SE543769C2 - A scanning antenna comprising several stacked microwave lenses - Google Patents

A scanning antenna comprising several stacked microwave lenses

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Publication number
SE543769C2
SE543769C2 SE1951395A SE1951395A SE543769C2 SE 543769 C2 SE543769 C2 SE 543769C2 SE 1951395 A SE1951395 A SE 1951395A SE 1951395 A SE1951395 A SE 1951395A SE 543769 C2 SE543769 C2 SE 543769C2
Authority
SE
Sweden
Prior art keywords
antenna
lens
microwave
scanning
lenses
Prior art date
Application number
SE1951395A
Other languages
Swedish (sv)
Other versions
SE1951395A1 (en
Inventor
Iman Vakili
Original Assignee
Sencept Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sencept Ab filed Critical Sencept Ab
Priority to SE1951395A priority Critical patent/SE543769C2/en
Priority to EP20820130.1A priority patent/EP4070129A1/en
Priority to PCT/EP2020/084697 priority patent/WO2021110947A1/en
Publication of SE1951395A1 publication Critical patent/SE1951395A1/en
Publication of SE543769C2 publication Critical patent/SE543769C2/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/06—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/42—Simultaneous measurement of distance and other co-ordinates
    • G01S13/426—Scanning radar, e.g. 3D radar
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/66—Radar-tracking systems; Analogous systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
    • G01S7/032—Constructional details for solid-state radar subsystems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/32—Adaptation for use in or on road or rail vehicles
    • H01Q1/3208—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used
    • H01Q1/3233—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
    • H01Q15/06—Refracting or diffracting devices, e.g. lens, prism comprising plurality of wave-guiding channels of different length
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/0006—Particular feeding systems
    • H01Q21/0031—Parallel-plate fed arrays; Lens-fed arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/007—Antennas or antenna systems providing at least two radiating patterns using two or more primary active elements in the focal region of a focusing device
    • H01Q25/008—Antennas or antenna systems providing at least two radiating patterns using two or more primary active elements in the focal region of a focusing device lens fed multibeam arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/24—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/24—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
    • H01Q3/245—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching in the focal plane of a focussing device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/44—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element
    • H01Q3/46—Active lenses or reflecting arrays
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S2013/0236—Special technical features
    • G01S2013/0245—Radar with phased array antenna
    • G01S2013/0263—Passive array antenna

Landscapes

  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Security & Cryptography (AREA)
  • Aerials With Secondary Devices (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)

Abstract

The invention relates to a scanning antenna (1) comprising several stacked microwave lenses (2), each microwave lens comprising a first lens contour (7) and a second lens contour (8) arranged opposite to the first lens contour. The first lens contour comprises input ports (3) and the second lens contour comprises output ports (5), and each microwave lens (2) is sandwiched between ground layers (4). The output ports (5) of each microwave lens (2) are located at the same position along the respective second lens contour (8), with respect to the other stacked microwave lenses (2), the input ports (3) of each microwave lens (2) are located at different positions along the respective first lens contour (7), with respect to the other stacked microwave lenses (2), and the output ports (5) of the microwave lenses (2) are coupled to a common antenna output (10). This provides a compact scanning antenna (1) with high resolution.

Description

The present invention relates to a scanning antenna and to a radar systemand a scanning device comprising such a scanning antenna.
BACKGROUND OF THE INVENTION Radar systems are extensively used for detecting location, velocity andrange of a target, for example in automotive sensing, mining, robotics anddrones, by emitting electromagnetic waves and measuring the reflectedsignals. Common automotive radars on the market use a frequencymodulated continuous wave (FMCW) scheme to find the range and velocity oftargets. These radars have multiple transmitting and receiving antennas. Thetransmitting antennas propagate the radar signal in the radar field-of-view(FOV) and the receiving antennas collect the reflected signals from targets.By comparing the signal phase at different receiving antennas and performingspatial Fourier transform or similar techniques, the angle of the target isestimated. These methods, in which signal processing is used to estimate thedirection of arrival, are called digital beam forming (DBF).
The combined need for more low-level processing, on the one hand,and high amount of data, on the other hand, demand complex and costlyprocessing units. Radars in the past made use of mechanical scanning usingpencil beam or fan beam antennas and a rotational stage to control the scanangle. These radars are usually bulky, cost inefficient, and suffer fromvibrations in extreme conditions. Another known type of radar system iselectronically steering radars. These radars use phase shifters to scan theradar beam. The use of phase shifters is not appropriate in wide-bandapplications due to their narrow-band nature.
Microwave lenses have been studied for radar applications, mainly dueto the wide-band and true time-delay (TTD) nature of these structures,making them an ideal choice for scanning applications. These lenses are realizable at millimeter-waves. However, it would be advantageous to improvethe resolution of radar systems using such lenses without compromising theoverall scanning performance of the lens due to e.g. an increased side lobelevel, nor its compactness.
SUMMARY OF THE INVENTION An object of the present invention is to overcome, or at least lessen theabove-mentioned problems. A particular object is to provide a compactscanning antenna with an improved resolution.
To better address this concern, in a first aspect of the invention there ispresented a scanning antenna comprising several stacked microwave lenses,each microwave lens comprising a first lens contour and a second lenscontour arranged opposite to the first lens contour. The first lens contourcomprises input ports and the second lens contour comprises output ports,and each microwave lens is sandwiched between ground layers. The outputports of each microwave lens are located at the same position along therespective second lens contour, with respect to the other stacked microwavelenses, the input ports of each microwave lens are located at differentpositions along the respective first lens contour, with respect to the otherstacked microwave lenses, and the output ports of the microwave lenses arecoupled to a common antenna output.
The input ports can be connected to a control system consisting ofmultiple high-speed switches. By exciting a specific input port, or several inputports, the propagated wave inside the lens cavity, i.e. between the first andthe second lens contours, reaches the output ports at different time instants,resulting in a linear progressive phase shift across the output ports. A flatmicrowave lens used for radar applications is generally capable of providingthe same number of beams as the number of input ports on the first contour.ln order to improve the resolution and reduce the step size between thebeams, the distance between the input ports needs to be reduced. Thisresults in a significant increase in mutual coupling between the input ports,which, as a consequence, deteriorates the overall scanning performance andincreases the side lobe level. Alternatively, the lens size can be increased and input ports added. This is however inappropriate when compactness ofthe antenna is desirable.
Using several stacked microwave lenses with input ports of each firstlens contour at different positions with respect to the other stacked microwavelenses, i.e. having the input ports slightly shifted in position with respect to theadjacent microwave lens or lenses, and coupling the output ports of eachmicrowave lens to a common antenna output, allows reducing the step sizebetween the beams while keeping the overall lens size constant. That is,angles that are not covered by one of the several stacked microwave lensescan be covered by another one of the several stacked microwave lenses,such that each microwave lens covers different scan angles. This results inan improved resolution of the scanning antenna. Further, by exciting eitherone or several of the input ports of the scanning antenna, an arbitrary shapedantenna pattern can be produced to adaptively scan the environment. ln accordance with an embodiment of the scanning antenna themicrowave lenses are Rotman lenses. The Rotman lens is a type ofmicrowave beamforming network which is robust, simple to fabricate and is alow-cost antenna. lt is further a planar lens that has the advantage ofscanning wide angles over a wide frequency bandwidth by passively shiftingthe input phase. lts geometry is specially designed to produce true timedelays for the output ports to provide multiple beams in certain directions.Thereby, this provides a robust low-cost scanning antenna with highresolution. ln accordance with an embodiment of the scanning antenna, theground layers comprise a bottom ground layer, a top ground layer, and atleast one intermediate ground layer. Further, the top ground layer and the atleast one intermediate ground layer each comprises apertures for couplingeach of the output ports to the common antenna output. One aperture isprovided for each output port of each of the stacked microwave lenses. Thisallows transmitting the signal from each microwave lens to the commonantenna output without interfering with the signal from the other stackedmicrowave lenses. ln accordance with an embodiment of the scanning antenna, the topground layer comprises the common antenna output. The output ports ofeach microwave lens are coupled to apertures of the ground layer directlyadjacent thereto in the direction towards the top ground layer. The aperturesextend through the subsequent layers up to the top ground layer. Thisprovides a flat antenna in which the top ground layer comprises the antennaoutput. The scanning antenna may be produced in any suitable way, forexample by additive manufacturing, milling, substrate integrated waveguidetechnology or printed circuit board techniques.ln accordance with an embodiment of the scanning antenna, the common antenna array comprises rows of apertures, the number of rowscorresponding to the number of stacked microwave lenses of the scanning antenna.
According to a second aspect of the invention, there is presented aradar system comprising a scanning antenna as disclosed herein. lnaccordance with an embodiment of the radar system, the scanning antenna isa transmitting antenna. This allows increasing the resolution in one plane, e.g.elevation or azimuth, of the radar image obtainable by the radar system. ln accordance with an embodiment of the radar system, a receivingantenna of the radar system comprises a scanning antenna as disclosedherein. ln accordance with an embodiment of the radar system, a receivingantenna and a transmitting antenna of the radar system each comprises ascanning antenna as disclosed herein. This allows lens scanning to beapplied in two planes, e.g. azimuth and elevation, thereby further improvingthe resolution of the radar system. This also allows reducing the number ofreceiving channels and transmitting channels required on the radartransceiver of the radar system, providing a reduced system complexity. ln accordance with an embodiment, the radar system further comprisessecond and third transmitting antennas, different from the scanning antennadisclosed herein, configured to generate a complementary common antennaoutput. ln an embodiment, the second and third transmitting antennas arearranged with a half-wavelength spacing in the same plane as the scanning of the scanning antenna is performed. These transmitting antennas can beactivated sequentially or adaptively at each lens scan angle to improve theangular estimation accuracy. This allows detecting the exact angle of a targetwithin a scanning direction of the scanning antenna. ln an embodiment, theangular estimation accuracy may be less than half a degree. ln accordance with an embodiment of the radar system, the secondand third transmitting antennas are single antenna elements. The singleantenna elements may for example be patch antennas, slot antennas, orslotted waveguides. ln accordance with an embodiment, the radar system further comprisessecond and third receiving antennas, different from the scanning antennas. ln accordance with an embodiment, the second and third receivingantennas are single antenna elements. As an example only, the singleantenna element may be patch antennas, slot antennas, or slottedwaveguides.
According to a third aspect of the invention, there is provided ascanning device comprising a scanning antenna as disclosed herein. lnaccordance with an embodiment, the scanning device is at least one of atelecommunication transceiver, an electromagnetic transmitter and anelectromagnetic receiver.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail and with referenceto the appended drawings in which: Fig. 1 is a schematic view of an embodiment of a scanning antennaaccording to a first aspect of the present invention; Fig. 2 is a block diagram of an embodiment ofa radar systemaccording to a second aspect of the present invention; and Fig. 3 is a block diagram of an embodiment of a radar systemaccording to a second aspect of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplifying embodimentsof the invention are shown. The present invention may, however, beembodied in many different forms and should not be construed as limited tothe embodiments set forth herein; rather, these embodiments are provided forthoroughness and completeness, and to fully convey the scope of theinvention to the skilled addressee. Like reference characters refer to likeelements throughout.
With reference to Fig. 1, there is provided an embodiment of ascanning antenna 1 comprising several stacked microwave lenses 2. Eachmicrowave lens 2 comprises a lens substrate 12 and a conductive patternarranged in the lens substrate 12. ln this exemplifying embodiment, themicrowave lenses 2 are Rotman lenses. However, providing other flatmicrowave lenses suitable for scanning applications is also possible withinthe concept of the present invention. Further, in the embodiment shown inFig. 1, the number of stacked microwave lenses 2 is three. These may hereinbe referred to as first, second and third microwave lens 2', 2", 2"'. However,providing a scanning antenna 1 comprising more than three stackedmicrowave lenses 2 is also possible and may be advantageous for furtherincreasing the resolution provided by the scanning antenna 1.
Each Rotman lens 2 comprises a lens substrate 12 and a conductivepattern arranged therein. The conductive pattern comprises a first lenscontour 7 and a second lens contour 8, arranged opposite to the first lenscontour 7. The space between the first lens contour 7 and the second lenscontour 8 is hereinafter referred to as a lens cavity 9. The first lens contour 7comprises input ports 3, for the Rotman lens commonly also referred to asbeam ports. The second lens contour 8 comprises output ports 5, commonlyalso referred to as array ports. When used in a radar system, the input ports 3are connected to a control system through transmission lines, which controlsystem comprises multiple high-speed switches for selecting one or several ofthe lines at a time for sending a signal and thereby directing the beamtowards a specific direction. By exciting a specific input port 3, the propagated wave inside the lens cavity 9 reaches the output ports 5 at different timeinstants. This results in a linear progressive phase shift across the outputports 5. A correction of phases can be implemented at the output ports 5 ofthe Rotman lens 2 to improve the phase steering accuracy.
The number of discrete beams that can be provided by the Rotmanlens 2 is generally limited by its number of input ports 3. ln the exemplifyingembodiment of Fig. 1, the number of input ports 3 provided at each Rotmanlens 2 is five. However, providing a microwave lens 2 comprising a differentnumber of input ports 3, such as for example four or more than five, is alsopossible within the concept of the present invention.
The input ports 3 are positioned along the first lens contour 7. Further,the position of each input port 3 along the first lens contour 7 of e.g. thesecond Rotman lens 2” is different from the position of the correspondinginput port 3 at the first lens contour 7 of the first Rotman lens 2'. The positionof each input port 3 of the third Rotman 2"' lens is further different from theposition of the corresponding input port 3 of the first and second Rotmanlenses 2', 2". That is, the input ports 3 of each Rotman lens 2 is shifted inposition along the first lens contour 7 with respect to the other stackedRotman lenses 2. This provides a constant phase shift at each of the outputports 5 of the scanning antenna 1.
The output ports 5 of each of the stacked Rotman lenses 2 are coupledto a common antenna output 10. More particularly, each of the output ports 5of each Rotman lens 2 is connected via a respective transmission line to arespective antenna element 11. The antenna elements 11 may for examplebe microstrip patches, dipoles, slotted waveguides and/or Vivaldi antennas.
Each Rotman lens 2 of the scanning antenna 1 is sandwiched byground layers 4. ln the embodiment shown in Fig. 1, the scanning antennacomprises three stacked Rotman lenses 2 and four ground layers 4. Theground layers comprise a bottom ground layer 4', at least one intermediateground layer 4", and a top ground layer 4"'. The scanning antenna shown inthe exemplifying embodiment of Fig. 1 comprises two intermediate groundlayers 4". The stacked Rotman lenses 2 of the exemplifying embodimentshown are hereinafter referred to as first, second and third Rotman lenses 2', 2", 2"' where the first Rotman lens 2' is arranged adjacent to the bottomground layer 4', the third Rotman lens 2"' is arranged adjacent to the topground layer 4"', and the second Rotman lens 2" is arranged therebetween,between the two intermediate ground layers 4”. Between each ground layer 4and Rotman lens 2, a dielectric substrate is further provided, not shown inFig. 1 for reasons of clarity.
The first Rotman lens 2' is configured to support the transverseelectromagnetic (TEM) mode between the first lens 2' and the bottom groundlayer4ï The intermediate ground layers 4" and the top ground layer 4"' eachcomprises apertures 6. The lowermost intermediate ground layer 4"comprises a row of apertures 6, the number of apertures 6 corresponding tothe number of output ports 5 of the first Rotman lens 2'. Thereby, each of theoutput ports 5 of the first Rotman lens 2' is coupled to one of the apertures 6of the lowermost intermediate ground layer 4". The apertures 6 of thelowermost intermediate ground layer 4" are aligned with correspondingapertures through all the subsequent ground layers 4, lens substrates 12 anddielectric substrates up to the top ground layer 4"' and therethrough.Correspondingly, output ports 5 of the second Rotman lens 2" are coupled toapertures 6 of the uppermost intermediate ground layer 4". The uppermostintermediate ground layer 4" comprises a first row of apertures 6, coupled tothe output ports 5 of the first Rotman lens 2', and a second row of apertures6, coupled to the output ports of the second Rotman lens 2". As with thelowermost intermediate ground layer 4", the second row of apertures 6 of theuppermost intermediate ground layer 4" extend through the lens substrate 12of the third Rotman lens 2"', the subsequent dielectric substrate and the topground layer 4"', and therethrough.
Finally, the top ground layer 4"' comprises a first row of apertures 6coupled to the output ports 5 of the first Rotman lens 2', a second row ofapertures 6 coupled to the output ports 5 of the second Rotman lens 2", anda third row of apertures 6 coupled to the output ports 5 of the third Rotmanlens 2"'. The apertures 6 form open ended waveguides through the differentlayers of the scanning antenna 1. The first, second and third rows of apertures 6 of the top ground layer 4"' thereby form a common antennaoutput 10 of the scanning antenna 1. The top ground layer 4"' thus comprisesthe common antenna output 10.
Although not shown, the conductive pattern of the Rotman lenses 2, orother type of microwave lenses of the scanning antenna 1, may compriseseveral dummy ports positioned along each side of the lens substrate 12 thatcan absorb lens spillover and thus reduce multiple reflections and/or standingwaves that can deteriorate the performance of the scanning antenna 1.
The scanning antenna 1 can be used in a radar system as atransmitting antenna. Radar systems generally comprises a transceiver forgenerating a radar signal. The transceiver sends the signal to a control unitwhich is in communication with the conductive pattern of the scanningantenna 1. A switch system is used to direct the beam towards a specificdirection. More particularly, the switch system of the control unit connects theradar signal to one or several of the input ports 3 of the scanning antenna 1.The signal is propagated through the lens cavity 9 and reaches the outputports 5 at different time instants. The output ports 5 are connected torespective antenna elements 11 which can transmit the radio signal, generallya radio frequency signal, to a particular direction. Due to the signal reachingthe output port 5 at different time instants, it also reaches the individualantenna elements 11 at different instances of time. This can result in phaseshifts between the different received signals, generating a phase front acrossthe antenna elements 11 to radiate a beam from the common antenna output10 in a certain direction associated with the beam originating at the input port3. By switching input port or ports 3, the beam radiating from the commonantenna output 10 can be steered in different directions. Either one or severalof the input ports 3 can thus be chosen to produce an arbitrary shapedantenna pattern to adaptively scan the environment.
Due to the scanning antenna 1 comprising several stacked microwavelenses 2, and comprising a common antenna output 11, the step sizebetween beams is reduced. Thereby, the number of scan angles is increased,improving the overall resolution of the scanning antenna 1. ln a corresponding manner, the scanning antenna 1 can also be usedin a radar system as a receiving antenna.
With reference now to Fig. 2, there is presented a radar system 20comprising a scanning antenna 1 as previously described. The scanningantenna 1 is generally configured to scan horizontally or vertically, i.e. one ofthe azimuth and the elevation planes. The radar system 20 further comprisesa second transmitting antenna 22 and a third transmitting antenna 23. Thesecond transmitting antenna 22 and the third transmitting antenna 23 arespaced half a wavelength in the same dimension as the main extension of thelens 2 of the scanning antenna 1. Providing additional transmitting antennasis also possible within the concept of the present invention.
The radar system 20 of the exemplifying embodiment of Fig. 2 furthercomprises four receiving antennas 25. The receiving antennas 25 aregenerally spaced by half a wavelength in a direction orthogonal to that of themicrowave lens 2 of the scanning antenna 1. According to anotherembodiment, the radar system 20 comprises more than four receivingantennas 25. The radar system 20 further comprises a radar transceiver 26.The radar transceiver 26 comprises multiple transmitting and receivingchannels to generate radar signals and receive the reflections by means ofmultiple receivers. The radar transceiver 26 can generate signals of any ofthe types frequency modulation continuous wave (FMCW), fast chirpmodulation, modulated square pulses, or phase modulation continuous wave(PMCW). FMCW signals can for example be generated at a carrier frequencyof for example 77/79 GHz.
The radar system 20 also comprises a control unit 24. ln anembodiment, the control unit comprises pin-diode or micro-electromechanicalsystems (MEMS) switches with multiple input and multiple output. ln use, the radar transceiver 26 transmits the generated signals to thecontrol unit 24 via one or more transmitting channels. The control unit 24comprises outputs connected to the input ports 3 of the scanning antenna 1and comprises multiple high-speed switches for connecting the transmittingchannel from the radar transceiver 26 to the input ports 3 of the scanningantenna 1 sequentially. Using amplitude tapering along the common antenna 11 output 10 of the scanning antenna 1, sidelobe levels of the antenna outputare low relative to the level of the main lobe. According to an embodiment, thedetected target falls within the half-power beam width of the scanningantenna 1. An input of the control unit 24 is further connected to the secondand third transmitting antennas 22, 23, which are spaced half a wavelengthfrom each other. The second and third transmitting antennas 22, 23 areactivated sequentially at each lens scan angle. The output ports 5 of thescanning antenna 1 are connected to the common antenna output 10, whichscans different directions based on choosing different input ports 3 of theseveral stacked lenses 2. The propagated radar signal hits a target and aportion thereof is reflected back towards the radar and collected by thereceiving antennas 25. The second and third transmitting antennas 22, 23generate a detectable signal when reflected on the target and collected by thereceiving antennas 25, allowing to detect the angle of the target within theillumination direction of the scanning antenna 1 with a high accuracy. ln anembodiment, the angular estimation accuracy is as high as less than half adegree.
The radar signal received at the receiving antennas 25 is down-converted and sampled in the radar transceiver 26. The signal can then befurther transferred to a signal processing unit, not shown in the block diagramof Fig. 2, to perform 4D radar processing to generate a radar image andestimate the position of the target in three dimensions, and its velocity as thefourth dimension. The transmitting antennas of the radar system shown inFig. 2, i.e. the scanning antenna 1, the second transmitting antenna 22 andthe third transmitting antenna 23 provide angular estimation of a target in oneplane, e.g. azimuth. The angle of the target in the other plane, e.g. elevation,is determined using classical digital beam forming by estimating the phasedifference between the receiving antennas 25. The radar transceiver of theexemplifying embodiment of Fig. 2 comprises four receiving channels and twotransmitting channels. However, providing a radar transceiver with a differentnumber of receiving and transmitting channels is also possible within theconcept of the present invention. 12 With reference now to Fig. 3, there is provided a radar system 30comprising a first scanning antenna 1 as a transmitting antenna 31 and asecond scanning antenna 1 as a receiving antenna 35. Providing scanningantennas 1 both for transmitting and receiving the radar signal allowsscanning to be applied to two planes, i.e. e|evation and azimuth. ln thisexemplifying embodiment, the radar transceiver 36 comprises two receivingchannels and two transmitting channels. The transmitting and receivingchannels are connected to two control units 34. One of the two control units34 is further connected to second and third transmitting antennas 32, 33 andthe other control unit 34 is further connected to second and third receivingantennas 37, 38. The second and third transmitting and receiving antennas32, 33, 37, 38 are provided to improve the angular accuracy by estimating thephase difference between the channels.
While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and description are to beconsidered illustrative or exemplary and not restrictive. The invention is notlimited to the disclosed embodiments. For instance, a radar system asdescribed with respect to Figs. 2 and 3 may be provided comprising, insteadof the scanning antenna 1 as transmitting antenna and/or receiving antenna,a scanning antenna comprising only one microwave lens, such as a Rotmanlens. ln this radar system, the second and third transmitting antennas and/orsecond and third receiving antennas provide improved angular accuracy ofthe target.
The scanning antenna 1, although having been described mainly foruse in radar systems, can also be used for other scanning applications suchas for telecommunication transceivers, and any electromagnetic transmitter orreceivers. Thus, according to another aspect of the present invention there isprovided a scanning device comprising the scanning antenna 1.
Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimed invention, from astudy of the drawings, the disclosure, and the appended claims. ln the claims,the word "comprising" does not exclude other elements or steps, and the 13 indefinite article "a" or "an" does not exclude a plurality. The mere fact thatcertain measures are recited in mutually different dependent claims does notindicate that a combination of these measured cannot be used to advantage.Any reference signs in the claims should not be construed as Iimiting the scope.

Claims (2)

1. A scanning antenna (1) comprising several stacked microwave lenses(2), each microwave lens (2) comprising a first lens contour (7) anda second lens contour (8) arranged opposite to the first lens contour(7), the first lens contour (7) comprising input ports (3) and the secondlens contour (8) comprising output ports (5), and each microwave lens(2) being sandwiched between ground layers (4), wherein the output ports (5) of each microwave lens are located at thesame position along the respective second lens contour (8) withrespect to the other stacked microwave lenses (2); the input ports (3) of each microwave lens (2) are located atdifferent positions along the respective first lens contour (7), withrespect to the other stacked microwave lenses (2); and the output ports (5) of the microwave lenses (2) are coupled to acommon antenna output (10). _ The scanning antenna (1) according to claim 1, wherein the microwave lenses (2) are Rotman lenses. The scanning antenna (1) according to claim 1 or 2, wherein theground layers (4) comprise a bottom ground layer (4'), a top groundlayer (4"'), and at least one intermediate ground layer (4"), wherein thetop ground layer (4"') and the at least one intermediate ground layer(4") comprises apertures (6) for coupling each of the output ports (5) tothe common antenna output (10). _ The scanning antenna (1) according to claim 3, wherein the top ground layer (4"') comprises the common antenna output (10). _ The scanning antenna (1) according to any one of the preceding claims, wherein the common antenna output (10) comprises rows ofapertures (6), the number of rows corresponding to the number ofstacked microwave lenses (2) of the scanning antenna (1). _ A radar system comprising a scanning antenna (1) according to any one of the preceding claims. _ The radar system according to claim 6, wherein the scanning antenna (1) is a transmitting antenna. _ The radar system according to claim 6 or 7, wherein a receiving antenna of the radar system comprises a scanning antenna (1)according to any one of c|aims 1-5. _ The radar system (20) according to claim 6 or 7, further comprising second and third transmitting antennas (22, 23), different from thescanning antenna (1 ), configured to generate a complementarycommon antenna output. 10_The radar system (20) according to claim 9, wherein the second and third transmitting antennas (22, 23) are single antenna elements. 11_The radar system (30) according to c|aims 8 and 9, further comprising second and third receiving antennas (37, 38), different from thescanning antenna (1). 12_The radar system (30) according to claim 11, wherein the second and third receiving antennas (37, 38) are single antenna elements. 13_A scanning device comprising a scanning antenna (1) according to any one of c|aims 1-5. 14_The scanning device according to claim 13, wherein the scanning device is at least one of a telecommunication transceiver, an electromagnetic transmitter and an electromagnetic receiver.
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PCT/EP2020/084697 WO2021110947A1 (en) 2019-12-04 2020-12-04 Scanning antenna

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