Method and apparatus for backscatter-based communication in a wireless communication system

Abstract

A communication device includes an interrogator configured to output an interrogation signal comprising a continuous unit chirp signal varying from a first frequency to a second frequency, and a backscatter tag configured to receive the interrogation signal and frequency modulate the interrogation signal to generate and provide a tag signal, wherein the interrogator is further configured to receive the tag signal and demodulate the tag signal.

Description

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2021-0171342 filed on December 2, 2021, Korean Patent Application No. 10-2022-0066606 filed on May 31, 2022, and Korean Patent Application No. 10-2022-0162049 filed on November 28, 2022, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure relates to a method and apparatus for communication based on backscattering in a wireless communication system, and more specifically, to a method and apparatus for communication using an interrogation signal that repeats a unit chirp signal by frequency modulation through backscattering. Background Technology

[0004] With the number of Internet of Things (IoT) devices targeting massive machine-type communication (mMTC) expected to increase to one trillion by 2035, massive connectivity has long been considered key to the success of IoT and various future services.

[0005] Backscattering is an attractive option for large-scale networks, while low-power operation provides long-term sustainability. Furthermore, the abundant spectrum resources of millimeter wave (mmWave) covering up to 14 GHz bandwidth in the 60-GHz band of sixth-generation (6G) networks hold great potential for large-scale networks. Summary of the Invention

[0006] Using millimeter-wave backscattering networks presents several challenges. One such challenge is that the power of the backscattered signal is lower than the power of clutter noise caused by environmental reflections in the millimeter-wave spectrum, making it prone to errors. This, along with the attenuation of the backscattered signal, has a greater impact in rooms where signals are frequently reflected.

[0007] Another challenge is that, for low-cost circuitry and ultra-low-power operation, backscattering devices cannot access wide-bandwidth millimeter waves in the range of several GHz, and cannot share channels for simultaneous communication, thus limiting scalability.

[0008] The embodiments are intended to address these difficulties in the prior art. Specifically, one object of this embodiment is to provide a communication method using backscattering.

[0009] The technical objects of these embodiments are not limited to the technical objects described above, and other technical objects can be inferred from the following embodiments.

[0010] Other aspects will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments described in this disclosure.

[0011] According to one aspect of this disclosure, a communication device includes an interrogator and a backscattering tag, the interrogator being configured to output an interrogation signal comprising a continuous unit chirp signal varying from a first frequency to a second frequency, the backscattering tag being configured to receive the interrogation signal and frequency modulate the interrogation signal to generate and provide a tag signal, wherein the interrogator is further configured to receive the tag signal and demodulate the tag signal.

[0012] According to another aspect of this disclosure, the interrogator includes an interrogation signal providing unit and a demodulation unit. The interrogation signal providing unit is configured to output an interrogation signal including a continuous unit chirp signal changing from a first frequency to a second frequency. The demodulation unit is configured to receive and demodulate a tag signal generated by frequency modulation of the interrogation signal, wherein the interrogation signal is a periodic signal including a continuous unit chirp signal having a continuous phase. Attached Figure Description

[0013] Other aspects, features, and advantages of the above and certain embodiments of this disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, wherein:

[0014] Figure 1 This is a conceptual diagram illustrating a wireless communication system according to an embodiment;

[0015] Figure 2 This is a block diagram of an interrogator according to an embodiment;

[0016] Figure 3A It is a graph used to describe the change of frequency of the interrogation signal provided by the interrogator over time;

[0017] Figure 3B This is a graph showing the change in the amplitude of the interrogation signal over time;

[0018] Figure 4 This is a block diagram of a backscattering tag according to an embodiment;

[0019] Figure 5 This is a diagram illustrating the unit chirp signal contained in the interrogation signal separated by the signal separator according to an embodiment and the tag signal received by the interrogator;

[0020] Figure 6 This is a diagram illustrating the decoding characteristics of an interrogation signal consisting of a single chirp signal and an interrogation signal consisting of repetitions of chirp signals, according to an embodiment.

[0021] Figure 7AThis is a diagram showing the noise bin where clutter noise is located and the tag bin where the tag signal is located in the frequency domain;

[0022] Figure 7B This is a diagram showing the signals reflected by two backscattering markers at different distances from the interrogator in the discrete frequency domain;

[0023] Figure 8 This is a diagram showing the channel allocation based on the distance between the interrogator and each backscatter tag;

[0024] Figure 9A This is a diagram showing a prototype of a backscattering tag housed in an aluminum casing;

[0025] Figure 9B This is a diagram showing the substrate of the backscattering tag;

[0026] Figure 9C This is a graph showing the reflection coefficient (S11) of a substrate with a backscattering tag having a closed switch;

[0027] Figure 10A This is a diagram showing a prototype of a backscattering tag implemented using a Van Atta array;

[0028] Figure 10B This is a diagram showing the results of measuring the beam pattern of a tag prototype with normalized power;

[0029] Figure 10C This is a diagram illustrating a prototype backscatter tag implemented in the 60 GHz Industrial, Scientific and Medical (ISM) band;

[0030] Figure 11A This is a diagram showing a reader implemented using the EVAL-Tinyrad commercial radar;

[0031] Figure 11B This is a diagram showing the beam characteristics of an omnidirectional antenna for a TX antenna;

[0032] Figure 12 This is a diagram showing backscattering tags arranged in different positions;

[0033] Figure 13 It is used to describe based on Figure 12 A graph showing the communication performance of backscattering tags arranged in a central pattern;

[0034] Figure 14 This is a diagram illustrating the communication performance according to an embodiment, in a state where the interrogator and backscatter tag constituting the communication device are partially blocked.

[0035] Figure 15AIt is a diagram used to describe a scenario where there are various obstacles between the interrogator and the backscatter tag;

[0036] Figure 15B This is a graph showing the signal-to-noise ratio (SNR) measured when obstacles are present;

[0037] Figure 15C This is a graph showing the bit error rate (BER) measured when obstacles are present;

[0038] Figure 16A It is a photograph showing an auditorium measuring 20m x 20m that was used for large-scale communication experiments;

[0039] Figure 16B This is a diagram showing a scene with backscattered labels arranged in a specific pattern;

[0040] Figure 17 This is a graph used to describe the signals of the multiple backscattered tags and the BER performance of the multiple backscattered tags;

[0041] Figure 18A This is a diagram showing the path of the backscattered tag horizontally away from the interrogator;

[0042] Figure 18B This is a diagram showing the channel when the backscattered tag is horizontally away from the interrogator;

[0043] Figure 18C This is a graph used to describe the BER when the backscattered tag is horizontally away from the interrogator;

[0044] Figure 19A This is a diagram showing the path of the backscattering tag perpendicularly away from the interrogator; and

[0045] Figure 19B This is a graph used to describe the BER when the backscattered tag is perpendicular to the interrogator. Detailed Implementation

[0046] Reference will now be made in detail to embodiments, examples of which are shown in the accompanying drawings, wherein similar reference numerals always refer to similar elements. In this respect, the embodiments may take different forms and should not be construed as limited to the description herein. Therefore, these embodiments are described below solely by reference to the figures to explain various aspects of this specification. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. As expressed as “at least one,” when preceding the list of elements, the entire list of elements is modified without modifying any individual element in the list.

[0047] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, enabling those skilled in the art to perform the disclosure without difficulty. However, this disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments described herein. Furthermore, for clarity of description, portions irrelevant to the description have been omitted, and similar reference numerals have been assigned to similar elements throughout this specification.

[0048] Although the terms used in this disclosure are chosen from commonly used terms in view of their function in this disclosure, the terms may differ depending on the intent of a person skilled in the art, a precedent, or the emergence of a new technology. Furthermore, in certain cases, these terms were carefully chosen by the applicant of this disclosure, in which case the meaning of these terms will be described in detail in the corresponding embodiments. Therefore, the terms used herein are not merely names of these terms, but are defined based on their meaning throughout the terminology and content of this disclosure.

[0049] A singular expression may also include a plural meaning, provided it is not inconsistent with the context. Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains, based on an understanding of this disclosure. Terms as defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and the disclosure, and shall not be interpreted as having an idealized or overly formal meaning, unless expressly defined herein.

[0050] Throughout this disclosure, when a component "includes" an element, it should be understood that the component may additionally include other elements, rather than exclude other elements, unless specifically stated otherwise. Furthermore, as used herein, terms such as "...device," "...unit," "...module," etc., indicate a unit that performs at least one function or operation, which may be implemented as hardware or software or a combination thereof.

[0051] Throughout this specification, when a component is referred to as "connecting" another component, it may be "directly connected" to the other component or "electrically connected" to the other component via an intermediate element.

[0052] As used here, the expression “configured as” can be used interchangeably with, for example, “suitable,” “capable of,” “designed to,” “adapted,” “as,” or “able to.” The expression “configured as” may not simply mean “specifically designed for” in a hardware manner. Rather, in some cases, the expression “system configured as” can indicate that the system is “capable” of working with other devices or components. For example, “processor configured (or set) to perform A, B, and C” might mean a dedicated processor (e.g., an embedded processor) for performing the respective operations, or a general-purpose processor (e.g., a central processing unit (CPU) or application processor) capable of performing the respective operations by executing one or more software programs stored in memory.

[0053] Here, it can be understood that each block in the process flowchart and its combination can be executed by computer program instructions. These computer program instructions can be loaded into the processor of a general-purpose computer, special-purpose computer, or other programmable data processing equipment, and thus, the instructions executed by the computer's processor or other programmable data processing equipment can generate means configured to perform the functions described in the flowchart(s) block(s). These computer program instructions can also be stored in a computer-usable or computer-readable storage device, capable of directing the computer or other programmable data processing equipment to perform functions in a specific mode; therefore, the instructions stored in the computer-usable or computer-readable storage device can also produce production items involving instruction means configured to perform the functions described in the flowchart(s) block(s). The computer program instructions can also be loaded into a computer or other programmable data processing equipment, and thus, a computer-executable process can be generated by performing a series of operational steps on the computer or other programmable data processing equipment, such that the instructions executing in the computer or other programmable data processing equipment provide steps for performing the functions described in the flowchart(s) block(s).

[0054] Furthermore, each block may indicate a portion of a module, segment, or code containing one or more executable instructions for performing a specific logical function(s). Additionally, in several alternative embodiments, the functions described in a block may be out of order. For example, two blocks displayed consecutively may actually execute substantially simultaneously, or the block may sometimes execute in reverse order according to its corresponding function.

[0055] Hereinafter, various embodiments will be described with reference to the accompanying drawings.

[0056] Figure 1 This is a conceptual diagram illustrating a wireless communication system 10 according to an embodiment.

[0057] Reference Figure 1The wireless communication system 10 according to the embodiment may include an interrogator 100 and at least one backscatter tag (e.g., backscatter tag 200).

[0058] The interrogator 100 can output an interrogation signal IS. The interrogator 100 can generate the interrogation signal IS by repeatedly transmitting a unit chirp signal that changes from a first frequency to a second frequency over a preset duration.

[0059] The backscatter tag 200 can receive an interrogation signal output from the interrogator 100. The backscatter tag 200 can generate a tag signal TS by frequency modulation of the received interrogation signal. For example, the backscatter tag 200 can provide the tag signal TS by modulating the frequency of the interrogation signal based on the frequency corresponding to the provided data. The backscatter tag 200 can receive data provided from an electronic device including the backscatter tag 200 or from another electronic device connected to the backscatter tag 200.

[0060] Interrogator 100 can receive tag signal TS from backscattered tag 200. Since the interrogation signal IS has a structure where a unit chirp signal repeats over a preset duration, the characteristics of the modulation frequency may differ from those of a signal consisting of a single chirp signal. Specifically, a tag signal obtained by frequency modulation of an interrogation signal consisting of a single chirp signal is added to a clutter noise signal, while a tag signal TS obtained by frequency modulation of the interrogation signal IS in which a repeating unit chirp signal is present can be obtained at a frequency that excludes clutter noise. In this way, the noise signal and the data signal are separated from each other, and therefore, interrogator 100 can achieve a high signal-to-noise ratio (SNR).

[0061] Figure 2 This is a block diagram of the interrogator 100 according to an embodiment.

[0062] Reference Figure 2 The interrogator 100 may include a signal generator 110 configured to generate an interrogation signal, a signal separator 115 configured to separate the signal generated by the signal generator 110, and a demodulation unit 120 configured to demodulate the received tag signal.

[0063] Signal generator 110 can generate an interrogation signal by repeating a chirp signal with a frequency changing from f1 to f2 N times over a unit time period T. Here, the interrogation signal s(t) can be determined based on the following equation 1.

[0064] [Equation 1]

[0065]

[0066] In Equation 1, c(t) represents the chirped signal, and for example, the frequency of the chirped signal can increase linearly from f1 to f2 during the period T. However, this is just an example, and the chirped signal is not limited to the example above. Furthermore, the values ​​of T, f1, f2, and N can be set according to the channel environment in which communication is carried out or the performance required in the wireless communication system.

[0067] The interrogation signal can be separated into first and second interrogation signals by the signal splitter 115, and the first interrogation signal can be transmitted to the backscatter tag 200 via the antenna.

[0068] The second portion of the interrogation signal separated by signal separator 115 can be sent to demodulation unit 120. Demodulation unit 120 may include mixer 122, low-pass filter (LPF) 124, and fast Fourier transform (FFT) unit 126. In mixer 122, the second portion of the interrogation signal separated by signal separator 115 may be mixed with the tag signal received by interrogator 100. The mixed signal may be sent to FFT unit 126 via LPF 124, and FFT unit 126 may perform a Fourier transform on the signal that has passed through LPF 124. The above components are merely examples, and interrogator 100 may not necessarily include all of the above components. According to another example, demodulation unit 120 may include filters other than LPF 124.

[0069] Furthermore, according to an embodiment not shown, the interrogator 100 may further include a power amplifier. The interrogation signal can be amplified by the power amplifier (not shown) and then transmitted via an antenna.

[0070] Furthermore, according to another embodiment, the interrogator 100 may include a transceiver, a processor, and a memory. According to various embodiments, the transceiver, processor, and memory of the interrogator 100 can operate according to the communication method of the interrogator 100. However, the components of the interrogator 100 are not limited to the examples described above. For example, the interrogator 100 may include more or fewer components than those described above. Furthermore, the processor, transceiver, and memory may be implemented as a single chip.

[0071] A transceiver, in general, refers to both the receiver and transmitter of the interrogator 100, and can transmit and receive signals to and from backscatter tags, base stations, or network entities. For this purpose, a transceiver may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of the transmitted signal, and an RF receiver for low-noise amplification and down-converting the frequency of the received signal. However, this is merely one example of a transceiver, and its components are not limited to RF transmitters and RF receivers.

[0072] Furthermore, the transceiver may include wired / wireless transceivers and may include various components for transmitting and receiving signals. Additionally, the transceiver can receive signals via a radio channel, output signals to a processor, and transmit signals output from the processor via a radio channel.

[0073] The memory can store programs and data necessary for the operation of the interrogator 100. Additionally, the memory can store control information or data contained in signals obtained by the interrogator 100. The memory can be a storage medium such as read-only memory (ROM), random access memory (RAM), hard disk, optical disc ROM (CD-ROM), or digital video disc (DVD), or a combination of storage media.

[0074] The processor can control a series of processes so that the interrogator 100 operates according to the above embodiments. The processor may include one or more processors. For example, the processor may include a communication processor (CP) for performing communication control and an application processor (AP) for controlling higher layers (such as applications).

[0075] Figure 3A It is a graph used to describe the frequency of the interrogation signal IS provided by the interrogator 100 over time.

[0076] Reference Figure 3A It can be seen that the query signal consists of repetitions of a chirped signal C whose frequency changes linearly within a unit time period. Figure 3A In the illustrated embodiment, the frequency of the unit chirped signal C increases linearly from a first frequency f1 to a second frequency f2. However, according to an embodiment not shown, the frequency of the unit chirped signal can increase non-linearly from the first frequency to the second frequency. Furthermore, according to an embodiment not shown, the frequency of the unit chirped signal C can decrease linearly from the first frequency f1 to the second frequency f2, and according to another embodiment, the frequency of the unit chirped signal C can decrease non-linearly from the first frequency to the second frequency.

[0077] The difference between the first frequency f1 and the second frequency f2 can correspond to the bandwidth of the frequency band to be used. In one embodiment, the first frequency f1 and the second frequency f2 can constitute a bandwidth of 250 MHz relative to the center frequency of the 24-GHz band in the millimeter-wave band of tens to hundreds of GHz. In another embodiment, the first frequency f1 and the second frequency f2 can constitute a bandwidth of 14 GHz relative to the center frequency of 60 GHz in the millimeter-wave band.

[0078] Figure 3B This is a graph showing the change in the amplitude of the interrogation signal IS over time. For example... Figure 3B As shown, the unit chirped signals C that constitute the interrogation signal IS can be interconnected to make the phase continuous.

[0079] As described below, the number of unit chirp signals C constituting the interrogation signal IS, the change in the frequency of the unit chirp signal C over time, and the duration of the unit chirp signal C can be controlled according to the communication environment.

[0080] Figure 4 This is a block diagram of a backscattering tag 200 according to an embodiment.

[0081] Reference Figure 4 The backscattering tag 200 may include an antenna 210 configured to receive an interrogation signal IS and output a tag signal TS, and a modulation unit 220 configured to frequency modulate the received interrogation signal IS. In an embodiment, the interrogation signal IS can be received via the antenna 210, and the tag signal TS, generated by modulating the frequency of the interrogation signal IS with data provided to the backscattering tag 200, can be transmitted. In an embodiment, the antenna 210 may be implemented as any type of antenna, such as a VanAtta array, a phased array antenna, or a waveguide antenna.

[0082] The modulation unit 220 can adjust the impedance of the antenna by impedance switching to modulate the interrogation signal IS to the desired frequency, thereby generating the tag signal TS. For example, the backscatter tag 200 can generate the tag signal TS by modulating the interrogation signal IS at frequency fn through impedance switching.

[0083] In one embodiment, the backscatter tag 200 may be included in an Internet of Things (IoT) device (not shown), and the interrogation signal IS may be frequency-modulated using data DATA collected by the IoT device and then provided to the interrogator 100. The IoT device (not shown) may include an energy harvesting device, and the backscatter tag 200 may be driven by the power harvested by the energy harvesting device.

[0084] Figure 5 This is a diagram illustrating the unit chirp signal C contained in the interrogation signal IS separated by the signal separator according to an embodiment and the tag signal TS received by the interrogator 100.

[0085] The tag signal TS received by the interrogator 100 is provided by the backscattered tag 200 that reflects the interrogation signal IS.

[0086] The received tag signal TS and the interrogation signal IS separated by the signal separator can be provided to mixer 122, and the two signals are mixed to generate an intermediate signal IF. The intermediate signal IF is generated by multiplying the tag signal TS by the interrogation signal IS, and can be separated into a signal having a frequency component corresponding to the sum of the frequencies of the two signals and a signal having a frequency component corresponding to the difference between the frequencies of the two signals.

[0087] Signals having a frequency component corresponding to the sum of the frequencies of the tag signal TS and the interrogation signal IS can be filtered out by the LPF 124. Conversely, signals having a frequency component corresponding to the difference between the frequencies of the tag signal TS and the interrogation signal IS can be provided to the FFT unit 126. In an embodiment, the FFT unit 126 can perform a discrete fast Fourier transform on the input signal.

[0088] Between the interrogation signal IS and the tag signal TS, there exists a time difference Δt corresponding to the distance traveled by the interrogation signal IS and the distance traveled by the tag signal TS. As the time difference Δt increases, the frequency difference Δf between the two signals increases. That is, it can be seen that the frequency of the tag signal TS received and modulated by the interrogator 100 includes not only the frequency component modulated by the backscattering tag 200, but also the frequency component corresponding to the distance between the interrogator 100 and the backscattering tag 200.

[0089] In this embodiment, the channel can be allocated to the tag based on the distance between the backscattering tag 200 and the interrogator 100 without individual modification. Therefore, frequency division multiple access can be performed without adjustment across the entire millimeter-wave bandwidth, without incurring overhead in the backscattering tag 200 and the interrogator 100.

[0090] Figure 6 This is a diagram illustrating the decoding characteristics of an interrogation signal consisting of a single chirped signal and an interrogation signal consisting of repetitions of chirped signals according to an embodiment.

[0091] Figure 6 A tag signal 615 generated from an interrogation signal 610 consisting of a single chirp signal is shown, as well as a tag signal 625 generated from an interrogation signal 620 consisting of multiple chirp signals.

[0092] Due to the characteristics of the Fourier transform of a periodic signal containing both signal and noise components, the result of the Fourier transform is in the discrete frequency domain. The results show that clutter noise is in the noise segment NB, and the demodulated tag signal component is in the tag segment TB.

[0093] Clutter noise can be represented by the following equation 2.

[0094] [Equation 2]

[0095]

[0096] Clutter noise can be generated by signals reflected from multiple surrounding objects. Equation 2 represents the sum of n signals reflected from multiple surrounding objects, and t nThis corresponds to the propagation delay until the signal returns after being reflected from the nth surrounding object. In Equation 2, all n signals have a period T, and the clutter noise consisting of the sum of the n signals also has a period T.

[0097] The tag signal 615 generated by the interrogation signal 610, which consists of a single-unit chirp signal, has a frequency that is a multiple of 1 / T. Therefore, in the case of the interrogation signal 610, which consists of a single-unit chirp signal, the obtained tag signal overlaps with the clutter noise signal, thus significantly degrading the SNR performance and making the data difficult to decode.

[0098] Conversely, in the case of the interrogation signal 620, which consists of repeated unit chirp signals, the tag signal 625 has a frequency that excludes multiples of 1 / T. The tag signal obtained from the interrogation signal 620, which consists of repeated unit chirp signals, can be expressed as Equation 3 below.

[0099] [Equation 3]

[0100]

[0101] Referring to Equation 3, it can be confirmed that the period of the tag signal according to the embodiment is not T. Therefore, the tag signal according to the embodiment can be separated from clutter noise signals, thereby improving the SNR.

[0102] Figure 7A This is a diagram showing the noise segment NB where clutter noise is located and the tag segment NB where the marker signal is located in the frequency domain.

[0103] Reference Figure 7A As described above, the unit chirped signal C constituting the interrogation signal IS is a series of interconnected periodic signals, making the phase continuous. Due to the characteristics of the Fourier transform of a periodic signal containing both signal and noise components, the result of the Fourier transform is in a discrete frequency domain. This result is in a frequency domain called segment-specific. In this result, clutter noise is in the noise segment NB, and the demodulated tag signal component is in the tag segment TB. The noise segment NB and the tag segment TB do not overlap in the frequency domain.

[0104] exist Figure 7A In the illustrated embodiment, two tag segments TB and one noise segment NB repeat periodically. This example corresponds to the case where three consecutive unit chirps constitute the interrogation signal IS. That is, when N consecutive unit chirps constitute the interrogation signal IS, (N-1) tag segments and one noise segment are formed.

[0105] The power of clutter noise is concentrated on the noise located in the noise segment NB, while the power of the noise component in the (N-1) tag segment TB is low. Therefore, the signal can be detected with a high SNR even when the power of the signal in the tag segment TB provided by the backscattering tag 200 through modulation is low.

[0106] Figure 7B This is a diagram showing the signals reflected by two backscattering tags at different distances from the interrogator 100 in the discrete frequency domain.

[0107] Reference Figure 7B The tag signals reflected by the first backscattering tag 2001 and the second backscattering tag 2002, respectively, are in a frequency range determined by the sum of frequencies corresponding to their respective distances from the interrogator 100. For example, when the first backscattering tag 2001 modulates the interrogation signal IS with frequency fm1, the tag signal can be formed at a frequency determined by the sum of frequencies corresponding to the distances between the first backscattering tag 2001 and the interrogator 100. For the distance being the distance between each backscattering tag and the interrogator 100, the frequency corresponds to the distance between the first backscattering tag 2001 and the interrogator 100. Clutter noise can be generated in The frequency corresponds to the distance between the first backscattering tag 2001 and the interrogator 100, and the tag signal and clutter noise can be spaced apart by fm1. In the interrogator's frequency domain, the tag signal can be formed as the sum of the frequency spaced apart by fm1 with the clutter noise and the frequency corresponding to the distance between the tag and the interrogator. The tag signal of the first backscattering tag 2001 can be formed as being spaced apart by fm1 in the frequency domain. Furthermore, according to the same principle, when the second backscattering tag 2002 modulates the interrogation signal IS at a frequency of fm2, the tag signal of the second backscattering tag can be spaced apart from the clutter noise by fm2 in the frequency domain.

[0108] Demodulation unit 120 (see) Figure 2 The signal corresponding to the noise segment NB can be filtered out from the output of the Fourier transform by using a filter, and the signal greater than the noise level can be found and demodulated in the frequency domain of the tag segment TB.

[0109] exist Figure 7BIn the illustrated embodiment, the backscattering tag 200 can multiply the interrogation signal IS by a certain frequency to generate the tag signal TS. Ideally, the tag signal TS needs to be represented within a tag segment TB. However, in practical applications, spectral leakage may occur, so the signal may be generated in J segments (typically J=4) around the tag segment TB. Signals in the J tag segments TB are all generated by multiplying the interrogation signal IS by the same frequency and have the same spacing size as the noise segments NB. That is, all J signals generated in a tag have the same frequency difference with the adjacent noise segments.

[0110] Therefore, even in the non-ideal case of spectral leakage, N FFT peaks with the same difference as the noise segment NB can be interpreted as signals from one tag, rather than N tags.

[0111] Even when the tag is moving, the tag signal generated and spaced apart from the clutter noise signal can be applied equivalently. Even when the position of tag segment TB in the frequency domain changes due to the movement of the backscattering tag, the signal generated in the moving tag has the same frequency difference as the adjacent noise segment NB. Therefore, the tag signal can be tracked and demodulated even when the backscattering tag 200 is moving.

[0112] As the number of unit chirps included in the interrogation signal IS increases, the number of tag segments TB located by the tag signals provided by the backscattered tags 200 increases. Therefore, large-scale communication between one interrogator 100 and multiple backscattered tags 200 is possible when communication is performed using the interrogation signal according to the embodiment.

[0113] Figure 8 This is a diagram showing the channel allocation based on the distance between the interrogator and each backscatter tag.

[0114] Reference Figure 8 In this embodiment, the channel can be divided into a channel width expressed as 1 / THz (T: the period of a unit chirped signal) and... The inter-channel distance (BW: frequency difference per unit chirp, c: speed of light). Backscatter tags 210, 220, and 230 can be assigned to channels generated based on the distances between interrogator 100 and backscatter tags 210, 220, and 230, respectively.

[0115] A backscattering tag (e.g., 210) can modulate data using a frequency shift keying (FSK) scheme within a channel width of 1 / T Hz used for channel access, without information about the assigned channel. In this case, data can be provided from a device connected to the backscattering tag (e.g., 210) or a device that includes the backscattering tag. The backscattering tag (e.g., 210) can reflect and thus provide the modulated tag signal TS to the interrogator 100.

[0116] As described above, even when the backscattering tags 210, 220 and 220 and 230, which modulate and reflect the interrogation signal IS at the same frequency, are arranged around the interrogator 100 that provides the interrogation signal IS, the frequencies of the signals received and demodulated by the interrogator 100 are different from each other when the distances between the backscattering tags 210, 220 and 230 and the interrogator 100 are different.

[0117] In this embodiment, the millimeter-wave bandwidth can be utilized based on the maximum distance D among the distances D between the backscattering tags 21O, 220, and 230 and the interrogator 100, as illustrated in the example below. Figure 3A As shown, the interrogator 100 outputs an interrogation signal consisting of continuous unit chirp signals C, and the backscatter tag 200 frequency-modulates the unit chirp signals C and reflects the modulated unit chirp signals C. (Refer to the above text.) Figure 5 The time difference Δt can be the time difference between the interrogation signal IS and the tag signal TS.

[0118] Bandwidth can be utilized by controlling the period (i.e., duration) and slope of the unit chirp signal, so that the time difference Δt falls within the period of the chirp signal C. In this case, the period of the unit chirp signal can be determined based on... (D: maximum distance between the backscattering tag and the interrogator, c: speed of light, T: period of the chirp signal) to calculate.

[0119] Because existing backscattering techniques have a significantly limited power budget, backscattering devices either lack an oscillator or are equipped with low-quality local oscillators ranging from tens of MHz. Therefore, in general, backscattering frequency modulation cannot utilize the entire millimeter-wave spectrum in the range of hundreds to thousands of MHz.

[0120] However, according to this embodiment, the entire bandwidth can be utilized by optimizing channel utilization, maximum scalability can be achieved by maximizing the tag segment TB of the channel, and simultaneous communication with all nodes in the network is possible. Therefore, the wide millimeter-wave band can be used as the communication band between multiple backscattering tags 210, 220, 230 and interrogator 100.

[0121] The number of channels resulting from distance-based channel allocation can vary depending on bandwidth. For example, a bandwidth of 14-GHz with a center frequency in the 60GHz ISM band can provide up to 4600 channels for a maximum separation distance D = 50m between the backscatter tag 200 and the interrogator 100. However, for the same maximum separation distance, the number of channels with a bandwidth of 250-MHz in the 24GHz ISM band is limited to 80.

[0122] Similarly, the inter-channel distance required for two different backscattering tags (e.g., 210 and 220) to be spaced apart to occupy different channels may also vary. At a center frequency of 60 GHz in the ISM band, the inter-channel distance is 10.7 mm, while at a center frequency of 24 GHz in the ISM band, the inter-channel distance is 600 mm.

[0123] In other words, the number of channels and the distance between channels depend on bandwidth and cannot be controlled, and allocating channels to a single tag may not provide sufficient scalability for dense networks. This may require a multi-channel access mechanism that can be configured across multiple tags to support different scalability requirements in a wide range of settings, including different spectral bands and network densities.

[0124] In this embodiment, the number of tag segments TB can be freely adjusted by controlling the number of unit chirp signals C contained in the symbols of the interrogation signal IS, and thus, multi-channel access can be performed. Increasing the number of tag segments provides space to simultaneously express more tag signals, thereby increasing scalability.

[0125] This embodiment provides unadjusted multi-channel access by allowing backscattered tags 200 to access a series of segments (e.g., sub-channels) containing bits with corresponding tag identifiers (IDs). Therefore, it is possible to prevent signal collisions across the network.

[0126] In this embodiment, the number of unit chirps included in a symbol is configured such that the number of bits per symbol is greater than the tag ID space. Specifically, N chirps per symbol (= logN bits per symbol) scale to (N-1) / 2 tags in 2-FSK. As the number of tag segments (TB) increases, the symbol duration increases, resulting in lower throughput. That is, increasing the chirp from N to N' reduces the throughput of 2-FSK tags by N / N'.

[0127] In this embodiment, as will be described below, seamless communication with the interrogator 100 is possible even when the backscatter tag 200 moves, without requiring additional cardinality design. As the backscatter tag 200 moves, the distance to the interrogator 100 changes, and therefore, the backscatter tag 200 can traverse multiple channels during the symbol duration.

[0128] Unlike a fixed backscattering tag 200, a moving backscattering tag 200 may have more than four spectral leaks, thus extending to several channels. However, unlike a fixed tag, the interrogator 100 can increase the frequency domain used to demodulate the signal provided by the moving tag to a value greater than 4, depending on the moving speed of the backscattering tag 200, for communication.

[0129] Figure 9A This is a diagram showing a prototype of a backscattering tag housed in an aluminum casing. Furthermore, Figure 9B This is a diagram showing the substrate of the backscattering tag. Additionally, Figure 9C This is a graph showing the reflection coefficient (S11) of a substrate with a backscattering tag having a closed switch.

[0130] Reference Figures 9A to 9C The prototype of the backscatter tag was fabricated on a Rogers RO4003C substrate with a MACOM MASW-011105GaAs SPDTRF switch. The RFC port of the switch was connected to a commercial 24GHz 17-dBi microstrip array antenna via a 2.92mm connector, and the RF1 / RF2 ports were connected to a matched 50Ω ground and an open circuit (infinite impedance), respectively.

[0131] This embodiment was evaluated using a total of six labels. Figure 9C This is a graph showing the results of measuring the return loss (S11) of the tag in a non-reflective state (i.e., matched ground) at 24 GHz. All backscattering tags exhibit a flat return loss of -9.5 dB in the reflective state, resulting in a total return loss difference of 20 dB or greater between the switching states at 24 GHz. In the experiments, the tag control signals were fed to a TerasIC T-Core P0633 FPGA board driven by an Altera MAX-10 chip, or an Arduino Uno board. Tag dimensions: 51.2 mm x 41.7 mm with the aluminum housing and 40.3 mm x 30.1 mm without the housing.

[0132] The prototype backscattering tag uses a MACOM RF switch operating at a conventional power consumption of 5 μW using a separate control board. For power consumption analysis, a ring oscillator and modulator circuit with a power consumption of 2 μW was used for frequency shifting and control logic, and the backscattering tag in this embodiment consumed a total of 7 μW. Since it is known that 100 μW of power can be harvested using energy harvesting, the backscattering tag in this embodiment can operate without a battery. As another example, the backscattering tag can operate for 24.5 years using a coin-sized coin cell battery (1000mAh).

[0133] Figure 10A This is a diagram showing a prototype of a backscattering tag implemented using a VanAtta array. Figure 10B This is a graph showing the results of measuring the beam pattern of a tag prototype with normalized power, and Figure 10C This is a diagram illustrating a prototype backscattered tag implemented in the 60 GHz Industrial, Scientific, and Medical (ISM) band. (See reference...) Figure 10A and Figure 10B The backscattering tag is based on the EVAL-ADRF5026 analog switch evaluation board, with RFC and RF1 ports connected to the same commercial 24-GHz antenna, and RF2 port connected to a matched 50Ω ground plane. A T-Core P0633 FPGA or Arduino Due is used to control the prototype tag using the VanAtta array. Figure 10B The pattern shown illustrates a retroreflection of -20 dB or greater over the entire 180-degree angle of incidence.

[0134] Reference Figure 10C Further implementation and evaluation of backscattering tags in the 60-GHz ISM band were conducted. As shown in the figure, the 60GHz tag is based on a V-band reflective SPST PIN diode switch (Eravant), with one end of the switch connected to a WR-15 waveguide angle antenna (Pasternack). The other end of the switch is connected to a WR-15WAVEGUIDE OPEN (Eravant) to implement S(11) suitable for tag operation. The transistor-to-transistor logic (TTL) signals of the 60-GHz tag are provided to a T-CoreP0633 FPGA or Arduino Due.

[0135] The interrogator in this embodiment is implemented using a custom reader based on software-defined radio (SDR) and three commercial radars. The custom reader uses two USRP X310s as signal transmitters and receivers. Each X310 is connected to EVAL-ADMV1013 and EVAL-ADMV1014 (analog devices), which act as 24-GHz RF signal up-converters and down-converters. A 6-GHz external local oscillator signal is supplied to the converter using a USRP B210, and then supplied to the signal mixer at a frequency of 24 GHz via an internal quadrupler on the converter board. The SDR implements the interrogator by generating and processing a continuous phase-chirped signal.

[0136] The 24-GHz reader is implemented using Distance2Go (Infineon) and EVAL Tinyrad (analog equipment), both commercial radars, while the 60-GHz reader is implemented using a suite of TImmWave ICBoost, IWR6843ISK, and DCA1000EVM. All radars provide an interface for real-time reception of raw data related to chirp demodulation results, as well as user-defined selections and parameters, such as the duration of a unit chirp signal, the interval between unit chirps, or the bandwidth and transmission power of a unit chirp signal.

[0137] To implement an interrogator using commercial radar, the transmission time between chirps was precisely calculated, and the corresponding phase shift over time was compensated by reconstructing the chirp data. Therefore, unit chirp signals are interconnected with zeros in between to correctly reflect the chirp phase. The time difference between chirps can be easily calculated using user-defined chirp parameters.

[0138] Figure 11A This is a diagram showing a reader implemented using the EVAL-Tinyrad commercial radar, and Figure 11B This is a diagram showing the beam characteristics of an omnidirectional TX antenna. (Refer to...) Figure 11A and Figure 11B The radar was configured for omnidirectional communication using a single Tx antenna and a single Rx antenna. The radar was configured with a maximum transmit power of 8 dBm and utilized the full 250-MHz bandwidth of the 24-GHz ISM band (24 GHz to 24.25 GHz). The duration of a single chirp signal, the guard time between single chirps, and the number of single chirps per symbol were set to 8.192 ms, 23 μs, and 32, respectively. 128 symbols from each measurement were analyzed, and their averages were calculated unless otherwise specified, and evaluated using prototype labels.

[0139] Figure 12This is a diagram illustrating backscattering tags arranged in different positions. Figure 12 1210 is an example of backscattered tags arranged in different locations within a 10m x 10m office space. Figure 12 1220 is an example of a backscattering label arranged in a cabinet. Figure 12 1230 is an example of a backscatter label arranged on a cardboard box. Figure 12 1240 is an example of a backscattered label that is blocked by a bookshelf, and Figure 12 The 1250 is an example of a backscattered label blocked by a metal partition.

[0140] Figure 13 Based on Figure 12 A diagram describing communication performance using backscattered tags arranged in a grid.

[0141] Figure 13 1310 shows Figure 12 The SNR of each of the 1210 arranged backscattered tags. Furthermore, Figure 13 The value 1320 in the figure represents the bit error rate (BER) of a single omnidirectional radar.

[0142] exist Figure 12 Of the 1210 backscattered tag locations, up to four locations were repeatedly selected and evaluated using backscattered tags modulated at 150 kHz, 152 kHz, 154 kHz, and 156 kHz. The backscattered tags simultaneously transmitted data, and the measured SNR was displayed. Figure 13 SNR heatmap of 1310 and Figure 13 The BER (Breakpoint) is shown in the 1320 graph. During the experiment, the radar's direction or position remained unchanged. As a result, the SNR for the entire office was 20 dB or higher, and the BER was less than 10%, demonstrating the performance of this embodiment and its high practicality. That is, according to this embodiment, its advantage is that tags can be arranged arbitrarily, and communication of all tags in an office can be fully supported using a single commercial antenna radar.

[0143] Figure 14 This is a diagram used to describe the communication performance when the interrogator and backscatter tag constituting the communication device according to this embodiment are partially blocked.

[0144] Figure 14 1410 shows the SNR measured in a university library with the communication devices according to this embodiment arranged and the interrogators and backscatter tags arranged in a manner obstructed by bookshelves. Figure 14 Figure 1420 shows the BER measured in a state where the communication equipment according to this embodiment is arranged in a university library, and the interrogator and backscatter tag are arranged to be blocked by the bookshelf. Figure 14 1430 is a plan view showing the state of setting up the interrogator and the backscatter tag, and Figure 14 Photo 1440 shows the status of the arranged interrogator and backscatter labels.

[0145] As shown in 1430 and 1440, experiments were conducted in a library where a wooden box and an iron frame were placed between the interrogator and the back label. The metal frame was 50 cm thick and spaced 124 cm apart, as shown in the figure. The experiment was conducted at a total of 8 locations, using labels with a modulation frequency of 10 kHz. The four locations in each row were spaced 135 cm apart in a direction parallel to the frame. The SNR and BER measured at the 8 label locations are shown in 1310 and 1320.

[0146] As shown in the figure, even with two steel frames between the tag and the radar, the average BER is 5%, and the SNR gain is as high as 58.4 dB. SNR and BER deteriorate at locations 4 and 8, where the obstruction on the line-of-sight (LOS) link is thicker because the signal is more likely to hit the metal posts on the frames. Due to the high SNR gain and clutter noise removal of this embodiment, communication was successfully achieved even in harsh non-LOS (NLOS) environments. These experimental results validate the stability of this embodiment in complex and realistic NLOS communication scenarios.

[0147] Figure 15A This diagram illustrates the various obstacles that exist between the interrogator ("radar" in the diagram) and the backscatter tag.

[0148] Figure 15B This is a graph showing the SNR measured when an obstacle is present. Figure 15C This is a graph showing the BER measured when obstacles are present.

[0149] Examples of obstacles used included a 0.5cm thick cardboard box, a 1cm thick glass window, a 13cm thick plaster wall, and a 4cm thick wooden door. The backscatter tag was completely obstructed by these obstacles, and the only way to communicate with the interrogator was through them. The backscatter tag was modulated at 156kHz for the experiments. Each experiment was conducted with a distance of 122cm between the tag and the radar. The radar, implemented as an interrogator, demonstrated excellent SNR and BER characteristics even under obstruction conditions, exhibiting high SNR gains of 40dB or higher and a BER as high as 6.7%. The communication stability under various obstruction conditions demonstrated the feasibility of using the tag for communication in different rooms.

[0150] Figure 16A It is a photograph showing an auditorium measuring 20m x 20m that was used for large-scale communication experiments.

[0151] Figure 16B This is a diagram illustrating a scene with backscattered tags arranged. To confirm the large-scale communication of this embodiment, such as... Figure 16A As shown, the BER was calculated from tags located in 1100 different location-frequency pairs with a size of 20m x 20m. The distance between the interrogator and the backscattered tag ranged from 0.3m to 14.1m, and the modulation frequency ranged from 7315Hz to 7414Hz. The large-scale distributed BER was measured by summing all 1100 signal pairs.

[0152] Figure 17 It is a graph used to describe the signals of multiple backscattered tags and the BER performance of multiple backscattered tags.

[0153] Figure 17 Figure 1710 is a diagram showing the signals of 1100 backscattered tags along the channel, and Figure 17 Figure 1720 is a graph showing the BER of all backscattered tags. (Reference) Figure 17 Figures 1710 and 1720 show the partial amplification and demodulation results of the summed signals, and it can be seen that, according to this embodiment, the backscattering tags are located in different channels based on distance-based frequency division multiple access. However, some tags share channels with other tags.

[0154] Figure 1720 shows the aggregated BER for the number of aggregated tags after signal summation. The tag signals are summed in ascending order of distance. The demodulation results, with BERs less than 2% for all 1100 tag signals, indicate the possibility of large-scale communication. It can be seen that newly added tags have increased communication distances, and therefore, the aggregated BER increases with the number of added tags. It is also noted that additive white Gaussian noise (AWGN) is added with the signal summation, leading to a more severe situation; however, even under these conditions, the interrogator of this embodiment is able to successfully demodulate all signals. This is achieved by removing clutter noise and using a large-scale network channel allocation design in this embodiment, and it can be expected that backscattered tags can operate at scale with improved SNR in practice.

[0155] Figure 18A This is a diagram showing the path of the backscattered tag horizontally away from the interrogator. Figure 18B This is a diagram showing the channel when the backscattered tag is horizontally far from the interrogator, and Figure 18C This is a graph used to describe the BER (Breakpoint) when the backscattered tag is horizontally far from the interrogator. Additionally, Figure 19A It is a diagram showing the path of the backscattered tag perpendicularly away from the interrogator, and Figure 19B This is a graph used to describe the BER when the backscattered tag is perpendicular to the interrogator.

[0156] Reference Figures 18A to 19B Since this embodiment does not require beamforming in the interrogator, signals reflected by movable backscattering tags can be successfully detected and demodulated. Experiments were conducted in a mobile environment with the chirp count per symbol set to 8, and a total of 1664 symbols were analyzed for evaluation. Figure 18A A simple indoor mobility experiment is shown, in which the tag moves horizontally in a straight line at a distance of at least 3 m from the radar, at a distance of 4.15 m. The measurement lasted 13.7 seconds, during which the tag moved at a speed of 0.3 m / s. Figure 18B The channel allocation during the time period based on the radar tag distance movement is shown, and the results of these mobility experiments confirm that this embodiment has excellent communication performance even in mobile environments. Figure 18C The BER over time is shown, with an average BER of 6.4% during the movement.

[0157] Figure 19A Another indoor mobility was demonstrated, in which the tag moved vertically along a straight line for 4.32m (from point 2.48m to point 6.8m) at a speed of 0.9m / s for 48.5 seconds. Figure 19B The BER over time is shown, with an average BER of 6.2% during mobility. Tags in both experiments were modulated at 156 kHz. The resulting curves demonstrate successful demodulation of tag signals even in mobile environments.

[0158] Various embodiments may be implemented or supported by one or more computer programs, which may be generated from computer-readable program code and stored in a computer-readable medium. In this disclosure, the terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, classes, instances, and associated data that are suitable for implementation as computer-readable program code or a portion thereof. The term "computer-readable program code" can include various types of computer code, including source code, object code, and executable code. The term "computer-readable medium" can include various types of media accessible by a computer, such as ROM, RAM, hard disk drive (HDD), optical disk drive (CD), DVD, or various types of memory.

[0159] Furthermore, machine-readable storage media can be provided in the form of non-transitory storage media. Here, the term "non-transitory storage media" refers to a tangible device and may exclude wired, wireless, optical, or other communication links that transmit temporary electrical or other signals. Moreover, the term "non-transitory storage media" does not distinguish between cases where data is stored semi-permanently in a storage medium and cases where data is temporarily stored. For example, a non-transitory storage medium may include a buffer that temporarily stores data. Computer-readable media can be any available medium accessible by a computer and may include volatile or non-volatile media as well as removable or non-removable media. Computer-readable media includes media that can permanently store data and media that can store data and be rewritten later, such as rewritable optical discs or erasable storage devices.

[0160] According to embodiments, methods according to various embodiments may be included in and provided in a computer program product. The computer program product may be traded as a commodity between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., CD-ROM), or distributed online through an app store (e.g., downloaded or uploaded), or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored in a machine-readable storage medium, such as the memory of a manufacturer's server, an app store's server, or a relay server.

[0161] While specific examples and descriptions have been provided, those skilled in the art will understand that various changes in form and detail can be made without departing from the spirit and scope of the invention. For example, the described techniques may be performed in a different order than the components of the described methods and / or systems, structures, devices, circuits, etc.; may be combined or integrated in a different manner than the described methods; or may be replaced or substituted by other components or equivalents to achieve suitable results. Therefore, it should be understood that the above embodiments do not limit the scope of this disclosure. For example, each element described as a single type may be performed in a distributed manner, and elements described in a distributed manner may also be performed in an integrated manner.

[0162] The scope of this invention is not limited by the detailed description of the invention, but by the following claims. All modifications or alternatives derived from the scope and spirit of the claims and their equivalents are within the scope of this invention.

[0163] According to an embodiment, a backscatter communication method and apparatus for large-scale communication in low-power wide bandwidth can be provided.

[0164] It should be understood that the embodiments described herein are for illustrative purposes only and not for limiting purposes. The description of features or aspects in each embodiment should generally be considered applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of this disclosure as defined by the appended claims.

Claims

1. A communication device, comprising: An interrogator is configured to output an interrogation signal in which N unit chirped signals are repeated at a predetermined period T, wherein N is a natural number equal to or greater than 2; and The backscattered tag is configured to receive interrogation signals over a channel width of 1 / T Hz using a frequency shift keying (FSK) scheme and to frequency modulate the interrogation signals to generate and provide tag signals. The interrogator is further configured to mix a received signal, including a tag signal provided by a backscattered tag, with an interrogation signal to generate an intermediate signal, perform a Fourier transform on the intermediate signal or a signal filtered from the intermediate signal, the Fourier transform signal including N-1 tag segments repeatedly formed along the frequency axis and a noise segment, and demodulate the tag signal from the frequency components of the Fourier transform signal other than the noise segment, and the frequency components other than the noise segment are included in the N-1 tag segments.

2. The communication device of claim 1, wherein the plurality of unit chirped signals are phase-continuous.

3. The communication device as described in claim 1, wherein, The query signal belongs to the millimeter wave band.

4. The communication device as described in claim 1, wherein, The interrogator includes: The demodulation unit is configured to demodulate the tag signal, and The demodulation unit includes: A mixer configured to mix an interrogation signal with the received signal to generate an intermediate signal, the received signal including a tag signal formed by frequency modulation of the interrogation signal by a backscattered tag; and The Fourier transform unit is configured to perform fast Fourier transform on intermediate signals, and The filter is configured to block frequency components in the intermediate signal that correspond to the sum of the frequency of the tag signal and the frequency of the query signal.

5. The communication device of claim 1, wherein the interrogator further comprises... Demodulation unit, configured to demodulate tag signals; and The demodulation unit includes: The filter is configured to receive an intermediate signal and transmit a signal component having a frequency corresponding to the difference between the frequency of the interrogation signal and the frequency of the tag signal.

6. The communication device as described in claim 1, wherein, The interrogator performs a Fourier transform on the intermediate signal, which includes periodically located clutter noise and a component of the tag signal located in the frequency domain that does not overlap with the clutter noise.

7. The communication device as claimed in claim 6, wherein, Clutter noise is in the noise range of the frequency domain, and The tag signal components are in the tag segment in the frequency domain.

8. The communication device of claim 7, wherein the tag signal is in one or more tag segments, and the frequency of the backscattered tag modulation is spaced apart from a plurality of noise segments respectively adjacent to the one or more tag segments.

9. The communication device as described in claim 8, wherein, The interrogator includes a demodulation unit configured to demodulate the tag signal, and As the backscatter tag moves, the demodulation unit tracks the signal of the moving backscatter tag by tracking the signal of the frequency modulated by the backscatter tag at intervals of the plurality of noise segments.

10. The communication device of claim 1, wherein the backscatter tag is included in an Internet of Things (IoT) device.

11. The communication device of claim 1, wherein the backscatter tag operates by using power harvested through energy harvesting.

12. The communication device of claim 1, wherein the backscatter tag communicates with the interrogator via a channel determined based on the distance between the interrogator and the backscatter tag.

13. The communication device according to claim 1, wherein the interrogation signal is composed of N periodic unit chirped signals, and the tag signal is in N-1 discrete frequency bands in each channel.

14. The communication device of claim 1, wherein the backscatter tag is configured to frequency modulate the interrogation signal received from the interrogator via the backscatter tag without information about the channel allocated to the backscatter tag, and to provide the frequency-modulated output signal as the tag signal.

15. The communication device according to claim 1, wherein, The signal generated by demodulating the tag signal provided by the backscattering tag includes a frequency component corresponding to the distance the interrogation signal travels between the interrogator and the backscattering tag.

16. The communication device according to claim 15, wherein, The signal generated by demodulating the tag signal provided by the backscatter tag also includes a frequency component corresponding to the frequency at which the interrogation signal is modulated.

17. The communication device according to claim 1, wherein: The communication device includes multiple backscatter tags. The interrogator receives multiple tag signals formed by modulating the interrogation signal with the multiple backscattered tags, and performs simultaneous communication with the multiple backscattered tags.

18. The communication device as claimed in claim 1, wherein, The backscattering tag is operated by power supplied by a battery.

19. An interrogator, comprising: A signal generator configured to output an interrogation signal in which N unit chirped signals are repeated at a predetermined period T, wherein N is a natural number equal to or greater than 2; and Demodulation unit; The demodulation unit includes: A mixer configured to mix a received signal, including a tag signal, with an interrogation signal to generate an intermediate signal, the tag signal being formed by frequency modulation of the interrogation signal via a backscattered tag within a channel width of 1 / T Hz using a frequency shift keying (FSK) scheme; and A Fourier transformer configured to perform a Fourier transform on an intermediate signal or a signal filtered from an intermediate signal, wherein the Fourier transformed signal comprises N-1 tag segments repeatedly formed along the frequency axis and a noise segment; The demodulation unit is further configured to demodulate the tag signal from the frequency components of the Fourier transform signal, excluding the noise segment, and the frequency components excluding the noise segment are included in the N-1 tag segments.

20. The interrogator as claimed in claim 19, wherein, The query signal belongs to the millimeter wave band.

21. The interrogator as claimed in claim 19, wherein, The demodulation unit also includes a filter configured to receive the interrogation signal and transmit a signal component having a frequency corresponding to the difference between the frequencies of the interrogation signal and the tag signal.

22. The interrogator as claimed in claim 19, wherein, When the interrogator performs a Fourier transform on the intermediate signal, the intermediate signal of the Fourier transform includes components of periodically located clutter noise and tag signals located in the frequency domain that do not overlap with the clutter noise.

23. The interrogator according to claim 19, wherein, The interrogation signal consists of N periodic chirp signals, and the tag signal is in N-1 discrete frequency bands in each channel.

24. The interrogator according to claim 19, wherein, The backscatter tag is configured to frequency modulate the interrogation signal received from the interrogator via the backscatter tag without information about the channel allocated to the backscatter tag, and to provide the frequency-modulated output signal as the tag signal.

25. The interrogator according to claim 19, wherein, The signal generated by demodulating the tag signal provided by the backscattering tag includes a frequency component corresponding to the distance the interrogation signal travels between the interrogator and the backscattering tag.

26. The interrogator according to claim 19, wherein, Multiple unit chirped signals are in phase continuity.

27. The interrogator according to claim 19, wherein, The interrogator receives multiple tag signals formed by modulating the interrogation signal with multiple backscattered tags, and performs simultaneous communication with the multiple backscattered tags.

28. The interrogator as claimed in claim 19, wherein, The demodulation unit further includes: The filter is configured to block frequency components in the intermediate signal that correspond to the sum of the frequency of the tag signal and the frequency of the query signal.

29. The interrogator as claimed in claim 19, wherein, Backscattering tags are included in Internet of Things (IoT) devices.

30. A communication method, wherein, The interrogator includes a signal generator and a demodulation unit that communicates with a backscatter tag, and the method includes: An interrogation signal is generated by outputting N unit chirped signals from a signal generator, which repeat at a predetermined period T, where N is a natural number equal to or greater than 2; and The received signal, including the tag signal, is mixed with the interrogation signal by the demodulation unit to generate an intermediate signal. The tag signal is formed by frequency shift keying (FSK) of the interrogation signal within a channel width of 1 / T Hz using a backscattered tag. A Fourier transform is performed on the intermediate signal or the signal filtered from the intermediate signal by a demodulation unit, wherein the Fourier transform signal includes N-1 tag segments repeatedly formed along the frequency axis and a noise segment; and The demodulation unit demodulates the tag signal from the frequency components of the Fourier transform signal, excluding the noise segment, and the frequency components excluding the noise segment are included in the N-1 tag segments.

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