IL282938A

IL282938A - Antenna-based radio detection systems and methods

Info

Publication number: IL282938A
Application number: IL282938A
Authority: IL
Inventors: Shachar Aviv-Zion; Norbashan Moshe; Nahman Boaz
Original assignee: Elbit Systems Ew And Sigint Elisra Ltd; Aviv Zion Shachar; Norbashan Moshe; Nahman Boaz
Priority date: 2021-05-04
Filing date: 2021-05-04
Publication date: 2022-12-01
Also published as: IL282938B2; WO2022234426A1

Description

TECHNICAL FIELD id="p-1" id="p-1" id="p-1" id="p-1"

[0001] This present disclosure is generally related to antenna-based radio detection systems.

BACKGROUND id="p-2" id="p-2" id="p-2" id="p-2"

[0002] Radio detection systems such as RADAR (Radio Detection and Ranging) uses radio waves (either pulsed or continuous) to determine various parameters such as a range, angle, velocity, etc. of objects in a scene, and may be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, terrain topography, etc.

Radio detection system may comprise a transmitter configured to produce electromagnetic radiation (EMR), a transmitter antenna, a receiver antenna configured to receive EMR reflected from a scene and a receiver configured to produce EMR signals based on said reflections. id="p-3" id="p-3" id="p-3" id="p-3"

[0003] The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.

BRIEF DESCRIPTION OF THE FIGURES id="p-4" id="p-4" id="p-4" id="p-4"

[0004] The figures illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. id="p-5" id="p-5" id="p-5" id="p-5"

[0005] For simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity of presentation. Furthermore, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. References to previously presented elements are implied without necessarily further citing the drawing or description in which they appear. The figures are listed below. id="p-6" id="p-6" id="p-6" id="p-6"

[0006] FIG. 1 represents a schematic illustration of an antenna-based radio detection system, according to some embodiments. 1 according to some embodiments. id="p-8" id="p-8" id="p-8" id="p-8"

[0008] FIG. 2B is another schematic view of the antenna-based radio detection system of FIG. 2B, according to some embodiments. id="p-9" id="p-9" id="p-9" id="p-9"

[0009] FIGs. 3A-3D are schematic illustrations of electromagnetic radiation (EMR) absorbing elements of antenna-based radiation detection systems, according to some embodiments. id="p-10" id="p-10" id="p-10" id="p-10"

[0010] FIG. 4A is a schematic view of an antenna-based radiation detection system, according to some other embodiments. id="p-11" id="p-11" id="p-11" id="p-11"

[0011] FIG. 4B is a schematic illustration of a radiation pattern of electromagnetic radiation between two adjacent EMR absorbing elements, according to some embodiments. id="p-12" id="p-12" id="p-12" id="p-12"

[0012] FIGs. 5A-D schematically show EMR absorbing structures and, in overlay, the equivalent electrical circuits. id="p-13" id="p-13" id="p-13" id="p-13"

[0013] FIGs. 6A-B are photographs of an antenna-based radio detection system, according to some embodiments. id="p-14" id="p-14" id="p-14" id="p-14"

[0014] FIG. 7A shows geometric parameters of rectangular absorption elements of an antenna-based radiation detection system, according to some embodiments. id="p-15" id="p-15" id="p-15" id="p-15"

[0015] FIG. 7B graphically illustrates surface current isolation properties for various rectangular absorption elements having different geometric parameters, according to corresponding embodiments. id="p-16" id="p-16" id="p-16" id="p-16"

[0016] FIG. 8 shows a schematic heat-map simulation to depict the effect of T-shaped EMR absorption elements on electromagnetic attenuation from a transmitter to a receiver side of an antenna-based radio detection system, according to some embodiments. id="p-17" id="p-17" id="p-17" id="p-17"

[0017] FIG. 9 shows a graph of S-parameters measured during operation of an antenna-based radio detection system, according to some embodiments. id="p-18" id="p-18" id="p-18" id="p-18"

[0018] FIGs. 10A-B shows various schematic views of an antenna array of an antenna- based radio detection system, according to some embodiments. 2 cover 2000 on an antenna-based radio detection system, according to some embodiments. id="p-20" id="p-20" id="p-20" id="p-20"

[0020] FIG. 12 shows a flowchart of a method of detecting objects in a scene using an antenna-based radio detection system.

DETAILED DESCRIPTION id="p-21" id="p-21" id="p-21" id="p-21"

[0021] Aspects of embodiments pertain to antenna-based radio detection systems comprising a transmitter (Tx) antenna and a receiver (Rx) antenna. The transmitter antenna is configured to radiate or emit into free space electromagnetic radiation (EMR) towards a scene, and the Rx antenna is configured to receive EMR reflected by objects that may be present in the scene to produce a reflection-based signal. The reflection- based signal may be processed, for example, to detect the presence of objects in the scene and, for instance, to identify the type of object detected. Such object may be an airborne vehicle (e.g., a drone, an aircraft). In some examples, based on characteristics of the transmitted and the reflected signals, the system may determine a distance estimate between the radar system and a detected object. In some examples, the antenna-based radio detection system may be a RADAR system such as a Frequency- Modulated Continuous Wave FMCW RADAR system. The antenna-based radio detection system, according to some embodiments, may be configured to be mountable on a variety of mobile or stationary platforms. id="p-22" id="p-22" id="p-22" id="p-22"

[0022] One of the many factors that may have a significant effect on the performance characteristics of antenna-based radio detection systems is related to the extent at which a receiver (also: Rx) antenna may be exposed to or may pick up surface currents generated as result of the emission of EMR by the transmitter antenna employed by such systems. id="p-23" id="p-23" id="p-23" id="p-23"

[0023] Exposure to such surface currents operably interferes with the performance characteristics of the antenna-based radiation detection system. For example, increased exposure may reduce the signal-to-noise ratio (SNR) at the receiver antenna. 3 currents that may otherwise be generated between transmitter and receiver antennas. id="p-25" id="p-25" id="p-25" id="p-25"

[0025] Embodiments relate to enhancing performance characteristics of antenna- based radio detection systems by disposing an electromagnetic radiation (EMR) absorbing structure between a transmitter and a receiver antenna. The EMR absorbing structure can include frequency-selective surfaces (FSS), corrugated structures, uneven structures, and/or surfaces exhibiting periodic, non-periodic, pseud-periodic and/or fractal structures. id="p-26" id="p-26" id="p-26" id="p-26"

[0026] In some examples, the transmitter and receiver antennas may be disposed or arranged on a common platform or base of the antenna-based radio detection system.

In some examples, the base may comprise or constitute the EMR absorbing structure to reduce or prevent from surface currents reaching the receiver antenna, to enhance one or more performance characteristics of the radiation-based detection system such as, for example, SNR, e.g., due to noise suppression. id="p-27" id="p-27" id="p-27" id="p-27"

[0027] According to some embodiments, the antenna-based radio detection system is configured to produce high bandwidth signals. For example, the antenna-based radio detection system may be configured to operate in a frequency band ranging, for example, from a 5 GHz band to 24 GHz band. In some examples, the EMR isolation structure may be configured to provide enhanced isolation performances across a comparatively wide frequency band (e.g., tens of Gigahertz). In some configurations of the EMR isolation structure, a median, average or maximum reduction of, for example, at least 30 dB may be achieved, for example, of emitted RF signals ranging from, for example, 8 GHz to 11 GHz, thereby obtaining a corresponding reduction in unwanted surface currents. id="p-28" id="p-28" id="p-28" id="p-28"

[0028] Although some examples disclosed herein pertain to X-band applications, this should by no means be construed in a limiting manner. Accordingly, the same principles that are exemplified herein may also be applicable to additional radio ranges including, for example, 1 GHz or higher frequencies. id="p-29" id="p-29" id="p-29" id="p-29"

[0029] In some other examples, the EMR absorbing structure may be configured to act as notch-filter or band stop filter. 4 between the Tx & Rx antennas, may be tuned to isolate (e.g., reduce or eliminate exposure of the Rx antenna) surface currents with respect to a specific detection system operating band range. In some examples, the EMR absorbing structure may provide approximately, at least, 30 dB isolation between the transmitter and receiver antenna for a comparatively broad frequency band (e.g., 5GHz to 24 GHz). id="p-31" id="p-31" id="p-31" id="p-31"

[0031] In some embodiments, the antenna-based radio detection system may be configured to emit EMR towards the scene while, at the same time, receive EMR to produce reflection-based signals. In some examples, no blanking periods may be employed during the emission and receiving of EMR by the radiation detection system. id="p-32" id="p-32" id="p-32" id="p-32"

[0032] A pair of Rx & Tx antennas of the radio detection system may be in a fixed configuration relative to each other. id="p-33" id="p-33" id="p-33" id="p-33"

[0033] In some embodiments, the receiver antenna is spaced apart from the transmitter antenna by the EMR absorbing structure by a distance D. The EMR absorbing structure may comprise or consist of any suitable EMR absorbing material. For example, the EMR absorbing structure may comprise conductive metals (e.g., copper, brass, nickel, steel). The EMR absorbing structure may be configured as a sheet metal, conductive, and/or the like. According to some embodiments, the EMR absorbing structure is configured to isolate (choke) the receiver antenna from/against surface currents that may be generated at the transmitter side of the Radio detection system, e.g., due to EMR induction. id="p-34" id="p-34" id="p-34" id="p-34"

[0034] According to some embodiments, by employing the EMR absorbing structure, the distance D between the transmitter antenna and the receiver antenna in a radiation detection system according to some embodiments may be reduced by several orders of magnitudes (e.g., at least tenfold) without compromising a performance characteristic (e.g., SNR), compared to a distance between a transmitter and receiver radio of a radio detection system that does not employ an EMR absorbing structure. In embodiments the radio detection system, one or more performance characteristics may be improved even for shorter distances D. characteristics of embodiments of radio detection systems comprising an EMR absorbing structure, are made in relation to radio detection systems that do not employ an EMR absorbing structure. id="p-36" id="p-36" id="p-36" id="p-36"

[0036] The EMR absorbing structure may comprise a plurality of EMR absorbing elements. In some examples, the plurality of EMR absorbing elements may be directly coupled to the common conductive ground or base plate. For example, the device may be configured to lack an intermediate structure (e.g., dielectric or conductive) between the plurality of EMR absorbing elements may and the common conductive ground or base plate. In some embodiments, at least one or all of the plurality of EMR absorbing elements may be integrally formed with the common conductive ground. In some embodiments, at least one or all of the EMR absorbing elements may be made of solid material, i.e., may be free of any macroscopic cavity. In some examples, each two neighboring EMR absorbing elements are spaced apart from each other, and longitudinally (and, e.g., continuously) extend in a direction X over a length exceeding the X-dimensions of the at least one transmitter antenna and the at least one receiver antenna. In some examples, all EMR absorbing elements of th EMR absorbing structure may be arranged in a same plane and directly coupled to the same single conductive common ground. Upper surfaces of two neighboring EMR absorbing elements are arranged to form a dielectric gap therebetween. id="p-37" id="p-37" id="p-37" id="p-37"

[0037] According to some embodiments, Tx-Rx isolation can be improved through design optimization of, for example, one or more of the following parameters of the EMR absorbing structure: a pitch length (also: the sum of the line-width of the EMR absorbing element and one neighboring ridge width), the geometry of the cross-section of a EMR absorbing element; groove depth H between neighboring EMR absorbing elements and/or an orientation of an EMR absorbing element relative to the transmitter and/or the receiver antenna, etc. In some examples, the EMR absorbing structure may have periodical and/or non-periodical design structures. id="p-38" id="p-38" id="p-38" id="p-38"

[0038] The EMR absorbing structure and/or the EMR absorbing elements may be manufactured, for example, by employing 2D or 3D material contouring techniques (e.g., 6 suitable manufacturing technique. id="p-39" id="p-39" id="p-39" id="p-39"

[0039] In some embodiments, the EMR absorbing elements may be arranged to form the EMR absorbing structure having a plurality of ridges and grooves extending from the transmitter side (also: a first location of the transmitter antenna) to the receiver side (also: second location of the receiver antenna). id="p-40" id="p-40" id="p-40" id="p-40"

[0040] An orientation of the plurality of EMR absorbing elements may be perpendicular with respect to a longitudinal axis of the radio detection system extending from the transmitter to the receiver antenna, and further perpendicular with respect to a direction of free space emission of EMR radiation towards the scene. id="p-41" id="p-41" id="p-41" id="p-41"

[0041] In some examples, the EMR absorbing elements may be arranged in a coplanar manner (also: substantially coplanar) with respect to a straight or substantially straight surface. In some examples, EMR absorbing elements may be coplanar with the transmitter and the receiver antenna. id="p-42" id="p-42" id="p-42" id="p-42"

[0042] The elements of the EMR absorbing structure may have various geometric configurations. For instance, a plurality of EMR absorbing elements may be arranged to form ridges of varying depths H and/or protrusions of varying heights relative to a reference base plane. According to some embodiments, the depths H and/or widths W of a plurality of recesses formed by at least three EMR absorbing elements may be uniform or vary relative to each other. In some examples, a plurality of ridges may be coplanar relative to each other, yet neighboring ridges may have different depths. In a further example, a plurality of ridges may lie on different planes, yet may have same depths H. For instance, a plurality of EMR absorbing elements may be arranged in a staggered (e.g., alternating) manner relative to each other such that some ridges or protrusion extend beyond a reference plane and some not. In further examples, a plurality of EMR absorbing elements may be designed such at least two ridges are coplanar, at least two other ridges are lie on different planes, at least two grooves have same depths H, and at least two grooves have different depths H. In some examples, the depth or height H of an indentation or recess may be greater than a width W between adjacent ridges. In some examples, the depth H of an indentation or recess may be smaller than a width W between adjacent ridges. In some further examples, the depth H 7 recess. id="p-43" id="p-43" id="p-43" id="p-43"

[0043] In some examples, an EMR absorbing element may have a rectangular cross- section. In some examples, an EMR absorbing element may have a triangular cross- section. In some embodiments, the body of an EMR absorbing element may widen in EMR transmission direction. id="p-44" id="p-44" id="p-44" id="p-44"

[0044] According to some embodiments, an indentation or recess between adjacent ridges of the EMR absorbing structure may have height H in accordance with the EMR wavelength band that is to be attenuated for Rx isolation purposes. For example, a largest recess dimension of the EMR absorbing structure may have a height H that is about 1/4 of the wavelength (or multiplied by a positive integer factor) of the center frequency of the EMR radiated by the transmitter antenna to choke surface currents through destructive interference of EMR being reflected between the adjacent conductive surfaces forming a recess between adjacent EMR absorbing elements.

Optionally, adjacent EMR absorbing elements may form a recess having decreasing or increasing width W in direction of the free space EMR emission (Z-direction), to obtain a corresponding choking frequency bandwidth. id="p-45" id="p-45" id="p-45" id="p-45"

[0045] For instance, for a system adapted to transmit between about 5.4 and about 6.2 GHz, the heights H of the recesses in the EMR absorbing structure may for example range from about 13.89 mm to about 12.1 mm. id="p-46" id="p-46" id="p-46" id="p-46"

[0046] In a further example, in a radio detection system that may be adapted to operate at between about 4 GHz and about 8 GHz, recesses formed by the EMR absorbing elements may range, for example, from about 18.8 mm to about 9.4 mm. id="p-47" id="p-47" id="p-47" id="p-47"

[0047] The term "EMR absorbing structure", as used herein, refers to any conductive/semi-conductive structure formed by a plurality of EMR absorbing elements and configured to reduce or prevent from induced surface currents to reach the receiver antenna to reduce or prevent interference or the proper operation of an antenna-based radio detection system. id="p-48" id="p-48" id="p-48" id="p-48"

[0048] The term "uneven", as used herein, refers to a structure having an irregular of non-uniform surface in any shape of form. 8 or non-periodical ridges and recesses that may protrude/be sunken in any desirable direction. id="p-50" id="p-50" id="p-50" id="p-50"

[0050] The term "Signal-to-noise ratio (SNR or S/N)", as used herein, refers to a measure that compares the level of a desired signal to the level of background noise.

SNR is defined as the ratio of signal power to a noise power, often expressed in decibels wherein a ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. id="p-51" id="p-51" id="p-51" id="p-51"

[0051] The term "fractal structure", as used herein, refers to any of various and extremely irregular curves or shapes, for which any suitably chosen part is similar in shape to a given larger or smaller part, when magnified or reduced to the same size. id="p-52" id="p-52" id="p-52" id="p-52"

[0052] The term "FMCW", as used herein, refers to a Frequency- Modulated Continuous-Wave Radar, which is a type of radar system where a known, stable frequency and continuous radio transmission is transmitted and then received from any reflecting object in a scene. For example, objects may be detected using a Doppler effect, which causes the received signal to have a different frequency from the transmitted signal, allowing it to be detected by filtering out the transmitted frequency. id="p-53" id="p-53" id="p-53" id="p-53"

[0053] The following description of the display devices, systems and methods is given with reference to particular examples, with the understanding that such devices, systems and methods are not limited to these examples. id="p-54" id="p-54" id="p-54" id="p-54"

[0054] Reference is now made to FIG. 1 . An antenna-based radio detection system 1000 comprises a first antenna array 1100 and a second antenna array 1200. For the purpose of the present discussion, first antenna array 1100 is herein referred to as "transmitter antenna" 1100, and second antenna array 1200 is herein referred to as "receiver antenna" 1200. Transmitter antenna 1100 is configured to emit EMR into free space towards a scene 500, as schematically illustrated by arrow EMR , in Z-direction T and, as schematically illustrated by arrow EM , receive reflected electromagnetic R radiation EMR from scene 500 to produce processable reflection-based signals for R analysis purposes. For example, the reflection-based signals may be processed to detect the presence of one or more objects 510 (e.g., objects 510A and 510B) in scene 500 and, 9 (e.g., a drone, an aircraft) and/or a terrestrial object. id="p-55" id="p-55" id="p-55" id="p-55"

[0055] Transmitter antenna 1100 may be arranged at a first location, and receiver antenna 1200 may be arranged at a second location, spatially separated from the first location by a distance D and configured to pick up electromagnetic radiation EMR R reflected from scene 500. According to some embodiments, the at least one transmitter antenna 1100 may be is spatially separated from at least one receiver antenna 1200 at a distance D not exceeding 190 mm, 180 mm, 170 mm, 160 mm, or 150 mm. In some examples, the distance D may be 190 mm or less, 180 mm or less, 170 mm or less, 160 mm or less, 150 mm or less, 140 mm or less, 130 mm or less, 120 mm or less, 110 mm or less, or 100 mm or less. id="p-56" id="p-56" id="p-56" id="p-56"

[0056] In some embodiments, transmit antenna 1100 and receive antenna 1200 may be mounted on or accommodated by a common base 1300 (e.g., a common base plate). id="p-57" id="p-57" id="p-57" id="p-57"

[0057] According to some embodiments, base 1300 may be a rigid or a semi-rigid plate configured to provide a platform for the various components forming the antenna- based radio detection system 1000. id="p-58" id="p-58" id="p-58" id="p-58"

[0058] According to some embodiments, EMR absorbing structure 1400 may be embedded as part of the base 1300. For example, a section of base 1300 may be formed by a plurality of EMR absorbing elements 1500. id="p-59" id="p-59" id="p-59" id="p-59"

[0059] According to some embodiments, the EMR absorbing structure 1400 embedded as part of the base 1300 is configured to reduce the induction of surface currents between transmitter antenna 1100 and the receiver antenna 1200. id="p-60" id="p-60" id="p-60" id="p-60"

[0060] In some embodiments, transmit antenna 1100 and receive antenna 1200 may be mounted on or accommodated by different bases (not shown). The different bases may be configured to be coupleable with each other. id="p-61" id="p-61" id="p-61" id="p-61"

[0061] According to some embodiments, the various components forming the antenna-based radio detection system 1000 are available as assembly components, for example, pre-manufactured parts available for purchase and assembly to form various systems. According to some embodiments, the term assembly components may also to form an antenna-based radio detection system. id="p-62" id="p-62" id="p-62" id="p-62"

[0062] According to some embodiments, upon operation of the antenna-based radio detection system 1000, transmitter antenna 1100 (e.g., continuously) transmits electromagnetic radiation, and receiver antenna 1200 (e.g., continuously) receives electromagnetic radiation reflections to generate reflection-based signals. id="p-63" id="p-63" id="p-63" id="p-63"

[0063] According to some embodiments, the antenna-based radio detection system 1000 may be a Frequency-Modulated Continuous Wave (FMCW) radar. id="p-64" id="p-64" id="p-64" id="p-64"

[0064] In some examples, transmit antenna 1100 may have a fixed field-of-view (FOV) relative to scene 500. In some other examples, transmit antenna 1100 may scan a plurality of different scene FOVs. In some examples, transmit antenna 1100 may adapt (narrow or widen) its FOV. id="p-65" id="p-65" id="p-65" id="p-65"

[0065] According to some embodiments, an EMR absorbing structure 1400 is disposed between transmitter antenna 1100 and receiver antenna 1200. EMR absorbing structure 1400 extends in a first direction along longitudinal axis Y of the radar system, from the first location of transmitter antenna 1100 to the second location of receiver antenna 1200. id="p-66" id="p-66" id="p-66" id="p-66"

[0066] EMR absorbing structure 1400 may be configured to reduce the amount of unwanted electromagnetic radiation propagating from transmitter antenna 1100 to the receiver antenna 1200 to reduce or prevent from unwanted surface currents Is, induced by the unwanted electromagnetic radiation, to reach receiver antenna 1200. id="p-67" id="p-67" id="p-67" id="p-67"

[0067] EMR absorbing structure 1400 may be formed by a plurality of EMR absorbing elements, as exemplified herein. id="p-68" id="p-68" id="p-68" id="p-68"

[0068] Radio detection system 1000 may comprise a plurality of EMR absorbing elements 1500 configured and arranged to form grooves and ridges of an EMR absorbing structure 1400. id="p-69" id="p-69" id="p-69" id="p-69"

[0069] EMR absorbing elements 1500 may have longitudinal axes E (E1,…, En) which are perpendicular with respect to a longitudinal axis Y of the radar system, extending from transmitter antenna 1100 to receiver antenna 1200, and further perpendicular with 11 common base or base plate 1300. id="p-70" id="p-70" id="p-70" id="p-70"

[0070] In some embodiments, the plurality of EMR absorbing elements 1500 may be arranged in parallel (also: substantially parallel) to one another. According to some embodiments, EMR absorbing structure 1400 is configured to reduce or prevent the induction of surface currents between transmitter antenna 1100 and receiver antenna 1200 such that the reflection-based signals generated by receiver antenna 1200 are stronger than surface currents picked up by receiver antenna 1200. In some examples, EMR absorbing structure 1400 may cause complete extinction of surface currents, such that no surface currents are picked up by receiver antenna 1200. id="p-71" id="p-71" id="p-71" id="p-71"

[0071] According to some embodiments, EMR absorbing structure 1400 may be made of any conductive or semi-conductive material such as metal, a silicon-based compound, and/or the like. id="p-72" id="p-72" id="p-72" id="p-72"

[0072] According to some embodiments, the reduction in induction of surface currents induced by the EMR absorbing structure 1400 enables reception of comparatively weak electromagnetic radiation reflected from scene 500. Optionally, a reduction in magnitude of induced surface currents may cause the surface currents reaching receiver antenna 1200 to drop below a certain threshold. id="p-73" id="p-73" id="p-73" id="p-73"

[0073] Accordingly, compared to known antenna-based radio detection systems lacking the EMR absorbing structure, embodiments of radio detection systems comprising an EMR absorbing structure may be configured to increase a Signal Noise to Ratio (SNR) between the reflection-based signals and the surface currents. id="p-74" id="p-74" id="p-74" id="p-74"

[0074] According to some embodiments, EMR absorbing structure 1400 may be configured to provide at least 30dB increase in SNR between the reflection-based signals and the surface currents. According to some embodiments, the at least 30dB increase in SNR is achieved across a frequency band of at least 1.5 GHz, 2 GHz or at least 3 GHz. id="p-75" id="p-75" id="p-75" id="p-75"

[0075] According to some embodiments, at least one geometric characteristic of the plurality of EMR absorbing elements 1500 is specifically adapted to a certain wavelength band being transmitted to reduce or minimize the induction of surface currents (e.g., in base 1300) by transmitter antenna 1100. 12 EMR absorbing elements may be automatically adaptable, e.g., based on a wavelength or wavelength range to be transmitted by transmitter antenna 1100 to reduce or minimize the induction of surface currents. id="p-77" id="p-77" id="p-77" id="p-77"

[0077] For example, at least one geometric characteristic of the plurality of EMR absorbing elements 1500 may be controllably adaptable, hence, it may be altered to provide ultimate reduction of surface currents adapted to various wavelength band or to any other factor. id="p-78" id="p-78" id="p-78" id="p-78"

[0078] For example, EMR absorbing structure may include "smart" material or materials that undergoes transformation (e.g., geometric transformation, phase transformation) in response to suitable external stimuli applied, thus enabling controllable EMR absorption. Such material may for example have shape memory properties, electro-activatable (e.g., piezoelectric) properties, and/or magnetorheological properties. Shape memory material may be implemented, for example, by a shape memory alloy (SMA) or a shape memory polymer (SMP). The applied stimuli may for example pertain to voltage, electric current, temperature, and/or a magnetic field. id="p-79" id="p-79" id="p-79" id="p-79"

[0079] In some examples, the radiation detection system may comprise one or more actuators that are based on smart materials for controllably adapting the system’s EMR absorption characteristics. id="p-80" id="p-80" id="p-80" id="p-80"

[0080] For example, a height, width and/or a taper angle, of an absorption element may be controllably adapted. In a further example, a distance or gap between two adjacent absorption elements may be controllably adjustable by applying at least one suitable stimulus. id="p-81" id="p-81" id="p-81" id="p-81"

[0081] In some examples, a gap between adjacent absorption elements may be controllably mechanically adapted by employing, for example, a telescopic mechanism. id="p-82" id="p-82" id="p-82" id="p-82"

[0082] For example, an increase in the gap or taper angle between two adjacent absorption elements may increase the absorption bandwidth. Conversely, a decrease in the gap or taper angle between two adjacent absorption elements may decrease the absorption bandwidth of the EMR absorbing structure. 13 that are based on different smart materials, may be employed for controllably adapting different portions of the EMR absorption structure. For example, the system may be configured such that a first EMR absorption element responds to a certain smart material activation stimulus differently than a second EMR absorption element. In a further example, at least one EMR absorption element may be non-responsive to a smart material activation stimulus, while at least one other EMR absorption element may be responsive to the same smart material activation stimulus. In a yet additional example, the system may be configured such that, concurrently or at different points in time, different stimuli may be applied to different EMR absorption elements configured to be controllably adaptable by smart materials. The expression "different stimuli" may pertain to different magnitudes of same physical input, or to physical input of different type. For instance, a geometric characteristic of a first EMR absorption element may be controllably adapted through temperature-activatable smart material, and a geometric characteristic of a second EMR absorption element may be controllably adapted by, e.g., an electric-activatable smart material. id="p-84" id="p-84" id="p-84" id="p-84"

[0084] In some embodiments, different geometric characteristics of a same EMR absorption element may be controllably adaptable by applying different stimuli to a same smart material or to different smart materials. id="p-85" id="p-85" id="p-85" id="p-85"

[0085] According to some embodiments, at least one geometric characteristic of the plurality of EMR absorbing elements 1500 includes a periodical or non-periodical feature of EMR absorbing structure 1400. According to some embodiments, the plurality of EMR absorbing elements 1500, as a whole, may form a periodic structure. For example, EMR absorbing elements 1500 may form a corrugated, crinkled, wrinkled structure, etc., having ridges that may protrude in Z-direction and/or in any other desirable direction. id="p-86" id="p-86" id="p-86" id="p-86"

[0086] According to some embodiments, the plurality of EMR absorbing elements 1500 may form a non-periodic structure having a geometric irregularity also configured to reduce the surface currents generated by transmitter antenna 1100. According to some embodiments, the plurality of EMR absorbing elements 1500 form a fractal structure. 14 protrude beneath the common ground plane, in a direction opposite to the EMR radiation emitted by transmitter antenna 1100. According to some embodiments, EMR absorbing elements 1500 may protrude above the common ground plane, in the direction of the electromagnetic radiation emitted by transmitter antenna 1100. id="p-88" id="p-88" id="p-88" id="p-88"

[0088] According to some embodiments, at least two of the EMR absorbing elements 1500 may protrude above the common ground plane, in the direction of the electromagnetic radiation emitted by transmitter antenna 1100, and wherein at least another two of the EMR absorbing elements protrude beneath the common ground plane, in a direction opposite to the electromagnetic radiation emitted by transmitter antenna 1100. id="p-89" id="p-89" id="p-89" id="p-89"

[0089] As schematically shown in Fig. 2, at least two of EMR absorbing elements 1502 of a radio detection system 1002 forming EMR absorbing structure 1402 may, for example, have a rectangular cross-section and be arranged relative to each other to form grooves of corresponding rectangular shape extending along the X-direction. FIG. 2 further shows transmitter input port 1102 and receiver output port 1202 which are in respective communication with transmitter antenna 1100 and receiver antenna 1200. id="p-90" id="p-90" id="p-90" id="p-90"

[0090] According to some embodiments, EMR absorbing elements according to further embodiments may have a tapered or narrowing cross-section and be arranged relative to each other to form grooves of corresponding widening shape. id="p-91" id="p-91" id="p-91" id="p-91"

[0091] As for example shown Figs. 3A-D, the cross-section of EMR absorbing elements 1500A-D the respective EMR absorbing structures 1404, 1406, 1408 and 1410, may narrow or taper in a direction D that points from scene 500 towards base 1300, i.e., in a direction that is reverse to axis Z. As a result, corresponding cavities 1600A-D are formed between two neighboring EMR absorbing elements 1500A-D that narrow or taper from base 1300 towards scene 500. id="p-92" id="p-92" id="p-92" id="p-92"

[0092] EMR absorbing elements 1500 may have various tapered or narrowing cross- sectional geometries in a direction opposite to positive Z including, for example, a triangular cross-section (Fig. 3A), a T-shaped cross-section (Figs. 3B), a trapezoidal cross- 3C-3D. id="p-93" id="p-93" id="p-93" id="p-93"

[0093] According to some embodiments, a plurality of EMR absorbing elements may be disposed in a matrix arrangement. For example, a plurality of EMR absorbing elements may arranged to extend along X-axis, and a further plurality of EMR absorbing elements be arranged to extend in Y-direction. For example, as shown schematically in FIG. 3D, a plurality of cones or cone-shaped bodies may be arranged in a matrix to create an EMR absorbing structure. Optionally, pyramids or pyramid-like structures may be configured in a matrix arrangement to create an EMR absorbing structure. EMR absorbing elements of different shapes may be employed in combination to create an EMR absorbing structure. For example, at least two cone-like elements as well as a at least two pyramid-like elements may be employed for implementing an EMR absorbing structure. id="p-94" id="p-94" id="p-94" id="p-94"

[0094] Additional reference is made to FIG. 4A, exemplifying an antenna-based radio detection system 1004 comprising EMR absorbing elements 1504 forming EMR absorbing structure 1404. At least two of EMR absorbing elements 1504 may have a triangular cross-section and set in an orientation such that the triangular cross-section of at least one of the plurality of EMR absorbing elements 1504 is widening towards scene 500, such that the cavities formed by the elements are narrowing towards the scene. id="p-95" id="p-95" id="p-95" id="p-95"

[0095] The plurality of EMR absorbing elements 1504 are arranged in a periodical manner across base plate 1300. According to some embodiments, a tapered or otherwise narrowing cross-section e.g., as shown in FIG. 4B, may have an improved ability to reduce surface currents by diverting electromagnetic radiation in a wide frequency band. In the example configuration shown in FIG. 4B, at least two of the plurality of EMR absorbing elements 1500 may have a tapered cross-section oriented such that a narrow edge of the EMR absorbing element is facing the base plate 1300 and the wider edge is facing in direction of scene 500. In some examples, recesses may be configured to allow for surface currents Js of different wavelengths to traverse corresponding quarter path lengths ¼1,…,¼N which are herein exemplified by V -V . 1 N 16 attenuation for surface current Js is obtained. id="p-96" id="p-96" id="p-96" id="p-96"

[0096] According to some embodiments, as schematically shown in FIG. 4B, upon operation of the antenna-based radio detection system 1000, electromagnetic radiation may radiate along vectors 1 to 8, and as a result, in a wider frequency band, hence comparatively efficiently reduce the surface currents that would otherwise be transmitted or flow unattenuated or substantially unattenuated to receiver antenna 1200. According to some embodiments, at least two of the plurality of EMR absorbing elements 1500 may assume any shape widening in direction of scene 500, i.e., in a direction normal to base plate 1300. id="p-97" id="p-97" id="p-97" id="p-97"

[0097] Further reference is made to FIGs. 5A-D, showing the equivalent electronic circuits in overlay with the corresponding EMR absorbing structures 1402, 1404, 1406, and 1408. id="p-98" id="p-98" id="p-98" id="p-98"

[0098] Additional reference is made to FIGS. 6A and 6B. An antenna-based radio detection system 1005 may comprise a plurality of EMR absorbing elements 1505. At least two of the EMR absorbing elements 1505 may have a T-shaped cross-section and arranged in a periodical manner across the base plate 1300. According to some embodiments, each EMR absorbing element 1505 is oriented such that its narrower edge is facing toward the base plate 1300 and its wider edge (the T-shaped head) is facing the direction of scene 500, in direction of the electromagnetic radiation emitted by transmitter antenna 1100. id="p-99" id="p-99" id="p-99" id="p-99"

[0099] Referring now to FIG. 7A, the following geometric parameters of absorption elements are schematically shown for an ERM absorbing structure comprising rectangular absorption elements: id="p-100" id="p-100" id="p-100" id="p-100"

[0100] H – height or depth of an (e.g., rectangular) absorption element id="p-101" id="p-101" id="p-101" id="p-101"

[0101] W – width or maximum width of an (e.g., rectangular) absorption element id="p-102" id="p-102" id="p-102" id="p-102"

[0102] SS – distance between two adjacent geometric symmetry centers of (e.g., rectangular) absorption elements. Considering constant W and SS for all absorption elements, then the gap "G" between two adjacent rectangular absorption elements is defined as SS-W. 17 7B demonstrate surface current isolation properties for different geometric parameters of absorption elements of an antenna-based radio detection system. id="p-104" id="p-104" id="p-104" id="p-104"

[0104] As can readily be seen from FIG. 7B, EMR absorption elements having a tapered cross-sectional profile provide comparatively improved isolation performance compared to EMR absorption elements having rectangular cross-sectional profiles. id="p-105" id="p-105" id="p-105" id="p-105"

[0105] Compared to a traditional antenna-based radio detection system that lack the EMR absorbing structure 1400, systems that do employ an EMR absorbing structure exhibit significantly improved surface current isolation performance. Depending on the configuration of the EMR absorbing structure, varied isolation performance is obtained along the frequency band. For the variety of EMR absorbing structures, best isolation results (attenuation up to 30 dB) are achieved at about 9.5 GHz, resulting in a corresponding reduction in surface currents flowing from the transmitting to the receiver antenna. id="p-106" id="p-106" id="p-106" id="p-106"

[0106] A shown with respect to the blue graph for tapered EMR absorption elements, approximately a median or average attenuation of 30 dB can be achieved across a comparatively broad frequency band ranging from about 9.5 GHz to about 11 GHz. In some examples, an attenuation ranging 20 dB to 90 dB may be achieved. This is in distinct contrast to the rectangular EMR absorption elements for which a maximum, median or average attenuation of 30 dB is limited around a comparatively narrow frequency band of about 9.5 GHz. id="p-107" id="p-107" id="p-107" id="p-107"

[0107] Further reference is made to FIG. 8. A heat-map simulation is schematically shown in FIG. 8 to depict the effect of T-shaped EMR absorption elements on electromagnetic radiation attenuation from the transmitter to the receiver side. id="p-108" id="p-108" id="p-108" id="p-108"

[0108] Additional reference is made to FIG. 9 schematically showing a graph of S- parameters measured during operation of the antenna-based radio detection system 1000, according to some embodiments. S-parameters describe the input-output relationship between ports (or terminals) in an electrical system such as a radio detection system. 18 NM multi-port network. For example, if such system has 2 ports (e.g., designated as "Port 1" and "Port 2"), then S12 represents the power transferred from Port 2 to Port 1, vice versa, S21 represents the power transferred from Port 1 to Port 2. As shown, the S- parameters measured during the operation of the antenna-based radio detection system 1000 shows a maximal reduction in dB isolation at approximately 9.0-9.5 GHz, as demonstrated by line E. This in stark contrast to the isolation, depicted by line F, obtained in a known antenna-based radio detection system that does not employ an EMR absorbing structure. These results correspond with the results of the surface currents isolation parameters measured during operation of antenna-based radio detection system 1000, schematically shown in FIG. 8. id="p-110" id="p-110" id="p-110" id="p-110"

[0110] Referring now to FIGS. 10A-10B. Various views of an antenna array 1900 forming a part of an antenna-based radio detection system and that may be employed as a transmitter antenna 1100 and/or receiver antenna 1200. id="p-111" id="p-111" id="p-111" id="p-111"

[0111] Antenna array 1900 may comprise at least one radiator 1902 (e.g., implemented as a square patch) that is coupled with a feeder 1904. id="p-112" id="p-112" id="p-112" id="p-112"

[0112] Feeder 1904 is configured to operate as a transmission line 1910 that connects antenna array 1900 with a radio transmitter/receiver (not shown) operating as part of the antenna-based radio detection system 1000. In a transmitter antenna 1100, feeder 1904 feeds the radio frequency (RF) current to radiator 1902, where it is radiated as radio waves. In a receiver antenna 1200, feeder 1904 transfers the electromagnetic radiation received through radiator 1902 to generate RF voltage signals induced by the electromagnetic radiation reflection. id="p-113" id="p-113" id="p-113" id="p-113"

[0113] Feeder 1904 may be connected to the transmitter/receiver via an RF connector 1908. id="p-114" id="p-114" id="p-114" id="p-114"

[0114] A transformer may be employed configured in accordance with a desired signal transmission to or signal reception output from antenna array 1900. id="p-115" id="p-115" id="p-115" id="p-115"

[0115] According to some embodiments, antenna array 1900 is configured to transmits a linear modulated EMR RF signal, wherein the reflected signal has a time delay 19 antenna-based radio detection system 1000 and the target. id="p-116" id="p-116" id="p-116" id="p-116"

[0116] According to some embodiments, antenna array 1900 can form different radiation patterns by controlling the phase and amplitude of the wavelength band signal in each antenna channel. id="p-117" id="p-117" id="p-117" id="p-117"

[0117] According to some embodiments, a base 1912 may be employed, configured with mechanical holes to be fixed to base plate 1300 (previously disclosed). Base 1912 may be composed from various materials such as, for example, woven glass reinforced hydrocarbon/ceramics, PTFE or any other material having desirable characteristics. id="p-118" id="p-118" id="p-118" id="p-118"

[0118] According to some embodiments, a cover 2000 may be employed as a lid designated to overlay a base, and therefore the EMR absorbing structure of a radio detection system. id="p-119" id="p-119" id="p-119" id="p-119"

[0119] Cover 2000 may be made of any suitable material (e.g., a polymer-based material) to provide dust and humidity protection to the various components comprising the antenna-based radio detection system 1000, without attenuating electromagnetic radiation transmitted by or received at antenna-based radio detection system 1000.

According to some embodiments, cover 2000 may be transparent or semi-transparent to provide a clear view of the various components comprising the antenna-based radio detection system 1000. FIG. 11 shows a photograph of an example implementation of placement of cover 2000 on radio detection system 1005. id="p-120" id="p-120" id="p-120" id="p-120"

[0120] Further reference is made to FIG. 12. According to some examples, a method for detecting objects in a scene using an antenna-based radio detection system, may comprise transmitting, by at least one transmitter antenna arranged at a first location, EMR into free space towards a scene (block 12002). id="p-121" id="p-121" id="p-121" id="p-121"

[0121] The method may further comprise reducing the induction of surface currents induced by the transmission of electromagnetic radiation into the free space (block 12004). id="p-122" id="p-122" id="p-122" id="p-122"

[0122] In some examples, the method may further comprise receiving, by at least one receiver antenna, at a second location different from the first location, electromagnetic radiation reflections reflected by at least one object from the scene (block 12006). electromagnetic radiation reflections, reflection-based signals. Reducing the induction of surface currents is achieved by an electromagnetic radiation absorbing structure formed by a plurality of EMR absorbing elements disposed between the first and the second location such that the reflection-based signals are stronger than received surface currents (block 12008). id="p-124" id="p-124" id="p-124" id="p-124"

[0124] Additional Examples: id="p-125" id="p-125" id="p-125" id="p-125"

[0125] Example 1 pertains to an antenna-based radio detection system, comprising: id="p-126" id="p-126" id="p-126" id="p-126"

[0126] at least one transmitter antenna arranged at a first location and configured to emit electromagnetic (EM) radiation into free space toward a scene to generate electromagnetic radiation reflections reflected by at least one object in the scene; id="p-127" id="p-127" id="p-127" id="p-127"

[0127] at least one receiver antenna arranged at a second location spatially separated from the first location and configured to generate, based on the electromagnetic radiation reflections received at the receiver antenna from the scene, reflection-based signals; and id="p-128" id="p-128" id="p-128" id="p-128"

[0128] an electromagnetic radiation (EMR) absorbing structure formed by a plurality of EMR absorbing elements and that is disposed between the first and the second location. The EMR absorbing structure is configured to reduce the induction of surface currents between the transmitter and receiver antenna such that the reflection-based signals generated by the receiver antenna are stronger than surface currents picked up by the receiver antenna. id="p-129" id="p-129" id="p-129" id="p-129"

[0129] In Example 2, the subject matter of Example 1 optionally includes wherein the wherein the transmitter and the receiver antenna are separated from each other by a rigid plate structure. id="p-130" id="p-130" id="p-130" id="p-130"

[0130] In Example 3, the subject matter of Example 1 and/or Example 2 optionally include wherein a reduction in induction of surface currents enables analyzing a comparatively weak reflection-based signals generated by the receiver antenna. id="p-131" id="p-131" id="p-131" id="p-131"

[0131] In Example 4, the subject matter of any one or more of the Examples 1-3 optionally includes wherein the induction of surface currents is configured to be reduced below a threshold by the EMR absorbing structure. 21 optionally includes wherein the EMR absorbing structure is configured to increase a Signal Noise to Ratio (SNR) between the reflection-based signals and the surface currents, compared to antenna-based radio detection systems lacking the EMR absorbing structure. id="p-133" id="p-133" id="p-133" id="p-133"

[0133] In Example 6, the subject matter of any one or more of the Examples 1-5 optionally includes wherein the EMR absorbing structure is configured to provide at least dB increase in SNR between the reflection-based signals and the surface currents picked up by the receiver antenna. id="p-134" id="p-134" id="p-134" id="p-134"

[0134] In Example 7, the subject matter of example 6 optionally includes wherein the at least 30dB increase in SNR is achieved across a frequency band of at least 1.5 GHz. id="p-135" id="p-135" id="p-135" id="p-135"

[0135] In Example 8, the subject matter of any one or more of the Examples 1-7 optionally includes wherein at least one geometric characteristic of the plurality of EMR absorbing elements is specifically adapted to a transmitting and/or receiving wavelength band to reduce or eliminate the induction of surface currents. id="p-136" id="p-136" id="p-136" id="p-136"

[0136] In Example 9, the subject matter of example 8 optionally includes wherein the at least one geometric characteristic is controllably adaptable. id="p-137" id="p-137" id="p-137" id="p-137"

[0137] In Example 10 the subject matter of any one or more of the Examples 8-9 optionally includes wherein the at least one geometric characteristic includes a periodical or non-periodical feature of the EMR absorbing structure. id="p-138" id="p-138" id="p-138" id="p-138"

[0138] In Example 11 the subject matter of any one or more of the Examples 1-10 optionally includes wherein the plurality of EMR absorbing elements form a periodic structure. id="p-139" id="p-139" id="p-139" id="p-139"

[0139] In Example 12 the subject matter of any one or more of the Examples 1-11 optionally includes wherein the plurality of EMR absorbing elements form a non-periodic structure. id="p-140" id="p-140" id="p-140" id="p-140"

[0140] In Example 13 the subject matter of any one or more of the Examples 1-12 optionally includes, wherein the plurality of EMR absorbing elements form a fractal structure. 22 optionally includes wherein each one of the plurality of EMR absorbing elements has one of the following geometric characteristics: a rectangular cross-section, a trapezoidal cross-section, a triangular cross-section, a cross-section that is widening in direction of the scene, a T-shaped cross-section, and a V-shaped cross-section. id="p-142" id="p-142" id="p-142" id="p-142"

[0142] In Example 15, the subject matter of any one or more of the Examples 1-14 optionally includes wherein the EMR absorbing elements protrude beneath a common ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna. id="p-143" id="p-143" id="p-143" id="p-143"

[0143] In Example 16, the subject matter of any one or more of the Examples 1-15 optionally includes wherein the EMR absorbing elements protrude above the common ground plane, in direction of the electromagnetic radiation emitted by the transmitter antenna. id="p-144" id="p-144" id="p-144" id="p-144"

[0144] In Example 17, the subject matter of any one or more of the Examples 15-16 optionally includes wherein at least two of the plurality of EMR absorbing elements protrude above the common ground plane, in a direction of the electromagnetic radiation emitted by the transmitter antenna. At least another two of the EMR absorbing elements protrude beneath the common ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna. id="p-145" id="p-145" id="p-145" id="p-145"

[0145] In Example 18, the subject matter of any one or more of the Examples 15-17 optionally includes wherein the EMR absorbing elements are arranged to constitute part of the common ground plane. id="p-146" id="p-146" id="p-146" id="p-146"

[0146] In Example 19, the subject matter of any one or more of the Examples 15-18 optionally includes wherein the EMR absorbing elements have a longitudinal axis extending in a second direction perpendicular to the first direction of the longitudinal axis of the EMR absorbing structure and further perpendicular to the normal vector of the common ground plane. id="p-147" id="p-147" id="p-147" id="p-147"

[0147] In Example 20, the subject matter of any one or more of the Examples 1-19 optionally includes wherein upon operation of the system the transmitter antenna (e.g., continuously) transmits electromagnetic radiation and the receiver antenna (e.g., 23 signals. id="p-148" id="p-148" id="p-148" id="p-148"

[0148] In Example 21, the subject matter of any one or more of the Examples 1-20 optionally includes a Frequency-Modulated Continuous Wave (FMCW) radar. id="p-149" id="p-149" id="p-149" id="p-149"

[0149] In Example 22, the subject matter of any one or more of the Examples 1-21 optionally includes wherein the transmitter antenna is spatially separated from the receiver antenna at a distance equal or less than 190 mm, equal or less than 180 mm, equal or less than 170 mm, equal or less than 160 mm, equal or less than 150 mm, equal or less than 140 mm, equal or less than 130 mm or equal or less than 120 mm. id="p-150" id="p-150" id="p-150" id="p-150"

[0150] In Example 23, the subject matter of any one or more of the Examples 1-22 optionally includes wherein at least two components forming the system are assembly components. id="p-151" id="p-151" id="p-151" id="p-151"

[0151] In Example 24, the subject matter of any one or more of the Examples 1-23 optionally includes wherein the various components forming the system are configured to be housed in a casing. id="p-152" id="p-152" id="p-152" id="p-152"

[0152] Example 25 concerns a method for detecting objects in a scene using an antenna-based radio detection system, the method comprising: id="p-153" id="p-153" id="p-153" id="p-153"

[0153] transmitting, by at least one transmitter antenna arranged at a first location, electromagnetic radiation into free space towards the scene; id="p-154" id="p-154" id="p-154" id="p-154"

[0154] reducing the induction of surface currents induced by the transmission of electromagnetic radiation into the free space; id="p-155" id="p-155" id="p-155" id="p-155"

[0155] receiving, by at least one receiver antenna, at a second location different from the first location, electromagnetic radiation reflections reflected by at least one object from the scene; and id="p-156" id="p-156" id="p-156" id="p-156"

[0156] generating, based on the received electromagnetic radiation reflections, reflection-based signals; id="p-157" id="p-157" id="p-157" id="p-157"

[0157] wherein reducing the induction of surface currents is achieved by an electromagnetic radiation (EMR) absorbing structure formed by a plurality of EMR 24 reflection-based signals are stronger than received surface currents. id="p-158" id="p-158" id="p-158" id="p-158"

[0158] In Example 26, the subject matter of Example 25 optionally includes: wherein the transmitter and the receiver antenna are separated from each other by a rigid plate structure. id="p-159" id="p-159" id="p-159" id="p-159"

[0159] In Example 27, the subject matter of Examples 25 and/or 26 optionally includes wherein a reduction in the induction of surface currents enables analyzing a comparatively weak reflection-based signals generated by the receiver antenna. id="p-160" id="p-160" id="p-160" id="p-160"

[0160] In Example 28, the subject matter of any one or more of the Examples 25 to 27 optionally includes wherein the induction of surface currents is configured to be reduced below a threshold by the EMR absorbing structure. id="p-161" id="p-161" id="p-161" id="p-161"

[0161] In Example 29, the subject matter of any one or more of the Examples 25 to 28 optionally includes wherein the EMR absorbing structure is configured to increase a Signal Noise to Ratio (SNR) between the reflection-based signals and the surface currents, compared to antenna-based radio detection systems lacking the EMR absorbing structure. id="p-162" id="p-162" id="p-162" id="p-162"

[0162] In example 30, , the subject matter of any one or more of the Examples 25 to 29 optionally includes wherein the EMR absorbing structure is configured to provide at least 30dB increase in SNR between the reflection-based signals and the surface currents picked up by the receiver antenna. id="p-163" id="p-163" id="p-163" id="p-163"

[0163] In Example 31, the subject matter of any one or more of the Examples 25 to optionally includes wherein the at least 30dB increase in SNR is achieved across a frequency band of at least 1.5 GHz. id="p-164" id="p-164" id="p-164" id="p-164"

[0164] In Example 32, the subject matter of any one or more of the Examples 25 to 31 optionally includes wherein at least one geometric characteristic of the plurality of EMR absorbing elements is specifically adapted to a transmitting and/or receiving wavelength band to reduce or eliminate the induction of surface currents. id="p-165" id="p-165" id="p-165" id="p-165"

[0165] In Example 33, the subject matter of any one or more of the Examples 25 to 32 optionally includes wherein the at least one geometric characteristic is controllably adaptable. 33 optionally includes wherein the at least one geometric characteristic includes a periodical or non-periodical feature of the EMR absorbing structure. id="p-167" id="p-167" id="p-167" id="p-167"

[0167] In Example 35, the subject matter of any one or more of the Examples 25 to 34 optionally includes, wherein the plurality of EMR absorbing elements form a periodic structure. id="p-168" id="p-168" id="p-168" id="p-168"

[0168] In Example 36, the subject matter of any one or more of the Examples 25 to optionally includes wherein the plurality of EMR absorbing elements form a non- periodic structure. id="p-169" id="p-169" id="p-169" id="p-169"

[0169] In Example 37, the subject matter of any one or more of the Examples 25 to 36 optionally includes wherein the plurality of EMR absorbing elements form a fractal structure. id="p-170" id="p-170" id="p-170" id="p-170"

[0170] In Example 38, the subject matter of any one or more of the Examples 25 to 37 optionally includes wherein each one of the plurality of EMR absorbing elements has one of the following geometric characteristics: a rectangular cross-section, a trapezoidal cross-section, a triangular cross-section, a cross-section that is widening in direction of the scene, a T-shaped cross-section, and a V-shaped cross-section. id="p-171" id="p-171" id="p-171" id="p-171"

[0171] In Example 39, the subject matter of any one or more of the Examples 25 to 38 optionally includes wherein the EMR absorbing elements protrude beneath a common ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna. id="p-172" id="p-172" id="p-172" id="p-172"

[0172] In Example 40, the subject matter of any one or more of the Examples 25 to 39 optionally includes wherein the EMR absorbing elements protrude above the common ground plane, in direction of the electromagnetic radiation emitted by the transmitter antenna. id="p-173" id="p-173" id="p-173" id="p-173"

[0173] In Example 41, the subject matter of any one or more of the Examples 25 to 40 optionally includes wherein at least two of the plurality of EMR absorbing elements protrude above the common ground plane, in a direction of the electromagnetic radiation emitted by the transmitter antenna; and wherein at least another two of the 26 opposite to the electromagnetic radiation emitted by the transmitter antenna. id="p-174" id="p-174" id="p-174" id="p-174"

[0174] In Example 42, the subject matter of any one or more of the Examples 25 to 41 optionally includes wherein the EMR absorbing elements are arranged to constitute part of the common ground plane. id="p-175" id="p-175" id="p-175" id="p-175"

[0175] In Example 43, the subject matter of any one or more of the Examples 25 to 42 optionally includes wherein the EMR absorbing elements have a longitudinal axis extending in a second direction perpendicular to the first direction of the longitudinal axis of the EMR absorbing structure and further perpendicular to the normal vector of the common ground plane. id="p-176" id="p-176" id="p-176" id="p-176"

[0176] In Example 44, the subject matter of any one or more of the Examples 25 to 43 optionally includes wherein upon operation of the system the transmitter antenna (e.g., continuously) transmits electromagnetic radiation while the receiver antenna (e.g., continuously) receives electromagnetic radiation to generate the reflection-based signals. id="p-177" id="p-177" id="p-177" id="p-177"

[0177] In Example 45, the subject matter of any one or more of the Examples 25 to 44 optionally includes a Frequency-Modulated Continuous Wave (FMCW) radar id="p-178" id="p-178" id="p-178" id="p-178"

[0178] In Example 46, the subject matter of any one or more of the Examples 25 to 45 optionally includes wherein the transmitter antenna is spatially separated from the receiver antenna at a distance equal or less than 190 mm, equal or less than 180 mm, equal or less than 170 mm, equal or less than 160 mm, equal or less than 150 mm, equal or less than 140 mm, equal or less than 130 mm or equal or less than 120 mm. id="p-179" id="p-179" id="p-179" id="p-179"

[0179] In Example 47, the subject matter of any one or more of the Examples 25 to 46 optionally includes wherein at least two components forming the system are assembly components. id="p-180" id="p-180" id="p-180" id="p-180"

[0180] In Example 48, the subject matter of any one or more of the Examples 25 to 47 optionally includes wherein the various components forming the system are configured to be housed in a casing. id="p-181" id="p-181" id="p-181" id="p-181"

[0181] In the discussion, unless otherwise stated, adjectives such as "substantially" and "about" that modify a condition or relationship characteristic of a feature or features 27 characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended. id="p-182" id="p-182" id="p-182" id="p-182"

[0182] Unless otherwise specified, the terms "substantially", "'about" and/or "close" with respect to a magnitude or a numerical value may imply to be within an inclusive range of -10% to +10% of the respective magnitude or value. id="p-183" id="p-183" id="p-183" id="p-183"

[0183] It is important to note that the method may include is not limited to those diagrams or to the corresponding descriptions. For example, the method may include additional or even fewer processes or operations in comparison to what is described in the figures. In addition, embodiments of the method are not necessarily limited to the chronological order as illustrated and described herein. id="p-184" id="p-184" id="p-184" id="p-184"

[0184] Discussions herein utilizing terms such as, for example, "processing", "computing", "calculating", "determining", "establishing", "analyzing", "checking", "estimating", "deriving", "selecting", "inferring" or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulate and/or transform data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information storage medium that may store instructions to perform operations and/or processes. The term determining may, where applicable, also refer to "heuristically determining". id="p-185" id="p-185" id="p-185" id="p-185"

[0185] It should be noted that where an embodiment refers to a condition of "above a threshold", this should not be construed as excluding an embodiment referring to a condition of "equal or above a threshold". Analogously, where an embodiment refers to a condition "below a threshold", this should not to be construed as excluding an embodiment referring to a condition "equal or below a threshold". It is clear that should a condition be interpreted as being fulfilled if the value of a given parameter is above a threshold, then the same condition is considered as not being fulfilled if the value of the given parameter is equal or below the given threshold. Conversely, should a condition be interpreted as being fulfilled if the value of a given parameter is equal or above a 28 given parameter is below (and only below) the given threshold. id="p-186" id="p-186" id="p-186" id="p-186"

[0186] It should be understood that where the claims or specification refer to "a" or "an" element and/or feature, such reference is not to be construed as there being only one of that element. Hence, reference to "an element" or "at least one element" for instance may also encompass "one or more elements". id="p-187" id="p-187" id="p-187" id="p-187"

[0187] Terms used in the singular shall also include the plural, except where expressly otherwise stated or where the context otherwise requires. id="p-188" id="p-188" id="p-188" id="p-188"

[0188] In the description and claims of the present application, each of the verbs, "comprise" "include" and "have", and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of components, elements or parts of the subject or subjects of the verb. id="p-189" id="p-189" id="p-189" id="p-189"

[0189] Unless otherwise stated, the use of the expression "and/or" between the last two members of a list of options for selection indicates that a selection of one or more of the listed options is appropriate and may be made. Further, the use of the expression "and/or" may be used interchangeably with the expressions "at least one of the following", "any one of the following" or "one or more of the following", followed by a listing of the various options. id="p-190" id="p-190" id="p-190" id="p-190"

[0190] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments or example, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, example and/or option, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment, example or option of the invention. Certain features described in the context of various embodiments, examples and/or optional implementation are not to be considered essential features of those embodiments, unless the embodiment, example and/or optional implementation is inoperative without those elements. 29 embodiments", "for example", "e.g.", "for instance" and "optionally" may herein be used interchangeably. id="p-192" id="p-192" id="p-192" id="p-192"

[0192] The number of elements shown in the Figures should by no means be construed as limiting and is for illustrative purposes only. id="p-193" id="p-193" id="p-193" id="p-193"

[0193] It is noted that the terms "operable to" can encompass the meaning of the term "adapted or configured to". In other words, a machine "operable to" perform a task can in some embodiments, embrace a mere capability (e.g., "adapted") to perform the function and, in some other embodiments, a machine that is actually made (e.g., "configured") to perform the function. id="p-194" id="p-194" id="p-194" id="p-194"

[0194] Throughout this application, various embodiments may be presented in and/or relate to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the embodiments. Accordingly, the description of a range should be considered to have speciﬁcally disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have speciﬁcally disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. id="p-195" id="p-195" id="p-195" id="p-195"

[0195] The phrases "ranging/ranges between" a ﬁrst indicate number and a second indicate number and "ranging/ranges from" a ﬁrst indicate number "to" a second indicate number are used herein interchangeably and are meant to include the ﬁrst and second indicated numbers and all the fractional and integral numerals there between. id="p-196" id="p-196" id="p-196" id="p-196"

[0196] While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the embodiments.

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Claims

1. An antenna-based radio detection system, comprising: (i) at least one transmitter antenna arranged at a first location and configured to emit electromagnetic (EM) radiation into free space toward a scene to generate electromagnetic radiation reflections reflected by at least one object in the scene; (ii) at least one receiver antenna arranged at a second location spatially separated from the first location and configured to generate, based on the electromagnetic radiation reflections received at the receiver antenna from the scene, reflection- based signals; and (iii) an electromagnetic radiation (EMR) absorbing structure formed by a plurality of EMR absorbing elements which are disposed between the first and the second location; wherein the EMR absorbing elements have a longitudinal axis X extending in a second direction which is about perpendicular to a first direction extending along an axis Y between the at least one transmitter antenna and the at least one receiver antenna, and further extending about perpendicular with respect to a direction of free space emission of EMR radiation towards the scene; wherein each one of the plurality of absorbing elements is arranged at a different position along the first direction extending between the at least one transmitter antenna and the at least one receiver antenna; and wherein the EMR absorbing structure is configured to reduce the induction of surface currents J between the transmitter and receiver antenna such that the S reflection-based signals generated by the receiver antenna are stronger than the surface currents picked up by the receiver antenna.

2. The antenna-based radio detection system of claim 1, wherein a recess formed by two neighboring EMR absorbing elements has a height that corresponds to about a quarter of a wavelength of a center frequency of the surface currents J . S 30

3. The antenna-based radio detection system of claim 1 or claim 2, wherein the transmitter antenna and the receiver antenna are separated from each other by a rigid plate structure.

4. The antenna-based radio detection system of any one or more of the preceding claims, wherein a reduction in induction of surface currents enables analyzing a comparatively weak reflection-based signals generated by the receiver antenna.

5. The antenna-based radio detection system of any one of the preceding claims, wherein the induction of surface currents is configured to be reduced below a threshold by the EMR absorbing structure.

6. The antenna-based radio detection system of any one of the preceding claims, wherein the EMR absorbing structure is configured to increase a Signal Noise to Ratio (SNR) between the reflection-based signals and the surface currents, compared to antenna- based radio detection systems lacking the EMR absorbing structure.

7. The antenna-based radio detection system of any one of the preceding claims, wherein the EMR absorbing structure is configured to provide at least 30dB increase in SNR between the reflection-based signals and the surface currents picked up by the receiver antenna.

8. The antenna-based radio detection system of claim 7, wherein the at least 30dB increase in SNR is achieved across a frequency band of at least 1.5 GHz.

9. The antenna-based radio detection system of any one of the preceding claims, wherein at least one geometric characteristic of the plurality of EMR absorbing elements is specifically adapted to a transmitting and/or receiving wavelength band to reduce or eliminate the induction of surface currents. 31

10. The antenna-based radio detection system of claim 9, further comprising smart material for controllably adapting the at least one geometric characteristic.

11. The antenna-based radio detection system of claim 9 or claim 10, wherein the at least one geometric characteristic includes a periodical or non-periodical feature of the EMR absorbing structure.

12. The antenna-based radio detection system of any one of the preceding claims, wherein the plurality of EMR absorbing elements form a periodic structure.

13. The antenna-based radio detection system of any one of the preceding claims, wherein the plurality of EMR absorbing elements form a non-periodic structure.

14. The antenna-based radio detection system of any one of the preceding claims, wherein the plurality of EMR absorbing elements form a fractal structure.

15. The antenna-based radio detection system of any one of the preceding claims, wherein each one of the plurality of EMR absorbing elements has one of the following geometric characteristics: a rectangular cross-section, a trapezoidal cross-section, a triangular cross-section, a cross-section that is widening in direction of the scene, a T-shaped cross-section, and a V-shaped cross-section.

16. The antenna-based radio detection system of any one of the preceding claims, further comprising a common ground plane, wherein the EMR absorbing elements are directly coupled to the common conductive ground plane and protrude beneath the common conductive ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna. 32

17. The antenna-based radio detection system of claim 16, wherein the EMR absorbing elements are directly coupled to the common conductive ground plane and protrude above the common conductive ground plane, in direction of the electromagnetic radiation emitted by the transmitter antenna.

18. The antenna-based radio detection system of any one of the claims 16-17, wherein at least two of the plurality of EMR absorbing elements protrude above the common ground plane, in a direction of the electromagnetic radiation emitted by the transmitter antenna; and wherein at least another two of the EMR absorbing elements protrude beneath the common ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna.

19. The antenna-based radio detection system of the claims 16 to 18, wherein the EMR absorbing elements are arranged to constitute part of the common ground plane.

20. The antenna-based radio detection system of any one of the claims 16 to 19, wherein the EMR absorbing elements are solid elements.

21. The antenna-based radio detection system of any one of the preceding claims, wherein upon operation of the system the transmitter antenna continuously transmits electromagnetic radiation, and the receiver antenna continuously receives electromagnetic radiation to generate the reflection-based signals.

22. The antenna-based radio detection system of any one of the preceding claims, comprising a Frequency-Modulated Continuous Wave (FMCW) radar. 33

23. The antenna-based radio detection system of any one of the preceding claims, wherein the transmitter antenna is spatially separated from the receiver antenna at a distance not exceeding 190 mm.

24. The antenna-based radio detection system of any one of the preceding claims, wherein at least two components forming the system are assembly components.

25. The antenna-based radio detection system of any one of the preceding claims, wherein various components forming the system are configured to be housed in a casing.

26. The antenna-based radio detection system of any one of the preceding claims, wherein each two neighboring EMR absorbing elements are spaced apart from each other and further have a length that exceeds the dimensions of the at least one transmitter antenna and the at least one receiver antenna extending in direction of the longitudinal axis of EMR absorbing elements.

27. A method for detecting objects in a scene using an antenna-based radio detection system, the method comprising: transmitting, by at least one transmitter antenna arranged at a first location, electromagnetic radiation into free space towards the scene; reducing the induction of surface currents induced by the transmission of electromagnetic radiation into the free space; receiving, by at least one receiver antenna, at a second location different from the first location, electromagnetic radiation reflections reflected by at least one object from the scene; and generating, based on the received electromagnetic radiation reflections, ref4lection- based signals; wherein the EMR absorbing elements have a longitudinal axis X extending in a second direction which is about perpendicular to a first direction extending along an axis Y between the at least one transmitter antenna and the at least one receiver antenna, 34 and further extending about perpendicular with respect to a direction of free space emission of EMR radiation towards the scene; wherein each one of the plurality of absorbing elements is arranged at a different position along the first direction extending between the at least one transmitter antenna and the at least one receiver antenna; and wherein reducing the induction of surface currents is achieved by an electromagnetic radiation (EMR) absorbing structure formed by a plurality of EMR absorbing elements disposed between the first and the second location such that the reflection-based signals are stronger than received surface currents.

28. The method of claim 27 wherein a recess formed by two neighboring EMR absorbing elements has a height that corresponds to about a quarter of a wavelength of a center frequency of the surface currents J . S

29. The method for detecting objects in a scene of claim 27, wherein the transmitter and the receiver antenna are separated from each other by a rigid plate structure.

30. The method for detecting objects in a scene of any one of the claims 27 to 29, wherein a reduction in the induction of surface currents enables analyzing a comparatively weak reflection-based signals generated by the receiver antenna.

31. The method for detecting objects in a scene of any one of claims 27 to 30 wherein the induction of surface currents is configured to be reduced below a threshold by the EMR absorbing structure.

32. The method for detecting objects in a scene of any one of the claims 27 to 31 wherein the EMR absorbing structure is configured to increase a Signal Noise to Ratio (SNR) between the reflection-based signals and the surface currents, compared to antenna- based radio detection systems lacking the EMR absorbing structure. 35

33. The method for detecting objects in a scene of any one of the claims 27 to 32, wherein the EMR absorbing structure is configured to provide at least 30dB increase in SNR between the reflection-based signals and the surface currents picked up by the receiver antenna.

34. The method for detecting objects in a scene of any one of the claims 27 to 33 wherein the at least 30dB increase in SNR is achieved across a frequency band of at least 1.5 GHz.

35. The method for detecting objects in a scene of any one of the claims 27 to 34, wherein at least one geometric characteristic of the plurality of EMR absorbing elements is specifically adapted to a transmitting and/or receiving wavelength band to reduce or eliminate the induction of surface currents.

36. The method for detecting objects in a scene of any one of the claims 27 to 35, wherein the at least one geometric characteristic is controllably adaptable.

37. The antenna-based radio detection system of claim 35 or claim 36, wherein the at least one geometric characteristic includes a periodical or non-periodical feature of the EMR absorbing structure.

38. The method for detecting objects in a scene of any one of the claims 27 to 37, wherein the plurality of EMR absorbing elements form a periodic structure.

39. The method for detecting objects in a scene of any one of the claims 27 to 37, wherein the plurality of EMR absorbing elements form a non-periodic structure. 36

40. The method for detecting objects in a scene of any one of the claims 27 to 39, wherein the plurality of EMR absorbing elements form a fractal structure.

41. The method for detecting objects in a scene of any one of the claims 27 to 40, wherein each one of the plurality of EMR absorbing elements has one of the following geometric characteristics: a rectangular cross-section, a trapezoidal cross-section, a triangular cross-section, a cross-section that is widening in direction of the scene, a T-shaped cross-section, and a V-shaped cross-section.

42. The method for detecting objects in a scene of any one of the claims 27 to 41, further comprising a common ground plane, wherein the EMR absorbing elements are directly coupled to the common ground plane and protrude beneath the common ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna.

43. The method for detecting objects in a scene of any one of the claims 27 to 41, wherein the EMR absorbing elements are directly coupled to the common ground plane and protrude above the common ground plane, in direction of the electromagnetic radiation emitted by the transmitter antenna.

44. The method for detecting objects in a scene of any one of the claims 27 to 41, wherein at least two of the plurality of EMR absorbing elements are directly coupled to the common ground plane and protrude above the common ground plane, in a direction of the electromagnetic radiation emitted by the transmitter antenna; and wherein at least another two of the EMR absorbing elements are directly coupled to the common ground plane and protrude beneath the common ground plane, in a direction opposite to the electromagnetic radiation emitted by the transmitter antenna. 37

45. The method for detecting objects in a scene of any one of the claims 27 to 44, wherein the EMR absorbing elements are arranged to constitute part of the common ground plane.

46. The method for detecting objects in a scene of any one of the claims 27 to 45, wherein the EMR absorbing elements are solid elements.

47. The method for detecting objects in a scene of any one of the claims 27 to 46, wherein upon operation of the system the transmitter antenna transmits electromagnetic radiation, and the receiver antenna receives electromagnetic radiation to generate the reflection-based signals.

48. The method for detecting objects in a scene of any one of the claims 27 to 47, wherein the transmitter antenna is spatially separated from the receiver antenna at a distance not exceeding 190 mm.

49. The method for detecting objects in a scene of any one of the claims 27 to 48, wherein at least two components forming the system are assembly components.

50. The method for detecting objects in a scene of any one of the claims 27 to 49, wherein each two neighboring EMR absorbing elements are spaced apart from each other and further have a length that exceeds the dimensions of the at least one transmitter antenna and the at least one receiver antenna extending in direction of the longitudinal axis of EMR absorbing elements. 38