Background
Due to the continuous improvement of automobile safety standards in various countries, advanced Driving Assistance Systems (ADAS) of active safety technology have rapidly developed in recent years. The automobile millimeter wave radar has the advantages of all-weather operation, high accuracy, strong anti-interference capability, strong penetrating power, long detection distance, over 120 km of action speed per hour, no influence on the overall appearance of the vehicle and the like, and becomes a main stream choice recognized by automobile electronic manufacturers and has huge market demands.
To achieve higher angular resolution, increasing the antenna aperture is the most straightforward technical choice. The MIMO technology can improve the antenna aperture on the premise of increasing the radar size as small as possible, and becomes a choice of a plurality of vehicle-mounted radar manufacturers.
MIMO, a multiple input multiple output technology, refers to using multiple transmitting antennas and receiving antennas at a transmitting end and a receiving end, respectively, so that signals are transmitted and received through the multiple antennas at the transmitting end and the receiving end, thereby improving communication quality. The system can fully utilize space resources, realize multiple transmission and multiple reception through a plurality of antennas, and can doubly improve the system channel capacity under the condition of not increasing frequency spectrum resources and antenna transmitting power, thereby showing obvious advantages. The application of MIMO technology makes space a resource that can be used to improve performance, thereby increasing the coverage of the wireless system. The MIMO radar has virtual aperture expansion capability and more flexible power distribution capability, and improves the energy utilization rate, angle measurement precision, clutter suppression, low interception capability and other performances of the system.
For an M transmit N receive MIMO radar, the transmit element and the receive element share m×n pairs, i.e., m×n transmit elements and N receive elements can be virtualized, and the number of the transmit elements and the receive elements is generally far greater than N, so that the array aperture is extended. For example, the 2-transmission 4-reception MIMO radar can form an 8-element virtual array, and the radar detection precision is greatly improved under the condition of not increasing the number of antennas.
Fig. 1 shows a schematic diagram of such a 2-transmit (TX 1, TX 2) and 4-receive (RX 1 to RX 4) MIMO virtual array element, and finally virtually obtaining RX1 to RX4, and VRX1 to VRX4 totaling 8 virtual array elements.
Currently, the industry mostly uses long-distance MIMO antennas and short-distance MIMO antennas in combination, such as the schematic diagram of the coverage area of the long-distance MIMO antennas shown in fig. 2. The purpose of the combined use is to simultaneously exert the performance advantages of the long-distance antenna and the short-distance antenna, namely: firstly, the performance characteristics of the remote antenna are high gain narrow lobe angles, and remote target monitoring can be provided; second, the performance characteristics of the short-range antenna are low gain wide lobe angle, can provide short-range wide angle target coverage, and can bring the advantages of the two into play.
It should be noted that, to achieve the high gain characteristic of the remote antenna, multiple arrays of antennas are required for the array, the number of antenna arrays is proportional to the antenna gain, theoretically (without considering the loss), the number of antenna array sets is doubled, the antenna gain is increased by 3dB, and as a result, the physical width of the remote antenna is necessarily wider.
To achieve the near antenna linewidth lobe angle characteristics, it is generally necessary to implement a single-column antenna, which brings about antenna lobe angle compression, resulting in a narrow physical width of the near antenna.
Based on the characteristics of the antenna, the unreasonable antenna layout inevitably leads to lengthening of the antenna feeder, and as a result, the feeder loss is increased and the antenna performance is reduced.
Disclosure of Invention
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed.
The invention aims to provide a vehicle-mounted MIMO radar antenna layout scheme, and aims to provide a compact antenna layout scheme, so that the antenna feeder loss can be reduced, and the radar performance can be improved.
In order to achieve the above object, the present invention provides a layout structure of a vehicle-mounted MIMO radar antenna, which is applied to a radio frequency chip, and is characterized in that the layout structure includes:
The first transmitting antenna group comprises a plurality of first transmitting antennas which are arranged along the first direction in an extending way;
the second transmitting antenna group comprises a plurality of second transmitting antennas which are arranged along the first direction in an extending way;
The first receiving antenna group comprises a plurality of first receiving antennas which are arranged along the first direction in an extending way;
Wherein the second transmit antenna group is located between the first transmit antenna group and the first receive antenna group in a second direction;
The second direction is perpendicular to the first direction.
Preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that,
The first transmitting antenna group, the second transmitting antenna group and the first receiving antenna group are arranged in an axisymmetric mode by taking the radio frequency chip as an axis.
Preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that,
The first receiving antenna group comprises a plurality of short-distance receiving antennas covering short distances and a plurality of long-distance receiving antennas covering long distances;
Wherein the plurality of short-range receiving antennas are arranged between the plurality of long-range receiving antennas which are divided into two groups.
Preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that,
The phase center height difference H between every two of the plurality of first transmitting antennas, between every two of the plurality of second transmitting antennas and between every two of the plurality of short-distance receiving antennas and between every two of the plurality of long-distance receiving antennas meets the following conditions:
H＜λ
and lambda is the working wavelength of the MIMO radar antenna.
Preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that,
The first transmitting antenna, the second transmitting antenna and the first receiving antenna comprise single-column antennas and array antennas, and the distance between the array antennas is the distance between the centers of the array antennas.
Preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that,
The long-distance covered transceiving antenna and the short-distance covered transceiving antenna adopt a time-sharing working mode.
Preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that in the layout structure,
The first transmitting antenna group comprises 2 long-distance transmitting antennas with a distance D1, the second transmitting antenna group comprises 2 short-distance transmitting antennas with a distance D2, the first receiving antenna group comprises 4 short-distance receiving antennas which are divided into two groups, the distance D5 between every two adjacent short-distance receiving antennas in each group, the distance D6 between every two adjacent short-distance receiving antennas in every two groups, the first receiving antenna group further comprises 4 long-distance receiving antennas which are divided into two groups, the distance D3 between every two adjacent long-distance receiving antennas in each group and the distance D4 between every two adjacent long-distance receiving antennas in every two groups, wherein the 4 short-distance receiving antennas are arranged between two groups of the 4 long-distance receiving antennas;
wherein, each antenna interval satisfies:
D1＝2×D3
D4＝3×D3
D2＝5×D5+D6。
preferably, the invention further provides a layout structure of the vehicle-mounted MIMO radar antenna, which is characterized in that,
The spacing of the antenna groups satisfies:
D4>2×D5+D6。
The invention utilizes the axisymmetric structure, and the distance from the most far-end antenna of the radio frequency chip to the pin of the radio frequency chip is shortest, so that the minimum feeder loss is realized. And the long-distance transmitting antenna and the short-distance transmitting antenna extend along different transverse lines, so that the problem of layout interference between the antennas due to the problem of antenna spacing can be avoided.
Detailed Description
This specification discloses one or more embodiments that incorporate the features of the invention. The disclosed embodiments merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiments. The invention is defined by the appended claims.
Reference in the specification to "one embodiment," "an example embodiment," etc., means that a particular feature, structure, or characteristic may be included in the described embodiments, but that all embodiments may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, mechanism, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, mechanism, or characteristic in connection with other embodiments whether or not explicitly described.
Moreover, it is to be understood that the spatial descriptions (e.g., above, below, above, left, right, below, top, bottom, vertical, horizontal, etc.) used herein are for illustrative purposes only, and that the actual implementation of the structures described herein may be spatially arranged in any orientation or manner.
Referring to fig. 3, a vehicle-mounted MIMO radar antenna according to the present invention includes a transceiver antenna covering a long distance and a transceiver antenna covering a short distance, and is configured to extend laterally according to a three-layer layout. The technical scheme is described in detail below in conjunction with the layout shown in fig. 3:
In the vehicle-mounted MIMO radar antenna layout structure, a transceiver antenna covering a long distance comprises 2 long-distance transmitting antennas TX2 and TX3 and 4 long-distance receiving antennas RX1, RX2, RX7 and RX8; and the transceiver antenna covering the short range includes 2 short range transmitting antennas TX1, TX4, and 4 short range receiving antennas RX3, RX4, RX5, RX6.
The long-distance and short-distance transmitting and receiving antennas are arranged according to three layers of layouts, and the method is as follows:
a first layer: the transmission antennas TX2 and TX3 covering the long distance extend along the first transverse direction;
a second layer: the transmitting antennas TX1, TX4 covering the close range extend in the second lateral direction;
And a third layer, wherein the receiving antennas RX1, RX2, RX7 and RX8 covering the long distance and the receiving antennas RX3, RX4, RX5 and RX6 covering the short distance extend along the third horizontal line direction.
Wherein, although the near and far distance receiving antennas are arranged in the third horizontal line direction, the receiving antennas are divided into two groups, wherein 4 receiving antennas RX1, RX2, RX7 and RX8 covering the far distance are divided into two groups, wherein RX1 and RX2 are the first group, and the interval between every two groups is D3; RX7 and RX8 are the second group, the interval between every two groups is D3, and the interval between two long-distance groups of receiving antennas is D4.
The distances D1, D3, D4 between the remote transmitting antennas TX2 and TX3 and the remote receiving antennas RX1, RX2, RX7, RX8 described above satisfy the following relationship:
D1＝2×D3 (1)
D4＝3×D3 (2)
It should be noted that, the spacing between the single-column antennas is the distance between the single-column antennas, and the spacing between the array antennas is the distance between the centers of the array antennas.
In the embodiment shown in fig. 3, the two remote transmitting antennas TX2 and TX3 are each an array antenna consisting of 8×10 radio units, and D1 is shown as the distance between the centers of the two array antennas. The close range transmitting antennas TX1 and TX4 are single-column antennas, so the distance D2 between them is the distance between the two single-column antennas.
In the third layer, the 4 receiving antennas RX3, RX4, RX5, RX6 covering the close range are also divided into two groups, wherein RX3, RX4 are the first group of receiving antennas, and the interval between two groups is D5; RX5 and RX6 are the second group of receiving antennas, and the interval between every two is also D5. The distance between the first and second groups of receiving antennas is D6, and the relationship between the distance D2 between the close range transmitting antennas TX1 and TX4 and D5 and D6 between the first and second groups of close range receiving antenna groups RX3 to RX6 needs to satisfy:
D2＝5×D5+D6 (3)
In order to ensure that the close range receiving antenna can be placed in the distance receiving antenna interval, it is necessary to ensure that:
D4＞2×D5+D6 (4)
the arrangement of the short-distance receiving antennas RX3, RX4, RX5, and RX6 is not limited to this, and may be equally spaced, non-equally spaced, randomly combined, and equally spaced or non-equally spaced by groups.
Fig. 7 is a schematic diagram of a layout of the transceiver antenna according to the present invention using three layers of lateral extension directions based on fig. 3.
That is, the M long-distance transmitting antennas TX-I provided on the first layer are arranged along the first traverse direction, the X short-distance transmitting antennas TX-II on the second layer are arranged along the second traverse direction, and the N long-distance receiving antennas and the Y short-distance receiving antennas RX on the third layer are arranged along the third traverse direction.
In terms of signals, the transmitting antennas TX2, TX3 of the long-distance transceiving antennas are used to transmit radar signals, and the long-distance receiving antennas RX1, RX2, RX7, RX8 are used to receive long-distance target echo signals. The transmitting antennas TX1, TX4 of the near-distance receiving antennas are used to transmit radar signals, and the near-distance receiving antennas RX3, RX4, RX5, RX6 are used to receive near-distance target echo signals.
The long-distance receiving and transmitting antennas TX2, TX3, RX1, RX2, RX7 and RX8 are array antennas formed by multiple rows of antennas, the antenna is characterized by high-gain antennas, the azimuth angle of the antenna is narrower, and long-distance narrow-angle target coverage can be provided.
The near-field transceiver antennas TX1, TX4, RX3, RX4, RX5 and RX6 are all single-column array antennas, the antenna is characterized by a low-gain antenna, the azimuth angle of the antenna is wider, and the near-field wide-angle target coverage can be provided.
In the layout embodiment shown in fig. 3, a radio frequency chip RF is further included, and the layout of all antennas including the long-distance transceiver antenna and the short-distance transceiver antenna is arranged with the radio frequency chip RF as an axisymmetric center. In the figure, the broken line represents the central axis L of the radio frequency chip RF, i.e. each layer of the three-layer structure covering the transceiver antenna at a distance from the near to the far is symmetrically arranged with the central axis L.
Specifically, the remote transmitting antennas TX2 and TX3 are axisymmetric with the central axis L as the axis; the short-range transmitting antennas TX1 and TX4 are axisymmetric with the central axis L; the remote receiving antennas RX1 and RX2, RX7 and RX8 are arranged in an axisymmetric way by taking the central axis L as an axis; the short-range receiving antennas RX3, RX4, RX5, RX6 are also arranged axisymmetrically with respect to the central axis L.
The axisymmetric structure has the advantage that the distance from the RF-most remote antenna of the radio frequency chip to the pin of the radio frequency chip is the shortest, i.e. the feeder loss is the smallest, compared to other non-axisymmetric antenna solutions.
The long-distance covered transceiving antenna and the short-distance covered transceiving antenna adopt a time-sharing working mode.
The receiving antennas in the receiving and transmitting antennas covering the long and short distances generate virtual array elements through the translation of the transmitting antennas, so that the caliber of the radar antenna is increased, the angular resolution of the radar azimuth plane is improved, the caliber of the radar antenna is maximized, and the angular resolution of the radar azimuth plane is improved.
Fig. 4 illustrates the operation of the remote transmitting and receiving antenna.
The receiving antennas Rx1, rx2, rx7 and Rx8 translate at intervals between the transmitting antennas Tx2 and Tx3 to generate virtual array elements VRx1, VRx2, VRx7 and VRx8, wherein the virtual array elements VRx1 and VRx2 just fall between the receiving antennas Rx2 and Rx5, the antenna caliber is increased by about 1 time, and the corresponding angle resolution is improved by about 1 time.
Fig. 5 further illustrates the operation of the close range transmit receive antenna.
The receiving antennas Rx3, rx4, rx5 and Rx6 generate virtual array elements VRx3, VRx4, VRx5 and VRx6 by means of space translation between the transmitting antennas Tx1 and Tx4, the antenna aperture is increased by more than 1 time, and the corresponding angle resolution is improved by about 1 time.
Fig. 8 shows a diagram of the resultant coverage area of the radar produced by the arrangement shown in fig. 3, where the radar distance coverage may be greater than 200m (rcs=10 dBsm), and the FOV may be up to ±4°, the radar near 70m (rcs=10 dBsm), and the coverage distance may be up to ±48° with respect to the FOV.
It should be noted that, the antennas in the same layer do not require the antenna phase center height to be completely aligned, and the appropriate phase center height difference is also considered as the same layer, and fig. 9 illustrates that there is a height difference H between two antennas with the same function located in the same layer, where the range of H needs to be satisfied:
H＜λ (5)
and lambda is the working wavelength of the MIMO radar antenna.
The layout of fig. 3 provided in the preferred embodiment of the present invention is three layers, and for convenience of explanation, each layer of antenna function is defined, but each layer of antenna function is not unique, each layer of antenna function is changed, and the present invention is also applicable to the layout scheme of the antenna, but the positions of the receiving antennas must be in the first layer or the third layer, and the positions of the transmitting antennas in the other two layers can be changed at will.
The antenna spacing relationship includes, but is not limited to, the antenna spacing relationship in the embodiment, the number of antenna arrays and the number of units includes, but is not limited to, the number of near and far transceiver antennas includes, but is not limited to, the number of antennas in the embodiment.
In addition, the antenna form is not fixed, and can be other antenna forms such as a microstrip patch antenna, a substrate integrated waveguide slot antenna and the like, and the antenna form is not limited on the premise of meeting the layout requirement.
Furthermore, M, N, X, Y is even in the above embodiment, when any one of M, N, X, Y is odd, for example, when m=3, the antenna layout is as shown in fig. 6, that is, the middle antenna phase center is guaranteed to coincide with the radio frequency chip center axis. The layout scheme may also consider the antenna axisymmetric with respect to the rf chip.
The technical scheme of the invention has the advantages that:
First, in the case of a certain antenna spacing, the distance from the most remote antenna of the rf chip to the rf chip pins is the shortest, i.e. the feeder loss is the smallest, compared to other non-axisymmetric antenna schemes.
Second, the long-range transmitting antenna and the short-range transmitting antenna extend along different transverse lines, which is beneficial in that the problem of layout interference caused by the problem of antenna spacing between the antennas can be avoided. Namely, the long-distance transmitting antenna extends along the first transverse direction, the antenna spacing layout is flexible, and the long-distance transmitting antenna is not influenced by the short-distance transmitting antenna layout. The close-range transmitting antenna extends along the second transverse direction, the space layout of the antennas is flexible, and the close-range transmitting antenna is not influenced by the layout of the remote-range transmitting antenna.
The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.