System and method for foil detection using millimeter waves for retail applications

Abstract

In an aspect, the present disclosure includes a system for retail applications to detect metal foil using millimeter wave (mmWave). The system includes one or more pedestals positioned to define an exit to an exit point, one or more security tag readers fixedly positioned with the one or more pedestals configured to read data from a security tag passing through the exit, and one or more mmWave receivers fixedly positioned near the exit point configured to receive one or more reflected mmWave beams from a metal foil, wherein detection of the metal foil generates an alert message.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of U.S. Patent Application No. 17 / 162,689, filed January 29, 2021, entitled “System and Method for Foil Detection using Millimeter Wave for Retail Applications,” which claims priority to and the benefit of U.S. Provisional Application No. 62 / 968,971, filed January 31, 2020, entitled “System and Method for Foil Detection using Millimeter Wave for Retail Applications,” the contents of which are incorporated by reference in their entirety. TECHNICAL FIELD

[0003] The present disclosure relates to retail applications, and more specifically to metal foil detection using millimeter wave (mmWave) for retail applications. BACKGROUND

[0004] Radio frequency identification (RFID) systems and / or electronic article surveillance (“EAS”) systems are commonly used in retail stores and other locations to prevent the unauthorized removal of merchandise from a protected area. Typically, a detection system is configured at the exit of the protected area, which contains one or more transmitters and antennas (“pedestals”) capable of generating an electromagnetic field at the exit, known as an “interrogation zone.” Items to be protected are tagged with security tags, such as EAS tags (or markers) and / or RFID tags, which generate a response signal when activated as the tag passes through the interrogation zone. Antennas and receivers in the same or another “pedestal” detect the response signal and can generate an alarm if the security tag is not accounted for.

[0005] Acousto-Magnetic (AM) systems are commonly used for EAS tag detection and are well known in the art. Detectors in AM systems transmit periodic bursts of 58 kHz, which induces a detectable resonant response in EAS tags. Similarly, detectors in RFID systems transmit periodic bursts in the radio frequency range, which induces a detectable resonant response in RFID tags. "Dual-technology" tags include EAS tags and RFID tags in an integrated tag or an integrated tag with EAS tag capabilities and RFID tag capabilities. Detectors in dual-technology systems transmit periodic bursts of 58 kHz and transmit periodic bursts in the radio frequency range, which induces a detectable resonant response of dual-technology tags.

[0006] Retailers, such as clothing retailers, have deployed security tags in stores to track product movement as the products arrive at the store, are to be displayed on the sales floor, and are sold. The security tags can be used with a security system to detect inventory changes and / or possible loss events. For example, the security tags can be read by an exit system to determine if a tagged item is leaving the retail premises. The security tags can be read from up to several feet away and do not need to be in direct line of sight of the reader to be tracked.

[0007] To avoid detection of the security tags, a metal foil or metal foil bag (also referred to as a "boost bag") can be used to shield detection of one or more security tags. For example, a thief can place merchandise in a boost bag and walk through an exit / pedestal and the security tag is not detected because the accelerated bag shields the signal emitted by the security tag from the pedestal. In other words, the boost bag shields the AM and / or RFID frequencies from being detected by the pedestal.

[0008] Accordingly, there is a need in the art to detect boost bags that can contain stolen merchandise from a store. SUMMARY

[0009] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0010] Example implementations include a system for retail applications using millimeter wave (mmWave) to detect metal foil. The system includes one or more pedestals positioned to define an exit to an exit point, one or more security tag readers fixedly positioned with the one or more pedestals configured to read data from a security tag passing through the exit, and one or more mmWave receivers fixedly positioned near the exit point configured to receive one or more reflected mmWave beams from a metal foil, wherein detection of the metal foil generates an alert message.

[0011] In another example, a method for retail applications using millimeter wave (mmWave) to detect metal foil is disclosed. In yet another aspect, a non-transitory computer readable medium comprising code executable by one or more processors for using millimeter wave (mmWave) to detect metal foil in a retail application is disclosed.

[0012] To the accomplishment of the foregoing and related ends, one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects can be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic illustration of an example retail location including a first example of a security system.

[0014] Figure 2 is a schematic block diagram of an example computer device according to implementations of the disclosure.

[0015] Figure 3 is a flowchart of a method for detecting foil according to implementations of the disclosure. DETAILED DESCRIPTION

[0016] The present disclosure provides systems and methods for detecting metal foil bags. By incorporating millimeter wave technology into a base or overhead detection system, the base or overhead detection system is able to detect metal foil bags. For example, the base or overhead detection system can emit one or more millimeter wave beams and receive one or more reflected millimeter wave beams from the metal foil or metal foil bag. The one or more reflected beams can trigger an alarm. For example, the system can cause an alarm message to be sent to a device associated with a store personnel such as a security guard. Thus, if a security tagged item is placed in a pressurized bag, the millimeter wave technology is able to detect the pressurized bag and trigger an alarm. The alarm can be audible and / or an alarm message such as an email, a text message, and any other alarm message received by a device such as a computing device and / or a mobile device. For example, the security guard can receive the alarm and investigate the situation and find the stolen item in the pressurized bag.

[0017] Reference is now made to Figure 1 The example retail location 100 includes multiple areas in which tagged products can be located. For example, the retail location 100 can include an open display area 110, a front end 112, an aisle 114, and a security room 118. Customers 130 can be located in different areas or zones within and / or outside the store. Workers 132 can be located at locations such as checkout registers and the security room 118. Those skilled in the art will appreciate that the disclosed systems and methods are applicable to a variety of retail locations, and the present disclosure is not limited to the example retail location or areas.

[0018] As noted above, retailers, such as clothing retailers, have deployed security systems, such as EAS and / or RFID systems, in the store that use security tags to track product movement, for example, as the product arrives at the store, is displayed on the sales floor, and / or is sold. By employing security tags, retailers are able to reduce the amount of time store employees spend counting inventory (e.g., manually counting inventory on the floor and in the stockroom), as well as increase merchandise visibility within each store, enabling shoppers in the store and online to find what they are looking for. The security system can use different frequency signals to read and capture information stored on tags attached to objects, such as goods, products, or merchandise. For example, the security tags can be used with the security system to detect inventory changes and / or possible loss events. For example, one or more security tags can be read by an exit system to determine whether the tagged item 122 is leaving the retail location. The security tags (e.g., tags 124) can be read from as far as several feet away and do not need to be in direct line of sight of the reader to be tracked.

[0019] The security system can include one or more security tags or labels 124 (e.g., EAS tags, RFID tags, or dual technology tags) and readers (e.g., exit system 140). Each security tag is embedded with at least one transmitter and at least one receiver, such as an EAS transmitter and an EAS receiver, an RFID transmitter and an RFID receiver, or both. Each security tag can further contain a specific serial number (e.g., an Electronic Product Code (EPC)) for each particular object. For example, in one embodiment, a security tag can include multiple memory banks, such as a reserved memory, an EPC memory, a tag identification (TID) memory, and a user memory. The reserved memory bank can include an access password and a deactivation password. The EPC memory can include an EPC, a protocol control, and a cyclic redundancy check value. The TID memory can include a tag identification. The user memory can store custom data.

[0020] To read the information encoded on the security tag 124, a bidirectional radio transmitter-receiver, known as an interrogator or reader (e.g., exit system 140), uses one or more antennas, antenna panels, or antenna arrays (e.g., internal antennas) to transmit a signal to the security tag. The reader 140 can apply filtering to indicate what memory bank the security tag 124 should use to respond to the transmitted signal. The security tag 124 can respond with the information written in the memory bank (e.g., an EPC value or serial number). A security tag data set can include any information stored on the security tag 124 as well as information about reading the security tag 124. For example, the security tag data set can include a timestamp, a location, a signal transmission power, a received signal strength indication (RSSI), and an identifier of the reader 140. The security tag 124 can be a passive tag or a battery-powered security tag. A passive security tag can use the wave energy of the interrogator or receiver 140 to relay the stored information back to the interrogator. Conversely, a battery-powered security tag 124 can be embedded with a battery to power the relaying of information.

[0021] The security system 102 can include an exit system 140, a plurality of cameras 120, and an evaluation computer 126. The exit system 140 can include a plurality of sensors 142 located proximate to an exit 144. The plurality of sensors 142 can define an exit or exit point. For example, the example retail establishment 100 can include three relatively narrow exits 144. Sensors 142 can be located on each side of the exit 144. For example, in an embodiment, the sensors 142 can include at least one security tag reader including an antenna that generates a tag detection field 146. Each security tag reader can be fixedly positioned with the sensor 142 or base. For example, each security tag reader can be positioned or fastened to the sensor 142 or base. Generally, the sensors 142 can be configured (e.g., by setting a power level) such that the tag detection field 146 covers the exit 144 to detect tags moving through the exit. While the sensors 142 are shown as bases adjacent to the exit 144, the sensors 142 can be located on the floor and / or ceiling. As explained in more detail below, the sensors 142 can include millimeter wave technology to detect metal foils.

[0022] The cameras 120 can be located in or proximate to the exit system 140, or can be located in other areas of the retail establishment 100. Each camera 120 can be a digital video camera such as a security camera. The plurality of cameras 120 can be located throughout the retail establishment 100. Each camera 120 can provide a constant video feed of one or more areas of the retail establishment 100. The cameras 120 can generally be oriented in a default direction to capture a particular view of the retail establishment 100 of desired activity, but one or more cameras 120 can be mounted on a gimbal that allows for rotation and panning of the respective camera 120. For example, the security system 102 can move the cameras 120 to keep the field of view of the cameras 120 on the customer 130. In another aspect, the security system 102 can allow for manual control of one or more cameras 120. In an aspect, the security system 102 can be integrated with one or more other systems, and the video feeds of the cameras 120 can be used for multiple purposes.

[0023] The evaluation computer 126 can be a computer device programmed to evaluate at least the exit system measurements from the sensors 142. The evaluation computer 126 can be, for example, any mobile or fixed computer device, including but not limited to a computer server, a desktop or laptop or tablet computer, a cellular telephone, a personal digital assistant (PDA), a handheld device, any other computer device having wired and / or wireless connectivity capability with one or more other devices, or any other type of computerized device capable of processing exit system measurements.

[0024] The outlet system 140 can include millimeter wave sensors 142 or millimeter wave technology. For example, the millimeter wave sensors 142 or millimeter wave technology can include a millimeter wave transmitter, a millimeter wave receiver, and one or more antennas, antenna panels, or antenna arrays. Each millimeter wave sensor 142 can be fixedly positioned with the base. For example, the millimeter wave sensors 142 can be positioned or fastened to the base. The millimeter wave transmitter can transmit one or more incident millimeter wave beams (e.g., at about 60 GHz) through the one or more antennas, and receive one or more reflected millimeter wave beams through the one or more antennas. The one or more millimeter wave beams can reflect off the booster bag. The one or more reflected millimeter wave beams can be compared to a threshold to determine whether the booster bag is detected. For example, a received signal strength of the one or more reflected millimeter wave beams is compared to a threshold to determine whether the booster bag is detected. The comparison can be done at the base (e.g., by a processor or a combination of hardware and software) and / or can be done by a processor of the evaluation computer 126. For example, a transceiver of the base can communicate the one or more reflected millimeter wave beams to the evaluation computer 126 over a wired or wireless communication link for processing.

[0025] In one embodiment, the millimeter wave sensors 142 can compare an amplitude, a phase, a frequency, and / or a frequency shift of the one or more incident millimeter wave beams and the one or more reflected millimeter wave beams. The millimeter wave sensors 142, which can include a millimeter wave transmitter and / or receiver, can determine the presence of the metal foil based on a difference / variation in the amplitude, the phase, the frequency, and / or the frequency shift of the one or more incident millimeter wave beams and / or the one or more reflected millimeter wave beams. For example, the millimeter wave sensors 142 can evaluate a received signal strength of a received signal strength of the one or more reflected millimeter wave beams to determine the presence of the metal foil. The millimeter wave sensors 142 can determine the presence of the metal foil if the received signal strength is greater than, for example, a threshold strength value. The millimeter wave sensors 142 can determine the absence of the metal foil if the received signal strength is less than, for example, a threshold strength value.

[0026] In one or more embodiments, the camera 120 can include millimeter wave sensors 142 and perform similar functions as described above. In one or more embodiments, the sensor system, the top system, or the antenna system can include millimeter wave sensors 142, such as a millimeter wave transmitter, a millimeter wave receiver, and one or more antennas, and perform similar functions as described above. The sensor system, the top system, or the antenna system can be installed in the store in a similar manner as the camera 120.

[0027] Millimeter wave technology or millimeter wave sensors 142 can be used for read people counting, backfield control, and / or RFID filtering. For people counting, millimeter wave technology can be used to count how many people enter and exit a store and / or how many people enter or exit a zone or area within a store. For example, a millimeter wave transmitter can transmit one or more millimeter wave beams and a millimeter wave receiver can receive one or more reflected millimeter wave beams. The one or more reflected millimeter wave beams can be compared to a threshold (e.g., received signal strength) and a threshold to determine whether a person is entering or exiting an area or store.

[0028] Backfield control allows a store to place merchandise closer to sensors. For example, a base or overhead detection system (or antenna system) can detect one or more security tags and millimeter wave technology can be used to identify whether the one or more security tags are associated with a person (e.g., moving) or remain stationary. If the millimeter wave technology detects that the one or more security tags are fixed, no alarm message is generated. However, if the millimeter wave technology detects that the one or more security tags are moving, another determination can be used to determine whether the one or more security tags are within an alarm zone to trigger an alarm message. For example, the evaluation computer 126 can receive information from the base or overhead detection system and determine whether the one or more security tags are moving toward an exit or alarm zone (e.g., within a predetermined threshold of the exit) and trigger an alarm message.

[0029] Read RFID filtering has allowed stores to determine whether a read of an RFID tag is an unintended signal. Due to the nature of radio frequencies, a resonant response from an RFID tag can be triggered by an RFID pulse string reflected from one or more objects or the resonant response is reflected from one or more objects and can result in a false read. For example, a radio frequency signal can be reflected from a person or another object. By using millimeter wave technology as described above with respect to backfield control, an unintended resonant response can be determined to be an unintended signal.

[0030] Referring now to Figure 2 , an example computer device 240 in accordance with embodiments is shown, including additional component details as compared to Figure 1 . The computer device 240 can be an example of the evaluation computer 126 of Figure 1 In one example, the computer device 240 can include a processor 48 for carrying out processing functions associated with one or more components and functions described herein. The processor 48 can include a single or multiple set of processors or multi-core processors. Further, the processor 48 can be implemented as an integrated processing system and / or a distributed processing system. In embodiments, the processor 48 can include, for example, a CPU 242.

[0031] In an example, the computer device 240 can include memory 50 storing instructions executable by the processor 48 for performing the functions described herein. In embodiments, for example, the memory 50 can include memory 244. The memory 50 can include instructions for executing a metal foil detection application 260 to perform the methods.

[0032] Further, the computer device 240 can include a communication component 52 for establishing and maintaining communications with one or more parties utilizing hardware, software, and services as described herein. The communication component 52 can communicate with components of the computer device 240 as well as with external devices including devices located across a communications network and / or devices serially or

[0033] Additionally, the computer device 240 can include a data store 54, which can be any suitable combination of hardware and / or software, that provides for the mass storage of information, databases, and programs employed in connection with embodiments described herein. For example, the data store 54 can be a data repository for the operating system 252 and / or the metal foil detection application 260. The data store can include the memory 244 and / or the storage device 246.

[0034] The computer device 240 can also include a user interface component 56 operable to receive inputs from a user of the computer device 240 and further operable to generate outputs for presentation to the user. The user interface component 56 can include one or more input devices, including but not limited to a keyboard, a number pad, a mouse, a touch-sensitive display, a digitizer, a navigation key, a function key, a microphone, a voice recognition component, any other mechanism capable of receiving an input from a user, or any combination thereof. Further, the user interface component 56 can include one or more output devices, including but not limited to a display, a speaker, a haptic feedback mechanism, a printer, any other mechanism capable of presenting an output to a user, or any combination thereof.

[0035] In embodiments, the user interface component 56 can transmit and / or receive messages corresponding to the operation of the operating system 252 and / or the metal foil detection application 260. Further, the processor 48 can execute and the memory 50 or the data store 54 can store the operating system 252 and / or the metal foil detection application 260.

[0036] Turning to Figure 3The method 300 of detecting a metal foil can be performed by the evaluation computer 126, the millimeter wave sensor 142, and / or the computing device 240.

[0037] At block 305, the method 300 can emit one or more incident millimeter wave beams toward the metal foil. For example, the evaluation computer 126, the millimeter wave sensor 142, the one or more millimeter wave emitters, and / or the computing device 240 can emit one or more incident millimeter wave beams toward the metal foil.

[0038] At block 310, the method 300 can receive one or more reflected millimeter wave beams. For example, the evaluation computer 126, the millimeter wave sensor 142, the one or more millimeter wave emitters, and / or the computing device 240 can receive one or more reflected millimeter wave beams.

[0039] At block 315, the method 300 can detect the metal foil based on the one or more reflected millimeter wave beams. For example, the evaluation computer 126, the millimeter wave sensor 142, and / or the computing device 240 can detect the metal foil based on the one or more reflected millimeter wave beams as described above. In one embodiment, the millimeter wave sensor 142 can compare the amplitude, phase, frequency, and / or frequency shift of the one or more incident millimeter wave beams to the amplitude, phase, frequency, and / or frequency shift of the one or more reflected millimeter wave beams. The millimeter wave sensor 142, which can include a millimeter wave emitter and / or receiver, can determine the presence of the metal foil based on the difference / variation in the amplitude, phase, frequency, and / or frequency shift of the one or more incident millimeter wave beams and / or the one or more reflected millimeter wave beams. For example, the millimeter wave sensor 142 can evaluate the received signal strength of the received signal strength of the one or more reflected millimeter wave beams to determine the presence of the metal foil. If the received signal strength is, for example, greater than a threshold strength value, the millimeter wave sensor 142 can determine the presence of the metal foil. If the received signal strength is, for example, less than a threshold strength value, the millimeter wave sensor 142 can determine the absence of the metal foil.

[0040] At block 320, the method 300 can generate an alert in response to detecting the metal foil. For example, the evaluation computer 126, the millimeter wave sensor 142, and / or the computing device 240 can generate an alert in response to detecting the metal foil.

[0041] As used in this application, the terms "component," "system" and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component can be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and / or a computer. By way of illustration, both an application running on a computer device and the computer device can be a component. One or more components can reside within a process and / or thread of execution and a component can be localized, both within a single computer and / or distributed across

[0042] In addition, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless specified otherwise, or clear from context, the phrase "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, the phrase "X employs A or B" is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form.

[0043] Various embodiments or features can take forms other than the embodiments described and / or pictured herein. As will be apparent to those of ordinary skill in the art, various systems can include additional components, steps, or functions, and / or can not include all of the components, steps, or functions illustrated in the figures. Embodiments of the disclosure can include combinations of elements and features. It will be apparent to those of ordinary skill in the art that various implementations of the systems can not include all of the functions described herein, or can include a different arrangement of functions.

[0044] The various illustrative logics, logical blocks, and actions described in connection with the embodiments disclosed herein can be implemented or performed with a specially-programmed one of a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computer devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Additionally, at least one processor can include one or more components operable to perform one or more of the steps and / or actions described above.

[0045] Furthermore, the steps and / or actions of a method or process described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium can be coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. Further, in some embodiments, the processor and the storage medium can reside in an ASIC. Additionally, the ASIC can reside in a user terminal. In the alternative, the processor and the storage medium can reside as discrete components in a user terminal. Moreover, in some embodiments, the steps and / or actions of a method or process can reside as one or any combination or set of codes and / or instructions on a machine readable medium and / or computer readable medium, which can be incorporated in a computer program product.

[0046] In one or more embodiments, the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. Storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, include compact discs (CD), laser discs, optical discs, digital versatile discs (DVD), floppy disks and Blu-ray discs where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0047] While embodiments of the disclosure have been described in connection with examples of the disclosure, as will be understood by one of ordinary skill in the art, the disclosure is not limited to the embodiments disclosed but rather can be modified and implemented in various ways without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification or from practice of the examples disclosed herein.

Claims

1. A system for detecting metal foil using millimeter wave (mmWave) for retail applications, the system comprising: one or more bases positioned to define an exit to an exit point; one or more security tag readers fixedly positioned with the one or more bases and configured to read data from a security tag proximate the exit; as well as One or more millimeter wave receivers, the one or more millimeter wave receivers being fixedly positioned near the exit point and configured to receive one or more reflected millimeter wave beams from the metal foil, wherein the one or more millimeter wave receivers are further configured to detect the metal foil based on a receiver amplitude of the one or more reflected millimeter wave beams without requiring a receiver phase of the one or more reflected millimeter wave beams, wherein detection of the metal foil generates an alarm message. 2 . The system of claim 1 , further comprising one or more millimeter wave transmitters configured to transmit one or more incident millimeter wave beams toward the metal foil. 3 . The system of claim 2 , wherein the one or more millimeter wave receivers are further configured to compare the one or more incident millimeter wave beams and the one or more reflected millimeter wave beams.

4. The system of claim 3, wherein comparing comprises comparing at least one of a transmitter frequency or a transmitter frequency shift of the one or more incident millimeter-wave beams with at least one of a receiver frequency or a receiver frequency shift of the one or more reflected millimeter-wave beams.

5. The system of claim 1 , wherein the one or more millimeter wave receivers are further configured to detect the metal foil based on received signal strength of the one or more reflected millimeter wave beams, and / or wherein the one or more millimeter wave receivers are further configured to count the number of people approaching the exit.

6. The system of claim 5, wherein detecting the metal foil comprises: comparing the received signal strength with a threshold; as well as The alert message is generated in response to the received signal strength being greater than the threshold.

7. A method for detecting metal foil, the method comprising: transmitting one or more incident millimeter-wave beams toward the metal foil; receiving one or more reflected millimeter-wave beams; detecting the metal foil based on a receiver amplitude of the one or more reflected millimeter-wave beams without requiring a receiver phase of the one or more reflected millimeter-wave beams; as well as An alarm is generated in response to detecting the metal foil. 8 . The method of claim 7 , wherein detecting the metal foil further comprises comparing the one or more incident millimeter-wave beams and the one or more reflected millimeter-wave beams.

9. The method of claim 8, wherein comparing further comprises comparing at least one of a transmitter frequency or a transmitter frequency shift of the one or more incident millimeter-wave beams with at least one of a receiver frequency or a receiver frequency shift of the one or more reflected millimeter-wave beams.

10. The method of claim 7, wherein detecting the metal foil comprises detecting the metal foil based on a received signal strength of the one or more reflected millimeter wave beams.

11. The method of claim 10, wherein detecting the metal foil further comprises comparing the received signal strength to a threshold.

12. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors, cause the one or more processors to: cause one or more millimeter wave transmitters to emit one or more incident millimeter wave beams toward a metal foil; cause one or more millimeter wave receivers to receive one or more reflected millimeter wave beams; detect the metal foil based on a receiver amplitude of the one or more reflected millimeter wave beams without a receiver phase of the one or more reflected millimeter wave beams; and generate an alert in response to detecting the metal foil.

13. The non-transitory computer-readable medium of claim 12, wherein the instructions to detect the metal foil further comprise instructions to compare the one or more incident millimeter wave beams and the one or more reflected millimeter wave beams.

14. The non-transitory computer-readable medium of claim 13, wherein the instructions to compare further comprise instructions to compare at least one of a transmitter frequency or a transmitter frequency shift of the one or more incident millimeter wave beams to at least one of a receiver frequency or a receiver frequency shift of the one or more reflected millimeter wave beams.

15. The non-transitory computer-readable medium of claim 12, wherein the instructions to detect the metal foil comprise instructions to detect the metal foil based on a received signal strength of the one or more reflected millimeter wave beams.

16. The non-transitory computer-readable medium of claim 15, wherein the instructions to detect the metal foil further comprise instructions to compare the received signal strength to a threshold.

Images