EP1108616A2

EP1108616A2 - Planar microstrip antenna for motor-vehicle system

Info

Publication number: EP1108616A2
Application number: EP00125605A
Authority: EP
Inventors: Guido Biffi Gentili; Pietro Mantovani
Original assignee: Ask Industries SpA; Zendar SpA
Current assignee: Ask Industries SpA
Priority date: 1999-12-13
Filing date: 2000-11-22
Publication date: 2001-06-20
Also published as: IT248292Y1; ITRE990059U1; EP1108616A3

Abstract

A planar microstrip antenna suitable for motor-vehicle systems operating in dual-band resonance frequency. it comprises a radiant element (1), a mass plane (2) parallel to said radiant element (1), a shorting lead (3) that connects said radiant element to said mass plane, and feeding means fixed to a coaxial cable (8). Said radiant element (1) has a configuration proportioned for a first resonance frequency, and is provided with at least a slot (6) located in proximity with and parallel to its edge (5). Said slot has a proportional extension according to the resonance frequency desired.

Description

The present invention relates to a microstrip, suitable for use of motor-vehicles systems.
More particularly, the present invention relates to a planar microstrip antenna for motor-vehicle systems suitable for cellular telephony, and especially for systems operating in dual band resonance frequency, as well as for applications other than telephony.
The planar antenna of the present invention is preferably applied on the windows of motor-vehicles; more specifically on windscreens and/or rear windows. It is particularly configured to be used at prefixed frequencies, 800/900 MHz (GSM, ETACS, AMPS, PCD) adopted in Europe.
Planar microstrip antennas are known; they comprise:

a radiant element adhering to the glass of the windscreen or the rear window;
a mass plane parallel to said radiant element;
a mass shorting plane parallel to said radiant element;
a mass shorting element that connects said radiant element to said mass plane; and
feeding means comprising a capacitive coupling fixed to a coaxial cable; said capacitive coupling being applied 10 the mass plane and spaced from the radiant element of an extent that depends on the operating band of the antenna.

Such planar microstrip antennas may be installed on any type of motor vehicles, allow to operate within a bandwidth equal to or greater than 10%, with a uniform irradiation on the horizontal plane, a prevailingly vertical polarization of the electric. field, and field boundary emissions within the passengers' compartment, avoiding to overcome the electromagnetic field limits indicated by the norms in force.
Object of the present invention is to realize a planar antenna ensuing from the theories of the so-called patch-antennas, specifically suitable to operate at dual-band frequencies such as those of 900 MHz and 11800 MHz, usually adopted in the present European radio-telephone systems.
A further object of the present invention is to realize a planar antenna of the above type, having a low profile with contained dimensions, simple construction and low costs, and also easily installable in the inside of any type of vehicle.
In its more general aspects, the present invention allows to obtain these and other objects which will be obvious thanks to the following description of a microstrip planar antenna wherein the radiant element is so proportioned as to operated at a first prefixed resonance frequency, and the same element comprises, in close proximity and parallel to its radiating edge, at least a slot whose extension is proportioned as function of a second prefixed resonance frequency.
The behavior of such slot is that of a radiating edge, corresponding to said second resonance frequency.
Other resonance frequencies may be obtained by varying the length extension of said slot(s) or realizing the same with serially aligned couples of slots.
Slots are rectilinear, parallel, adjoining each other and the edge of the radiant element corresponding to the first of said frequencies and are closed at the ends.
The advantages achieved by the antenna of the present invention lie essentially in that the same, constituted to operate at defined frequencies, can irradiate uniformly across the horizontal plane with a prevailingly vertical polarization of the electric field, and allows an adequate containment of the radiation emitted in the inside of the compartments without exceeding the admitted limits of the electromagnetic field. Besides, the present invention can be installed, on a prior simple tuning, on all vehicles.
The constructive and functional characteristics of the microstrip planar antenna of the present invention will be better comprised thanks to the following description wherein reference is made to the attached drawings which represent some embodiments reported by way of non limiting example and wherein:
Figure 1 shows the schematic perspective view of an example of planar antenna of the present invention;
Figure 2 shows a schematic plan view of the antenna of Figure 1;
Figure 3 shows the schematic plan view of an embodiment of the antenna of the preceding figures; and
Figure 4 shows the prospective view from the bottom upwards of the planar antenna of the present invention having the mass plane obtained from a printed circuit board metallized on one side only, and the feeding connection realized with a microstrip.
The figures refer to a planar patch-antenna, in particular of the dual-band type, for use in motor-vehicle applications of "QWSCM" cellular telephony.
With special reference to the figures, the planar antenna of the present invention comprises a radiant element 1, a mass plane 2 parallel to said radiant element 1, and a shorting connector 3 which connects said radiant element 1 to said mass plane 2.
The antenna is fed by a cable 8 through a flat armor 9 capacitive coupling 7.
The distance of the lower armor 9 from the upper radiant element 1 may be adjusted to optimize the radiation and circuit characteristics of the antenna, in particular to optimize its bandwidth.
According to a first embodiment, cable 8 may be associated to a connector 10 whose position is adjustable for the maximum impedance adaptation, by sliding and tying along a slot 11 obtained on the mass plane 2.
According to a second embodiment, the mass plane 2 is preferably obtained from a printed circuit board, metallized on one only side 12, so as to allow the realization of the feeding line with one microstrip 13. In this way, the antenna has a structure simpler, easily realizable, symmetrical, with minimum overall dimensions and mechanically stronger, with minimum electromagnetic perturbations. Besides, the transition to the coaxial cable 8 with the side inlet, is made simpler. Microstrips or stubs 14, orthogonal, suitably positioned and adapted in the direction of the length of said feeding line may be also applied to the feeding line 13. The arrangement of such stubs allows to widen or to restrict, to elongate or to shorten said line, according to the specific requirement of impedance adaptation, and to insert a capacity between the radiating edge of the antenna and the mass plane.
For the reduction of the emissions in the inside of the passengers' compartments, the mass plane 2 may be extended through a connection with the windshield or the rear window realized with glassmetallized on one side only or treated with surface applications of transparent conductive films.
The adoption of a printed circuit board, metallized on one only side 12 allows to exploit the mass plane 2 also as a support for a GPS amplified antenna. The low-noise amplifying electronic circuit 15 of the GPS antenna and the related connections are applicable on the metallized layer 12 of the board, wherever it does not hamper the path of the microstrip feeding line 13, with or without orthogonal stubs 14, for instance, in one of the external angles of the mass plane. In order to exploit rationally the metallized surface 12 of the card without interfering between the components, the path of the feeding line from edge 17 to the base of the capacitive coupling 7 may also be inclined. Circuit 15 of the GPS antenna is connected and engaged with the corresponding "patch" ceramic tile 16, with superposed
a) the radiant element 1 is associated to a mass plane 2 of reduced dimensions through a continuous orthogonal lead 3 that constitutes the mass shorting element of the antenna;
b) the geometric configuration of the radiant element 1 depends on a first prefixed band of operating resonance frequency of the antenna;
c) on element 1, in a position close to its radiating edge 5, a slot 6 is obtained whose extension is a function of a second prefixed band of operating resonance frequency of the antenna;
d) the feeding of the antenna is through a capacitive coupling 7 which a coaxial cable 8 abuts to;
e) the glass of the rear window of vehicles constitutes the overlayer of the quarter-wave radiating element, and contributes to the determination of the radiation characteristics of the antenna, being the seat of surface waves;
f) in a preferred non-limiting embodiment, element 1 is so sized as to constitute a radiating edge 5, corresponding to the 900 MHz resonance frequency, and slot 6 created in a position close to said radiant edge 5 is so sized as to constitute a second radiating edge corresponding to the 1800 MHz resonance frequency.
Such characteristics cause the antenna of the present invention to be substantially universal for applications on any type of vehicles, and allow the same to operate with a uniform irradiation on the horizontal plane at a prevailingly vertical polarization of the electric field, with electromagnetic field emissions in the inside of the vehicles within the limits allowed.
While the present invention has been described and illustrated according to some embodiments reported by way of non limiting examples, many alternatives and variants will be obvious to those skilled in the art in the light of the above description.
Therefore, the present inventions intends to cover all the alternatives and variants that fall within the spirit and the protection scope of the following claims.

Claims

A microstrip planar antenna suitable for motor-vehicles comprising a radiant element (1); a mass plane (2) parallel to said radiant element (1); a shortening lead (3) connecting said radiant element (1) to said mass plane (2), and feeding means comprising a capacitive coupling (7) fixed to a coaxial cable (8),
characterized in that the radiant element (1) has a whole configuration proportioned for a first fixed working resonance frequency, and in that it is provided with at least a slot (6), located close and parallel to its edge (5), said slot (6) having an extension proportioned as a function of a second prefixed resonance frequency and constituting the radiant edge corresponding to this latter second frequency.
The microstrip planar antenna according to claim 1,
characterized in that slot (6) is rectilinear, parallel and close to edge (5) of the radiant element (1) corresponding to its first resonance frequency, and is closed at its ends.
The microstrip planar antenna according to claim 1 or 2,
characterized in that it is of the dual-band type.
The microstrip planar antenna according to claim 3,
characterized in that it has 900 MHz and 1800 MHz resonance frequencies.
The microstrip planar antenna according to any of the preceding claims, characterized in that the radiant element (1) is provided with further slots (18) always parallel to each other at reduced distances, and having more or less extended length developments depending on the resonance frequencies desired.
The microstrip planar antenna according to claim 5,
characterized in that the further slots (18) are individual or multiple and serially aligned.
The microstrip planar antenna according to any of the preceding claims, characterized in that the mass plane (2) of the antenna is constituted of a printed circuit board, metallized on one side only (12), whereon a microstrip feeding line (13) is applied.
The microstrip planar antenna according to claim 7,
characterized in that microstrips or stubs (14) are orthogonally arranged and positioned and adapted in the direction of the length of the microstrip feeding line (13), and in that their position depends on the widening or shortening of said line, according to the specific requirements of impedance adaptation, and the possible insertion of a capacity between the radiant edge (1) and the mass plane (2).
The microstrip planar antenna according to claim 7 or 8,
characterized in that said printed circuit board (12) constituting the mass plane (2) supports an amplified GPS antenna, wherein the connections and the low-sound amplifying electronic circuit (15) are applied to the metallized layer, while the corresponding ceramic patch tile (16) is positioned in superposed alignment on the non metallized upper surface of said board.
The microstrip planar antenna according to any of the preceding claims, characterized in that the coaxial cable (8) is associated to a connector (10) whose position is adjustable, for the maximum impedance adaptation, by sliding and tying along a slot (11) obtained on the mass plane (2).
The microstrip planar antenna according to any of the preceding claims, characterized in that the antenna feeding means comprise a flat armor (9) capacitive coupling and in that the distance of the lower armor (9) from the upper radiant element (1) can be adjusted in view of the optimization of the radiation and circuit characteristics of the antenna.
The microstrip planar antenna according to any of the preceding claims, characterized in that the mass plane (2) is connected to a windscreen or a rear window metallized or treated with the surface application of transparent conductive films.
Use of the microstrip planar antenna according to any of the preceding claims in "QWSCM" cellular telephony (GSM, ETACS, AMPS, PCD) of motor-vehicles.
A magnetic pump according to claim 1, wherein the magnetic coupling is realized by means of two magnets (41, 42) incorporated respectively in the wall of chamber (12) and the central part (28) of the impeller (25), said magnets (41, 42) being mutually aligned and arranged with heteronomous poles (North-South and vice-versa), so as to realize a closed magnetic circuit.
The magnetic pump according to claim 1 or 2, wherein chamber (12) is formed by a front body (11) and a back body (20), tight-united with each other, and wherein its internal surface is provided, in correspondence of the connection zone between bodies (11, 20), with a statoric element (40) wherein one (41) of the magnets for the linear magnetic coupling is incorporated.
The magnetic pump according to any of the preceding claims, wherein magnets (41, 42) have the shape of a toroidal ring.
The magnetic pump according to any of the preceding claims 1-3, wherein at least one of magnets (41, 42) has the shape of circle arcs (41', 41").
The magnetic pump according to any of the preceding claims 1-3, wherein at least one of magnets (41, 42) is articulated into sectors (41a, 41b, 41c, 41d, etc., and 42a, 42b, 42c, etc.).
The magnetic pump according to any of the preceding claims, wherein the thrust bearing bushes (18, 24) are of the magnetic repulsion type and comprise two magnets (43, 44), aligned with each other and arranged with the related poles (North-North and South-South), one (43) of which is incorporated in the thrust bearing bush and the other one (44) in the guide bush of the impeller.
The magnetic pump according to any of the preceding claims,
characterized in that it comprises a further magnetic repulsion thrust bearing bush comprising two magnets (43', 44') aligned with each other and arranged with the related poles (North-North and South-South), one (43') of which is incorporated in the wall of the front body (11) and the other one (44') in the operating front part of impeller (25).