DE10034547A1 - Broadband antenna has spiral coil set above reflector surface to provide a low profile antenna - Google Patents

Abstract

The broadband antenna has a spiral arm (2) that is parallel to a reflector (3) that has a dielectric layer (3b) and a metallic surface (3c). The separating distance (d) is set to suit the frequency range. The metal surface is organized as an array of elements.

Description

The present invention relates to an antenna according to the Preamble of the independent claim.

Antennas for the reception and radiation of electromagnetic Waves for the purposes of various radio services such as terrestrial and / or transmitted and / or received via satellite Broadcasting, mobile communications, navigation and the like can be found in increasing use. Varies depending on the application here the frequencies and it is currently, especially in Motor vehicle area, common for GPS systems, broadcasting temp catch, cellular in the different bands, if necessary TV and the like, attach separate antennas. The The reason for this is that for a given transmission or Reception performance the antenna still satisfactory Profit should have what so far with multi-band antennas cannot be achieved, for example, the broadband the frequency ranges for television reception, GSM 900, DAB, GPS, GSM 1800, DECT, UMTS, etc. should cover. individual antennas  can better adapt to a certain frequency range become.

Various approaches are already known, broadband users nen, d. H. frequency-independent antennas. So a spiral antenna was described by V. H. Rumsey in "Fre quency independent antennas ", IRE National Conv. Record, 5, Pages 114-118, 1957. The problem with these antennas is that that the electromagnetic radiation to both levels of Spiral is emitted symmetrically, but usually egg ne radiation in one direction is desired. To the Achieving the desired radiation characteristic becomes ty a metallic conductive surface as a reflector in one predetermined distance from the spiral. The distance is typically chosen so that the from the antenna on the Re electromagnetic radiation emitted by a reflector suitable phase runs back to the spiral antenna. To do this comparatively large distances between reflector and antenna arm, see T. E. Mayes, "Planar and other wi de-angle logarithmic spirals over ground ", in" Electromagne tics ", volume 14, pages 329-362, 1994. The distances chosen too small between reflector and antenna arm no or no significant radiation.

A broadband antenna structure is known from US Pat. No. 4,608,572 with a frequency-independent ground plane with little loss most known. It is suggested in it, near the mass level to arrange throttle elements with suitable dimensions. The ground plane has a conical shape.

US Pat. No. 5,313,216 describes a multi-octave band Microstrip antenna known to be a metal foil spiral dus antenna element and a dielectric substrate,  which posi between the antenna element and the ground plane is dated. The spiral mode antenna element has a fre sequence independent pattern, like a sine, log periodic, serrated or spiral pattern. The antenna ne can supposedly be flat on the surface of a body structure can be attached without the surface of the body having to penetrate the huge structure and can be adapted to it be, the antenna having a bandwidth of typically around 600%, that is to say spanning several octaves. To the US In the present patent is patented in particular with regard to the antenna reference arm forms.

Another flat spiral mode is known from US Pat. No. 5,508,710. Microstrip antenna known.

From the publication "Low-cost spiral antenna with dual Mode Radiation Pattern for Integrated Radio Services "by E. Gschwendtner and W. Wiesbeck, published during AP 2000 from 09.-14. April 2000 in Davos, Switzerland, it is known that spiral antennas can be used for automobiles. It will proposed there, the reflector distance, that is, the Ab stood between spiral arm and reflector level, through use suitable dielectric material. It will stated that it was not intended to use the spiral to realize a very obvious mass level because on this way in the required at the arm ends of the spiral Absorbers energy is lost too quickly. The usage of absorbers is disadvantageous especially when sending signals and undesirable.

Attention is also drawn to the article "Spiral Antenna with Frequency-Independent Coplanar Feed for Mobile Communi  cation Systems "by E. Gschwendtner, J. Parlebas, W. Wiesbeck in IEEE AP-S. 99, 11.-16. July, Orlando, Florida.

The aim of the present invention is to create a fla che antenna arrangement to implement a broadband Radiation enabled with a flat structure.

The independent claim 1 specifies the characteristics that lead to the Lö solution of the task are required. Preferred execution shapes can be found in the subclaims.

According to a preferred embodiment of the invention thus an antenna with a flat antenna arm arrangement and an associated reflector arrangement proposed, at wel It is provided that the reflector arrangement is close to the arm is brought and a dispersing, so frequency-dependent Has structure.

A basic idea of the invention is therefore to be seen in the fact that the reflector is a frequency-dependent, in particular resonant Has structure, that is, it is structured that it can be used for certain Fre sequences is resonant. An absorber is no longer used imperative. The resonance or dispersion leads to that the phase shift changes on reflection, whereby how the electromagnetic returning to the antenna arm Wave in this also has a changed phase. Structured reflector levels per se are known and described for example in the article by D. Sievenpie per, L. Zhang, R.F. Jimenez-Broas, N.G. Alexopoulus, E. Yablonovitch, "High-impedance electromagnetics-surfaces with a for hidden frequency band "," IEEE Trans. Microwave Theory and Techniques ", Volume 47, No. 11, Pages No. 2059-2074, Nov. 1999.  

The above article is incorporated by reference for reference purposes fully integrated.

The inventors have thus recognized that only by appro structured reflector planes emit radiation without Ab sorber losses are significant even with flat antenna formation can be improved.

The reflector arrangement can and will be preferred Embodiment attached so close to the antenna that the Distance at least one from the antenna properly frequency to be radiated not greater than lambda quarter, ins is special as a lambda sixth. It was found that a good profit can even be achieved at lambda / tenth leaves. This results in particularly low overall heights radiation caused by the reflector structure according to the invention is still good.

The antenna is preferably broadband and can at least over two, preferably more octaves of electromagnetic radiate and / or receive waves. This is in particular their preferred by realizing the antenna arms as spi Antenna arms have been reached. The spiral shape can be esp are particularly linear or exponential and there can be two or more spiral antenna arms are provided. On the in U.S. Pat. No. 5,313,216 disclosed antenna forms are referred to accepted.

The reflector arrangement is preferably at least essentially Chen arranged parallel to the spiral arms. The angle deflection chung between reflector arrangement and spiral arms can thus are typically below 15 ° of a 360 ° full circle. Prefers is the geometric oblique angle between the reflector and  Spiral arms less than 5 °, each one exactly level Reflector was accepted, but not necessarily the Case must be. In particular, it is possible to use the reflector and / or the spiral arms of a housing contour, for example to adapt to a body contour.

The resonance structure on the reflector is preferably chosen so that that a given frequency and / or a given fre frequency range of the radiated from the antenna arms received electromagnetic waves with a predetermined phase shift is reflected and thus with predetermined phase shift runs back on the arms. In a preferred embodiment is the phase shift at a predetermined frequency not larger than 15 ° (from 360 ° for the full circle) and is approximately 0 °. It however, it should be noted that this is not absolutely necessary is, but any phase positions can be set, to keep the variable, especially over the reflector surface are a further degree of freedom in the variation to obtain the directional characteristic.

It is preferred if a phase jump is not greater than 15 ° for those frequencies or frequency ranges or at least egg NEN part of which or which the reflect Gate arrangement closer than lambda quarter, preferably closer than Lambda sixth on the antenna or spiral arms lies. The reflector structuring is typically not for all frequencies with a very broadband antenna to be emitted, to be resonant. This is preferred for low frequencies, i.e. long wavelengths of lambda Case. Here would be a conventional, not structured Reflector lead to a significantly larger height and that Accordingly, the downsizing according to the invention is special  pronounced. At higher frequencies and thus smaller wel then the reflector structure is no longer right sonant, but the wavelength is also smaller and therefore the Distance between reflector and antenna arm related to the Wavelength larger, so that a green increased radiation behavior results.

The reflector structure can be made in a manner known per se will be realized. Frequency selectors are known in particular ve surfaces or photonic bandgap structures. A preferred variant is the use of so-called patch Arrays, i.e. a group of microstrip line arrays tennen, which can be particularly square. It is preferably a multi-layer reflector arrangement is provided, näm Lich first removed from the antennae Level is an electrically conductive, continuous thin layer over an insulating dielectric layer that also goes through and in turn a layer with electrically conductive capable surface elements. The lower, continuously conductive Layer is preferably on a self-adhesive carrier or the like attached.

The surface elements are preferably structured so that it resonance phenomena occur at certain frequencies, such as known in the art per se. It is possible to have multiple layers suitably structured conductive surfaces on top of each other assign and moreover in these locations the relative position to select the conductive surfaces to one another as desired len, as known per se in the prior art.

In a preferred embodiment, the reflector and the antenna arms with an electrically conductive ring surface che surround, the ring corresponds in particular to a height  according to the distance between antenna arms and reflector level having. This is how the reflector forms with the antenna arms or the level in which they are arranged, for example the plane in which the spiral arms lie, a cavity, which further increases the radiation behavior influenced. The cavity can be chosen depending on the shape of the antenna be and especially elliptical, square or before trains be cylindrical.

It should be mentioned that the antenna is preferred for the mobile Use, especially on motor vehicles, especially cars is suitable and determined.

In the following, the invention is only illustrated by way of example described the drawing. In this shows:

Figure 1 is a schematic view of an antenna according to the present invention with spiral arms and assigned reflector.

Figure 2 shows an antenna arrangement according to the present invention with an associated surrounding ring surface.

Fig. 3, 4 sketches for explaining the radiation characteristics.

Fig. 5a, 5b a structured reflector arrangement in top view and side view;

FIG. 6a, 6b multilayer patch arrays in side view;

Fig. 7a, 7b further structured reflector arrangements.

According to Fig. 1, generally designated 1 with transformants 1 comprises antenna array a plurality of antenna beams 2, which are generally planar and arranged at a distance d are of a struc tured reflector array 3.

The antenna arms 2 are formed as spiral antenna arms 2 a, 2 b, 2 c, 2 d and run in one plane. The dimensioning of the spiral arms is chosen so that the spiral antenna for receiving and emitting electromagnetic waves is arranged over several octaves. The feeding and decoupling of signals takes place in a manner known per se via a central connection (not shown).

The plane reflector 3 is arranged parallel to the plane of the spiral arms at a distance d. The distance d is selected such that it is smaller than lambda / sixth for one of the lower frequencies to be emitted by the spiral antenna arms. The reflector 3 consists of a base layer 3 a made of continuous, electrically conductive material on the side facing away from the spiral arms, a dielectric layer 3 b above and above this the spiral arms facing an array, that is to say a particularly regular arrangement of metal conductor surfaces 3 c. The size of the surface elements 3 c is selected such that the structures are resonant at one of the lower frequencies to be emitted by the spiral arms. The resonant frequency is by area size selection, distance between the surfaces to each other and strength and thickness of the dielectric material of the layer 3b to the desired frequency adjusted.

The operation of the antenna is illustrated in Fig. 3 and Fig. 4. The arrows show the currents at the spiral arms and the mirror currents given with the nearby reflector. In the case of a continuous, electrically conductive, ie metallic reflector, the reflection phase at the reflector is 180 °, so that the respective currents above and with the reflector are directed in opposite directions. This leads to a suppression of the radiation at a small distance, as is given in the present arrangement.

Due to the resonant structuring of the reflector according to the invention, however, there are no conditions as shown in FIG. 3, but rather conditions according to the invention as in FIG The in-phase nature of the two currents results in radiation as in a single-conductor system and not, as shown in FIG. 3, a radiation suppression as in a two-conductor system.

For frequencies other than resonant, the result is ent phases varying between 0 and 180 °, whereby by appropriate interpretation of the structures and through the about the wavelengths changing with the frequencies and the thus increasing distances between the wavelengths radiation arms and reflector still a good radiation results.

While the reflector arrangement of FIG. 1 is shown in FIGS . 5a, 5b, the surface structuring is not limited to quadratic patch arrays and other structures are possible, as shown in FIGS. 6 to 8. The dark areas in the figures represent metallically conductive areas. In the examples there is always a continuous, lower electrically conductive layer and one or more dielectric and conductive layers above it.

Fig. Shows that if a plurality of electroconducting higer fields and dielectric layers above one another, the electrically conductive surfaces in any arrangement zuein other according to the prior art can be disposed 6b.

In FIG. 2 it is shown that the reflector arrangement and the spiral antenna arms with an electrically conductive Ringflä surface 4 can be surrounded by the radiation by cavitation to improve further.

It should also be mentioned that the antenna arms are also available as Slots made in an electrically conductive surface could be.

Claims (21)

1. Antenna with a flat antenna arm arrangement and an associated reflector arrangement, characterized in that the reflector arrangement is attached close to the arm and has a dispersing, in particular resonant structure. 2. Antenna according to the preceding claim, characterized records that the reflector assembly at a distance of no greater than lambda / quarter of a radiation to be radiated Frequency is provided. 3. Antenna arrangement according to the preceding claim, there characterized in that the reflector arrangement in egg a distance of not greater than lambda / sixth one radiated frequency is provided.   4. Antenna according to one of the preceding claims, characterized characterized that the antenna for broadband radiation formed over at least two, preferably four octaves is. 5. Antenna according to the preceding claim, characterized records that the reflector is not at a distance greater than lambda / quarter, preferably not greater than Lambda / sixth, one, wavelength from a lower Distance octave band (lower frequency) from the antenna arms stands. 6. Antenna according to one of the preceding claims, characterized characterized in that the antenna arms in particular with linear or exponential spiral course venform are formed. 7. Antenna according to the preceding claim, characterized records that at least two spiral arms are provided are. 8. Antenna according to one of the preceding claims, characterized characterized in that the reflector arms at least in the we is arranged substantially parallel to the antenna arms. 9. Antenna according to one of the preceding claims, characterized characterized that the arms as slits in a lei tend surface are formed. 10. Antenna according to one of the preceding claims, characterized characterized in that the reflector arrangement for reflection that radiated and / or received by the antenna arms  predetermined radiation with a reflection phase predetermined Phase jump are formed. 11. Antenna according to the preceding claim, characterized records that the phase jump for a predetermined Frequency is not greater than 15 °, preferably around 0 °. 12. Antenna according to the preceding claim, characterized records that for a frequency with a phases jump is not reflected over 15 °, the reflector arrangement closer than lambda / quarter preferred as Lambda / sixth on the antenna arms, especially Spi alarms, is arranged. 13. Antenna according to one of the preceding claims, characterized characterized in that the reflector arrangement and / or the Antenna arm assembly is generally flat. 14. Antenna according to one of the preceding claims, characterized characterized that the resonance structure as a patch array with at least one lower conductive layer, one upper conductive layer and an intermediate dielectric layer is constructed. 15. Antenna arrangement according to the preceding claim, there characterized by that the lower conductive layer is electrically continuous. 16. Antenna according to one of claims 14 or 15, characterized ge indicates that there is more than one conductor / dielectric alternate layers.   17. Antenna according to one of claims 14, 15 or 16, characterized characterized that at least one of the lowest Layer different electrical conductive layer Structuring, especially regular patterns has. 18. Antenna according to the preceding claim, characterized ge indicates the regular pattern by Ellip sen, circles and / or polygons are formed. 19. Antenna according to one of the preceding claims, characterized characterized that the structure size to the desired Resonance frequency is tuned. 20. Antenna according to one of the preceding claims, characterized characterized in that the reflector / antenna arrangement of is surrounded by an electrically conductive wall, with which they form a cavity. 21. Antenna according to the preceding claim, characterized records that the cavity is elliptical, cuboid or is cylindrical.