Positioning antenna based on single vertical plane symmetry structure

Abstract

The utility model discloses a positioning antenna based on single vertical plane symmetry structure, including setting together at least a pair of directional antenna, two directional antennas in each pair of directional antenna are same, and along the same heavy straight face each other symmetry setting, two directional antennas in at least a pair of directional antenna's horizontal plane effective coverage area partially overlap. The positioning principle of the utility model compares with the generation principle of the locking area of prior art, not only can form the locking interface of projection as line, but also can directly distinguish the movement direction of the object from inside to outside or from outside to inside. The RSSI value of both sides antenna under the influence of environment, also increase or reduce, and this same increase and reduce are eliminated when calculating the difference. Therefore can effectively solve the problem of prior art affected by environment.

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 relative to a target vertical plane (such as the vertical projection line and the double vertical plane corresponding to the boundary of a supermarket parking lot), as well as various applications.

[0008] This invention first proposes a symmetrical positioning antenna unit, comprising two identical directional antennas arranged together with different orientations. The two directional antennas are symmetrically arranged along a straight plane, and the included angle (in their maximum radiation directions) satisfies the condition that the effective horizontal coverage areas of the two directional antennas partially overlap. Here, the effective coverage area refers to the signal coverage range within which the antenna can effectively transmit data to the target. Structurally, "arranged together" means that the two directional antennas are mounted on the same carrier, even if this carrier is detachable; at least in use, the carrier is a single unit. Effectively, it means that for the target object communicating with the positioning antenna, the two directional antennas can be considered to be communicating with the target object at the same point; that is, compared to the distance between the positioning antenna and the target object during operation, the distance between the two directional antennas is negligible. The above explanation regarding "arranged together" applies to every instance of "arranged together" mentioned below.

[0009] When the aforementioned positioning antenna unit is used to locate the object being located, it can be used as a transmitter or a receiver.

[0010] When using the transmitter, the positioning principle is as follows: two directional antennas transmit signals of the same power for positioning (hereinafter referred to as positioning signals) from the same point. The object being positioned receives the positioning signals emitted by the two directional antennas. Since the two directional antennas are symmetrical along the vertical plane of the positioning antenna but have different orientations, when the object being positioned is on the vertical plane of the positioning antenna, the received signal strength (RSSI) of the positioning signals received by the object from the two directional antennas is the same. When the object being positioned is not on the vertical plane of the positioning antenna, the RSSI values ​​of the positioning signals received by the object from the two directional antennas will be different. By comparing the RSSI values ​​of the positioning signals from the two directional antennas, it can be determined whether the object being positioned is located on the vertical plane of the positioning antenna or is biased towards one side of the vertical plane of the positioning antenna.

[0011] When used as a receiver, its positioning principle is as follows: two directional antennas receive the same positioning signal emitted by the object being positioned at the same time from the same point. Since the two directional antennas are symmetrical along the vertical plane of the positioning antenna but have different orientations, when the object being positioned is on the vertical plane of the positioning antenna, the RSSI values ​​of the positioning signals received by the two directional antennas are the same. When the object being positioned is not on the vertical plane of the positioning antenna, the RSSI values ​​of the positioning signals received by the two directional antennas will be different. By comparing the RSSI values ​​of the positioning signals received by the two directional antennas, it can be determined whether the object being positioned is located on the vertical plane of the positioning antenna or is biased towards one side of the vertical plane of the positioning antenna.

[0012] Since the two directional antennas communicate with the target object at the same point, the influence of the external environment on signal transmission exists for both antennas. This means that the RSSI values ​​of the positioning signals received by both antennas will increase or decrease under the influence of the external environment, and this increase or decrease will be eliminated during comparison (difference calculation). Therefore, this symmetrical positioning antenna can effectively solve the problem of inaccurate positioning results caused by the influence of the external environment on wireless signal transmission in existing technologies.

[0013] Comparing the positioning principles used for the transmitting and receiving ends reveals that when used as a transmitting antenna, to enable the target object to identify which directional antenna the received positioning signal originates from, separate identification information needs to be configured for each directional antenna. This results in the target object receiving positioning signals from different directional antennas not being the same signal emitted from the same source at the same time. However, when the positioning antenna is used as a receiving antenna, all directional antennas can simultaneously receive the same positioning signal emitted from the same source at the same time from the target object. Therefore, the positioning antenna unit of this invention is more suitable for use at the receiving end to achieve better positioning results.

[0014] According to the positioning principle of the positioning antenna unit of this utility model, when the object to be positioned is close to the vertical plane of the positioning antenna, both directional antennas must be able to successfully receive the positioning signal emitted by the object, or the positioning signals emitted by both directional antennas must be successfully received by the object. Therefore, when the object to be positioned is close to the vertical plane of the positioning antenna, the effective horizontal coverage areas of the two directional antennas should respectively cover the object. Thus, the positioning antenna unit of this utility model requires that the effective horizontal coverage areas of the two directional antennas partially overlap on both sides of the vertical plane of the target. Ideally, the shape of the effective horizontal coverage area of ​​a directional antenna is the same as the shape of its horizontal radiation pattern lobe. Theoretically, when setting up two directional antennas, by partially overlapping the horizontal radiation pattern lobes of the directional antennas, the partial overlap of the effective horizontal coverage areas of the two directional antennas can be achieved. However, it is understandable that since the radiation pattern is an idealized simulation result, based on the working principle of the positioning antenna unit of this utility model, when setting up two directional antennas, it is best to test the actual effective coverage area of ​​the directional antennas through experiments, and then use the beamwidth of the simulated radiation pattern as a reference to determine the appropriate angle range between the two directional antennas according to the actual tested effective coverage area.

[0015] This invention provides a relatively simple method for determining the included angle between two directional antennas: the horizontal included angle between the two directional antennas is equal to or approximately equal to the horizontal beamwidth of the directional antenna.

[0016] In practical applications, the positioning antenna unit of this invention can be directly configured as a positioning antenna based on a single vertical plane symmetric structure and directly used as a receiving or transmitting antenna in a positioning device.

[0017] For example, a positioning device can be formed by combining a positioning antenna unit as a receiving antenna with a receiving and processing control unit. The object to be positioned is equipped with an omnidirectional transmitting antenna and a transmitting control unit to form the transmitting end. The transmitting control unit generates a positioning signal and broadcasts it through the omnidirectional transmitting antenna. The positioning antenna outputs the positioning signals received by its two directional antennas to the receiving and processing control unit. The receiving and processing control unit calculates and compares the RSSI values ​​of the positioning signals received by the two directional antennas, and then determines the relative position of the object to be positioned relative to the vertical plane of the positioning antenna based on the comparison results. In this example, the receiving and processing control unit preferably includes two signal processing modules (preferably a Bluetooth communication module) and a controller (preferably an MCU). Each of the two directional antennas of the positioning antenna is connected to a signal processing module, and the two signal processing modules are connected to the controller. The two signal processing modules calculate and output the RSSI values ​​of the positioning signals received by the two directional antennas. The controller compares the RSSI values ​​of the signals received by the two directional antennas and determines the relative position of the object to be positioned.

[0018] The positioning antenna unit of this utility model can also be used to construct a receiving or transmitting antenna, which can then be further used in a positioning device.

[0019] For example, multiple positioning antenna units of this invention can be combined to form a first novel positioning antenna based on a single vertical plane symmetry structure. This includes multiple pairs (two or more pairs) of directional antennas arranged together. The two positioning antennas in each pair are identical and symmetrically arranged along the same vertical plane. The effective horizontal coverage areas of the two directional antennas in each pair partially overlap. Here, each pair of directional antennas constitutes a positioning antenna unit of this invention. Further, this novel positioning antenna based on a single vertical plane symmetry structure can be combined with a receiving and processing control unit to form a positioning device. The positioning antenna outputs the positioning signals received by its multiple pairs of directional antennas to the receiving and processing control unit. The receiving and processing control unit calculates the RSSI value of the positioning signal received by each directional antenna and compares the RSSI values ​​of the directional antennas located on both sides of the vertical plane of the positioning antenna. Based on the comparison results, the relative position of the object being positioned relative to the vertical plane of the positioning antenna is determined.

[0020] There are several comparison methods available. For example, the first method is to add up the RSSI values ​​of all directional antennas on one side of the vertical plane of the positioning antenna and compare them with the sum of the RSSI values ​​of all directional antennas on the other side. Alternatively, the RSSI values ​​of each pair of directional antennas can be compared separately, and the final comparison result can be obtained based on the individual comparison results of each pair of directional antennas. (For example, when all individual comparison results are consistent (e.g., the RSSI value of the first directional antenna in each pair is greater than the RSSI value of the second directional antenna), the consistent result is taken as the final comparison result; if they are inconsistent, the positioning is considered to have failed.) Another example is the second method, which uses the majority of individual comparison results as the final comparison result. (e.g., if there are three pairs of directional antennas, and the RSSI values ​​of the first directional antennas in two pairs are greater than the RSSI values ​​of the second directional antennas, while the RSSI value of the first directional antenna in another pair is less than the RSSI value of the second directional antenna, then the final comparison result is that the RSSI value of the first directional antenna is greater than the RSSI value of the second directional antenna, thus determining that the object being positioned is currently located on the first side of the vertical plane of the positioning antenna.)

[0021] For example, based on the positioning antenna unit of this utility model, additional directional antennas can be added to form a second new positioning antenna based on a single vertical plane symmetry structure. This includes multiple pairs (two or more pairs) of directional antennas arranged together, with two identical directional antennas in each pair, symmetrically arranged along the same vertical plane. At least one pair of directional antennas has a partially overlapping horizontal effective coverage area. Here, the at least one pair of directional antennas with partially overlapping horizontal effective coverage areas is the positioning antenna unit of this utility model. Furthermore, this second positioning antenna based on a single vertical plane symmetry structure can be combined with a receiving antenna and a receiving processing control unit to form a positioning device. The positioning antenna outputs the positioning signals received by its multiple pairs of directional antennas to the receiving processing control unit. The receiving processing control unit calculates the RSSI value of the positioning signal received by each directional antenna and compares the RSSI values ​​of the directional antennas located on both sides of the vertical plane of the positioning antenna. Based on the comparison results, the relative position of the object being positioned relative to the vertical plane of the positioning antenna is determined.

[0022] Depending on the specific addition of directional antennas, there are several comparison methods available. In the first case, the effective horizontal coverage areas of the two directional antennas in each pair of added antennas partially overlap. This is the same as the case described above where multiple positioning antenna elements are combined to form a positioning antenna, and the various comparison methods exemplified above can be applied. In the second case, among the added pairs of directional antennas, the effective horizontal coverage areas of the two directional antennas in one or more pairs do not overlap. If the non-overlapping directional antennas cannot simultaneously receive signals from the target object, they are not suitable for individual comparison. When setting comparison rules, the RSSI values ​​of the non-overlapping directional antenna pairs can be added to the RSSI values ​​of one or more overlapping directional antenna pairs on the same side and compared. This comparison is then combined with other individual comparison results to determine the final comparison result. Alternatively, the authenticity of the individual or combined comparison results of other overlapping directional antenna pairs can be determined based on the RSSI values ​​of the non-overlapping directional antenna pairs, thereby determining the final comparison result (e.g., if the RSSI value comparison result of the overlapping directional antenna pairs is that the RSSI value of the first directional antenna is greater than that of the second directional antenna, but the first directional antenna in the non-overlapping directional antenna pairs does not receive a signal, then the individual or combined comparison results of other overlapping directional antenna pairs are considered incorrect, and the positioning fails). In the third case, all additional directional antenna pairs have horizontal effective coverage areas that do not overlap. When setting comparison rules, the RSSI values ​​of the non-overlapping pair of directional antennas can be added together with the RSSI values ​​of the pair of directional antennas constituting the positioning antenna unit on the same side, and then the two sides can be compared to obtain the final comparison result. Alternatively, the authenticity of the comparison result of the RSSI values ​​of the pair of directional antennas constituting the positioning antenna unit can be determined based on the RSSI values ​​of the non-overlapping pair of directional antennas, and then the final comparison result can be determined.

[0023] It can be noted that the second new type of positioning antenna, which is based on the positioning antenna unit of this utility model and additionally includes other directional antennas, includes the case of the first new type of positioning antenna formed by combining multiple positioning antenna units of this utility model.

[0024] Based on the various comparison methods described above, it can be seen that regardless of the situation (whether it's a comprehensive judgment of the results of comparing multiple pairs of directional antennas individually; or incorporating the RSSI value of the additional directional antenna into the comparison; or judging the authenticity of the comparison result based on the RSSI value of the additional directional antenna), more directional antennas can effectively correct the judgment errors that may occur when directly using a single positioning antenna element as the directional antenna. Therefore, although multiple pairs of directional antennas increase the cost of the positioning antenna, they can achieve better positioning results.

[0025] For ease of description, the examples above primarily use the positioning antenna as a receiving antenna. If the positioning antenna is used as a transmitting antenna, the structures and comparison methods for various positioning antennas based on a single vertical plane symmetry structure described above are equally applicable. The difference is that the signal transmission direction is reversed. In this case, the positioning device is formed by combining the positioning antenna as a transmitting antenna and a transmission control unit, while the object being positioned is configured with an omnidirectional receiving antenna and a receiving processing control unit to form the receiving end. The transmitting control unit generates positioning signals containing the identification information of the corresponding directional antennas and distributes them accordingly to each directional antenna of the positioning antenna. The receiving processing control unit at the receiving end calculates the RSSI value of the positioning signal from each directional antenna, compares them, and then determines the relative position of the object being positioned relative to the vertical plane of the positioning antenna based on the comparison results.

[0026] Based on the positioning principle of the positioning antenna unit of this utility model, it is known that the key to achieving positioning lies in the comparability of RSSI values, that is, the relative magnitude of the RSSI value is consistent with the relative position of the object being positioned relative to the target vertical plane. Correspondingly, its core structural feature is that the directional antenna is symmetrical with respect to the vertical plane. Therefore, it can be inferred that, in addition to the aforementioned examples, any positioning antenna with a symmetrical structure, extended from the positioning antenna unit of this utility model, can achieve the determination of the relative position of the object being positioned relative to the target vertical plane as described in this utility model.

[0027] It is also conceivable that any positioning antenna that includes the positioning antenna unit of this utility model (i.e., two identical directional antennas that are symmetrically arranged along the vertical plane and whose effective coverage area on the horizontal plane partially overlaps) and that uses the comparison of the RSSI values ​​of the symmetrical directional antennas to locate the relative position of the object to be positioned relative to the target vertical plane should be considered an application of the positioning antenna unit of this utility model.

[0028] The following are some other special applications of the positioning antenna unit of this utility model.

[0029] The first, rather unique application scenario is as follows: Based on the positioning antenna unit of this utility model, an omnidirectional antenna is set at the structural center of the positioning antenna to form a positioning antenna, and the RSSI value of the omnidirectional antenna is used as the condition for performing the comparison.

[0030] The second, more unique application scenario involves setting up three directional antennas in different orientations around the intersection point of two intersecting vertical planes to form a positioning antenna. The first and second directional antennas are symmetrical along the first vertical plane, forming a positioning antenna unit of this invention. The second and third directional antennas are symmetrical along the second vertical plane, also forming a positioning antenna unit of this invention.

[0031] The third, more unique application scenario involves four directional antennas arranged in different orientations around the intersection of two intersecting vertical planes, forming a positioning antenna. The first and second directional antennas, with the first vertical plane as their plane of symmetry, constitute one positioning antenna unit of this invention. The second and third directional antennas, with the second vertical plane as their plane of symmetry, also constitute one positioning antenna unit of this invention. The third and fourth directional antennas, with the first vertical plane as their plane of symmetry, also constitute one positioning antenna unit of this invention. The fourth directional antenna and the first directional antenna, with the second vertical plane as their plane of symmetry, also constitute one positioning antenna unit of this invention.

[0032] Preferably, all the aforementioned positioning antennas based on a single vertical plane structure are mounted on the same carrier. The horizontal angle between a pair of directional antennas whose effective horizontal coverage areas partially overlap is within ±10° of the horizontal beamwidth. Based on the aforementioned positioning antenna unit and positioning antennas based on a single vertical plane symmetrical structure, as well as various comparison methods, this invention preferably uses the positioning antenna as the receiving antenna. Further, it claims a positioning method based on single vertical plane comparison for determining the relative position of the object to be positioned relative to a target vertical plane. This method uses the object to be positioned as the signal transmitter, and pairs of directional antennas are set along the target vertical plane as receivers. The two directional antennas in the pair are identical and symmetrically arranged along the target vertical plane. The horizontal angle between the two directional antennas in the pair is set so that the effective horizontal coverage areas of at least two of the directional antennas in a pair partially overlap. By comparing the RSSI values ​​of the same signal emitted by the object and received by the directional antennas on both sides of the target vertical plane, it is determined which side of the target vertical plane the object is located on.

[0033] The following section lists several typical comparison methods for different settings of directional antennas.

[0034] The first method involves setting two identical directional antennas symmetrically along the target plane, and setting the horizontal angle between the two directional antennas so that the effective coverage areas of the two directional antennas partially overlap.

[0035] The positioning method compares the RSSI values ​​of the same signal emitted by the target object received by two directional antennas to determine which side of the target's vertical plane the target object is located on. The side of the directional antenna with the larger RSSI value is the side where the target object is currently located.

[0036] The second method involves symmetrically setting at least two pairs of directional antennas along the target's horizontal plane. The two antennas in each pair are identical and symmetrical along the target's horizontal plane. The horizontal angle between each pair of directional antennas is set so that the effective horizontal coverage areas of at least two antennas in one pair partially overlap.

[0037] By comparing the sum of the RSSI values ​​of the same signal emitted by the target object and received by directional antennas on both sides of the target's vertical plane, it can be determined which side of the target's vertical plane the target object is located on. The side of the directional antenna with the larger sum of RSSI values ​​is the side where the target object is currently located.

[0038] The third method involves symmetrically setting at least two pairs of directional antennas along the target's horizontal plane. The two antennas in each pair are identical and symmetrical along the target's horizontal plane. The horizontal angle between each pair of directional antennas is set so that the effective horizontal coverage areas of the two antennas in each pair partially overlap.

[0039] The RSSI values ​​of the same signal emitted by the target object and received by the two directional antennas in each pair of directional antennas are compared. The final comparison result is the one where all values ​​are consistent or the majority value is obtained, which determines which side of the vertical plane the target object is located on. The side of the directional antenna with the larger RSSI value in the final comparison result is the side where the target object is currently located.

[0040] Based on the aforementioned positioning method based on single vertical plane comparison, this utility model further claims a positioning system based on single vertical plane comparison, including a positioning device and a target object. The target object is equipped with a signal transmitter. The positioning device includes a positioning antenna disposed on the target vertical plane and a receiving and processing control unit configured for the positioning antenna. The positioning antenna is a positioning antenna based on a single vertical plane symmetrical structure, including at least one pair of directional antennas disposed together. Two directional antennas in each pair are identical and symmetrically arranged along the target vertical plane. The effective horizontal coverage areas of the two directional antennas in at least one pair partially overlap. The receiving and processing control unit includes a signal processing module equal in number to the directional antennas and a controller for positioning determination. Each directional antenna is connected to a signal processing module, and each signal processing module is connected to the controller. Each signal processing module calculates and outputs the RSSI value of the signal received by the connected directional antenna to the controller. The controller compares the RSSI values ​​of the same signal emitted by the target object received by the directional antennas on both sides of the target vertical plane and determines which side of the target vertical plane the target object is located on based on the comparison result.

[0041] Alternatively, the positioning antenna may consist of only a pair of directional antennas. The controller compares the RSSI values ​​of the same signal emitted by the object being located, received by the two directional antennas in the pair, and determines the side where the directional antenna with the larger RSSI value is located as the current location of the object being located.

[0042] Alternatively, the positioning antenna includes multiple pairs of directional antennas, with at least two of the directional antennas having partially overlapping horizontal effective coverage areas. The controller compares the sum of the RSSI values ​​of the signals received by the directional antennas on one side of the horizontal plane with the sum of the RSSI values ​​of the signals received by the directional antennas on the other side of the horizontal plane. The side containing the directional antennas with the larger sum of RSSI values ​​is determined to be the current location of the object being located.

[0043] Alternatively, the positioning antenna includes multiple pairs of directional antennas, with the effective horizontal coverage areas of two directional antennas in each pair partially overlapping. The controller compares the RSSI values ​​of the same signal emitted by the object being located, received by the two directional antennas in each pair. When the RSSI values ​​of all or most of the directional antennas on one side are greater than the RSSI values ​​of the symmetrical directional antennas, that side is determined to be the side where the object being located is currently located.

[0044] Furthermore, the included angle of each pair of positioning antennas is different.

[0045] This invention further claims a shopping cart control method based on single vertical plane comparison, using the aforementioned positioning method based on single vertical plane comparison. The method uses the shopping cart as the object to be positioned, and includes a braking mechanism on the cart to restrict its movement. The cart is also equipped with functions for receiving commands and sending positioning signals. A positioning antenna with a single vertical plane symmetrical structure is set along the boundary preventing the cart from being pushed out, receiving the positioning signal emitted by the cart. The vertical plane of the positioning antenna corresponds to the boundary preventing the cart from being pushed out. By comparing the RSSI values ​​of the positioning signals received from the shopping cart by the directional antennas on both sides of the vertical plane of the positioning antenna, it is determined which side of the boundary preventing the cart from being pushed out is on. When the shopping cart is positioned outside the boundary preventing the cart from being pushed out, or based on positioning results at different times, it is determined that the shopping cart has moved from inside to outside the boundary preventing the cart from being pushed out, and a locking command is sent to the shopping cart. Upon receiving the locking command, the shopping cart activates the braking mechanism to lock the cart.

[0046] 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 the boundary 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.

[0047] Furthermore, considering the limited effective range of the positioning antenna, when the width of the boundary preventing shopping cart ejection is less than the effective range of the positioning antenna—for example, for controlling shopping carts at supermarket entrances, shopping area entrances, checkout lanes, or entrances / exits of enclosed parking lots (where barriers prevent shopping cart ejection along the parking lot boundary, with only a few entrances / exits for vehicles and / or pedestrians)—a positioning antenna based on a single vertical symmetrical structure can be installed at one end of the boundary preventing shopping cart ejection, with its direction of action facing the other end. The effective range of this antenna covers the width of the boundary preventing shopping cart ejection. Alternatively, two positioning antennas based on a single vertical symmetrical structure can be installed at each end of the boundary preventing shopping cart ejection, with their directions of action opposite each other. The sum of the effective ranges of the two antennas covers the width of the boundary preventing shopping cart ejection. Alternatively, the effective range of each positioning antenna can cover the width of the boundary, and the final positioning result from both antennas can be used to control the locking or unlocking of the shopping cart.

[0048] When the width of the boundary preventing shopping carts from being pushed out is greater than the effective range of the positioning antenna, such as for shopping cart control at the boundary of an open parking lot, positioning antennas based on a single vertical plane symmetrical structure can be set at intervals along the boundary of the parking lot. When selecting the setting points of the positioning antennas, the boundary between every two positioning antennas should be a straight boundary. The interval between two positioning antennas can be covered by the effective range of one of the positioning antennas, or it can be covered by half of the effective range of each of the two positioning antennas, or it can be covered by the effective range of both positioning antennas at the same time.

[0049] Based on the aforementioned shopping cart control method based on single vertical plane comparison, this utility model further claims a shopping cart control system based on single vertical plane comparison, 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 that can limit the movement of the shopping cart, and a signal transceiver for sending positioning signals and receiving control commands.

[0050] The base station includes a positioning antenna for receiving positioning signals, a signal processing module with the same number of directional antennas as the positioning antenna, and a controller for positioning judgment and generating control commands. Optionally, the base station also includes a transmitting antenna for sending control commands (if no transmitting antenna is provided, the control commands can also be sent through one of the directional antennas in the positioning antenna).

[0051] The positioning antenna is the aforementioned positioning antenna based on a single vertical plane symmetrical structure. The positioning antenna is positioned along the boundary line preventing the shopping cart from being pushed out, with the vertical plane of the positioning antenna corresponding to the boundary line. 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 the connected directional antenna. Each signal processing module is connected to a controller. The controller compares the RSSI values ​​of the positioning signals from the shopping cart received by the directional antennas on both sides of the vertical plane of the positioning antenna to determine which side of the boundary line preventing the shopping cart from being pushed out. When the shopping cart is positioned outside the boundary line, or, based on positioning results at different times, it is determined that the shopping cart has moved from inside to outside the boundary line, the base station sends a locking command to the shopping cart. The shopping cart receives and responds to the locking command, activating the braking mechanism to lock the shopping cart.

[0052] Furthermore, when multiple positioning antennas are required, for example, one positioning antenna can be installed on each side of the entrance and exit of a closed parking lot, or multiple positioning antennas can be installed at intervals along the boundary of an open parking lot. The base station can be configured in the following two ways.

[0053] The first setup method: Connect all positioning antennas to a controller to form a base station.

[0054] In this configuration, the controller compares and judges the RSSI value for each positioning antenna. It can then choose to issue a control command only when the judgment result of any one positioning antenna meets the control condition, or when the judgment results of multiple positioning antennas meet the control condition simultaneously.

[0055] The second setup method: Each positioning antenna or several positioning antennas are grouped together and connected to a controller to form a base station.

[0056] In this configuration, multiple base stations can operate independently, with each base station's controller comparing and judging the RSSI values ​​of its connected positioning antenna and issuing control commands based on the results. Alternatively, multiple base stations can work collaboratively, with each base station outputting its judgment results to a central controller, which then makes control decisions based on the judgment results from all base stations. As an option, one base station can be selected as the primary base station, and the others as secondary base stations, with the primary base station's controller serving as the central controller. All secondary base stations communicate with the primary base station separately (through additional communication modules and antennas). Alternatively, a separate central controller can be set up independently of each base station, with all secondary base stations communicating with the central controller separately (through additional communication modules and antennas).

[0057] One can imagine: By setting the above-mentioned shopping cart control system based on single vertical plane comparison along the boundary of the parking lot or at the entrance and exit of the parking lot, a shopping cart anti-theft system based on single vertical plane comparison is formed, which can effectively prevent shopping carts from being pushed out of the supermarket area. By setting the shopping cart control system based on single vertical plane comparison 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 product anti-theft system based on single vertical plane comparison is formed, which can effectively prevent unchecked products from being stolen by pushing out the shopping cart. By setting the shopping cart control system based on single vertical plane comparison at the entrance of the supermarket shopping area, and using "the shopping cart moving from the inside to the outside of the boundary where shopping carts are prohibited from being pushed out" as the condition for issuing the locking command, a shopping cart reverse-movement control system based on single vertical plane comparison is constituted, which can prevent customers from pushing the shopping cart out of the shopping area entrance in the reverse direction.

[0058] The beneficial effects of this invention are as follows: Compared with the existing technology's locking area generation principle, the positioning principle of this invention 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 a 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 view, resulting in poor stability. Under good conditions, an antenna that can cover the entire target area may no longer be able to cover the entire target area under poor conditions, leading to loopholes in anti-theft measures. The RSSI value comparison method of the two antennas proposed in this invention addresses the issue that since the antennas on both sides of the vertical plane receive signals from the same source at the same time, the influence of external factors on signal transmission exists on both antennas. That is, the RSSI values ​​of both antennas increase or decrease under environmental influences, and this same increase or decrease is eliminated when calculating the difference. Therefore, this method can effectively solve the problem of environmental influence in existing technologies. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of a PCB directional antenna.

[0060] Figure 2 for Figure 1 The horizontal radiation pattern of the PCB directional antenna is shown.

[0061] Figure 3 for Figure 1 The diagram shows the effective horizontal coverage area of ​​the PCB directional antenna.

[0062] Figure 4 This is a schematic diagram of the first type of positioning antenna unit.

[0063] Figure 5 This is a schematic diagram of the second type of positioning antenna unit.

[0064] Figure 6 This is a schematic diagram of the third type of positioning antenna unit.

[0065] Figure 7 This is a schematic diagram of the first type of positioning antenna based on a single vertical plane symmetrical structure.

[0066] Figure 8 This is a schematic diagram of the second type of positioning antenna based on a single vertical plane symmetrical structure.

[0067] Figure 9 This is a schematic diagram of the third type of positioning antenna based on a single vertical plane symmetrical structure.

[0068] Figure 10 This is a schematic diagram of the fourth type of positioning antenna based on a single vertical plane symmetric structure.

[0069] Figure 11 This is a schematic diagram of the fifth type of positioning antenna based on a single vertical plane symmetric structure.

[0070] Figure 12 This is a schematic diagram of the sixth type of positioning antenna based on a single vertical plane symmetrical structure.

[0071] Figure 13 This is a schematic diagram of the seventh type of positioning antenna based on a single vertical plane symmetric structure.

[0072] Figure 14 This is a schematic diagram of the eighth type of positioning antenna based on a single vertical plane symmetrical structure.

[0073] Figure 15 This is a schematic diagram of the first positioning antenna setup based on a single vertical plane symmetrical structure.

[0074] Figure 16 This is a schematic diagram of the second type of positioning antenna setup based on a single vertical plane symmetrical structure.

[0075] Figure 17 This is a schematic diagram of the third type of positioning antenna setup based on a single vertical plane symmetrical structure.

[0076] Figure 18 This is a schematic diagram illustrating the installation method of a positioning antenna based on a single vertical plane symmetry structure in an open parking lot. Detailed Implementation

[0077] The technical solution claimed in this utility model will be further described below with reference to the accompanying drawings and examples.

[0078] 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.

[0079] Reference Figure 4 Two Figure 1 The directional antennas shown are symmetrically arranged along a vertical plane (shown by the center line) to form a positioning antenna unit 104 (1) of this invention. It can be directly used as a positioning antenna based on a single vertical plane symmetrical structure to locate which side of the target vertical plane the object is on. In this example, the angle between the two directional antennas is 70 degrees, which is exactly equal to the beamwidth of the directional antenna. As can be seen in the figure, the effective horizontal coverage area 103 of the two directional antennas overlaps at the center line representing the vertical plane.

[0080] Reference Figure 5 This example also uses two Figure 1 The directional antennas shown are symmetrically arranged along a vertical plane (shown by the center line) to form a positioning antenna unit 104 (2) as described in this utility model. In this example, the included angle between the two directional antennas is 90 degrees, which is greater than the beamwidth of the directional antennas. However, as can be seen in the figure, the effective horizontal coverage area 103 of the two directional antennas still overlaps to a certain extent at the center line used to represent the vertical plane. However, the effective range of the positioning antenna unit during positioning is greater than that of the directional antenna unit. Figure 4 The example shown is shorter.

[0081] Figure 6 The following is another example of the positioning antenna unit of this utility model. The directional antenna used in this example has a narrower beamwidth, and the corresponding effective coverage area is also narrower and longer. The directional antenna unit constructed in this way has a longer effective range when used to locate the oriented object.

[0082] Figure 7-14 The positioning antennas shown are examples of several positioning antennas based on a single vertical plane symmetric structure.

[0083] Figure 7The positioning antenna shown consists of four directional antennas. The first directional antenna 210 and the second directional antenna 211 form the first positioning antenna unit 201, with their operating direction pointing upwards along the centerline d1. The third directional antenna 212 and the fourth directional antenna 213 form the second positioning antenna unit 202, with their operating direction pointing upwards along the centerline d1. The entire positioning antenna operates with its operating direction pointing upwards along the centerline d1. This can be used to determine whether the object being positioned above the positioning antenna is located to the left or right of the target's vertical plane (corresponding to the centerline).

[0084] Figure 8 The positioning antenna shown also consists of four directional antennas. The first directional antenna 215 and the second directional antenna 216 form the first positioning antenna unit 203, with its direction of action pointing upwards along the centerline d1. The third directional antenna 217 and the fourth directional antenna 218 form the second positioning antenna unit 204, with its direction of action pointing downwards along the centerline d1. The entire positioning antenna operates both upwards and downwards along the centerline d1. This can be used to determine whether the object being positioned above or below the positioning antenna is located to the left or right of the target's vertical plane (corresponding to the centerline).

[0085] Figure 9 The positioning antenna shown consists of six directional antennas. The first directional antenna 219 and the second directional antenna 220 form the first positioning antenna unit 205, with their operating direction upwards along the centerline d1. The third directional antenna 221 and the fourth directional antenna 222 are symmetrical along the centerline d1 and are used for auxiliary judgment. The fifth directional antenna 223 and the sixth directional antenna 224 form the second positioning antenna unit 206, with their operating direction downwards along the centerline d1. The entire positioning antenna operates both upwards and downwards along the centerline d1. This can be used to determine whether the object being positioned above or below the positioning antenna is located to the left or right of the target's vertical plane (corresponding to the centerline). In this example, theoretically, the third directional antenna 221 and the fourth directional antenna 222 cannot simultaneously receive the positioning signal emitted by the object being positioned. When one of them receives the positioning signal, it can be basically determined that the object being positioned is located on the side of that directional antenna. By adding the RSSI values ​​of the third directional antenna 221 and the fourth directional antenna 222 to the comparison, misjudgments that may occur when using only the first directional antenna 219, the second directional antenna 220, the fifth directional antenna 223, and the sixth directional antenna 224 can be effectively corrected.

[0086] Figure 10The positioning antenna shown also consists of six directional antennas. The first directional antenna 225 and the second directional antenna 226 form the first positioning antenna unit 207, with their operating direction pointing upwards along the centerline d1. The third directional antenna 227 and the fourth directional antenna 228 form the second positioning antenna unit 208, with their operating direction pointing upwards along the centerline d1, and their angle is greater than the angle between the first directional antenna 225 and the second directional antenna 226. The fifth directional antenna 229 and the sixth directional antenna 230 form the third positioning antenna unit 209, with their operating direction pointing upwards along the centerline d1, and their angle is greater than the angle between the third directional antenna 227 and the fourth directional antenna 228. Combining three positioning antenna units of different sizes and angles allows the positioning effects of each unit to complement each other.

[0087] Figure 11 The positioning antenna shown consists of eight directional antennas, including four positioning antenna elements. The first directional antenna 231 and the second directional antenna 232 constitute the first positioning antenna element 250, with its direction of action pointing upwards along the centerline d1. The third directional antenna 233 and the fourth directional antenna 234 constitute the second positioning antenna element 251, with its direction of action pointing upwards along the centerline d1, and the angle between them is greater than the angle between the first directional antenna 231 and the second directional antenna 232. The fifth directional antenna 235 and the sixth directional antenna 236 constitute the third positioning antenna element 252, with its direction of action pointing downwards along the centerline d1, and the angle between them is equal to the angle between the first and second directional antennas 231 and 232. The angle between the three directional antennas 233 and the fourth directional antenna 234, and the seventh directional antenna 237 and the eighth directional antenna 238 constitute the fourth positioning antenna unit 253. The direction of action is downward along the centerline d1, and the angle between them is equal to the angle between the first directional antenna 231 and the second directional antenna 232. The two upper positioning antenna units have the direction of action upward along the centerline, use directional antennas of different sizes, and have different angles, so their positioning effects complement each other. The two lower positioning antenna units have the direction of action downward along the centerline, use directional antennas of different sizes, and have different angles, so their positioning effects complement each other.

[0088] Figure 12 The positioning antenna shown consists of four directional antennas and one omnidirectional antenna. The first directional antenna 239 and the second directional antenna 240 form the first positioning antenna element 254, with their operating direction pointing upwards along the centerline d1. The third directional antenna 242 and the fourth directional antenna 243 form the second positioning antenna element 255, with their operating direction pointing downwards along the centerline d1. The omnidirectional antenna 241 is located at the center of the positioning antenna structure and can be used to determine whether the object being located has entered the area to be located based on the RSSI value.

[0089] Figure 13The positioning antenna shown consists of six directional antennas. The first directional antenna 244 and the second directional antenna 245 form the first positioning antenna unit 256, with their operating direction pointing upwards along the centerline d1. The third directional antenna 246 and the fourth directional antenna 247 form the second positioning antenna unit 257, with their operating direction pointing downwards along the centerline d1. The fifth directional antenna 248 and the sixth directional antenna 249 are positioned on the centerline d1 (vertical plane). The fifth directional antenna 248 operates upwards along the centerline d1, and the sixth directional antenna 249 operates downwards along the centerline d1, respectively used to determine whether the object being positioned has entered the area to be positioned from above or below. The entire positioning antenna operates both upwards and downwards along the centerline d1.

[0090] Figure 14 The positioning antenna shown consists of four directional antennas. The first directional antenna 258 and the second directional antenna 259 are symmetrical along the vertical plane d1, forming the first positioning antenna element 262. The third directional antenna 260 and the fourth directional antenna 261 are symmetrical along the vertical plane d1, forming the second positioning antenna element 263. The first positioning antenna element 262 and the second positioning antenna element 263 use the same directional antennas and are set at the same angle, overlapping in the vertical direction. In use, the RSSI values ​​of the two antennas are compared individually. The positioning result is obtained if the comparison results of the two positioning antenna elements are the same, which can effectively reduce false positioning.

[0091] Figure 15-17 This diagram illustrates several ways to configure the positioning antenna in the practical application of the shopping cart control system based on single vertical plane symmetry of this utility model. 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. Taking a positioning antenna based on a single vertical plane symmetry structure composed of a single positioning antenna unit as an example, there are three possible configuration methods.

[0092] The first setup method: A positioning antenna 500 based on a single vertical symmetrical structure is installed at one end of the entrance / exit 510. The positioning antenna 500's direction of action is towards the other end, and its effective range covers the width of the entrance / exit 510. Figure 15 As shown.

[0093] The second setup involves installing a positioning antenna 501 with a single vertical symmetrical structure at each end of the entrance / exit 510. The two antennas 501 are positioned with their operating directions opposite each other, and the sum of their effective operating distances covers the width of the boundary line preventing the shopping cart from being pushed out. Figure 16 As shown.

[0094] The third configuration method: At each end of the entrance / exit 510, a positioning antenna 502 based on a single vertical plane symmetrical structure is installed. The two positioning antennas 502 are positioned with their operating directions opposite each other. The effective operating distance of each positioning antenna 502 covers the width of the boundary line prohibiting the shopping cart from being pushed out. Figure 17 As shown.

[0095] Based on this third setting method, the shopping cart can be locked or unlocked by using the same positioning result from both positioning antennas as the final positioning result.

[0096] Figure 18 This is a schematic diagram illustrating one configuration of the positioning antenna in a shopping cart anti-theft system based on a single vertical plane symmetry, used in an open parking lot. In this example, the parking lot 503 is rectangular, supported by a supermarket building 504, and its boundary is a semi-enclosed structure with three sides. A unidirectional positioning antenna 501 based on a single vertical plane symmetry is installed at each of the two endpoints of the boundary, with its direction of action pointing downwards along the side boundary. Two unidirectional positioning antennas 501 based on a single vertical plane symmetry are installed at each of the two corners of the boundary, one with its direction of action pointing upwards along the side boundary, and the other with its direction of action pointing towards the other corner along the bottom boundary. A bidirectional positioning antenna 501 based on a single vertical plane symmetry is installed in the middle of both the side and bottom boundaries, with its direction of action coinciding with the boundary.

Claims

1. A positioning antenna based on a single vertical plane symmetrical structure, characterized in that, It includes at least one pair of directional antennas set together, wherein the two directional antennas in each pair are identical and are symmetrically arranged along the same straight plane, and the effective horizontal coverage areas of the two directional antennas in at least one pair partially overlap.

2. The positioning antenna based on a single vertical plane symmetrical structure according to claim 1, characterized in that, All of the directional antennas are mounted on the same carrier.

3. The positioning antenna based on a single vertical plane symmetrical structure according to claim 1, characterized in that, This includes multiple pairs of directional antennas set together.

4. The positioning antenna based on a single vertical plane symmetrical structure according to claim 3, characterized in that, The effective horizontal coverage areas of the two directional antennas in each pair of positioning antennas partially overlap.

5. The positioning antenna based on a single vertical plane symmetrical structure according to claim 1, characterized in that, The horizontal angle between a pair of directional antennas whose effective coverage area on the horizontal plane partially overlaps is within ±10° of the horizontal beamwidth.

6. The positioning antenna based on a single vertical plane symmetrical structure according to claim 1, characterized in that, It consists of multiple pairs of directional antennas set on the same horizontal plane.

7. The positioning antenna based on a single vertical plane symmetrical structure according to claim 1, characterized in that, It consists of multiple pairs of directional antennas set on different horizontal planes.

8. The positioning antenna based on a single vertical plane symmetrical structure according to claim 7, characterized in that, A pair of directional antennas is set on each horizontal plane, and each pair of directional antennas overlaps in the vertical direction.

9. The positioning antenna based on a single vertical plane symmetrical structure according to claim 6 or 7, characterized in that, It also includes an omnidirectional antenna, which is located at the structural center of the positioning antenna.

10. The positioning antenna based on a single vertical plane symmetrical structure according to claim 1, characterized in that, The horizontal angle between a pair of directional antennas whose effective coverage area on the horizontal plane partially overlaps is equal to or substantially equal to the horizontal beamwidth of the directional antenna.

Images