Method and apparatus for lowering the vertical polar diagram of a transmitting and/or receiving antenna for mobile radio

(42) Date of commencement of the patent: 15.11.1998 (45) Date of issue: 26. 7.1999 (51) Int.CI.⁶ : H01Q 3/36

<td>(56) Documents:</td><td>(73) Patent owner:</td>

<td>US 45786B0A US 4555706A US 4516132A</td><td>FEEL JOSEF DIPL.ING. LIKE.</td>

<td>Y. YAMADA UH KIJIMA: LOW SIDELOBE AND TILTED BEAM</td><td>A-1040 VIENNA (AT).</td>

<td>BASE STATION ANTENNAS FOR SMALLER-CELL SYSTEMS ", IEEE</td><td>BONEK ERNST DIPL.ING. DR.</td>

<td>ANTENNAS AND PROPAGATION SOCIATY, APS INTERNATIONAL</td><td>A-1040 VIENNA (AT).</td>

<td>SYMPOSIUM 1989, VOL. 1, PP. 138-141</td><td>(72) Inventor: FEEL JOSEF DIPL.ING. LIKE. VIENNA (AT). BONEK ERNST DIPL.ING. DR. VIENNA (AT).</td>

AT 405 348 (54) METHOD AND DEVICE FOR REDUCING THE VERTICAL DIRECTION DIAGRAM OF A TRANSMITTER AND / OR RECEIVER ANTENNA FOR MOBILE RADIO (57) The apparatus for lowering the vertical directional pattern of a transmitting and / or receiving antenna consists of an antenna array (consisting in the embodiment of the elements 10, 11, 12, 13 and 14) have a circuit for shaping the directional characteristic, consisting of the phase shifters 20, 21 22 23 as well as 25, 26 27 26 and the service provider 30. The phase shifters 20,21,22,23 are used for basic adjustment of the desired directional diagram, while the phase shifters 25, 26, 27, 28 are provided for impressing phase shifts for lowering the directional diagram.

The lowering of the vertical directional diagram takes place both by tilting of the individual elements with respect to the group axis by an angle Oy equal to all elements (change in directional characteristic of the individual element) with unchanged position of the group axis and by changing the phase shift of the feed currents (change of the group characteristic).

This method combines the advantages of electrical (flexibility, preservation of the directional diagram characteristics) with those of mechanical lowering (frequency independence), but avoids their disadvantages.

This makes it possible to use even small antennas (few elements) or sparse large antennas in mobile communications.

OW 0078018

AT 405 348 Β

The invention relates to a method and a device for lowering the vertical directional diagram of a transmitting and / or receiving antenna for mobile communication, consisting of a phased array antenna provided with a circuit for shaping the directional characteristic.

Antennas are an essential element of the radio transmission link, especially in mobile communications. Current mobile communication systems, such as. B. from G. W. Lorenz in Comparison of Digital Mobile Radio Systems in Europe (GSM) and Japan (JDC) with Special Consideration of Economic Aspects, The Telecommunications Engineer, January / February 1993, pages 38-44, use base station antennas whose directional diagram is mechanical or mechanical and electrical or can be lowered purely electrically.

The idea underlying the subsidence results from β (θ, φ) = ί (θ, φ) · Ρ (θ, φ), (1) where G (δ, φ) is the directional characteristic (gain function) of the antenna group, ί (θ, Φ) is the directivity of the single element and Ρ (β, φ) is the group characteristic of the antenna array (this principle of diagram multiplication is described, for example, in RE Collin, Antennas and Radiowave Propagation, McGraw-Hill 1985, pages 107-109).

In the case of current antennas, only one of the multiplicative parameters, namely the group characteristic F (e, &lt;t&gt;), is used to change the directional characteristic (shift of the maximum). The reason for this is that the group characteristic exerts much greater influence on the directional pattern of the antenna group than the directional characteristic of the single element.

Optimizations of the directional diagram of group antennas, such as As the front-to-back ratio, can also be achieved by purely mechanical-constructive measures as in US Patent No. 4 516 132 (Bond, 5 pages).

In general, there are three methods for lowering the vertical directional diagram:

1) electrical lowering

2) mechanical pivoting of the overall arrangement

3) from 1) and 2) combined methods ad 1) When the vertical directional diagram is electrically lowered, the phases of the individual supply currents are changed so that the maximum of F (ö ^) comes to lie in a different spatial direction, which leads to a change in the Directional characteristic leads. The disadvantages of this method are mainly due to the following points:

a) Increasing widening of the main lobe when lowered and associated profit reduction.

b) occurrence of additional unwanted side lobes, grating lobes, due to the periodicity of

Move group characteristic in a shift of the same in the field of view of the antenna and thus

Power loss (reduction in profit) and additional interference for neighboring cells in digital mobile radio in the transmission mode or a reduced signal-to-noise ratio (SRV) and a reduced S / L (carrier to interference ratio, C / I (carrier-to-interference ratio)) in reception mode.

c) With increasing Absenkwinkel the normal side lobes of the directional diagram increase disproportionately, which also leads to interference for neighboring cells in the mobile and causes power loss.

d) frequency dependence of Absenkwinkels due to the frequency dependence of the phase shifts, which are optimal only for the operating frequency.

To minimize these disadvantages, it is necessary to use large array antennas with small distances between the elements of the group, as they are, for. By Yoshihide Yamada and Makoto Kijima in Low Sidelobe and Tilted Beam Base Station Antennas for Smaller-Cell Systems, IEEE Antennas and Propagation Society, AP-S (1989), p. 138-141 are described.

ad 2) With purely mechanical tilting of the overall arrangement, as is currently state of the art in sector antennas for mobile communications (see, for example, US Pat. B. the publications of the companies Kathrein, Dapa and Celwave), the reference plane for the group characteristic is changed, which leads in the same form as in the electrical lowering to a change in the phases of the supply currents to the original vertical reference plane and thus to lower the otherwise unchanged directional diagram. Since only the antenna axis is changed, the shape of the directional diagram is retained, only the radiation maximum looks in another spatial direction. This form of lowering is frequency-independent in contrast to the electrical lowering.

The disadvantages of mechanical lowering are essentially in

a) Change in cell size (horizontal broadening of the area coverage of the antenna) with increasing descent angle

AT 405 348 Β

b) Significant increase in radiation in neighboring cells (Störemission)

c) Low flexibility and difficult implementation of on-site lowering due to the mounting height of such antenna assemblies

d) Deteriorated wind load characteristics

(e) public impression that such antennas could fall - apparently because they were poorly mounted - ad 3) Combined methods consist in the application of both principles, whereby the electrical lowering generally can not be carried out on site, but already during the manufacture of the Antenna must be preset (see, for example, the publications of the companies Kathrein, Dapa and Celwave).

It is also known that mechanical and electrical properties of array antennas are generally related. In U.S. Patent No. 4,578,680 (Haupt, 12 pages), for example, stochastic mechanical manufacturing defects are electrically compensated.

The invention is based on the object to perform the lowering of the vertical directional diagram of an antenna group so that the advantages of the electrical (flexibility in lowering) and mechanical lowering (frequency independence) combined, the disadvantages are eliminated.

This is achieved in that the lowering of the vertical directional diagram both by tilting of the individual elements with respect to the group axis to an equal angle for all elements e_v (Change in the directional characteristic of the individual element) with unchanged position of the group axis takes place as well as by changing the phase shift of the feed currents (change of the group characteristic).

The proposed method is thus essentially based on a combination of two steps for lowering the directional diagram:

1) inclination of the individual elements (change of f (ö, &lt;») and thus elimination of the disadvantages of purely electrical lowering of the directional diagram.

2) Modification of the phase shift of the supply currents and, associated with this, a lowering of the vertical directional diagram (influencing F (e, j))).

It is not necessary that the individual elements are changed for each Absenkwinkel, but it can be determined for certain areas a certain angle of inclination of the individual elements to eliminate side lobes and Gräting praise. Preferably, this preset skew angle is equal to the upper limit of the desired lowering range.

By individual inclination of the individual elements also fine adjustments of a set directional diagram are also possible later.

The proposed method is suitable for any type of phased array antennas. As simulations have shown, this method is particularly advantageous for relatively small antennas (few elements), which can be used for mobile communication purposes for the first time due to this modification. By tilting the individual elements disturbing side lobes are eliminated and increases the gain in the main beam direction of such arrangements by up to 2 dB.

The invented method thus succeeds in significantly increasing the usable bandwidth.

This advantage is so important in mobile communication because it makes it possible to use one and the same antenna element for transmission and reception. According to the state of the art, this is not the case today (see, for example, the document by Kathrein on GSMAntennen).

A further significant improvement brings an application of this method on antennas with large profits, which can now be equipped with unchanged gains with a smaller number of individual elements, as Grating praise, which in lowering the vertical directional characteristic due to the large distances between the individual elements very quickly and occur massively, be eliminated by the tilting of the individual elements.

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

Figure 1, the basic arrangement

Figure 2 is a purely electrical lowering of the directional diagram

FIG. 3 shows the principle of the mechanical lowering of the directional diagram

FIG. 4 shows the characteristic shapes of the directional diagrams with mechanical lowering

Figure 5 is a schematic diagram of the novel method

Figure 6 is a comparison of the conventional method of electrical lowering and the invented method

Figure 7 is a comparison of the conventional method of mechanical lowering and the invented method

AT 405 348 Β

Generally applies to the illustrated directional diagrams:

-) The directional diagrams apply to a frequency of 900 MHz. The scaling to other frequencies is trivial and can easily be accomplished by the skilled person.

-) A displayed unit in the scaling corresponds to 10 dB.

-) The reference line (outermost circle) is 20 dB gain above the isotropic radiator.

1a shows a phased array antenna consisting of 5 elements (10, 11, 12, 13, 14), the phase shifters 20, 21, 22, 23 and 25, 26, 27, 28 and the power divider 30. The phase shifter 20, 21, 22, 23 are used for basic adjustment of the desired directional diagram, while the phase shifters 25, 26, 27, 28 are provided for impressing phase shifts for lowering the directional diagram.

FIG. 1b shows the corresponding directional diagrams. They show two sections through the directional characteristic of the arrangement, one recognizes in the vertical diagram the padded zeros between 90'SöS180 'and the suppressed side lobes between 0 £ θ £ 90 ·.

FIG. 2 shows a directional diagram, which has been lowered by 26 °, of the arrangement from FIG. 1, the difference of the phase shift of two individual elements (consecutive phase shift) being constant.

The diagrams show the much larger side lobes and the associated power loss as well as the unfavorable change in the shape of the main lobe compared to FIG. 1b.

FIG. 3 shows a schematic diagram of the mechanical lowering. It can be seen that the entire antenna structure 1 is rotated relative to the vertical axis by the desired lowering angle of the directional diagram θγ, whereby the reduction is achieved.

FIG. 4a shows the directional diagrams with mechanical lowering.

FIG. 4b shows, by means of the juxtaposition of the horizontal directional diagrams for electrical (10) and mechanical lowering (20), the great disadvantage of mechanical swiveling of the overall arrangement, which considerably broadens the horizontal directional diagram and thus

a) an altered cell size as well

b) cause increased interference emissions in neighboring cells.

FIG. 5 shows a schematic diagram of the invented method. It can be seen the inclination of the individual elements 10, 11, 12, 13, 14 relative to the group axis by the angle fl_v (Vorabsenkung), the further lowering of the directional diagram is carried out by konsekutive phase shift of the supply currents. One advantage is that the antenna can now be mounted substantially vertically. So it can be mounted much easier and much more stable on poles and buildings and does not give the impression that it could fall.

From Figure 6 can be seen the main advantage of Vorabsenkung over a purely electrically lowered radiation pattern (shown in phantom). It can be seen that the side lobes are suppressed by 10 dB in this example and the original shape of the directional diagram is restored.

Figure 7 shows the difference between purely mechanical lowering (7a) and the invented method (7b). It can be seen that with the same lowering angle, the cell broadening and thus the interference emissions in neighboring cells in the invented method could be substantially reduced compared to the values ​​for purely mechanical lowering.