METHOD FOR DETERMINING A RECEPTION DIRECTION OF A RADIO SIGNAL

Abstract

A method for determining a reception direction of a radio signal, wherein several antennas having different directional characteristics are used.

Claims

1. A method for determining a reception direction of a radio signal, comprising: receiving the radio signal by a first antenna having a first reception characteristic, and simultaneously generating a first reception signal, receiving the radio signal by a second antenna having a second reception characteristic, and simultaneously generating a second reception signal, wherein the second reception characteristic is different from the first reception characteristic, and identifying the reception direction based on the first reception signal and the second reception signal, wherein the reception direction is further identified based on a position information contained in the radio signal.

2. The method according to claim 1, wherein the first antenna has an omnidirectional characteristic as a reception characteristic.

3. The method according to claim 1, wherein the second antenna has a directional characteristic as a reception characteristic.

4. The method according to claim 1, wherein the reception direction is identified based on respective powers of the first reception signal and the second reception signal.

5. The method according to claim 1, wherein the reception direction is identified with an uncertainty regarding a limited number of transformations, in particular reflections and/or rotations.

6. The method according to claim 1, further comprising: receiving the radio signal by a third antenna having a third reception characteristic, and simultaneously generating a third reception signal, wherein the reception direction is also identified based on the third reception signal.

7. The method according to claim 6, wherein the third reception characteristic corresponds to the second reception characteristic, rotated about a vertical axis.

8. The method according to claim 6, further including the step of receiving the radio signal by a fourth antenna having a fourth reception characteristic, and simultaneously generating a fourth reception signal, wherein the reception direction is also identified based on the fourth reception signal.

9. The method according to claim 8, wherein the fourth reception characteristic corresponds to the second reception characteristic, rotated about a vertical axis.

10. The method according to claim 6, wherein the reception direction is identified unambiguously and/or without uncertainty.

11. The method according to claim 1, wherein the reception characteristics are implemented as a formula and/or numerically in each case.

12. The method according to claim 1, wherein a distance of a source emitting the radio signal is further identified based on a power of at least one of the reception signals, in particular the first reception signal.

13. The method according to claim 1, wherein the method is carried out using at least a first radio signal and a second radio signal, and wherein a change in a distance of a source emitting the radio signals is identified based on associated reception signals, in particular first reception signals, in particular based on a free-space path loss.

14. (canceled)

15. The method according to claim 1, wherein the antennas are arranged vertically on top of each other.

16. The method according to claim 7, further comprising: receiving the radio signal by a fourth antenna having a fourth reception characteristic, and simultaneously generating a fourth reception signal, wherein the reception direction is also identified based on the fourth reception signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Further features and advantages will be apparent to those skilled in the art from the exemplary embodiment described below with reference to the accompanying drawing, in which:

[0048] FIG. 1 shows reception characteristics of an omnidirectional antenna and a directional antenna,

[0049] FIG. 2 shows reception characteristics of an omnidirectional antenna and four directional antennas,

[0050] FIG. 3 shows reception characteristics of an omnidirectional antenna and an alternative directional antenna,

[0051] FIG. 4 shows reception characteristics of an omnidirectional antenna and three directional antennas,

[0052] FIG. 5 shows an arrangement in which the method according to an aspect of the invention can be carried out.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] FIG. 1 shows directional characteristics of an omnidirectional antenna and a directional antenna. It can be clearly seen that the omnidirectional antenna has a uniform reception characteristic towards all sides. In contrast, the directional antenna has a reception characteristic which includes three bulges. The difference between the two reception characteristics can be used to determine the reception direction of a signal, although this reception direction may still include an uncertainty.

[0054] FIG. 2 shows an arrangement with a total of four directional antennas and one omnidirectional antenna, where again the respective reception characteristics are shown. The directional antennas each have the same reception characteristic as the directional antenna illustrated in FIG. 1. As the reception characteristics of the directional antennas overlap, it is possible to determine the reception direction of a radio signal without uncertainty and with very high accuracy.

[0055] FIG. 3 shows reception characteristics of an omnidirectional antenna and a directional antenna which is designed differently from those the reception characteristics of which are illustrated in FIGS. 1 and 2. The reception characteristic shown in FIG. 3, which is labeled directional antenna 1 in the figure, is not a reception characteristic having three bulges but with a one-sided continuous configuration of the reception characteristic.

[0056] FIG. 4 shows reception characteristics of an omnidirectional antenna and three directional antennas, which are labeled directional antenna 1, directional antenna 2 and directional antenna 3, wherein the reception characteristics of the directional antennas are identical to that illustrated in FIG. 4. These antennas also allow for precise determination of a reception direction of a radio signal without uncertainty or ambiguity.

[0057] FIG. 5 schematically shows an arrangement for carrying out an exemplary embodiment of the method according to an aspect of the invention. A vehicle 10 is illustrated only schematically, including a total of four antennas, specifically a first antenna 21, a second antenna 22, a third antenna 23 and a fourth antenna 24.

[0058] Said first antenna 21 is designed as a vertical dipole, so that it has an omnidirectional characteristic as a reception characteristic in the horizontal plane. In contrast, the second, third and fourth antennas 22, 23, 24 are designed as horizontal dipoles which are rotated by 120 to each other, so that they have reception characteristics similar to those shown in FIG. 4. This arrangement generally allows for precise determination of a reception direction of a radio signal.

[0059] FIG. 5 further schematically illustrates a transmitter 30, which may for example be a mobile phone. The transmitter 30 emits a radio signal 40 which is received by the antennas 21, 22, 23, 24 of the vehicle 10. As the radio signal 40 is received by the total of four antennas 21, 22, 23, 24 with different signal strengths and the directional characteristics of the four antennas 21, 22, 23, 24 are known, it is possible to calculate the reception direction of the radio signal 40. This is explained below by way of example.

[0060] Below, an exemplary calculation with a directional antenna and an omnidirectional antenna to identify the reception direction is given, which is based on the arrangement shown in FIG. 5 and the diagram of reception characteristics shown in FIG. 4.

[0061] A reception power of the omnidirectional antenna is assumed to be P.sub.Ru=50 dBm and a reception power of the directional antenna is assumed to be P.sub.Rl=55 dBm.

[0062] The following formula is assumed as the directional characteristic of the omnidirectional antenna:

D.sub.Ru()=0 dB.

[0063] The following formula is assumed as the directional characteristic of the directional antennas:

D.sub.Rl()=10 log 10(cos().sup.2).

[0064] The directional characteristic of such a directional antenna approximately corresponds to that of a patch antenna. The assumed directional characteristic of the omnidirectional antenna approximately corresponds to the directional characteristic of a dipole or monopole.

[0065] Now the difference between the two reception powers, which is P.sub.RuP.sub.Ri=5 dB, is to be expressed in terms of the directional characteristic. Therefore the following holds true:

P.sub.RuP.sub.Rl=D.sub.Ru()D.sub.Ri()=5 dB,

[0066] which, if D.sub.Ru()=0 dB,

[0067] leads to

[00001]$10.Math.\frac{-\left(P_{\mathrm{Ru}}-P_{\mathrm{Ri}}\right)}{10}={\cos \left(\right)}^2$

[0068] P.sub.RuP.sub.Rl=10 log 10(cos().sup.2). With the aid of the calculation rule

[00002]$\cos .Math..Math.x^2=\frac{1}{2}.Math.\left(1+\cos .Math..Math.2.Math.x\right),$

the right term can be resolved. The result is:

[00003]$10.Math.\frac{-\left(P_{\mathrm{Ru}}-P_{\mathrm{Ri}}\right)}{10}=\frac{1}{2}.Math.\left(1+\cos .Math..Math.2.Math.\right),$

[0069] whereafter the cos term

[00004]$2.Math.10.Math.\frac{-\left(P_{\mathrm{Ru}}-P_{\mathrm{Ri}}\right)}{10}-1=\cos .Math..Math.2.Math.$

[0070] can be isolated. Subsequently, the equation can be resolved to give , that is the angle, by means of the arc cosine.

[0071] After the equation is resolved to give , the result is:

[00005]$=\frac{1}{2}.Math.{\cos }^{-1}\left(2.Math.{10}^{\frac{-5.Math..Math.\mathrm{dB}}{10}}-1\right)$

[0072] This means, an angle of =55.78 is calculated for a reception power of 5 dB.

[0073] It is to be understood that, if only one directional antenna is used as has been done in the exemplary calculation just made, there is still an uncertainty regarding the reception direction, i.e. the radio signal 40 may come from the left or right relative to a central axis of the directional antenna and this would not be distinguishable. This uncertainty can be resolved by making corresponding calculations using the other antennas, so that the reception direction can be determined without ambiguity.

[0074] The aforementioned steps of the method according to an aspect of the invention can be carried out in the given order. However, they can also be carried out in a different order. In one of its embodiments, for example including a particular combination of steps, the method according to an aspect of the invention can be carried out in such a manner that no further steps are carried out. However, in principle further steps can be carried out, even steps which are not mentioned.

[0075] In general it should be noted that vehicle-to-X communication means in particular direct communication between vehicles and/or between vehicles and infrastructure facilities. It can therefore be vehicle-to-vehicle communication or vehicle-to-infrastructure communication, for example. If throughout this application reference is made to communication between vehicles, this can in principle be realized for example as vehicle-to-vehicle communication, which typically takes place without transfer via a mobile phone network or a similar external infrastructure and which should therefore be distinguished from other solutions, which are for example based on a mobile phone network. Vehicle-to-X communication can take place using the IEEE 802.11p or IEEE 1609.4 standards, for example. Vehicle-to-X communication can also be referred to as C2X communication. The subfields can be referred to as C2C (Car-to-Car) or C2I (Car-to-Infrastructure). However, an aspect of the invention does explicitly not exclude vehicle-to-X communication with transfer, for example via a mobile phone network.

[0076] The claims belonging to the application are not a waiver to achieve broader protection. If it turns out during the procedure that a feature or a group of features is not absolutely necessary, it is already now the applicant's intention to formulate at least an independent claim which does no longer include the feature or the group of features. This may be for example a sub-combination of a claim existing on the filing date or a sub-combination of a claim existing on the filing date, which is limited by further features. Such reformulated claims or combinations of features should be understood as covered by the disclosure of this application.

[0077] It should further be noted that configurations, features and variants of aspects of the invention which are described in the different embodiments or exemplary embodiments and/or shown in the figures can be arbitrarily combined with each other. Individual or several features can be arbitrarily exchanged with each other. Any resulting combinations of features should be understood as covered by the disclosure of this application.

[0078] References back to dependent claims should not be understood as a waiver to achieve independent material protection for the features of the subclaims reference is made to. These features can also be arbitrarily combined with other features.

[0079] Features which are only disclosed in the description or features which are disclosed in conjunction with other features, either in the description or in any claim, can in principle be of essential importance to aspects of the invention by themselves. They can therefore also be included in any claim individually for differentiation from the state of the art.