A positioning antenna based on a four-quadrant distribution structure

Abstract

The utility model discloses a positioning antenna based on four quadrant distribution structure, including same multiple directional antenna, and directional antenna is with the intersection of two mutually perpendicular vertical surfaces as the center axis, and is distributed in the same horizontal height circumferentially, and the radiation direction of each directional antenna is radially outward with the center axis as the center, and the perpendicular projection of two vertical surfaces divides the horizontal plane into four quadrants, and each quadrant has at least one directional antenna. The positioning antenna based on four quadrant distribution structure proposed by the utility model not only can form the locking interface of projection as linear, but also can directly distinguish the movement direction of the object to be positioned from inside to outside or from outside to inside, and the RSSI value of each antenna under the influence of environment increases or decreases when positioning based on the positioning antenna of four quadrant distribution structure, and is eliminated when vector operation.

Description

Technical Field

[0001] This utility model belongs to the field of wireless positioning technology, specifically relating to the technology of determining the location of a located object by the received signal strength (RSSI) value, and in particular, determining the relative position of the located object with respect to a target boundary or interface. Background Technology

[0002] Installing locking wheels (one, two, or all) on shopping carts, which lock when the cart attempts to cross the supermarket boundary, is currently a proven and effective method for preventing theft. One key technical challenge in this method is determining when the cart is attempting to cross the boundary.

[0003] US Patent No. 5598144 discloses a shopping cart anti-theft method. This method involves installing buried cables along the boundary of the area accessible to shopping carts outside the supermarket (typically a parking lot boundary). These buried cables radiate signals at close range. Signal receivers are installed inside the wheels to receive the radiated signals from the buried cables. When the shopping cart attempts to cross the boundary from the inside out, the wheels pass over the buried cables, and the signal receivers receive the radiated signals. Based on the signals received from the buried cables, the controller activates a locking mechanism to lock the wheels.

[0004] The disadvantages of this method are: 1. Buried cables are expensive. 2. The ground needs to be dug up for cable installation, which is inconvenient and costly.

[0005] US Patent No. 8463540 uses a directional antenna instead of buried cables. By placing a base station at the boundary where shopping carts are prohibited, the base station sends a locking command to the signal coverage area of ​​the directional antenna, forming a locked zone. The signal coverage area of ​​the directional antenna covers the boundary where shopping carts are prohibited. When a shopping cart attempts to cross the boundary, the wheels enter the locked zone. The wheel's signal receiver receives the locking command from the directional antenna, and the controller, based on the locking command received from the base station, activates the locking mechanism to lock the wheels.

[0006] The drawback of this method is that even narrow-beam directional antennas have blade-shaped lobes, making it difficult to form a very narrow line of radiation. Instead, they cover a relatively wide area, making it difficult to accurately determine whether a shopping cart is attempting to cross the boundary. This can easily lead to shopping carts that are moving normally near the boundary (e.g., being pushed parallel to the boundary within the boundary) being mistakenly locked. A better solution proposed in this patent is to enclose the boundary with a fence, maintaining a sufficiently wide entrance / exit for pedestrians and vehicles, and then placing a base station at the entrance / exit. However, enclosing the boundary outside the entrance / exit is also very costly. Furthermore, the actual radiation range of a directional antenna does not have a clear boundary. This patent uses RSSI values ​​to determine whether a shopping cart has entered the locking area, but RSSI values ​​fluctuate. If the threshold is set too high, missed locking is likely. If the threshold is set too low, the probability of false locking increases. Moreover, signal strength is very susceptible to environmental interference. Using an absolute threshold as the criterion, the effective coverage area of ​​the antenna (the area with RSSI greater than the threshold) will change under different weather conditions, pedestrian activity, and object obstruction, resulting in poor stability. Under good conditions, an antenna that can normally cover the entire target area may fail to do so under poor conditions, leading to vulnerabilities in the anti-theft system. Summary of the Invention

[0007] This invention addresses the problem of determining whether a shopping cart is attempting to cross a boundary by proposing a positioning method suitable for determining the relative position of the object being positioned with respect to a target vertical plane (such as the vertical projection line and the plane corresponding to the boundary of a supermarket parking lot), as well as various applications.

[0008] This utility model discloses a positioning antenna based on a four-quadrant distribution structure, including multiple identical directional antennas. The directional antennas are circumferentially distributed at the same horizontal height with the intersection of two mutually perpendicular vertical planes as the central axis. The radiation direction of each directional antenna is radially outward with the central axis as the center. The vertical projection of the two vertical planes divides the horizontal plane into four quadrants, and each quadrant has at least one directional antenna.

[0009] Preferably, the directional antenna comprises four groups, each located in one of the four quadrants. The four groups of antennas form a 90-degree rotationally symmetrical structure with the intersection of two vertical planes as the central axis.

[0010] Furthermore, the four antennas form a centrally symmetrical structure with the intersection of the two vertical planes as the central axis.

[0011] Furthermore, the four antennas form a ring array structure with the intersection of the two vertical planes as the central axis.

[0012] Furthermore, it also includes a directional antenna mounted on a vertical plane.

[0013] Based on the aforementioned four-quadrant distribution structure of the positioning antenna, this utility model further claims a positioning method based on vector operations for determining the relative position of the object to be positioned relative to two mutually perpendicular target vertical planes. This method uses the object to be positioned as the signal transmitter, with the intersection of the two target vertical planes as the central axis, and multiple directional antennas distributed circumferentially. In each of the four right-angled regions formed by the two target vertical planes, at least one directional antenna is distributed. The RSSI value of the same signal received from the object by each directional antenna is used as the magnitude of the vector, and the angle of the directional antenna is used as the direction of the vector to obtain the detection vector of that directional antenna. The detection vectors of each directional antenna are added together to obtain a positioning vector. The quadrant in which the direction of this positioning vector lies determines which right-angled region the object to be positioned is located in.

[0014] Based on the aforementioned vector-based positioning method, this utility model discloses a vector-based positioning system for locating an object crossing a target boundary. The system includes a positioning device and the object being located. The object is equipped with a signal transmitter. The positioning device includes two positioning antennas with a four-quadrant distribution structure (described above) positioned at both ends of the target boundary, several signal processing modules, and a controller for vector operation judgment. Each directional antenna of the two positioning antennas is connected to a signal processing module. Each signal processing module calculates and outputs the RSSI value of the signal received by its connected directional antenna. The first vertical plane of the first positioning antenna and the second positioning antenna are both aligned with the target boundary. The controller uses the RSSI value of the directional antenna as the magnitude of the vector and the angle of the directional antenna as the direction of the vector to generate a detection vector for one directional antenna. The controller adds the detection vectors of all directional antennas of one positioning antenna to obtain the positioning vector of that antenna. The controller combines the directions of the positioning vectors of the two antennas to determine whether the object being located is within the width of the target boundary and, if so, on which side of the target boundary it is located.

[0015] The aforementioned positioning system based on vector operations can be used for shopping cart reverse movement control, shopping cart anti-theft, or product anti-theft.

[0016] When used for shopping cart reverse movement control, two positioning antennas are set on both sides of the prohibited reverse movement channel. The second positioning antenna is set to be located on the positive half-axis of the X-axis of the first positioning antenna. The first quadrant of the first positioning antenna and the second quadrant of the second positioning antenna are used as the locking zone, and the fourth quadrant of the first positioning antenna and the third quadrant of the second positioning antenna are used as the unlocking zone. When the shopping cart moves from the unlocking zone to the locking zone without passing through other zones, a locking command is sent to the shopping cart. The shopping cart receives and responds to the locking command, and activates the braking mechanism to lock the shopping cart.

[0017] When used for shopping cart anti-theft, positioning antennas are placed on both sides of the parking lot entrance and exit. A second positioning antenna is positioned on the positive X-axis of the first positioning antenna. The area where the first quadrant of the first positioning antenna coincides with the second quadrant of the second positioning antenna is designated as the locking zone, and the area where the fourth quadrant of the first positioning antenna coincides with the third quadrant of the second positioning antenna is designated as the unlocking zone. When the shopping cart is in the locking zone, a locking command is sent to the cart. The cart receives and responds to the locking command, activating the braking mechanism to lock the cart. Furthermore, when the shopping cart is in the unlocking zone, an unlocking command is sent to the cart. The cart receives and responds to the unlocking command, activating the braking mechanism to unlock the cart.

[0018] When used for anti-theft of goods, the positioning antennas are placed on both sides of the supermarket entrance, and the control condition is that the shopping cart has not been checked out. The control method can be the aforementioned reverse control method or the shopping cart anti-theft control method.

[0019] This invention further claims a shopping cart control method based on vector operations, using the aforementioned vector-based positioning system for supermarket shopping cart control. The method uses the shopping cart as the object to be positioned, equips it with a braking mechanism to restrict its movement, and provides both command receiving and positioning signal sending capabilities. Two positioning antennas with a four-quadrant distribution structure are positioned at either end of a boundary line (e.g., a parking lot entrance / exit boundary) to receive positioning signals from the shopping cart. The first vertical planes of the two positioning antennas correspond to the boundary line. The RSSI value of the directional antenna is used as the magnitude of the vector, and the angle of the directional antenna is used as the direction of the vector to obtain the detection vector of one directional antenna. The positioning vector of the positioning antenna is obtained by adding the detection vectors of all the directional antennas of the positioning antenna. The directions of the positioning vectors of the two positioning antennas are combined to determine whether the shopping cart is within the width of the boundary line prohibiting cart movement, and which side of the boundary line it is on. When the shopping cart is positioned outside a boundary that prevents it from being pushed out, or, based on positioning results at different times, it is determined that the shopping cart has moved from the inside to the outside of a boundary that prevents it from being pushed out, a locking command is sent to the shopping cart. Upon receiving the locking command, the shopping cart activates its braking mechanism to lock the cart.

[0020] Furthermore, the positioning signal sent by the shopping cart includes the status information of the shopping cart being locked or unlocked. When the shopping cart is located inside a boundary line that prevents the shopping cart from being pushed out and is in a locked state, an unlock command is sent to the shopping cart. After receiving the unlock command, the shopping cart activates the braking mechanism to unlock the shopping cart.

[0021] Based on the aforementioned shopping cart control method based on vector operations, this utility model further claims a shopping cart control system based on vector operations, including a shopping cart as the object to be located and a base station for locating and controlling the shopping cart. The shopping cart is equipped with a braking mechanism to limit its movement and a transceiver for sending positioning signals and receiving control commands. The base station is equipped with a positioning antenna for receiving positioning signals, a signal processing module having the same number of directional antennas as the positioning antenna, and a controller for determining positioning and generating control commands. Optionally, the base station is also equipped with a transmitting antenna for sending control commands (if no transmitting antenna is configured, the control commands can also be sent through the positioning antenna).

[0022] The positioning antenna is the aforementioned positioning antenna based on a four-quadrant distribution structure. The positioning antenna includes a first positioning antenna and a second positioning antenna respectively positioned at both ends of a boundary line prohibiting shopping carts from being pushed out. The first vertical planes of the first and second positioning antennas overlap and correspond to the boundary line prohibiting shopping carts from being pushed out. Each directional antenna in the positioning antenna is connected to a signal processing module. Each signal processing module calculates and outputs the RSSI value of the positioning signal received by its connected directional antenna. Each signal processing module is connected to a controller. The controller uses the RSSI value of the directional antenna as the magnitude of the vector and the angle of the directional antenna as the direction of the vector to generate a detection vector for the directional antenna. The controller adds the detection vectors of all directional antennas of a positioning antenna to obtain the positioning vector of that positioning antenna. The controller combines the directions of the positioning vectors of the two positioning antennas to determine whether the shopping cart is located within the width of the boundary line prohibiting shopping carts from being pushed out, and on which side of the boundary line it is located on. When the shopping cart is located outside a boundary that prevents it from being pushed out, or when the location results at different times indicate that the shopping cart has moved from the inside to the outside of a boundary that prevents it from being pushed out, the base station sends a locking command to the shopping cart. After receiving the locking command, the shopping cart activates its braking mechanism to lock the cart.

[0023] Alternatively, the base station may be configured with only one controller, to which all signal processing modules are connected.

[0024] Alternatively, the base station includes a primary base station and a secondary base station. The primary base station includes a first positioning antenna, a signal processing module with the same number of directional antennas as the first positioning antenna, and a first controller, and optionally also includes a transmitting antenna. The secondary base station includes a second positioning antenna, a signal processing module with the same number of directional antennas as the second positioning antenna, and a second controller. The secondary base station (optionally via a wired or additionally configured communication module and antenna) communicates with the primary base station.

[0025] The second controller adds the detection vectors of all directional antennas of the second positioning antenna to obtain the positioning vector of the second positioning antenna, and sends the direction of the positioning vector (an angle value between 0 and 360 degrees) to the first controller. The first controller adds the detection vectors of all directional antennas of the first positioning antenna to obtain the positioning vector of the first positioning antenna. Combining the directions of the positioning vectors of the first and second positioning antennas, the first controller determines whether the shopping cart is within the width of the no-cart-out boundary and on which side of the no-cart-out boundary it is located on. When the shopping cart is located outside the no-cart-out boundary, or, based on positioning results at different times, it is determined that the shopping cart has moved from the inside to the outside of the no-cart-out boundary, the first controller generates a locking command and sends it to the shopping cart via a transmitting antenna (if a transmitting antenna is configured) or one of the directional antennas of the first positioning antenna (if no transmitting antenna is configured).

[0026] One can imagine: By setting the above-mentioned shopping cart control system based on vector operation at the entrance and exit of the closed parking lot, a shopping cart anti-theft system based on vector operation is formed, which can effectively prevent shopping carts from being pushed out of the supermarket area from the entrance and exit of the closed parking lot. Applying the above-mentioned shopping cart control system based on vector operations to an open parking lot, dividing the parking lot boundary into several straight segments, and setting up a system for each segment, constitutes another shopping cart anti-theft system based on vector operations, which can effectively prevent shopping carts from being pushed out of the supermarket area from the boundary of the open parking lot. By setting the aforementioned shopping cart control system based on vector operations at the boundary that prohibits unchecked shopping carts from being pushed out, and using "unchecked shopping cart" as a prerequisite for issuing a cart locking command, a commodity anti-theft system based on vector operations is constituted, which can effectively prevent unchecked goods from being stolen by pushing out the shopping cart. By placing the aforementioned vector-based shopping cart control system at the entrance of the supermarket shopping area, and using the condition that "the shopping cart moves from the inside to the outside within a boundary width that prohibits pushing the shopping cart out" as the condition for issuing the locking command, a vector-based shopping cart reverse-movement control system is constructed, which can prevent customers from pushing the shopping cart out of the shopping area entrance in the opposite direction. The beneficial effects of this utility model are: Compared with the existing locking area generation principle, the positioning principle of this utility model can not only form a linear locking interface (the measured line width can be controlled within 0.5m), but also directly distinguish the movement direction of the located object from the inside to the outside or from the outside to the inside. More importantly, signal strength is very easily affected by environmental interference. Using an absolute threshold as the judgment condition, the effective coverage area of ​​the antenna (the area greater than the threshold) will change under different weather conditions, whether there are pedestrians walking, or whether there are objects blocking the signal, resulting in poor stability. An antenna that can cover the entire target area under good conditions may no longer be able to cover the entire target area under poor conditions, leading to loopholes in anti-theft measures. The positioning antenna based on a four-quadrant distribution structure proposed in this invention receives signals from the same source at the same time using directional antennas at different angles at the same location. The signal orientation is obtained through vector operations. External influences on signal transmission exist collectively for each antenna; that is, the RSSI value of each antenna increases or decreases under environmental influences. This uniform increase or decrease is eliminated during vector operations. Therefore, this method effectively solves the problem of environmental influence in existing technologies. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a PCB directional antenna.

[0028] Figure 2 for Figure 1 The horizontal radiation pattern of the PCB directional antenna is shown.

[0029] Figure 3 for Figure 1 The diagram shows the effective horizontal coverage area of ​​the PCB directional antenna.

[0030] Figure 4 This is a schematic diagram of the first positioning antenna based on a four-quadrant distribution structure.

[0031] Figure 5 This is a schematic diagram of the second type of positioning antenna based on a four-quadrant distribution structure.

[0032] Figure 6 This is a schematic diagram of the third type of positioning antenna based on a four-quadrant distribution structure.

[0033] Figure 7 This is a schematic diagram of the fourth type of positioning antenna based on a four-quadrant distribution structure.

[0034] Figure 8 This is a schematic diagram of the fifth type of positioning antenna based on a four-quadrant distribution structure.

[0035] Figure 9 This is a schematic diagram of the effective coverage area of ​​a directional antenna.

[0036] Figure 10 This is a schematic diagram of the effective coverage area of ​​a positioning antenna based on a four-quadrant distribution structure.

[0037] Figure 11 This is a schematic diagram illustrating the setup method for a positioning antenna based on a four-quadrant distribution structure in practical applications.

[0038] Figure 12 This is a schematic diagram illustrating the setup of a positioning antenna based on a four-quadrant distribution structure for use in an open parking lot. Detailed Implementation

[0039] The technical solution claimed in this utility model will be further described below with reference to the accompanying drawings and examples.

[0040] Figure 1 The image shows a PCB directional antenna 101. The PCB is rectangular, and the antenna's radiation direction is along the length of the PCB. The PCB is placed vertically for use, and the antenna's horizontal radiation pattern is shown below. Figure 2 As shown, its beam lobe 102 is oval in shape, with a beamwidth of 70 degrees. In use, the effective horizontal coverage area 103 of the antenna has the same shape as the beam lobe, and the effective horizontal coverage area 103 is symmetrical along the centerline, as shown... Figure 3 As shown.

[0041] Figure 4-8 The positioning antennas shown are examples of several positioning antennas based on a four-quadrant distribution structure.

[0042] Figure 4 The positioning antenna shown consists of four identical directional antennas. The first directional antenna 400, the second directional antenna 401, the third directional antenna 402, and the fourth directional antenna 403 are centrally positioned in the first, second, third, and fourth quadrants of the coordinate system at angles of 45°, 135°, 225°, and 315°, respectively. The four directional antennas are located on the same circumference, and their radiation direction is radially outward from the origin of the coordinate system.

[0043] Figure 5 The positioning antenna shown also consists of four identical directional antennas, and... Figure 2 , 3The example shown differs in that the four antennas are not centrally located in the four quadrants. Instead, the first directional antenna 404, the second directional antenna 405, the third directional antenna 406, and the fourth directional antenna 407 are arranged in a 90° rotationally symmetrical structure in the first, second, third, and fourth quadrants of the coordinate system, respectively, with orientations of 30°, 120°, 210°, and 300°. The four directional antennas lie on the same circle, and their radiation direction is radially outward from the origin of the coordinate system.

[0044] Figure 6 The positioning antenna shown consists of eight identical directional antennas, which are not centrally located in the four quadrants and do not form a 90° rotationally symmetrical structure. The eight directional antennas are situated on the same circle, with their radiation directions all radially outward from the origin of the coordinate system.

[0045] Figure 7 The positioning antenna shown consists of six identical directional antennas. The first directional antenna 408 and the second directional antenna 411 are centrally positioned in the first and third quadrants of the coordinate system, respectively, at 45° and 225° angles. The third directional antenna 409 and the fourth directional antenna 410 are evenly spaced in the second quadrant, with the third directional antenna 409 making a 30° angle with the Y-axis and the fourth directional antenna 410 making a 60° angle with the Y-axis. The fifth directional antenna 412 and the sixth directional antenna 413 are evenly spaced in the fourth quadrant, with the fifth directional antenna 412 making a 30° angle with the Y-axis and the sixth directional antenna 413 making a 60° angle with the Y-axis. These eight directional antennas form a 180° rotationally symmetric structure, located on the same circle, with their radiation direction radially outward from the origin of the coordinate system.

[0046] Figure 8 The positioning antenna shown consists of eight identical directional antennas. These eight antennas are not centrally located in the four quadrants, but are evenly spaced within the coordinate system. The angle between any two adjacent directional antennas is 45°, and the eight antennas form a 45° rotationally symmetric structure. All eight antennas are located on the same circle, and their radiation direction is radially outward from the origin of the coordinate system. Each quadrant has two directional antennas, and the eight antennas are symmetric about the x-axis and y-axis.

[0047] Figure 9 The image shows a directional antenna whose effective coverage area includes the area behind it, but the gain at the front is significantly greater than that at the sides and rear. Four such directional antennas can be used to form a positioning antenna with a four-quadrant distribution structure, for example... Figure 10 The positioning antenna shown can locate the target when each directional antenna can receive the positioning signal.

[0048] Figure 11This diagram illustrates the placement of the positioning antennas in the practical application of the vector-based shopping cart control system of this invention. The entrance / exit 510 shown in the diagram can be the entrance / exit of a closed parking lot, the entrance of a supermarket, or the entrance to a shopping area, etc. In this example, a first positioning antenna 505 and a second positioning antenna 506 are respectively installed at both ends of the entrance / exit 510. The first vertical plane d1 of the first positioning antenna 505 and the second positioning antenna 506 overlaps and corresponds to the boundary line set at the entrance / exit 510 that prohibits the cart from exiting.

[0049] Figure 12 This is a schematic diagram illustrating one configuration of the positioning antenna in the shopping cart anti-theft system based on vector operations of this utility model, used in an open parking lot. The parking lot boundary is divided into several straight segments, and a first positioning antenna 507 and a second positioning antenna 508 are respectively set at both ends of each straight segment. Two connected straight segments share one positioning antenna.

Claims

1. A positioning antenna based on a four-quadrant distribution structure, characterized in that, It includes multiple identical directional antennas, which are circumferentially distributed at the same horizontal height with the intersection of two mutually perpendicular vertical planes as the central axis. The radiation direction of each directional antenna is radially outward with the central axis as the center. The vertical projection of the two vertical planes divides the horizontal plane into four quadrants, and each quadrant has at least one directional antenna.

2. The positioning antenna based on a four-quadrant distribution structure according to claim 1, characterized in that, The directional antenna comprises four groups, each located in one of the four quadrants. The four groups of antennas form a 90-degree rotationally symmetrical structure with the intersection of two vertical planes as the central axis.

3. The positioning antenna based on a four-quadrant distribution structure according to claim 2, characterized in that, The four antennas form a centrally symmetrical structure with the intersection of the two vertical planes as the central axis.

4. The positioning antenna based on a four-quadrant distribution structure according to claim 3, characterized in that, The four antennas form a ring array structure with the intersection of the two vertical planes as the central axis.

5. The positioning antenna based on a four-quadrant distribution structure according to claim 1, characterized in that, It also includes directional antennas mounted on a vertical plane.

6. A positioning antenna based on a four-quadrant distribution structure, characterized in that, It includes multiple identical directional antennas, which are circumferentially distributed at the same horizontal height with the intersection of two mutually perpendicular vertical planes as the central axis. The radiation direction of each directional antenna is radially outward with the central axis as the center. The vertical projection of the two vertical planes divides the horizontal plane into four quadrants. The directional antennas include four groups, all of which are set on the two vertical planes, and the four groups of directional antennas form a 90-degree rotationally symmetrical structure with the intersection of the two vertical planes as the central axis.

Images