CN113866769A - Millimeter wave radar measurement method and device - Google Patents
Millimeter wave radar measurement method and device Download PDFInfo
- Publication number
- CN113866769A CN113866769A CN202111143587.8A CN202111143587A CN113866769A CN 113866769 A CN113866769 A CN 113866769A CN 202111143587 A CN202111143587 A CN 202111143587A CN 113866769 A CN113866769 A CN 113866769A
- Authority
- CN
- China
- Prior art keywords
- signals
- transmit
- transmission
- signal
- sequence
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
- G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
- G01S13/584—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets adapted for simultaneous range and velocity measurements
Abstract
The invention provides a millimeter wave radar measuring method and a device, comprising the following steps: generating a sequence of FMCW signals comprising a plurality of transmitted signals, a first transmitted signal having a starting transmission frequency f0The initial frequencies of two adjacent transmitting signals have an offset deltaf; transmitting the plurality of transmission signals, wherein the initial transmission time interval T between two adjacent transmission signals in the plurality of transmission signalsPlIs variable such that the product of the initial transmission frequency of the ith transmission signal of the plurality of transmission signals and its initial transmission time is linear with i; receiving a plurality of echo signals respectively corresponding to the plurality of transmission signals; mixing each of the plurality of transmit signals with a corresponding echo signal to obtain a plurality of baseband signals; and processing the plurality of baseband signals to obtain the distance and the speed of the target.
Description
Technical Field
The invention relates to the field of automatic driving, in particular to a vehicle-mounted millimeter wave radar measuring method and device.
Background
Millimeter-wave radar sensors are used in automotive autopilot solutions. Millimeter Wave radars usually continuously transmit a plurality of FMCW (Frequency Modulated Continuous Wave) signals, the FMCW signals are reflected by a target to obtain echo signals, and the distance and relative speed of the target from the radar can be obtained by processing the transmitted signals and the echo signals.
With the increasing requirements of the automatic driving function on the range resolution and the maximum detection distance of the radar sensor, the contradiction between the range resolution and the maximum detection distance caused by the fact that the millimeter wave radar adopts the conventional FMCW linear frequency modulation sequence waveform is increasingly highlighted. The frequency modulation stepping FMCW signal sequence can improve the radar ranging resolution ratio under the condition of not changing the frequency sweep bandwidth and the maximum detection distance. However, since the frequency modulation step introduces a secondary phase term related to the speed, when the target speed is high, the resolving power of the distance and the speed and the measurement accuracy are seriously influenced.
Disclosure of Invention
In order to solve the technical problem, the invention provides an improved FMCW millimeter wave radar measuring method.
In one aspect, the present invention provides a millimeter wave radar measurement method, including:
generating a sequence of frequency modulated continuous wave, FMCW, signals, wherein the sequence of FMCW signals includes a plurality of transmit signals, wherein a first transmit signal has a starting transmit frequency f0The initial frequencies of two adjacent transmitting signals have a deviation delta f;
transmitting the plurality of transmission signals by a radar antenna, wherein the initial transmission time interval T between two adjacent transmission signals in the plurality of transmission signalsPlIs variable such that a starting transmission frequency (f) of an ith transmission signal of the plurality of transmission signals0+ i Δ f) and its initial emission time
The product of the two is linear with i, wherein i is greater than or equal to 0;
receiving a plurality of echo signals respectively corresponding to the plurality of transmission signals;
mixing each of the plurality of transmit signals with a corresponding echo signal to obtain a baseband signal sequence comprising a plurality of baseband signals; and
and processing the baseband signal sequence to obtain the distance and the speed of the target.
Optionally, the starting transmission time interval between the ith transmission signal and the (i + 1) th transmission signal is inversely proportional to the quadratic function of i.
Optionally, the processing the baseband signal sequence to obtain the range and the velocity of the target comprises:
FFT transforming each baseband signal in the sequence of baseband signals in a first dimension to obtain a first dimension baseband signal spectrum, an
And performing FFT conversion on the baseband signal sequence in a second dimension to obtain a second dimension baseband signal frequency spectrum.
Optionally, the method further comprises,
obtaining a first spectrum peak position in the first dimension baseband signal spectrum and a second spectrum peak position in the second dimension baseband signal spectrum; and
the distance and velocity of the target are obtained using the first spectral peak position and the second spectral peak position.
Optionally, the method further comprises transmitting a second FMCW signal sequence, the second FMCW signal sequence comprising a plurality of second transmission signals, the originating transmission time interval between adjacent ones of the plurality of second transmission signals being variable such that the product of the originating radio frequency of the ith one of the plurality of second transmission signals and its originating transmission time is linear with i.
Optionally, the frequency sweep slope of the second plurality of transmit signals is the same as the frequency sweep slope of the plurality of transmit signals.
Optionally, the frequency sweep slope of the second plurality of transmit signals is different from the frequency sweep slope of the plurality of transmit signals.
Optionally, the method further comprises:
obtaining the range and velocity of the target, and the range ambiguity in the first dimension baseband signal spectrum and the velocity ambiguity in the second dimension baseband signal spectrum using the sweep slopes of the plurality of transmit signals and the sweep slopes of the plurality of second transmit signals.
Optionally, the method further comprises selecting the offset Δ f between the starting transmission frequencies of two adjacent transmission signals such that
Where N is the number of signals in the FMCW signal sequence and B is the swept bandwidth of the FMCW signal sequence.
Another aspect of the present invention provides a millimeter wave radar measuring device, including:
a waveform generation module configured to generate a sequence of frequency modulated continuous wave, FMCW, signals, the sequence of FMCW signals including a plurality of transmit signals, wherein a first transmit signal has a starting transmit frequency f0The initial frequencies of two adjacent transmitting signals have an offset deltaf;
a transmit antenna configured to transmit the plurality of transmit signals;
a control module configured to control the transmit antennas to transmit the sequence of FMCW signals as required: a starting transmission time interval T between two adjacent transmission signals in the plurality of transmission signalsPlIs variable such that a starting transmission frequency (f) of an ith transmission signal of the plurality of transmission signals0+ i Δ f) and its initial emission time
The product of the two is linear with i, wherein i is greater than or equal to 0;
a receive antenna configured to receive a plurality of echo signals respectively corresponding to the plurality of transmit signals; and
a mixer configured to mix each of the plurality of transmit signals with a corresponding echo signal to obtain a baseband signal sequence comprising a plurality of baseband signals, respectively;
wherein the control module is further configured to process the baseband signal sequence to derive a range and a velocity of a target.
Optionally, the starting transmission time interval between the ith transmission signal and the (i + 1) th transmission signal is inversely proportional to the quadratic function of i.
Optionally, the processing the baseband signal sequence to obtain the range and the velocity of the target comprises:
FFT transforming each baseband signal in the sequence of baseband signals in a first dimension to obtain a first dimension baseband signal spectrum, an
And performing FFT conversion on the baseband signal sequence in a second dimension to obtain a second dimension baseband signal frequency spectrum.
Optionally, the control module is further configured to:
obtaining a first spectrum peak position in the first dimension baseband signal spectrum and a second spectrum peak position in the second dimension baseband signal spectrum; and
the distance and velocity of the target are obtained using the first spectral peak position and the second spectral peak position.
Optionally, the apparatus is further configured to transmit a second FMCW signal sequence, the second FMCW signal sequence comprising a plurality of second transmission signals, the originating transmission time interval between adjacent ones of the plurality of second transmission signals being variable such that the product of the originating radio frequency of the ith one of the plurality of second transmission signals and its originating transmission time is linear with i.
Optionally, the frequency sweep slope of the second plurality of transmit signals is the same as the frequency sweep slope of the plurality of transmit signals.
Optionally, the frequency sweep slope of the second plurality of transmit signals is different from the frequency sweep slope of the plurality of transmit signals.
Optionally, the control module is further configured to:
obtaining the range and velocity of the target, and the range ambiguity in the first dimension baseband signal spectrum and the velocity ambiguity in the second dimension baseband signal spectrum using the sweep slopes of the plurality of transmit signals and the sweep slopes of the plurality of second transmit signals.
Optionally, the control module is further configured to: the offset deltaf between the starting transmission frequencies of two adjacent transmission signals is chosen such that
Where N is the number of signals in the FMCW signal sequence and B is the swept bandwidth of the FMCW signal sequence.
Yet another aspect of the invention provides an electronic device comprising a processor and a memory, the memory having stored thereon program instructions; the processor executes program instructions to implement the millimeter wave radar measurement method of any one of claims 1 to 9.
By selecting the non-fixed pulse repetition interval, the method and the device can eliminate the secondary phase item related to the speed introduced by the sweep frequency step, eliminate the broadening effect of the secondary phase item on the slow time frequency spectrum and the migration effect of the secondary phase item on the spectrum value position, and further avoid the measurement precision loss of a high-speed target caused by the influence of the secondary phase item.
Drawings
Fig. 1A shows a schematic diagram of the amplitude versus time of a transmission signal of a millimeter wave radar.
Fig. 1B shows a schematic diagram of the frequency versus time of the transmission signal and the echo signal of the millimeter wave radar.
Fig. 2 is a schematic composition diagram of the millimeter wave radar sensor.
Fig. 3 is a schematic diagram of a waveform sequence of a pulse signal according to the first embodiment.
Fig. 4 is a schematic diagram of a waveform sequence of a pulse signal according to a second embodiment.
Fig. 5 is a schematic illustration of a second-dimensional spectral peak according to the present invention in comparison to the prior art.
Fig. 6 is a flowchart of a millimeter wave radar measurement method according to the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments disclosed below.
The FMCW radar transmits continuous waves with variable frequency in a frequency sweep period, echoes after being transmitted by an object have a certain frequency difference with a transmitting signal, and distance information and relative speed information between a target and the radar can be acquired by processing the transmitting signal and the echo signals. One signal transmitted by the FMCW radar may be referred to as chirp (also referred to as a pulse signal, a ramp signal, and referred to herein as a transmit signal).
Fig. 1A shows the amplitude of the transmitted signal of the FMCW radar versus time. As shown in fig. 1A, one transmitted signal is a sinusoid whose frequency increases linearly with time.
After a transmitting signal sent by the radar through the transmitting antenna contacts a target, the transmitting signal is reflected to a receiving antenna of the radar to form an echo signal.
Fig. 1B shows the frequency versus time of the transmitted signal and the echo signal of the radar, wherein the transmitted signal is shown in solid lines and the echo signal is shown in dashed lines. The echo signal has a delay relative to the transmit signal.
As shown, the radar transmits a plurality of transmit signals, referred to herein as a sequence of transmit signals. Each transmitted signal has a corresponding echo signal, and the radar receives a plurality of echo signals, each echo signal corresponding to one transmitted signal.
As shown, the signal sequence has a swept bandwidth B, a signal duration tpInitial transmission frequency f0Slope of the sweep frequency
As shown in fig. 1B, the frequency of the transmitted signal is linear with time, and the frequency sweep slope of the echo signal is the same as that of the corresponding transmitted signal.
Note that although in FIG. 1B, the signal duration t is shown aspShown as the transmission interval (pulse repetition interval (PRI)) between adjacent signals is the same, but in practical applications, tpSee fig. 3 and 4, which may be different from the PRT.
Fig. 2 is a schematic composition diagram of millimeter wave radar sensor 200.
As shown in fig. 2, millimeter-wave radar sensor 200 includes a waveform generation module 202, a transmit antenna 204, a receive antenna 206, a mixer 208, and a control and processing module 210.
The waveform generation module 202 generates FMCW signal sequences, each sequence including a plurality of FMCW signals (e.g., the signal in fig. 1A and the transmit signal in fig. 1B).
The transmit antenna 204 transmits the plurality of FMCW signals. After the signal contacts the target 212, it is reflected back onto the receiving antenna, forming an echo signal.
The receive antenna 206 receives the echo signal.
Note that although only one transmitting antenna 204 and one receiving antenna 206 are shown in fig. 2, in practical applications, millimeter wave radar sensor 200 may have multiple transmitting antennas and multiple receiving antennas, as described below.
The mixer 208 mixes the transmit signal with its corresponding echo signal to obtain a baseband signal, which is an Intermediate Frequency (IF) signal. Mixing a plurality of transmitting signals in the signal sequence with a plurality of echo signals corresponding to the transmitting signals can obtain a baseband signal sequence comprising a plurality of baseband signals.
The control and processing module 210 may process the mixed baseband signal sequence to obtain the target range and velocity.
In particular, the control and processing module 210 may sample a baseband signal sequence. In particular, the control and processing module 210 may use a sampling frequency fsEach baseband signal in the sequence of baseband signals is sampled. The samples of the baseband signal sequence may be represented in a fast time dimension and a slow time dimension.
Fast timeIndicating the time at which a plurality of samples are taken within a baseband signal, each sample time being available
Where j denotes the jth sampling point within the signal pulse.
The slow time refers to the "time" used to mark different baseband signals when processing a sequence of baseband signals, and can be generally represented by the number i of the baseband signal in the sequence. The sampling frequency in the slow time dimension, i.e., the Pulse Repetition Frequency (PRF).
The control and processing module 210 may convert the sampled baseband signal sequence into a frequency spectrum through an FFT (fast fourier transform), perform a range-doppler joint processing, and obtain range and velocity information of the target through detection of a peak of the frequency spectrum.
Converting the baseband signal sequence to a frequency spectrum may include a two-dimensional FFT that resolves the target from two dimensions. The two-dimensional FFT includes a first-dimensional FFT transform and a second-dimensional FFT transform.
In the first dimension FFT, a one-dimensional FFT is performed on a plurality of sample points of each baseband signal in the sequence of baseband signals, providing a one-dimensional spectrum for the baseband signals. A number of different spectra are thus obtained for each sequence of baseband signals, each spectrum corresponding to a baseband signal. The peak position p in each spectrum may be obtained (i.e., the first-dimensional spectral peak is obtained at the p-th sample point within the signal), and p may be referred to as a distance index. In millimeter wave radar detection, the first-dimension FFT is also referred to as a range FFT.
In the second-dimensional FFT, a plurality of baseband signals in the sequence are FFT-transformed. The second dimension FFT transform is also known as doppler FFT or velocity FFT. Specifically, in the two-dimensional FFT, the spectral peak p of each signal is usediAnd the signal pulse number i is taken as input to carry out FFT conversion, thereby obtaining a two-dimensional frequency spectrum. The peak location q in the two-dimensional spectrum (i.e., the two-dimensional spectrum peak is obtained at the qth signal) may be obtained, and q may be referred to as the doppler index or velocity index.
After the FFT of two dimensions, a range-doppler map (RD map) can be obtained; the RDmap is subjected to Constant False Alarm Rate (CFAR) detection, and a preliminary detection result of the target, including the distance of the target relative to the radar and the estimated speed, can be obtained.
The radar system of the present invention may be applied to vehicles, aircrafts, robots, or the like, for example, automatic or semi-automatic driving cars, unmanned aircrafts, unmanned aerial vehicles, or the like; the method can also be applied to terminal equipment such as smart phones, tablet computers, wearable equipment and the like; it is also applicable to Road Side Unit (RSU) for detecting speed, position, etc. of vehicles on a road. The RSU may include, but is not limited to, a velometer, a camera, an indicator light, and the like, which is not limited in this embodiment.
In the conventional FMCW millimeter wave radar measurement scheme, the interval between adjacent pulse transmissions (pulse repetition time (PRT)) is the same, and the range resolution and the maximum detection range are respectively
And
where B is the swept bandwidth of the signal, c is the speed of light, tpFor signal duration, fsIs the sampling frequency for each signal. If the range resolution is improved by increasing the sweep bandwidth B, this will result in a decrease in the maximum detection range.
The frequency shift delta f is set between the initial emission frequencies of each adjacent signal in the FMCW signal sequence with frequency modulation stepping, and the radar ranging resolution can be improved under the condition that the sweep frequency bandwidth and the maximum detection distance are not changed. However, the FMCW signal sequence using frequency modulation stepping introduces a secondary phase term related to speed, which causes problems of spectrum broadening and spectrum value position shift when the target moves, especially moves at high speed, and seriously affects resolution capability and measurement accuracy of distance and speed, thereby affecting radar detection performance.
In view of the above problems, the present patent proposes an improved millimeter wave radar measurement method, which can effectively eliminate the influence of the velocity-related quadratic phase term on the measurement accuracy by improving the frequency-modulated stepped FMCW signal sequence. Although this patent is based on in-vehicle millimeter wave radar applications, it is not limited to the in-vehicle application field. The improved method can be applied to various fields such as traffic speed measuring radar, security radar and the like.
Example one
In embodiment one of the present invention, the millimeter wave radar may utilize one or more transmitting antennas 204 to transmit the FMCW signal sequence generated by the waveform generation module 202, and each antenna may transmit one or more signal sequences. Each signal sequence may include a plurality of transmit signals, each transmit signal in the sequence having the same sweep bandwidth B and a sweep slope
Similarly, the starting transmit frequency of the adjacent signal has a frequency offset Δ f. The sequence of different sequence transmission can be overlapped in sequence or another sequence can be started to transmit after the transmission of one sequence is finished.
Fig. 3 is a schematic diagram of a waveform sequence of a pulse signal according to the first embodiment.
As shown in fig. 3, the plurality of FMCW signals in a sequence consisting of signals transmitted by the same antenna are numbered 0,1,2, …, N-1 in sequence.
The starting frequency of the transmitted signal with sequence number 0 is f0With a fixed offset deltaf between the start frequencies of temporally adjacent transmit signals, i.e. with the start frequency f of the transmit signal numbered i0+ i Δ f, Δ f may be positive or negative.
The interval between the start transmission times of two time-adjacent transmission signals may be defined as a Pulse Repetition Interval (PRI). According to the present invention, the interval between the start transmission times of adjacent FMCW signals in the FMCW signal sequence (which may be referred to herein as the start transmission time interval) may be variable, i.e. the pulse repetition intervals in the FMCW signal sequence are different.
Specifically, theIn other words, if the initial transmission time interval between the transmission signal of sequence number 0 and the transmission signal of sequence number 1 is TP0The initial transmission time interval between a transmission signal with sequence number l and a transmission signal with sequence number l +1 is TPlThe first signal in the sequence having a starting transmission frequency f0And the frequency offset between two adjacent signals in the sequence is Δ f, the transmitted signal sequence needs to satisfy the following condition:
wherein the content of the first and second substances,
wherein a is0、b0、b1、b2、c0、c1Are all constants.
At setting f0And Δ f, the parameter a may be obtained by substituting equation (2) for equation (1) and establishing a plurality of relational expressions using data of a plurality of pulses (for example, pulse number i)0、b0、b1、b2、c0、c1From the value of (a), T of the initial transmission time interval of the adjacent transmission signals in the signal sequence can be obtainedPiIs expressed by (i.e., formula (2)).
The invention enables the initial transmission frequency (f) of the ith signal in the sequence0+ i Δ f) and initial launch time
The product of (c) can be linear with i, i.e., expressed as a linear function of i (c)1·i+c0) The velocity-dependent quadratic phase term in the baseband signal waveform can thus be eliminated, as described below.
As shown in the above equation (2), the present invention can set the initial transmission time interval between the ith FMCW signal and the (i + 1) th FMCW signal to be a quadratic function of i (b)0+b1i+b2i2) In inverse proportion. The parameter a can be obtained by using the time interval of signal transmission in the form of the formula (2) in conjunction with the formula (1)0、b0、b1、b2And thus the initial transmission time interval between two signals adjacent in time in the signal sequence.
The millimeter-wave radar receives an echo signal reflected from a target (for example, an obstacle near the traveling track of the vehicle) by the receiving antenna 206, and mixes the echo signal with a transmission signal to obtain a baseband signal.
For a conventional FMCW sequence, the initial transmit frequencies of the signals in the sequence are equal, fc＝f0And the pulse repetition intervals between two adjacent signals are all equal and are TPi＝TP0The baseband signal corresponding to the nth target can be expressed as:
wherein A isnThe amplitude of the baseband signal, r, corresponding to the nth targetnAnd vnRespectively representing the distance and the relative speed of the nth target relative to the radar, mu is the slope of the sweep frequency, j is the serial number of the sampling point in the signal, fsIs the sampling frequency for each signal.
For moving objects, for the signal numbered i in the sequence,
taking equation (3) and omitting the small term, the following equation can be obtained:
for the frequency modulated stepped FMCW signal sequence of the present invention, f isc＝f0The + i Δ f and equation (1) are taken into equation (4) and the small term is omitted, and the baseband signal corresponding to the nth target can be expressed as:
wherein A isnAmplitude, r, of the baseband signal corresponding to the nth targetnAnd vnRespectively representing the distance and the relative speed of the nth target relative to the radar, mu being the frequency sweep slope of the transmitted signal, fsFor each signal sampling frequency, j is the sample point number within the signal, and i is the signal number in the sequence.
According to equation (5), the fast time frequency can be expressed as follows:
the slow time frequency can be expressed as follows:
the fast time frequency is obtained from the fast time spectral peak as follows:
where p is the peak position of the spectrum of a signal, i.e., the number of the peak points of the spectrum obtained by the first dimension FFT, Nsample is the number of sampling points in the signal, fsIs the sampling rate within the signal.
From equations (6) and (8), the following equation can be obtained:
the fast time frequency is obtained from the fast time spectral peak as follows:
where q is the number of peak points of the spectrum obtained by the second dimension FFT and Nchirp is the number of signals in the signal sequence.
From equations (7) and (10), the following equation can be obtained:
the distance r of the nth target can be obtained by the equations (9) and (11)nAnd relative velocity vn。
According to the method of the invention, by appropriately selecting a fixed offset Δ f of the starting frequencies of adjacent FMCW signals, an amount of distance can be introduced in the slow time frequency. That is, referring to the formula (11),
and
correlation, from which it can be deduced that the distance resolution can be expressed as
Where Nchirp is the number of pulse signals in the pulse train signal sequence. Whereas the conventional FMCW signal sequence has a range resolution of
Therefore, by properly selecting the fixed offset deltaf of the central frequency point of the adjacent FMCW signals, the method leads to
Can realize delta r2＜Δr1Thereby improved distance resolution can be achieved.
Example two
In a second embodiment of the invention, millimeter-wave radar may utilize one or more transmit antennas 204 to transmit signals generated by waveform generation module 202Generating FMCW signal sequences, each antenna transmitting one or more signal sequences, each signal sequence comprising a plurality of pulsed signals, each signal in the sequence having a same sweep bandwidth B and a sweep slope
Similarly, the starting transmit frequency of the adjacent signal has a frequency offset Δ f. The sequence of different sequence transmission can be overlapped in sequence or another sequence can be started to transmit after the transmission of one sequence is finished.
Unlike the first embodiment, in the second embodiment, the starting frequency f of different FMCW signal sequences0And slope
Are different, whereby different parameters of different signal sequences (e.g. the starting transmission frequency f of the signal sequence) can be used0And slope μ, etc.) to obtain the distance and velocity of the target relative to the radar.
Fig. 4 is a schematic diagram of an FMCW signal sequence according to the second embodiment. As shown, the start frequency and slope of the signal sequence transmitted by the transmitting antenna 2 are different from those of the transmitting antenna 1.
Note that although fig. 4 shows that two signal sequences are transmitted using two antennas, respectively, in actual operation, more than two antennas may be used to transmit different signal sequences, respectively, or one antenna may be used to transmit a plurality of signal sequences.
In the second embodiment, the initial transmission time interval (i.e., equation (1) and equation (2)), the baseband signal representation (i.e., equation (5)), the fast time frequency representation (equation (6)), and the slow time frequency representation (equation (7)) of the transmission signal of each signal sequence are the same as those in the first embodiment, and are not described again here.
As described above, after the receive antenna receives the echo signal and mixes the transmit signal and the echo signal, the baseband signal may be converted to a frequency spectrum. Converting the baseband signal to a frequency spectrum may include a first dimension FFT transform and a second dimension FFT transform.
In the first dimension FFT transformFor a plurality of sampling points (using a sampling frequency f) of each baseband signal in the sequence of baseband signalssA plurality of sampling points obtained by sampling one baseband signal) is subjected to one-dimensional FFT to provide a one-dimensional spectrum for the FMCW signal. A certain number (Nchirp) of different frequency spectra are thus obtained for each signal sequence. The peak location p in each spectrum may be obtained (i.e., the first-dimension spectral peak is obtained at the p-th sampling point), which may be referred to as a distance index. In millimeter wave radar detection, the first-dimension FFT is also referred to as a range FFT.
In the second-dimensional FFT, a plurality of baseband signals in the sequence are FFT-transformed. The second dimension FFT transform is also known as doppler FFT or velocity FFT. Specifically, in the two-dimensional FFT, FFT conversion is performed using a spectral peak of each signal (a power peak corresponding to the p-th sample point in the signal) and the number i of the signal in the sequence as inputs, thereby obtaining a two-dimensional spectrum. The peak location q in the two-dimensional spectrum (i.e., the second-dimensional spectral peak is obtained at the qth signal) may be obtained, and q may be referred to as the doppler index or the velocity index.
Because the range resolution and the maximum speed measurement range of the radar are limited, the range information and the speed information in the two FFTs can be subjected to an aliasing phenomenon.
In particular, "range aliasing" refers to the true range R of an objectTruePossibly estimated R detected by CFAREstimation ofPlus an integer multiple of the maximum range Rmax, the value of which is called the range ambiguity. "velocity aliasing" refers to the true velocity V of an objectTruePossibly pre-estimated V detected by CFAREstimation ofPlus an integer multiple of the maximum velocity measurement range Vmax, the value of this integer multiple is called the velocity ambiguity number (also called doppler ambiguity number).
For example, when 512 samples are subjected to FFT, the peak appears at the nth point of the frequency domain, but the same peak may appear at the 512i + n (i ≧ 1) th point of the frequency domain, which affects the accuracy of the subsequent data processing. The number of times the same peak occurs at the same position is called a blur number, with the number of samples (e.g., 512, 1024, etc.) of the FFT as a period.
The fast time frequency of the kth antenna can be obtained from the fast time spectral peak as follows:
where l represents the ambiguity number (i.e., distance ambiguity number) of the fast time FFT (first dimension FFT), pkRepresenting the peak position in the first dimension FFT spectrum of the signal sequence transmitted by the kth antenna.
The slow time frequency of the kth antenna can be obtained from the fast time spectral peak as follows:
where m represents the ambiguity (i.e., Doppler ambiguity or velocity ambiguity) of the slow-time FFT (second-dimension FFT), qkRepresenting the peak position in the second dimension FFT spectrum of the signal sequence transmitted by the kth antenna.
From equations (6) and (12), the following equations can be obtained:
from equations (7) and (13), the following equation can be obtained:
wherein mukIs the slope of the sweep frequency, f, of the signal in the k-th signal sequence (e.g., the signal sequence transmitted by the k-th antenna)0,kIs the starting frequency, r, of the pulse signal in the k-th signal sequencenIs the distance of the nth object, vnIs the relative velocity of the nth target.
In comparison with the expressions (9) and (11) of example one, the unknowns l and m appear in the expressions (14) and (15), and do not useDifferent mu from signal sequencekAnd f0,kTo obtain a larger number of relations, and the distance r of the target can be obtained by solving the relations or by maximum likelihood estimationnVelocity v of the targetnAnd a distance ambiguity number l and a doppler ambiguity number (velocity ambiguity number) m, and a larger range of distance measurement and velocity measurement can be achieved.
Note that for illustration, the first signal sequence (represented by a solid line) and the second signal sequence (represented by a dashed line) are shown in fig. 3 and 4 as being transmitted by two transmit antennas (represented by antenna number 1 and antenna number 2, respectively), respectively, but the first signal sequence and the second signal sequence may also be transmitted by the same transmit antenna. In other words, the transmitted multiple signal sequences may be transmitted by different transmit antennas or by the same transmit antenna, respectively.
Fig. 5 is a schematic illustration of a second-dimensional spectrum according to the present invention compared to a second-dimensional spectrum of the prior art.
As shown in fig. 5, the solid line is the second-dimensional spectrum at the non-fixed pulse repetition interval according to the present invention, and the dotted line is the second-dimensional spectrum at the fixed pulse repetition interval in the related art. The 0 point on the horizontal axis represents the true spectral peak position corresponding to the target.
As shown, the second dimension spectrum at a fixed pulse repetition interval in the prior art deviates from the true spectrum peak position, and the peak is not obvious and is not easy to detect.
In contrast, the peak position of the second-dimensional frequency spectrum obtained by the millimeter wave radar detection approaches the peak position of the real frequency spectrum, and the peak is obvious and easy to detect.
Fig. 6 is a flowchart of a millimeter wave radar measurement method according to the present invention.
In step 601, a sequence of frequency modulated continuous wave, FMCW, signals may be generated.
An FMCW signal sequence may be generated by the waveform generation module 202, where the FMCW signal sequence includes a plurality of transmit signals, where a first transmit signal has a starting transmit frequency f0Of the starting frequencies of two adjacent transmission signalsWith an offset deltaf therebetween.
At step 602, the FMCW signal sequence may be transmitted by a radar antenna.
The FMCW signal sequence may be transmitted by the transmission antenna 204 according to the set initial transmission time interval between adjacent two transmission signals.
Specifically, the initial transmission time interval T between two adjacent transmission signals in the plurality of transmission signals in the FMCW signal sequencePlIs variable such that a starting transmission frequency (f) of an i-th transmission signal of the plurality of transmission signals0+ i Δ f) and its initial emission time
The product of the two is linear with i (as shown in formula (1),
wherein i is greater than or equal to 0.
The initial transmission time interval between the ith transmission signal and the (i + 1) th transmission signal may be inversely proportional to a quadratic function of i, as shown in equation (2).
At step 603, a plurality of echo signals respectively corresponding to the plurality of transmit signals may be received.
The echo signal reflected after the transmitted signal contacts the target may be received by the receive antenna 206. The transmitted signal may be reflected back to the radar by one or more targets, each target having a corresponding echo signal.
At step 604, each of the plurality of transmit signals may be mixed with a corresponding echo signal to obtain a baseband signal sequence including a plurality of baseband signals.
At step 605, the baseband signal sequence may be processed to obtain the range and velocity of the target.
Processing the baseband signal sequence to obtain the range and the speed of the target comprises: FFT conversion is performed on each baseband signal in the sequence of baseband signals in a first dimension to obtain a first dimension baseband signal spectrum, and FFT conversion is performed on the sequence of baseband signals in a second dimension to obtain a second dimension baseband signal spectrum.
Further, a first spectral peak position (p) in the first dimension baseband signal spectrum and a second spectral peak position (q) in the second dimension baseband signal spectrum may be obtained; and using the first spectral peak position and the second spectral peak position to obtain the range and velocity of the target.
For example, the distance r of the target can be obtained using the above-described equations (9) and (11)nAnd velocity vn。
Further, a second FMCW signal sequence may be transmitted, the second FMCW signal sequence including a plurality of second transmission signals, a start transmission time interval between adjacent transmission signals of the plurality of second transmission signals being variable such that a product of a start transmission frequency of an ith transmission signal of the plurality of second transmission signals and a start transmission time thereof has a linear relationship with i.
In an aspect, the frequency sweep slope of the second plurality of transmit signals and the frequency sweep slope of the plurality of transmit signals may be the same.
In another aspect, the frequency sweep slope of the second plurality of transmit signals may be different from the frequency sweep slope of the plurality of transmit signals.
Further, in the case that the frequency sweep slopes of the plurality of second transmission signals are different from the frequency sweep slopes of the plurality of transmission signals, the distance and the speed of the target, and the distance ambiguity in the first-dimensional baseband signal spectrum and the speed ambiguity in the second-dimensional baseband signal spectrum can be obtained using the frequency sweep slopes of the plurality of transmission signals and the frequency sweep slopes of the plurality of second transmission signals. For example, the distance blur number l and the speed blur number m can be obtained using equations (12) and (13) as described above.
Furthermore, the offset Δ f between the starting transmission frequencies of two adjacent transmission signals can be selected such that
Where N is the number of signals in the FMCW signal sequence and B is the swept bandwidth of the FMCW signal sequence.
The illustrations set forth herein in connection with the figures describe example configurations and are not intended to represent all examples that may be implemented or fall within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration," and does not mean "preferred" or "advantageous over other examples. The detailed description includes specific details to provide an understanding of the described technology. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.
In the drawings, similar components or features may have the same reference numerals. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).
The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and the following claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hard-wired, or any combination thereof. Features that perform functions may also be physically located at various locations, including being distributed such that portions of functions are performed at different physical locations. Further, as used herein, including in the claims, "or" as used in a list of items (e.g., a list of items accompanied by a phrase such as "at least one of" or "one or more of") indicates an inclusive list, such that a list of at least one of, for example, A, B or C means a or B or C or AB or AC or BC or ABC (i.e., a and B and C). Also, as used herein, the phrase "based on" should not be read as referring to a closed condition set. For example, an exemplary step described as "based on condition a" may be based on both condition a and condition B without departing from the scope of the present disclosure. In other words, the phrase "based on," as used herein, should be interpreted in the same manner as the phrase "based, at least in part, on.
Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, a non-transitory computer-readable medium may include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), Compact Disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a web site, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk (disk) and disc (disc), as used herein, includes CD, laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.
The description herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (19)
1. A millimeter wave radar measurement method, comprising:
generating a sequence of frequency modulated continuous wave, FMCW, signals, wherein the sequence of FMCW signals includes a plurality of transmit signals, wherein a first transmit signal has a starting transmit frequency f0The initial frequencies of two adjacent transmitting signals have an offset deltaf;
transmitting the plurality of transmission signals by a radar antenna, the initial transmission time interval T between two adjacent transmission signals in the plurality of transmission signalsPlIs variable such that a starting transmission frequency (f) of an ith transmission signal of the plurality of transmission signals0+ i Δ f) and its initial emission time
The product of the two is linear with i, wherein i is greater than or equal to 0;
receiving a plurality of echo signals respectively corresponding to the plurality of transmission signals;
mixing each of the plurality of transmit signals with a corresponding echo signal to obtain a baseband signal sequence comprising a plurality of baseband signals; and
and processing the baseband signal sequence to obtain the distance and the speed of the target.
2. The method of claim 1, wherein a starting transmission time interval between an ith transmission signal and an (i + 1) th transmission signal is inversely proportional to a quadratic function of i.
3. The method of claim 1, wherein processing the baseband signal sequence to obtain the range and velocity of the target comprises:
performing an FFT on each baseband signal in the sequence of baseband signals in a first dimension to obtain a first dimension baseband signal spectrum, an
And performing FFT conversion on the baseband signal sequence in a second dimension to obtain a second dimension baseband signal frequency spectrum.
4. The method of claim 3, further comprising,
obtaining a first spectrum peak position in the first dimension baseband signal spectrum and a second spectrum peak position in the second dimension baseband signal spectrum; and
obtaining a distance and a velocity of the target using the first spectral peak position and the second spectral peak position.
5. The method of claim 1, further comprising transmitting a second FMCW signal sequence, the second FMCW signal sequence comprising a plurality of second transmit signals, a starting transmit time interval between adjacent ones of the plurality of second transmit signals being variable such that a product of a starting transmit frequency of an ith one of the plurality of second transmit signals and its starting transmit time is linear with i.
6. The method of claim 5, wherein a slope of a frequency sweep of the second plurality of transmit signals is the same as a slope of a frequency sweep of the plurality of transmit signals.
7. The method of claim 5, wherein a slope of a frequency sweep of the second plurality of transmit signals is different from a slope of a frequency sweep of the plurality of transmit signals.
8. The method of claim 7, further comprising:
using the sweep slopes of the plurality of transmit signals and the sweep slopes of the plurality of second transmit signals to obtain the range and velocity of the target, and the range ambiguity in the first dimension baseband signal spectrum and the velocity ambiguity in the second dimension baseband signal spectrum.
9. The method of claim 1, further comprising selecting an offset Δ f between starting transmit frequencies of two adjacent transmit signals such that
Where N is the number of signals in the FMCW signal sequence and B is the swept bandwidth of the FMCW signal sequence.
10. A millimeter wave radar measurement device, comprising:
a waveform generation module configured to generate a sequence of frequency modulated continuous wave, FMCW, signals, the sequence of FMCW signals including a plurality of transmit signals, wherein a first transmit signal has a starting transmit frequency f0The initial frequencies of two adjacent transmitting signals have an offset deltaf;
a transmit antenna configured to transmit the plurality of transmit signals;
a control module configured to control the transmit antennas to transmit the sequence of FMCW signals as required: a starting transmission time interval T between two adjacent transmission signals in the plurality of transmission signalsPlIs variable such that a starting transmission frequency (f) of an ith transmission signal of the plurality of transmission signals0+ i Δ f) and its initial emission time
The product of the two is linear with i, wherein i is greater than or equal to 0;
a receiving antenna configured to receive a plurality of echo signals respectively corresponding to the plurality of transmission signals; and
a mixer configured to mix each of the plurality of transmit signals with a corresponding echo signal to obtain a baseband signal sequence comprising a plurality of baseband signals, respectively;
wherein the control module is further configured to process the baseband signal sequence to derive a range and a velocity of a target.
11. The apparatus of claim 10, wherein a starting transmission time interval between an ith transmission signal and an (i + 1) th transmission signal is inversely proportional to a quadratic function of i.
12. The apparatus of claim 10, wherein processing the baseband signal sequence to obtain the range and velocity of the target comprises:
performing an FFT on each baseband signal in the sequence of baseband signals in a first dimension to obtain a first dimension baseband signal spectrum, an
And performing FFT conversion on the baseband signal sequence in a second dimension to obtain a second dimension baseband signal frequency spectrum.
13. The apparatus of claim 12, the control module further configured to:
obtaining a first spectrum peak position in the first dimension baseband signal spectrum and a second spectrum peak position in the second dimension baseband signal spectrum; and
obtaining a distance and a velocity of the target using the first spectral peak position and the second spectral peak position.
14. The apparatus of claim 10, wherein the millimeter wave radar measurement device is further configured to:
transmitting a second FMCW signal sequence that includes a plurality of second transmit signals, a starting transmit time interval between adjacent ones of the plurality of second transmit signals being variable such that a product of a starting transmit frequency of an ith one of the plurality of second transmit signals and its starting transmit time is linear with i.
15. The apparatus of claim 14, wherein a slope of a frequency sweep of the second plurality of transmit signals is the same as a slope of a frequency sweep of the plurality of transmit signals.
16. The apparatus of claim 14, wherein a slope of a frequency sweep of the second plurality of transmit signals is different from a slope of a frequency sweep of the plurality of transmit signals.
17. The apparatus of claim 16, the control module further configured to:
using the sweep slopes of the plurality of transmit signals and the sweep slopes of the plurality of second transmit signals to obtain the range and velocity of the target, and the range ambiguity in the first dimension baseband signal spectrum and the velocity ambiguity in the second dimension baseband signal spectrum.
18. The apparatus of claim 10, wherein the control module is further configured to: the offset deltaf between the starting transmission frequencies of two adjacent transmission signals is chosen such that
Where N is the number of signals in the FMCW signal sequence and B is the swept bandwidth of the FMCW signal sequence.
19. An electronic device comprising a processor and a memory, the memory storing program instructions; the processor executes program instructions to implement the millimeter wave radar measurement method of any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111143587.8A CN113866769A (en) | 2021-09-28 | 2021-09-28 | Millimeter wave radar measurement method and device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111143587.8A CN113866769A (en) | 2021-09-28 | 2021-09-28 | Millimeter wave radar measurement method and device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113866769A true CN113866769A (en) | 2021-12-31 |
Family
ID=78991837
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111143587.8A Pending CN113866769A (en) | 2021-09-28 | 2021-09-28 | Millimeter wave radar measurement method and device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113866769A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115267698A (en) * | 2022-06-29 | 2022-11-01 | 珠海正和微芯科技有限公司 | FMCW radar moving and micro-moving target detection and identification method and system |
-
2021
- 2021-09-28 CN CN202111143587.8A patent/CN113866769A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115267698A (en) * | 2022-06-29 | 2022-11-01 | 珠海正和微芯科技有限公司 | FMCW radar moving and micro-moving target detection and identification method and system |
| WO2024000610A1 (en) * | 2022-06-29 | 2024-01-04 | 珠海正和微芯科技有限公司 | Fmcw radar moving and micro-moving target detection and recognition method and system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP2884299B1 (en) | Speed determination of a target | |
| Jeng et al. | Estimating speed using a side-looking single-radar vehicle detector | |
| US9063225B2 (en) | High resolution Doppler collision avoidance radar | |
| US9791550B2 (en) | Frequency-Modulated-Continuous-Wave (FMCW) radar with timing synchronization | |
| US5483242A (en) | Method for measuring the distance and velocity of objects | |
| US9933518B2 (en) | FMCW radar having distance range graduation | |
| CN108333581B (en) | Multi-undersampled chirp sequence radar | |
| US8334800B2 (en) | On-vehicle radar device | |
| Song et al. | The velocity and range detection using the 2D-FFT scheme for automotive radars | |
| JP2020067455A (en) | Fmcw radar for suppressing disturbing signal | |
| US10473757B2 (en) | Moving target identification without special radar mode | |
| CN110431436B (en) | Method for determining the radial relative acceleration of at least one object and radar device | |
| CN110161472B (en) | Broadband vehicle-mounted millimeter wave radar speed ambiguity resolution method based on signal multiplexing | |
| US20210215816A1 (en) | Radar systems and methods | |
| CN104614723A (en) | Vechicle radar for discriminating false target using variable wave and method for discriminating false target using it | |
| Kuptsov et al. | Features of multi-target detection algorithm for automotive FMCW radar | |
| CN111103580A (en) | Radar signal processing method and device | |
| Wan et al. | Moving target detection using the 2D-FFT algorithm for automotive FMCW radars | |
| CN113866769A (en) | Millimeter wave radar measurement method and device | |
| Son et al. | A novel multi-target detection algorithm for automotive FMCW radar | |
| Fan et al. | Radar waveform design and multi-target detection in vehicular applications | |
| Pandey et al. | Automated parking test using isar images from automotive radar | |
| WO2023142126A1 (en) | Detection apparatus, terminal device, and signal processing method | |
| CN115291202A (en) | FrFT-based target acceleration estimation method and system for vehicle-mounted radar | |
| JP4090513B2 (en) | How to remove ambiguity from distance measurements by radar systems |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |