Radar system

Abstract

This disclosure relates to a Doppler frequency division multiplexing (DDM) MIMO radar system. An example embodiment includes a Doppler frequency division multiplexing (DDM) MIMO radar system (400) comprising: a transmitter (401) that transmits signals via different electrical lengths (L... 1‑N ) corresponding to multiple signal paths (403) 1‑N ) connected to multiple transmitter antennas (402) 1‑N ), such that the phase of the signal transmitted by the transmitter (401) is such that the phase of the signal transmitted by the plurality of transmitter antennas (402) is such that the phase of the signal transmitted by the transmitter (401) is such that the phase of the signal transmitted by the transmitter antenna (402) is such that the phase of the signal transmitted by the transmitter antenna (401 ... 1‑N The difference is at each transmitter antenna in the )

Description

Technical Field

[0001] This disclosure relates to a Doppler frequency division multiplexing MIMO radar system. Background Technology

[0002] Modern automotive radar systems require high angular resolution. This can be achieved in different ways. One approach is to use a phased-array antenna and perform beamforming, where multiple transmitters combine different phases to control the beam. A second approach is to implement a multiple-input multiple-output (MIMO) radar to create a virtual antenna. However, both strategies require a system with multiple transmitters and receivers. This leads to a situation where the area, power consumption, and power dissipation required to implement such a system on a monolithic scale eventually decrease as the number of channels required increases, resulting in higher angular resolution.

[0003] For MIMO radar systems, orthogonal signals are required for each transmitter channel in order to reconstruct information at the receiver. In automotive radar, one way to achieve orthogonality between channels is to use Doppler domain multiplexing (DDM) technology. In DDM, frequency-modulated signals are used and frequency increments are generated between transmitter channels. Each channel can be identified at the receiver because it will fall within a different frequency band in the Doppler spectrum. One way to generate incremental frequencies between channels is by changing the phase from linear frequency-modulated pulses to linear frequency-modulated pulses with a defined sequence. To achieve this, a phase rotator is needed at the transmitter.

[0004] One problem with existing DDM MIMO radars is the need for multiple transmitter channels, which occupies more space and increases system cost and power consumption. Another issue is the difficulty in precisely controlling the phase shift between transmitter channels using digital technology. Summary of the Invention

[0005] According to a first aspect, a Doppler frequency division multiplexing (DDM) and multiple input multiple output (MIMO) radar system is provided, comprising a transmitter connected to a plurality of transmitter antennas via corresponding multiple signal paths of different electrical lengths, such that the phase of the signal transmitted by the transmitter is different at each of the plurality of transmitter antennas.

[0006] The transmitter can be configured to generate a series of M linearly frequency-modulated pulses in a radar periodic frame provided to each of the plurality of N transmitter antennas. Each of the N signal paths can have a length L. n This makes the phase difference between the m-th linear frequency modulated pulse in the radar periodic frame at the n-th antenna and the m-th linear frequency modulated pulse at the first antenna equal to (m-1)(n-1)*360 / N.

[0007] The length L1 of the first signal path among the N signal paths can be equal to A. m1 λ m A m1 It is an integer, and λ m It is the wavelength of the center frequency of the m-th linear frequency modulated pulse in the radar periodic frame.

[0008] The length difference between the nth signal path and the first signal path among the N signal paths can be equal to Xnλ. n +(n-1)(n-1)λ n / n, where X n It is an integer corresponding to the number of antennas.

[0009] Each of the M linear frequency modulated pulses in the series has a center frequency, and the change in the center frequency between consecutive linear frequency modulated pulses can be a frequency difference ΔF.

[0010] According to a second aspect, a method for designing a DDM MIMO radar system is provided, the DDM MIMO radar system having N antennas, the N antennas being connected via a length of L 1-N The method comprises connecting N signal paths to the transmitter, wherein the method includes:

[0011] Defined frequency difference ΔF and having wavelength λ 1-M A series of M frequencies;

[0012] Determine the length L1 of the first signal path among the N signal paths;

[0013] The length difference between the first signal path and the nth signal path among the N signal paths is determined as Xnλ. n +(n-1)(n-1)λ n / n, where X n It is an integer.

[0014] In some examples, the length of the first signal path among the N signal paths can be determined as A. m1 λ m A m1 It is an integer, and λ m It is the wavelength of the m-th frequency in the series of M frequencies. In this example, the phase difference at the first antenna will be zero. In other examples, the length of the first signal path can be determined as arbitrary, and the difference between said length and the other lengths can be determined. Then, by rotating the phase of the transmitter's output during operation, the phase at the first antenna can be selected to be zero.

[0015] According to a third aspect, a method is provided for operating a Doppler frequency division multiplexing (DDM) and multiple-input multiple-output (MIMO) radar system, the radar system including a transmitter connected to a plurality of N transmitter antennas via corresponding multiple signal paths of different electrical lengths, the method including the transmitter generating a series of M linear frequency modulated pulses in a radar periodic frame provided to each of the plurality of N antennas.

[0016] Each of the N signal paths can have a length L. n This ensures that the phase difference between the m-th linear frequency modulated pulse in the radar periodic frame at the n-th antenna and the m-th linear frequency modulated pulse at the first antenna is equal to (m-1)(n-1)*360 / N. Other features related to the first aspect can also be applied to the method of the second aspect.

[0017] According to the first aspect, a transmitter is connected to multiple antennas with feed structures of different electrical lengths, and the center frequency of the linear frequency modulated (LFM) pulse is changed from one LFM pulse to another. This combination generates a phase difference between the LFM pulse and the antennas, simultaneously producing the effect required to encode each transmit channel in different Doppler bands. In this way, only one TX channel is needed to establish the MIMO system. This reduces energy, power dissipation, and chip area. An additional advantage is that the phase shift of each transmitter can be precisely designed compared to phase shifters in conventional RF chips, which are digitally controlled and tend to have large error values ​​(typically ±6°) that degrade radar system performance. By using waveguides of different lengths, the phase shift (and therefore the frequency offset of each transmitter) can be precisely set, resulting in better performance and a closer approximation to the simulation model of the Doppler frequency division multiplexing algorithm.

[0018] These and other aspects of the invention will become apparent from the embodiments described below, and will be illustrated with reference to the embodiments described below. Attached Figure Description

[0019] The embodiments will be described by way of example only with reference to the accompanying drawings, in which:

[0020] Figure 1 This is a schematic diagram of Doppler domain multiplexing of three channels;

[0021] Figure 2 This is a schematic diagram of a series of linear frequency modulated pulses from the transmitter in a radar periodic frame;

[0022] Figure 3 It is a two-dimensional FFT representation used for the three transmission channels;

[0023] Figure 4 This is a schematic diagram of an example MIMO radar system;

[0024] Figure 5 This is a schematic diagram of N transmitted signals on N transmission channels, where each channel includes M linear frequency modulated pulses;

[0025] Figure 6 The image shows antenna feed lines of different lengths.

[0026] Figure 7 Different antenna feeds are further shown; and

[0027] Figure 8 This is a flowchart illustrating an example method for designing a DDM MIMO radar system.

[0028] It should be noted that the figures are illustrative and not drawn to scale. For clarity and convenience, the relative dimensions and proportions of the parts in these figures have been enlarged or reduced. In modified and different embodiments, the same reference numerals are generally used to refer to corresponding or similar features. Detailed Implementation

[0029] In Doppler domain multiplexing, a frequency difference (or Δf) is provided between multiple channels. Δf needs to be large enough to locate each channel in different bandwidths. Figure 1 An example Doppler spectrum is schematically shown, in which three transmission channels TX1, TX2, and TX3 are separated by a velocity difference Δv in the spectrum.

[0030] To achieve Doppler separation between channels, one approach is to change the phase of each channel between linear frequency modulated pulses (chirps, bird calls) within a defined sequence. To achieve a Doppler separation equal to Δf... 多普勒 The channel separation and phase shift can be expressed as:

[0031]

[0032] Where PRI is the pulse repetition interval, M is the number of linear frequency modulated pulses (chirp, bird call signal), and N is the number of channels.

[0033] Considering the case of one transmitter driving three antennas, the orthogonal codes of the continuous linear frequency modulated pulses for each transmit channel are shown in Table 1 below. Channel TX1 maintains zero-phase modulation, while channels TX2 and TX3 alternate between 120° and 240°.

[0034] Table 1: Orthogonal codes of phase-modulated continuous linear frequency modulation pulses for three transmission channels.

[0035]

[0036] Figure 2 The diagram shows an example sequence of linear frequency modulated pulses (chirps, bird calls) on a radar periodic frame, wherein N consecutive linear frequency modulated pulses (chirps) are transmitted in each transmit channel TX1, TX2, TX3 on the radar periodic frame. 1-N For each linear frequency modulated pulse, a frequency shift Δf is introduced. n , where n ranges from 1 to N.

[0037] The phase modulation of a continuous linear frequency modulated pulse produces a shift in the Doppler domain, making it easier to extract different transmission channels. Regarding the relationship between the range and velocity of the three transmission channels TX1, TX2, and TX3... Figure 3 The representation of a two-dimensional FFT is shown.

[0038] Instead of using multiple transmitters, the phase difference between channels and between consecutive linear frequency modulated pulses can be generated using the relationship between the length of the feed structure of each antenna and the center frequency of each linear frequency modulated pulse. In this way, a MIMO radar system can be created by connecting one transmitter to multiple antennas.

[0039] Figure 4 An example MIMO radar system 400 is shown, which has multiple signal paths 403. 1-N To multiple antennas 402 1-N A single transmitter 401 provides the signal. Each signal path 403 1-N Length L 1-N Depending on what is provided to each antenna 402 1-N The required phase difference for the signal. N is the number of signal paths and the corresponding number of antennas and transmitted signals.

[0040] Figure 5 The diagram schematically illustrates N transmitted signals TX1-TXN, each consisting of M linear frequency modulated (LFM) pulses (chirps, bird calls), i.e., LFM pulse 1 to LFM pulse M. The frequency shift of consecutive LFM pulses in each transmitted signal causes the LFM pulse M in each transmitted signal to shift by ΔF(m-1), where ΔF is the shift between consecutive LFM pulses, and m is an integer from 1 to M. Each LFM pulse also has a phase shift of (m-1)(n-1)*360° / N, where n is an integer from 1 to N. Table 2 below summarizes the antenna feeds L1 to L... N The length and the center frequency F1 to F M The relationship between the linear frequency modulation pulses 1 to M provided to each antenna is given.

[0041] The first antenna feed line 4031 should have a 0° phase shift signal, and therefore its length L1 should be equal to a multiple of the wavelength of all frequencies used, i.e.:

[0042] L1 = A 11 λ1=A 21 λ2=A 31 λ3=A N1 λ N

[0043] Where A XY It is an integer value that is assigned to provide the alignment phase between channels at different frequencies.

[0044] The second antenna feed line 4032 should also be a continuous frequency, that is, provide a progressive phase shift at frequencies such as +λ2 / N, 2λ3 / N, and 3λ4 / N.

[0045]

[0046] Applying phase-shift boundary conditions to the remaining antenna feeds provides a complete set of equations required for system design. The design process can begin by defining the frequencies to be used with different linear frequency modulated pulses, and then finding integer values ​​that satisfy all the required relationships.

[0047] Table 3 provides a set of relationships indicating the length difference between each antenna feed line in terms of the wavelength of the linear frequency modulated pulse center frequency. For antenna feed line 403 1-N The lengths and differences in Tables 1 and 2 are in Figure 6 It is shown graphically in the middle.

[0048] For L1: and and

[0049] For L2-L1:

[0050]

[0051]

[0052]

[0053] For L N -L1:

[0054]

[0055]

[0056]

[0057] Table 2: Calculation of the equivalent length of N antenna feed lines

[0058]

[0059]

[0060] Table 3: Calculation of the equivalent length of N antenna feed lines

[0061]

[0062] Practical design environments may not allow sufficient flexibility to select the length of each antenna feeder. Therefore, to simplify the design, any length can be used instead of length L1. Due to the introduction of frequency shift, i.e., the point in the waveguide used to define the phase within and between channels, a phase mismatch occurs at the end of L1 between linear frequency modulated pulses in reference scheme 701. The phase reference scheme at the end of L1 can be adjusted by using a TX phase rotator. Figure 7 Schematic illustration of a length L 1-N A series of antenna feed lines 703 1-N .

[0063] Tables 4, 5, and 6 below indicate the phase extraction at reference plan 701. Table 4 indicates the phases using L1 in the reference plan. Table 5 indicates the phases of arbitrary length L in the reference plan. Z The phase. Table 6 indicates L with opposite phase rotation in the reference plan. Z The phases are: F1 is E°, F2 is F°, and F3 is G°.

[0064] Table 5: Phase extraction of antenna feed line length L1 at the reference plan.

[0065]

[0066] Table 6: Reference Plan for Arbitrary Length L Z Phase extraction.

[0067]

[0068] Table 7: Arbitrary length L with opposite phase rotator correction at the reference plan location Z Phase extraction.

[0069]

[0070] To employ the example embodiment where N=2, i.e., a single transmitter drives only two antennas, the first step is to define the frequency difference ΔF between consecutive linear frequency modulated pulses. In this example, ΔF is defined as 5%. The value of ΔF can then be input into the equation mentioned above, and the resulting calculation is:

[0071] f2 = 1.05f1

[0072]

[0073]

[0074] The result is:

[0075]

[0076] Because there are two unknowns and only one relationship exists between B1 and B2, this equation has multiple solutions. Assuming B1 and B2 are integers, the minimum solution to the design constraint is B1 = 10 and B2 = 10. The result is:

[0077] L1=100λ1=105λ2

[0078]

[0079] This provides some key constraints for hardware design. The simplification concept described above can be applied to significantly reduce the different lengths L1 and L2, the difference being that the increment L for the described concept is fixed and required.

[0080] L Z =10λ1=10.5λ2

[0081] Therefore, we must determine a new phase for both frequencies f1 and f2.

[0082] For f1, L1-L Z =100λ1-10λ1=90λ1

[0083] This is an integer of λ, so the reference phase remains 0°.

[0084] For f2, L1-L Z =105λ² - 10.5λ² = 94.5λ²

[0085] This is an integer of λ plus one-half, so the reference phase is 180°.

[0086] Between frequencies f1 and f2, the TX phase must be shifted by 180° to maintain phase consistency of the system.

[0087] Figure 8 It shows the design Figure 4 A flowchart illustrating an example method for a DDM MIMO radar system 400, where system 400 has N antennas 402. 1-N The N antennas 402 1-N Via length L1-N N signal paths 403 1-N Connected to transmitter 401. In the first step 801, a frequency difference ΔF is defined and a wavelength λ is defined. 1-M A series of M frequencies. These frequencies define the center frequencies of a series of linear frequency modulated pulses (chirps, bird calls) to be transmitted in each radar period frame. In the second step 802, N signal paths 403 are determined. 1-N The length L1 of the first signal path 4031 in the diagram. The length L1 can be arbitrarily determined, or it can be determined as A. m1 λ m A m1 It is an integer, and λ m It is the wavelength of the m-th frequency in a series of M frequencies. In the third step 803, N signal paths 403 are determined. 1-N The length difference between the first signal path 4031 and the nth signal path is Xnλ n +(n-1)(n-1)λ n / n, where X n It is an integer. This defines the length of each signal path between the transmitter and the N antennas, such that the phase of the signal transmitted by transmitter 401 varies across the multiple transmitter antennas 402. 1-N Each transmitter antenna is different.

[0088] By reading this disclosure, those skilled in the art will understand other variations and modifications. Such variations and modifications may involve equivalents and other features known in the field of memory systems and that can be used in place of or in addition to the features described herein.

[0089] Although the appended claims are directed to specific combinations of features, it should be understood that the scope of the disclosure of this invention also includes any novel feature or combination of novel features or any generalized form thereof explicitly or implicitly disclosed herein, regardless of whether the novel feature relates to the same invention as claimed in any of the present claims or whether the novel feature alleviates the same technical problem as any or all of the technical problems alleviated by this invention.

[0090] Features described in the context of a single embodiment may also be provided in combination in a single embodiment. Conversely, for the sake of brevity, various features described in the context of a single embodiment may also be provided individually or in any suitable sub-combination. The applicant hereby reminds that new claims may be made for such features and / or combinations of such features during the examination of this application or any other application derived therefrom.

[0091] For the sake of completeness, it is also specified that the term "comprising" does not exclude other elements or steps, the terms "a" or "an" do not exclude that a plurality of, a single processor or other unit may perform the functions of the several components described in the claims, and the reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A Doppler Frequency Division Multiplexing (DDM) and Multiple Input Multiple Output (MIMO) radar system (400), characterized in that, Includes a transmitter (401), said transmitter (401) via different lengths (L) 1-N The corresponding multiple signal paths (403) 1-N ) connected to multiple transmitter antennas (402) 1-N ), so that the phase of the signal transmitted by the transmitter (401) is such that the phase of the signal transmitted by the transmitter (402) is such ... 1-N The difference lies at each transmitter antenna in the diagram; in The transmitter (401) is configured to provide power to the plurality of transmitter antennas (402). 1-N Each transmitter antenna in the radar periodic frame generates a series of M linear frequency modulated pulses; The length difference between the nth signal path and the first signal path among the N signal paths is equal to X. n λ n +(n-1)(n-1)λ n / n, where X n It is an integer corresponding to the number of each antenna; and Each of the M linear frequency modulated pulses in the series has a center frequency, and the change in the center frequency between consecutive linear frequency modulated pulses can be a frequency difference ΔF.

2. The radar system (400) according to claim 1, characterized in that, Each of the N signal paths has a length L. n The phase difference between the m-th linear frequency modulated pulse in the radar periodic frame at the n-th antenna and the m-th linear frequency modulated pulse at the first antenna is equal to (m-1)(n-1)*360 / N.

3. A method for designing a DDM MIMO radar system, said DDM MIMO radar system having N antennas (402... 1-N The N antennas are connected by a length of L. 1-N N signal paths (403) 1-N ) is connected to the transmitter (401), characterized in that, The method includes: Defined frequency difference ΔF and having wavelength λ 1-M A series of M frequencies; Determine the N signal paths (403) 1-N The length L1 of the first signal path (4031) in the signal path is L1; The N signal paths (403) 1-N The length difference between the first signal path (4031) and the nth signal path in the equation is determined as X. n λ n +(n-1)(n-1)λ n / n, where X n It is an integer.

4. The method according to claim 3, characterized in that, The N signal paths (403) 1-N The length L1 of the first signal path (4031) in the diagram is determined to be A. m1 λ m A m1 It is an integer, and λ m It is the wavelength of the m-th frequency in the series of M frequencies.

5. A method for operating a Doppler frequency division multiplexing (DDM) and multiple input multiple output (MIMO) radar system (400), the radar system comprising a transmitter (401) that transmits signals via different electrical lengths (L... 1-N The corresponding multiple signal paths (403) 1-N ) connected to N transmitter antennas (402 1-N ), characterized in that, The method includes the transmitter (401) providing power to N antennas (402). 1-N Each antenna in the radar periodic frame generates a series of M linear frequency modulated pulses; in The length difference between the nth signal path and the first signal path among the N signal paths is equal to X. n λ n +(n-1)(n-1)λ n / n, where X n It is an integer corresponding to the number of each antenna; and Each of the M linear frequency modulated pulses in the series has a center frequency, and the change in the center frequency between consecutive linear frequency modulated pulses can be a frequency difference ΔF.

6. The method according to claim 5, characterized in that, Each of the N signal paths has a length L. n This makes the phase difference between the m-th linear frequency modulated pulse in the radar periodic frame at the n-th antenna and the m-th linear frequency modulated pulse at the first antenna equal to (m-1)(n-1)*360 / N.

7. The method according to claim 5 or claim 6, characterized in that, The length L1 of the first signal path among the N signal paths is equal to A. m1 λ m A m1 It is an integer, and λ m It is the wavelength of the center frequency of the m-th linear frequency modulated pulse in the radar periodic frame.

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