Noise reduction device for electromagnetic measuring systems, radar measuring systems and its use

Abstract

Noise reduction device for a measuring system operating by means of electromagnetic waves, which has the form of a hollow cylinder (1) open at both ends and comprising a wall, wherein the wall of the hollow cylinder (1) includes an open-pore foam, characterized in that the open-pore foam consists of a non-metallic material having a surface coating of a metal.

Description

[0001] The invention relates to a device that enables an increase in the signal-to-noise ratio in measuring systems that operate using electromagnetic waves, preferably in the radio wave range. Furthermore, the invention relates to a radar measuring system with such a noise suppression device and a use thereof.

[0002] Measurement and detection methods using electromagnetic waves have the advantage that, by appropriately determining the wavelength of the electromagnetic waves used, the objects to be detected or examined can be visualized under a wide variety of conditions. For example, if visibility is obstructed by vapors in the visible wavelength range, switching to low-frequency waves allows penetration of the vapors.

[0003] The detection of (metallic) objects using radar waves, i.e., electromagnetic waves in the radio range, is well known in both civilian and military applications. These systems emit radio waves and detect the radio waves reflected by the objects. The resolution of the image captured in this way is limited—not least due to the significantly longer wavelength of radio waves compared to light waves—so that details of the objects detected by radio waves are barely or not at all visible, especially at greater measurement distances.

[0004] The power of the emitted radio waves also influences the signal-to-noise ratio and thus the maximum possible resolution. The trend toward ever-increasing miniaturization of radio wave emitters inevitably leads to reduced emission power and thus to a deteriorated resolution or a reduced signal-to-noise ratio.

[0005] DE 10 2012 202 913 A1 discloses a radar sensor with a radar antenna, a radar lens, and a funnel element between the radar antenna and the radar lens. The funnel element comprises a material that absorbs radar radiation emitted by the radar antenna.

[0006] DE 10 2004 012 563 A1 describes a multispectral camouflage agent based on a temperature-controlled heat exchanger, in which the heat transfer medium is gaseous and simultaneously a signature carrier in the visible light, near infrared, and thermal infrared spectral ranges. Furthermore, the same element also reduces the reflection of high-frequency radar radiation across a broad spectrum.

[0007] DE 10 2017 213 001 A1 discloses a method and a control unit for controlling a joining station. The control unit is configured to determine actual data regarding a first joining element joined by the joining station to a current workpiece based on sensor data from one or more sensors, for example, from a radar scanner.

[0008] The invention is based on the object of avoiding the above-mentioned disadvantages, such as poor resolution of the images of objects detected by means of long-wave electromagnetic waves, in particular when using radio wave emitters with low transmission power, whereby a compact noise suppression device for measuring systems which operate on the basis of electromagnetic waves should be realizable, which enables an increase in the signal-to-noise ratio and the spatial resolution during a measurement without the need for electronic components.

[0009] This object is achieved by a noise suppression device having the characterizing features of claim 1; expedient embodiments of the invention are found in the subclaims. A particularly advantageous use of the invention is set forth in claim 8.

[0010] According to the invention, a noise suppression device for a measuring system emitting electromagnetic waves and detecting the reflected signal thereof is provided, which essentially has the shape of a hollow cylinder open on both sides.

[0011] The term "hollow cylinder open on both sides" refers to any shaped body with a centrally located through-opening. The base of the hollow cylinder can have any shape, but is preferably rectangular or oval (including circular).

[0012] Likewise, the cross-sectional area of ​​the cavity enclosed by the wall of the hollow cylinder can have any shape, whereby the shape of the cavity cross-sectional area can also be variable in the direction along the longitudinal axis of the hollow cylinder.

[0013] The wall of the hollow cylinder comprises an open-pore foam that is metallic at least on its surface. According to the invention, the open-pore foam consists of a non-metallic material, e.g., polyurethane (PU), coated with a metal.

[0014] It has been shown that such a hollow foam cylinder, when placed in front of the emitter or receiver of a radar measurement system, can significantly increase the signal-to-noise ratio and improve the resolution of the image acquired by the radar measurement system by orders of magnitude.

[0015] The advantage of this designed noise suppression device is its simple construction, its compact size and the absence of error-prone electronic components that require an additional power supply.

[0016] The invention can be further designed such that the noise suppression device, ie the hollow cylinder, consists entirely of an open-pore foam.

[0017] In particular, it can be provided that the hollow cylinder is constructed in layers, i.e., the wall of the hollow cylinder comprises a plurality of sections made of an open-pore foam. The sections are preferably in the form of a plate, with the sections arranged along the longitudinal axis of the hollow cylinder. The pores of one or more of these sections can also have a different pore size than the other sections.

[0018] Additionally, the open-pore foam can be provided with a gradation, i.e., the size of the pores in one or more of the sections varies progressively from a minimum value to a maximum value. This variation can be formed along the hollow cylinder's longitudinal axis or radially relative to the hollow cylinder's longitudinal axis.

[0019] Alternatively, the wall of the hollow cylinder can have a uniform gradation along the entire height of the hollow cylinder, i.e., a continuously increasing or decreasing pore size of its open-pore foam. This uniform gradation can be formed either along or across, i.e., radially, the longitudinal axis of the hollow cylinder.

[0020] According to one embodiment, the cavity enclosed by the wall of the hollow cylinder has the geometric shape of a truncated cone or pyramid. The hollow cylinder can have the same shape, i.e., it is conical.

[0021] Furthermore, a radar measuring system is provided, in front of whose radio wave emitter or receiver a noise suppression device with the above-mentioned features is arranged in such a way that the radio waves emitted or to be detected pass through the cavity from the radio wave emitter or to the radio wave receiver.

[0022] In particular, the radar measuring system can be designed in the form of a (semiconductor) chip whose area does not exceed 100 square centimeters.

[0023] Such a radar measurement system can be used for joining workpieces or for repairing steel structures using welding. The radar measurement system allows for the detection of edges of the workpieces or the gap to be welded, the determination of the size and / or position of the gap, and the detection of the positioning and alignment of the workpieces to be joined in space and relative to each other. Since fumes often develop during welding, the radar measurement system enables reliable detection of the aforementioned parameters through the fumes. It can also be used for underwater welding when visual inspection is impeded by murky water or steam formation.

[0024] The invention will be explained in more detail below using an exemplary embodiment, wherein identical or similar features are provided with the same reference numerals. In this connection, the Fig. 1 shows a noise suppression device according to a first embodiment in a perspective view; Fig. 2 shows a noise suppression device according to a second embodiment in a perspective view; and Fig. 3 a radar measuring system with noise suppression device in perspective view.

[0025] The noise reduction device according to Fig. 1 is designed as a hollow cylinder 1 open on both sides with a square base, with the cavity opening cross-section 2 of the hollow cylinder 1 being circular. The noise suppression device is a one-piece construction, although it is not entirely made of an open-pore metal foam according to the invention.

[0026] Fig. Figure 2 shows a noise suppression device whose hollow cylinder 1 has a circular top surface. Transverse to the longitudinal axis 3 of the hollow cylinder 1, the cylinder is divided into three sections 4, each with a different pore size. Along the longitudinal axis 3 of the hollow cylinder 1, the pore size increases from bottom to top in the figure. According to the invention, the wall of the hollow cylinder 1, or rather the individual sections 4, consists entirely of a metal-coated, open-pore PU foam.

[0027] On chip 5 of the Fig. 3, a noise suppression device with a conical hollow cylinder 1 is arranged, wherein the shape of the cavity enclosed by the wall of the hollow cylinder 1 corresponds to an (upside down) truncated cone. List of reference symbols used 1 hollow cylinder 2 Opening cross-section of the cavity 3 Longitudinal axis of the hollow cylinder 4 Section 5 radar measurement system chip

Claims

[1] Noise suppression device for a measuring system operating by means of electromagnetic waves, which has the shape of a hollow cylinder (1) open on both sides and comprising a wall, wherein the wall of the hollow cylinder (1) contains an open-pore foam, characterized by that the open-pore foam consists of a non-metallic material which has a surface coating of a metal. [2] Noise suppression device according to claim 1, characterized in that the wall of the hollow cylinder (1) consists entirely of an open-pore foam. [3] Noise suppression device according to claim 1, characterized in that the wall of the hollow cylinder (1) has a plurality of sections (4) made of an open-pore foam, wherein the pore size of each section (4) is different from the pore sizes of the other sections (4). [4] Noise suppression device according to claim 1, characterized in that the open-pore foam has a gradation along the cylinder axis of the hollow cylinder (1). [5] Noise suppression device according to claim 1, characterized in that the open-pore foam has a graduation in the radial direction with respect to the hollow cylinder (1). [6] Noise suppression device according to claim 1, characterized in that the cavity enclosed by the wall of the hollow cylinder (1) has a cross-sectional area which is variable in the longitudinal direction of the hollow cylinder (1). [7] Radar measuring system, characterized in that it comprises a noise suppression device according to one of claims 1 to 6, the hollow cylinder longitudinal axis (3) of which is aligned parallel to the radio waves emitted by a radar wave emitter of the radar measuring system. [8] Use of the radar measuring system according to claim 7 in the joining of workpieces for edge detection of the workpieces and / or for determining a gap between the workpieces and / or for determining the position of the workpieces.

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