Radar front end and radar system

Abstract

A radar front end is disclosed, the radar front end comprising: an antenna array, each antenna coupled to a first input of a respective one of a plurality of directional couplers, and the antenna array comprising an end antenna coupled to a first input of a first directional coupler; a first directional coupler having an output configured to be coupled to a receiver unit; the remaining directional couplers each having an output coupled to an input of a respective delay line; wherein the output of each delay line is coupled to the second input of a corresponding adjacent directional coupler. A radar system including the radar front end is also disclosed.

Description

Technical Field

[0001] The present disclosure relates to radar front ends. In particular, it relates to radar front ends with multiple receiving antennas, wherein the components are passive. Background Art

[0002] In order to achieve high resolution, conventional radars include multiple receive antennas spaced apart. Transmitted radar pulses, which may be configured as "chirps" in which the carrier frequency varies, are transmitted from the transmit antennas, and reflections from the target are received as corresponding reflected pulses at each of the multiple receive antennas. The arrival time at a separate receive antenna typically varies depending on the angle of arrival of the reflected pulse. Using well-known but computationally intensive methods, the reflected signals received at each of the antennas can be processed to determine the exact angle of arrival. Deconvolution of the contributions of the individual receive antennas may require intensive computations, and this typically limits the fields of application that utilize this high-resolution radar. It would be desirable to provide an alternative front end that can reduce costs and thereby increase the number of fields of application in which high-resolution radars can be beneficially used, such as for gesture recognition. Summary of the invention

[0003] According to a first aspect of the present disclosure, a radar front end is provided, the radar front end comprising: an antenna array, each antenna coupled to a first input of a corresponding directional coupler among a plurality of directional couplers, and the antenna array comprising an end antenna coupled to a first input of a first directional coupler; the first directional coupler having an output configured to be coupled to a receiver unit; the remaining directional couplers each having an output coupled to an input of a corresponding delay line; wherein the output of each delay line is coupled to a second input of a corresponding adjacent directional coupler. The delay line provides time separation between reflected radar signals received from each antenna. This can greatly simplify signal processing at a relatively low cost.

[0004] In one or more embodiments, the radar front end is configured to sequentially couple respective reflected radar pulses received at each of the antenna arrays to the receiver unit. The sequencing will depend on the configuration arrangement of the delay lines and couplers.

[0005] In one or more embodiments, the antenna is configured to receive radar signals having a carrier frequency in the range of 10 GHz to 100 GHz. These radar frequencies are particularly suitable for short-range radar applications such as gesture recognition. They are also suitable for relatively low-cost manufacturing processes such as stripline waveguides.

[0006] In one or more embodiments, each of the antenna arrays receives reflected radar pulses, wherein the reflected radar pulses overlap in time, and wherein the delay line delays the reflected radar pulses such that they do not overlap in time at the output of the first directional coupler. Providing non-overlap significantly simplifies subsequent processing in the receiver unit.

[0007] In one or more embodiments, the reflected radar pulse has a duration in the range between 10 μs and 1 ms. Specifically, the transmitted and thus reflected radar pulse should have a duration that allows it to include relevant appropriate features such as frequency chirp. In one or more embodiments, each delay line introduces a delay between 10 μs and 1 ms. Providing a delay at least equal to the duration of the transmitted radar signal facilitates non-overlapping time separation including the received reflected radar signals. In other embodiments, each delay line introduces a delay between 10 ns and 1 μs, which may correspond to a distance range between 5 m and 300 m.

[0008] In one or more embodiments, the antenna array is a linear array. In other embodiments, the antenna array is a two-dimensional array. The array can be a regular array or an irregular array.

[0009] In one or more embodiments, the plurality of directional couplers are a plurality of rat-race couplers. Other forms of directional couplers may be used in place of rat-race couplers. In one or more embodiments, the first input of each directional coupler is a corresponding rat-race first input, the second input of each directional coupler is a corresponding rat-race second input, and the output of each directional coupler is a corresponding rat-race sigma output.

[0010] In one or more embodiments, the antennas of the array are equally spaced and the delay lines are configured to provide equal propagation delays.

[0011] In one or more embodiments, the radar front end further comprises a transmit antenna, wherein the transmit antenna is aligned to the linear array of antennas to form an extended array. Including a transmitter antenna in the front end, and particularly in the radar antenna array, can simplify manufacturing and / or reduce manufacturing costs.

[0012] In one or more embodiments, the transmit antenna is configured to transmit a radar chirp, each antenna of the antenna array is arranged to receive a respective reflection of the chirp from a target, and the delay line is configured to couple the reflections to the receiver unit such that they do not overlap in time.

[0013] In one or more embodiments, the radar front end may additionally include at least one of a receiving unit and a transmitter unit.

[0014] According to a second aspect of the present disclosure, a method is provided, the method comprising: transmitting a radar signal including a plurality of periodic pulses having a first duration from a transmitting antenna; receiving a reflection of the pulse transmitted from the transmitting antenna at a first receiving antenna as a first antenna reflection pulse; transmitting the reflection pulse to a receiver unit by means of a signal line; receiving a reflection of the pulse transmitted from the transmitting antenna at a second receiver antenna as a second antenna reflection pulse; coupling the second antenna reflection pulse to the beginning of a delay line; coupling the second antenna reflection pulse at the end of the delay line to the signal line by means of a directional coupler; and transmitting the second antenna reflection pulse to the receiver unit after the first antenna reflection pulse and without overlapping the first antenna reflection pulse. The signal line may be a transmitting line, a stripline, a waveguide, or other suitable means for transmitting the reflection pulse.

[0015] In one or more embodiments, the method further comprises:

[0016] Respective reflected radar pulses received at each of the antenna arrays are sequentially coupled to the receiver unit.

[0017] In one or more embodiments, the antenna array is a linear array.

[0018] In one or more embodiments,

[0019] The directional coupler is a rat-rail coupler.

[0020] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments will be described by way of example only with reference to the accompanying drawings in which

[0022] Figure 1 A simplified schematic diagram of a radar system including a front end having a single transmit antenna and a receive antenna array is shown;

[0023] Figure 2 Schematically showing the Figure 1 Timing associated with the operation of a conventional radar having multiple receive antennas as shown in;

[0024] Figure 3 A radar system according to an embodiment of the present disclosure is shown, the radar system comprising a front end having a transmitter antenna 120 and an array of receiving antennas therein;

[0025] Figure 4 Schematically showing the Figure 3 Timing associated with the operation of a radar having multiple receive antennas as shown in;

[0026] Figure 5 A radar front end according to one or more embodiments of the present disclosure is shown;

[0027] Figure 6 shows a radar front end according to one or more other embodiments of the present disclosure;

[0028] Figure 7 , Figure 8 and Fig. 9 each showing a radar front end according to yet other embodiments of the present disclosure; and

[0029] Fig.10 and Fig.11 A radar front end arranged for gesture recognition according to yet other embodiments of the present disclosure is shown.

[0030] It should be noted that the figures are diagrammatic and not drawn to scale. For clarity and convenience in the drawings, the relative sizes and proportions of the parts of these figures have been shown in an enlarged or reduced manner. The same reference numerals are generally used to refer to corresponding or similar features in modified and different embodiments. DETAILED DESCRIPTION

[0031] Figure 1 A simplified schematic diagram of a radar system 100 is shown, the radar system comprising a front end 110 having a single transmit antenna 120 and an array of receive antennas 130, 140, 150, 160, the array of receive antennas being configured as a linear array in this example. The radar system 100 further comprises a transmitter unit 170, which may be integral with a receiver unit 180, or may be separate from the receiver unit 180 as shown. In use, the transmitter unit 170 generates radar pulses, which are transmitted from the transmit antenna 120. In the presence of a reflecting target 190, a reflected radar pulse is generated by the transmitted pulse. The reflected radar pulse is received at each of the receive antennas. Each copy of the reflected radar pulse may be pre-processed, for example, in an RF front end processor (not shown) and forwarded to the receiver unit 180.

[0032] Figure 2 Schematically showing the Figure 11 shows the timing associated with the operation of a conventional radar with multiple receive antennas shown in FIG. The horizontal axis represents the passage of time. The transmitter unit 170 generates pulses that are transmitted from the transmitter antenna 120, as schematically shown at 122 and 124. Each pulse 122 and 124 is schematically shown as a triangle, illustrating the concept of frequency chirping, where the frequency of the transmitted pulse varies during the pulse - as shown the frequency may increase linearly from the beginning of the pulse to the completion of the pulse, but the skilled person will appreciate that other types of chirping may be used. The pulse chirp 122, 124 may have a duration Tp, as shown at 126. The transmitted signal takes a finite time Tt to reach the reflector or target, Figure 1 and Figure 2 In the figure, they are shown by 128 and 228 respectively.

[0033] When the pulse or chirp reaches the target 190, it is reflected back toward the radar system. The reflected signal takes a finite amount of time to reach each receiving antenna. However, because the receiving antennas are typically not equally far from the target, the pulse or chirp takes a slightly different time Tr1, Tr2, Tr3, or Tr4 to reach each receiving antenna. This Figure 1 This is shown by the different lengths of paths 132, 142, 152, and 162. Figure 2 As shown in , the closest receiver (in this case, receiver 130) receives the start of reflected signal 134 slightly earlier than the next closest receiver, which in turn receives the start of reflected signal 144 slightly earlier than the next receiver, and so on. In other words, the signals are not received simultaneously at each of the receiving antennas, but there is an offset between each receiving antenna. However, the path difference between the reflected signals is short, on the order of a few cm. For example, for a radar signal traveling at the speed of light (3x10∧8 m / s), a 1 cm path difference corresponds to a time offset of 30 ps. In general, the time offset resulting from the difference in path length is much smaller than the duration of the reflected radar pulse. The signals received at the receiving antennas therefore overlap to a large extent in time, and this generally requires parallel processing of the signals received within the receiver unit 180.

[0034] Now turn to Figure 3 and Figure 4 , these drawings illustrate the overall concept of the embodiments according to the present disclosure. First, turn to Figure 3, the radar system 300 includes a front end 310 having a transmitter antenna 120 and an array of receiving antennas 130, 140, 150 and 160 therein. The radar system further includes a transmitter unit 170 and a receiver unit 380. The first receiving antenna 130 is coupled to the receiver unit. However, the remaining receiving antennas 140, 150, 160 are not directly connected to the receiver unit 380. In fact, the front end includes an arrangement of delay lines and couplers in a daisy chain configuration. That is, the reflected data pulses received at all antennas are routed to the receiver unit 380 via a single signal path 136. The reflected data pulses received at the first receiving antenna 130 are directed to this signal path 136 via a coupler 138. The signal path 136 is connected to the output of the coupler 138. The coupler has a first input from the first receiving antenna 130, and a second input. The second input is connected to a delay line 146. The delay line 146 is connected to the second receiving antenna 140 via a second coupler 148. The delay line 146 is connected to the output of the second coupler 148. The second coupler has a first input connected to the second receive antenna 140, and a second input connected to another delay line 152. The further delay line 156 is connected to the third receive antenna 150 via a third coupler 158. The delay line 156 is connected to the output of the third coupler 158. The third coupler has a first input connected to the third receive antenna 140, and a second input connected to a further delay line 166. The further delay line is connected to the fourth receive antenna 160. In the embodiment shown, the fourth receive antenna 160 is an end receive antenna, and the further delay line 166 is directly coupled to the fourth antenna. In other embodiments, another coupler may be introduced between the further delay line 166 and the fourth receive antenna 160 in order to equalize the signal attenuation between any receive antenna and the associated delay line. In other embodiments, there may be more receive antennas, so that a coupler is needed to couple signals from those receive antennas.

[0035] Figure 4 The effect of introducing a coupler and a delay line into the front end 310 is shown. Figure 2 In conventional operation shown, the transmitter unit 370 generates pulses, which are transmitted from the transmitter antenna 120 and schematically shown at 122 and 124. The pulses or chirps 122, 124 may have a duration Tp, as shown at 126. The transmitted signal takes a finite time Tt to reach the reflector or target, Figure 1 and Figure 2 In the figure, they are shown by 128 and 228 respectively.

[0036] When the pulse or chirp reaches the target 190, it is reflected back toward the radar system, and the reflected signal takes a finite amount of time to reach each receiving antenna. As discussed above, because the receiving antennas are typically not equally far from the target, the pulse or chirp takes a slightly different time Tr1, Tr2, Tr3, or Tr4 to reach each receiving antenna. And therefore, the reflected signal is received at a slightly different start time. However, the duration of the signal is large relative to the difference between the flight times (that is, the difference between (Tt+Tr1), (Tt+Tr2), (Tt+Tr3), etc.). Therefore, the received signals overlap in time. However, by introducing delay lines, the signals can be separated in time, such as Figure 4 . Similar to conventional configurations, the beginning 334 of the reflected radar signal is received by the first receiving antenna 130 at a time (Tt+Tr1) after the start of the signal transmission from the transmitting antenna. The reflected signal is received by the second receiver antenna 140 at a time (Tt+Tr2) after the start of transmission. However, this signal is routed to the signal path 136 via a delay line. If the delay line introduces a delay D, the beginning of the reflected signal 344 received by the second receiving antenna 140 arrives at the signal path 136 to the receiving unit 380 at a time (Tt+Tr2+D) after the start of transmission. By ensuring that the delay D is equal to or greater than the duration of the transmitted signal pulse or chirp, when it arrives at the signal path 136 to the receiving unit, the signal received by the second receiving antenna 140 does not overlap in time with the signal received by the first receiving antenna 130 that has not been delayed. Similarly, the reflected radar signal received at the third receiving antenna 150 is delayed by another delay line before it arrives at the path taken by the signal received at the second receiving antenna 140, thereby introducing a delay D. This signal must travel through delay line 156 and delay line 146 before it reaches signal path 136. The start of the signal arrives at signal path 136 at a time (Tt+Tr3+2D) after the start of the transmitted signal.

[0037] In other words, the signals received by the respective antennas have been separated in time by the use of delay lines. It will be appreciated that as the signals travel through the delay lines and in particular through the couplers, there is attenuation of the signals. This is Figure 4 This is shown by a smaller triangle depicting the signal received later on the signal line, and it should be noted that this does not reflect nor is it intended to imply a different spectrum.

[0038] like Figure 2As has been shown in FIG. 1 , typically a radar system has a waiting or response time between each transmitted chirp in order to receive the reflected signal. It should be appreciated that in order to most effectively use the principles described above, the time should be sufficient so that the reflected radar signals received by all receiving antennas can be received by the receiver unit 380 in a sequential and non-overlapping manner as discussed above before starting to receive signals from subsequent transmitted pulses or chirps.

[0039] The processing of the signal in the receiving unit is simple using known techniques. Specifically, a radar front end with a linear array of antennas daisy-chained with delay lines between them is similar to a mobile synthetic aperture radar (SAR) platform with a single mobile receiver that scans the target with a snapshot at the exact location of the receiving antenna. The simulated trajectory of the movement can be tracked by the feed network, i.e., what is the next antenna to be fed. The target is illuminated by the chirp sent by the Tx antenna and received by each Rx antenna, just as a single receiver antenna is moving over those locations and building a larger synthetic aperture to image the target using SAR functionality. The functionality is simulated by the radar front end and is well explained in the literature and is well known to the skilled person.

[0040] Viewed from another perspective, the temporal separation of the reflected radar pulses received by each of the antennas allows signal processing to be performed in the same manner as other time division multiple access (TDMA) techniques, which will also be familiar to the skilled person.

[0041] Now turn to Figure 5 , this figure shows a radar front end 500 according to one or more embodiments of the present disclosure. The radar front end includes an array 505 of antennas 510, 520, 530. Each antenna is coupled to a first input 512, 522, 532 of a corresponding directional coupler in a plurality of directional couplers 514, 524, 534. The antenna array includes an end antenna 510 coupled to a first input 512 of a first directional coupler 514, the first directional coupler 514 having a directional coupler configured to couple to a receiver unit (380, Figure 5 The remaining directional couplers 524, 534 each have an output 526, 536 coupled to the input or start of a corresponding delay line 528, 538. The output or end of each delay line is coupled to the second input 519, 529 of the corresponding adjacent directional coupler. Figure 5In the embodiment shown in , each directional coupler is implemented as a rat track loop. As will be well known to the skilled person, a rat track loop has two inputs and two outputs. It can be configured as a directional coupler, wherein one of the outputs is terminated with a suitably matched terminal (indicated by a "T" in the figure). In addition, the use of a directional coupler such as a rat track loop configured as shown limits or minimizes any reflection back to the antenna, which may otherwise cause interference with the signal.

[0042] Now turn to Figure 6 , this figure shows a radar front end 600 according to one or more other embodiments of the present disclosure. The radar front end includes an array 605 of antennas 510, 520, 530. The array 605 may include another transmit antenna 610 as shown, which is directly coupled to the transmitter unit 170 (not shown).

[0043] Steering Figure 7 , this figure shows a radar front end 700 according to one or more other embodiments of the present disclosure. As shown, the antenna array 705 is arranged as a two-dimensional array. One of the antennas can be configured as a transmitting antenna 710 and is configured to be connected to the transmitter unit 370. The remaining antennas are receiver antennas 720, 730, 760, 770.. with delay lines 732, 742..762, 772.. in between. As in the previous embodiments, a directional coupler connects the output or end of the delay line with the signal from each receiving antenna and, except in the case of the last antenna 720, receives the signal from the associated receiving antenna at the input or beginning of the delay line. For ease of understanding, a directional coupler is not shown in the figure. As Figure 7 As shown, the antennas may be connected across a first row, and then back across another row. A composite signal, which is a combination of the time-separated reflected radar signals received at each of the antennas, is read out from the first antenna to the receiver unit 380 via signal path 136. The receiver unit 380 then "reads" the reflected signals in a manner from left to right from the first horizontal row, then from right to left from the second horizontal row, and from left to right from the third horizontal row (as shown).

[0044] The horizontal separation of the antennas in each row enables, for example, signal processing for a SAR platform, which can allow for improved resolution in the horizontal plane compared to a single antenna. In addition, the vertical separation of the antennas enables, for example, signal processing for a SAR platform, which can allow for improved resolution in the vertical plane. It will be appreciated that interleaved left-to-right and right-to-left readouts from the antennas may require the use of additional signal processing. Turning briefly to Figure 8 , this figure shows something similar to Figure 7, except that in this example the delay lines and directional couplers are configured to achieve a "readout" from each row of the antenna in a left-to-right order. This may allow for some simplification of the signal processing in the receiver unit 380. It will be appreciated that although Figure 8 and 9 A "4×4" array of receive antennas is shown, but fewer or more antennas may be included in any row, and fewer or more rows may be included. Furthermore, the number of antennas in each row need not be the same. Furthermore, the spacing of the antennas in each row with spacing between rows need not be the same. However, it will also be understood that signal processing is simplified in the case of a regular array of equally spaced antennas where there are the same number of antennas in each row. Furthermore, in embodiments where the antenna rows are equally spaced in the vertical direction, signal processing is also relatively simplified.

[0045] Fig. 9 A radar front end 900 is shown according to other embodiments of the present disclosure. Fig. 9 A first subarray is shown, which includes an array of transmit antennas 910 and receive antennas - in this case a two-dimensional array. As in the previously described embodiment, receive antennas 920, 930, 940 ... are connected by delay lines 934, 944 ... and directional couplers (not shown) so that the reflected radar signals received at each antenna arrive at the signal path 136 sequentially and separately. However, another (or more) such subarrays are included in this embodiment, each of which has its own transmit antenna and receive antenna. In the example shown, there is one such subarray with another transmit antenna 950 and additional receiver antennas 960, 970, 980 ... . The transmit antenna 950 is coupled to the transmit antenna 910 by another transmit daily laying line 955. In order to include multiple transmit antennas with delay lines between them, directional couplers are required with respect to combining reflected radar signals as discussed above; however, in the case of transmit antennas, directional couplers are provided so that pulses or chirps can be transmitted to first couple to the first transmit antenna 910, and then, after being delayed by the delay line, to the second transmit antenna 950. In the case of additional transmit antennas, additional directional couplers and delay lines are included. In e.g. Fig. 9 In the embodiment shown in , the delay line on the switching side may include delays that allow time division multiplexing of the transmit signal.

[0046] In some such embodiments, the first transmit-receive antenna of the second subarray may be coupled to the Fig. 9The last receiving antenna marked as 949 in FIG. However, the skilled person will appreciate that the signal from the more remote portion of the second subarray will have been significantly attenuated by passing through several directional couplers and delay lines by the time it reaches the first antenna 960 of the second subarray. Therefore, it may be preferred to direct this signal directly to the receiving unit to avoid further degradation of the signal-to-noise ratio of the received signal. Therefore, in addition to the signal path 136, according to Fig. 9 Some embodiments of the embodiment shown in may also include a second signal path 936 from the second sub-array to the receiver unit. In embodiments where there are more than two sub-arrays, there may correspondingly be more than two signal paths to the receiving unit.

[0047] It will be appreciated that the radar front end described above includes an array of receive antennas, and associated delay lines and couplers can achieve a low-cost, high-resolution radar, because all front-end components (excluding transmitters and receivers) such as couplers, delay lines and antennas can be provided as passive components and may be simpler to design and manufacture. In addition, it will be appreciated that a single RF channel can be used to provide high angular resolution, which may be beneficial compared to conventional multiple-input multiple-output (MIMO) radars in which more channels are added to improve resolution. In addition, the benefits of a SAR architecture can be provided without requiring any moving parts. Such a configuration may be particularly suitable for applications such as gesture recognition.

[0048] Fig.10 A radar front end suitable for gesture recognition according to one or more embodiments is schematically shown. As shown, the radar front end includes an antenna array, in this case arranged as a two-dimensional array. The array can be configured in a vertical arrangement and can be capable of detecting gestures. As will be appreciated from the above description, this array can enable a low-cost high-resolution radar that can be used in applications such as gesture recognition, where conventional high-resolution radar technology may not be economically justified.

[0049] like Fig.10 As shown, the antenna may be a sheet antenna 1020, 1030, ... However, the present disclosure is not limited thereto, and other antenna types known to the skilled person may be used. Specifically, the frequencies commonly used by short-range radars for applications such as gesture recognition are currently typically about 10 GHz to 100 GHz. Such a frequency range is well suited for slot antennas, which can be constructed at low cost, for example, by a multi-layer PCB manufacturing process to produce, for example, Fig.11 , in which the individual rows of antennas 1120, 1130, ... are fabricated within individual PCBs or similar structures in which waveguides may be easily printed or otherwise defined.

[0050] By reading this disclosure, other changes and modifications will be apparent to the skilled person. Such changes and modifications may involve equivalent and other features that are already known to us in the field of radar antenna arrays and can be used as a substitute or supplement to the features already described herein.

[0051] Although the attached claims are directed to specific feature combinations, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel feature combination or any generalized form thereof disclosed explicitly or implicitly herein, regardless of whether it relates to the same invention as currently claimed in any claim or whether it alleviates the same technical problem as any or all of the technical problems alleviated by the present invention.

[0052] Features described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, for the sake of brevity, various features described in the context of a single embodiment may also be provided separately or in any suitable subcombination. Applicants hereby caution that new claims may be formulated based on such features and / or combinations of such features during the prosecution of this application or any further application derived therefrom.

[0053] For the sake of completeness, it is also stipulated that the term "comprising" does not exclude other elements or steps, the term "a" does not exclude a plurality, a single processor or other unit may perform the functions of several components recited in the claims [deleted if irrelevant], and the reference numerals in the claims should not be interpreted as limiting the scope of the claims. In addition, the word "may" is used in a permissive sense (i.e., having a potential meaning) rather than a mandatory sense (i.e., a necessary meaning). Similarly, the word "comprising" means including but not limited to.

Claims

1. A radar front end, characterized in that: include: an antenna array, each antenna coupled to a first input of a respective one of a plurality of directional couplers, and the antenna array comprising an end antenna coupled to a first input of a first directional coupler; the first directional coupler having an output configured to be coupled to a receiver unit; the remaining directional couplers each having an output coupled to an input of a corresponding delay line; The output of each delay line is coupled to the second input of the corresponding adjacent directional coupler.

2. The radar front end according to claim 1, characterized in that: Wherein the radar front end is configured to sequentially couple respective reflected radar pulses received at each of the antenna arrays to the receiver unit.

3. The radar front end according to claim 2, characterized in that: Each of the antenna arrays receives reflected radar pulses, wherein the reflected radar pulses overlap in time, and wherein the delay line delays the reflected radar pulses such that they do not overlap in time at the output of the first directional coupler.

4. The radar front end according to claim 1, characterized in that: The antenna array is a linear array.

5. The radar front end according to claim 1, characterized in that The plurality of directional couplers is a plurality of rat-rail couplers.

6. The radar front end according to claim 2, characterized in that The first input of each directional coupler is a corresponding rat-rail first input, the second input of each directional coupler is a corresponding rat-rail second input, and the output of each directional coupler is a corresponding rat-rail sigma output.

7. The radar front end according to claim 4, characterized in that: It additionally comprises a transmit antenna, wherein the transmit antenna is aligned to the linear array of antennas to form an extended array.

8. The radar front end according to claim 7, characterized in that The transmitting antenna is configured to transmit a radar chirp, Each antenna of the antenna array is arranged to receive a respective reflection of the radar chirp from a target, and the delay line is configured to couple the reflections to the receiver unit such that they do not overlap in time.

9. A method, characterized in that include: transmitting, from a transmit antenna, a radar signal comprising a plurality of periodic pulses having a first duration; receiving, at a first receiving antenna, a reflection of a pulse transmitted from the transmitting antenna as a first antenna reflected pulse; transmitting the first antenna reflected pulse to the receiver unit by means of a signal line; receiving, at a second receiver antenna, a reflection of the pulse transmitted from the transmit antenna as a second antenna reflected pulse; coupling the second antenna reflected pulse to the beginning of the delay line; coupling the second antenna reflected pulse at the end of the delay line to the signal line by means of a directional coupler; as well as The second antenna reflected pulse is transmitted to the receiver unit after the first antenna reflected pulse and without overlapping the first antenna reflected pulse.

10. The method according to claim 9, characterized in that Also includes: Respective reflected radar pulses received at each of the antenna arrays are sequentially coupled to the receiver unit.

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