PROCESSING RADAR SIGNALS

It is suggested to process radar signals at a first radar unit as follows: (i) receiving the radar signals via at least one receiving antenna; (ii) selecting a portion of the radar signals or of data that is based on the radar signals for further processing; and (iii) conveying a reduced amount of data to a second radar unit, wherein the reduced amount of data is based on the portion of the radar signals or of data that is based on the radar signals.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application 10 2022 128 752.1, filed on Oct. 28, 2022. The contents of the above-referenced Patent Application is hereby incorporated by reference in its entirety.

BACKGROUND

Embodiments of the present invention relate to processing radar signals, in particular to units that enable or utilize such signal processing.

Processing radar signals in this regard in particular refers to radar signals received by a sensor or an antenna. Each sensor may have more than one antenna.

Several radar variants are used in cars for various applications. For example, radar can be used for blind spot detection (parking assistant, pedestrian protection, cross traffic), collision mitigation, lane change assist and adaptive cruise control. Numerous use case scenarios for radar appliances may be directed to different directions (e.g., back, side, front), varying angles (e.g., azimuth direction angle) and/or different distances (short, medium or long range). For example, an adaptive cruise control may utilize an azimuth direction angle amounting to ±18 degrees, the radar signal is emitted from the front of the car, which allows a detection range up to several hundred meters.

An objective is to improve existing solutions, in particular increase the efficiency of a radar system with distributed components.

This problem may be solved according to the features of the independent claims. Further embodiments result from the dependent claims.

SUMMARY

The examples suggested herein may in particular be based on at least one of the following solutions. In particular combinations of the following features could be utilized in order to reach a desired result. The features of the method could be combined with any feature(s) of the device, apparatus, system or computer product or vice versa.

A method is suggested for processing radar signals at a first radar unit comprising: receiving the radar signals via at least one receiving antenna, selecting a portion of the radar signals or of data that is based on the radar signals for further processing, conveying a reduced amount of data to a second radar unit, wherein the reduced amount of data is based on the portion of the radar signals or of data that is based on the radar signals.

Hence, this approach allows to efficiently cope with a limited bandwidth connection between the first and second radar unit.

According to an embodiment, the first radar unit is a radar sensor electronic control unit.

According to an embodiment, the second radar unit is a central electronic control unit.

According to an embodiment, the portion of the radar signals or of data that is based on the radar signals is selected on at least one of the following: a random basis, a pseudo-random basis, a deterministic selection scheme.

According to an embodiment, an information regarding the portion of the radar signals or of data that is based on the radar signals is conveyed to the second radar unit.

This information may be an information regarding the reduction scheme or the selection code. It allows the second radar unit to become aware of the reduction and/or the systematic of the reduction.

According to an embodiment, the selection of the portion of the radar signals or of data that is based on the radar signals comprises at least one of the following: a selection of chirps; a selection of FFT results, in particular of first stage FFT results; a selection of at least one receiving channel; a selection of analog signals; a selection of digital signals.

According to an embodiment, the portion of the radar signals or of data that is based on the radar signals comprises output data of an interference detection.

It is an option that the selection or an additional selection utilizes an output of an interference detection (which may be obtained by an interference detection unit) to get rid of (at least a portion of) signals that are subject to interference. Such interfered signals can be omitted thereby reducing the overall communication load between the first and second radar unit.

Also, a device for processing radar signals is suggested, wherein the device comprises a processing unit that is arranged for receiving the radar signals via at least one receiving antenna, selecting a portion of the radar signals or of data that is based on the radar signals for further processing, conveying a reduced amount of data to a second radar unit, wherein the reduced amount of data is based on the portion of the radar signals or of data that is based on the radar signals.

It is noted that the steps of the method stated herein may be executable on this processing unit. It is further noted that said processing unit can comprise at least one, in particular several means that are arranged to execute the steps of the method described herein. The means may be logically or physically separated; in particular several logically separate means could be combined in at least one physical unit. The processing unit may comprise at least one of the following: a processor, a microcontroller, a hard-wired circuit, an ASIC, an FPGA, a logic device.

According to an embodiment, said device is a first radar unit.

Further, a computer program product is provided, which is directly loadable into a memory of a digital processing device, comprising software code portions for performing the steps of the method as described herein.

Embodiments are shown and illustrated with reference to the drawings. The drawings serve to illustrate the basic principle, so that only aspects necessary for understanding the basic principle are illustrated. The drawings are not to scale. In the drawings the same reference characters denote like features.

DETAILED DESCRIPTION

In a radar processing environment, a radar source emits a signal and a sensor detects a returned signal. The returned signal may be acquired in a time domain by at least one antenna, in particular by several antennas. The returned signal may then be converted into the frequency domain by conducting a Fast Fourier Transform (FFT), which may result in a signal spectrum, e.g., a signal distributed across the frequency. Frequency peaks may be used to determine potential targets, e.g., along a moving direction of a vehicle.

A Discrete Fourier Transform (DFT) may be implemented in computers by numerical algorithms or dedicated hardware. Such implementation may employ FFT algorithms. Hence, the terms “FFT” and “DFT” may be used interchangeably.

The signal emitted by each of the antennas has a ramp-shape, wherein each ramp may have a linear rising slope of frequency over time. The reflected ramps are received and further processed by the radar system. An acquisition period may comprise several ramps. Each of the ramps is also referred to as chirp. Hence, the chirp has a certain bandwidth and duration. The slope of frequency may be linear, but it may also be of different shape.

In vehicles, in particular cars, electronic architectures are more often equipped with at least one high performance electronic control unit (ECU) acting as a central ECU. With decreasing costs of computing resources, e.g., processing power and/or memory, overall costs may be optimized by shifting the processing from the distributed components, e.g., sensors, towards the increasingly powerful central ECU. This also allows using more complex approaches, e.g., algorithms processing higher resolution or improved interference mitigation to achieve the goal of a better overall performance of the radar application.

A problem of this approach lies within the amount of data to be transmitted towards the central ECU.

An exemplary solution described herein is directed to a reduction of the overall data (also referred to as “compression of data”) which efficiently copes with the bottleneck of the connection between decentralized ECUs and the central ECU.

For example, the transmission (data rate) may be adjusted to achieve a suitable compression that allows for a compromise between the following conflicting goals: the processing power (and the memory) of the de-centralized component, e.g., radar sensor, to provide radar data; and a benefit provided by the output of the central ECU based on the data obtained for the de-centralized component(s).

FIG.1shows an exemplary radar component101, which may be a radar (sensor) ECU, comprising a radiofrequency (RF) processing102, a signal processing103and a signal compression and transmission104.

The output of the radar component101is connected to a central ECU110, which comprises a signal decompression unit111and a signal processing unit112.

In an exemplary scenario, several radar components101covey data to at least one central ECU110. The processing power of the central ECU110may in particular be significantly higher than the processing power (and memory) available at each of the decentralized radar components101. Hence, applications running at the central ECU110can utilize the higher computing performance to produce improved results (e.g., higher resolution, faster recognition of objects, etc.).

FIG.2shows an exemplary radar processing flow. A Monolithic Microwave Integrated Circuit (MMIC)201receives radar data, e.g., via several antennas. The MMIC201outputs analog-digital-converted (ADC) data towards a sensor preprocessing unit (SPU)202.

The SPU202provides a sensor pre-processing stage and it may in particular process the received ADC data as follows: interference may be mitigated in a unit203; a direct current (DC) offset is compensated in a DC-offset compensation unit204; a first stage FFT is conducted in a unit205and the results are stored in a radar memory206; a second stage FFT is conducted in a unit207; the results a stored in a range/Doppler (R/D) map208; threshold detection is conducted based on the R/D map208and the output of the unit207by a unit209; the output of the unit209is multiplied with the output from the second stage FFT unit207and the result of this multiplication is fed to a digital signal processor (DSP)210.

The DSP210may determine, e.g., a direction of arrival (based on e.g., a parabolic interpolation), and supplies its outputs towards another DSP211.

The DSP211may be or comprise (at least one) microcontroller unit (MCU) and it may conduct a classification212, a tracking213, a decision making214, and supply data to a vehicle interface215.

The DSP210and the DSP211may be arranged as a single device or as multiple devices.

InFIG.2, the output of the MMIC201is 100% (without compression), the output of the first stage FFT unit205is 100% (without compression), whereas the output of the DSP210may only be 2% to 5% due to the processing provided by the DSP210.

FIG.3shows an exemplary division of the radar processing flow between a (decentralized) radar sensor ECU301and a central ECU302, which are connected, e.g., via a line303(which may be implemented as parallel or serial bus). In a vehicle, several radar sensor ECUs301may be connected to one central ECU302.

The radar sensor ECU301comprises the components MMIC201, interference unit203, DC-offset compensation unit204, first stage FFT unit205and radar memory206as described with regard toFIG.2above.

In addition, the radar sensor ECU301comprises an interface311that is connected to the line303.

The central ECU302also comprises an interface312that is connected to the line303. As an option, the interface312may be connected to several lines from other ECUs (not shown inFIG.3).

The interface312feeds data to the second stage FFT unit207. The further processing within the central ECU302comprising the R/D map208, the unit209, the DSP210and the DSP/MCU211corresponding to the components shown in and described with regard toFIG.2.

Hence, in contrast to the radar processing flow ofFIG.2,FIG.3divides the processing into a portion conducted by the radar sensor ECU301and another portion conducted by the central ECU302, which are both connected via interfaces311,312by said line303.

A bottleneck might be the data amounts processed by the ECU301to be conveyed to the central ECU302.

An exemplary solution to overcome this obstacle suggests reducing the amount of data that has to be conveyed from the decentralized ECU301to the central ECU302across the line303.

Such reduction (or compression) may in particular comprise at least one of the following: a selective omission of at least one signal or at least a portion of such signal; a reduction of the memory allocated by at least one signal.

The selective omission of at least one signal is also referred to as a selection of signal. Such omission may follow a random, pseudo-random or deterministic approach. It is noted that random selection may refer to a true random selection or to any selection that may have at least some degree of randomness, e.g., generated by a random generator of a deterministic machine like a microcontroller or processor.

For example, 7 out of 12 signals may be selected for further processing purposes. In other words, 5 signals are to be omitted. This selection can be made randomly, pseudo-randomly or due to a deterministic rule (e.g., following a predefined pattern stored, e.g., in a table). As a result, only 7 signals (instead of 12 signals) are conveyed towards the central ECU302resulting in a reduction of data to be conveyed across the line303. This reduction of data may also be referred to as compression.

The reduction of data can be achieved at various stages within the radar sensor ECU301. For example, the reduction may be conducted in the MMIC201and/or the first stage FFT unit205.

As an option, the reduction may use a reduction scheme that is known to the central ECU302in order for the ECU302to be aware which data arrives and which data has been omitted. The reduction scheme may be known to the ECUs in advance or (at least in part) a posteriori. For example, the radar sensor ECU301and the central ECU302may dynamically agree on (e.g., by communicating over the line303or via a different communication means) on the reduction scheme or a modification thereof.

The solution may allow for an, e.g., up to 75%-reduction of data traffic from the radar sensor ECU301to the central ECU302.

Example 1: Reduction by Selecting Chirp Data

FIG.4shows an exemplary diagram visualizing a reduction of data within an MMIC401. The MMIC401may be a schematic simplification of the MMIC201shown inFIG.2andFIG.3.

According to the example shown inFIG.4, the MMIC401comprises three receiving branches, each for one receiving antenna (RX antenna1to RX antenna3). Each branch works as follows: A mixer multiplies a signal from the receiving antenna with a local oscillator signal and the result is fed to an amplifier and filter (“Amp+Filter”). The amplified and filtered result is analog-to-digital converted (using an analog-to-digital converter, ADC, with an ADC clock) and optionally down-sampled. The resulting digital signal from all branches is then further processed. Thus, each mixer has a receive input, a local oscillator input, and an output. The receive input of each mixer is coupled to a respective receiving antenna port. The local oscillator inputs are coupled to a local oscillator terminal. Each amplifier and filter unit has an input and an output. The input of each amplifier and filter unit is coupled to the output a corresponding mixer.

In the example shown inFIG.4, the resulting digital signal is compressed by selecting which chirp is to be processed (see step402). A random, pseudo-random or deterministic sequence can be used to select the chirps. Thus, after the optional down-conversion, a selection block, such as a multiplexor in hardware or software, can select which chip data is to be processed.

The selected chirps are then subject to a first stage FFT in a step403and the first stage FFT results are conveyed from the decentralized ECU301to the central ECU302in a step404. As an option, a selection code can be conveyed together with the FFT results to let the central ECU302know which chirps have been omitted and/or which chirps have been processed.

Example 2: Reduction by Selecting FFT Results

FIG.5shows an exemplary diagram visualizing a reduction of data occurring at a first stage FFT unit502. An MMIC501may be a schematic simplification of the MMIC201shown inFIG.2andFIG.3. The receiving branches of the MMIC501correspond to the receiving branches of the MMIC401explained above.

The resulting digital signal provided by the MMIC501is processed at the first stage FFT unit502as follows: In a step503, the first stage FFT is applied on (all) chirps. In a subsequent step504, a reduction is achieved by selecting only a portion of the FFT results to be processed. A random, pseudo-random or deterministic sequence can be used to select the FFT results.

These selected FFT results are conveyed from the decentralized ECU301to the central ECU302in a step505. As an option, a selection code can be conveyed together with the FFT results to let the central ECU302know which chirps have been omitted and/or which chirps have been processed.

Example 3: Reduction by Selecting Reception Channel

FIG.6shows an exemplary diagram visualizing a reduction of data occurring within an MMIC601, which may be a schematic simplification of the MMIC201shown inFIG.2andFIG.3.

According to an example shown inFIG.6, the MMIC601comprises three receiving branches, each for one receiving antenna (RX antenna1to RX antenna3). Each branch works as follows: A mixer multiplies a signal from the receiving antenna with a local oscillator signal and the result is fed to an amplifier and filter (“Amp+Filter”). The amplified and filtered result is conveyed to a multiplexer605. In this example, the multiplexer605has three inputs and a single output. A signal606controls which input of the multiplexer605is connected to its output. Hence, the signal606selects one of the receiving channels for a predefined amount of time.

The signal606is provided by a select signal602, which enables a random, pseudo-random or deterministic selection of RX channels. For example, each of the receiving channels can be selected at substantially the same rate.

The output of the multiplexer605is conveyed to an analog-to-digital converter (ADC), which is driven by an ADC clock.

The output of the ADC is fed to the first stage FFT unit, which determines FFT results (see step603). Next, the FFT results are conveyed from the decentralized ECU301to the central ECU302in a step604.

Further Embodiments and Advantages

It is noted that preferably all chirps are emitted and the signals received at the various antennas of the radar sensor ECU301are further processed by reducing the overall data to be conveyed towards the central ECU302.

The reduction may be achieved by reducing the number of chirps that are subject to further processing. In other words, not all chirps are further processed. The selection may be conducted according to a random or deterministic scheme.

In an exemplary use-case, several radar sensor ECUs are provided together with at least one central ECU in a vehicle.