CN1551410A - Multiband Planar Antenna - Google Patents

Abstract

A multi-band planar antenna comprising at least one radiating element, the radiating element consisting of a triangular or polygonal metal patch (1) having one or two coplanar protrusions (2) containing strips, printed on a substrate of thin dielectric material (3). The planar radiating element is preferably perpendicular to a ground plane (5-7) such as the roof of a vehicle. The lower vertex (8) of the metal patch (1) is the lead-in of the antenna and can be connected directly or with the aid of a matching network to the middle conductor of a coaxial feed line.

Description

Multiband Planar Antenna

technical field

The invention relates to a multi-band planar antenna. Various dual-band antennas are known for use in vehicles for cellular telephone service. Most of them are monopole or asymmetrical dipole wire or strip type mounted on the roof of the vehicle close to their front or rear edge. The radiating element of said antenna is usually protected by an aesthetically and aerodynamically functional housing of plastic material which can be of various shapes and configurations, even though the "dolphin fin" is the most commonly used one .

Background technique

Antenna positioning on top of the vehicle allows an isotropic diagram to be obtained in the horizontal plane when the presence of structural obstructions in the near sound field does not affect the radiation.

Printed monopole or dipole planar antennas with constant-width strip radiating arms (arms) have a common disadvantage of inherently limited impedance bands, therefore, the only way to obtain dual-band operation is to combine them with appropriate matching networks associated, but this results in further bandwidth reduction.

The most relevant consequence of these solutions is basically the difficulty of covering more services with the same antenna, and this situation is at odds with the needs of automakers who are increasingly demanding low-cost, capable A compact antenna that enables multiple services on different frequencies. A typical need is coverage for all cellular telephone services including the recent UMTS (Universal Mobile Telecommunications System) with one antenna.

Contents of the invention

It is an object of the present invention to realize at low cost a simple and compact multi-band planar antenna capable of covering current cellular telephone service while being mounted on the roof of a vehicle, or any sufficiently wide area such as the rear hood or doors of a vehicle. Optimal operation on metal surfaces.

Another object is to obtain "intrinsic" bandwidth operation by using a planar radiating structure conceptually derived from the "pressure" of a pseudo-conical radiating element loaded with a dielectric material and fitted with a ground-connected strip corresponding to a type present in a conical antenna loaded with dielectric material, suitable for operation in a vertical position on top of a vehicle, and in a Zendar Shown and described in European Patent No. 01121539.9 filed 10.09.2001 in the name of S.p.A (42020 Montecavolo, RE Italy) with the title "low profile, cord-less aerial".

Another object is to construct the radiating element such that a more commercial "swap" is integrated into the radiating element to receive GPS (Global Positioning System) satellite signals with associated amplification and filtering circuits.

Yet another object is to design antennas for intrinsic bandwidth operation capable of focusing two separate frequency bands by inserting matching networks, a first narrower band centered around 900 MHz and a second wider band centered On one frequency that covers both GSM (Global System for Mobile) and UMTS (around 1800MHz) cellular telephone services.

These objects according to the invention are achieved in the following manner:

a) using a thin plate of dielectric material as a support for a radiating element consisting of a triangular, or more generally polygonal, printed metal tab oriented in such a way that its lower apex forms the power supply point;

b) if further reduction of the radiating element is required, as an alternative to a single plate of dielectric material, multiple layers also including magnetic material are used;

c) Insert one or two coplanar strips with one end connected to the above-mentioned printed metal patch radiating element, and the other end connected directly or through a concentrated impedance;

d) In order to extend the coplanar band, a slit is introduced at the lower end of the band so that it can reach the dimensions required to obtain a good Impedance pattern;

e) Placing a plate of dielectric material at an orthogonal position with respect to the ground plane (e.g. the roof of a vehicle) so that the polygonal metal patch with its protruding part constituting the radiating element appears similar to operating in the presence of a metallic infinite reflector Radiation behavior of one of the typical vertically folded monopoles in the case of (metallic Infinite reflector);

f) Consider removing one of the coplanar stripline portions, thereby allowing additional tabs to be inserted perpendicular to the previous one to receive GPS signals;

g) consider the possibility of using two V-shaped placed tabs of dielectric material with a common feeding apex, in order to reduce the overall height dimension and to give the antenna maximum aerodynamic properties and a pleasing appearance;

h) optimization taking into account the shape, size, configuration and position of the planar radiating element relative to the ground plane to obtain a maximum bandwidth physically consistent with the overall dimensions of the antenna;

i) consider the possibility of using multiple layers of the windshield as support for the polygonal shape of the thin metal splices forming the radiating elements;

j) Consider inserting matching networks with centralized, distributed, or mixed constants to cover both old and new frequency bands for cellular telephone service.

The advantages obtained by means of the present invention are essentially that the antenna retains its predominant flatness and thinness characteristics on ground planes of limited size relative to wavelengths such as vehicle roof, hood, doors, rearview mirrors, windshields , and monopole electromagnetic behavior (electromagnetic behavior), at the same time, the antenna can adopt any flat or curved triangular, rectangular, trapezoidal or polygonal shape to meet manufacturing requirements and installation constraints.

Another advantage is that it is possible to configure the shape of the metal conductor sheet constituting the radiating element and the shape of the dielectric material plate on which the same patch is printed, allowing the patch to be integrated for use by using the same patch as the radiating element. ground plane to receive GPS satellite signals.

A further advantage is that the metallic conductor pieces constituting the radiating element can be embedded in multiple layers consisting of thin layers of dielectric and/or magnetic material.

Description of drawings

In the following, the invention is described in detail on the basis of embodiments given by way of non-limiting example with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a radiating element for a multi-band planar antenna in a basic embodiment according to the invention, the radiating element consisting of a symmetrical polygonal metal patch and two strips relative to a vertical axis placed symmetrically with respect to the connected ground;

2 is a perspective view of a radiating element for a multi-band planar antenna according to another embodiment of the present invention, the radiating element is formed of an asymmetric polygonal metal patch comprising a strip;

Figure 3 is a cross-sectional view of a plate of dielectric material making up a radiating element in a single layer embodiment;

Figure 4 is a cross-sectional view of a plate of dielectric material making up a radiating element in a dual layer embodiment;

Figure 5 shows the trend of the input reflection coefficient as a function of frequency for the antenna having the radiating element of Figure 1 without the matching network;

Figure 6 shows the trend of the input reflection coefficient as a function of frequency for the antenna having the radiating element of Figure 1, with the matching network included;

Figure 7 shows the radiation pattern trend in a horizontal section of the antenna with the radiating element of Figure 1 at a frequency of 900 MHz;

Figure 8 shows the radiation pattern trend in a horizontal section of the antenna with the radiating element of Figure 1 at a frequency of 1800 MHz;

Figure 9 is a perspective view of a radiating element for a multi-band planar antenna in a different embodiment according to the present invention, the radiating element comprising two plates of dielectric material placed in a V shape with a common feed apex and both ends of the strip ;

10 is a front view of a radiating element for a multi-band planar antenna in one embodiment according to the present invention, wherein the polygonal metal patch includes extending slots corresponding to the bands;

11 is a perspective view of an example of a radiating element for a multiband planar antenna associated with a patch for GPS reception according to the present invention;

12 is a perspective view of an example of association and connection between a radiating element for a multiband planar antenna and a circuit including a matching network according to the present invention, and

13 and 14 are perspective views of an embodiment example of a multi-band planar antenna according to the present invention, the multi-band planar antenna of a vehicle pre-configured for installation on the roof of the vehicle, and equipped with circuitry including a matching network and Plugs for GPS reception.

Detailed ways

With reference to the accompanying drawings, it can be noted that according to the invention in its basic embodiment, the multiband planar antenna is substantially constituted by a radiating element obtained by means of a triangular or polygonal thin metal conductor patch 1, which conductor patch 1 has one or two coplanar projections with a strip 2 connected to the ground.

Metallic contacts 1 are typically printed on a single substrate of thin dielectric material 3 by means of well-known selective etching techniques, which are commonly used in the production of printed circuits. Other suitable methods of obtaining metal tabs can also be used without departing from the scope of the invention, such as serigraphy using conductive paint.

In a second embodiment, a metal patch 1 with associated strip/strips 2 is obtained on a sheet of dielectric material 3 associated with a multilayer that also includes a thin layer of magnetic material 4; by means of this A solution that would allow for a significant reduction in the size of the multi-band planar antenna; this would allow the antenna to be mounted in a narrower area rather than on the roof of the vehicle, for example to mirrors, bumpers, doors, spoilers, etc. that would damage the antenna where the bandwidth is.

The upper end of the strip/strips 2 is connected to the metal patch radiating element 1 as described above, while the bottom end 8 is connected to the underlying ground plane 5 directly, or by means of a concentrated or distributed impedance . The strip/strips 2 allow the in-phase currents that form the low frequency radiation pattern to flow to ground.

Another patch 6 can be inserted in a suitable configuration in the shape of a metallic conductor patch constituting the radiating element 1, in the shape of a plate of dielectric material 3 on which the same patch is printed and one of the strips is removed (Fig. 11, 13, 15), the patch 6 is used to receive GPS satellite signals by using the same ground plane 5, which does not include very much the low frequency performance of the antenna.

The planar radiating element 1 is preferably positioned orthogonally with respect to a lower ground plane formed by a base 5 having the required dimensions compatible with the available space and which is in contact with, for example, the vehicle roof 7 below. connect.

The input electrical connection part of the antenna is formed by the connection between the lower apex 8 of the planar radiating element 1 and the middle conductor of the coaxial feeder whose grounded braid is connected to the ground. This connection can be obtained directly or through a circuit comprising a centralized, distributed, or mixed constant matching network 9 .

The substantially orthogonal positioning of the thin dielectric material plate 3 with respect to the base-ground plane 5 pre-arranges the metal tabs constituting the radiating element 1 with the strip 2 so as to exhibit similar operation in the presence of a metallic infinite reflector Radiation behavior of one of the typical folded monopoles below.

The possible insertion of the slit 10 allows the strip 2 to be extended (Fig. 10, 13) so that it can reach the required dimensions in order to obtain a good impedance pattern at the lower end of the strip (below 900 MHz).

In another embodiment, two plates 3 of dielectric material are used instead of 1; these plates are placed in a V shape and the lower feeding vertices 8 of the metal tabs constituting the radiating element 1 are common and the lower ends of the strips are Jointly or individually connected to the ground (Fig. 9); this layout allows reducing the overall height dimension and obtaining the maximum possibility of its external covering aerodynamic configuration.

In yet another embodiment, multiple layers that make up the windshield, rear window, or any other housing, or plastic support for accessories such as rear view mirrors, spoilers, bumpers, and the like can be used as the supporting polygon The thin metal patch that constitutes the radiating element 1.

Dielectric material supporting the radiating element 1 with respect to the ground plane 5-7 The configuration and layout of the plate/plates, as well as the optimization of shape and size allow to obtain the maximum bandwidth consistent with the overall available size for the antenna application .

In short, even though the antenna retains its predominant flatness characteristics and electromagnetic behavior typical of a monopole antenna at ground level, and has a constrained size, preferably large, however, relative to, for example, the roof of a vehicle, hoods, doors and windshields, it may also have any arbitrary planar curved triangular, rectangular, trapezoidal shape to fit it, while from an aerodynamic point of view, requirements and installations are constrained to any position and/or or on any type of vehicle. Apart from the shape of the patch constituting the radiating element 1 and the thin plate of dielectric material 3 supporting it, the radiation behavior of this antenna is similar to one of the monopole antennas operating on the same ground plane.

A circuit with a matching network 9 with centralized, distributed or mixed constant integration (associated with the antenna's input electrical connections) is used to optimize performance over two independent frequency bands; the first narrower band is centered at 900MHz around, while a second wider band is centered around frequencies that cover both GSM and UMTS cellular phone service (between 1700 and 2200MHz). A comparison between Figures 5 and 6 shows the trend of the input reflection coefficient as a function of frequency for an antenna of the type shown in Figure 1 with and without a matching network, it can be noted that the matching network functions to Values are centered on the two minimum values on the graph.

Having described and illustrated the invention by way of embodiments of the invention given by way of non-limiting examples only, various modifications in shape, detail, orientation, assembly and fit may be made without departing from its scope and scope, This is obvious to those of ordinary skill in the art.

Claims (14)

1. A multi-band planar antenna, characterized in that: it comprises at least one planar radiation element, which is made up of a metal patch (1) with a triangular or any polygonal shape, said patch being flat or is in the shape of one or two coplanar raised portions containing strips (2) printed on a substrate of thin dielectric material (3), said at least one planar radiating element being substantially Orientation orthogonal to the ground plane of space-compatible dimensions; the lower apex (8) of the metal patch (1) is used as the input electrical connection for the antenna, which is insulated from ground, and the strip/strips (2 ) is connected to the above-mentioned metal patch radiating element (1), while the lower end is connected to the above-mentioned underlying ground plane (5-7). 2. The multi-band planar antenna according to claim 1, characterized in that it consists of at least one radiating element made of a metal patch (1) of triangular or any polygonal shape, which is printed on a thin Dielectric material (3) on the substrate. 3. Multiband planar antenna according to claims 1 and 2, characterized in that it consists of at least one radiating element made of a metal patch (1) of triangular or any polygonal shape, which is printed On a substrate with a thin dielectric material (3) containing two coplanar raised portions of the strip (2). 4. Multiband planar antenna according to claims 1 and 2, characterized in that it consists of a radiating element consisting of triangular or any polygonal shaped metal patch (1) printed on a On a substrate of thin dielectric material (3) containing a coplanar raised portion of strip (2). 5. Multiband planar antenna according to claims 1 and 2, characterized in that it consists of a radiating element made of a metal patch (1) of triangular or any polygonal shape, which is printed on On a substrate having a thin dielectric material (3) comprising a coplanar raised portion of the strip (2), wherein identical tabs include extending slots (10) of the same strip. 6. According to claim 1, 2, the multi-band planar antenna of 4 and 5, it is characterized in that: it is made of radiating element, and this radiating element is made by the metal patch (1) of triangular or any polygonal shape, and its is printed on a substrate having a thin dielectric material (3) with a coplanar raised portion of the strip (2), and the metal tab (1) is associated with a tab (6) perpendicular to it , for receiving GPS signals. 7. The multi-band planar antenna according to any one of the preceding claims, characterized in that it consists of a triangular or any polygonal shape and has one or two coplanar protrusions containing one or more bands (2) A radiating element or elements constituted by the insert (1) is printed on any one of the external or internal interfaces of the multilayer which also includes one or more thin layers of magnetic material (4). 8. The multi-band planar antenna according to any one of the preceding claims, characterized in that one end of the protruding part containing the band (2) is connected to the metal patch (1), while the other end is directly connected to the ground ( 5-7). 9. The multi-band planar antenna according to any one of the preceding claims, characterized in that one end of the protruding portion/parts containing the strip (2) is connected to the metal patch (1) and the other end is passed through A centralized or distributed impedance is connected directly to ground (5-7). 10. The multi-band planar antenna according to any one of the preceding claims, characterized in that the planar radiating element (1) is substantially orthogonally bonded and placed on a ground metal base (5) having required dimensions and attached to the roof (7) of the underlying vehicle, or to a corresponding complementary surface of the same vehicle. 11. Multiband planar antenna according to claims 1-9, characterized in that it comprises two plates 3 of dielectric material placed in a V shape and constituting the lower apex of the power supply of the metal tabs of the associated radiating elements (1) (8) are common, and the lower ends of the bands (2) are united or individually connected to the ground. 12. According to the multi-band planar antenna according to any one of the preceding claims, it is characterized in that: the input electrical connection of the antenna is by the middle of the lower apex (8) of metal patch (1) and the coaxial feeder line that has ground braiding layer Constructed by direct connection of wires. 13. according to the multi-band planar antenna of claim 1-11, it is characterized in that: the input electrical connection of antenna is to be by the middle of the coaxial feeder wire that has ground braiding layer by the lower apex (8) of metal patch (1) The wires are formed by the connection of a circuit comprising a matching network with centralized or distributed constants (9). 14. The multi-band planar antenna according to any one of the preceding claims, characterized in that: the support of the polygonal thin metal patch that constitutes the radiating element (1) can be multi-layered, and the multi-layers are formed on the windshield or the rear window , or any housing or accessory supported by plastic such as mirrors, spoilers, bumpers.

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