characterised in that the polarisation potential applied to the second zone (Z₂) is superimposed on the radiofrequency signal.
11. Aerial according to any one of the preceding claims, characterised in that, in order to be coupled to the operating frequency of said aerial, two zones (Z₁ Z₂, Z₃, Z_n) partially overlap, while being spaced from one another by a space.
12. Mobile communications terminal, characterised in that it comprises an aerial according to one of the preceding claims.

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