EP1353406B1 - Antenna for mobile, in particular for a vehicle, with at least one circular and one linear polarisation, preferably vertical polarisation - Google Patents

Abstract

The device has a circular polarized antenna (3) above the linear polarized antenna(s) (33) on a counterweight surface (9). The circular polarized antenna can withstand high currents and the top antenna is fed from a feed point via a coaxial cable. An inner conductor-outer conductor inversion takes place at the feed point with the inner conductor of the feed (17,20) connected to the outer conductor of the coaxial cable (11) and vice-versa.

Description

The invention relates to a mobile antenna, in particular vehicle antenna for at least one circular and at least one linear, preferably vertical polarization according to the preamble of claim 1.

For the location of a mobile receiver, satellite-based systems, such as e.g. GPS, wider distribution.

Such GPS antennas usually consist of a circularly polarized antenna in the form of a patch radiator.

Such circularly polarized patch emitters require a large counterweight surface to ensure that the radiation pattern of the GPS emitter is properly formed. Too small a counterweight surface leads namely to the fact that the radiation pattern is bundled too much vertically in the usual vertical orientation, and thus especially the very low above the horizon satellites can no longer be received, whereby the evaluation errors are greater.

Vertically polarized antennas are commonly used in mobile communications. They serve for example for the transmission of calls according to the GSM standard, ie in the 900 MHz band and in the 1800 MHz band.

In many applications there is interest in a combi antenna using at least one circular antenna and at least one vertically polarized antenna, i. For example, a combination antenna with a GPS antenna for local positioning of a mobile subscriber and at least one vertically polarized antenna to handle this conversation over a mobile network. If, for example, two vertically polarized antennas are used, dual-band mobile phones could be used here, for example, which can be operated on the one hand and on the 1800 MHz band on the other, for example, on the 900 MHz band which is particularly common in Europe.

For the realization of these combination antenna systems different constructions are known.

According to a known construction are under a protective housing on a common base both the circularly polarized antenna (GPS antenna) and laterally offset a sharply shortened λ / 4 monopole antenna as a vertically polarized antenna (for example for the Mobile operation) arranged. The monopole antenna must therefore be greatly shortened, ie the height of the antenna relative to the base surface must be very low, as increasingly higher construction of this vertically polarized antenna, an increasingly strong mutual interference between the two antenna systems is observed, with a significant deterioration of the radiation pattern and significantly deteriorated results in the VSWR.

From GB 22 72 575 A a combination antenna consisting of a vertically polarized omnidirectional antenna and an overlying patch antenna is known, wherein the counterweight of the patch antenna is comparatively small and must be so as not to adversely affect the radiation pattern and the radiation properties of the vertically polarized antenna , However, the smaller the counterweight area becomes, the worse the radiation pattern and the radiation characteristic of the circularly polarized antenna becomes.

Therefore, according to EP 0 740 361 A1, it has also been proposed that the linearly polarized antenna be low, i. As a greatly shortened λ / 4 monopole to mount on a base, the height of the sharply shortened λ / 4 monopole should be so small that the counterweight surface carrying the circularly polarized antenna passes virtually infinitely into the ground plane lying to ground, in order to simulate a large counterweight area here.

But even with this construction is on the one hand as a disadvantage note that such vertically polarized antennas are very narrow band and with larger bandwidth the results on the VSWR significantly deteriorate. Because of the greatly reduced monopole of the linearly polarized antenna, the gain of the antenna is relatively low.

A combi antenna with an overhead circularly polarized patch antenna has also become known, for example, from EP 0 740 361 A1. The patch antenna provided above sits on a counterweight surface, which corresponds in size to the patch antenna. Below the patch antenna and the counterweight surface of the same size, a helix antenna extends over a comparatively long axial length, on the dielectric antenna body of which radiating elements are arranged helically running around. The cross section of the antenna body can be formed, for example, round, square, etc. In one of the embodiments, additional short radiator elements can also be provided, which likewise extend helically down over a partial length of the antenna body from the overhead base plate, wherein the connection of these additional radiator elements can be galvanic or by means of a capacitive coupling to the counterweight surface. However, this is a total of a different type of antenna with an additional GPS antenna to a helical antenna.

Finally, the known from the prior art combi antennas also continue to have the disadvantage that they are - especially if they are used on electrified routes in railway traffic - not high current safe, so no adequate protection against dangerous Touch voltages exists.

It follows from the above-mentioned descriptions that an optimization of the circularly polarized antenna leads to a further deterioration of the linearly polarized antenna and vice versa.

Regarding the achievement of a high current security, it is in principle from the prior publication Flachenecker, G .: "A lightning protected transistor-oriented receiving antenna" in NTZ, Volume 22, Issue 10, October 1969, pages 557-564 known to provide a corresponding grounding of the antenna system as such , A general grounding of an antenna system is in principle also known from EP 0 170 344 A2 as known. This is achieved basically by choosing a correspondingly large cross section, with which the inner conductor is grounded. However, this does not provide a solution for the case in which a circular antenna offset from a mass is fed via an inner conductor which is usually dimensioned in the usual way (that is, not heavily dimensioned). A solution to achieve a Hochstromtauglichkeit are not to be seen from this Vorveröffentlichungen.

A generic antenna, as it is used as a multi-purpose antenna, especially for submarines, has become generally known from US-A-4 030 100. This antenna comprises overhead a circularly polarized GPS antenna, which is arranged above the at least one linearly polarized antenna on a counterweight surface. This is above the at least one linearly polarized antenna arranged circularly polarized antenna thereby formed highly current-proof. This circularly polarized antenna is fed from a feed point via a coaxial line.

Object of the present invention is to provide over the prior art nevertheless improved combination antenna with favorable antenna characteristics, especially for vehicles such as electrified rail vehicles, comprising at least one circularly polarized antenna and at least one linear, in particular vertically polarized antenna.

The object is achieved according to the features specified in claim 1. Advantageous embodiments of the invention are specified in the subclaims.

It is also surprising in the context of the present invention that with simple means, for example, the above-described mobile combi antenna can be designed high-current safe.

The high current safety is possible by a massive grounding of all parts of the antenna including the inner conductor, without this leading to a deterioration of the antenna function. Due to the high current safety, the antenna is also suitable for electric locomotives, for example, as it fulfills the requirements for personal safety (for example, if the high-voltage overhead wire would fall down).

According to a preferred embodiment of the invention must also be noted as surprising that apart from the high current safety also has become possible to provide a linearly polarized antenna and install so that an optimal radiation pattern is given with respect to this linearly polarized antenna, and that equally with respect to the circularly polarized antenna. In other words, it has been possible to avoid that optimization of the radiation pattern of the one antenna type leads to a deterioration of the radiation pattern of the other antenna type.

This has become possible by a completely surprising not obvious solution.

Namely, the linear antenna radiator can be arranged and mounted in front of a base area or mass without being shortened, in order to ensure an optimum radiation pattern here. In a linear extension of the linearly polarized radiator, the circularly polarized antenna is generally located in a transverse orientation, preferably in the form of a patch radiator, which, however, is only mounted on a comparatively small residual counterweight surface.

Nevertheless, an optimal radiation pattern with respect to this circularly polarized antenna is possible, in particular also for the reception of many satellites in the vicinity of the horizon, for which purpose passive radiators or balancing elements are provided on the remaining counterweight surface.

These passive radiator or balancing elements or groups of several of these radiator or balancing elements are preferably arranged approximately crosswise to one another. However, the decision that matters is that these passive radiating or leveling elements projecting beyond the residual counterweight surface do not extend in the plane of the residual counterweight surface or the patch radiator itself, but strongly angled, the angling being preferably carried out in the direction of the vertical radiator underneath.

An angle of less than 60 ° to 50 ° is preferred for alignment of the underlying linear radiator. Favorable angle values are less than 30 °, even less than 25 '. Good values are in a range of 30 ° to 1 °.

These passive radiating or balancing elements can be designed differently, in the form of finger-shaped strips, electrically conductive gratings, beam-like or cylindrical elements, wire-shaped, hollow-body, etc. The width as the material thickness, the outer contour and shape can be varied as desired in many areas. It is also possible for several such passive radiating and adjusting elements to be grouped together, which are preferably offset by 90 ° relative to each other in plan view. In this case, these emitter or balancing elements, even if they are combined into groups, not each must be identically formed and provided.

In particular, it is also possible in a preferred embodiment of the invention by at least slight adjustments of the effective electrical length, thickness, shape, material choice, etc. of these passive radiator and balance elements and / or by different thickness selection, etc. to produce a slightly asymmetrical radiation pattern, which is so is agreed that with additionally attached protective housing caused by the protective housing or other local specificities caused asymmetries can be avoided or at least tend to be compensated.

Although so-called ground-plane antennas are known, which also have rods for improving the antenna characteristic. In such ground-plane antennas but only the mirror surface is important to get to a simplified antenna structure. However, the present invention does not relate to a λ / 2 radiator nor have the case of a ground-plane antenna known rods or wires a comparable with the present antenna device function. For an attachment of the rods known per se from a ground-plane antenna in the case of the present antenna type at the residual counterweight surface provided there would only lead to a non-functional antenna.

Another important difference between the inventively provided passive radiator or balancing elements to the rods of a ground-plane antenna is that the length of the rods in a ground-plane antenna ultimately can not serve to adjust the radiation pattern. However, completely different is the effect and operation in the present invention, since the angle adjustment and especially the change in length of the inventively provided passive radiator or balancing elements has a decisive influence on the radiation pattern. According to the invention, a fine adjustment in the sense of a targeted change of the radiation pattern can be made thereby.

Figur 1:

eine schematische vertikale Längsschnittdarstellung durch eine schematisch wiedergegebene Kombi-Mobil-Antenne;

Figur 2 :

eine Draufsicht auf die in Figur 1 gezeigte Antenne;

Figur 3 :

eine schematische Darstellung des Antennenaufbaus der vertikal polarisierten Antennen;

Figur 4:

ein Strahlungsdiagramm des GPS-Strahlers ohne die erfindungsgemäßen parasitären Strahlerelemente;

Figur 5 :

ein Strahlungsdiagramm bezüglich des Patch-Strahlers bei einer großdimensionierten Gegengewichtsfläche von 100 mm x 100 mm; und

Figur 6 :

ein Strahlungsdiagramm bezüglich des GPS-Strahlers unter Verwendung der erfindungsgemäß vorgesehenen parasitären Strahlerelemente.

The invention will be explained in more detail with reference to embodiments. Show in detail:

FIG. 1:

a schematic vertical longitudinal section through a schematically reproduced combined mobile antenna;

FIG. 2:

a plan view of the antenna shown in Figure 1;

FIG. 3:

a schematic representation of the antenna structure of the vertically polarized antennas;

FIG. 4:

a radiation diagram of the GPS radiator without the parasitic radiator elements according to the invention;

FIG. 5:

a radiation pattern with respect to the patch radiator with a large-sized counterweight area of 100 mm x 100 mm; and

FIG. 6:

a radiation pattern with respect to the GPS radiator using the inventively provided parasitic radiator elements.

In Figure 1, a mobile antenna, in particular vehicle antenna is shown in vertical cross-section, which is mounted on a lying on ground base plate 1. This base plate 1 can for example be mounted on the electrically conductive roof of a vehicle, on a roof section on an electric locomotive or on a wagon, etc.

As can be seen in the sectional view in Figure 1 and in the plan view of Figure 2, is on the top of the mobile multi-region antenna in the illustrated embodiment in horizontal position a circularly polarized antennas 3, i. a patch radiator 3 'is provided, which may consist of a ceramic plate 5, on the upper side, for example, the actual formed as a thin metal plate patch radiator 3' sits.

This circularly polarized antenna 3 sits on a in Top view square residual counterweight surface 9, which may, however, also have a different shape, and will be discussed later.

The patch emitter 3 'is fed by a coaxial line 11, which comprises an inner conductor 11' and a large-dimensioned outer conductor 11 "with a large material cross-section.

The inner conductor 11 'extends from the aforementioned patch radiator 3' through the entire mobile antenna assembly to the lower end of the coaxial line 11 and is there at a feeding point 20 with the base plate 1, i. connected to ground, conducting. A feed line 17 for feeding the circularly polarized antenna 3 comprises a feed inner conductor 17 'and a feed outer conductor 17 ", wherein the feed inner conductor 17' with the outer conductor 11" of the coaxial line is electrically connected.

The supply outer conductor 17 "is electrically connected to the base plate 1 and therefore to ground, namely at 21. As can be seen from the axial cross-sectional view of Figure 1, the feed outer conductor 17" but ultimately with the feed inner conductor 17th ', via an inner stub 27, which consists of a coaxial outer conductor 27', which is electrically connected at its opposite end to the base plate 1 via a radial or cup-shaped short circuit 27 "with the associated inner conductor 11" and thus shorted. The conductor 11 "thus has a double function. On its inside, it acts as an outer conductor for the Coaxial line 11 and on its outer side it acts as an inner conductor for the stub 27. The length, ie the height of this stub 27 corresponds to λ / 4 relative to the frequency to be transmitted, ie in the illustrated embodiment λ / 4 with respect to the GPS frequency band (1575 MHz band). The wall of the inner stub 27, ie of the coaxial outer conductor 27 'and of the ground or radial short circuit 27 "is made thick-walled in order to ensure the desired high-current safety.23 The coaxial outer conductor 27' is electrically conductively connected to the base plate 1.

In other words, therefore, the feed outer conductor 17 "with the coaxial inner conductor 11 'and the feed inner conductor 17' to the coaxial outer conductor 11" electrically connected, so that ultimately takes place at the feed point 20, a change of inner and outer conductors.

As can also be seen from FIG. 1, the coaxial outer conductor 11 "is continued over the cup-shaped short circuit 27" in the axial extension over the plane of the short circuit 27 "as far as the patch radiator 3 together with the inner conductor 11 'lying on the inner side.

In the embodiment shown in Figure 1 is also still a linear, that is provided in the embodiment shown vertically polarized antenna 33. The antenna 33 consists of a locking pot 30, the cylinder wall 33 'is arranged concentrically to the inner stub 27 and via a ring-shaped or ground-shaped short circuit 31 with the coaxial outer conductor 27' is in communication. In this case, the locking pot 30 ends opposite to its bottom-shaped short circuit 31 at a small distance 28th Before the base plate 1. As shown in Figure 3, the length of the locking pot is λ / 4 relative to the higher frequency to be transmitted, ie in the illustrated embodiment with respect to the PCN frequency band (1800 MHz band). The total height between the base plate 1 and patch radiator 3 and thus the entire axial length or height of the antenna 33 corresponds to λ / 2 of the higher frequency to be transmitted (in the illustrated embodiment, the frequency band 1800 MHz, ie the PCN frequency band), wherein the height of the antenna 33rd simultaneously λ / 4 of the lower frequency band to be transmitted, in the illustrated embodiment of the GSM frequency band (900 MHz band) corresponds. In the illustrated embodiment, while the cylinder wall 33 'of the locking pot 30 beyond the ring or bottom-shaped short circuit 31 extends to the remaining counterweight surface 9, with which it is electrically connected, the cylinder wall 33 thus formed' together with the cylinder wall 33 ' The antenna 33 thus acts as the λ / 2 radiator for the higher frequency to be transmitted and as the λ / 4 radiator for the lower frequency to be transmitted.

While the GPS antenna is fed via a first not shown in Figure 1 and indicated by reference numeral 37 coaxial terminal 37 (wherein the outgoing therefrom coaxial feed line 17 in the feed point 20 passes through a hole 22 in the base plate 1, ie at least from Inner conductor 17 'is penetrated while the outer conductor 17 "is electrically connected to the base plate 1 and ends here), the vertically polarized antenna for transmitting a lower and upper frequency band range (eg 900 MHz band, 1800 MHz band) via a second Coaxial connection 39 fed, its inner conductor 41 'is electrically contacted with the cylindrical antenna 33 and its outer conductor 41 "with the base plate 1. Instead of the connection 37 not shown in detail in Figure 1, a coaxial terminal 37 comparable to the coaxial terminal 39, for example, also directly on or in front of the feed point 20, so that a corresponding coaxial feed line 17 can be connected here, similar to the coaxial terminal 39. In this case, the coaxial terminal 37, ie its outer conductor or inner conductor, is correspondingly connected in the sense of the above-described change of inner conductor and outer conductor Also, instead of the coaxial terminal 39, a coaxial cable depart, which leads to a coaxial terminal 39 offset from FIG.

In order to improve the radiation pattern of the circularly polarized antenna 3, parasitic radiator elements 41 which are arranged crosswise are now also provided, which are also sometimes referred to below as balancing elements. These may consist of metal strips, metal mesh, bar-shaped constructions, etc., i. they may have different material thickness, material width, material shaping, straight edges, wavy cut edges, etc. The length, shape, material and resistance values as well as the thickness of the material can influence one another, so that a fine adaptation to a desired radiation pattern can be carried out as a result.

The aforementioned parasitic radiator elements 41 are in the axial sectional view according to Figure 1 but not in the plane of the residual counterweight surface 9 extending are arranged (which would significantly deteriorate the radiation pattern and the adaptation of the vertically polarized antenna), but are angled relative to the axial orientation 43 down towards the base plate 1, whereby an improved radiation characteristics on the one hand and a low overall height and overall width of the antenna construction to the other is realized.

A preferred angle α between the orientation of these parasitic radiating elements 41 in side view transversely to the axial orientation is preferably in a range of about 1 ° to 50 °, preferably in a range of 1 ° to 40 °, in particular 1 ° to 30 °. Favorable values are around 10 °.

The length of the parasitic radiator elements 41 shown in the drawings corresponds to approximately λ / 4 of the relative to the circularly polarized antenna 3 to be transmitted frequency band, in the present case the GPS frequency band. The length of the individual parasitic radiator elements 41 may differ slightly from each other, whereby a fine adjustment of the radiation pattern can be made, in particular a fine adjustment with respect to still aufzusetzenden protective housing for the antenna, thereby compensate for asymmetrical effects.

With such an antenna can be due to the non-shortened radiator with respect to the vertically polarized antenna 33 favorable results in terms of the radiation pattern and the radiation properties realize. Above all, however, such an antenna can be used simultaneously in a highly surprising manner realize optimal radiation pattern with respect to the circularly polarized antenna 3, which is explained in more detail with reference to Figures 4 to 6.

FIG. 4 shows a radiation diagram for a circularly polarized antenna 3 which does not have any of the parasitic radiator elements 41. It can be seen that the radiation pattern is severely limited.

With reference to the radiation pattern shown in FIG. 5, an antenna arrangement is shown in which a large-sized counterweight surface 9 of, for example, 100 mm × 100 mm was used. The radiation pattern is thereby somewhat improved. However, this would have further adverse effects on the radiation pattern and the VSWR of the vertically polarized antenna 33.

With reference to FIG. 6, the radiation pattern of the circularly polarized antenna 3 is reproduced using the parasitic radiating elements 41 explained with reference to FIGS. 1 and 2, which is significantly better by far than the diagrams according to FIGS. 3 and 4.

Instead of the described, crosswise arranged four parasitic radiator elements, for example, only two by 180 ° to each other staggered parasitic radiator elements may be provided, namely, for example, preferably in the one or perpendicular to another perpendicular direction, a radiation or a reception to be made. In the embodiment shown, however, a crosswise arrangement of the parasitic radiator elements is preferred.

Claims (18)

1. Mobile antenna, in particular a vehicle antenna, for at least one circular polarization and at least one linear polarization,

   - the circular-polarized antenna (3) is arranged above the at least one linear-polarized antenna (33) on a counterweight surface (9),

   - the circular-polarized antenna (3) which is arranged above at least one linear-polarized antenna (33) is designed to be able to withstand high currents, and

   - the antenna (3,'3') which is seated at the top is fed from a feed point (20, 17) via a coaxial line (11),

   characterized

   - in that, in this case, an inner conductor/outer conductor reversal takes place at the feed point in such a way that the inner conductor (17') of the feed (17) is connected to the outer conductor (11") of the coaxial line (11), and the outer conductor (17") of the feed (17) is connected to the inner conductor (11') of the coaxial line (11) and

   - in that, in this case, the inner conductor (17') is furthermore connected to the outer conductor (17") of the feed (17, 20) to one another, to be precise via an outer conductor (27') and an inner conductor (11''), which represents the outer conductor of the coaxial line (11), with the outer conductor (27) and the inner conductor (11' ') of the spur line (27) which is formed in this way being short-circuited opposite the feed point (17, 20) via a short circuit (27'') which is radial or in the form of a pot.
2. Mobile antenna according to Claim 1, characterized in that the inner conductor/outer conductor reversal takes place in the area of the feed (17, 20) in such a way that the inner conductor (11') of the coaxial line (11) and the outer conductor (17") of the feed (17, 20) are electrically connected to a base plate or base surface (1).
3. Mobile antenna according to Claim 1 or 2, characterized in that the short-circuited spur line (27) has a cylindrical outer conductor (27') and a short-circuiting section (27'') which is annular or in the form of a base and through which the coaxial outer conductor (11' ') of the coaxial line (11) passes.
4. Mobile antenna according to one of Claims 1 to 3, characterized in that the outer conductor (11'') of the coaxial line which leads to the antenna (3, 3'), the short-circuiting section (27") which is annular or in the form of a base, and the cylindrical outer conductor (27') of the short-circuited spur line (27) are provided with a large earthing cross section in order to be able to withstand high currents.
5. Mobile antenna according to one of Claims 1 to 4, characterized in that the circular-polarized antenna (3, 3') is fed via the feedline (17), and the antenna (33) which is linearly polarized, preferably vertically polarized, at least for one frequency band, or the antenna (33) which is linearly polarized, preferably vertically polarized, at least for two frequency bands are fed via a separate feed connection (39).
6. Mobile radio antenna according to one of Claims 1 to 5, characterized by the following further features:

   - the counterweight surface (9) has a base section (9') on which the circular-polarized antenna (3, 3') is arranged, and has additional antenna elements or tuning elements (41),

   - the parasitic antenna elements or tuning elements (41) are arranged offset in the circumferential direction corresponding to the radiation direction in a plan view of the mobile antenna, and at the same time project beyond the edge of the base section (9') of the counterweight surface (9), and

   - the parasitic antenna elements or tuning elements (41) are arranged in an angle range of 1° < α < 60° with respect to the longitudinal direction (43) of the antenna.
7. Mobile antenna according to one of Claims 1 to 6, characterized in that the angle α is 10° or more.
8. Mobile antenna according to Claims 1 to 7, characterized in that the angle α is less than 50°, preferably less than 40°, and in particular less than 30°.
9. Mobile antenna according to one of Claims 1 to 8, characterized in that the parasitic antenna elements or tuning elements (41) are in the form of metal strips, metal grids, line elements in the form of bars, and the like.
10. Mobile antenna according to one of Claims 1 to 9, characterized in that the parasitic antenna elements or tuning elements (41) have a length which is greater than their width.
11. Mobile antenna according to one of Claims 1 to 10, characterized in that the parasitic antenna elements or tuning elements (41) have straight or curved longitudinal edges.
12. Mobile antenna according to one of Claims 1 to 11, characterized in that the parasitic antenna elements or tuning elements (41) are composed of electrical material which is flat or is in the form of a hollow body.
13. Mobile antenna according to one of Claims 1 to 12, characterized in that individual parameters of the parasitic antenna elements or tuning elements (41) are chosen differently, for example to have slightly different lengths, widths, material thicknesses, shapes and the like.
14. Mobile antenna according to one of Claims 1 to 13, characterized in that the parasitic antenna elements or tuning elements (41) are offset through 90° with respect to one another in a plan view of the antenna, that is to say they are arranged in a cruciform shape with respect to one another.
15. Mobile antenna according to one of Claims 1 to 14, characterized in that two or more parasitic antenna elements or tuning elements (41) are in each case combined to form groups, and in that corresponding groups of parasitic antenna elements or tuning elements (41) are each offset through 90° with respect to one another in a plan view of the antenna, that is to say they are arranged in a cruciform shape with respect to one another.
16. Mobile antenna according to one of Claims 1 to 15, characterized in that the lengths of the parasitic antenna elements or tuning elements (41) are greater than the side length of the residual counterweight surface (9) which is not angled with respect to the parasitic antenna elements or tuning elements (41).
17. Mobile antenna according to one of Claims 1 to 16, characterized in that the antenna (33) which is linear-polarized at least for one frequency band, and preferably the antenna (33) which is linear-polarized at least for two frequency bands, and preferably transmits and receives via a common cylindrical arrangement (33', 33''), is arranged underneath the base section (9') of the counterweight surface (9).
18. Mobile antenna according to one of Claims 1 to 17, characterized in that, if the linear-polarized antenna (33) is designed for at least two frequency bands, the antenna (33) for the higher frequency band range is designed in the form of a wave trap (30) whose opening faces in the direction of the base plate or base surface (1).

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