LENS ANTENNA WITH INTEGRATED INTERFERENCE FILTER STRUCTURE

Description

Technical field

[0001] Exemplary embodiments relate to a lens antenna with an interference filter structure integrated into the lens antenna, particularly for radar measurements. Further exemplary embodiments relate to a method for manufacturing a lens antenna. background

[0002] Radar-based measurement systems are gaining increasing importance in various industrial, safety, and automotive applications. Particularly in industrial applications under harsh conditions, such as in blast furnaces or for level measurement, or for non-destructive testing, distance measurements, and measurements in machine tools, as well as in high-resolution imaging and material characterization, radar-based measurement systems are increasingly replacing conventional measurement systems. To meet the rising demands for 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 achieve operating frequencies above 200 GHz. However, III-V technologies are associated with high production costs and a low level of integration. This makes these technologies largely inefficient and uneconomical for large-scale, cost-effective measurement systems.Thanks to recent advances in silicon-germanium (SiGe) technology, frequencies above 200 GHz are now possible, combined with a high degree of integration and low energy consumption. SiGe technology thus enables cost-effective mass production.

[0003] An ultra-compact, high-resolution, and high-precision SiGe transceiver for radar measurements can, for example, be integrated with on-chip antennas on a monolithic microwave integrated circuit (MMIC). A lens antenna can also be attached to the MMIC to collimate and focus the radar signal. To generate high output frequencies in such MMICs, a multiplication stage is used that multiplies a lower-frequency fundamental signal. This fundamental signal is generated, for example, in a voltage-controlled oscillator. The multiplication stage can suppress the fundamental signal, but this is only possible to a limited extent. Implementing filter structures on the MMIC is difficult. Push-push doublers can attenuate the fundamental frequency with a high Q factor. Nevertheless, some crosstalk of the fundamental signal still occurs in the radar sensor's output signal.In FMCW (Frequency Modulated Continuous Wave) operation of the radar measurement system, this can lead to false targets in the radar sensor's received spectrum. Due to multiple reflections in the lens antenna, the false target can become so overlaid in the received spectrum that it is indistinguishable from the actual target. Crosstalk of the fundamental signal in mixer configurations can also reduce signal quality. The low-frequency harmonic components of the fundamental signal are usually higher in the radiated power and may complicate or prevent regulatory approval of the measurement system or compliance with EMC (Electromagnetic Compatibility) guidelines. For example, different approval regulations apply to transmission in the frequency range around 240 GHz than to 60 GHz or 120 GHz.

[0004] Patent publication DE 102012003948 B4 describes a level measurement system based on the radar principle. The system has at least one antenna that emits electromagnetic radiation, and at least one microwave window that separates a first chamber from a second chamber and is formed by a partially microwave-transparent disc. The disc has several cylindrical depressions on at least one side, arranged as points of a hexagonal coordinate system on the side.

[0005] Patent publication US 2006202909 A1, entitled "Dielectric lens, dielectric lens device, design method for dielectric lens, manufacturing method and transmit / receive equipment for dielectric lenses", discusses the following: A design process first determines a desired aperture distribution, then transforms the law of conservation of electrical power, Snell's law on the back side of a dielectric lens, and the formula representing the light path length constraint into simultaneous equations, and calculates the shapes of the surface and back side of the dielectric lens depending on the azimuthal angle Theta of a primary beam from the focal point of the dielectric lens to the back side of the dielectric lens.He then reduces the light path length in the formula showing the light path length constraint by a multiple of the wavelength when the coordinates on the surface of the dielectric lens reach a predetermined constraint thickness. A dielectric lens is designed by incrementally changing the azimuthal angle Theta from its initial value and repeating the second and third steps. This achieves reduction and quantization through zoning, while maintaining good antenna properties in the construction of a dielectric lens antenna.

[0006] US patent 2020363330 A1, entitled "Lens Assembly, Terahertz Wave Tomography System and Method, and Terahertz Wave Filter," discloses the following: The present disclosure provides a lens assembly, a terahertz wave tomography system and method, and a terahertz wave filter. The lens assembly consists of a first substrate and a second substrate arranged opposite each other; a seal, wherein the seal, the first substrate, and the second substrate enclose a cavity containing a magnetic fluid; and a plurality of electromagnetic generating units arranged on at least one first side of the first substrate near the second substrate or on a second side of the first substrate away from the second substrate.At least some of the electromagnetic generating units are configured to produce a magnetic field when a voltage is applied to shape the magnetic fluid into a Fresnel zone plate pattern.

[0007] WU GENG BO ET AL: "High-Gain Circularly Polarized Lens Antenna for Terahertz Applications", IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, IEEE, PISCATAWAY, NJ, US, Vol. 18, No. 5, May 1, 2019 (2019-05-01), pages 921-925, XP01 1722807 proposes a high-gain circularly polarized lens (CP lens) fed by a standard linearly polarized pyramidal horn operating at a frequency of 300 GHz. The lens consists of discrete, variable-height dielectric pillars and a grating. The height of each dielectric pillar is tuned to achieve the required transmission phase and to form a planar wavefront across the lens aperture. By integrating the lower dielectric grating with anisotropic character, the dielectric lens can convert the incident LP waves from the feeding source into CP radiation waves.3D printing technology is used to fabricate the terahertz CP lens, simplifying the manufacturing process and reducing costs. Measurements show that the designed lens can generate right-hand circular polarization radiation with a gain of 30.8 dBic at 300 GHz. The measured 1 dB gain bandwidth and 3 dB axis ratio bandwidth of the THz CP lens can reach 13.3% and 18.8%, respectively. A 3D-printed dielectric CP lens for use at 1 Hz frequencies is demonstrated, opening up new possibilities for high-speed wireless communication.

[0008] Patent EP 1 624 317 B1 proposes a radar sensor for motor vehicles, with optics that split a radar beam generated by a single antenna element into several partial beams emitted in different directions, characterized in that the optics have a diffraction grating.

[0009] Patent specification JP 4 238215 B2 proposes an antenna swertia consisting of at least one orthogonal mode converter connected to the feed point of at least one horn antenna, which is matched to receive an information signal. The horn antenna comprises a first and a second terminal, from which the information signal is received and subsequently segmented. It is connected to the aforementioned orthogonal mode converter so that the second component signal, which has the second polarized wave that orthogonally intersects the first polarized wave of the first component signal at the first terminal, can be supplied to the first polarized wave at the second terminal.

[0010] Therefore, the object of the present invention can be considered to be to create an improved filter concept, for example for radar applications. Summary

[0011] The above-mentioned problem can be solved using the independent claims of this disclosure. Dependent claims of this disclosure may specify advantageous embodiments.

[0012] According to a first aspect, the present invention relates to a lens antenna comprising an interference filter structure integrated into the lens antenna.

[0013] The lens antenna can be part of a radar measurement system. The interference filter structure serves, for example, to filter out unwanted frequency components of a radar signal. The lens antenna can be part of a receiver and / or transmitter system for electromagnetic waves, such as in the radio and / or terahertz range.

[0014] In some embodiments, the interference filter structure comprises material sections of different permittivity.

[0015] Since, for example, the radar signal propagates at different speeds in material sections with different permittivity, the material sections can be designed to cause a phase delay of 180° in the unwanted frequency components.

[0016] In some embodiments, first material sections of the interference filter structure have a first dielectric and second material sections of the interference filter structure have a second dielectric.

[0017] In some embodiments, the interference filter structure comprises raised areas and fluid-filled depressions in a material of the lens antenna.

[0018] The elevations may have a permittivity different from that of the depressions.

[0019] In some embodiments, the interference filter structure runs along an ellipsoidal surface around a feed point for the lens antenna.

[0020] This allows a signal emitted from the feed point, such as the radar signal, to arrive uniformly at the interference filter structure. In other words, portions of the signal's wavefront can arrive at the interference filter structure in phase. The signal propagates approximately spherically from the feed point. The feed point is, for example, the emission point of a patch antenna for the radar signal.

[0021] In some embodiments, the interference filter structure along the ellipsoid surface comprises material sections of different permittivity.

[0022] In some embodiments, the interference filter structure on the ellipsoid surface comprises spaced-apart protrusions.

[0023] In some embodiments, the raised areas are at least partially ring-shaped.

[0024] In some embodiments, the raised areas are rotationally symmetrical.

[0025] In some other embodiments, the raised areas are mirror-symmetrical.

[0026] In some embodiments, the spaces between the raised areas are filled with air.

[0027] In some embodiments, one height corresponds to the height of the elevations. c 0 2 × f × ε r , 1 − ε r , 2 , where c 0 is the speed of light, f is a frequency of an unwanted frequency component, ε r,1 is a permittivity of a material of the peaks and ε r,2 is a permittivity of a material of the spaces.

[0028] The peaks and gaps can thus create a 180° phase delay between parts of the unwanted frequency component that hit the peaks and parts of the unwanted frequency component that hit the gaps. This allows the interference filter structure to produce destructive interference and filter out the unwanted frequency component.

[0029] In some embodiments, the lens antenna and / or the interference filter structure comprises Teflon, resin and / or a polymer.

[0030] Resin or polymer can be used as printing materials in an additive manufacturing process. Due to the additive manufacturing process, the interference filter structure can have more precisely shaped contours when made with resin or polymer than with Teflon.

[0031] Teflon can be machined using conventional manufacturing processes such as turning or milling. Teflon can exhibit better frequency characteristics than resins or polymers with regard to losses, even at higher frequencies.

[0032] In some embodiments, the interference filter structure is designed to attenuate an unwanted frequency component of a signal in the radio and / or terahertz range.

[0033] In some embodiments, the unwanted frequency component includes a fundamental frequency of an oscillator, wherein the oscillator is part of a transceiver circuit that provides the signal for the lens antenna.

[0034] The transceiver circuit, for example, is part of a radar measurement system and is designed to transmit and receive a radar signal. Other components of the transceiver circuit, such as a frequency multiplier, can process the fundamental frequency of the oscillator, i.e., double it.

[0035] In some embodiments, the interference filter structure is designed to cause destructive interference for an unwanted frequency component.

[0036] In some embodiments, the lens antenna further comprises a first part and a second part that is detachable from the first part. The interference filter structure can be formed integrally with the first part and enclosed by the first and second parts in a combined state.

[0037] Thus, during the manufacturing of the lens antenna, the interference filter structure can be easily integrated into the lens antenna.

[0038] In some embodiments, the lens antenna further comprises at least one fastening pin designed to positively connect the first and second parts of the lens antenna.

[0039] In some embodiments, the interference filter structure comprises various dielectric material layers in a radial direction radiating from a feed point for the lens antenna.

[0040] For example, the interference filter structure includes a Bragg filter, which can filter out an unwanted frequency component of a transmitted signal.

[0041] 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 configured to generate a center frequency of the radar signal from a fundamental frequency. The device further comprises a lens antenna coupled to the transceiver circuit. The lens antenna includes an interference filter structure integrated into the lens antenna, configured to attenuate signal components around the fundamental frequency.

[0042] The frequency multiplier is, for example, part of a multiplication stage for frequency conditioning of the radar signal. The frequency multiplier can roughly double the fundamental frequency. For radar measurements, the radar signal can be modulated within a frequency bandwidth around the center frequency.

[0043] According to a third aspect, the present invention relates to a method for manufacturing a lens antenna. The method comprises forming an interference filter structure into a lens antenna.

[0044] In some embodiments, the molding process involves the application of an additive manufacturing process.

[0045] In some embodiments, the additive manufacturing process includes stereolithography and / or selective laser sintering.

[0046] Further embodiments of the device and the method may include various embodiments of the lens antenna described above. Character description

[0047] Some examples of devices and / or methods are explained in more detail below with reference to the accompanying figures. These show: Fig. 1 a cross-section of a conventional radar device; Fig. 2 a cross-section of a conventional dielectric filter plate; Fig. 3 a cross-section of a lens antenna according to the invention; Fig. 4a an exploded view of the lens antenna according to the invention in two further embodiments; Fig. 5a dielectric properties of the materials FLGPCL03 and PA2200; Fig. 6a the directivity factor over different beam angles for a lens antenna made of FLGPCL03 or PA2200; Fig. 7a a voltage level of a received radar signal over different distances for a reference antenna, a lens antenna made of FLGPCL03 or PA2200. Description

[0048] Several embodiments will now be described in more detail with reference to the accompanying drawings, in which some embodiments are illustrated.

[0049] Although embodiments can be modified and altered in various ways, the embodiments shown in the figures are examples and are described in detail herein. It should be clarified, however, that the intention is not to limit embodiments to the forms disclosed, but rather to cover all functional and / or structural possibilities, equivalents, and alternatives within the scope of the invention.

[0050] A transceiver circuit for a radar signal can include a frequency multiplier that generates the radar signal from a fundamental signal with a fundamental frequency of an oscillator within the circuit. The frequency of the radar signal can be a multiple of the fundamental frequency. A lens antenna can be coupled to the transceiver circuit to focus the radar signal, which may be emitted by on-chip antennas or other antenna structures. It may be necessary to prevent the emission of unwanted frequency components of the radar signal, such as the oscillator's fundamental signal, as this can lead to mistargeting or problems with frequency approval and compliance with EMC regulations. Therefore, filter structures are commonly used.

[0051] Waveguides are known to be used, into which the radar signal is coupled. These waveguides, for example, adapt the radar signal as desired through their transmission characteristics (cut-off frequency). Additionally, conventional filter structures can be integrated into the waveguide. Furthermore, interference filter plates with different permittivities or suitable structures are known; these are placed in front of the on-chip antenna or the antenna structure used. Through interference, they filter out the unwanted frequency components. However, the aforementioned filter structures can be bulky, expensive, and difficult to align.

[0052] Therefore, the object of the present invention can be considered to be to provide an improved concept for filtering unwanted frequency components.

[0053] Fig. 1Figure 1 shows the cross-section of a conventional radar device 100, which generates and transmits a radar signal. The radar device 100 comprises an ellipsoidal, solid lens antenna 110, which is mounted on a circuit board 130 together with an FMCW radar transceiver 120. The lens antenna 110 is positioned in front of the FMCW radar transceiver 120, so that the lens antenna 110 and the circuit board 130 enclose the FMCW radar transceiver 120. The FMCW radar transceiver 120 comprises an open-cavity QFN package 122 (Quad Flat No Leads) and a SiGe transceiver MMIC 124 with two on-chip patch antennas 126, which is mounted on an inner surface of the QFN package 122.

[0054] A fundamental signal of the radar device 100 is generated, for example, by a voltage-controlled oscillator (not shown) with a fundamental frequency of 112 GHz (gigahertz). The fundamental signal can be split into two paths, each feeding a frequency multiplier, in this case a frequency doubler, for a TX and RX path, respectively. Since the output frequency of the radar signal can be up to 250 GHz, this may be too high to connect the corresponding paths via bond wires. Therefore, it may be necessary to integrate the two patch antennas 126 for transmitting and receiving the radar signal directly onto the chip 124. The lens antenna 110 can be used to focus the radar signal.

[0055] The PLL-stabilized modulation range (phase-locked loop) of the FMCW radar transceiver 120 can extend from 198 GHz to 250 GHz, resulting in an FMCW ramp bandwidth of 52 GHz – suitable for high-resolution radar measurements. Integrating RF components onto the SiGe transceiver MMIC 124 may necessitate connecting only low-frequency signal paths via bond wires. This allows the SiGe transceiver MMIC 124 to be installed in the QFN package 122, which is then mounted on the printed circuit board 130, for example, a standard FR-4 circuit board.

[0056] The 130 circuit board can include a front end with analog signal stabilization and an intermediate frequency (IF) circuit. The front end can be connected to a back end, which may include a reference crystal oscillator, a power supply circuit, and a microcontroller. The microcontroller is used for configuration, data processing, and data transmission. For this purpose, the microcontroller can transmit sampled IF data to a computer via a USB interface. The microcontroller can also be responsible for configuring PLL chips.

[0057] The radar device 100 can generate an output signal with a center frequency of 224 GHz by using a frequency doubler to double the fundamental signal of a voltage-controlled oscillator with a fundamental frequency of 112 GHz. This signal generation concept can suffer from parasitic crosstalk of the fundamental signal through the frequency doubler. In such cases, the fundamental signal can be radiated along with the desired, doubled output signal. This can result in a false target appearing at half the distance in the range spectrum for a genuine radar measurement, potentially leading to ambiguity in range determination. Since crosstalk cannot be completely suppressed at the chip level alone, for example, through improved frequency doubler topology and circuitry, an external filter structure can remedy the situation.

[0058] As in Fig. 2As shown, for example a dielectric filter plate 200 can be used. Fig. 2Figure 1 shows a cross-section of the filter plate 200. The transmission direction 210 indicates how a radar signal originating from a transceiver such as the radar device 100 propagates through the filter plate 200. Accordingly, the radar device 100 (not shown here) would be located, for example, to the left of the filter plate 200. The filter plate 200 has longitudinal slots 220. The depth of the longitudinal slots 220 can be such that, for a fundamental signal around a fundamental frequency, a phase difference of λ / 2 (180°) can be produced between components 230 of the fundamental signal that impinge on the longitudinal slots 220 and components 240 of the fundamental signal that impinge 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 the following equation 1. Equation 1: d = c 0 2 × f × ε r , 1 − ε r , 2 , where d is the depth, c 0 of the speed of light, f the fundamental frequency, ε r ,1 a permittivity of a material of increases and ε r ,2 correspond to a permittivity of a material longitudinal slots (e.g., air). With an output signal 250 of the radar device 100, which has a desired frequency approximately twice that of the fundamental frequency, passing through the longitudinal slots and elevations can cause a phase difference of λ (360°). Thus, corresponding components of the output signal 250 are in phase and superimpose constructively. Since 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. Furthermore, it may be necessary to align the filter plate 200 manually, which can increase implementation effort.

[0059] The present invention can therefore aim to offer an alternative to the concepts described above.

[0060] Fig. 3Figure 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 designed to focus electromagnetic waves with frequencies in the radio and / or terahertz range, similar to an optical lens for light. For this purpose, the lens antenna 300 can diffract the electromagnetic waves at a material interface within the interior of the lens antenna 300. For diffraction of the electromagnetic waves, the lens antenna 300 can consist at least partially of one or more dielectrics (such as resin, polymer, or Teflon) and / or one or more composite materials of at least one dielectric. The lens antenna 300 can be ellipsoidal in shape to enable the diffraction of the waves at the inner walls of the lens antenna 300 towards a focal point 330. The focal point 330 can be located within the interior of the lens antenna 300.The dielectrics and / or composite materials of the lens antenna 300 can exhibit different dielectric conductivities (permittivities) and refractive indices, which influence the propagation of electromagnetic waves within the lens antenna 300. The electromagnetic waves can be a signal from a transmitter system that radiates the electromagnetic waves as free-space waves via feed antennas. At least partially, the signal can propagate approximately spherically within the lens antenna 300, originating from a feed point 320. The feed point 320 can be located inside the lens antenna 300. The lens antenna 320 can also have multiple feed points, for example, 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 within the lens antenna 300 (for example, if the lens antenna 300 comprises different materials) and is focused from the focal point 330 of the lens antenna 300 and transmitted 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 transmitting and receiving antennas. The lens antenna 300 can therefore focus an outgoing signal from a transmitter system, an incoming signal from a receiver system, or both an outgoing and an incoming signal. For example, in the case of a transmitter / receiver system, it could be a transceiver circuit of a radar device, such as radar device 100.

[0061] The interference filter structure 310 can extend at least partially over a plane inside the lens antenna 300. The interference filter structure 310 can comprise material sections made of different dielectrics and / or composite materials. The interference filter structure 310 can be curved along an ellipsoidal surface around the feed point 320. The interference filter structure 310 can have different material sections along the ellipsoidal surface. The different material sections can be configured as different material thicknesses, that is, as elevations and depressions in one or more materials of the interference filter structure 310. Alternatively or additionally, the material sections can be configured, for example, as different dielectric layers along an axis 340 through the feed point 320 and focal point 330 of the lens antenna 300.The interference filter structure 310 can induce a phase delay in unwanted frequency components of the signal, so that a more phase-delayed part of the unwanted frequency components interferes destructively with a less phase-delayed part of the unwanted frequency components, thus attenuating the unwanted frequency components. For example, the different material sections, due to their varying permittivities, can cause the phase delay of at least some of the unwanted frequency components.

[0062] The interference filter structure 310 can be located closer to or further away from the feed point 320 than in Fig. 3The interference filter structure 310 can be arranged as shown. The distance between the interference filter structure 310 and the feed point 320 can be adjusted so that, on the one hand, the signal arrives at the interference filter structure 310 as close to the feed point 320 as possible in phase, and on the other hand, the interference filter structure 310 is easy to manufacture (i.e., at a certain distance from the feed point 320). The lens antenna 300 can be made of multiple parts to facilitate the integration of the interference filter structure 310 into the material of the lens antenna 300.

[0063] Fig. 4a and Fig. 4bFigure 1 shows 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, an upper part 410 and a lower part 420, to illustrate the interference filter structure 310a or 310b, which is formed integrally with part 420. The interference filter structures 310a and 310b extend along an ellipsoidal surface around a feed point of a radar signal. The feed point can be located, for example, on an on-chip antenna (not shown), such as on-chip antenna 126, or on a radar device, such as radar device 100. The feed point can be located on an axis 430 of the lens antenna 300. Assuming that wavefronts of the radar signal propagate approximately spherically from the feed point, the wavefronts can arrive at the interference filter structure 310a or 310b in phase.The ellipsoidal surface can therefore be approximately spherical. The in . Fig. 4a The interference filter structure 310a shown has (at least) three slot-shaped, "linear" depressions 440 on the ellipsoidal surface and (at least) three corresponding protrusions 450. The depressions 440 can extend along meridians on the ellipsoidal surface. The poles belonging to the meridians can be arranged outside the lens antenna 300, where (upon extension) the depressions 332a would converge. The depressions 440 can be mirror-symmetrical to a plane spanned by an axis 460 and an axis 430. In other embodiments, the interference filter structure 310a can comprise more or fewer depressions 440 and protrusions 450 than shown here. Fig. 4bThe interference filter structure 310b shown has three rotationally symmetric, annular ("circular") depressions 440 on the ellipsoidal surface about the axis 430 and four corresponding protrusions 450. 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. The depth of the depressions 440 can be calculated according to Equation 1 in order to induce destructive interference for an unwanted frequency component of the radar signal, similar to the filter plate 200, while leaving a desired frequency component virtually unchanged or constructively superimposing it.The width of the depressions 440 or elevations 450 can be determined, for example, by simulating the wave propagation of the radar signal for a specific shape of the lens antenna 300 and the interference filter structure 310, as well as for a wavelength of the unwanted frequency component. The lens antenna 300 can, for instance, replace the lens antenna 110 of the radar device 100. Subsequent 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 operates in frequency ranges other than those mentioned here.In other embodiments, the interference filter structure of the lens antenna 300 can have other shapes that follow the aforementioned 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, cancel out the unwanted frequency component by destructive interference.

[0064] While the conventional lens antenna 110 can be milled from a solid PTFE body, the lens antenna 300 with its integrated interference filter structures 310a, 310b may be too complex for a mechanical manufacturing process. Therefore, it may be advantageous to produce the interference filter structures 310a, 310b using additive manufacturing processes, such as stereolithography or selective laser sintering.

[0065] Additive manufacturing processes are a term used to describe manufacturing processes in which a workpiece is built up layer by layer. Unlike conventional manufacturing processes, where the workpiece is created by selectively removing material from a blank, additive manufacturing processes selectively add material. This allows for the production of highly complex shapes.

[0066] Stereolithography (SLA) uses a UV-light-sensitive liquid resin 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. This path is defined by slicer software. As soon as a laser beam from the UV laser strikes the liquid resin, it solidifies instantly. Once a layer of the workpiece is completely polymerized, it is removed from the liquid resin. After all layers of the workpiece have been completed, it is placed in a UV chamber to cure. Stresses occur during polymerization in the geometries of the workpiece that extend away from a base body, i.e., in overhanging components of the workpiece.To prevent stresses from causing deformations and crumbling in the solidified resin, support structures are used, which are removed in a post-processing step.

[0067] In Selective Laser Sintering (SLS), unlike SLA, a polymer powder is spread across a platform using a blade coater. An infrared heat lamp warms the powder to just below its melting point. A carbon dioxide laser fuses the powder particles by selectively heating them above their melting point. Each process step is completed by lowering the platform by one layer. The next process step then follows, and the cycle repeats until all layers of the workpiece have been built up. The finished workpiece is removed and cleaned of any remaining powder. SLS offers the advantage that the workpiece is embedded directly into the powder, eliminating the need for support structures for overhanging components.

[0068] These two additive manufacturing processes can be used to manufacture the lens antenna 300 with integrated interference filter structure 310a, 310b. First, the electromagnetic properties of the respective materials used in the additive manufacturing processes can be determined. For example, 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 comprises two waveguides and a flat test specimen made of the respective material. Corrugations on the inner walls of the waveguides can generate a plane wavefront, so that a coupled wave at the end of the waveguide covers the entire surface of the test specimen in phase. The test specimen can thus cover the entire aperture of the waveguide.The dielectric constant and dielectric loss of the test specimens can be determined from measured scattering parameters using a curve-fitting algorithm. The dielectric constant can be varied for a given sample thickness until the transmission and reflection curves match as closely as possible. Since the materials are non-magnetic, their permeability can be assumed to be 1. Standard materials such as clear resin "FLGPCL03" or "PA2200" (PA12) can be used for SLA and SLS. In other embodiments, the lens antenna 300 is manufactured from a material other than those listed here. The lens antenna 300 can also be made of Teflon and processed using conventional manufacturing methods to integrate the interference filter structure, such as interference filter structure 310a or 310b, into the lens antenna 300.

[0069] Fig. 5a and Fig. 5bshow dielectric properties of a test specimen made of FLGPCL03. Fig. 5c and Fig. 5d show dielectric properties of a test specimen made of PA2200. Fig. 5a and Fig. 5c They show a permittivity curve across the investigated frequencies and Fig. 5b and Fig. 5d The graphs show the loss factor over the investigated frequencies of the respective materials. For this purpose, a square test specimen measuring 40 x 40 x 4 mm (³ cubic millimeters) was printed using SLA and SLS processes, respectively, to extract the dielectric parameters of the specimens. Measurements of the dielectric parameters were performed in the V-band, as a measuring device for the Y-band was not available. For further analysis, values ​​for the dielectric parameters from the V-band measurements were also used in the Y-band.

[0070] Fig. 6a and Fig. 6bThis paper shows simulation results of a directivity factor over various radiation angles of an unwanted frequency component with a fundamental frequency of 112 GHz. The simulation results are presented for both embodiments of the lens antenna 300 described above, each with interference filter structures 310a and 310b made of PA2200 and FLGPCL03, respectively. For comparison, a conventional reference lens 610 or 620 without an interference filter structure, made of the respective material, is used. The reference lenses 610 and 620 can exhibit a simulated directivity factor of 31 dBi (decibels relative to an isotropic radiator) for both materials. The antenna efficiency, which is affected by material losses, was not considered in the directivity factor simulations.In the main beam direction, a significant decrease in directivity can be observed for both interference filter structures 310a and 310b, which may indicate good filtering performance. The SLS-printed PA2200 version of the lens antenna 300 can exhibit a simulated attenuation of approximately -33 dB for interference filter structure 310a and -30 dB for 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 attenuation of -32 dB for interference filter structure 310a and -21 dB for interference filter structure 310b can be achieved.

[0071] In the main beam direction (at 0°), interference filter structure 310a performs best in this example; however, larger sidelobes occur outside the main beam direction than with interference filter structure 310b. In this example, the directivity in the sidelobes for PA2200 is -5 dB for interference filter structure 310a and -15 dB for interference filter structure 310b, which is lower than the main lobe directivity of reference antenna 610. Similarly, in this example, the directivity in the sidelobes for FLGPCL03 is -5 dB for interference filter structure 310a and -12 dB for interference filter structure 310b, also lower than the main lobe directivity of reference antenna 620.

[0072] To validate the approach described above, radar measurements were performed using a fixed reflector as the target. The following describes the radar measurement, which is not intended to limit embodiments of the present invention to the specified values ​​for antenna length or losses. The reflector was placed 0.6 m (meters) in front of the radar transceiver 120. Fig. 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 ( Fig. 7a ), for the lens antenna 300 made of PA2200 with interference filter structure 310a and 310b ( Fig. 7b ) or for the lens antenna 300 made of FLGPCL03 with interference filter structure 310a and 310b ( Fig. 7c ). As in Fig. 7aAs shown, in measurements with the PTFE reference antenna, the false target 710 appears at half the distance of 0.3 m. Multiple reflections 720 within the reference antenna appear as peaks behind the true target 730 and in the immediate vicinity. Fig. 7b and Fig. 7cIn measurements with the two embodiments 310a and 310b of the lens antenna 300, no false target 710 appears at half the distance, meaning it was successfully filtered out. The amplitude of the target peak 730 is significantly lower, which can be attributed primarily to dielectric losses in the material. The geometric length of the reference antenna can be 41 mm. The 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 during radar operation, where the radar signal must pass through the respective antenna twice, 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 version of the lens antenna 300.Within the lens material, additional dielectric losses of -7 dB for interference filter structure 310a and -14 dB for interference filter structure 310b can occur due to the PA2200 version. The additional losses can be -11 dB for interference filter structure 310a and -12 dB for interference filter structure 310b in the FLGPCL03 version. The losses for interference filter structure 310b are slightly higher than those for interference filter structure 310a in this example. This may be due to a manufacturing process, since the lens antenna 300 with interference filter structure 310a can be printed in one piece, whereas for the lens antenna 300 with interference filter structure 310b it may be necessary to print it in two parts (310, 320) in order to remove unprocessed powder from the recesses 332b.In this case, the unprocessed powder could otherwise be trapped inside the lens antenna 300 during a single-piece printing process. The two parts 310 and 320 can then be assembled, which can create a small air gap between them, causing further losses.

[0073] Depending on the signal generation concept, modern radar sensors can suffer from crosstalk of the fundamental signal at a fundamental frequency. This can lead to false targets in the range spectrum and thus to 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, enabling reliable and robust measurements in industrial measurement applications. Two exemplary embodiments of the interference filter structure were demonstrated. When selecting the interference filter structure, it may be necessary to find a compromise between passband rejection and sidelobe amplitude. Furthermore, it was proposed to print the demonstrated interference filter structures using additive manufacturing processes.The measurements described showed that polyamide may be the better choice for SLS printing with regard to dielectric losses compared to the photopolymer resin of SLA printing, while the latter may be the more affordable choice.

[0074] 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 an identical feature of the other example or to additionally introduce the feature into the other example.

[0075] The following claims are hereby included in the detailed description, each claim being a separate example. It should also be noted that—although a dependent claim may refer to a specific combination with one or more other claims—other examples may 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 a specific case that a particular combination is not intended. Furthermore, features of a claim are also to be included for each other independent claim, even if that claim is not directly defined as dependent on that other independent claim.

Claims

1. A lens antenna (300) comprising an interference filter structure (310) integrated into a lens of the lens antenna (300), wherein the interference filter structure (310) extends along an ellipsoidal surface around a feed point (320) for the lens antenna (300), and wherein the interference filter structure (310) comprises material portions of different permittivity along the ellipsoidal surface.

2. The lens antenna (300) of claim 1, wherein first material portions of the interference filter structure (310) comprise a first dielectric and second material portions of the interference filter structure (310) comprise a second dielectric.

3. The lens antenna (300) of one of the preceding claims, wherein the interference filter structure (310) comprises elevations (450) and fluid-filled depressions (440) in a material of the lens antenna (300).

4. The lens antenna (300) of one of the preceding claims, wherein the interference filter structure (310) comprises elevations (450) spaced apart on the ellipsoidal surface.

5. The lens antenna (300) of claim 4, wherein the elevations (450) are at least partially annular.

6. The lens antenna (300) of claim 4 or 5, wherein the elevations (450) are rotationally symmetrical about a major axis of the ellipsoid of the ellipsoidal surface.

7. The lens antenna (300) of claim 4 or 5, wherein the elevations (450) are mirror-symmetrical with respect to a plane formed by two major axes of the ellipsoid of the ellipsoidal surface.

8. The lens antenna (300) of one of the preceding claims, wherein the interference filter structure (310) is configured to attenuate an undesired frequency component of a signal in the radio and / or terahertz range.

9. The lens antenna (300) of one of the preceding claims, further comprising a first part (420) and a second part (410) removable from the first part (420), wherein the interference filter structure (310) is integrally formed with the first part (420) and is enclosed by the first and second parts (410, 420) in an assembled state.

10. An apparatus for radar measurements comprising a transceiver circuit (124) for a radar signal, wherein the transceiver circuit (124) comprises a frequency multiplier configured to generate a center frequency of the radar signal from a fundamental frequency, a lens antenna (300) according to one of the preceding claims coupled to the transceiver circuit (124), wherein the interference filter structure (310) is configured to attenuate signal components of the radar signal around the fundamental frequency.

11. A method for manufacturing a lens antenna (300) comprising molding an interference filter structure (310) into a lens of the lens antenna (300), wherein the interference filter structure (310) extends along an ellipsoidal surface around a feed point (320) for the lens antenna (300), and wherein the interference filter structure (310) comprises material portions of different permittivity along the ellipsoidal surface.