DE102021111253A1 - Lens antenna with integrated interference filter structure - Google Patents

Abstract

The present invention relates to a lens antenna (300) comprising an interference filter structure (310) integrated into the lens antenna. The present invention also relates to a device for radar measurements. The device includes a transceiver circuit for a radar signal. The transceiver circuit includes a frequency multiplier that is designed to generate a center frequency of the radar signal from a fundamental frequency. The device further includes a lens antenna (300) coupled to the transceiver circuitry (124). The lens antenna (300) includes an interference filter structure (310) integrated into the lens antenna (300), which is designed to attenuate signal components of the radar signal by the fundamental frequency. The present invention further relates to a method of manufacturing a lens antenna (300). The method includes molding an interference filter structure (310) into a lens antenna (300).

Description

technical field

Exemplary embodiments relate to a lens antenna with an interference filter structure integrated into the lens antenna, in particular for radar measurements. Further exemplary embodiments relate to a method for producing a lens antenna.

background

Radar-based measurement systems are becoming increasingly important in various industrial, security and automotive applications. Especially in industrial applications under harsh conditions, such as in blast furnaces or for level detection, or for non-destructive testing, distance measurements and measurements in machine tools, as well as in high-resolution imaging and material characterization, radar-based measuring systems are increasingly replacing conventional measuring systems. In order to meet the increasing demands on accuracy and resolution, higher frequencies with large modulation bandwidths are necessary. In the past, III-V technologies such as gallium arsenide (GaAs) were the only way to reach operating frequencies above 200 GHz. However, III-V technologies are associated with high production costs and a low level of integration. As a result, these technologies are largely too inefficient and uneconomical for large-volume, cost-effective measuring systems. Thanks to recent advances in silicon-germanium technology (SiGe), frequencies above 200 GHz are also possible with a high degree of integration and low energy consumption at the same time. The Si-Ge technology thus enables cost-effective mass production.

For example, an ultra-compact, high-resolution, and highly accurate SiGe transceiver for radar measurements can be integrated on an MMIC (Monolithic Microwave Integrated Circuit) together with on-chip antennas. A lens antenna can also be attached to the MMIC that collimates and focuses the radar signal. In order to generate high output frequencies in such MMICs, a multiplication stage is used, for example, which multiplies a basic signal with a lower frequency, a so-called fundamental frequency. The basic signal is generated in a voltage-controlled oscillator. The multiplication stage can suppress the basic signal, but this is only possible to a limited extent. It is difficult to implement filter structures on the MMIC. Push-push doublers can at least attenuate the fundamental frequency to a high degree. Nevertheless, the basic signal sometimes speaks through in the output signal of the radar sensor. In FMCW operation of the radar measurement system (Frequency Modulated Continuous Wave), this can in turn lead to false targets in the reception spectrum of the radar sensor. Due to multiple reflections in the lens antenna, the false target can overlap in the reception spectrum in such a way that it cannot be distinguished from the actual target. In the case of mixer concepts, speaking through the basic signal can also reduce the signal quality. In most cases, the low-frequency harmonic frequency components of the basic signal are higher in the radiated power and, under certain circumstances, make it difficult or even prevent official approval of the measuring system or compliance with EMC guidelines (electromagnetic compatibility). For example, different approval regulations apply to radiation in the frequency range around 240 GHz than to 60 GHz or 120 GHz.

It can therefore be regarded as an object of the present invention to create an improved filter concept, for example for radar applications.

summary

The above object can be achieved with the help of the independent claims of the present disclosure. Dependent claims of the present disclosure may specify advantageous embodiments.

According to a first aspect, the present invention relates to a lens antenna, comprising an interference filter structure integrated into the lens antenna.

The lens antenna can be part of a radar measurement system. The interference filter structure is used, for example, to filter undesired frequency components of a radar signal. The lens antenna can be part of a receiver and/or transmitter system for electromagnetic waves, for example in the radio and/or terahertz range.

In some exemplary embodiments, the interference filter structure includes material sections of different permittivity.

Since, for example, the radar signal propagates at different speeds in the material sections of different permittivity, the material sections can be designed to cause a phase delay of 180° in the undesired frequency components.

In some embodiments, first portions of material of the interference filter structure include a first dielectric and second material cuts the interference filter structure on a second dielectric.

In some embodiments, the interference filter structure includes ridges and fluid-filled valleys in a material of the lens antenna.

The elevations can have a different permittivity than the depressions.

In some embodiments, the interference filter structure runs along an ellipsoidal surface around a feed point for the lens antenna.

As a result, a signal radiated at the feed point, such as the radar signal, can impinge uniformly on the interference filter structure. In other words, areas of a wave front of the signal can impinge on the interference filter structure in phase. The signal propagates approximately spherically, starting from the feed point. The feed point is, for example, a radiation point of a patch antenna for the radar signal.

In some exemplary embodiments, the interference filter structure includes material sections of different permittivity along the ellipsoid surface.

In some embodiments, the interference filter structure includes ridges spaced apart on the ellipsoid surface.

In some exemplary embodiments, the elevations are at least partially ring-shaped.

In some exemplary embodiments, the elevations are designed to be rotationally symmetrical.

In some further exemplary embodiments, the elevations are mirror-symmetric.

In some embodiments, spaces between the ridges are filled with air.

wobei c₀ der Lichtgeschwindigkeit, f einer Frequenz eines unerwünschten Frequenzanteils, ε_r,1 einer Permittivität eines Materials der Erhöhungen und ε_r,2 einer Permittivität eines Materials der Zwischenräume entsprechen.In some embodiments, a height corresponds to the bumps $\frac{c_{}}{}$$\frac{{}_0}{2\times f\times \left(\sqrt{e_{\mathrm{right}\mathrm{,1}}}-\sqrt{e_{\mathrm{right}\mathrm{,2}}}\right)},$

where c ₀ corresponds to the speed of light, f to a frequency of an unwanted frequency component, ε _r,1 to a permittivity of a material of the ridges and ε _r,2 to a permittivity of a material of the gaps.

The ridges and gaps can thus introduce a 180° phase lag between parts of the unwanted frequency component that impinge on the ridges and parts of the unwanted frequency component that impinge on the gaps. As a result, the interference filter structure can cause destructive interference and filter the unwanted frequency component.

In some embodiments, the lens antenna and/or the interference filter structure comprises Teflon, resin and/or a polymer.

Resin or polymer can be used as printing materials of an additive manufacturing process. Due to the additive manufacturing process, the interference filter structure can have more precisely shaped contours with resin or polymer than with Teflon.

Teflon can be machined using conventional manufacturing processes such as turning or milling. Teflon can have better frequency properties than resin or polymer in terms of losses, even towards higher frequencies.

In some exemplary embodiments, the interference filter structure is designed to attenuate an unwanted frequency component of a signal in the radio and/or terahertz range.

In some embodiments, the unwanted frequency component comprises a fundamental frequency of an oscillator, where the oscillator is part of a transceiver circuit that provides the signal for the lens antenna.

The transceiver circuit is part of a radar measurement system, for example, and is designed to transmit and receive a radar signal. Other components of the transceiver circuit, such as a frequency multiplier, can condition the fundamental frequency of the oscillator, i.e. double it.

In some exemplary embodiments, the interference filter structure is designed to cause destructive interference for an unwanted frequency component.

In some embodiments, the lens antenna further includes a first part and a second part detachable from the first part. The interference filter structure may be integral with the first part and enclosed by the first and second parts in an assembled state.

Thus, when manufacturing the lens antenna, the interference filter structure can be easily integrated into the lens antenna.

In some exemplary embodiments, the lens antenna further comprises at least one fastening pin which is designed to positively connect the first and the second part of the lens antenna to one another.

In some exemplary embodiments, the interference filter structure comprises different dielectric material layers in a radial direction starting from a feed point for the lens antenna.

For example, the interference filter structure thus includes a Bragg filter that can filter an unwanted frequency component of a transmission signal.

According to a second aspect, the present invention relates to a device for radar measurements, comprising a transceiver circuit for a radar signal. The transceiver circuit includes a frequency multiplier that is designed to generate a center frequency of the radar signal from a fundamental frequency. The device further includes a lens antenna coupled to the transceiver circuitry.

The lens antenna includes an interference filter structure integrated into the lens antenna, which is designed to attenuate signal components around the fundamental frequency.

The frequency multiplier is, for example, part of a multiplication stage for frequency processing of the radar signal. The frequency multiplier can roughly double the fundamental frequency. For the radar measurements, the radar signal can be modulated in a frequency bandwidth around the center frequency.

According to a third aspect, the present invention relates to a method of manufacturing a lens antenna. The method includes molding an interference filter structure into a lens antenna.

In some embodiments, molding includes applying an additive manufacturing process.

In some embodiments, the additive manufacturing process includes stereolithography and/or selective laser sintering.

Further embodiments of the apparatus and method may include various of the lens antenna embodiments described above.

character list

• 1 einen Querschnitt einer herkömmlichen Radarvorrichtung;
• 2 einen Querschnitt einer herkömmlichen dielektrischen Filterplatte;
• 3 einen Querschnitt einer erfindungsgemäßen Linsenantenne;
• 4a, b eine Explosionsdarstellung der erfindungsgemäße Linsenantenne in zwei weiteren Ausführungsformen;
• 5a-d dielektrische Eigenschaften der Materialien FLGPCL03 und PA2200;
• 6a, b einen Richtfaktor über verschiedene Abstrahlwinkel für eine Linsenantenne aus FLGPCL03 beziehungsweise PA2200;
• 7a-c einen Spannungspegel eines empfangenen Radarsignals über verschiedene Entfernungen für eine Referenzantenne, eine Linsenantenne aus FLGPCL03 beziehungsweise PA2200.

Some examples of devices and/or methods are explained in more detail below with reference to the accompanying figures, merely by way of example. Show it:

• 1 a cross section of a conventional radar device;
• 2 a cross section of a conventional dielectric filter plate;
• 3 a cross section of a lens antenna according to the invention;
• 4a, b an exploded view of the lens antenna according to the invention in two further embodiments;
• 5a-d dielectric properties of materials FLGPCL03 and PA2200;
• 6a, b a directivity factor over different beam angles for a lens antenna from FLGPCL03 or PA2200;
• 7a-c a voltage level of a received radar signal over different distances for a reference antenna, a lens antenna from FLGPCL03 and PA2200, respectively.

description

Various embodiments will now be described in more detail and with reference to the accompanying drawings, in which some embodiments are illustrated.

Although example embodiments can be modified and altered in various ways, example embodiments are illustrated in the figures and are described in detail herein. It should be understood, however, that example embodiments are not intended to be limited to the precise forms disclosed, but rather that example embodiments are intended to cover all functional and/or structural possibilities, equivalents, and alternatives falling within the scope of the invention.

A transceiver circuit for a radar signal can include a frequency multiplier, which generates the radar signal from a basic signal with a fundamental frequency of an oscillator of the circuit. The frequency of the radar signal can be a multiple of the fundamental frequency. A lens antenna may be coupled to the transceiver circuitry to receive the radar signal, such as from on-chip antennas or other antennas structures is radiated to focus. It may be necessary to avoid emitting unwanted frequency components of the radar signal, such as the oscillator's fundamental signal, as they can lead to false targets or problems with frequency approvals and compliance with EMC guidelines. Therefore, filter structures are usually used.

Waveguides are known, into which the radar signal is coupled and which adjust the radar signal in a desired manner, for example through the transmission properties of the waveguide (cut-off frequency). In addition, common filter structures can be introduced into the waveguide. In addition, interference filter plates of different permittivity or with a suitable structure are known, which are placed in front of the on-chip antenna or the antenna structure used. They use interference to filter out unwanted frequency components. However, the mentioned filter structures can be bulky, expensive and difficult to align.

It can therefore be seen as an object of the present invention to provide an improved concept for filtering unwanted frequency components.

1 Fig. 12 shows the cross section of a conventional radar device 100 which generates and radiates a radar signal. The radar device 100 includes an ellipsoidal solid lens antenna 110 mounted on a circuit board 130 along with an FMCW radar transceiver 120 . The lens antenna 110 is arranged in front of the FMCW radar transceiver 120 such that the lens antenna 110 and the circuit board 130 enclose the FMCW radar transceiver 120 . The FMCW radar transceiver 120 includes an open-cavity QFN package 122 (Quad Flat No Leads) and a SiGe transceiver MMIC 124 attached to an inside of the QFN package 122 with two on-chip patch antennas 126 .

A fundamental signal of the radar device 100 is generated, for example, by a voltage controlled oscillator (not shown) having a fundamental frequency of 112 GHz (gigahertz). The basic signal can be divided into two paths, each of which feeds a frequency multiplier, here a frequency doubler, for a TX or RX path. Since an output frequency of the radar signal can be up to 250 GHz, this can be too high to connect the associated paths via bonding wires. It may therefore be necessary to integrate the two patch antennas 126 directly on the chip 124 for transmitting and receiving the radar signal. The lens antenna 110 can be used to focus the radar signal.

The phase-locked loop (PLL) stabilized modulation range of the FMCW radar transceiver 120 can be from 198 GHz to 250 GHz, resulting in an FMCW ramp bandwidth of 52 GHz - suitable for high-resolution radar measurements. By integrating HF components on the SiGe transceiver MMIC 124, it may be necessary to connect only low-frequency signal paths via bonding wires. This may allow the SiGe transceiver MMIC 124 to be built into the QFN package 122, which in turn is mounted on the circuit board 130, such as a standard FR-4 circuit board.

The circuit board 130 may include a front end with analog signal stabilization and IF (intermediate frequency) circuitry. The front end may be connected to a back end, which may include a reference crystal oscillator, power supply circuitry, and a microcontroller. The microcontroller is used, for example, for configuration, data processing and data transmission of measurement data. To do this, the microcontroller can forward sampled IF data to a computer via a USB interface. The microcontroller can also be responsible for configuring PLL chips.

That is, the radar device 100 can generate an output signal with a center frequency of 224 GHz by using a frequency doubler to double a fundamental signal of a voltage controlled oscillator with a fundamental frequency of 112 GHz. This signal generation concept can suffer from parasitic feedthrough of the fundamental signal through the frequency doublers. Then, in addition to the desired, doubled output signal, the basic signal can also be emitted. Thus, for a real target of the radar measurements, a false target can appear at half the distance in the range spectrum, which can lead to ambiguity when determining the distance. Since the talk-through cannot be completely suppressed at the chip level alone, for example with a better frequency doubler topology and circuit, an external filter structure can help.

wobei d der Tiefe, c₀ der Lichtgeschwindigkeit, f der fundamentalen Frequenz, ε_r,1 einer Permittivität eines Materials der Erhöhungen und ε_r,2 einer Permittivität eines Materials Längsschlitze (z.B. Luft) entsprechen. Bei einem Ausgangssignal 250 der Radarvorrichtung 100, das eine gewünschte, etwa doppelte so hohe Frequenz wie die fundamentale Frequenz aufweist, kann ein Passieren der Längsschlitze und Erhöhungen eine Phasendifferenz von λ (360°) hervorrufen. Somit sind dazugehörige Anteile des Ausgangssignals 250 phasengleich und überlagern sich konstruktiv. Da es sich bei der Filterplatte 200 um eine externe Komponente handelt, die vor einem Radarsensor platziert werden kann, kann sie eine funktionale, aber sperrige Lösung sein. Außerdem kann es notwendig sein, die Filterplatte 200 manuell auszurichten, was einen Implementierungsaufwand erhöhen kann.As in 2 shown, for example, a dielectric filter plate 200 can be used. 2 12 shows a cross-section of the filter plate 200. The transmit direction 210 indicates how a radar signal coming from a transceiver such as the radar device 100 propagates through the filter plate 200. FIG. Accordingly, radar device 100 (not shown here) would be arranged to the left of filter plate 200, for example. The filter plate 200 has longitudinal slits 220 . A depth of the longitudinal slits 220 can be formed, for a fundamental signal, around a fundamental Fre frequency to induce a phase difference of λ/2 (180°) between portions 230 of the fundamental signal impinging on the longitudinal slots 220 and portions 240 of the fundamental signal impinging on the ridges corresponding to the longitudinal slots 220. This can lead to destructive interference. That is, the fundamental signal around the fundamental frequency can be attenuated. The depth of the longitudinal slots can be determined using Equation 1 below. Equation 1: $\mathrm{i.e}=\frac{c_0}{2\times f\times \left(\sqrt{e_{\mathrm{right}\mathrm{,1}}}-\sqrt{e_{\mathrm{right}\mathrm{,2}}}\right)},$

where d corresponds to the depth, c ₀ to the speed of light, f to the fundamental frequency, ε _r,1 to a permittivity of a material of the elevations and ε _r,2 to a permittivity of a material longitudinal slits (eg air). For an output signal 250 of the radar device 100 having a desired frequency about twice the fundamental frequency, passing through the longitudinal slits and ridges can cause a phase difference of λ (360°). Thus, associated portions of the output signal 250 are in phase and constructively superimpose. Because the filter plate 200 is an external component that can be placed in front of a radar sensor, it can be a functional but bulky solution. Additionally, it may be necessary to manually align the filter plate 200, which may increase implementation effort.

The present invention may therefore aim to offer an alternative to the concepts described above.

3 shows a cross section of a lens antenna 300 according to the invention with an interference filter structure 310 integrated into the lens antenna 300. The lens antenna 300 can be an antenna which is designed to focus electromagnetic waves with frequencies in the radio and/or terahertz range, similar to an optical lens for Light. For this, the lens antenna 300 can bend the electromagnetic waves in an inside of the lens antenna 300 at a material transition. For the diffraction of the electromagnetic waves, the lens antenna 300 can consist at least in part of one or more dielectrics (such as resin, polymer or Teflon) and/or one or more composites of at least one dielectric. The lens antenna 300 may be ellipsoidal in shape to allow diffraction of waves at inner walls of the lens antenna 300 toward a focal point 330 . The focal point 330 can be located in an interior of the lens antenna 300 . The dielectrics and/or composites of lens antenna 300 may have different dielectric conductivities (permittivities) and refractive indices that affect propagation of the electromagnetic waves inside lens antenna 300 . The electromagnetic waves can be a signal from a transmitter system, which emits the electromagnetic waves as free-space waves via feed antennas. Starting from a feed point 320 of the lens antenna 300, the signal can propagate at least partially in the lens antenna 300 in an approximately spherical manner. The feeding point 320 can be located in an interior of the lens antenna 300 . Lens antenna 320 may also have multiple feed points, such as in the case of an array of feed antennas. The signal can be diffracted at the inner walls of the lens antenna 300 or at other material transitions in the lens antenna 300 (e.g. if the lens antenna 300 comprises different materials) and is emitted from the focal point 330 of the lens antenna 300 in a focused manner into an environment or to a receiver system. The lens antenna 300 can be part of the transmitter system, the receiver system, or a combined transmitter/receiver system with transmit and receive antennas. Thus, the lens antenna 300 can focus an outgoing signal of a transmission system, an incoming signal of a receiving system, or both an outgoing signal and an incoming signal. For example, in the case of a transceiver system, it may be transceiver circuitry of a radar device, such as radar device 100 .

The interference filter structure 310 can extend at least partially over a plane inside the lens antenna 300 . The interference filter structure 310 can have material sections made of different dielectrics and/or composites. The interference filter structure 310 may be curved around the feed point 320 along an ellipsoidal surface. The interference filter structure 310 can have the different material sections along the ellipsoid surface. The different material sections can be designed as different material thicknesses, i.e. as elevations and depressions in one or more materials of the interference filter structure 310. Alternatively or additionally, the material sections can be configured as different dielectric layers along an axis 340 through the feed point 320 and focal point 330 of the Lens antenna 300 may be formed. The interference filter structure 310 can introduce a phase delay at undesired frequency components of the signal, so that a more phase-delayed part of the undesired frequency components interfere destructively with a less phase-delayed part of the undesired frequency components and thus the undesired frequency components are attenuated. For example, the different material sections due to different permittivities of the material sections Cause phase delay of at least part of the unwanted frequency components.

The interference filter structure 310 can be closer to the feed point 320 or farther away than in FIG 3 be arranged shown. A distance between the interference filter structure 310 and the feed point 320 can be adjusted such that on the one hand the signal arrives at the interference filter structure 310 in the same phase as possible (i.e. close to the feed point 320) and on the other hand the interference filter structure 310 can be easily manufactured (i.e. at a certain distance from the feed point 320). . The lens antenna 300 can have a multi-part design in order to facilitate integration of the interference filter structure 310 into a material of the lens antenna 300 .

4a and 4b show an exploded view of the lens antenna 300 according to the invention in two further embodiments. The ovoid lens antenna 300 is shown in two parts, a top part 410 and a bottom part 420, to reveal the interference filter structures 310a and 310b integral with the part 420, respectively. The interference filter structures 310a and 310b run along an ellipsoidal surface around a feed point of a radar signal. The feed point may be located on an on-chip antenna (not shown), such as on-chip antenna 126, of a radar device, such as radar device 100, for example. The feed point can be on an axis 430 of the lens antenna 300 . If one assumes that wave fronts of the radar signal propagate approximately spherically from the feed point, the wave fronts can impinge on the interference filter structure 310a or 310b in phase. The ellipsoidal surface can thus be formed approximately as a sphere. In the 4a The interference filter structure 310a shown has (at least) three slot-shaped, “linear” depressions 440 on the ellipsoid surface and (at least) three elevations 450 corresponding thereto. The indentations 440 may run along meridians on the ellipsoidal surface. The poles associated with the meridians may be located outside the lens antenna 300 (when lengthened) the indentations 332a would converge. The depressions 440 can be mirror-symmetrical to a plane, the plane being spanned by an axis 460 and the axis 430 . In other exemplary embodiments, the interference filter structure 310a can include more or fewer depressions 440 and elevations 450 than are illustrated here. In the 4b The interference filter structure 310b shown has three annular (“circular”) depressions 440 that are rotationally symmetrical to the axis 430 on the ellipsoid surface and four elevations 450 that correspond thereto. The lower part 420 of the lens antenna 300 can have fastening pins 470 (here four fastening pins) with which the lower part 420 can be positively connected to the upper part 410 . The depressions 440 can be filled with air or another fluid. A depth of the depressions 440 can be calculated according to Equation 1 in order to cause destructive interference at an undesired frequency component of the radar signal according to a principle similar to the filter plate 200, while leaving a desired frequency component almost unchanged or superimposing it constructively. A width of the depressions 440 or elevations 450 can be determined, for example, using simulations of a wave propagation of the radar signal for a shape of the lens antenna 300 and the interference filter structure 310 and for a wavelength of the undesired frequency component. The lens antenna 300 can replace the lens antenna 110 of the radar device 100, for example. The following simulations and measurements refer to this case. However, the lens antenna 300 can also be combined with any other receiver and/or transmitter systems that require a lens antenna and a filter structure. For example, the lens antenna 300 can be used for a receiver circuit that receives a signal in the terahertz range or electromagnetic signals in other frequency ranges. Likewise, the lens antenna 300 can be used for a transmitter circuit or a transceiver circuit that is operated in frequency ranges other than those mentioned here. In other embodiments, the interference filter structure of the lens antenna 300 can have other forms that follow said interference principle. For example, the interference filter structure can have material layers of different permittivity along the axis 430 and thus, similar to a Bragg filter, eliminate the unwanted frequency component through destructive interference.

While the conventional lens antenna 110 may be machined from a solid PTFE body, the lens antenna 300 with the integrated interference filter structures 310a, 310b may be too complex for a mechanical manufacturing process. It can therefore be advantageous to produce the interference filter structures 310a, 310b using additive manufacturing methods, such as stereolithography or selective laser sintering.

Additive manufacturing processes are a description of manufacturing processes in which a workpiece is built up layer by layer. In contrast to conventional manufacturing processes, in which the workpiece is manufactured by selectively removing material from a blank, additive manufacturing processes add material selectively. This can enable the production of very complex shapes.

In stereolithography (SLA), a UV light-sensitive liquid resin is used as the base material. A UV laser with a mirror-based scanning unit processes the base material using selective photopolymerization. The UV laser scans a surface of the workpiece along a path on a platform. The path is specified using slicer software. As soon as a laser beam from the UV laser hits the liquid resin, it solidifies immediately. When a layer of the workpiece is fully polymerized, it is taken out of the liquid resin. After all layers of the workpiece are fully fabricated, it is placed in a UV chamber to cure it. In geometries of the workpiece that extend away from a base body of the workpiece, ie in overhanging components of the workpiece, stresses occur during the polymerization. So that the stresses do not cause deformations and crumbling in the solidified resin, support structures are used, which are removed again in a post-processing step.

In contrast to SLA, in selective laser sintering (SLS) a polymer powder is distributed over a platform using a blade coater. An infrared heat lamp heats the powder to just below the melting point. A carbon dioxide laser fuses particles of the powder by selectively heating them above the melting point. A process step is completed by lowering the platform by one layer. Then comes a next process step and the process cycle repeats itself until all layers of the workpiece have been built up. The finished workpiece is removed and cleaned of unprocessed powder. SLS can have the advantage of incorporating the workpiece into the raw powder and consequently eliminating the need for support structures for overhanging components of the workpiece.

These two additive manufacturing methods can be used to manufacture the lens antenna 300 with an integrated interference filter structure 310a, 310b. First, electromagnetic properties of the respective materials of the additive manufacturing process can be determined. An MCK measuring device from Swissto12 SA can be used to determine material parameters. A metrological evaluation can be based on a quasi-guided free space wave method. The corresponding measurement setup includes two waveguides and a flat test piece made of the respective material. A corrugation on the inner walls of the waveguide can generate a flat wave front, so that a decoupled wave at the end of the waveguide covers the entire surface of the test object in phase. The test object can cover an entire aperture of the waveguide. A dielectric constant and a dielectric loss of the specimens can be determined from measured scattering parameters using a curve fitting algorithm. The dielectric constant can be varied for a given sample thickness of the test object until the transmission and reflection curves match as closely as possible. Since the materials are not magnetic, a permeability of the materials can be assumed to be 1. Standard materials such as clear resin "FLGPCL03" and "PA2200" (PA12) respectively can be used for SLA and SLS. In other embodiments, the lens antenna 300 is made of a different material than the materials listed here. The lens antenna 300 can also be made of Teflon and processed using a conventional manufacturing process to integrate the interference filter structure, such as interference filter structure 310a or 310b, into the lens antenna 300.

5a and 5b show dielectric properties of a test piece made of FLGPCL03. 5c and 5d show the dielectric properties of a test specimen made of PA2200. 5a and 5c show a course of a permittivity over the examined frequencies and 5b and 5d show the course of a loss factor over the examined frequencies of the respective material. For this purpose, a square test piece with FLGPCL03 or PA2200 of size 40x40x4 mm ³ (cubic millimeters) was printed using SLA and SLS in order to extract the dielectric parameters of the test pieces. Measurements of the dielectric parameters were carried out in the V-band since a measuring device for the Y-band was not available. For a further evaluation, values for the dielectric parameters from the measurements in the V-band were also used in the Y-band.

6a and 6b show simulation results of a directivity factor over different radiation angles of an unwanted frequency component with a fundamental frequency of 112 GHz. The simulation results are shown for each of the two above-described embodiments of lens antenna 300 with interference filter structure 310a and 310b from PA2200 and FLGPCL03, respectively. A conventional reference lens 610 or 620 without an interference filter structure made of the respective material is used as a comparison. The reference lenses 610 and 620 can have a simulated directivity of 31 dBi (decibels referenced to an isotropic radiator) for both materials. The simulations of the directivity factor did not take into account the efficiency of the antenna, which is influenced by the material losses. In the main beam direction, for both interference filter structures 310a and 310b, a significant decrease in the directional factor can be observed, which can indicate a good filter effect. The SLS-printed PA2200 version of the lens antenna 300 can have a simulated rejection of about -33 dB (decibels) for the interference filter structure 310a and -30 dB for the interference filter structure 310b compared to the reference lenses 610 and 620. For the SLA-printed FLGPCL03 version of the lens antenna 300, a simulated rejection of -32 dB for the interference filter structure 310a and -21 dB for the interference filter structure 310b can result.

In the main beam direction (at 0°), the interference filter structure 310a performs best in this example, although larger side lobes occur outside of the main beam direction than with the interference filter structure 310b. In this example, however, the directivity factor in the side lobes for PA2200 is -5 dB for interference filter structure 310a and -15 dB for interference filter structure 310b below the main lobe directivity factor of reference antenna 610. In this example, for FLGPCL03 the directivity factor in the side lobes is -5 dB Interference filter structure 310a and -12 dB with interference filter structure 310b also below the main lobe directivity factor of the reference antenna 620.

To validate the approach described above, radar measurements were performed with a fixed reflector as the target. The radar measurement is described below, which is not intended to limit exemplary embodiments of the present invention to the specified values for a length of the antenna or losses. The reflector was placed in front of the radar transceiver 120 at a distance of 0.6 m (meters). 7a-c show a voltage level (in dBV; decibels referenced to 1 volt) of a received radar signal over various distances (on the horizontal axis; in meters) for a PTFE reference antenna ( 7a) , for the lens antenna 300 made of PA2200 with interference filter structure 310a and 310b ( 7b) or for the lens antenna 300 from FLGPCL03 with interference filter structure 310a and 310b ( 7c ). As in 7a shown, the false target 710 occurs in the measurements with the PTFE reference antenna at half the distance of 0.3 m. Multiple reflections 720 within the reference antenna show up as peaks behind the true target 730 and at close range. In 7b and 7c no false target 710 appears at half the distance in the measurements with the two embodiments 310a and 310b of the lens antenna 300, that is to say it was successfully filtered out. The amplitude of the target peak 730 is significantly lower, which can mainly be attributed to dielectric losses in the material. A geometric length of the reference antenna can be 41 mm (millimeters). A geometric length of the lens antenna 300 made of PA2200 can be 38 mm and that of the lens antenna made of FLGPCL03 can be 36 mm. This can result in a loss of -0.3 dB for the reference antenna, -19 dB for the PA2200 version of the lens antenna 300 and -33 dB for the FLGPCL03 in radar operation where the radar signal has to pass the respective antenna twice -Version of the lens antenna 300 yield. Due to the interference filter structure 310a and 310b, additional dielectric losses of -7 dB for the interference filter structure 310a and -14 dB for the interference filter structure 310b can result within the lens material, each in the PA2200 version. The additional losses can result in -11 dB for the interference filter structure 310a and -12 dB for the interference filter structure 310b, both in the FLGPCL03 version. In this example, the losses for the interference filter structure 310b are slightly higher than those for the interference filter structure 310a. This may be due to a manufacturing process, as the lens antenna 300 with interference filter structure 310a can be printed approximately in one piece, while the lens antenna 300 with interference filter structure 310b may need to be printed in two parts (310, 320) to obtain unprocessed to remove powder from the recesses 332b. In this case, the unprocessed powder may otherwise be sealed inside the lens antenna 300 at an integral pressure. The two parts 310 and 320 can then be put together, which can create a small air gap between them, causing further losses.

Depending on the concept of signal generation, modern radar sensors can suffer from the fundamental signal leaking through at a fundamental frequency. This can lead to false targets in the range spectrum and thus to an ambiguity in target acquisition. The present invention therefore proposes a lens antenna with an interference filter structure integrated into the lens antenna. The interference filter structure can filter out unwanted signal components and thus avoid false targets, which enables reliable and robust measurements in industrial measurement applications. Two embodiments of the interference filter structure have been demonstrated by way of example. When choosing the interference filter structure, it may be necessary to find a compromise between transmission rejection and sidelobe levels. It was also proposed to print the interference filter structures shown using additive manufacturing processes. The measurements described showed that polyamide for SLS printing can be the better choice in terms of dielectric losses compared to the photopolymer resin of SLA printing, whereas the latter can be the cheaper choice.

The aspects and features described together with one or more of the previously detailed examples and figures can also be combined with one or more of the other examples to replace a same feature of the other example or to add the feature to the other example to introduce

The following claims are hereby incorporated into the Detailed Description, with each claim being able to stand on its own as a separate example. It should also be noted that although a dependent claim in the claims refers to a particular combination with one or more other claims, other examples may also include a combination of the dependent claim with the subject-matter of any other dependent or independent claim. Such combinations are hereby explicitly proposed, unless it is stated in individual cases that a specific combination is not intended. Furthermore, features of a claim are also intended to be included for any other independent claim, even if that claim is not directly defined as dependent on that other independent claim.

Claims (20)

Lens antenna (300), comprising an interference filter structure (310) integrated into the lens antenna (300). Lens antenna (300) according to claim 1 , wherein the interference filter structure (310) comprises material sections of different permittivity. Lens antenna (300) according to one of the preceding claims, wherein first material sections of the interference filter structure (310) have a first dielectric and second material sections of the interference filter structure (310) have a second dielectric. A lens antenna (300) according to any one of the preceding claims, wherein the interference filter structure (310) comprises ridges (450) and fluid-filled depressions (440) in a material of the lens antenna (300). A lens antenna (300) as claimed in any preceding claim, wherein the interference filter structure (310) extends along an ellipsoidal surface around a feed point (320) for the lens antenna (300). Lens antenna (300) according to claim 5 , wherein the interference filter structure (310) comprises material sections of different permittivity along the ellipsoid surface. Lens antenna (300) according to any one of Claims 5 or 6 wherein the interference filter structure (310) comprises ridges (450) spaced apart on the ellipsoid surface. Lens antenna (300) according to claim 7 , wherein the elevations (450) are at least partially ring-shaped. Lens antenna (300) according to claim 7 or 8th , wherein the elevations (450) are rotationally symmetrical. Lens antenna (300) according to claim 7 or 8th , wherein the elevations (450) are mirror-symmetrical. Lens antenna (300) according to any one of Claims 4 until 10 , where an amount of increases (450) $\frac{c_0}{2\times f\times \left(\sqrt{e_{\mathrm{right}\mathrm{,1}}}-\sqrt{e_{\mathrm{right}\mathrm{,2}}}\right)}$

where c ₀ corresponds to the speed of light, f to a frequency of an undesired frequency component, ε _r,1 to a permittivity of a material of the ridges (450) and ε _r,2 to a permittivity of a material of the ridges (450) corresponding spaces (440). . A lens antenna (300) as claimed in any preceding claim, wherein the lens antenna (300) and/or the interference filter structure (310) comprises teflon, resin and/or a polymer. Lens antenna (300) according to one of the preceding claims, wherein the interference filter structure (310) is designed to attenuate an unwanted frequency component of a signal in the radio and/or terahertz range. Lens antenna (300) according to Claim 13 , wherein the unwanted frequency component comprises a fundamental frequency of an oscillator, the oscillator being part of a transceiver circuit (124) which provides the signal for the lens antenna (300). A lens antenna (300) according to any one of the preceding claims, further comprising a first part (420) and a second part (410) detachable from the first part (420), the interference filter structure (310) being integrally formed with the first part (420) and in an assembled state, is enclosed by the first and second parts (410, 420). Lens antenna (300) according to any one of Claims 1 until 3 , wherein the interference filter structure (310) in a radial direction (330) starting from a feed point (320) for the lens antenna (300) comprises various dielectric material layers. Apparatus for radar measurements, comprising a transceiver circuit (124) for a radar signal, the transceiver circuit (124) comprising a frequency multiplier which is designed to generate a center frequency of the radar signal from a fundamental frequency, a lens antenna (300) coupled to the transceiver circuit (124), the lens antenna (300) comprising an interference filter structure (310) integrated into the lens antenna (300) and designed to attenuate signal components of the radar signal around the fundamental frequency. A method of manufacturing a lens antenna (300) comprising molding an interference filter structure (310) into a lens antenna (300). procedure according to Claim 18 , wherein the molding includes applying an additive manufacturing process. procedure according to claim 19 , wherein the additive manufacturing process comprises stereolithography and/or selective laser sintering.

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