EP3352301A1 - Antenna for mobile communication device - Google Patents

Abstract

The invention relates to an antenna (2) comprising: an elongate conductive strip (22); an antenna socket (24); a connection (26) to ground; at least a first capacitive element (28) of adjustable capacity; and at least one first inductive element (32) connecting the conductive strip to the ground or at least one first inductive element (34) in series with the first capacitive element.

Description

Field

The present description generally relates to electronic devices and, more particularly, to antennas used by transmission circuits fitted to mobile communication devices. The present disclosure is more particularly directed to a short-circuited quarter-wave antenna (PIFA antenna - Planar Inverted-F Antenna) for mobile telecommunication equipment of the mobile telephony type.

Presentation of the prior art

A mobile phone antenna is generally disposed at the housing or shell of the phone so as not to be shielded by metal elements. The antenna is then connected to the internal electronic transmission circuits on the telephone.

The multiplication of the frequency bands that can be used in mobile phones and tablets leads to the provision of broadband and / or frequency-adjustable antennas.

summary

It would be desirable to have a radio frequency antenna architecture that can operate efficiently in different frequency bands.

It would be desirable to have a solution particularly suited to the frequency bands used in mobile telecommunication devices.

It would be desirable to have a solution adaptable to existing transmission circuits.

• une bande conductrice allongée ;
• une prise d'antenne ;
• une connexion à la masse ;
• au moins un premier élément capacitif de capacité réglable ; et
• au moins un premier élément inductif reliant la bande conductrice à la masse.

Thus, an embodiment provides an antenna comprising:

• an elongate conductive strip;
• an antenna socket;
• a connection to the ground;
• at least one first capacitive element of adjustable capacity; and
• at least one first inductive element connecting the conductive strip to ground.

According to one embodiment, the distance between the respective connection points of the first inductive element and the first capacitive element, to the band, is less than the distance between the connection point of the first inductive element and the connection to ground.

According to one embodiment, the first inductive element is in parallel with the first capacitive element.

According to one embodiment, the antenna further comprises a second inductive element in series with the first capacitive element.

• une bande conductrice allongée ;
• une prise d'antenne ;
• une connexion à la masse ;
• au moins un premier élément capacitif de capacité réglable ; et
• au moins un premier élément inductif en série avec le premier élément capacitif.

An embodiment also provides an antenna comprising:

• an elongate conductive strip;
• an antenna socket;
• a connection to the ground;
• at least one first capacitive element of adjustable capacity; and
• at least one first inductive element in series with the first capacitive element.

According to one embodiment, the antenna further comprises a second inductive element connecting the conductive strip to ground.

According to one embodiment, the distance between the respective connection points of the second inductive element and the series connection of the first capacitive element and the first inductive element to the band is less than the distance between the connection point of the second inductive element and the connection to the ground.

According to one embodiment, the second inductive element is in parallel with the series association of the first capacitive element and the first inductive element.

According to one embodiment, the inductance value of the second inductive element is at least five times greater than the inductance value of the connection to ground.

According to one embodiment, the antenna further comprises a second capacitive element of adjustable capacity connecting the conductive strip to ground.

According to one embodiment, the distance between the respective connection points of the second capacitive element and the series connection of the first capacitive element and the second inductive element to the band is less than the distance between the connection point of the capacitive element and the capacitive element. second capacitive element and the connection to the ground.

According to one embodiment, the second capacitive element is in parallel with the series association of the first capacitive element and the second inductive element.

According to one embodiment, the inductance value of the first inductive element is at least five times greater than the inductance value of the ground connection.

According to one embodiment, the antenna constitutes a short-circuited quarter-wave antenna.

According to one embodiment, the antenna is sized for bandwidths in the range between about 700 MHz and 2.7 GHz.

According to one embodiment, the antenna is sized for bandwidths in the range between about 470 MHz and 3 GHz.

An embodiment also provides a portable telecommunication device comprising at least one antenna.

Brief description of the drawings

• la figure 1 un schéma-bloc d'un exemple de chaine 1 de transmission radiofréquence du type auquel s'appliquent les modes de réalisation qui vont être décrits ;
• les figures 2A et 2B sont des représentations schématiques d'antennes quart d'onde court-circuitées ;
• la figure 3 est une vue en coupe schématique d'un mode de réalisation d'une antenne PIFA ;
• la figure 4 est une vue en coupe schématique d'un autre mode de réalisation d'une antenne PIFA ; et
• La figure 5 représente une variante du mode de réalisation de la figure 4.

These and other features and advantages will be set forth in detail in the following description of particular embodiments in a non-limiting manner with reference to the accompanying drawings in which:

• the figure 1 a block diagram of an exemplary radio frequency transmission chain 1 of the type to which the embodiments to be described apply;
• the Figures 2A and 2B are schematic representations of quarter-wave antennas short-circuited;
• the figure 3 is a schematic sectional view of an embodiment of a PIFA antenna;
• the figure 4 is a schematic sectional view of another embodiment of a PIFA antenna; and
• The figure 5 represents a variant of the embodiment of the figure 4 .

detailed description

The same elements have been designated with the same references in the various figures.

For the sake of clarity, only the elements useful for understanding the embodiments that will be described have been shown and will be detailed. In particular, the operation and the structure of the whole of a radio frequency transmission chain have not been detailed, the described embodiments being compatible with the usual transmission chains. In the following description, when referring to the terms "approximately", "about" and "in the order of", this means to within 10%, preferably to within 5%.

The figure 1 a block diagram of an example of radio frequency transmission chain 1 of the type to which the embodiments to be described apply.

Such a chain is, in the applications targeted by this description, multifrequencies in transmission and reception. One or (most often) several antennas 2 are individually connected to a frequency tuning circuit 12 (TUNE).

In transmission, signals Tx to be transmitted are generated by electronic circuits 14 and are supplied by one or more power amplifiers (PA) to a switch network (SWITCH), whose role is to direct the signals towards a filter a network of filters 16 (FILTERS) as a function of the frequency band considered. The outputs (in transmission) of the filters are connected to another network of antenna switches 17 (SWITCH) responsible for selecting the output of the filter used and connecting it to the circuit 12 for adjusting an antenna 2.

In reception, the received signals Rx perform a similar but inverse path, from the circuit 12 of the antenna 2 picking up the signals in the appropriate frequency band, through the network of switches 17 to be filtered by one of the network filters 16 and then switched by the switch array 15 to a receive amplifier (generally a low noise amplifier - LNA) of the circuit 14.

The Figures 2A and 2B are schematic representations of quarter-wave antennas short-circuited, also called antennas F inverted (Inverted-F Antenna) which are particularly targeted by the described embodiments. Indeed, this type of antennas is the one generally used in mobile phones and tablets. More precisely, the antennas that are preferentially referred to are the PIFA antennas (Planar Inverted-F Antenna) which are formed from a conductive plane, often in the form of a conductive flat strip 22, which is plated on the internal face or which constitutes a portion of a peripheral region of a shell 4 of the phone. In the latter case, the conductive strip 22 is then isolated from the rest of the shell 4 by portions 42 of the latter, electrically insulating.

The Figures 2A and 2B illustrate an example of antenna 2 formed on a small side of the periphery of the shell 4 of a telephone. We suppose the case of a telephone of rectangular general shape. However, all that will be described applies more generally to any PIFA antenna whether or not it is worn by the periphery of the phone shell. These figures schematize sectional views of a telephone shell portion 4.

The Figure 2A illustrates the case of an antenna 2 whose length requires it to protrude from the short side. The antenna 2 therefore extends partially on the lateral edges of the shell 4.

The Figure 2B illustrates the case of an antenna 2 whose length is such that it is entirely contained in the short side of the periphery of the shell 4.

• une bande conductrice allongée 22 ;
• une prise d'antenne 24 (FEED) destinée à être connectée aux circuits du téléphone (en réception ou en émission), par exemple à un circuit 12 ou directement au réseau 17 de la figure 1 ; et
• une connexion 26 à la masse.

A PIFA antenna comprises at least:

• an elongate conductive strip 22;
• an antenna socket 24 (FEED) intended to be connected to the telephone circuits (in reception or transmission), for example to a circuit 12 or directly to the network 17 of the figure 1 ; and
• a connection 26 to the ground.

The socket 24 and the connection 26 are disposed in the same side of the strip 22, typically in an end quarter of the strip 22. The connection 26 is equivalent to an inductive element 23 (shown in dotted lines) of inductance L1 connecting the band 22 to the ground. According to the embodiments, this inductance L1 comes from the intrinsic inductance of the connection 26 or is that of a discrete inductive component.

In the antennas PIFA covered by this description, which are multiband antennas, the antenna 2 further comprises a capacitive element 28 of adjustable capacitance C connecting the band 22 to ground. The connection of the capacitive element 28 to the strip 22 is located in the other half of the length of the strip 22 relative to that receiving the plug 24 and the connection 26. The socket 24 can be on one side or the other of the connection 26 with respect to the element 28. The capacitive element 28 is controlled by the circuits 14 ( figure 1 ) depending on the desired operating frequency band or bands.

For an antenna, the bandwidth is defined as a Standing Wave Ratio (VSWR) of 3, which is equivalent to loss in reflection (Return Loss - RL) of -6dB. In other words, this corresponds to the frequency band in which at least 75% of the power is transmitted to the antenna.

The respective positions of the connection 26 and the capacitive element 28 as well as the respective values of the inductance L1 and of the capacitance C condition the resonance frequency of the antenna 2, which is otherwise fixed by the size of the band 22. In a simplified way, without capacitive element and with the connection 26 at the end of the band 22, the sum of the length and the width of a rectangular band 22 corresponds to a quarter (λ / 4) of the wavelength . The capacitive element 28 makes it possible to reduce the size of the strip 22. Still in a simplified manner, the position of the socket 24 with respect to the end of the strip 22 conditions the reflection coefficient of the antenna 2. In practice, the designer of the antenna 2 performs many simulations to determine the respective positions and values of the connections 24 and 26 and the element 28.

With the frequency bands used in mobile telephony, current antennas do not provide sufficient bandwidth to cover both the low and high frequencies of mobile telecommunication standards.

Typically, in order to cover the frequency bands of the 4G or even 5G standards, it is necessary to extend the operating frequency band of the antenna towards the high frequencies (from 2.17 GHz for 3G to 2.7 GHz for the 4G, then at 3 GHz or higher for 5G). This means that the current architectures of PIFA antennas are no longer suitable for going down sufficiently in frequency (for 4G, it is desired to have a bandwidth down to about 700 MHz and for 5G, to less than 500 MHz ).

In addition, it is now desired that the phones are able to capture or cover several frequency bands simultaneously (carrier aggregation) in order to increase the bandwidth and data communication rates. This is especially true for 4G and 5G standards.

The embodiments described below propose new antenna architectures aimed inter alia at improving the bandwidth with a given conductive strip size, imposed by the constraints of the shell 4 of the telephone or, more generally, by the space available for antenna 2.

The figure 3 is a schematic sectional view of an embodiment of a PIFA antenna.

In figure 3 , for example, an antenna 2 made with a strip 22 of the type of that of the Figure 2B . However, all that is described below also applies to an antenna whose band 22 extends partially around the longitudinal sides of the phone ( Figure 2A ).

In addition to the conductive strip 22, there is the socket 24, the connection 26 to the ground (direct or via an inductive component 23 illustrated in dotted lines) and the capacitive element 28. According to this embodiment, a inductive element 32 connects, near the capacitive element 28, the strip 22 to ground. By proximity, it is meant that the distance d32 between the respective connection points of the element 32 and the element 28 to the strip 22 is less than the distance d32 'between the connection point of the element 32 and the connection to the mass 26.

The inductive element 32 may be on one side or the other of the capacitive element 28.

Preferably, the elements 28 and 32 share the same point of connection to the band 22, that is to say that the distance d32 is zero and the elements 28 and 32 are in parallel.

The inductive element 32 adds an inductor L2 in parallel with the capacitive element 28. This inductance L2 makes it possible to improve the range of variation of the adjustable capacitive element 28, and makes it possible to widen the bandwidth towards the low frequencies, while facilitating the adjustment and choice of low frequencies. For a given low frequency limit, the smaller the distance d32, the lower the line length supplied by the band portion 22 between the connection points of the elements 28 and 32, and the lower the value of the inductance L2. to be high and better is the yield.

The value of the inductance L2 is greater than the value of the inductance L1 provided by the connection to ground. Preferably, the value of the inductance L2 is at least 5 times higher, preferably of the order of 10 times greater, than the value of the inductance L1.

For example, an antenna having a high frequency band (between about 1.7 and 2.7 GHz) and a low frequency band (between about 700 MHz and 1 GHz) is made, which is particularly suitable for mobile telephony. .

As a particular embodiment, in mobile phone applications, with a conductive strip 22 having a length of the order of 5 to 10 centimeters, the value of the inductance L2 is several tens of nanoHenry. The order of magnitude of the value of capacitance C of capacitive element 28 is picoFarad. Such an antenna can lower the low band to about 700 MHz or less.

The figure 4 is a schematic sectional view of another embodiment of a PIFA antenna.

In figure 4 , for example, an antenna 2 made with a strip 22 of the type of that of the Figure 2A . However, everything described below also applies to an antenna whose band 22 does not extend beyond one side of the phone ( Figure 2B ).

In addition to the conductive strip 22, there is the socket 24, the connection 26 to the ground (direct or via an inductive component 23 illustrated in dotted lines) and the capacitive element 28. According to this embodiment, a inductive element 34 is connected in series with the capacitive element 28. Thus, the strip 22 is connected to ground by a series association of an adjustable capacitive element 28 of capacitance C and an inductive element 34 of inductance L3 .

The inductive element 34 here again makes it possible to improve the range of variation of the adjustable capacitive element 28, and makes it possible to widen the bandwidth towards the low frequencies.

The value of the inductance L3 is greater than the value of the inductance L1. Preferably, the value of inductance L3 is at least 5 times higher, preferably of the order of 10 times greater than the value of the inductance L1.

The embodiments of the Figures 3 and 4 are combinable, that is to say that an antenna 2 having an inductive element 32 can be made in parallel with a series connection of an adjustable capacitive element 28 and an inductive element 34. In this case, the distance d32 ( figure 3 ) between the respective connection points of the inductive element 32 and the series connection of the capacitive element 28 and the inductive element 34, to the band 22, is less than the distance d32 'between the connection of the inductive element 32 and the connection to ground 26.

An advantage of such a combination is that the operating frequency range of the antenna is further improved. Typically, it is then possible to cover all the frequency bands and in particular also the frequencies of the 5G standard, that is to say in the range of 470 MHz to GHz. In particular, the three bands from approximately 470 MHz to approximately 960 MHz (approximately 490 MHz bandwidth) may be covered, from approximately 1.350 GHz to approximately 1.535 GHz (approximately 175 MHz bandwidth) and approximately 1.7 GHz at about 2.7 GHZ, or even about 3 GHz.

The figure 5 represents an alternative embodiment of the embodiment of the figure 4 , according to which a second capacitive element 36, of adjustable capacitance C ', is connected close to the series connection of the capacitive element 28 and of the inductive element 34. As for the embodiment of FIG. figure 3 , by proximity means that the distance d36 between the respective connection points of the element 36 and the series connection of the elements 28 and 34 to the strip 22 is less than the distance d36 'between the connection point of the element 36 and the connection 26 to ground.

As for the inductive element 32 ( figure 3 ), the capacitive element 36 can be on one side or the other of the capacitive element 28.

Preferably, the connection point is common, that is to say the distance d34 is zero and the element 36 is in parallel with the series association of the elements 28 and 34.

An advantage of the embodiment of the figure 5 is that keeping the other identical elements and, in particular without modifying the band 22, so the architecture of the shell 4 of the phone, we can move the central frequency, which allows to move the bandwidth to improve the frequency coverage.

An advantage of the embodiments which have been described is that they make it possible to improve the bandwidth of a PIFA antenna, in applications using the standards and frequency bands of the mobile telephony.

Another advantage is that the solutions described make it possible to produce antennas compatible with an operation in which all the frequency bands are simultaneously covered (carrier aggregation) with two antennas. Mobile phones usually have two antennas.

Another advantage of the embodiments that have been described is that they are compatible with current phone models. In particular, they do not require modification of the electronic circuits, or of the conductive strip 22 (hence of the shell 4) but only to add passive components (inductance (s) L2 and / or L3 and / or capacitance C ' ).

Various embodiments and variants have been described. Certain embodiments and variations may be combined and other variations and modifications will be apparent to those skilled in the art. Moreover, the control of the adjustable capacitive elements has not been detailed. This command comes from the electronic circuits of the device using the frequency-adjustable multiband antenna described, and is generated and determined in the same way as for conventional antennas. Finally, the practical implementation of the embodiments that have been described is within the abilities of those skilled in the art from the functional indications given above. In particular, the dimensioning of the inductive and capacitive depends on the electronic device incorporating the antenna PIFA and is within the reach of the skilled person.

Claims (17)

Antenna (2) comprising: an elongate conductive strip (22); an antenna socket (24); a connection (26) to ground; at least a first capacitive element (28) of adjustable capacity; and at least one first inductive element (32) connecting the conductive strip to ground. Antenna according to claim 1, wherein the distance (d32) between the respective connection points of the first inductive element (32) and the first capacitive element (28) to the band (22) is less than the distance (d32 ' ) between the connection point of the first inductive element (32) and the ground connection (26). Antenna according to claim 2, wherein the first inductive element (32) is in parallel with the first capacitive element (28). An antenna according to any one of claims 1 to 3, further comprising a second inductive element (34) in series with the first capacitive element (28). Antenna comprising: an elongate conductive strip (22); an antenna socket (24); a connection (26) to ground; at least a first capacitive element (28) of adjustable capacity; and at least one first inductive element (34) in series with the first capacitive element. An antenna according to claim 5, further comprising a second inductive element (32) connecting the conductive strip (22) to ground. Antenna according to claim 6, wherein the distance (d32) between the respective connection points of the second inductive element (32) and the series connection of the first capacitive element (28) and the first inductive element (34) to the band (22) is smaller than the distance (d32 ') between the connection point of the second inductive element (32) and the ground connection ( 26). Antenna according to claim 7, wherein the second inductive element (32) is in parallel with the series association of the first capacitive element (28) and the first inductive element (34). Antenna according to any one of claims 4, 6 to 8, wherein the inductance value (L3; L2) of the second inductive element (34; 32) is at least five times greater than the inductance value (L1) from the ground connection (26). Antenna according to any one of claims 1 to 9, further comprising a second capacitive element (36) of adjustable capacity connecting the conductive strip (22) to ground. Antenna according to claim 10, wherein the distance (d36) between the respective connection points of the second capacitive element (36) and the series connection of the first capacitive element (28) and the second inductive element (34) to the band (22) is smaller than the distance (d36 ') between the point of connection of the second capacitive element (36) and the ground connection (26). Antenna according to claim 11, wherein the second capacitive element (36) is in parallel with the series connection of the first capacitive element (28) and the second inductive element (34; 32). Antenna according to any one of claims 1 to 12, wherein the inductance value (L2; L3) of the first inductive element (32; 34) is at least five times greater than the inductance value (L1) of the ground connection (26). Antenna (2) according to any one of claims 1 to 13, constituting a short-circuited quarter-wave antenna. Antenna (2) according to any one of claims 1 to 14, sized for bandwidths in the range of about 700 MHz to 2.7 GHz. Antenna (2) according to any one of claims 1 to 15, sized to cover bandwidths in the range of about 470 MHz to 3 GHz. Portable telecommunication device comprising at least one antenna (2) according to any one of Claims 1 to 16.

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