MIMO radar system with novel phase modulation for suppression of undesirable effects

Abstract

The invention relates to a method for a radar system and to a corresponding radar system for environment detection, comprising a transmitting device having MTX transmitting antennas operating in parallel for transmitting a transmission signal, the transmission signal comprising one or more sequences, the invention relates to a radar system comprising a sequence of individual signals, comprising a phase modulation device for changing the phase of the transmitted individual signals, by means of which different phase changes are carried out on the individual signals for MTX transmitting antennas, referred to as phase modulation, the invention relates to a radar system having a phase modulation device capable of generating at least three different phase values, preferably distributed at least substantially uniformly over a phase single value range 2 [pi], having a receiving device with one or more receiving antennas for receiving a transmission signal reflected on an object, the radar system has a signal processing device for processing the received signal. According to the invention, the phase modulation consists of the sum of a linear phase change, which, if necessary, excludes a phase jump due to a phase single-value range of 2 [pi], and an irregular phase sequence, the linear phase change having different slopes on the transmission signals of the MTX different transmission antennas, the invention is characterized in that the superimposed irregular components are superimposed on the MTX different transmit antennas and are used to separate the components in the received signals caused by the transmit signals of the different transmit antennas, while the superimposed irregular components are identical on the MTX different transmit antennas and are used in particular to reduce or avoid the effects brought about by inaccuracies of the phase modulation means and / or by spectral folding.

Description

Technical Field

[0001] This invention relates to a radar method and a radar system for use in a driver assistance system for motor vehicles. The radar system has multiple transmitting and receiving antennas operating in parallel, a configuration known as MIMO (Multiple-Input Multiple-Output), and employs a novel phase modulation method (or the method according to the invention) that avoids undesirable effects, particularly ghost detection / spurious detection and distortion of measurements. Background Technology

[0002] Motor vehicles are increasingly equipped with driver assistance systems, which use sensor systems to detect the environment and derive automatic vehicle responses and / or instructions from the detected traffic conditions, particularly warnings to the driver. Comfort features and safety features are distinct.

[0003] As a comfort feature, FSRA (Full Speed ​​Range Adaptive Cruise Control) plays an important role in current development. In this mode, the vehicle adjusts its speed to the driver's desired speed whenever traffic conditions permit; otherwise, its speed automatically adapts to the traffic conditions.

[0004] Safety features now come in various forms. In this case, one set of features is used to reduce braking distance or stopping distance in emergency situations, up to autonomous emergency braking. Another set is lane change functionality: it warns the driver or intervenes in steering when the driver wants to make a dangerous lane change, i.e. when a vehicle in the adjacent lane is in the blind spot (called BSD – “Blind Spot Detection”) or is rapidly approaching from behind (LCA – “Lane Change Assist”).

[0005] But now drivers are no longer just assistants; their tasks are increasingly being performed autonomously by the vehicles, meaning that drivers are being replaced more and more; this is known as autonomous driving.

[0006] For systems of the types described above, radar sensors are used, often fused with sensors from other technologies, such as camera sensors. One advantage of radar sensors is their reliable operation even in adverse weather conditions, and their ability to directly measure radial relative velocity of objects via the Doppler effect, in addition to distance. Currently, 77 GHz and 79 GHz are commonly used as transmission frequencies.

[0007] The aforementioned functions require high detection quality, for which accurate angle measurement is absolutely essential. Therefore, MIMO radar is increasingly used, featuring multiple fully parallel transmitting and receiving antennas, utilizing all combinations of these antennas to form the best possible angle. For the parallel operation of the transmitting antennas, the transmitted signals must be modulated differently to separate the components they introduce in the received signal. To this end, patent EP 2 629113 B1 discloses a method using a sequence of single transmitted signals and altering the phase of each individual transmitted signal; for example, binary phase modulation (i.e., only two phase values, 0° and 180°) is shown there, representing either a random sequence or a periodic (especially) alternating process. It is also mentioned that phase modulation can consist of deterministic and random components. When using random phase modulation to distinguish transmitted signals, a disadvantage is that the received signal must be integrated separately over the single transmitted signal sequence for each transmitting antenna, resulting in high costs. This multiple integration avoids the linear phase modulation known in the prior art, in which the rate of change, i.e. the slope of the linear phase change, is different between each transmit antenna; however, this may lead to adverse effects caused by the inaccuracy of the phase modulation device and / or spectral folding. Summary of the Invention

[0008] The object of this invention is to provide an improved phase modulation for MIMO radar systems for motor vehicles, which at least to a large extent suppresses the adverse effects present in current phase modulation.

[0009] This objective is essentially achieved by the method according to claim 1 and the radar system according to claim 7. Advantageous embodiments of the invention are defined in the dependent claims. The core idea here is to superimpose a random phase modulation, identical for all transmitting antennas, onto a known linear phase modulation, wherein the random phase modulation uses more than two phase values ​​(i.e., not binary phase modulation), thereby producing many positive effects, particularly eliminating problems that would otherwise occur; the integration of the received signal over a single transmitted signal sequence can be performed jointly for all transmitting antennas, i.e., only once.

[0010] The advantage of this invention is that it can ensure high detection quality and reduce hardware requirements, especially in terms of the quality of the phase modulation device and the required digital computing power, through the novel phase modulation.

[0011] The radar system involved in the method for environmental detection according to the present invention includes: 1) a transmitting device, said transmitting device having M TXA parallel-operating transmitting antenna for transmitting a signal comprising one or more sequences of K individual signals, wherein the overall / general form of the individual signals is preferably the same or similar; 2) a phase modulation device for changing the phase of the transmitted individual signals, wherein the phase modulation device is used to achieve M-phase modulation on the K individual signals. TX The different phase changes of the transmitting antennas, hereinafter referred to as phase modulation, wherein these phase modulation devices are capable of generating at least three different phase values, which are preferably at least substantially uniformly distributed over a phase single-value range / phase unambiguous range / phase defined range 2π; 3) a receiving device having one or more receiving antennas for receiving the transmitted signal reflected from an object; and 4) a signal processing device for processing the received signal. The key feature of this method is that the phase modulation consists of the sum of a linear phase change—which, if necessary, eliminates phase jumps caused by the phase single-value range 2π—and an irregular phase sequence, wherein the linear phase change in the M... TX The transmitted signals from different transmitting antennas have different slopes, which are used to separate the components in the received signal caused by the transmitted signals from different transmitting antennas, while the superimposed irregular components are in the M... TX The same applies to different transmit antennas and is used in particular to reduce or avoid the effects of inaccuracies in phase modulation devices and / or the effects of spectral folding.

[0012] Advantageously, the superimposed irregular phase sequences can have random or pseudo-random values.

[0013] Furthermore, in a digital signal processing device, integration can be performed over K signals, which are derived from the received signals with respect to the K transmitted signals, wherein the integration is performed only over the signals corresponding to M. TX The signal from each different transmitting antenna is executed once, and the irregular phase components are compensated beforehand.

[0014] An advantageous design of the present invention is characterized in that the integration of the K signals is performed as a discrete Fourier transform, preferably in the form of a fast Fourier transform, wherein the K signals are derived from the received signal for the K transmitted signals, and the components corresponding to different transmit antennas produce power peaks at different positions in the resulting spectrum.

[0015] Advantageously, each transmitted signal can be linearly modulated in frequency, wherein its center frequency changes sequentially / in successively / in steps as necessary, either as an OFDM signal or generated by pseudo-random fast phase modulation.

[0016] Furthermore, the irregular components of phase modulation can also be used to decorrelate the effects of transmission from the receiving antenna due to limited isolation, internal coupling effects, and interference from other radar systems, thereby reducing or avoiding the negative effects. Attached Figure Description

[0017] Figure 1 An exemplary implementation of a radar system is shown.

[0018] Figure 2 The frequency modulation consisting of a frequency ramp sequence is shown.

[0019] Figure 3a The amplitude of the two-dimensional spectrum at the target distance gate j0 is shown, i.e. It does not have random phase modulation components. Figure 3b The case with random phase modulation components is shown; here, the inaccuracies that occur in real phase shifters, namely small phase and amplitude errors, are assumed. Detailed Implementation

[0020] Considering an exemplary implementation of a radar system, the radar system in Figure 1 The diagram is simplified. The radar system has M... TX =3 transmitting antennas TX0-2 and M for transmitting signals RX =Four receiving antennas RX0-RX3 for receiving the transmitted signal reflected from the object; these antennas are implemented as patch antennas using planar technology on a planar circuit board 1.1, wherein the circuit board is oriented relative to the horizontal and vertical directions of the vehicle as shown in the figure and toward the direction of travel. All antennas (transmitting and receiving antennas) have the same radiation characteristics in the elevation and azimuth directions. M RX = The four receiving antennas (and therefore their phase centers, i.e., radiation centers) are each spaced laterally, i.e., horizontally, by a distance d = λ / 2 = 1.96 mm, where λ = c / 76.5 GHz = 3.92 mm is the average wavelength of the signal transmitted in the 76-77 GHz band used, and c = 3 10 8 m / s is the speed of light. Therefore, M TX = The three transmitting antennas are correspondingly spaced four times horizontally, i.e., 4d = 2λ, so all combinations of transmitting and receiving antennas are combined in a grid with a spacing of d = λ / 2 to form a single antenna consisting of M TX ·M RX = An equidistant array consisting of 12 antenna channels, used to determine the azimuth of an object.

[0021] The transmitted signal sent on the transmitting antenna is obtained by a high-frequency oscillator 1.2 in the 76-77 GHz range, the frequency of which can be controlled by a voltage v. Steuer The control voltage is generated in control devices 1.8, which may include, for example, phase-locked loops or digital-to-analog converters. These devices drive the oscillator to change its frequency to correspond to the desired frequency modulation. The phase of the transmitted signal can be adjusted for M via phase shifter 1.3. TX Each transmitting antenna is adjusted and modified individually; the phase shifter achieves 64 phase values ​​with at least an approximately uniform distribution over a single phase range of 2π. Through these phase shifters, the transmitted signals from different transmitting antennas are modulated in different ways, enabling parallel transmission on all transmitting antennas, i.e., enabling MIMO operation, because after demodulation, the components from different transmitting antennas can be separated in the received signal.

[0022] The signals received by the four receiving antennas are down-mixed in parallel in a real-valued mixer 1.4 along with the signal from the oscillator 1.2 to a low-frequency range. These received signals then pass sequentially through a bandpass filter 1.5 with the indicated transfer function, an amplifier 1.6, and an analog-to-digital converter 1.7. They are then further processed in a digital signal processing unit 1.9.

[0023] In order to measure the distance to an object, such as Figure 2 As shown, the high-frequency oscillator and the frequency f of the transmitted signal TX Very rapid linear change (at T) ch = 51.2µs, B ch = 600MHz, where the center frequency f c = 76.5GHz); this is called a frequency ramp (often also known as a "chirp"). The frequency ramp occurs at a fixed grid T D The modulation scheme repeats periodically for 70 µs; there are a total of K = 512 frequency ramps, all with the same frequency profile, i.e., the same frequency slope, the same frequency location (i.e., specifically the same start frequency and center frequency), and the same duration. In recent years, this modulation method has been increasingly adopted and established in radars used for vehicle environment detection. It allows for high sensor detection range and velocity resolution (through longer data acquisition times), as well as high range resolution (through the use of higher modulation bandwidth).

[0024] During each frequency ramp k = 0,…,K-1, each M RX The A / D converter processes the received signal at intervals T. s =25ns (i.e., at 40MHz) l= 2048 samples, where sampling always begins at the same time relative to the start of the ramp (see...). Figure 2 ); in receiving path m RX The sequence obtained from the data has indices i = 0,…, l The digital sample value of -1 is represented as s (i,k,m) RX It is only meaningful to sample the signal within the time interval of the received signal from an object located within the range of interest—therefore, after the ramp begins, at least the propagation time corresponding to the maximum range of interest must be waited (which is 1.33µs at the maximum range of interest of 200m); it should be noted that, here and below, “distance” is always understood as radial distance, and “relative velocity” is understood as its radial component.

[0025] As is known from the prior art (see, for example, EP 2 629 113 B1) and can also be readily deduced, in the case of a single point object at a distance r, the transmitting antenna m TX The sampling signal caused by the transmitted signal (i,k,m) TX ,m RX Let be a sinusoidal oscillation about index i, which can be described very approximately as follows:

[0026] in,

[0027] That is, the frequency of this oscillation is proportional to the distance r from the object (j0 is the normalized frequency). The radial relative motion of the object with respect to the sensor causes a phase term in the sinusoidal oscillation. v (k) varies on a frequency ramp of K = 512; for motion with a constant radial velocity component v, the result is:

[0028] That is, a linear phase change occurs on the frequency ramp k, where the rate of phase change is proportional to the radial relative velocity v of the object. In the above formula (1), the phase term... PM,TX (k,m) TX This describes the phase adjustment achieved using phase shifter 1.3: It has two components: one is a component that varies linearly with the frequency ramp k.

[0029] The different velocity changes p(m) on each launch path. TX) / P, which has an integer common period P and a normalized rate of change p(m) that is treated here as an integer. TX (Normalized relative to the slowest rate of change 1 / P); this component is used to subsequently separate components from different transmission paths in the received signal (see later explanation). Another component is one that varies randomly or pseudo-randomly on the frequency ramp k. PM,r (k), which is identical for all transmit paths, and is generated by randomly selecting from 64 phase values ​​of phase shifter 1.3 for each frequency ramp k; this component according to the invention is used to suppress undesirable effects, which will be derived and explained later. The latter two phase components are independent of frequency ramp k. α,TX (m) TX )and α,RX (m) RX This represents the phase determined by the object's azimuth angle α for different transmission and reception paths. It should also be noted that the actual implemented phase values ​​are in the range of 0…2π, because due to the periodicity of phase, all phase values ​​can be mapped to this range; mathematically, this is a modular arithmetic function.

[0030] Finally, regarding formula (1), it should be noted that it is assumed that the amplitude A of the received signal is independent of the transmission and reception paths, that is, all transmission and reception paths should have the same intensity; this assumption has no impact on the subsequent analysis.

[0031] In the digital signal processing unit 1.9, for the received signal s(i,k,m) RX For each frequency ramp k and each receiver path m RX After multiplying with a suitable window function w1(i), for time indices i = 0,…, l -1 Perform the first Discrete Fourier Transform (DFT) because this transform is equivalent to an optimal filter for the signal form (1); the DFT is preferably implemented using the Fast Fourier Transform (FFT). Using the relation

[0032] Where "exp" represents the exponential function and It is the imaginary unit, which yields the DFT, i.e., the sampled signal generated by the transmission path. Spectrum :

[0033] Where j = 0, ..., l -1 is the running variable for the image range (i.e., the frequency range of the DFT) and represents the so-called range gate (because the frequency of the received signal is proportional to the distance), W1(j) is the spectrum of the window function w1(i) used, and "mod J "" represents the modulus function modulo j. The spectrum W1(j) of the window function has a fairly sharp power peak at j = 0, which extends approximately beyond three frequency values ​​j. Therefore, the spectrum produced by a single object According to formula (6), at frequencies j0 and l There are two power peaks at -j0 (assuming 0 ≤ j0 ≤ l This assumption holds given that the distance is nonnegative and due to the effect of the bandpass filter 1.5. If 0 ≤ j0 ≤ l / 2, then located l The power peak at -j0, i.e., the power peak in the upper half of the spectrum, does not provide additional information. This generally applies to the upper half of the spectrum because this part is a conjugate complex mirror image of the lower half due to the real-valued input signal. Therefore, in subsequent processing, only the lower half of the spectrum is considered, i.e., only the frequency or distance gate j = 0 is considered… l / 2.

[0034] Before a second DFT can be performed on dimension k, the phase modulation must be adjusted according to equation (4a). PM,r random phase components of (k) PM,TX (k,m) TX Compensation is performed (the remaining phase components represent linear phase changes along dimension k, which is necessary for applying DFT as optimal filtering). For the range of interest j0 = 0… l / 2 (i.e., objects within this range), the first term in equation (6) is relevant (because only the lower half of the spectrum j = 0 is considered... l / 2), therefore, in order to compensate for the random phase modulation component, it is necessary to multiply by Thus we get:

[0035] For each distance gate j and receiver path m RX After multiplying with the window function w2(k), a second DFT is then performed, this time along the frequency ramp number k (preferably also implemented via FFT); thus obtaining the two-dimensional spectrum.

[0036] Where l = 0,…,K-1 are the running variables of the image range, i.e., the running variables of the frequency range of the second DFT, and represent the so-called Doppler gate (because frequency is proportional to relative velocity, excluding additional phase modulation components). W 12 (j,l) is the two-dimensional spectrum of the two-dimensional window function w1(i)·w2(k) used (with power peaks at j = 0 and l = 0), and R PM (l) represents a unit vector with random phase variation. Spectrum The values ​​are randomly selected from 32 different phase values ​​uniformly distributed over 2π (the modality of the phase has already been considered here). Therefore, R PM (l) is itself a type of Rayleigh-distributed noise. For the range of the distance gate of interest, j0=0… l The object in / 2, according to formula (8), in the two-dimensional spectrum The first term is in the distance gate j = j0 and the Doppler gate. The power peak appears at j = ; the second term appears at j = l Noise is generated at -j0 (and its immediate vicinity) distributed across all Doppler gates k, where j is located within the range of the desired and considered distance gates j = 0… l / 2 and beyond.

[0037] Now, observe an object above the range of the desired distance gate, that is, at... Within the range; since the transition region of the bandpass filter 1.5 has only relatively low attenuation, it is especially effective slightly above j0 = l Objects with a range of 2 / 2 can also be received—this situation is called exceeding the effective range / overrange. Then, according to formula (8) in the two-dimensional spectrum... In the context of the distance gate, the first term is within the range j = 0… l The power peak occurs at j = j0 above / 2, while the second term now occurs within the range of the desired and considered distance gate, j = 0… l The distance gate j in / 2 = l Noise is generated at -j0, distributed across all Doppler gates k. However, even if this noise is significantly higher than the system noise, it will not lead to detection because detection is only formed for the power peak in dimension k, which is significantly higher than the total noise level there. If no random phase modulation component is present... PM,r (k), then the two-dimensional spectrum The result will be as follows (which can be derived from equations (7) and (8):

[0038] Therefore, it exceeds the effective distance, i.e., the range j0 = ( l / 2+1)...( l The object in -1) will now be passed through the second term within the range of the distance gate j = 0 and considered. l The distance gate j in / 2 = l A power peak is generated at -j0; thus, the detection is incorrectly formed, which not only has an incorrect (too small) distance, but also its relative velocity and angle measurements are incorrect (due to the incorrect sign of the contribution variable in the second term of formula (9)).

[0039] Therefore, through random phase modulation components PM,r (k) prevents false detections due to exceeding the effective distance; the resulting noise is approximately 26 dB lower in average power than the peak power generated without random components (26 dB is due to the integral gain from the DFT 10·log). 10 (K = 512) = 27dB minus approximately 1dB of window function loss. It should also be mentioned that the above considerations do not apply to binary phase shifters, i.e., those with only 0 and π states; because in this case, the phase component 2 in the second term of equation (7) PM,r (k) is always 0 (phase 2π is equivalent to phase 0), thus having no effect, resulting in a two-dimensional spectrum. The second term no longer represents noise, but instead generates a power peak according to formula (9), which then leads to an undesirable over-range effect. Therefore, at least three different phase values ​​are required to convert the over-range effect into noise.

[0040] The problem caused by exceeding the effective distance stems from the folding effect, which maps a frequency to other frequencies; if the frequency still has a certain power component at other frequencies, it is called over-folding—generally, this effect is also known as spectral folding. This over-folding effect exists in very close objects; for example, consider an object at a distance of j0 = 0.5 from the gate (it should be noted that although the bandpass filter 1.5 has high attenuation for such signals, these objects will still produce a strong signal on the receiving antenna due to the close distance, and therefore will still be received). Without random phase modulation components... PM,r (k), then in the two-dimensional spectrum According to equation (9), at the distance gate j = 0, components from both terms will act simultaneously (with a two-dimensional window function spectrum W). 12The power peak of the shape has a certain width, typically extending to three distance gates; the first term provides correct information, while the second term represents incorrect information. These erroneous components of the second term can cause distortion in the object's measurement (if it overlaps with the true component of the first term, then, for example, it affects distance interpolation), or lead to unrealistic detection, i.e., ghost detection (if it does not overlap with the real part of the first term, thus forming an independent power peak). This is achieved through random phase modulation of the components. PM,r (k), according to formula (8) two-dimensional spectrum The second item is noise, so it will not produce ghost detection; since the noise is much lower than the actual peak power of the first item, its effect on the object's measurements (distance, relative speed, and angle) is negligible.

[0041] Therefore, through random phase modulation components PM,r (k) Avoids the negative impact of spectrum folding.

[0042] A fundamental problem with phase modulation is that the devices used for this purpose, particularly phase shifters, are never ideal; they always contain some degree of error. The 64 phase values ​​of the phase shifter considered here (ideally uniformly distributed over a phase range of 2π = 360°) should have a standard deviation of 5°; furthermore, the amplitude of the realized phasor should also have a standard deviation of 10%. The modulation period used is set to P = 4, and for the considered transmission path m... TX Modulation change rate p (m TX = 1. Without random modulation components, according to equation (4b), four target phase values ​​of 0°, 90°, 180°, and 270° are periodically repeated, generated by phase shifter numbers 0, 16, 32, and 48; their corresponding actual phase values ​​are -5°, 91°, 185°, and 263°, with amplitude values ​​of 1.02, 1.1, 0.85, and 1.11, respectively. For a distance gate j0 < l / 2 and the object at the Doppler gate l0 = 72, thus obtaining the two-dimensional spectrum of the object at a distance j0 from the gate, i.e. ,exist Figure 3a It is expressed in amplitude form and in dB; except in In addition to the regular power peaks, other power peaks (harmonic frequencies with period P = 4) appear at grid positions with an interval of K / P = 128. These power peaks are generated by non-ideal phase shifter phase values ​​and their periodic repetition, and may lead to false detections, i.e., ghost detection. If the harmonics fall on the correct power peaks of other transmit antennas, they may distort the angle forming results. It should also be mentioned that in Figure 3a In the above formula, the noise that is significantly lower than the power peak comes from the system noise that is not shown.

[0043] When using phase modulation according to formula (4a) PM,TX (k,m) TX The phase components of the random superposition according to the present invention PM,r At (k), the four phase values ​​are no longer repeated periodically, but quasi-random phase values ​​are used (linear phase components are no longer visible); therefore, the phase modulation error (phase and amplitude) is no longer periodic, but quasi-random, making it possible to determine the phase modulation error based on the given information. Figure 3b Spectrum The power peaks generated by harmonics no longer appear—their energy is dispersed into the noise. Therefore, the superimposed random phase modulation components... PM,r (k) It avoids ghost detection caused by the inaccuracies that always occur in phase modulation devices, and thus also allows the use of fairly poor phase shifters, which can reduce costs.

[0044] In addition to the previously described random phase modulation component PM,r In addition to the advantages of (k), it also causes the transmission of the receiving antenna (due to its limited TX isolation), the internal coupling between the transmit and receive paths, and interference from other radar systems to be decorrelated and thus converted into noise—therefore it does not significantly degrade the quality of object measurements or produce ghost detection.

[0045] So far, only m has been considered accordingly. TX Contribution of the launch path. Derived by all M TX = The total two-dimensional spectrum S2(j,l,m) generated by the three transmission paths RX ) is the sum of each individual contribution shown in the above formula (i.e., for m) TX = 0,…,M TX -1 summation). Because of the random phase modulation components PM,r (k) in all M TX Since the modulation is constant across the three transmit paths, the compensation and second DFT only need to be calculated once for all transmit paths, i.e., it does not need to be calculated separately for each transmit path (if the random phase modulation components between transmit paths are different, they must be calculated separately, which would significantly increase the computational workload). The modulation used to distinguish transmit paths refers to the different linear phase variations between transmit paths. PM,lin (k,m) TXThis also eliminates the need for multiple second DFTs because it doesn't require prior compensation; without compensation, it would only cause a corresponding shift in the power peak during the DFT. After performing this second DFT jointly (i.e., only once) on all transmit paths, M will be obtained at the position corresponding to each transmit path (i.e., its linear phase change). TX Each power peak; this allows for the separation of components caused by different transmission paths, which is necessary for MIMO operation (i.e., angle forming using all combinations of transmit and receive antennas when the transmit antennas are running in parallel). Of course, the aforementioned random phase modulation components... PM,r The advantages and effects of (k) are also retained in all M. TX = The total spectrum of the 3 transmission paths (which applies to each individual transmission path, and therefore also to their sum).

[0046] So far, only individual point objects have been considered. The above analysis still applies even in the case of multiple and / or extended objects (because this only implies a linear superposition of multiple single signals).

[0047] The radar system previously considered has multiple receiving antennas, and therefore multiple receiving paths; of course, it is possible to have only one receiving antenna, but this is usually disadvantageous (poor angle formation and unbalanced use of hardware resources, i.e., not balanced, because the implementation of the transmission path is complex).

[0048] So far, real-valued mixers have been considered. For complex-valued mixers (also known as IQ mixers), ideally there is only one power peak; however, in reality, IQ generation is not perfect, resulting in smaller power peaks even at negative frequencies, which can lead to ghost detection or distortion of measurements. This is due to random phase modulation components. PM,r (k) The power peak is also converted into noise, thus avoiding the negative effects that result.

[0049] According to Figure 2 In the modulation, all frequency ramps have the same frequency position, i.e., the starting frequency (and therefore the same center frequency). To improve distance resolution, as described in DE 10 2020 210 079 B3, the starting frequency can vary linearly along the frequency ramps, wherein the distance between the frequency ramps preferably also varies linearly. This has no effect on the phase modulation according to the invention and its advantages, and therefore it remains unchanged.

[0050] Up to now, a linear frequency ramp has been considered to be a sequentially repeating transmitted signal. However, other signal forms can be used instead of a frequency ramp, such as signals with pseudo-random binary phase modulation (i.e., symbols within the signal change very rapidly in a pseudo-random manner) or OFDM signals (OFDM = Orthogonal Frequency Division Multiplexing). Then, the sampled values ​​cannot be directly used (after analog-to-digital conversion) as input values ​​for the first DFT described above; instead, the Fourier transform values ​​for each transmitted signal and receiving antenna must first be calculated and divided by the spectrum of the transmitted signal.

[0051] Finally, it should be noted that it will be obvious to those skilled in the art how the concepts and embodiments of the present invention, as illustrated in the above application examples, can be applied to common dimensional and parameter designs; that is, they can also be applied to other values.

Claims

1. A method for using a radar system for environmental detection, the radar system comprising: - A launching device, the launching device having M TX A parallel-operating transmitting antenna is used to transmit a signal, which includes one or more sequences, each sequence consisting of K individual signals, preferably having the same or similar overall form. - A phase modulation device for changing the phase of a transmitted single signal, wherein the phase modulation device achieves M on K single signals. TX Different phase changes of the transmitting antenna, hereinafter referred to as phase modulation, wherein the phase modulation device is capable of generating at least three different phase values, which are preferably at least substantially uniformly distributed over a single phase value range of 2π. - A receiving device having one or more receiving antennas, the receiving device being used to receive a transmitted signal reflected from an object. - and signal processing apparatus for processing the received signals, The characteristic feature is that the phase modulation consists of a linear phase change—excluding phase jumps due to a single-valued phase range of 2π if necessary—and an irregular phase sequence, wherein the linear phase change is in M TX The transmitted signals from different transmitting antennas have different slopes and are used to separate the components in the received signal caused by the transmitted signals from different transmitting antennas, while the superimposed irregular components are in the M... TX The same applies to different transmit antennas and is used in particular to reduce or avoid the effects of inaccuracies in phase modulation devices and / or the effects of spectral folding.

2. The method according to claim 1, wherein, The superimposed irregular phase sequences have random or pseudo-random values.

3. The method according to any one of the preceding claims, wherein, In a digital signal processing device, K signals are integrated, which are obtained from the received signals with respect to K transmitted signals, wherein the integration is performed only on signals corresponding to M. TX The signal from each different transmitting antenna is executed once, and the irregular phase components are compensated beforehand.

4. The method according to claim 3, wherein, The integration of the K signals obtained from the received signals for the K transmitted signals is performed as a discrete Fourier transform, preferably in the form of a fast Fourier transform. The components corresponding to different transmit antennas cause power peaks at different locations in the resulting spectrum.

5. The method according to any one of the preceding claims, wherein, Each transmitted signal is linearly modulated in frequency, wherein its center frequency changes sequentially as necessary, either as an OFDM signal or generated by pseudo-random fast phase modulation.

6. The method according to any one of the preceding claims, wherein, The irregular components of phase modulation are also used to decorrelate the effects of transmission from the receiving antenna due to limited isolation, internal coupling effects, and interference from other radar systems, thereby reducing or avoiding the negative effects.

7. A radar system for environmental detection, comprising: - A launching device, the launching device having M TX A parallel-operating transmitting antenna is used to transmit a signal, which includes one or more sequences, each sequence consisting of K individual signals, preferably having the same or similar overall form. - A phase modulation device for changing the phase of a transmitted single signal, wherein the phase modulation device achieves M on K single signals. TX Different phase changes of the transmitting antenna, hereinafter referred to as phase modulation, wherein the phase modulation device is capable of generating at least three different phase values, which are preferably at least substantially uniformly distributed over a single phase value range of 2π. - A receiving device having one or more receiving antennas, the receiving device being used to receive a transmitted signal reflected from an object. - and signal processing apparatus for processing the received signals, Its features are, The phase modulation consists of a linear phase change—excluding phase jumps due to the single-valued phase range of 2π where necessary—and an irregular phase sequence, wherein the linear phase change is in M TX The transmitted signals from different transmitting antennas have different slopes and are used to separate the components in the received signal caused by the transmitted signals from different transmitting antennas, while the superimposed irregular components are in the M... TX The same applies to different transmit antennas and is used in particular to reduce or avoid the effects of inaccuracies in phase modulation devices and / or the effects of spectral folding.

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