Method for determining the location of a communication device using FMCW (Frequency Modulation Continues Wave) radar

Abstract

Existing methods for determining the location of a communication device using FMCW radar use the frequency reflected from the communication device to calculate the frequency difference between the FMCW radar transmission signal and the reflected wave from the communication device. However, in the process of identifying the frequency difference, only the reciprocal frequency of the unit chirp time length is measured with a resolution, and the exact frequency cannot be measured. In order to solve the above problems, the present invention uses an FMCW radar and a frequency modulation tag, transmits a continuous chirp signal from the FMCW radar, calculates an intermediate signal IF, which is the frequency difference between the simultaneously received signals, and demodulates the accurate modulation frequency f_m, thereby enabling the rapid and accurate measurement of the distance between the FMCW radar and the communication device.

Description

[Technical Field]

[0001] The present invention relates to a technique for precisely measuring a position using a communication device, and more particularly to a technique for improving the position accuracy of a communication device by utilizing signal processing techniques. [Background technology]

[0002] Prior to the filing of the present application, a technology relating to an interrogator and a communication device including the same was disclosed. This technology includes an interrogator that outputs an interrogation signal consisting of a series of unit chirp signals that change from a first frequency to a second frequency, and a backscatter tag that receives the interrogation signal, frequency-modulates it, and forms and provides a tag signal.

[0003] Another prior art discloses a method and apparatus for performing communication based on backscattering in a wireless communication system. This technology includes an interrogator that outputs an interrogation signal consisting of a series of unit chirp signals that change from a first frequency to a second frequency, and a backscatter tag that receives the interrogation signal, frequency-modulates the interrogation signal, and forms and provides a tag signal, and the interrogator receives and demodulates the tag signal. Summary of the Invention [Problem to be solved by the invention]

[0004] Existing methods for determining the location of a communication device using FMCW radar use a frequency reflected from the communication device to calculate the frequency difference between the FMCW radar transmission signal and the reflected wave from the communication device. However, in the process of identifying the frequency difference, only the reciprocal frequency of the unit chirp time length is measured with a resolution, and the exact frequency cannot be measured. For this reason, the resolution for identifying the frequency difference is limited, which can lead to errors in measuring the distance of the communication device.

[0005] The present invention aims to eliminate distance measurement errors between the FMCW radar and the communication device that occur due to the inability to accurately measure the frequency difference.

[0006] The communication device may include either an active frequency modulation tag with a power source and a receiving antenna and a transmitting antenna that modulates received signals and generates reflected signals, or a passive frequency modulation tag that receives radar signals, modulates the signals, and reflects them.

[0007] In the present invention, we use the same term as the communication device: frequency modulation tag.

[0008] In addition, the FMCW radar comprises a signal generator that generates various types of transmission signals, a transmitting antenna that transmits the generated signals, a receiving antenna that receives the signals, and a signal processing unit, and in some cases, the signal generator and transmitting antenna, and the receiving antenna and signal processing unit that receive the signals may be provided separately. [Means for solving the problem]

[0009] The invention to solve the above problems is configured as follows.

[0010] Using FMCW radar and frequency modulation tags, The method for determining the location of a communication device using an FMCW radar includes transmitting a continuous chirp signal from the FMCW radar and calculating an intermediate signal IF, which is the difference in frequency between the received signals; the tag signal, which is the intermediate signal of the reflected wave obtained by reflecting the continuous chirp signal from a frequency-modulated tag, is the sum of a modulation frequency f_m and a distance frequency F_r, which indicates distance due to time shift; and calculating the modulation frequency f_m of the tag signal from the FMCW radar by subtracting the frequency of the most adjacent surrounding reflected signal that is smaller than the maximum peak frequency from the maximum peak frequency of the tag signal modulated by the frequency-modulated tag, which is located among surrounding reflected signals located at integer multiples of the reciprocal frequency of a unit chirp time length in the frequency domain.

[0011] It also uses FMCW radar and frequency modulation tags, The present invention provides a method for calculating a distance frequency indicating a distance between the FMCW radar and a frequency-modulated tag from a tag signal transmitted by the frequency-modulated tag, the method comprising: demodulating a sinc function of the tag signal received by the frequency-modulated tag using a modulation frequency spectrum leakage feature value of the tag signal received by the frequency-modulated tag, the modulation frequency spectrum leakage feature value being centered on a maximum peak frequency of the signal modulated by the frequency-modulated tag, which is located between periodically located peripheral reflected signal frequencies in the frequency domain, and not overlapping with the periodically located peripheral reflected signal frequencies; and calculating the distance frequency by subtracting the modulation frequency from the center frequency of the demodulated sinc function. It also uses FMCW radar and frequency modulation tags, In the method for measuring the distance between the FMCW radar and the frequency modulation tag, a radar transmission signal generating step of generating a radar transmission signal by the FMCW radar; a counter-transmission step of receiving the radar transmission signal generated in the radar transmission signal generating step by using a tag receiving antenna provided in the frequency modulation tag, modulating the frequency by f_m in a modulation unit provided in the frequency modulation tag, and transmitting the modulated signal from a tag transmitting antenna of the frequency modulation tag; a signal receiving step of receiving the modulated signal transmitted in the counter-transmitting step by a receiving antenna provided in the FMCW radar; a reception frequency pre-processing step of generating an intermediate signal by mixing the frequency transmitted from the FMCW radar with the received frequency to calculate the sum of a distance frequency, which is a difference between the frequency transmitted from the FMCW radar and the frequency received in the signal receiving step, and a modulation frequency; a frequency domain conversion step of converting the intermediate signal generated in the reception frequency pre-processing step into a frequency domain; a separation frequency confirmation step of confirming periodically located surrounding reflected signal frequencies in the frequency domain intermediate signal converted in the frequency domain conversion step and a tag signal modulated by the frequency modulation tag; The method for determining the location of a communication device using an FMCW radar includes calculating the modulation frequency f_m by subtracting the frequency of the most adjacent peripheral reflected signal, which is smaller than the maximum peak frequency of the tag signal among the periodically positioned peripheral reflected signals, from the maximum peak frequency of the tag signal modulated by the frequency modulation tag.

[0012] It also uses FMCW radar and frequency modulation tags, In the method for measuring the distance between the FMCW radar and the frequency modulation tag, a radar transmission signal generating step of generating a radar transmission signal by the FMCW radar; a counter-transmission step of receiving the radar transmission signal generated in the radar transmission signal generating step by using a tag receiving antenna provided in the frequency modulation tag, modulating the frequency by f_m in a modulation unit provided in the frequency modulation tag, and transmitting the modulated signal from a tag transmitting antenna of the frequency modulation tag; a signal receiving step of receiving the modulated signal transmitted in the counter-transmitting step by a receiving antenna provided in the FMCW radar; a reception frequency pre-processing step of generating an intermediate signal by mixing the frequency transmitted from the FMCW radar with the received frequency to calculate the sum of a distance frequency, which is a difference between the frequency transmitted from the FMCW radar and the frequency received in the signal receiving step, and a modulation frequency; a frequency domain conversion step of converting the intermediate signal generated in the reception frequency pre-processing step into a frequency domain; a separation frequency confirmation step of confirming periodically located surrounding reflected signal frequencies and tag signals modulated by the frequency modulation tag in the intermediate signal in the frequency domain converted in the frequency domain conversion step; The present invention provides a method for determining the location of a communication device using an FMCW radar, comprising: demodulating a sinc function of a signal received by a frequency-modulated tag using a modulation frequency spectrum leakage feature value of the signal received by the frequency-modulated tag that does not overlap with the periodically located surrounding reflected signal frequencies, centered on the maximum peak frequency of the tag signal modulated by the frequency-modulated tag, in the frequency domain; and calculating the center frequency of the demodulated sinc function as the sum of the distance frequency and the modulation frequency.

[0013] The present invention also provides a method for measuring the position of a communication device using an FMCW radar, characterized in that in the frequency domain, a value obtained by subtracting a modulation frequency f_m from the center frequency is calculated using a distance frequency F_r indicating distance.

[0014] The present invention also provides a method for determining the position of a communication device using an FMCW radar, wherein the radar signal generated by the FMCW radar is any one of a periodically repeated signal of two or more continuous chirp signals, an intermittently periodically repeated signal of two or more continuous chirp signals, a discontinuously periodically repeated signal of two or more chirp signals, and a discontinuously intermittently periodically repeated signal of two or more chirp signals.

[0015] In addition, a method for measuring the position of a communication device using an FMCW radar is provided, characterized in that the inverse of F_r is calculated using the time delay due to distance and multiplied by the speed of light to calculate the distance between the FMCW radar and the frequency modulation tag. [Effects of the Invention]

[0016] The present invention has the effect of providing a technology that can quickly and accurately measure the distance between an FMCW radar and one or more fixed or moving frequency modulation tags with frequency modulation function using an FMCW radar and a frequency modulation tag with frequency modulation function, by using the above-mentioned inventive configuration. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a conceptual diagram and an internal configuration diagram of an FMCW radar and a communication device (tag, frequency conversion tag) of the present invention. [Figure 2] FIG. 1 is a diagram illustrating the configuration of an FMCW radar and multiple communication devices (tags) according to the present invention. [Figure 3] 1 is a time domain signal graph of a communication signal used with an FMCW radar and multiple communication devices of the present invention; [Figure 4] The types of signals (chirp signals and their modified signals) that can be used for distance measurement in the FMCW radar of the present invention. [Figure 5] 10 is a frequency domain comparison graph of intermediate signal reception results using an existing FMCW radar and a frequency conversion tag, and intermediate signal reception results using an FMCW radar using a continuous chirp signal of the present invention and a frequency conversion tag. [Figure 6] 1 is a graph showing the tag signal of a frequency-converted tag received by an FMCW radar of the present invention in the frequency domain, and calculating the modulation frequency f_m of the frequency-converted tag. [Figure 7] 10 is a graph showing a demodulated sinc function graph of a frequency-converted tag received signal using spectral leakage features in the frequency domain of the tag signal of the frequency-converted tag received by the FMCW radar of the present invention. [Figure 8] 1 is a diagram illustrating the sequence of signal processing of a tag signal of a frequency conversion tag received by an FMCW radar of the present invention. [Figure 9] FIG. 1 is a conceptual diagram showing how the distances of multiple frequency-converting tags from an FMCW radar are measured using the FMCW radar of the present invention and multiple frequency-converting tags. [Figure 10] 1 is a diagram showing the measurement of the positions of multiple tags on a plane using the FMCW radar of the present invention and multiple frequency conversion tags. [Figure 11] 10 is a graph showing the results of calculating the sinc function of individual tag signals to measure the position of multiple tags on a plane using the FMCW radar of the present invention and multiple frequency-converting tags. [Figure 12] FIG. 1 is an explanatory diagram showing the case where the FMCW radar of the present invention and two frequency conversion tags are used, with the frequency conversion tag fixed to a moving object and the frequency conversion tag fixed to a stationary object. [Figure 13] 1 is a graph showing a tag signal in the frequency domain when a frequency conversion tag of the present invention is used and the tag is fixed to a moving object. [Figure 14] FIG. 1 is an explanatory diagram showing a case where the FMCW radar of the present invention and multiple frequency conversion tags are used, with frequency conversion tags fixed to a moving object, and a case where frequency conversion tags are fixed to a stationary object. [Figure 15] 1 is an explanatory diagram showing transmitted and received signals when the FMCW radar of the present invention and one frequency conversion tag are used to measure the distance between the FMCW radar and the frequency conversion tag. FIG. [Figure 16] 1 is an embodiment for locating a frequency transform tag in 2D or 3D space. [Figure 17] 10 is yet another embodiment for locating a frequency transforming tag in 2D or 3D space. [Figure 18] 10 is another embodiment of the present invention for simultaneously detecting fixed and moving frequency conversion tags in 2D or 3D space. DETAILED DESCRIPTION OF THE INVENTION

[0018] The effects of the above-described configuration of the present invention will be described below with reference to the accompanying drawings.

[0019] FIG. 1 shows a conceptual diagram and internal configuration of an FMCW radar and a communication device (tag, frequency conversion tag) according to the present invention. The upper diagram illustrates the concept of an FMCW radar and a communication device transmitting and receiving signals to and from each other, while the lower diagram illustrates the conceptual configuration of the FMCW radar and the communication device, respectively. The FMCW radar comprises a transmitter for transmitting signals to the communication device, a receiver for receiving signals transmitted back from the communication device, and a positioning algorithm for calculating position information from the received signals. The communication device comprises a transmitting / receiving antenna and a modulator, and further comprises a separate control signal to control the modulator. The transmitting / receiving antenna may be separated into a transmitting antenna and a receiving antenna. The FMCW radar uses various chirp signals and is equipped with a chirp signal generator for this purpose. The generated chirp signal is transmitted via a splitter to the transmitting antenna. The transmit signal transmitted via the splitter to the mixer is multiplied by the receive signal received via the receiving antenna in the mixer to generate an intermediate signal (IF). The generated IF signal is converted into a frequency domain signal and separated into an ambient reflection signal (noise signal) and a communication device signal (tag signal). The separated communication device signal is demodulated using a spectral leakage characteristic frequency to accurately determine the location of the communication device. The communication device can be any device comprising a receiving antenna, a modulator, and a transmitting antenna, and is even easier to use if it is in the form of a tag that is easily attached and usable. In the present invention, a tag can be used as the same expression as the communication device, but to distinguish it from a general tag without a frequency conversion function, it can also be referred to as a frequency modulation tag.

[0020] For frequency modulation, the modulation unit of the tag repeatedly switches between two or more impedance values. The modulation unit switches the impedance value according to the value of an externally input control signal, and the control signal can be adjusted using various means such as the output of a voltage-controlled oscillator (VCO), switching between multiple fixed oscillators, or directly generated by a separate processor (e.g., MCU).

[0021] Figure 2 shows the configuration of an FMCW radar and multiple communication devices (tags) of the present invention. Multiple frequency-converted tags receive a radar chirp signal generated by FMCW and transmit a different converted frequency for each tag. The FMCW radar receives these transmitted signals, separates and recognizes each tag, and calculates the distance for each tag.

[0022] Figure 3 is a time-domain graph of a signal reflected by a communication device received by an FMCW radar according to the present invention. Signals generated by the FMCW radar are reflected by objects, buildings, and other objects in space and received by the FMCW radar with a certain time delay (dt). The reflected signal from the communication device (frequency-converted tag) undergoes internal frequency conversion and is received by the FMCW radar separated by the object, building, and object signals by the modulated frequency signal. However, because this is a time domain graph, it can be seen that multiple signals are measured overlapping on the X-axis, which indicates the same time. However, because the Y-axis values, which indicate their respective frequencies, do not overlap, these signals can be measured separately in the frequency domain.

[0023] FIG. 4 illustrates types of signals (chirp signals and their modified signals) that can be used for distance measurement in the FMCW radar of the present invention. A chirp signal refers to a signal whose frequency changes linearly over time. It does not necessarily have to change linearly over the entire frequency range, but includes signals that are periodically repeated and whose increasing and decreasing portions are symmetrical or asymmetrical. FIG. 4 illustrates that various types of chirps can be used, partially or entirely. The present invention can also use chirp signals of types not shown in FIG. 4 as needed. Signals can be generated and used discontinuously, continuously, continuously, discontinuously, or discontinuously. Such signals can be used periodically for a certain period of time. In FIG. 4, the number and time length of the continuous chirp signal can be adjusted. Increasing the number of chirps improves frequency resolution and allows for the operation of a larger number of tags. Increasing the chirp length allows for the observation of tags at greater distances. On the other hand, if the number and length of chirps are reduced, the tag's location information can be updated at a faster rate. An appropriate continuous chirp signal setting can be selected depending on the application environment of the technology.

[0024] Figure 5 is a graph comparing the results of intermediate signal reception using a conventional FMCW radar and a frequency-converted tag with the results of intermediate signal reception using an FMCW radar using a continuous chirp signal of the present invention and a frequency-converted tag in the frequency domain. In Figure 5(a), the communication device signal performing 40 Hz frequency modulation is expressed at a frequency similar to the ambient reflected signals (noise) generated by nearby surrounding objects (clutter) in the FMCW radar, and the signal is so small that it is impossible to recognize. In (b), the communication device signal performing 40 Hz frequency modulation is expressed after being separated from the ambient reflected signals using continuous chirp interrogation. In this case, the distance accuracy of the communication device is 2 BW / C (60 cm in the 250 MHz frequency band), the same as that of conventional FMCW radar.

[0025] The continuous chirp radar transmission method, which adds continuous chirp signal processing to FMCW radar, effectively separates the tag FSK signal from surrounding reflected signals in the frequency domain. Compared to the existing FMCW method, which uses an intermittent single chirp signal c(t), the continuous chirp interrogation method uses multiple continuous chirp signals as the radar transmission signal. s(t)=c(t)*Σ n=1 N δ(t-nT) where c(t) is a single chirp, T is the chirp duration, N is the number of chirp repetitions, and * denotes convolution. That is, s(t) is the signal in which the chirp c(t) is repeated N times with a period T, as shown in the lower left of Figure 5.

[0026] When this radar transmission signal is reflected by surrounding reflectors (i.e., clutter), a propagation delay is reflected, resulting in s(t-dt), where dt is the round-trip propagation delay between the radar and the clutter. In the continuous chirp interrogation method, the radar transmission signal reflected by the clutter and received is simply a time-shifted radar transmission signal, so it maintains its period T. Therefore, the radar intermediate signal IF of the clutter (surrounding reflection signal, measurement noise) appears as peaks at integer multiples of 1 / T Hz frequency (because a signal with period T is expressed as the sum of integer multiples of 1 / T Hz frequency), and all other frequency components that are not integer multiples of 1 / T Hz are zero. This applies to all clutter noise; that is, all noise is concentrated at the same frequency set.

[0027] On the other hand, the backscatter signal (communication device signal) reflected by the communication device has its period changed by FSK (Frequency Shift Keying) on ​​the FMCW radar transmission signal. Specifically, the signal reflected from the communication device is expressed by the following equation: s(t-dt)*e j2πfmt Interrogation signal * FSK (period T) (period 1 / fm) Here, f_m is the FSK modulation frequency, and its period is 1 / f_m, which differs from the FMCW radar chirp signal period T. As a result, the period of the communication device signal becomes the least common multiple of the new period T and 1 / f_m, rather than T. As a result of this frequency modulation, the communication device's reflected signal is expressed at a frequency that is not an integer multiple of 1 / T during conversion to an intermediate signal, and is therefore separated from clutter noise and displayed in the frequency domain. The separation of the communication device signal and clutter (surrounding reflected signals, noise) can be seen in Figure 5.

[0028] 6 is a graph showing the frequency domain of the received signal from the FMCW radar and the frequency-converted tag of the present invention, and calculating the modulation frequency f_m of the frequency-converted tag. The received signal from the frequency-converted tag is a signal that includes a frequency change F_r due to time delay and a frequency change f_m due to frequency modulation performed within the frequency-converted tag. Therefore, it is possible to calculate the frequency difference f_m due to frequency modulation, and then calculate the frequency change F_r due to time delay, and use this to calculate distance.

[0029] The first step in obtaining an accurate estimate of the frequency change due to time delay, i.e., the distance frequency F_r, is to remove the effect of f_m using an intermediate frequency (IF) signal. While it is possible to design a modulation frequency when designing communications equipment, f_m is not always constant due to oscillator instability, and must be measured and used in real time. For example, a quartz oscillator has a deviation of approximately 500 ppm in various environments, and even an oscillator circuit constructed with an LCR circuit or other device will experience temperature-related changes. Therefore, when calculating F_r using the designed f_m frequency without actual measurement, a large distance error of more than 24.6 cm was measured.

[0030] The position tracking method of the present invention can accurately measure f_m without dictionary knowledge of the modulation rate of the communication device or the environment in which the communication device is installed. To accurately identify f_m, F_r can be measured using the principle of using a multi-chirp signal (s(t-dt)) with a period T, i.e., F_r is the propagation delay due to the difference in distance between the FMCW radar and the communication device. f_m is determined by the period 1 / f_m. j2πfmt The FSK signal s(t-dt) is frequency shifted by f_m. Due to this frequency shift, the intermediate signal IF of the communication device signal is displayed at a position f_m away from the 1 / T Hz integer multiple frequency peak as shown in Figure 6. Therefore, f_m can be accurately calculated in real time based on the frequency difference between the communication device signal and the adjacent 1 / T Hz integer multiple frequency peak.

[0031] To remove f_m, first nullify the clutter noise to 0, and then move the communication device signal to the nullified frequency interval, thereby removing f_m. This is because removing f_m from the communication device signal places the signal at an integer multiple of 1 / T Hz where clutter noise exists.

[0032] Figure 7 shows a graph of the sinc function of the frequency-converted tag signal received by the FMCW radar of the present invention, demodulated using spectral leakage features in the frequency domain. The center frequency of the sinc function represents the sum of the distance frequency and the modulation frequency. The modulated frequency f_m can be accurately removed using this method to calculate the position of the communication device (frequency-converted tag). The measured maximum peak signal of the communication device intermediate signal is displayed at 1 / T Hz intervals, so it is not the exact F_r+f_m. The exact F_r+f_m can be found by finding the center frequency of the sinc function. In Figure 7, the peak error frequency is labeled df.

[0033] To solve this problem and achieve more accurate positioning, the present invention utilizes the spectral leakage characteristics of the discrete Fourier transform (DFT) of a time-limited signal. The DFT of a signal with period T and frequency F_r shows peaks at multiples of 1 / T Hz, and the envelope of this spectral leakage is a sinc function centered on F_r (i.e., TSinc(pi*T(f-fr))). Therefore, to accurately identify F_r, the envelope sinc function must be accurately identified. To achieve this, the position tracking method zero-pads a signal with duration T in the time domain to a magnitude of T_pad. This is a sinc interpolation method in the frequency domain. As shown in Figures 8(c)-(e), the center of the sinc function is located at F_r. As a result, given the sinc interpolation result as shown in Figure 8(e), F_r is determined as the frequency with the maximum peak amplitude. The computational complexity of the overall location tracking method is O(NlogN), where N is the number of samples, and the computational complexity is the same as that of FFT. That is, the location tracking method achieves high accuracy while maintaining the complexity of the existing FMCW, which requires FFT.

[0034] 8 is a diagram illustrating the signal processing sequence for a frequency-converted tag signal received by an FMCW radar according to the present invention. (a) After f_m is identified and removed in real time at the intermediate frequency IF, (b) an IFFT (Inverse Fast Fourier Transform) is applied to the separated signal, leaving only F_r (including spectral leakage). (c) In the time domain of the signal resulting from the IFFT, (d) a signal fragment of duration T is zero-padded. Then, (e) an FFT (Fast Fourier Transform) is performed to obtain an envelope sinc function, and F_r is calculated as the frequency of the maximum peak amplitude.

[0035] 9 is a conceptual diagram showing how the distances of multiple frequency-converted tags from the FMCW radar are measured using the FMCW radar and multiple frequency-converted tags. The signals of each tag (frequency-converted tag, communication device) have different distance frequencies F_r and modulation frequencies f_m, and the intermediate signals IF are expressed as different frequencies F_r+f_m.

[0036] An FMCW radar is equipped with a wide-area receiver (wide-area receiving antenna) and can simultaneously measure the precise location of tags, which are expressed independently at different frequencies depending on their distance and modulation frequency, by analyzing multiple different tag intermediate signals IF in the frequency domain. This is illustrated in Figure 9. The distance frequency F_r is determined by the physical distance between the tag and the FMCW radar, and each tag is frequency-modulated with a different modulation frequency f_m to distinguish the tags and measure their distance.

[0037] Figure 10 shows graphs and photographs of the measurement of the positions of multiple tags on a plane using the FMCW radar of the present invention and multiple frequency-converted tags. The tag positions were measured very accurately. The results are not shown by scanning each tag individually, but by simultaneously transmitting a reflected wave from multiple tags arranged in a two-dimensional array in response to the FMCW radar's transmitted signal. The transmitted wave is then received by the wide-area receiver of the FMCW radar, converted to an intermediate frequency, and each tag is simultaneously recognized in the frequency domain. The distance is then calculated using the method described above.

[0038] 11 is a graph showing the results of calculating the sinc function of the tag signal received from each frequency-converted tag to measure the position of multiple tags on a plane using the FMCW radar and multiple frequency-converted tags of the present invention. The distance frequency of each tag can be accurately measured using the center frequency of the sinc function, and the precise distance between the radar and the tag can be calculated.

[0039] The method for tracking the location of a communication device (tag, frequency conversion tag) of the present invention can simultaneously track the location of mobile communication devices, even if the device is fixed to a single FMCW transmitter transmission. This is possible only if each communication device is configured to generate a different modulation frequency f_m. The different modulation frequencies f_m also function as IDs (identification characters) that distinguish the communication devices.

[0040] That is, the period 1 / f_m of the modulation frequency of each communication device is set to be distinct from the period T of the FMCW radar transmission signal s(t). As a result, each communication device can be effectively separated from clutter as shown in FIG. 6 and represented as a distinct frequency peak that does not overlap with each other as shown in FIG. 11. The location tracking method acquires communication device signals having different FSK frequencies returned from multiple communication devices using a wide-area receiver and analyzes the intermediate signal IF in the frequency domain to determine the precise locations of the communication devices, which are represented independently by different frequencies depending on the distance and modulation frequency in the frequency domain. The f_m of each communication device can be set to a frequency interval corresponding to the frequency to allow for frequency errors in the crystal oscillators used. Each f_m can include any frequency that is not an integer multiple of 1 / T Hz, and its value can be lower or higher than 1 / T Hz.

[0041] FIG. 12 illustrates the use of an FMCW radar and two frequency conversion tags according to the present invention, with a frequency conversion tag attached to a moving object and a frequency conversion tag attached to a stationary object. Unlike a fixed communication device, a mobile communication device induces a Doppler frequency f_d and a time-varying distance frequency F_r(t). The Doppler frequency f_d is added to f_m due to the movement of the communication device. f_d is essentially an intermediate frequency (IF) signal that operates in the same manner as f_m, but is displayed as a distance from the 1 / T Hz integer multiple peak by an amount f_m+f_d instead of f_m. This can be easily removed by measuring the distance from the 1 / T Hz integer multiple peak and shifting the IF signal in the negative direction by that frequency, similar to the f_m removal method described above. Meanwhile, the time-varying distance frequency F_r(t) induces frequency dispersion of the peak, as shown in FIG. 13(b).

[0042] A fixed frequency conversion tag does not have a variable f_d, so there is no frequency dispersion as shown in Figure 13(a). This can be used to distinguish between moving tags and fixed tags. The frequency dispersion increases as the communication device moves faster. A location tracking method can track F_r(t) with accuracy of less than 1 cm through fine-grained time analysis. Mobile communication device positioning can distinguish between mobile and stationary communication devices based on frequency dispersion, which is proportional to the communication device's velocity. For sub-cm location tracking, a mobile communication device is defined as having movement of >1 cm within the duration of the FMCW radar transmission signal s(t), which is a peak with a frequency dispersion of 1.4 Hz or greater.

[0043] The location tracking of a mobile communication device is basically the same as the design principle of fixed communication device positioning, by removing the mobile communication device signal f_m and performing IFFT (Fig. 8(a)-(c)), and then reconstructing the distance frequency (i.e., F_r(t)) in the time domain. That is, in Fig. 8(c), each signal fragment (duration T) of F_r(t) indicates the location at the corresponding time, and zero padding is performed to indicate the accurate location at that time (Fig. 8(d) and (e)). The FMCW radar of the present invention can be used to observe the frequency distribution of each of the multiple tag peaks to determine whether the tag is moving or stationary.

[0044] It is also possible to measure the tag's moving speed by measuring the magnitude of frequency dispersion. To precisely track the position of a moving tag, the same location recognition process as for a fixed tag is performed. However, in this case, to precisely restore the tag's position change over time, IFFT can be performed, including the tag peak, spectral leakage, and its frequency dispersion.

[0045] 14 is an explanatory diagram showing the case where a frequency-converting tag is fixed to a moving object and the case where a frequency-converting tag is fixed to a stationary object using the FMCW radar and multiple frequency-converting tags of the present invention. In a situation consisting of multiple moving tags and fixed tags, each tag is classified as moving or fixed, and then location recognition is performed appropriately according to the classification. In this case, the wide-area receiving unit of the FMCW radar can simultaneously measure the locations of multiple moving tags and fixed tags.

[0046] 15 is an explanatory diagram showing transmitted and received signals when measuring the distance between the FMCW radar and one frequency conversion tag using the FMCW radar of the present invention and one frequency conversion tag. By using one FMCW radar, one-dimensional distance can be measured.

[0047] Figure 16 shows an embodiment for detecting the position of a frequency-converted tag in 2D or 3D space. Using two or more FMCW radars, the position of the tag on a plane or in space can be calculated. To achieve this, a master FMCW radar and a slave FMCW radar are provided, and each radar transmits its measured distance to the tag to the master FMCW radar to determine the tag's position on a plane or in space.

[0048] FIG. 17 shows another embodiment for detecting the position of a frequency-converted tag in 2D or 3D space. This method does not distinguish between master and slave FMCW radars, but instead uses a separate position calculation controller to calculate the tag's position. Each radar is connected to a controller, such as a mini PC or Raspberry Pi, that can post-process and transmit / receive radar information. The controller transmits radar IF signals or distance information measured by each tag to the position calculation controller via wired or wireless communication and can receive instructions from the position calculation controller to change the continuous chirp signal settings (length per chirp and total number of chirps). The position calculation controller uses the information received from the radar to display or store the position information and can instruct the continuous chirp signal settings to be changed depending on environmental changes.

[0049] FIG. 18 shows another embodiment of the present invention for simultaneously detecting fixed and moving frequency conversion tags in 2D or 3D space. This diagram illustrates that the same method can be used to determine the location of both fixed and fixed tags, regardless of whether the tag is located on a plane or in space. Tags moving in space can also be measured because frequency dispersion is measured. Using multiple radars for trilateration allows for simultaneous location tracking of multiple tags, both fixed and moving. Moving tags are affected by different Doppler frequencies f_d for each radar depending on the direction of movement. To address this, each radar can set the modulation frequency f_m and distance frequency F_r interval for each tag to correspond to the maximum Doppler frequency. [Explanation of symbols]

[0050] 100 Communication equipment positioning system using FMCW radar 200 FMCW radar 210 Chirp Signal Generator 220 Signal Separator 230 transmitting antenna 240 receiving antenna 250 signal mixer 260 Distance or Position Measurement Algorithms 300 Communication device (frequency conversion tag) 310 Transmitting and receiving antenna 320 Modulation section [Industrial Applicability]

[0051] The present invention is an industrially applicable technique as a method for determining the position of a communication device using communication technology.

Claims

1. Using FMCW radar and frequency modulation tags, a tag signal, which is an intermediate signal of the reflected wave obtained by transmitting a continuous chirp signal from the FMCW radar and simultaneously calculating an intermediate signal IF, which is the difference in frequency between the received signals; the tag signal, which is an intermediate signal of the reflected wave obtained by transmitting the continuous chirp signal from a frequency-modulated tag, is the sum of a modulation frequency f_m and a distance frequency F_r, which indicates distance due to time shift; and to calculate the modulation frequency f_m of the tag signal from the FMCW radar, the method includes subtracting the frequency of the nearest surrounding reflected signal that is smaller than the maximum peak frequency from the maximum peak frequency of the tag signal modulated by the frequency-modulated tag, which is located among surrounding reflected signals located at integer multiples of the reciprocal frequency of a unit chirp time length in the frequency domain.

2. Using FMCW radar and frequency modulation tags, A method for calculating a distance frequency indicating the distance between the FMCW radar and a frequency-modulated tag from a tag signal transmitted by the frequency-modulated tag, the method comprising: demodulating a sinc function of the tag signal received by the frequency-modulated tag using a modulation frequency spectrum leakage feature value of the tag signal received by the frequency-modulated tag that does not overlap with the periodically located surrounding reflected signal frequencies, centered on a maximum peak frequency of the signal modulated by the frequency-modulated tag that is located between the periodically located surrounding reflected signal frequencies in the frequency domain; and calculating the distance frequency by subtracting the modulation frequency from the center frequency of the demodulated sinc function.

3. Using FMCW radar and frequency modulation tags, In the method for measuring the distance between the FMCW radar and the frequency modulation tag, generating a radar transmission signal by the FMCW radar; a counter-transmission step of receiving the radar transmission signal generated in the radar transmission signal generating step by using a tag receiving antenna provided in the frequency modulation tag, modulating the frequency by f_m in a modulation unit provided in the frequency modulation tag, and transmitting the modulated signal from a tag transmitting antenna of the frequency modulation tag; a signal receiving step of receiving the modulated signal transmitted in the counter-transmission step by a receiving antenna provided in the FMCW radar; a reception frequency pre-processing step of generating an intermediate signal by mixing the frequency transmitted from the FMCW radar with a received frequency to calculate the sum of a distance frequency, which is a frequency difference between the frequency transmitted from the FMCW radar and the frequency received in the signal receiving step, and a modulation frequency; a frequency domain conversion step of converting the intermediate signal generated in the reception frequency pre-processing step into a frequency domain; a separation frequency confirmation step of confirming periodically located peripheral reflected signal frequencies and tag signals modulated by the frequency modulation tag in the intermediate signal in the frequency domain converted in the frequency domain conversion step; A method for determining the location of a communication device using an FMCW radar, comprising: calculating the modulation frequency f_m by subtracting the frequency of the most adjacent peripheral reflected signal, among the periodically positioned peripheral reflected signals, that is lower than the maximum peak frequency of the tag signal modulated by the frequency-modulated tag.

4. Using FMCW radar and frequency modulation tags, In the method for measuring the distance between the FMCW radar and the frequency modulation tag, generating a radar transmission signal by the FMCW radar; a counter-transmission step of receiving the radar transmission signal generated in the radar transmission signal generating step by using a tag receiving antenna provided in the frequency modulation tag, modulating the frequency by f_m in a modulation unit provided in the frequency modulation tag, and transmitting the modulated signal from a tag transmitting antenna of the frequency modulation tag; a signal receiving step of receiving the modulated signal transmitted in the counter-transmission step by a receiving antenna provided in the FMCW radar; a reception frequency pre-processing step of generating an intermediate signal by mixing the frequency transmitted from the FMCW radar with a received frequency to calculate the sum of a distance frequency, which is a frequency difference between the frequency transmitted from the FMCW radar and the frequency received in the signal receiving step, and a modulation frequency; a frequency domain conversion step of converting the intermediate signal generated in the reception frequency pre-processing step into a frequency domain; a separation frequency confirmation step of confirming the periodically located surrounding reflected signal frequencies in the intermediate signal in the frequency domain converted in the frequency domain conversion step and the tag signal modulated by the frequency modulation tag; A method for determining the location of a communication device using an FMCW radar, comprising: demodulating a sinc function of a signal received by the frequency-modulated tag using a modulation frequency spectrum leakage feature value of the signal received by the frequency-modulated tag that does not overlap with the periodically located surrounding reflected signal frequencies, centered on the maximum peak frequency of the tag signal modulated by the frequency-modulated tag, in the frequency domain; and calculating the center frequency of the demodulated sinc function as the sum of the distance frequency and the modulation frequency.

5. A method for measuring the position of a communication device using an FMCW radar as described in any one of claims 1 to 4, characterized in that in the frequency domain, the value obtained by subtracting the modulation frequency f_m from the center frequency is calculated using a distance frequency F_r indicating the distance.

6. 5. The method for determining the position of a communication device using an FMCW radar according to claim 1, wherein the radar signal generated by the FMCW radar is one of a periodically repeated signal of two or more continuous chirp signals, an intermittently periodically repeated signal of two or more continuous chirp signals, a discontinuously periodically repeated signal of two or more chirp signals, and a discontinuously intermittently periodically repeated signal of two or more chirp signals.

7. The method for measuring the position of a communication device using an FMCW radar according to claim 5, characterized in that the inverse of F_r is calculated by the time delay due to distance and multiplied by the speed of light to calculate the distance between the FMCW radar and the frequency modulation tag.

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