FMCW radar with additional AM for jamming detection

Abstract

Method for a radar device comprising: generating an RF oscillator signal (sLO(t)) containing a chirp sequence with frequency-modulated chirps; amplitude-modulating the RF oscillator signal (sLO(t)) by a modulation signal (sAM(t)), wherein each chirp of the chirp sequence is amplitude-modulated by the modulation signal (sAM(t)) representing a unique identification code (ID) of the radar device; transmitting the amplitude-modulated RF oscillator signal (sLO,AM(t)) via at least one antenna; receiving an RF signal (yHF(t)) containing frequency-modulated chirp echo signals from a target (T); downconverting the received RF signal (yHF(t)) to a baseband using the RF oscillator signal (sLO(t)) and thus Providing a baseband signal (y(t)); and processing the baseband signal (y(t)) to detect information contained in the modulation signal (sAM(t)).

Description

TECHNICAL AREA

[0001] The present disclosure relates to the field of radar sensors, in particular radar detection techniques that allow interference detection and / or suppression. BACKGROUND

[0002] Radar sensors are found in numerous detection applications that measure the distance and speed of objects. In the automotive sector, there is a growing demand for radar sensors used in advanced driver-assistance systems (ADAS). Examples of ADAS include adaptive cruise control (ACC and radar cruise control). These systems can automatically adjust a vehicle's speed to maintain a safe distance from other vehicles ahead. Blind spot monitors, which use radar sensors to detect other vehicles in a vehicle's blind spot, are another example of ADAS.Autonomous vehicles, in particular, can use numerous sensors, such as radar sensors, to detect and locate objects in their environment. Information about the position and speed of objects within the autonomous vehicle's range is used to assist in safe driving.

[0003] Modern radar systems use highly integrated RF circuits that can integrate all the core functions of a radar transceiver's RF front end into a single package (single-chip transceiver). Such RF front ends typically include a local RF oscillator (LO), power amplifiers (PA), low-noise amplifiers (LNA), and a mixer. Frequency-modulated continuous-wave (FMCW) radar systems use radar signals whose frequency is modulated by ramping up and down the signal frequency. These radar signals are often referred to as "chirp signals" or simply "chirps." In the case of linear chirp signals, the term "LFM signals" is sometimes used, where LFM stands for "linear frequency modulation."A radar sensor typically emits sequences of chirps using one or more antennas, and the emitted signal is backscattered by one or more objects (called radar targets) within the radar sensor's "field of view." The backscattered signals (radar echoes) are received and processed by the radar sensor. Detection of the radar targets is usually achieved using digital signal processing.

[0004] As more and more cars are equipped with radar sensors, interference becomes an issue. This means that the radar signal emitted by a first radar sensor (installed in a car) can interfere with the receiving antenna of a second radar sensor (installed in another car) and disrupt its operation.

[0005] This document describes a method for use in a radar system. According to one embodiment, the method includes generating an RF oscillator signal containing frequency-modulated chirps, amplitude-modulating the RF oscillator signal by a modulation signal, and transmitting the amplitude-modulated RF oscillator signal via at least one antenna. In another embodiment, the method further includes receiving an RF signal containing frequency-modulated chirp echo signals from a target, down-converting the received RF signal to a baseband using the RF oscillator signal to provide a baseband signal, and processing the baseband signal to detect information contained in the modulation signal.

[0006] Furthermore, a radar system is described here. According to one embodiment, the radar system includes an RF oscillator configured to generate an RF oscillator signal containing frequency-modulated chirps; a modulator that receives the RF oscillator signal and a modulation signal and is configured to amplitude-modulate the RF oscillator signal with the modulation signal; the radar system further includes one or more antennas configured to transmit the amplitude-modulated RF oscillator signal and to receive an RF signal containing frequency-modulated chirp echo signals from a target; a mixer that receives the RF oscillator signal and the received RF signal and is configured to down-convert the RF signal to a baseband to provide a corresponding baseband signal; and an analog-to-digital converter configured to digitize the baseband signal.A processing unit is designed to process the baseband signal and detect information contained in the modulation signal. List of characters

[0007] The invention can be better understood with reference to the following drawings and descriptions. The components in the figures are not necessarily to scale; instead, the emphasis has been placed on illustrating the principles of the invention. In the figures, identical reference numerals denote corresponding parts. Regarding the drawings: Fig. Figure 1 is a sketch illustrating the operation of an FMCW radar system for distance and / or speed measurement. Fig. Figure 2 contains two time-course diagrams illustrating the frequency modulation of the RF signal used in FMCW radar systems. Fig. Figure 3 illustrates an example of how interference is introduced onto the receiver of a radar sensor. Fig. Figure 4 is a time-history diagram illustrating a sequence of chirps used for data acquisition in a radar sensor. Fig. Figure 5 illustrates in a time-course diagram a transmitted signal from a radar sensor and an interference signal from a jammer, where the frequency-over-time curves of these signals overlap at least partially. Fig. Figure 6 illustrates an example curve that includes a radar signal (after downconversion to the baseband), including a radar echo from a target and the in Fig. 5 interferences shown. Fig. Figure 7 is a diagram illustrating how interference can lead to the detection of so-called "ghost targets". Fig. Figure 8 is a block diagram illustrating the basic structure of an FMCW radar system. Fig. Figure 9 is a circuit diagram illustrating an example of an analog RF front end of a radar sensor and an analog RF front end of a jammer. Fig. Figure 10 is a diagram illustrating the curve of an example of an amplitude-modulated chirp signal. Fig. Figure 11 illustrates various examples of binary modulation signals used to modulate the amplitude of a chirp. Fig. Figure 12 illustrates the concept of range Doppler signal processing, as commonly used in radar sensors. Fig. Figure 13 is a circuit diagram illustrating a configuration of a radar transceiver designed to generate and process amplitude-modulated chirp signals. Fig. Figure 14 is a diagram illustrating an example spectrum of the baseband digital radar signal obtained from an amplitude-modulated chirp echo, containing three peaks corresponding to three radar targets. Fig. Figure 15 illustrates an example of a quaternary modulation signal that can be used to generate an amplitude-modulated chirp signal using quaternary ASK. Fig. 16 is a diagram similar to Fig. Figure 14 illustrates an example spectrum of the baseband digital radar signal obtained from an amplitude-modulated chirp echo when single-sideband modulation is obtained. Fig. Figure 17 is a diagram illustrating the achievable resolution for different code lengths and different amplitude modulation methods. The Fig. 18 and Fig. 19 are flowcharts illustrating example configurations of procedures used in radar systems for identifying ghost echoes. DETAILED DESCRIPTION

[0008] Fig. Figure 1 illustrates a conventional frequency-modulated continuous wave (FMCW) radar sensor 1. In the present example, separate transmit (TX) and receive (RX) antennas 5 and 6, respectively, are used (bi-static or pseudo-monostatic radar configuration). However, it should be noted that a single antenna can be used, so that the receive and transmit antennas are physically the same (monostatic radar configuration). The transmit antenna 5 emits an RF signal (almost) continuously HF (t) ab, which is frequency-modulated, for example by a sawtooth-shaped signal. If the radiated signal SHF(t) is backscattered from an object T that may be located in the radar channel within the measurement range of the radar device, the backscattered signal y HF (t) through the receiving antenna 6 received. The object T is usually referred to as the "radar target". In a more general example, there may be more than one target within the field of view of a radar sensor, and it may be able to detect a single target instead of a single one. RX-Antenne An antenna array can be used. Similarly, instead of a single antenna... TX-Antenne An antenna array is used. The use of multiple RX- and TX-Antennen In a multi-channel radar system, measuring the angle of incidence of a radar echo, commonly referred to as the direction of arrival (DoA), is possible. Measuring the direction of arrival is important for many applications, and therefore most radar sensors use antenna arrays. To keep the diagrams simple, only one antenna array is shown in the figures. TX-Antenne and a RX-Antenne shown. It goes without saying that the concepts described herein can be readily transferred to radar sensors with antenna arrays.

[0009] Fig. Figure 2 illustrates the aforementioned conventional frequency modulation of the signal. s HF (t) As shown in the diagram above. Fig. As shown in 2, the signal SHF (t) from a series of "chirps," i.e., sinusoidal waveforms with increasing (upward chirp) or decreasing (downward chirp) frequency. In the present example, the instantaneous frequency increases. f LO (t)a chirp within a defined time period T CHIRP (see diagram below) Fig. 2) from an initial frequency f START to a final frequency f STOP linear. Such a chirp is also called a linear frequency ramp. A linearly frequency-modulated (LFM) signal with three identical linear frequency ramps is in Fig. 2 is shown. However, it should be noted that the parameters f START , f STOP , T CHIRP , as well as the pause between the individual frequency ramps, depending on the actual implementation of the radar system 1 The frequency can vary and can also change during operation of the radar system. In practice, the frequency change can be, for example, linear (linear chirp, linear frequency ramp), exponential (exponential chirp), or hyperbolic (hyperbolic chirp).

[0010] Fig. Figure 3 illustrates a simple example showing how interference can disrupt the operation of a radar sensor. Accordingly, it shows Fig. 3 a road with three lanes and five vehicles A1 , A2 , A3 , A4 and A5 In the present example, the vehicle A1 The vehicle is considered its "own vehicle," and its radar sensor is considered its "own radar sensor." The own radar sensor sends a signal and detects a vehicle moving away from it. A5 , which represents the radar target T to be detected by the own radar sensor, backscattered echo signal E1 However, the radar sensor receives the desired echo signal in addition to the other input. E1 Interfering signals D2 , D3 , D4 , detected by the vehicles' onboard radar sensors A2 , A3 and A4 These jamming signals are transmitted. These jamming signals interfere with the desired radar echo. E1and can detect radar targets from the received radar signal (the echo) E1 as well as the interference signals D2 , D3 and D4 (contains) negatively affect.

[0011] Fig. Figure 4 schematically illustrates an LFM signal with an exemplary FM scheme, as commonly implemented in FMCW radar sensors. In the example shown, a sequence of sixteen upward chirps is sent for data acquisition. It should be noted that in practice, a chirp usually contains many more chirps (e.g., 256 chirps), and the present example has been simplified for illustrative purposes only. A radar sensor transmits an LFM signal, as shown in Figure 4. Fig. Figure 4 shows the system and receives a corresponding radar echo signal. An exemplary signal processing method for evaluating the radar echoes will be described later with reference to... Fig. 12 discussed.

[0012] Depending on the characteristics of the interference signals (see Fig. 3. Signals D2 , D3 and D4 The desired radar echoes can be affected in various ways. Fig. 5 and Fig. Section 6 illustrates, using an example, how a jammer can disrupt the received radar echoes if the jamming signals contain chirps that have different parameters, in particular a different frequency slope, than the radar echoes. Fig. Figure 5 illustrates the frequency of a chirp over time (chirp duration 60 µs), as in the example of Fig. 3 is emitted by its own radar sensor. The initial frequency of the emitted signal SHF (t) is approximately 76250 MHz, and the final frequency is approximately 76600 MHz. An interference signal (e.g., the interference signal) D3 in the example of Fig. 3), generated by another radar sensor, contains an upward chirp that begins at approximately 76100 MHz and ends at 76580 MHz (chirp duration 30 µs), and a subsequent downward chirp that begins at the end frequency of the preceding upward chirp (76580 MHz) and stops at the start frequency of the next upward chirp (76100 MHz), with a chirp duration of 10 µs. The bandwidth B of the baseband signal of the own radar sensor is in Fig. 5 indicated by dashed lines. Fig. Figure 6 illustrates an example curve of the (preprocessed) baseband signal resulting from the received radar signal, which contains a desired radar echo and interference. It can be seen that the signal components are most pronounced in those time intervals in which the frequency of the interference signal falls within the bandwidth B of the radar sensor (see Figure 6). Fig. 5) is, due to the interference, of a significant magnitude. In the present example, the interference occurs three times during the 60 µs chirp duration, namely at approximately 7 µs, 28 µs, and 42 µs. As mentioned, the power of interference signals is usually higher than the power of radar echoes from actual targets. Nevertheless, interference appears as comparatively short bursts, the duration of which depends on how long the bandwidths of the signals overlap. Therefore, not all chirps of a detection sequence are usually present (see Fig. 4) affected by interference. Furthermore, in this example, interference signals and the transmitted signal of a specific radar sensor are uncorrelated, which is why the interference can be considered noise and increases the overall background noise.

[0013] Fig. Figure 7 contains a diagram illustrating a situation in which the interference signals (see, for example, Fig. 3. Signals D2 ,D3 , D4 ) contain chirps that have the same signal parameters, and in particular the same frequency slope and are in the same frequency range as the chirps of the chirp sequences transmitted by the radar's own sensor. As in the example of Fig. Figure 7 shows the frequency differences between the radar signal sent by the radar itself and the corresponding echo. Δf1 If the interference signals D2 , D3 , D4 If they have the same frequency slopes and lie in the same frequency range, the corresponding frequency differences can Δf2 , Δf3 and Δf4 between the transmitted signal and the interference signals D2 , D3 or D4 within an entire acquisition sequence (see Fig. 4) be stable, and therefore the frequency differences can Δf2 , Δf3 and Δf4 When known radar signal processing techniques are used, these signals are misinterpreted as so-called ghost targets. The approaches discussed below aim to solve the ghost target problem by applying additional amplitude modulation to the chirp signals transmitted by a radar sensor. Amplitude modulation is used to transmit information (e.g., a binary code modulated onto the chirps of the transmitted radar signal) along with the transmitted radar signal. This allows the transmitter of the radar signal to be identified, thus distinguishing a radar echo of the radar signal transmitted by the user's own radar sensor from interference signals transmitted by other radar sensors in the received radar signal.

[0014] Before discussing the aforementioned amplitude modulation in more detail, some general aspects of radar sensors will be summarized to provide useful background information.

[0015] Fig. Figure 8 is a block diagram showing an example structure of a radar sensor. 1 illustrated. Accordingly, at least one transmitting antenna is required. 5 (TX antenna(s)) and at least one receiving antenna 6 (RX antenna(s)) with an RF front end 10 , which can be integrated into a semiconductor chip commonly referred to as a monolithic microwave integrated circuit (MMIC). The RF front end 10 It can contain all the circuit components required for RF signal processing. Such circuit components can include, for example, a local oscillator (LO), RF power amplifiers, low-noise amplifiers (LNAs), directional couplers such as rat-race couplers and circulators, as well as mixers for downconverting RF signals (e.g., the signal). y HF (t) , see Fig. 1) contained in the baseband or an IF band. As mentioned, antenna arrays can be used instead of single antennas. The illustrated example shows a bi-static (or pseudo-monostatic) radar system that has separate RX and TX antennas. In the case of a monostatic radar system, a single antenna or antenna array can be used for both receiving and transmitting electromagnetic (radar) signals. In this case, a directional coupler (e.g., a circulator) can be used to separate RF signals to be transmitted to the radar channel from RF signals received by the radar channel.

[0016] In the case of a frequency-modulated continuous wave (FMCW) radar sensor, the signals transmitted by the TX antenna can be 5 The radiated RF signals lie in a range between approximately 20 GHz (e.g., 24 GHz) and 81 GHz (e.g., about 77 GHz in automotive applications). As mentioned, this includes the signal transmitted by the RX antenna. 6The received RF signal represents the radar echoes, i.e., the signals that are scattered back from the radar target(s). The received RF signal y HF (t) is converted down to the baseband and processed in the baseband using analog signal processing (see Fig. 8, baseband signal processing chain 20 ), which essentially involves filtering and amplifying the baseband signal and thus increasing the bandwidth of the received signal (see Fig. 5, bandwidth B) is determined and further processed. The baseband signal is then converted using one or more analog-to-digital converters. 30 digitized and in the digital domain (see Fig. 3. Digital signal processing chain, which is e.g. in the digital signal processor 40 (is implemented) further processed. The overall system is managed by a system controller. 50controlled, which is implemented at least partially using a processor running suitable firmware. The processor can be contained, for example, in a microcontroller, a digital signal processor, or the like. The digital signal processor 40 (DSP) can be part of the system controller 50 or be separate from it. The RF front end 10 and the analog baseband signal processing chain 20 (and optionally the ADC) 30 ) can be integrated into a single MMIC. However, the components can be distributed across two or more integrated circuits.

[0017] Fig. Figure 9 illustrates an exemplary implementation of the RF frontend. 10 , which in which in Fig. The radar sensor shown in section 8 may be included. It should be noted that Fig. Figure 9 shows a simplified circuit diagram illustrating the basic structure of an RF front end. Actual implementations, which can vary significantly depending on the application, may be more complex. In particular, many practical implementations include multiple receive and transmit channels, whereas the example shown depicts only one receive channel and one transmit channel for the sake of simplicity. The RF front end 10 contains a local oscillator (LO) 101 , which emits an RF signal s LO (t) This generates, as above with reference to the Fig. 2 and Fig. 4 explains that it can be frequency modulated. The signal s LO (t) is also referred to as the LO signal. In radar applications, the LO signal is usually in the SHF (super high frequency) or EHF (extremely high frequency) band, e.g., between 76 GHz and 81 GHz in automotive applications.

[0018] The LO signal s LO (t) The signal is processed in both the transmit signal path (transmit channel) and the receive signal path (receive channel). s HF (t) , which is transmitted through the TX antenna 5 The emitted signal is amplified by amplifying the (frequency-modulated) LO signal. s LO (t) , e.g. using an RF power amplifier 102 , generated. The amplifier's output signal 102 is, for example, via strip lines, a coupler, a matching network, etc. (in Fig. (9 not shown) with the TX antenna 5 coupled. The received signal y HF (t) , which is transmitted through the RX antenna 6 is delivered to a mixer 104 supplied. In the present example, the received signal y HF (t) (i.e., the antenna signal) through an RF amplifier 103(e.g., a low-noise amplifier, LNA, with gain g) pre-amplified so that the mixer receives the amplified signal at its RF input. g·y HF (t) receives. The mixer 104 It continues to receive the frequency-modulated LO signal at its reference input. s LO (t) and is designed to amplify the signal g·y HF (t) to convert down to the baseband. The resulting baseband signal at the mixer output is... y BB (t) The baseband signal y BB (t) is processed by the analog baseband signal processing chain 20 (see also Fig. 8), which essentially contains one or more filters (e.g., a bandpass or a lowpass) to remove unwanted side fringing and frame rates, as well as one or more amplifiers, further processes the signal. The analog output signal of the baseband signal processing chain 20 is denoted by y(t) and can be used with an analog-to-digital converter (ADC) 30 (see also Fig. 8) are supplied. This is done by the ADC 30 The output digital signal y[n] is called a digital radar signal, which contains the digital radar data. The digital radar signal can be processed by a processor such as a digital signal processor. 40 to be supplied to a device programmed to further process the digital radar signal, e.g., by applying algorithms grouped under distance / Doppler processing. The implementation of the in Fig. The circuit components shown in 9 are known as such in the context of a radar sensor and will therefore not be discussed in further detail.

[0019] Fig. Figure 9 also illustrates how a desired radar echo and a radar signal sent by another radar sensor interfere. Fig. Figure 9 continues to show the radar front end. 10' of another radar sensor, with only the local oscillator 101' and the transmission channel (with amplifier) 102') and the transmitting antenna 5' The numbers shown are for illustrative purposes only. The additional radar sensor emits a signal. s HF '(t) off. That at the receiving antenna 6 The resulting RF signal arriving from the first radar sensor is called an RF interference signal. y HF,I (t) The receiving antenna is called the receiving antenna. 6 The first radar sensor receives the RF interference signal. y HF,I (t) together with the desired RF echo signal y HF,T (t) , which is located at the radar target T, where the signal emitted by the first radar sensor SHF (t) is scattered back, is caused.

[0020] Both the radar echo y HF,T (t) as well as the interference signal y HF,I (t) are transmitted through the antenna 6 The signals are received and superimposed at the RF input of the mixer. 104 (y HF (t)=y HF,T (t)+y HF,I (t)). Fig. As shown in Figure 9, the interference signal component y HF,I (t) of the received signal y HF (t)in the same way as radar echoes y HF,T (t) , which are contained in the received signal y HF (t) are contained within, and are converted down to the baseband. Accordingly, if the frequency difference between the instantaneous frequency f LO of the transmission signal SHF (t) and the instantaneous frequency of the received interference signal y HF,I (t) within bandwidth B of the baseband signal processing chain 20 The disturbance is also present in the digital signal y[n].

[0021] Two approaches aimed at eliminating interference are time-domain thresholding (TDT) and frequency-domain thresholding (FDT). Both methods adaptively calculate a threshold used to distinguish radar echoes from real targets from interference. However, finding a threshold that reliably differentiates between radar echoes and interference can be challenging in real-world scenarios. Furthermore, as mentioned above, ghost targets can be falsely detected by subsequent digital signal processing if the RF radar echo y HF,T (t) and the interference signal y HF,I (t) Chirps are contained in the same frequency band and with the same or a similar frequency slope.

[0022] As mentioned above, amplitude modulation can be used to encode an additional chirp signal to transmit information that allows a radar echo from a radar signal transmitted by the system's own radar sensor to be distinguished from interference signals transmitted by another radar sensor. The transmitted information can be unique to each radar sensor. Alternatively, the transmitted information can be (pseudo-)randomly selected and periodically changed by a radar sensor. The modulation index of amplitude modulation is low enough (e.g., in the range of 0.05 to 0.5 or 0.1 to 0.2) that amplitude modulation does not significantly impair the detection of radar targets using standard radar signal processing techniques. However, it does allow for the identification and elimination of detected ghost targets.

[0023] Fig. Figure 10 illustrates an example of a linear chirp with a linearly increasing frequency and additional amplitude modulation. The shape of the modulation signal used for the amplitude modulation corresponds to the shape of the envelope of the linear chirp. The modulation signal can, for example, be a binary signal (having only two signal levels, i.e., low and high) representing a bit stream. In the example mentioned above with a modulation index of 0.2, the signal levels low and high correspond to the binary modulation signal. s AM (t)a signal amplitude of 80% or 100% of the amplitude of the frequency-modulated chirp signal. The bit stream is a serial representation of a digital word that can be used as a unique identifier for a radar sensor. Using, for example, a 40-bit word would allow more than a quadrillion radar installations to be distinguished. Some bits of the digital word can be used to implement error correction techniques (e.g., parity bits, cyclic redundancy checks, etc.). Fig. Figure 11 illustrates three different examples of binary modulation signals. s AM (t), which are used to modulate the amplitude of the chirps generated by three different radar sensors. Before the processing of radar signals containing amplitude-modulated chirps is explained in more detail, a standard processing technique commonly referred to as range / Doppler processing is discussed. Range / Doppler processing is generally used in radar sensors to identify radar targets in the range / velocity domain, which is defined by a range / Doppler map (see Fig. 12) is represented, to detect.

[0024] The binary code represented by the aforementioned bit stream / digital word is modulated onto each individual chirp contained in the frequency-modulated RF oscillator signal (LO signal). That is, during each chirp of the RF oscillator signal... s LO (t)The amplitude is modulated according to the digital word representing the radar device's identification code, and this modulation is repeated for each chirp (see below). Fig. 10, which shows an amplitude-modulated chirp). Consequently, each chirp contains the same information represented by the modulated amplitude of the chirp. If the radar system has multiple transmit channels for sending radar signals, the chirps contained in the transmitted radar signals of each channel are amplitude-modulated in the same way, and the same identification code is used in all channels.

[0025] Fig. Figure 12 illustrates the signal processing used in an FMCW radar sensor that emits a frequency-modulated radar signal. Diagram (a) of Fig. Figure 12 illustrates the frequency of an outgoing radar signal over time (solid line, see Figure 12). Fig. 9, Signal s HF (t))and the corresponding incoming radar signal (dashed line, cf. Fig. 9, Signal y HF (t)) Accordingly, the frequency of the outgoing radar signal increases from a starting frequency. f START to a final frequency f STOP linear (Chirp No. 0), then falls on f START It decreases and rises again until the final frequency f STOP is reached (Chirp No. 1), and so on. As already mentioned with reference to Fig. As mentioned in section 4, the outgoing radar signal is composed of a sequence of "frequency ramps," also known as "chirp signals" or "chirps." Depending on the application, a modulation pause can be inserted between two adjacent chirps, during which the radar signal may remain at the end frequency or the start frequency (or any frequency between the start and end frequencies). The duration T CHIRP The duration of a chirp can range from a few microseconds to a few milliseconds, e.g., 20 µs to 2000 µs. However, the actual values ​​can be higher or lower depending on the application.

[0026] The (through a RX The radar signal received by the antenna differs from the outgoing radar signal (radiated by the antenna) due to the travel time. TX -Antenna to the radar target (from which the radar signal is backscattered) and back to the RX The antenna is delayed by a time delay Δt. The time delay Δt is often referred to as the round-trip delay (RTD). The distance d T of the radar target from the radar sensor is d T = c·Δt / 2, i.e., the speed of light c times half the time delay Δt. As from Fig. As can be seen in diagram (a) 12, the time delay Δt leads to a frequency shift Δf, which can be reduced by downmixing the incoming signal (see Fig. 4, Mixer 104 , diagram (b) of Fig. 12) by digitizing the baseband signal and performing a subsequent digital spectral analysis; the frequency shift appears in the baseband signal as a so-called “beat frequency”. If a linear chirp (i.e., a sawtooth modulation signal) is used, the time delay Δt can be calculated according to Δt = Δf / k, where the factor k represents the slope (steepness) of the frequency ramp, which is calculated according to k = (f STOP -f START ) / T CHIRP can be calculated.

[0027] Although the basic operating principle of an FMCW radar sensor has already been explained, it should be noted that more sophisticated signal processing can be applied in practice. In particular, an additional frequency shift. f D The Doppler effect can cause an error in distance measurement due to the incoming signal, as the Doppler shift f D The Doppler shift is added to the frequency Δf, which, as explained above, is caused by the travel time Δt (rounding time delay RTD) of the radar signal. Depending on the application, the Doppler shift can be estimated from the outgoing and incoming radar signals, while in some rangefinding applications, the Doppler shift may be negligible. This can be particularly true when the chirp duration is T CHIRP is short, so that the frequency shift Δf is in comparison to the Doppler shift f D for any distance within the radar sensor's measuring range, the frequency of the radar signal increases from... f START on F STOP This results in a so-called "upward chirp". However, the same measurement methods can also be applied to "downward chirps", i.e., when the final frequency is lower. f STOP smaller than the starting frequency f START is and the frequency during a chirp changes from f START to f STOP reduced. In some radar systems, the Doppler shift can be eliminated if the range is calculated based on an "upward chirp" and a "downward chirp". Theoretically, the actually measured range can be d T The distance of a radar target is calculated as the average of a distance value obtained from the upward chirp echo and a distance value obtained from the downward chirp echo; averaging cancels out the Doppler shift.

[0028] As stated above, the distance d T of the radar target are calculated by the radar sensor according to d T = c ⋅ Δ f ⋅ T CHIRP / ( 2 ⋅ B ) , where Δf denotes the beat frequency and B the bandwidth of the chirp (B = |f STOP - f START |). Accordingly, the basic signal processing of the linear FMCW radar involves determining the beat frequency Δf by spectral analysis. As mentioned, the Doppler effect must be taken into account to determine the velocity of the radar target (relative to the radar sensor). This can be done based on the aforementioned range Doppler maps, which can be calculated using range Doppler processing, an example of a standard digital signal processing technique for processing the digital FMCW radar signals (see Fig. 9, DSP 40 ) to process, is.

[0029] Distance Doppler processing involves the calculation of range Doppler maps (also called range Doppler images). In general, linear FMCW radars obtain target information (i.e., range, angle, and velocity of a radar target) by transmitting a sequence of linear chirps and processing the delayed chirp echoes (see Fig. 9, Signal y HF (t)) mix (downgrade) the signals from the targets with a copy of the sent signal (see Fig. 9, Mixer 104 , the signals s LO (t) receives). The downconverted chirp echoes are shown in diagram (b) of Fig. 12 shown (analog baseband signal y(t), see Fig. 9) The target range information (i.e., the distance between the sensor and a radar target) can be extracted from the spectrum of this downconverted signal. Therefore, the downconverted chirp echoes are digitized (see Fig. 9, ADC 30) to obtain the digital radar signal y[n]. A range Doppler map can be obtained, as described in more detail below, e.g., by a two-stage Fourier transform. Range Doppler maps can be used as the basis for various target detection, identification, and classification algorithms.

[0030] In the examples shown herein, a digital signal processor (DSP) is used as the computing unit to perform the calculations required to obtain the range map. However, it should be noted that the necessary calculations can be performed by various hardware and software units and combinations thereof, and that the terms computing unit and processor generally encompass any hardware or software unit or combination thereof capable and configured to perform the calculations described in connection with the embodiments described herein.

[0031] The common procedure for calculating the range-Doppler map involves two steps, each step requiring the calculation of several Fourier transforms, typically implemented using a fast Fourier transform (FFT) algorithm. In this discussion, the term "chirp echo" is used to denote the digitized baseband signal corresponding to an RF chirp echo received from the antenna. Furthermore, this example assumes that the signal from the ADC 30 (see Fig. 9) provided digital radar signal y[n] contains N × M samples representing M chirp echoes, where each chirp echo is composed of N samples (sampling time interval) T SAMPLE These N × M samples can be stored in a two-dimensional array Y[n, m] (see diagram (c) of Fig. 12) arranged with N rows and M columns. Each column of the array Y[n, m] represents a chirp. The nth row of the array Y[n, m] contains the nth sample of each chirp. The row index n can also be expressed as a discrete time value n·T. SAMPLE on a "fast" time axis. Similarly, the column index m (chirp number) can be viewed as a discrete time value m·T. CHIRP to be viewed on a "slow" timeline.

[0032] In a first step, a first FFT (usually called a range FFT) is applied to each chirp echo, i.e., to each column of the array Y[n, m]. That is, the FFT is computed for each of the M columns of the array Y[n, m]. In other words, the FFT is applied to the array Y[n, m] along the "fast" time axis. The resulting Fourier transforms can also be arranged in a two-dimensional array called the range map R[n, m], where the M columns contain the Fourier transforms of the M chirps. Each of the N rows contains the (complex-valued) spectral values ​​for a particular discrete frequency value. Accordingly, the index n, running from zero to N-1, represents a discrete frequency value, often called a frequency bin. The range map R[n, m] is shown in diagram (c) of Fig. Figure 12 illustrates this. A radar echo from a target results in a peak that occurs at a specific frequency bin. Typically, the peak appears in all columns, i.e., in all (Fourier-transformed) chirp echoes. The frequency value of the frequency bin can be converted into range information, e.g., according to Eq. (1). In other words, the index n in the range map R[n, m] can be assigned to a range value.

[0033] In a second stage, a second FFT (usually called a Doppler FFT) is applied to each N row of the range map R[n, m]. Each row of the range map R[n, m] contains N spectral values ​​of the M chirps for a specific frequency bin, where each frequency bin corresponds to a specific distance of a radar target. In other words, the FFT is applied to the range map R[n, m] along the "slow" time axis. The resulting Fourier transforms can also be arranged in a two-dimensional array called the range / Doppler map X[n, m]. A radar echo from a target produces a peak that appears at a specific location on the range / Doppler map X[n, m]. As mentioned, the number of rows n ∈ [0, ..., N-1] where the peak occurs represents the frequency bin, and the corresponding frequency value can be determined, for example, according to Eq. (1) can be converted into distance information. The column number m ∈ [0, ...., M-1], where the peak occurs, represents the Doppler frequency (frequency shift due to the Doppler effect), which can be converted into velocity information. In the case of more than one RX antenna, a range / Doppler map X can be created for each antenna. a [n, m] are calculated, where a is the index of the relevant RX-Antenne denoted (a = 0, 1, ... A-1, where A is the number of RX-Antennen (designated). The A Range / Doppler cards X a [n, m] can be stacked to form a three-dimensional array. The corresponding arrays Ya[n, m], which contain the digital radar signals for all antennas, are sometimes referred to as "radar data cubes". It is understood that the parameters N and M can be the same, but generally differ. For example, a detection sequence (cf. Fig. 4) M = 256 chirps are contained, where each chirp is represented by N = 512 samples.

[0034] As mentioned, radar data cubes, or the resulting range maps R[n, m] or range-Doppler maps X[n, m], can be used as input data for various signal processing techniques to detect radar targets in the vicinity (within the line of sight) of the radar sensor. For example, various peak detection algorithms are known to detect peaks (i.e., local maxima, FFT peaks) in the range map or range / Doppler map caused by objects (radar targets) in the radar channel. That is, a target can be detected if a value in the range map or range-Doppler map exceeds a certain threshold. However, more complex detection algorithms can also be used. Additional signal processing steps are performed to obtain a list of radar targets and corresponding range and velocity information from the detected FFT peaks.

[0035] As mentioned above, in practical applications such as automotive radar systems, situations can arise in which so-called ghost targets are detected. Such ghost targets can be caused by radar signals generated by other radar sensors if the chirp sequences of the radar sensors are in the same frequency range and the slope of the chirps is the same or similar. To enable a radar sensor to distinguish true echoes of its own transmitted radar signals from "foreign" radar signals, additional amplitude modulation can be applied to the (frequency-modulated) chirps. The signal used for amplitude modulation carries information that allows the radar sensor to identify its "own" chirp echoes. An example of an amplitude-modulated chirp was described in Fig. 10 were shown, and examples of suitable modulation signals were presented in Fig. 11 shown. Fig. Figure 13 illustrates an example of a radar transceiver that includes an RF front end 10 , baseband signal processing 20 , the analog-to-digital conversion 30 and the computing unit 40 , which is used for the digital signal processing of the digital radar signal y[n]. The basic structure of the in Fig. The analog components shown in the 13 examples are similar to the example of Fig. 9, and reference is made to the relevant explanations above; therefore, the following discussion focuses on the additional components used for amplitude modulation (AM) and the corresponding digital signal processing.

[0036] Compared to the previous example of Fig. 9 contains the present example of Fig. 13 an additional modulator 151 , the one with the amplifier 102 , which is connected upstream of this. That is to say, the modulator 151receives the frequency-modulated LO signal s LO (t) and modulates the amplitude of the LO signal s LO (t) corresponding to a modulation signal s AM (t) (cf.) Fig. 11), which is processed by an AM encoder 150 is provided. In other configurations, the modulator can 151 with the amplifier 102 , downstream of this, are coupled. The sequence of amplitude-modulated chirps is used as a signal. s LO,AM (t) designated as the effect of the amplifier 102 amplified and through the transmitting antenna 5 - as an RF radar signal SHF (t) - is emitted. The AM encoder 150 will be used with the LO 101 synchronized, so that the modulation signal s AM (t) can be generated synchronously with the individual chirps. Thus, each chirp can be amplitude-modulated in the same way. As in conjunction with Fig. As mentioned in point 11, the modulation signal can s AM (t)represent a binary sequence (i.e., a bitstream) generated according to a digital word ID. In this example, the digital word is a unique number used as an identifier and stored in a register. 410 , which is in the computing unit 40 It may contain information that is stored.

[0037] The received radar signal y HF (t) , which may contain RF chirp echoes and ghost echoes, is processed by the mixer. 104 using the LO signal s LO (t) downconverted, the downconverted signal y(t) (baseband signal) is digitized, and the resulting digital radar signal y[n] is sent to the processing unit 40 (e.g., a signal processor). As above with reference to Fig. As explained in section 12, the samples contained in the digital radar signal y[n] can be used for data acquisition (distance measurement, see Fig. 4) are arranged in an array Y[n, m], where each of the m columns of Y[n, m] contains n samples representing a chirp echo (in the baseband). The column-wise Fourier transform of the array Y[n, m] yields the range map R[n, m]. The in Fig. 13 FFT units shown 401 is designed to calculate the range map R[n, m] from the digital radar signal y[n]. The range map R[n, m] is then sent to the target detection unit. 406 supplied, which is trained to select radar targets T from the data contained in the range map R[n, m]. i to detect. The target detection unit 406 can furthermore be trained to compute a range / Doppler map X[n, m] during this detection process. The detected targets T i are represented by corresponding distance and speed information.

[0038] The target detection unit 406It receives information about which of the frequency bins of the range map R[n, m] contains data in which the identifier ID of the radar sensor, which was also used for amplitude modulation of the transmitted radar signal, was detected. This enables the target detection unit 406 , to distinguish "own" radar echoes from ghost echoes. The following explanations refer to the detection of the identifier ID (which was used for AM in the transmit path) in the received radar data. This detection process involves—for one or more chirp echo signals (columns) contained in the matrix Y[n, m]—separating potential radar echoes (which indicate real targets and ghost targets) in the frequency domain, which is essentially achieved by bandpass filtering in the frequency domain. In the present example, this separation of potential radar echoes is performed by the FFT separation unit. 402performed, and the spectra of potential radar echoes are with Y i [n] denotes (the index i denotes a specific radar echo from a specific target T) i In this context, the term "chirp-echo signals" refers to the baseband signals obtained by downconverting the RF chirp-echo signals. The operation of the FFT separation unit 402 will be discussed later with reference to Fig. 14 discussed in more detail. The spectra Y i [n] will be, e.g. using a unit defined by the IFFT unit 403 implemented, inverse FFT algorithm', transformed back into the time domain, where the spectra Y i [n], depending on the actual implementation, can be transformed sequentially or in parallel.

[0039] The resulting signals y i[n] of the time domain show amplitude modulation if they were caused by a radar signal containing amplitude-modulated chirps with the correct identifier ID. Accordingly, the envelope of the signals y corresponds to i [n] the modulation signal s AM [t], if the modulated chirps were transmitted by the same radar sensor. Determining the envelope is essentially a demodulation of the amplitude-modulated signal y. i [n], which in the example of Fig. 13 by the demodulator designated “AM Demod.” 404 is implemented. For each potential target T i The resulting envelope will be e i [n] of the AM code comparator unit 405 supplied, which is trained to envelop the i [n] to compare with the identifier ID of the radar sensor and to decide whether a particular envelope e i[n] matches the identifier ID. In one embodiment, the AM code detector can 405 be trained to envelop the i [n] and the identifier ID are correlated, and a threshold is used to detect a match. However, other approaches such as Wiener filtering or the calculation of a cross-correlation or correlation coefficient can be used. As mentioned, the target detection unit is 406 informs which of the potential chirp echoes matches the AM code comparator unit. 406 have caused. The frequency bins associated with a potential chirp echo / radar target for which the AM code could not be detected can be discarded (e.g., filled with zeros in the range map R[n, m]) before the range Doppler map is calculated.

[0040] Fig. Figure 14 schematically illustrates a column of an exemplary range map R[n, m], which shows three peaks at frequencies f1 , f2 and f3 (the frequency bins n1 , n2 , n3 corresponding) contains the presence of three potential radar targets T1 , T2 , T 3 The peaks are somewhat broadened due to the amplitude modulation; those of the modulation signal s AM (t) The information carried is located in the frequency bins adjacent to the frequency bins n1 , n2 and n3 , which are commonly referred to as sidebands. In other words, amplitude modulation spreads the spectrum "occupied" by each radar target, thus reducing the resolution of the frequency measurement (see also Fig. 17).

[0041] Fig. Figure 14 further illustrates how the separation of potential chirp echoes by the FFT separation unit402 can be implemented. As explained above, the FFT separation unit performs 402 Essentially, bandpass filtering is performed in the frequency domain. Accordingly, the spectral values ​​within the passbands are... B1 , B2 and B3 , which show the peaks at the frequencies f1 , f2 and f3 enclose, separated into different spectra Y1[n], Y2[n] and Y3[n], each of which contains only one of the passbands B1, B2 and B3, and then transformed back into the time domain (see Fig. 13, IFFT unit 403 ).

[0042] The range of in Fig. 14 passage bands shown B1 , B2 and B3 It depends on the code length of the identifier ID and thus on the number of bits or symbols to be transmitted in a chirp. Since the length T CHIRP Since the length of a chirp is fixed, the required bit rate or baud rate increases with the length of the identifier. To reduce the number of symbols to be transmitted with a chirp, a multi-level modulation signal can be used instead of a binary signal. S AM (t) can be used for amplitude modulation. Fig. Figure 15 illustrates an example of a quaternary (4-stage) modulation signal. s AM (t) (i.e., the signal can assume four different levels), so that each symbol represents two bits. As can be seen for a given code length (e.g., 32 bits), using a multi-level modulation signal reduces s AM (t) the number of symbols to be transmitted. For example, using a quaternary modulation signal halves the number of symbols. s AM (t) , as it is in Fig. Figure 15 shows a binary modulation signal instead of the one shown in Figure 15. Fig. Figure 11 shows the number of symbols that can be transmitted with a chirp for a given code length. A smaller number of symbols results in a smaller bandwidth for the passbands. B1 , B2 and B3 (cf.) Fig. 14) and thus to a higher resolution of distance measurement. Multi-level signals can also be referred to as L-level signals, where L is an integer indicating the number of levels.

[0043] Another option to further reduce the required bandwidth (and thus increase the achievable resolution) is to use single-sideband (SSB) modulation instead of conventional amplitude modulation. The effect of using SSB modulation instead of AM modulation is in Fig. 16 depicted a similar situation to Fig. Figure 14 illustrates this; however, since SSB modulation is used instead of AM, only one sideband (the lower or the upper sideband) is added to the peaks caused by the radar targets. The bandwidth of the passbands B1, B2, and B3 can therefore be chosen to be, for example, twice as small as in the situation described above. Fig. 14. It should be noted that SSB modulation can be performed with binary modulation signals as well as with multi-level modulation signals. It is understood that SSB modulation is a variant of amplitude modulation. SSB modulation can be divided into SSB modulation with upper sideband (USB) or lower sideband (LSB) transmission. In communication systems, SSB modulation is usually performed with a suppressed carrier, which is undesirable in radar applications because the carrier in the receive path carries the most important information, namely the distance information to radar targets.

[0044] The diagram of Fig. Figure 17 illustrates how the code length of the identifier ID affects the required bandwidth of the FFT separation unit. 402 (see Fig. 13) the bandpass filter used and thus the achievable resolution, for various modulation techniques. As from Fig. As can be seen in section 17, the achievable resolution decreases with increasing code length (and thus increasing bit / baud rate). Furthermore, the use of quaternary modulation signals results in a higher resolution than binary modulation signals, and SSB modulation improves the resolution by a factor of two.

[0045] Fig. 18 is a flowchart that shows an exemplary implementation of a procedure that is described in the Fig. The process, which can be implemented as shown in Figure 13, is summarized below. According to the illustrated example, the method involves generating an RF oscillator signal (see Figure 13). Fig. 13, LO signal s LO (t)) , the frequency-modulated chirps (see Fig. Step 18 S1 ) contains, and the amplitude modulation of the RF oscillator signal by a modulation signal (see Fig. Step 18 S2 ). The modulation signal can be used in this process (see below). Fig. 13, Signal s AM (t)) represent a unique identifier (ID) of the radar system. The amplitude-modulated RF signal (see Fig. 13, Signal s LO,AM (t)) is then transmitted via an antenna (see below). Fig. 13, TX antenna 6 ) sent.

[0046] In one implementation, amplitude modulation is implemented such that the amplitude of each frequency-modulated chirp is modulated by the modulation signal representing an identifier ID, as mentioned above. Accordingly, the information represented by the identifier ID is contained within each individual chirp. The modulation index of the amplitude modulation can range from 0.05 to 0.5, and more specifically from 0.1 to 0.2. There is a trade-off between the modulation index and the signal-to-noise ratio of the received radar echo signals, as a high modulation index reduces the transmitted signal power. In practice, the modulation signal representing the identifier ID is either a two-level signal or a multi-level signal that allows for more than two discrete signal levels.

[0047] Fig. Figure 19 is a flowchart illustrating an example of how the identifier modulated onto the transmitted chirps can be detected in the corresponding chirp echo signals contained in the received radar signal. According to the example shown, the procedure involves receiving an RF signal (see Figure 19). Fig. 13, Signal y HF (t)), which consists of frequency-modulated chirp-echo signals from one or more target objects T i is composed (see Fig. Step 19 S4 The received RF signal is downconverted to the baseband using the RF oscillator signal to provide a corresponding baseband signal (see Fig. Step 19 S5 Furthermore, the process includes processing the baseband signal (see...). Fig. 13, signal y(t)), to detect information that is also contained in the modulation signal used for amplitude modulation of the transmitted chirps (see Fig. Step 19 S6 ).

[0048] In one implementation, processing the baseband signal involves correlating a signal based on the baseband signal with a signal representing the modulation signal (and thus the identifier). In the example of Fig. 13 This correlation is determined by the AM code comparator 405 carried out. In a more specific implementation, processing the baseband signal involves digitizing the baseband signal to create a digital signal (see...). Fig. 13, Signal y[n]) to obtain, the calculation of a range map (see Fig. 12, Range map R[n, m]) based on the digital signal, wherein the range map contains a plurality of spectra corresponding to a plurality of chirp-echo signals (i.e., the columns of the reference to Fig. 11. The matrix X[n, m]) is explained, and the detection of one or more peaks in the spectra. The detected peaks allow for the identification of potential target objects T. i close. A time-domain signal is generated for each peak (see below). Fig. 13, y i [n]) calculated from the range map. The time domain signals can be used to check whether information (i.e., the identifier ID) contained in the modulation signal is also contained in the time domain signals. A potential target object T i can be discarded if the information contained in the modulation signal is not contained in the relevant time domain signal.

Claims

[1] Method which features: Generating an RF oscillator signal (s LO (t)), which contains frequency-modulated chirps; Amplitude modulation of the RF oscillator signal (s LO (t)) by a modulation signal (s AM (t)); Sending the amplitude-modulated RF oscillator signal (s LO,AM (t)) via at least one antenna; Receiving an RF signal (y HF (t)), which contains frequency-modulated chirp-echo signals from a target object (T); Downconverting the received RF signal (y HF (t)) into a baseband using the RF oscillator signal (s LO (t)) and thus providing a baseband signal (y(t)); and Processing the baseband signal (y(t)) to extract information contained in the modulation signal (s) AM (t)) are contained, to detect. [2] Method according to claim 1, wherein the amplitude modulation of the RF oscillator signal (s LO(t)) exhibits: Modulating the amplitude of each frequency-modulated chirp with the modulation signal (s LO (t)), which represents an identification code (ID). [3] Method according to claim 2, wherein the modulation index is not more than 0.5 or not more than 0.

2. [4] Method according to claim 2 or 3, wherein the identifier is a digital word. [5] Method according to any one of claims 2 to 4, wherein the modulation signal is a two-level signal or a multi-level signal that allows more than two discrete signal levels. [6] Method according to any one of claims 1 to 5, wherein the amplitude modulation of the RF oscillator signal (s LO (t)) exhibits: Applying single-sideband modulation to the RF oscillator signal (SLO(t)). [7] Method according to any one of claims 1 to 6, wherein the processing of the baseband signal (y(t)) comprises: Digitizing the baseband signal (y(t)) to obtain a digital signal (y[n]), Calculating a range map (R[n, m]) based on the digital signal (y[n]) with a multitude of spectra corresponding to a multitude of chirp echo signals; the detection of one or more peaks in the spectra that point to a potential target object (T i ) close; Calculating a time-domain signal (y) i [n]) from a range map (R[n, m]) for each detected peak; and Check if information contained in the modulation signal (s AM (t)) are also contained in the time domain signal (y) i [n]) are included. [8] Method according to any one of claims 1 to 7, further comprising: Rejection of a potential target (T) i ), if the in the modulation signal (s AM (t)) information not contained in the corresponding time domain signal (yi [n]) are included. [9] Method according to any one of claims 1 to 8, wherein the processing of the baseband signal (y(t)) comprises: Correlate a signal based on the baseband signal (y(t)) with a signal that is the modulation signal (s AM (t)) represents. [10] Radar device which includes: an RF oscillator (101) designed to generate an RF oscillator signal (s LO (t)), which contains frequency-modulated chirps; a modulator (151) that modulates the RF oscillator signal (s LO (t)) and a modulation signal (s AM (t)) receives and is designed to transmit the RF oscillator signal (s LO (t)) by the modulation signal (s AM (t)) to modulate amplitude; one or more antennas (5, 6) designed to receive the amplitude-modulated RF oscillator signal (s LO,AM (t)) to send and an RF signal (y HF(t)), which contains frequency-modulated chirp echo signals from a target object (T); a mixer (104) that converts the RF oscillator signal (s LO (t)) and the received RF signal (y HF (t)) receives and is designed to transmit the RF signal (y HF (t)) to downconvert to the baseband and provide a corresponding baseband signal (y(t)); an analog-to-digital converter (30) configured to digitize the baseband signal (y(t)); and a computing unit (40) designed to process the baseband signal (y(t)) in order to extract information contained in the modulation signal (s AM (t)) are contained, to detect. [11] Radar device according to claim 10, further comprising: an encoder unit (150) designed to convert the modulation signal (s AM (t)) to generate depending on a digital code, wherein the modulator (151) is configured to combine each frequency-modulated chirp with the modulation signal (s LO (t)) to modulate. [12] Radar device according to claim 10 or 11, wherein the modulator (151) is a single-sideband modulator. [13] Radar device according to one of claims 10 to 12, wherein the computing unit is configured to: to compute a range map (R[n, m]) based on the digital signal (y[n]), wherein the range map (R[n, m]) contains a plurality of spectra corresponding to a plurality of chirp echo signals; to detect one or more peaks in the spectra that suggest potential target objects (T); for each detected peak from the range map (R[n, m]) a time domain signal (y i [n]) to calculate; to check whether information contained in the modulation signal (s AM (t)) is also contained in the time domain signal (y) i[n]) is contained. [14] Radar device according to claim 13, wherein the computing unit is further configured to: a potential target object (T i ) to discard if the modulation signal (s AM (t)) information not contained in the corresponding time domain signal (y) i [n]) is contained. [15] Radar device according to one of claims 10 to 14, wherein the computing unit is further configured to: a signal based on the baseband signal (y(t)) with a signal that is the modulation signal (s AM (t)) represents, to correlate.

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