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Patent Application Titled "Angle-Resolving Radar Sensor for Motor Vehicles" Published Online

September 4, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors Binzer, Thomas (Ingersheim, DE); Waldschmidt, Christian (Renningen, DE); Gross, Volker (Ditzingen, DE); Hellinger, Raphael (Pforzheim, DE); Kuehnle, Goetz (Hemmingen, DE); Treptow, Andre (Vaihingen An Der Enz, DE), filed on May 16, 2012, was made available online on August 21, 2014.

No assignee for this patent application has been made.

Reporters obtained the following quote from the background information supplied by the inventors: "Motor vehicles are increasingly equipped with so-called ACC (adaptive cruise control) systems which allow the distance between the host vehicle and a preceding vehicle to be automatically controlled. For this purpose, the distances and azimuths as well as relative velocities of preceding vehicles are measured with the aid of the radar sensor, e.g., an FMCW LRR (frequency-modulated continuous wave long-range radar) sensor. These radar sensors typically work with a frequency of 24 GHz or 77 GHz.

"Lens antennas are, for example, used in the case of long-range radar (LRR) sensors for motor vehicles. These include a radar lens and multiple antenna elements which are also referred to as primary radiators. The primary radiators are, for example, configured as patch antennas. To obtain an angular misalignment of the primary sensitivity directions of the patch antennas, the primary radiators are situated in a series transversely to the optical axis of the radar sensor. If, as is often the case, the same antenna elements are used to emit the radar signal and to receive the radar echo, the primary radiation directions of the antenna elements also have corresponding deviations. The greater the distance a primary radiator is from the optical axis of the radar lens, the stronger does the primary radiation direction of the antenna element in question deviate from the optical axis. This deviation is also referred to as squinting. When specifying the widths of the sensitivity ranges of the antenna elements, a compromise must be made between a wide range of vision and a good angle resolution.

"The radar sensors used so far in this context have four antenna elements or antenna patches, for example. Each antenna element is assigned exactly one channel of an evaluation device of the radar sensor. The antenna elements each have a directional characteristic having a main lobe, i.e., a limited range of high sensitivity which includes a sensitivity maximum. The main lobes of the antenna elements together cover a certain angle range. Since the sensitivity ranges overlap, radar echoes from a single radar object are received in multiple antenna elements and thus in multiple channels. For an idealized, approximately punctiform radar object at a given azimuth, there is a characteristic phase-amplitude relation between the signals received in the different channels. Due to the propagation differences of the radar echoes from the radar object to the different antenna elements, a phase difference results which is approximately proportional to the azimuth with regard to an optical axis of the radar sensor and proportional to the distance between the antenna elements in the direction which is at a right angle to the optical axis, as well as inversely proportional to the wave length of the radar waves. The amplitude ratios between the received signals are a function of the azimuth and of the sensitivity curves of the antenna elements . By evaluating the phase relations and/or by evaluating the amplitude relations, it is possible to determine the azimuth of a located radar object.

"The signal received by an assigned antenna element is evaluated in the channels of the radar sensor. In an FMCW radar, for example, in which the frequency of the transmitted radar signal is modulated periodically, the received signal is mixed for each antenna element with the signal transmitted at the receiving point in time, by maintaining the phase and amplitude relations, so that an intermediate frequency signal is obtained whose frequency corresponds to the frequency difference between the transmitted and the received signal. The intermediate frequency signals may be evaluated in an electronic evaluation device. For example, they maybe digitized using analog/digital converters and then further processed digitally. For example, a frequency spectrum of the intermediate frequency signal is recorded in every channel of the evaluation device during each measurement period. In this frequency spectrum, each located object is indicated by a peak whose frequency range is a function of the distance and the relative velocity of the object in question. By modulating the transmitted frequency using different ramp gradients, it is possible to compute the distance and the relative velocity from the obtained frequency ranges.

"The dependency of the amplitude and phase of the signal received on an antenna element on the azimuth of the located object may be illustrated in an antenna diagram for a standard object at a given distance and having a given reflection intensity. By aligning the amplitudes and/or phases obtained for the same object from different antenna elements with the appropriate antenna diagrams, the azimuth of the object in question may be determined in a second evaluation stage."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "An object of the present invention is to provide a radar sensor having an improved angle detection capacity and at the same time to keep the necessary circuitry complexity within limits.

"According to the present invention, this object is achieved by at least two antenna elements connected to the same receive channel together having a directional characteristic having at least two main lobes having different primary sensitivity directions.

"Thus, six antenna elements and four receive channels may be provided, for example, two antenna elements being connected to one joint receive channel, two antenna elements being each connected to one innate additional receive channel and the remaining two antenna elements being, in turn, connected to one additional joint receive channel. The antenna elements, which are each connected to a single receive channel, cover, for example, central angle areas, while two antenna elements, which are connected to a joint channel, each have a primary sensitivity direction on the left- and the right-hand sides of the central area. In this way, they may be used both to detect an object in a left-hand area and in a right-hand area. It is therefore possible to cover a larger range of vision using the same number of receive channels, without reducing the angle resolution.

"For example, at least two antenna elements, each of which has a directional characteristic having a main lobe having a primary sensitivity direction, may be connected to the same receive channel, so that they have the aforementioned directional characteristic having at least two main lobes having different primary sensitivity directions.

"The directional characteristic is, in particular, the receiving directional characteristic of the particular antenna elements. The directional characteristic in principle corresponds to the transmitting directional characteristic with respect to the spatial parameters when one antenna element is used for transmitting and receiving.

"The receive channels may, in particular, be channels of an evaluation device of the radar sensor which are each configured to process signals of the corresponding antenna elements.

"The at least two main lobes of the directional characteristic of the antenna elements connected to the same receive channel may be separate, i.e., not overlapping, main lobes. This makes it easier to distinguish from which main lobe a received radar signal originates.

"Advantageous embodiments and refinements of the present invention are described herein.

"At least one other antenna element connected to another channel may have a directional characteristic having at least one main lobe having a primary sensitivity direction which lies between two primary sensitivity directions of the aforementioned at least two main lobes. This makes it possible to obtain additional information regarding angle detection of a radar object. The aforementioned at least one main lobe may overlap the at least one of the aforementioned at least two main lobes.

"In one specific embodiment, the radar sensor has a radar lens, in particular a collective lens, situated upstream from the antenna elements. Different primary sensitivity directions of the antenna elements may then be easily achieved with the aid of a different lateral offset of the antenna elements with regard to an optical axis of the radar lens. The sequence in which the primary sensitivity directions of the individual main lobes follow successively in the azimuthal direction may then correspond to the sequence of the antenna elements situated in series.

"Thus, the antenna elements may, for example, be situated in series, at least another antenna element connected to another receive channel being situated between the at least two antenna elements connected to the same receive channel. This additional antenna element then has a primary receiving direction which lies between two primary receiving directions of the first-named at least two antenna elements.

"The antenna elements may be patch antennas, for example.

"'Antenna elements' in the sense of this application are, however, also to be understood to mean antenna columns using which a beam formation in the elevation direction may take place, for example. Such antenna columns run vertically when the radar sensor is installed in the vehicle. The antenna columns are then situated horizontally next to one another. The phase relation and the performance distribution between the different subelements (patches) within an antenna column determine the directional characteristic in the elevation.

"The antenna elements may be transmitting and receiving antenna elements.

"The antenna elements maybe situated outside of a focal plane (image plane) of the radar lens. By placing the antenna elements at a slightly smaller or greater distance from the radar lens, for example, phase deviations of the radar signals, which are pronounced more or less strongly, occur for the individual antenna elements depending on the lateral distance from an optical axis of the radar lens. If, for example, antenna elements connected to the same receive channel are situated on the left and on the right of the optical axis at different distances from the optical axis, different phase relations may result among the received signals of the receive channels for positions of a radar object at the same angle distance on the left or on the right of the optical axis.

"The radar sensor may have an evaluation device which is configured to determine an angle position of a detected radar object on the basis of amplitudes and phases of received radar signals of the antenna elements.

"The evaluation device may be configured to distinguish between angle positions, assigned to the particular main lobes, of a radar object detected by the aforementioned at least two main lobes on the basis of amplitudes and phases of received radar signals of the antenna elements connected to the same receive channel and on the basis of amplitudes and phases of received radar signals of one or multiple additional antenna element(s) connected to one or multiple additional receive channel(s). For example, the antenna elements may be configured in such away that, in the directional characteristics of the antenna elements, angle positions, which are associated with different main lobes of the antenna elements connected to the same receive channel, are distinguishable based on associated amplitudes and phases and the amplitudes and phases, associated with the angle positions, of one or multiple additional receive channel(s), so that the evaluation device is capable of distinguishing between angle positions, associated with the particular main lobes, of a radar object detected by the aforementioned at least two main lobes.

"In one specific embodiment, the evaluation device may be configured to take into account, during the determination of the angle position, a phase difference between received radar signals from receive channels which are connected to the antenna elements which have directional characteristics having overlapping main lobes. By forming the phase difference, phase information from overlapping main lobes may be used particularly well.

"At least two primary sensitivity directions of the antenna elements connected to a first receive channel may be nested with at least two primary sensitivity directions of the antenna elements connected to another channel. If the primary sensitivity directions are nested in the azimuthal direction, they are thus situated on the left in a different sequence than on the right, from the inside to the outside in each case. For example, the evaluation device maybe configured to distinguish between angle positions of a radar object detected by two main lobes of antenna elements connected to the first receive channel on the basis of a phase difference between received radar signals of the first receive channel and of the aforementioned other receive channel.

"In the following, exemplary embodiments are elucidated in greater detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 shows a block diagram of the radar sensor according to the present invention.

"FIG. 2 shows a representation of an antenna diagram.

"FIG. 3 shows sections of a diagram which shows the angular dependency of the phase of the directional characteristic of two channels.

"FIG. 4 shows sections of a diagram which shows the angular dependency of the phase difference of the directional characteristic of the channels.

"FIG. 5 shows a drawing of another example of an antenna system of the radar sensor."

For more information, see this patent application: Binzer, Thomas; Waldschmidt, Christian; Gross, Volker; Hellinger, Raphael; Kuehnle, Goetz; Treptow, Andre. Angle-Resolving Radar Sensor for Motor Vehicles. Filed May 16, 2012 and posted August 21, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4348&p=87&f=G&l=50&d=PG01&S1=20140814.PD.&OS=PD/20140814&RS=PD/20140814

Keywords for this news article include: Patents.

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