KR101358904B1 - Amplitude modulated radar, apparatus and method for reducing a distance measurement error of the same - Google Patents

Abstract

The present invention relates to an amplitude modulated radar, an apparatus and a method for reducing distance measurement error of the amplitude modulated radar. Provided is an amplitude modulated radar including: an amplitude modulated signal transmission unit which generates an amplitude modulated signal by synthesizing a modulation frequency signal and a carrier frequency signal, and transmits the generated amplitude modulation signal to a target; a detector which detects a radio signal including the amplitude modulation signal reflected and received from the target; a phase detection unit which generates phase retardation data by detecting phase retardation between the radio signal detected by the detector and the modulation frequency signal; a demodulation unit which demodulates the radio signal to an I/Q signal by using the carrier frequency signal; and a signal processing unit which samples the phase retardation data by using the I/Q signal, and calculates distance information of the target by using the sampled phase retardation data. [Reference numerals] (113) Power attenuator; (120) Detector; (130) Phase detection unit; (142) Low pass filter; (150) Signal processing unit; (160) Analog-digital converter; (190) Power distributer

Description

AMPLITUDE MODULATED RADAR, APPARATUS AND METHOD FOR REDUCING A DISTANCE MEASUREMENT ERROR OF THE SAME}

The present invention relates to an amplitude modulated radar, an apparatus for reducing a distance measurement error of an amplitude modulated radar, and a method for reducing a distance measurement error of an amplitude modulated radar.

Radio Detection And Ranging (RADAR) is a wireless device that transmits radio waves and receives reflected waves reflected back from targets and detects the distance, speed, etc. to the targets. It has been used for a purpose, and in recent years has been widely used in the field of vehicle collision prevention, biological signal detection and the like. The radar includes a pulse radar, a frequency modulated continuous wave (FMCW) radar, an amplitude modulated (AM) radar, and the like. Among them, pulse radar and FMCW radar are limited in frequency bandwidth because they are not allowed to use wide frequency band due to the recent frequency regulation, and it is difficult to increase the accuracy of distance measurement. You will not get the accuracy of the distance measurement.

The amplitude modulation radar transmits a carrier wave at a modulation frequency to a target (target), and detects the phase of the envelope signal reflected from the target object and returns to the receiver, and measures the distance of the target, compared with other radar systems. Narrow frequency bandwidth can be used to increase the accuracy of distance measurements on targets. However, in the case of an amplitude modulation radar, a ripple error may occur due to a signal leaking from a transmitter to a receiver. If the distance between the transmitter and the receiver is increased to increase the isolation, an error may be reduced, but the size of the radar is inevitably increased.

An object of the present invention is to provide an amplitude modulation radar and an apparatus and method for reducing the distance measurement error of an amplitude modulation radar capable of reducing the distance measurement error of a target.

In addition, an object of the present invention is to provide an amplitude modulation radar and an apparatus and method for reducing a distance measurement error of an amplitude modulated radar, even when using a narrow bandwidth.

In addition, an object of the present invention is to reduce the distance measurement error of the target by canceling the ripple error caused by the leakage signal from the transmitting end to the receiving end of the amplitude modulation radar.

The problems to be solved by the present invention are not limited to the above-mentioned problems. Other technical subjects not mentioned may be clearly understood by those skilled in the art from the following description.

An amplitude modulation radar according to an aspect of the present invention comprises: an amplitude modulation signal transmitter for synthesizing a modulation frequency signal and a carrier frequency signal to generate an amplitude modulation signal, and transmitting the generated amplitude modulation signal to a target; A detector for detecting a wireless signal including an amplitude modulated signal reflected from the target; A phase detector configured to detect phase delay between the radio signal detected by the detector and the modulation frequency signal to generate phase delay data; A demodulator for demodulating the radio signal into an I / Q signal using the carrier frequency signal; And a signal processor configured to sample the phase delay data using the I / Q signal and calculate distance information of the target using the sampled phase delay data.

According to an aspect of the invention, the demodulation unit, I / Q demodulator for demodulating the radio signal into the I / Q signal using the carrier frequency signal; And a low pass filter for removing high frequency signals from the demodulated I / Q signals.

According to an aspect of the present invention, the I / Q demodulator demodulates the radio signal using the carrier frequency signal to generate an I-channel signal and a Q-channel signal, thereby converting the radio signal into the I / Q. Demodulate to signal.

According to an aspect of the present invention, the signal processing unit samples N phase delay data corresponding to N phases (N is an integer of 2 or more) on an I / Q plane by using phase information of the I / Q signal. An average value of the sampled N phase delay data is calculated, and the distance information of the target is calculated based on the average value.

According to an aspect of the present invention, the signal processing unit has a phase of the I / Q signal is θ ₀ + 2πk / N (k = 0,1, .., N-1) on the I / Q plane, where N is 2 The above integer, θ ₀ , samples the N phase delay data having a value of a predetermined reference phase value.

According to an aspect of the present invention, the signal processing unit calculates an average value of the current sampled phase delay data and the previous N-1 phase delay data each time the phase delay data is sampled, and based on the average value. To calculate the distance information.

According to an aspect of the present invention, the signal processing unit calculates a phase change of two adjacent phase delay data from information indicating the Doppler shift of the I / Q signal, and additionally reflects a value corresponding to the phase change to the average value. By this, distance information of the target with respect to the unsampled phase delay data is calculated.

According to an aspect of the present invention, the amplitude modulation radar further includes an analog-to-digital converter for converting the phase delay data and the I / Q signal to a digital signal to transmit to the signal processor.

According to an aspect of the present invention, the phase detector detects the phase delay between the envelope of the radio signal detected by the detector and the modulation frequency signal.

According to an aspect of the invention, the amplitude modulation radar comprises a receiving antenna for receiving the radio signal; A low noise amplifier for amplifying the received wireless signal; And a power divider for distributing and amplifying the amplified radio signal to the detector and the demodulator.

An apparatus for reducing a distance measurement error of an amplitude modulation radar according to another aspect of the present invention demodulates a radio signal including an amplitude modulation signal received by being reflected from a target into an I / Q signal using a carrier frequency signal of the amplitude modulation signal. A demodulation unit; And a signal processor configured to sample data corresponding to the signal detected from the radio signal by using the I / Q signal, and calculate distance information of the target by using the sampled data.

According to another aspect of the present invention, the signal processing unit samples the data corresponding to the phase delay between the signal detected from the radio signal and the modulation frequency signal of the amplitude modulated signal using the I / Q signal.

According to another aspect of the invention, the signal processing unit, using the phase information of the I / Q signal, N data corresponding to a predetermined N phase (N is an integer of 2 or more) on the I / Q plane Sampling, calculating an average value of the sampled N data, and calculating distance information of the target based on the average value.

According to another aspect of the invention, the signal processing unit is the phase of the I / Q signal in the I / Q plane θ ₀ + 2πk / N (k = 0, 1, ..., N-1) (N is An integer of 2 or more, θ ₀ samples the N pieces of data having a value of a predetermined reference phase value).

According to another aspect of the present invention, the signal processor calculates a phase change of two adjacent phase delay data from information indicating Doppler shift of the I / Q signal, and adds a value corresponding to the phase change to the average value. By reflecting, distance information of the target with respect to unsampled phase delay data is calculated.

According to another aspect of the present invention, a method for reducing a distance measurement error of an amplitude modulation radar includes converting a radio signal including an amplitude modulation signal received from a target into an I / Q signal using a carrier frequency signal of the amplitude modulation signal. Demodulating; Sampling data corresponding to a signal detected from the wireless signal using the I / Q signal; And calculating distance information of the target by using the sampled data.

According to another aspect of the invention, the step of sampling, the phase delay data corresponding to the phase delay between the signal detected from the radio signal and the modulation frequency signal of the amplitude modulation signal using the I / Q signal Sampling.

According to another aspect of the present invention, the sampling comprises sampling N pieces of data corresponding to N phases (N is an integer of 2 or more) on an I / Q plane using phase information of the I / Q signal. The calculating of the distance information may include calculating an average value of the N pieces of data sampled; And calculating distance information of the target based on the average value.

According to another aspect of the present invention, the sampling may include the phase of the I / Q signal being θ ₀ + 2πk / N on the I / Q plane (k = 0,1, .. N-1) ( N is an integer of 2 or more, and θ ₀ is a predetermined reference phase value).

According to another aspect of the invention, the method for reducing the distance measurement error of the amplitude modulation radar calculates the phase change of two adjacent data from the information indicating the Doppler shift of the I / Q signal, and the average value to the phase change The method further includes calculating distance information of the target with respect to the unsampled data by further reflecting the corresponding value.

According to the embodiment of the present invention, it is possible to provide an amplitude modulation radar and an apparatus and method for reducing the distance measurement error of the amplitude modulation radar which can reduce the distance measurement error of the target.

Further, according to the embodiment of the present invention, even when using a narrow bandwidth, it is possible to improve the distance measurement accuracy.

In addition, according to an embodiment of the present invention, the ripple error caused by the leakage signal from the transmitting end to the receiving end of the amplitude modulation radar can be canceled to reduce the distance measurement error of the target.

1 is a block diagram of an amplitude modulation radar according to an embodiment of the present invention.
2 is a flowchart illustrating a method for reducing a distance measurement error of an amplitude modulation radar according to an embodiment of the present invention.
3 is a graph illustrating a change in phase delay according to movement of a target.
Figure 4 shows a distance measurement graph of the target according to the prior art.
FIG. 5 is a conceptual diagram for describing step S25 of FIG. 2.
6 is a graph illustrating a change in distance of a target according to an output phase of a phase detector.
FIG. 7 is an enlarged view of a portion 'A' and a portion 'B' illustrated in FIG. 6.
8 is a graph illustrating a distance of a target by sampling phase delay data according to an exemplary embodiment of the present invention.
FIG. 9 is an enlarged view of a portion 'C' shown in FIG. 8.
FIG. 10 is a diagram for explaining step S27 of FIG. 2.
11 is a graph showing the measurement of the distance of the target according to an embodiment of the present invention.

Other advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Unless defined otherwise, all terms (including technical or scientific terms) used herein have the same meaning as commonly accepted by the generic art in the prior art to which this invention belongs. Terms defined by generic dictionaries may be interpreted to have the same meaning as in the related art and / or in the text of this application, and may be conceptualized or overly formalized, even if not expressly defined herein I will not. The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention.

In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the phrase "comprises" and various usages of the verb does not exclude the presence or addition of one or more other components, steps, operations and / or elements. The term 'and / or' as used herein refers to each of the listed configurations or various combinations thereof. Meanwhile, the terms '~' and '~' used throughout the present specification may mean a unit that processes at least one function or operation. For example, a hardware component, such as a software, FPGA, or ASIC. However, '~' and '~' are not meant to be limited to software or hardware. '~', '~' May be configured to reside in an addressable storage medium or may be configured to play one or more processors. Thus, as an example, 'part', '~' means components such as software components, object-oriented software components, class components, and task components, and processes, functions, and properties. Fields, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. Components and functions provided within '~', '~' may be combined into smaller number of components and '~', '~', or additional components, '~', '~' Can be further separated.

An amplitude modulation radar according to an embodiment of the present invention demodulates an amplitude modulation signal into an I / Q signal using a carrier frequency signal of an amplitude modulation signal, and outputs data corresponding to a phase delay obtained by detecting an amplitude modulation signal. Sampling is performed using the signal, and distance information of the target is calculated using the sampled data. Accordingly, the distance measurement error of the amplitude modulation radar can be reduced.

1 is a block diagram of an amplitude modulation radar according to an embodiment of the present invention. Referring to FIG. 1, an amplitude modulation radar 100 according to an embodiment of the present invention includes an amplitude modulated signal transmitter 110, a detector 120, a phase detector 130, a demodulator 140, and a signal processor 150. ), An analog-to-digital converter 160, a receive antenna 170, a low noise amplifier 180, and a power divider 190.

The amplitude modulation signal transmitter 110 synthesizes a modulation frequency signal and a carrier frequency signal to generate an amplitude modulation signal, and transmits the generated amplitude modulation signal to a target. In one embodiment, the amplitude modulated signal transmitter 110 includes a modulated frequency signal generator 111, a carrier frequency signal generator 112, a power attenuator 113, a mixer 114, an amplifier 115, and a transmit antenna 116. ).

The modulation frequency signal generator 111 generates a modulation frequency signal. Modulation frequency (modulation frequency) means the frequency of the signal wave for modulation. In one embodiment, the modulation frequency signal generator 111 may include a local oscillator for generating a signal of a modulation frequency corresponding to a frequency lower than the carrier frequency. If there are several targets to be measured, it is also possible to measure the distance using signals of different modulation frequencies for each target. The modulation frequency signal generated by the modulation frequency signal generator 111 is input to the power attenuator 113 for amplitude modulation, and to the phase detector 130 for distance measurement with a target.

The carrier frequency signal generator 112 generates a carrier frequency signal. The carrier frequency refers to a frequency of a high frequency (carrier) when modulating and transmitting a high frequency with a constant frequency by a signal wave. In other words, the carrier frequency may refer to a reference frequency used for this modulation when a signal occupying a specific frequency band is modulated into a carrier frequency band which is easily transmitted by a transmission medium. The carrier frequency (e.g., 2.44 GHz) may be the main file higher than the modulation frequency (e.g., 40 MHz). In one embodiment, the carrier frequency signal generator 112 may include a radio frequency (RF) local oscillator for generating a signal of a carrier frequency corresponding to a frequency higher than the modulation frequency.

The carrier frequency signal generated by the carrier frequency signal generator 112 is input to the mixer 114 for synthesis with the amplitude modulated modulated frequency signal and to the demodulator 140 for reducing the distance measurement error of the target. do.

The power attenuator 113 adjusts the amplitude of the modulation frequency signal. The modulated frequency signal amplitude modulated by the power attenuator 113 is input to the mixer 114 for synthesis with the carrier frequency signal. The mixer 114 mixes (synthesizes) an amplitude modulated modulation frequency signal and a carrier frequency signal. The amplifier 115 amplifies the amplitude modulated signal mixed by the mixer 114. The transmit antenna 116 transmits the amplitude modulated signal amplified by the amplifier 115 to the target. For example, the amplitude modulation signal is a bilateral band frequency f generated by mixing a signal of a fixed carrier frequency f ₀ , a signal of carrier frequency f ₀ and a signal of amplitude modulated modulation frequency f _m . ₀ ± f _m ).

The amplitude modulated signal reflected from the target returns to the receiving antenna 170. The receiving antenna 170 receives a radio signal including an amplitude modulated signal reflected from the target and returned. In the embodiment of FIG. 1, the transmitting antenna 116 and the receiving antenna 170 are separated, but according to another embodiment, the transmitting antenna 116 and the receiving antenna 170 may be provided in one module. In this case, Elements such as a circulator or a hybrid coupler may be provided to separate the transmission signal and the reception signal.

The low noise amplifier 180 amplifies the wireless signal received through the reception antenna 170. The power divider 190 distributes and outputs the wireless signal amplified by the low noise amplifier 180 to the detector 120 and the demodulator 140. The detector 120 detects a wireless signal including an amplitude modulated signal. In one embodiment, detector 120 includes an envelope detector that detects an envelope of a wireless signal. Alternatively, the detector 120 may detect the wireless signal using a synchronous detection scheme or the like.

The phase detector 130 detects a phase delay between the radio signal detected by the detector 120 and the modulation frequency signal. For example, when an envelope detector is used as the detector 120, the phase detector 130 may detect a phase delay from a difference value between a phase of the detected envelope signal and a phase of a modulation frequency signal. In one embodiment, the phase detector 130 may include a phase meter for detecting a phase difference between two signals.

The demodulator 140 demodulates a radio signal into an I / Q signal using a carrier frequency signal. The I / Q signal demodulated by the demodulator 140 includes information on the Doppler effect and is then input to the signal processor 150 to be used to reduce the distance measurement error of the amplitude modulation radar.

In one embodiment, the demodulator 140 may be implemented as a direct conversion demodulator. The demodulator 140 may include an I / Q demodulator 141 and a low pass filter 142. The I / Q demodulator 141 may demodulate the radio signal into an I / Q signal by generating an I-channel signal and a Q-channel signal from the radio signal using a carrier frequency signal. . The low pass filter 142 removes the high frequency signal from the demodulated I / Q signal. The analog-to-digital converter 160 converts analog data corresponding to the phase delay output from the phase detector 130 and analog I / Q signals output from the demodulator 140 into digital signals and transmits them to the signal processor 150. do.

The signal processor 150 samples the data corresponding to the phase delay using the I / Q signal from the demodulator 140, and calculates distance information of the target using the sampled data. In one embodiment, the signal processor 150 samples a predetermined number of data using the phase information on the I / Q plane of the I / Q signal, calculates an average value of the sampled data, and then calculates an average value of the sampled data. Based on the distance information of the target can be calculated. More specific functions and operations of the signal processor 150 will be described later.

2 is a flowchart illustrating a method for reducing a distance measurement error of an amplitude modulation radar according to an embodiment of the present invention. The steps of configuring the embodiment of FIG. 2 may be performed by the configurations of the embodiment of FIG. 1. 1 and 2, in step S21, the amplitude modulated signal transmitter 110 transmits an amplitude modulated signal to a target. The amplitude modulated signal transmitter 110 amplitude-modulates the modulated frequency signal generated by the modulated frequency signal generator 111 using the power attenuator 113, and modulates the modulated frequency signal and the carrier frequency signal generator 112 that are amplitude modulated. Carrier frequency signal generated by the can be synthesized using the mixer 114. The amplitude modulated signal transmitter 110 may generate an amplitude modulated signal as shown in Equation 1 below by amplifying the signal synthesized using the mixer 114 using the amplifier 115. The amplitude modulated signal generated by the amplitude modulated signal transmitter 110 is transmitted to the target through the transmit antenna 116.

[Equation 1]

Where T (t) is the amplitude modulation signal, A is the amplification factor of the amplifier 115, M is the amplitude modulation rate of the power attenuator, f _m is the modulation frequency (Hz), and φ _m is the phase (°) of the modulation frequency signal. , f ₀ represents a carrier frequency (Hz), and φ ₀ represents a phase of a carrier frequency signal.

Next, in step S22, the detector 120 detects the radio signal reflected and received from the target. The wireless signal received through the receiving antenna 170 includes an amplitude modulated signal reflected from the target and returned, for example, may be represented by Equation 2 below.

[Equation 2]

Where R (t) is an amplitude modulated signal reflected from the target and returned, B is a constant corresponding to the power of the received amplitude modulated signal, ω _m is 2πf _m (rad / sec) (angular frequency of the modulated frequency signal), d ₀ is the initial distance of the target (m), χ (t) is the distance from the reference distance to the target (m), c is the speed of light (m / sec), and ω ₀ is 2πf ₀ (rad / sec) (carrier Angular frequency of the frequency signal), E (t) represents a leakage signal.

Next, in step S23, the phase detector 130 detects a phase delay between the radio signal detected by the detector 120 and the modulation frequency signal. Since the amplitude modulated signal reflected from the target and returned has a phase delay according to the distance of the target, the phase detector 130 may detect a signal (eg, an envelope signal) detected from the amplitude modulated signal to estimate the distance of the target. The phase difference of the modulation frequency signal is calculated. The phase delay data detected by the phase detector 130 is converted into a digital signal by the analog-digital converter 160 and input to the signal processor 150.

However, as shown in Equation 2 above, in addition to the amplitude modulation signal reflected from the target and returned to the radio signal received by the reception antenna 170, the leakage signal E directly flowing from the transmission antenna 116 to the reception antenna 170. (t) is included. The signal received by the receiving antenna 170 and amplified by the low noise amplifier 180 may be detected by the detector 120 according to square law detection, for example, as shown in Equation 3 below.

[Equation 3]

Here, R _Env (t) is a square-detected signal, α is a constant representing a ratio of a signal transmitted to a target among the signals output from the transmitting antenna, and β is a signal leaked directly to the receiving antenna among the signals output from the transmitting antenna. Constant representing the ratio. Of the three signals of the signal R _Env (t) squarely detected in Equation 3, since the second signal (β ² sinω _m t) has a meaningless DC value at the final stage, no error occurs or is insignificant in phase detection. It only causes a level error. However, the third signal among the square-detected signals may cause a significant error in phase detection. As the third signal according to the leakage signal is demodulated by the detector 120 among the square-detected signals R _Env (t) of Equation 3, an error signal such as Equation 4 below may appear.

[Equation 4]

Here, E _Leak (t) is an error signal due to the leak signal, α is a constant representing the ratio of the signal transmitted to the target among the signals output from the transmitting antenna, β is leaked directly to the receiving antenna of the signal output from the transmitting antenna A constant representing the ratio of the signal, ω _m is the angular frequency (rad / sec) of the modulated frequency signal, χ (t) is the distance (m) over time from the reference position to the target, and c is the speed of light (3 × 10) ⁸ m / sec), ω ₀ represents the angular frequency (rad / sec) of the carrier frequency signal.

3 is a graph illustrating a change in phase delay according to movement of a target. In FIG. 3, the dotted line is an ideal graph virtually showing that the phase delay is measured without generating an error, and the solid line is an exemplary graph showing that an error occurs in the output phase of the phase detector 130. As a part of the amplitude modulation signal is a leakage signal directly input from the transmitting antenna 116 of the amplitude modulation radar to the receiving antenna 170, as shown in FIG. 3, the phase detector 130 according to the movement of the target object. ) Output phase has the ideal graph phase and error.

Figure 4 shows a distance measurement graph of the target according to the prior art. In FIG. 4, the dotted line graph represents the actual distance change over time of the target, and the solid line graph does not sample the phase delay data output from the phase detector, but all phase delay data output from the phase detector according to the prior art. The distance change with time of the target measured from FIG. Referring to FIG. 4, in the prior art, it can be seen that the distance measurement value of the target varies with time from the distance value of the actual target.

Since the angular frequency (ω _m ) of the modulation frequency signal is much smaller than the angular frequency (ω ₀ ) of the carrier frequency signal, the variation of the leakage signal error due to the modulation frequency in Equation 4 is related to the variation of the leakage signal error due to the carrier frequency. In comparison, the degree of change is very small and can be treated as a constant. On the other hand, since the carrier frequency is much larger than the modulation frequency, the error value of the phase delay caused by the fine movement of the target is ultimately dependent on the variable corresponding to the product of the carrier frequency and the distance of the target. Therefore, if the error component is canceled in consideration of the variable corresponding to the product of the carrier frequency corresponding to the high frequency and the distance of the target, the error of the phase delay caused by the leakage signal can be reduced, and thus the ripple error of the distance of the target ( ripple errors can be reduced.

However, in order to cancel the error due to the leak signal, since the distance information of the target must be known in addition to the carrier frequency, it is difficult to cancel the error due to the leak signal in a state where the exact distance information of the target is not known. Since the carrier frequency has a very large value, even if the estimated distance of the target has only a slight error in the distance of the actual target, the error due to the leakage signal may increase. To solve this problem, an embodiment of the present invention utilizes the fact that an I / Q signal demodulated from an amplitude modulated signal using a carrier frequency signal has a variable equal to a product of a carrier frequency of a high frequency and a distance of a target. Sampling allows the error due to leakage signals to be canceled out.

To this end, in step S24, the demodulator 140 demodulates the radio signal including the amplitude modulated signal received by being reflected from the target into an I / Q signal using a carrier frequency signal. For example, the I / Q demodulator 141 generates an I-channel signal and a Q-channel signal from the radio signal using a carrier frequency signal, thereby converting the radio signal into an I / Q signal. It can be demodulated. The demodulated I / Q signal is filtered by the low pass filter 142, and then converted into a digital signal by the analog-to-digital converter 160 and input to the phase detector 130. On the other hand, the above-described step S24 may be performed before or after step S22 and step S23, or may be performed in parallel with step S22 and step S23 simultaneously.

Equations 5 to 6 below represent I-channel signals of digitally converted I / Q signals and Q-channel signals, and Equation 7 represents digitally converted I / Q signals.

[Equation 5]

[Equation 6]

[Equation 7]

Here, R _I (n) represents the signal of the I-channel corresponding to the n-th data, R _q (n) represents the signal of the Q-channel corresponding to the n-th data, and χ (n) represents the n-th data. It represents the distance of the target corresponding to.

Among the I / Q signals demodulated in Equation 7, a phase change occurs using the motion χ [n] of the target and the angular frequency (ω ₀ ) of the carrier frequency signal as variables. At this time, the phase {ω ₀ · 2χ (n) / c} of the I / Q signal in Equation 7 is equal to the sine wave variable {ω ₀ · 2χ (t) / c} at the high frequency of the error signal in Equation 4. Able to know.

As shown in Equation 8 below, the sum of N data corresponding to the phase of 2πi / N (N is an integer of 2 or more, i is 1, .., N) in a sine wave becomes 0, If the phase change of Equation 7 is the same as the variable of Equation 4, the error signal of Equation 4 can be removed even if the distance of the target is not known accurately.

[Equation 8]

To this end, the signal processor 150 samples the data corresponding to the phase delay detected by the phase detector 130 using the phase information of the I / Q signal in step S25.

FIG. 5 is a conceptual diagram for describing step S25 of FIG. 2. 5 (a) shows that the phase of the I / Q signal demodulated by the demodulator 140 changes counterclockwise on the I / Q plane as the target moves away from the initial position with time. If the target has a movement close to the initial position, the phase of the I / Q signal demodulated by the demodulator 140 will change in the clockwise direction on the I / Q plane unlike in FIG. Referring to FIG. 5A, the signal processing unit 150 has a phase of the demodulated I / Q signal in the I / Q plane, θ ₀ + 2πk / N (k = 0,1, .., N-1). Data corresponding to (N is an integer of 2 or more) can be sampled. FIG. 5A shows an example in which the value of θ ₀ is set to 0 ° and the value of N is set to 4, whereby the I / Q signals of the data are S1, S2, Each time it passes through S3 and S4, four phase delay data D1, D2, D3, and D4 are sampled for one period of a sine wave, as shown in FIG. However, the number N of data sampled on the I / Q plane and the reference phase value θ ₀ are not limited to the example shown in FIG. 5.

6 to 11 are diagrams for describing a method for reducing a distance measurement error of a target according to an exemplary embodiment of the present invention.

In the experiment, a copper plate target was used, and the distance of the target was measured in a range of 0.5 to 2.0 m. Sampling data number N was set to eight. FIG. 6 is a graph illustrating a distance change of a target according to an output phase of a phase detector, and it may be seen that a distance measurement error occurs due to a leak signal from a transmitter to a receiver when data is not sampled. FIG. 7A is an enlarged view of part 'A' shown in FIG. 6, and FIG. 7B is an enlarged view of part 'B' shown in FIG. 6. As illustrated in FIG. 7, the signal processor 150 samples only data corresponding to the sampling signals S1, S2, S3, and S4 according to the phase change of the I / Q signal among the data from the phase detector 130. do.

Referring back to FIGS. 1 and 2, in step S26, the signal processor 150 calculates distance information of the target using the sampled data. In one embodiment, the signal processing unit 150 calculates an average value of the N pieces of data (N is the number of samples on the I / Q plane of the I / Q signal) and then calculates an average value based on the calculated average value. Distance information can be calculated. For example, the signal processor 150 may generate N data (D _sN , D _{sN −1} , .., D _{sN −N + 1} ) whenever N data is sampled, where D _SN is the sN-th phase delay data, s Is an integer of 1 or more). As another example, the signal processor 150 each time a data is sampled N data (D _p, D _{p -1,} .., D _{p -N + 1)} (D _p is a p-th phase delay data, p Is an integer greater than or equal to N). When calculating the average value every time the phase delay data is sampled, the signal processor 150 calculates an average value of the phase delay data currently sampled and the previous N-1 phase delay data, and the distance information of the target based on the average value. Can be calculated. The signal processor 150 may calculate distance information of the target from, for example, an average value of the sampling data according to Equation 9 below.

[Equation 9]

Where R is the distance of the target (m), c is the speed of light (3 × 10 ⁸ m / sec), φ _M is the average value (rad) of sampling data, and fm is the modulation frequency (Hz). When the target is moved by a distance of λ _0/2 (λ ₀ is c / f _0, f ₀ is the carrier frequency), I / Q signal is rotated in the first I / Q plane. For example, if the carrier frequency is 2.44 GHz, each time the target moves 6.15 cm, the I / Q signal rotates one revolution in the I / Q plane. After estimating the distance of a target until the N data is sampled initially, if N data is sampled as the target moves by a distance of λ ₀ (N-1) / 2N, an embodiment of the present invention According to the distance information of the target can be measured.

8 is a graph illustrating a distance of a target by sampling phase delay data according to an exemplary embodiment of the present invention. According to an embodiment of the present invention, an I / Q signal is demodulated from an amplitude modulated signal using a carrier frequency signal, and the phase delay data detected by the phase detection unit is sampled using the phase information of the I / Q signal. By calculating the distance information of the target from the average value of one data, as shown in FIG. 8, a ripple error due to a leak signal during the distance measurement of the target can be reduced. That is, according to the embodiment of the present invention, whenever the I / Q signal has a predetermined specific phase value, phase delay data resulting from the detection of the amplitude modulation signal (for example, envelope detection) is sampled, and The distance measurement error can be canceled by calculating the distance of the target based on the average value of the data.

Next, in step S27, the signal processor 150 may calculate distance information of the target corresponding to the unsampled data by using the average value of the sampling data and the information indicating the Doppler movement of the I / Q signal. FIG. 9 is an enlarged view of a portion 'C' shown in FIG. 8. Since the signal processor 150 samples the data and measures the distance of the target based on the average value of the data, the distance of the target has a constant value even though the target moves in the interval S between sampling. Therefore, in order to measure the distance of the target more precisely, the signal processor 150 estimates the distance information of the target with respect to the data belonging to the sampling interval S using the Doppler movement information of the I / Q signal. For example, the signal processor 150 may calculate distance information of the target corresponding to the data not sampled according to Equation 10 below.

[Equation 10]

Here, R _adaptive (n) is the distance information of the target corresponding to the nth data belonging to the sampling interval S, R _average (n) is the distance of the current target measured from the sampling data, and R _I (n) is n I-channel signal of the first data, R _I (n) is the _I -channel signal of the n-1th data, R _Q (n) is the Q-channel signal of the nth data, and R _Q (n) is the n-1 th Represents a Q-channel signal of data. That is, the signal processor 150 calculates the phase change of two adjacent phase delay data from the information indicating the Doppler movement of the I / Q signal, and additionally reflects the value corresponding to the phase change to the average value, thereby unsampling the phase delay data. Compute the distance information of the target for. By further performing step S27 according to an embodiment of the present invention, as shown in FIG. 10, the distance information of the target in the unsampled sampling data section S can also be calculated. Can be estimated more precisely.

11 is a graph showing the measurement of the distance of the target according to an embodiment of the present invention. As shown in FIG. 11, according to the embodiment of the present invention, it can be seen that the distance of the target can be accurately estimated without a large error compared to the distance of the actual target. According to the embodiment of the present invention, the measurement accuracy of the micro displacement can be obtained by using the Doppler effect of the carrier frequency. For example, when a phase difference of 1 ° on I / Q plane caused, λ _0/720 (λ ₀ is c / f ₀₎ a small displacement that corresponds to the (f ₀ is the carrier frequency, c is the speed of light) Occurs. According to an embodiment of the present invention, the average distance measurement error of the amplitude modulated radar can be reduced to about 1/10. In addition, according to one embodiment of the present invention, the maximum distance measurement error can be reduced to a level of 30% compared with the conventional.

It is to be understood that the above-described embodiments are provided to facilitate understanding of the present invention, and do not limit the scope of the present invention, and it is to be understood that various modifications may be made within the scope of the present invention. For example, each component shown in the embodiment of the present invention may be distributed and implemented, and conversely, a plurality of distributed components may be combined. Therefore, the technical protection scope of the present invention should be determined by the technical idea of the claims, and the technical protection scope of the present invention is not limited to the literary description of the claims, The invention of a category.

100: amplitude modulation radar 110: amplitude modulation signal transmission unit
111: modulated frequency signal generator 112: carrier frequency signal generator
113: power attenuator 114: mixer
115: amplifier 116: transmit antenna
120: detector 130: phase detection unit
140: demodulator 141: I / Q demodulator
142: low pass filter 150: signal processing unit
160: analog-to-digital converter 170: receiving antenna
180: low noise amplifier 190: power divider

Claims (20)

An amplitude modulated signal transmitter for synthesizing a modulated frequency signal and a carrier frequency signal to generate an amplitude modulated signal and transmitting the generated amplitude modulated signal to a target;
A detector for detecting a wireless signal including an amplitude modulated signal reflected from the target;
A phase detector configured to detect phase delay between the radio signal detected by the detector and the modulation frequency signal to generate phase delay data;
A demodulator for demodulating the radio signal into an I / Q signal using the carrier frequency signal; And
A signal processor configured to sample the phase delay data using the I / Q signal and calculate distance information of the target using the sampled phase delay data;
The signal processing unit,
And an amplitude modulation radar for sampling the data corresponding to the phase delay between the signal detected from the radio signal and the modulation frequency signal of the amplitude modulation signal using the I / Q signal. An amplitude modulated signal transmitter for synthesizing a modulated frequency signal and a carrier frequency signal to generate an amplitude modulated signal and transmitting the generated amplitude modulated signal to a target;
A detector for detecting a wireless signal including an amplitude modulated signal reflected from the target;
A phase detector configured to detect phase delay between the radio signal detected by the detector and the modulation frequency signal to generate phase delay data;
A demodulator for demodulating the radio signal into an I / Q signal using the carrier frequency signal; And
A signal processor configured to sample the phase delay data using the I / Q signal and calculate distance information of the target using the sampled phase delay data;
The demodulation unit,
An I / Q demodulator for demodulating the radio signal into the I / Q signal using the carrier frequency signal; And
And a low pass filter for removing high frequency signals from the demodulated I / Q signals. 3. The method of claim 2,
And the I / Q demodulator demodulates the radio signal using the carrier frequency signal to generate an I-channel signal and a Q-channel signal, thereby demodulating the radio signal into the I / Q signal. An amplitude modulated signal transmitter for synthesizing a modulated frequency signal and a carrier frequency signal to generate an amplitude modulated signal and transmitting the generated amplitude modulated signal to a target;
A detector for detecting a wireless signal including an amplitude modulated signal reflected from the target;
A phase detector configured to detect phase delay between the radio signal detected by the detector and the modulation frequency signal to generate phase delay data;
A demodulator for demodulating the radio signal into an I / Q signal using the carrier frequency signal; And
A signal processor configured to sample the phase delay data using the I / Q signal and calculate distance information of the target using the sampled phase delay data;
The signal processing unit,
N phase delay data corresponding to N phases (N is an integer of 2 or more) on an I / Q plane is sampled using the phase information of the I / Q signal, and the average value of the sampled N phase delay data is obtained. Calculating, and calculating distance information of the target based on the average value. 5. The method of claim 4,
The signal processor may be configured such that the phase of the I / Q signal is θ ₀ + 2πk / N (k = 0,1, .. N-1) (N is an integer of 2 or more, and θ ₀ is a predetermined value on the I / Q plane. An amplitude modulation radar for sampling the N phase delay data having a value of a reference phase value. 5. The method of claim 4,
The signal processing unit,
An amplitude modulation radar for calculating an average value of the current sampled phase delay data and previous N-1 phase delay data each time sampling the phase delay data, and calculating distance information of the target based on the average value. 5. The method of claim 4,
The signal processing unit,
The distance of the target with respect to the unsampled phase delay data is calculated by calculating a phase change of two adjacent phase delay data from information indicating the Doppler shift of the I / Q signal, and additionally reflecting the value corresponding to the phase change to the average value. Amplitude modulation radar to produce information. 8. The method according to any one of claims 1 to 7,
And an analog-to-digital converter for converting the phase delay data and the I / Q signal into a digital signal and transmitting the digital signal to the signal processor. 8. The method according to any one of claims 1 to 7,
And the phase detector detects the phase delay between the envelope of the radio signal detected by the detector and the modulation frequency signal. 8. The method according to any one of claims 1 to 7,
A receiving antenna for receiving the wireless signal;
A low noise amplifier for amplifying the received wireless signal; And
And a power divider for distributing and amplifying the amplified radio signal to the detector and the demodulator. delete A demodulator for demodulating a radio signal including an amplitude modulated signal received from a target object into an I / Q signal using a carrier frequency signal of the amplitude modulated signal; And
A signal processor configured to sample data corresponding to the signal detected from the wireless signal using the I / Q signal, and calculate distance information of the target using the sampled data;
The signal processing unit,
And measuring the data corresponding to the phase delay between the signal detected from the radio signal and the modulation frequency signal of the amplitude modulation signal by using the I / Q signal. The method of claim 12,
The signal processing unit,
Sampling the N data corresponding to the predetermined N phases (N is an integer of 2 or more) on the I / Q plane using the phase information of the I / Q signal, and calculating an average value of the sampled N data; And a distance measurement error reduction apparatus of an amplitude modulation radar that calculates distance information of the target based on the average value. 14. The method of claim 13,
The signal processing unit has a phase of the I / Q signal on the I / Q plane with θ ₀ + 2πk / N (k = 0,1, .. N-1) (N is an integer of 2 or more, θ ₀ is a predetermined value). And a distance measurement error reduction device of an amplitude modulation radar for sampling the N pieces of data having a value of a reference phase value). The method according to claim 13 or 14,
The signal processing unit,
The distance of the target with respect to the unsampled phase delay data is calculated by calculating a phase change of two adjacent phase delay data from information indicating the Doppler shift of the I / Q signal, and additionally reflecting the value corresponding to the phase change to the average value. An apparatus for reducing the distance measurement error of an amplitude modulated radar for calculating information. Demodulating a radio signal including an amplitude modulated signal received from a target object into an I / Q signal using a carrier frequency signal of the amplitude modulated signal;
Sampling data corresponding to a signal detected from the wireless signal using the I / Q signal; And
Comprising a step of calculating the distance information of the target by using the sampled data. 17. The method of claim 16,
Wherein the sampling comprises:
Sampling the phase delay data corresponding to the phase delay between the signal detected from the radio signal and the modulation frequency signal of the amplitude modulation signal using the I / Q signal. 17. The method of claim 16,
The sampling may include sampling N pieces of data corresponding to N phases (N is an integer of 2 or more) on an I / Q plane by using phase information of the I / Q signal.
The step of calculating the distance information,
Calculating an average value of the N pieces of data sampled; And
And calculating distance information of the target based on the average value. 19. The method of claim 18,
In the sampling, the phase of the I / Q signal is θ ₀ + 2πk / N (k = 0,1, .. N-1) on the I / Q plane, where N is an integer of 2 or more and θ ₀ is a predetermined value. And sampling the N pieces of data having a value of the reference phase value of the amplitude measurement radar. 20. The method according to claim 18 or 19,
Computing the phase change of two adjacent data from the information indicating the Doppler movement of the I / Q signal, and further reflects the value corresponding to the phase change in the average value, thereby calculating the distance information of the target to the unsampled data The method for reducing the distance measurement error of the amplitude modulation radar further comprising.

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