Tag, interrogator, and system for performing position measurement based on backscatter in millimeter-wave band

1 . A tag for performing position measurement based on backscatter in a millimeter-wave band, the tag comprising:

a planar Van Atta array antenna;

a frequency-shift keying (FSK) modulator connected to the planar Van Atta array antenna; and

at least one bias circuit connected to the FSK modulator,

wherein the FSK modulator is configured to:

based on an interrogation signal being received by the planar Van Atta array antenna, modulate the interrogation signal based on a control signal supplied through the at least one bias circuit; and

output the modulated interrogation signal in a direction from which the interrogation signal is received, through the planar Van Atta array antenna,

wherein an incident signal received by an upper antenna is output from a lower antenna of a centrosymmetric antenna pair in the planar Van Atta array antenna,

wherein the FSK modulator comprises a 90° hybrid coupler, the 90° hybrid coupler being configured to deliver the interrogation signal through a first path, a second path, a third path, and a fourth path,

wherein, among the interrogation signal, a first signal delivered through the first path and a second signal delivered through the second path are induced to undergo a 180° phase shift with respect to each other to offset each other, and

wherein, among the interrogation signal, a third signal delivered through the third path and a fourth signal delivered through the fourth path, having no phase difference therebetween, are summed up to a maximum and output.

2 . The tag of claim 1 , wherein the FSK modulator is further configured to perform FSK modulation by inducing periodic 180° shifts of a phase of the interrogation signal.

3 . The tag of claim 1 , wherein the FSK modulator further comprises:

a reflective network connected to the 90° hybrid coupler and comprising a plurality of PIN diodes.

4 . The tag of claim 1 , further comprising a radio-frequency (RF) choke arranged between the at least one bias circuit and the planar Van Atta array antenna to prevent leakage of the interrogation signal received by the planar Van Atta array antenna.

5 . The tag of claim 1 , wherein the interrogation signal comprises continuous unit chirp signals that change from a first frequency to a second frequency.

6 . The tag of claim 1 , wherein the planar Van Atta array antenna comprises a plurality of antenna elements,

the plurality of antenna elements comprise centrosymmetric antenna element pairs for retroreflection, and

a first antenna element and a second antenna element included in each of the antenna element pairs are connected to transmission lines having a length difference equal to multiples of length λ g of a guided wavelength of the interrogation signal.

7 . An interrogator for performing position measurement based on backscatter in a millimeter-wave band, the interrogator comprising:

a transceiver; and

at least one processor connected to the transceiver, wherein the at least one processor is configured to:

output an interrogation signal including continuous unit chirp signals that change from a first frequency to a second frequency;

receive a backscattered tag signal from a tag that has received the output interrogation signal; and

measure a position of the tag by isolating the tag signal and identifying frequency-shift keying (FSK) modulation applied to the backscattered tag signal,

wherein the tag comprises a frequency-shift keying (FSK) modulator connected to a planar Van Atta array antenna,

wherein an incident signal received by an upper antenna may be output from a lower antenna of a centrosymmetric antenna pair in the planar Van Atta array antenna,

wherein the FSK modulator comprises a 90° hybrid coupler, the 90° hybrid coupler being configured to deliver the interrogation signal through a first path, a second path, a third path, and a fourth path,

wherein, among the interrogation signal, a first signal delivered through the first path and a second signal delivered through the second path are induced to undergo a 180° phase shift with respect to each other to offset each other, and

wherein, among the interrogation signal, a third signal delivered through the third path and a fourth signal delivered through the fourth path, having no phase difference therebetween, are summed up to a maximum and output.

8 . The interrogator of claim 7 , wherein the interrogation signal belongs to a millimeter-wave band.

9 . The interrogator of claim 7 , wherein the at least one processor is further configured to:

mix the interrogation signal with the tag signal to generate an intermediate signal; and

perform a fast Fourier transform (FFT) on the intermediate signal.

10 . A system for performing position measurement based on backscatter in a millimeter-wave band, the system comprising:

an interrogator configured to output an interrogation signal including continuous unit chirp signals that change from a first frequency to a second frequency; and

a tag configured to receive the interrogation signal, apply frequency-shift keying (FSK) modulation to the interrogation signal, and transmit a tag signal to which the FSK modulation is applied, in a direction from which the interrogation signal is incident,

wherein the interrogator is further configured to measure a position of the tag by identifying the FSK modulation applied to the tag signal,

wherein the tag comprises a frequency-shift keying (FSK) modulator connected to a planar Van Atta array antenna,

wherein an incident signal received by an upper antenna may be output from a lower antenna of a centrosymmetric antenna pair in the planar Van Atta array antenna,

wherein the FSK modulator comprises a 90° hybrid coupler, the 90° hybrid coupler being configured to deliver the interrogation signal through a first path, a second path, a third path, and a fourth path,

wherein, among the interrogation signal, a first signal delivered through the first path and a second signal delivered through the second path are induced to undergo a 180° phase shift with respect to each other to offset each other, and

wherein, among the interrogation signal, a third signal delivered through the third path and a fourth signal delivered through the fourth path, having no phase difference therebetween, are summed up to a maximum and output.

11 . The system of claim 10 , wherein the interrogation signal belongs to a millimeter-wave band.

12 . The system of claim 10 , wherein the interrogator is further configured to:

mix the interrogation signal with the tag signal to generate an intermediate signal; and

perform a fast Fourier transform (FFT) on the intermediate signal.