Method and radar system for adaptive doppler window function selection to detect object

Abstract

A method and radar system for adaptive Doppler window function selection to detect an object. Systems and methods are provided for adaptive Doppler window function selection, and include a radar system that determines whether there is a dominant target in a sensing environment of the radar system based on received radar signals reflected from an object, and selecting a first window function or a second window function based on whether there is a dominant target in the sensed environment. The radar system performs a Doppler fast Fourier transform (FFT) process using the selected window function. When used to perform a Doppler FFT process, the first function and the second window function have different signal-to-noise ratio degradation. The radar system also determines information about the object based on performing the Doppler FFT process, the information including at least one of a position, a size, an orientation, a velocity, and an acceleration of the object.

Description

Technical Field

[0001] The present disclosure relates to radar systems and methods, and more particularly, to radar systems and methods that perform a Doppler Fast Fourier Transform (FFT) process using a window function. Background Art

[0002] This section provides background information related to the present disclosure which is not necessarily prior art.

[0003] Automotive radar sensors are used in vehicle sensing systems to determine information about objects in the vehicle environment, such as the location, size, orientation, velocity, and acceleration of objects in the vehicle environment. The sensed information can be used, for example, by other vehicle systems, such as autonomous driving systems and / or advanced driver assistance systems (ADAS), to control steering, braking, throttle, and / or other vehicle systems.

[0004] A multiple-input multiple-output (MIMO) radar system can use multiple transmit channels and receive channels. In order to allow the receive channel to distinguish the reflected signals originating from each transmit channel, the radar system can use a phase modulation code to modulate the phase of the transmit signal. The radar system can then use the transmit code to demodulate the received signal to recover the signal from each transmit channel and suppress the signal transmitted from other transmit channels. However, during demodulation, the energy of the suppressed signal from other transmit channels still exists and is distributed over the frequency band. The distributed energy from the suppressed signal present in the recovered signal is called a residue, and in some cases, a residue estimation and subtraction technique (REST: Residue Estimation And Subtraction Technique) is applied to remove the residue and increase the Doppler dynamic range of the radar system. In addition, in order to increase the Doppler dynamic range of the radar system, a window function can be used in combination with performing a Doppler FFT on the received signal. For example, a Chebyshev window function can be used. However, the use of a Chebyshev window function may result in a loss of signal-to-noise ratio (SNR). Summary of the invention

[0005] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0006] The present invention provides a radar system, the radar system includes a processor and a memory, the processor and the memory are configured to use the multiple transmission channels to transmit radar signals by performing binary phase modulation (BPM) on each of the multiple transmission channels using different BPM codes, and receive the radar signal reflected from at least one object with a receiving channel. The processor and the memory are also configured to determine whether there is a dominant target in the sensing environment of the radar system based on the received radar signal. The processor and the memory are also configured to select one of a first window function and a second window function based on whether there is a dominant target in the sensing environment. The processor and the memory are also configured to perform a Doppler fast Fourier transform (FFT) process using a window function selected from the first window function and the second window function, and when used in performing the Doppler FFT process, the first window function and the second window function have different signal-to-noise ratio (SNR) degradation. The processor and the memory are also configured to determine information about the object based on performing the Doppler FFT process, the information including at least one of the position, size, direction, speed and acceleration of the object.

[0007] In other aspects, the SNR degradation of the first window function is less than the SNR degradation of the second window function.

[0008] In other aspects, a first window function is selected by the processor for performing a Doppler FFT in response to determining that a dominant target is not present in the sensing environment of the radar system, and a second window function is selected by the processor for performing a Doppler FFT in response to determining that a dominant target is present in the sensing environment of the radar system.

[0009] In other aspects, the processor and memory are further configured to, in response to determining that the dominant target is present in the sensing environment of the radar system, perform a residual estimation and subtraction technique (REST) ​​to remove residuals generated by performing BPM on each of the multiple transmit channels using a different BPM code.

[0010] In other aspects, the radar system is located in a vehicle and information about the object is transmitted to a vehicle system that controls at least one of a steering system, a braking system, and a throttle system of the vehicle based on the information about the object.

[0011] In other aspects, a vehicle system includes at least one of an autonomous driving system and a driver assistance system.

[0012] In other aspects, the processor and memory are further configured to determine whether a dominant target is present in a sensing environment of the radar system by determining a total amplitude of a received signal in a current receive bin and a noise estimate from a previous frame and in response to a ratio of the total amplitude to the noise estimate being greater than a predetermined ratio threshold.

[0013] A method is also provided, the method comprising the steps of: using a radar system having a processor and a memory, transmitting a radar signal using the multiple transmit channels by performing binary phase modulation (BPM) on each of the multiple transmit channels using different BPM codes; and using the radar system, receiving the radar signal reflected from at least one object using a receive channel. The method also includes using the radar system to determine whether there is a dominant target in a sensing environment of the radar system based on the received radar signal. The method also includes using the radar system to select one of a first window function and a second window function based on whether the dominant target exists in the sensing environment, the first window function and the second window function having different signal-to-noise ratio (SNR) degradations. The method also includes using the radar system to perform a Doppler Fast Fourier Transform (FFT) process using a window function selected from the first window function and the second window function. The method also includes using the radar system to determine information about the object based on performing a Doppler FFT process, the information including at least one of the position, size, orientation, velocity and acceleration of the object.

[0014] In other aspects, the SNR degradation of the first window function is less than the SNR degradation of the second window function.

[0015] In other aspects, a first window function is selected to perform a Doppler FFT in response to determining that no dominant target is present in the sensing environment of the radar system, and a second window function is selected to perform a Doppler FFT in response to determining that a dominant target is present in the sensing environment of the radar system.

[0016] In other aspects, the method includes the following steps: in response to determining that the dominant target is present in the sensing environment of the radar system, using the radar system to perform a residual estimation and subtraction technique (REST) ​​to remove residuals generated by performing BPM on each of the multiple transmission channels using a different BPM code.

[0017] In other aspects, the radar system is located in a vehicle, and the method further includes transmitting the information about the object to a vehicle system, the vehicle system controlling at least one of a steering system, a braking system, and a throttle system of the vehicle based on the information about the object.

[0018] In other aspects, a vehicle system includes at least one of an autonomous driving system and a driver assistance system.

[0019] In other aspects, determining whether a dominant target exists in a sensing environment of a radar system includes: determining, using the radar system, a total amplitude of a received signal in a current receiving bin and a noise estimate from a previous frame; and determining, using the radar system, that a dominant target exists in response to a ratio of the total amplitude to the noise estimate being greater than a predetermined ratio threshold.

[0020] Further areas of applicability will become apparent from the description provided herein.The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are for illustrative purposes only and may not depict all possible implementations, and are not intended to limit the scope of the present disclosure.

[0022] Figure 1 is a block diagram of a vehicle having a radar system according to the present disclosure.

[0023] Figure 2 is another block diagram of a vehicle having a radar system according to the present disclosure.

[0024] Figure 3 is a graph showing the maximum sidelobe level (SLL) and processing loss (dB) for different window functions.

[0025] Figure 4 is a flow chart of a method for selecting a window function according to the present disclosure.

[0026] Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0027] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0028] The present disclosure relates to a radar system that selects and utilizes different window functions in conjunction with performing Doppler FFT on received radar signals according to the characteristics of the radar sensing environment. For example, as discussed in further detail below, if there is a dominant target in the sensing environment, a window function with a higher correlation dynamic range and a lower correlation SNR, such as a Chebyshev window function, can be used. Due to the presence of a dominant target, even if the signal loss increases due to a lower SNR and increased noise, the dominant target can be detected. If there is no dominant target, a window function with a higher correlation SNR and a lower correlation dynamic range, such as a Taylor window function, can be used. In this way, due to the absence of a dominant target, a smaller target can be detected by using a window function with a higher correlation SNR, reduced noise and a lower correlation signal loss. Therefore, when selecting an appropriate window function in conjunction with the Doppler FFT for a received signal, the present disclosure recognizes a compromise between a higher SNR and a lower dynamic range on the one hand, and recognizes a compromise between a lower SNR and a higher dynamic range on the other hand. Recognizing this tradeoff, the radar system and method of the present disclosure selects an appropriate window function based on the characteristics of the radar sensing environment, specifically, based on whether the dominant target is present in the radar sensing environment and is detected. Although this example utilizes Chebyshev window function and Taylor window function, recognizing the tradeoff between SNR degradation and dynamic range / maximum SLL, other window functions can be used according to other tradeoff factors and aspects of the window function. For example, different window functions can be used to consider the tradeoffs of SNR loss, maximum SLL, main lobe width, SLL roll off, etc. In addition or alternatively, tradeoffs of other factors or aspects can be used and adapted by using different window functions.

[0029] In this way, the radar system according to the present disclosure can adaptively use different window functions based on the characteristics of the radar sensing environment, and select a window function with desired dynamic range and SNR characteristics according to whether there is a dominant target in the radar sensing environment.

[0030] refer to Figure 1 and Figure 2 , shows a radar system 100 of a vehicle 102 according to the present disclosure. The radar system 100 transmits a signal 104 that is reflected from an object 106 in the environment of the vehicle 102. Figure 1 1 is a schematic diagram of a radar system 100. A single object 106 is shown for illustration purposes, but in reality the object 106 may include multiple objects, including a dominant target object and one or more smaller non-dominant target objects. The radar system 100 receives a signal 108 reflected from the object 106. Based on the characteristics of the received signal 108, the radar system 100 determines information about the object, such as the location, size, orientation, velocity, and acceleration of the object 106.

[0031] The radar system 100 includes a processor 200 and a memory 202, the memory 202 storing code executed by the processor to perform the functions required to transmit and receive signals 104, 108 and determine information about an object 106 based on characteristics of the received signals 108. Although the exemplary implementation shows a single processor 200, multiple processors and / or modules working together may be used instead. The radar system 100 includes a transmitter / receiver 204 that transmits and receives signals 104, 108. The transmitter / receiver 204 includes one or more transmit (Tx) antennas and one or more receive (Rx) antennas for transmitting and receiving signals 104, 108. For example, the processor 200 executes transmit / receive code 206 stored in the memory 202 to send and receive signals 104, 108.

[0032] The processor 200 may control the transmitter / receiver 204 to operate two transmit channels and one receive channel. As described above, in order for the processor 200 to distinguish the signal 108 received by the receive channel as originating from each transmit channel, the processor 200 may modulate the phase of each transmit signal 104 using a phase modulation code. For example, the processor 200 may perform binary phase modulation (BPM) using a BPM code 208 also stored in the memory 202. The processor 200 may then demodulate the received signal 108 using the BPM code 208 to recover the received signal sent from each transmit channel and suppress the signal sent from another transmit channel. Although this example includes two transmit channels and one receive channel, other combinations of transmit and receive channels may be used according to the present disclosure. For example, the radar system 100 may include four transmit channels and one receive channel. The processor 200 may perform range FFT processing on the received demodulated signal by executing a range FFT code 210 stored in the memory 202 to determine the distance information about the object 106.

[0033] When demodulating the received signal 108, the energy of the suppressed signal from another transmit channel still exists and is distributed on the frequency band of the demodulated signal. The distributed energy from the suppressed signal present in the recovered demodulated signal is called residual. The processor 200 can perform a residual estimation and subtraction technique (REST) ​​to remove the residual and increase the Doppler dynamic range of the radar system 100. The residual present in the demodulated signal is caused by or due to the lack of perfect orthogonality between the signals applied to each transmit channel. The residual present in the recovered demodulated signal from a specific transmit channel (e.g., composed of the superposition of residuals from other transmit channels). The level or intensity of the residual is related to the orthogonality between the received signal level and the transmit signal. The cross-correlation of the phase code for each transmit channel determines the orthogonality between the transmit signals and also determines the shape of the spectrum of the residual.

[0034] The REST process may include a plurality of processing steps performed by the processor 200 based on the REST code 218 stored in the memory. As a first step, the processor 200 may demodulate the received signal 108 based on the BPM code 208 used by the transmit channel to transmit the signal 104. As a next step, the processor 200 may identify the signal in the subchannel by identifying a frequency bin that is higher than the peak residual from other channels. Then, the signal is isolated from the residual by using a filter in the frequency domain to output the signal in a different frequency domain. As a next step, the processor 200 may estimate the residual produced by each subchannel when forming the other subchannels. For example, the processor 200 may determine the cross-correlation between the phase codes from all other subchannels, calculate the FFT of each resulting cross-correlation code, and then convolve it with one of the signals from the previous step. As another example, the processor 200 may convert one of the signals from the previous step to the time domain by a reduced dimension inverse FFT, modulate the resulting time domain signal using the original phase code applied to the subchannel and the complex conjugate of the phase code applied to extract another subchannel, and then convert the modulated signal back to the frequency domain by FFT. As a next step, for each subchannel, processor 200 may subtract the estimated residual from each corresponding suppressed subchannel to produce a residual-canceled signal.As a next step, the process may optionally be repeated one or more times after subtracting the estimated residual.

[0035] Additional details for implementing REST are provided in applicant's commonly assigned patent US9,952,319, entitled "Residue cancellation for automated vehicle MIMO RADAR," issued on April 24, 2018, the entire contents of which are incorporated herein by reference.

[0036] Performing the REST process increases the dynamic range of the radar system 100 in the Doppler domain. However, the REST process is not always necessary. For example, if there is a dominant target, REST is required because the reflected signal from the dominant target can hide smaller targets in its own residual. Therefore, REST is required to remove the residual to process the received signal and identify the received signal reflected from any possible smaller targets in the sensing environment. However, when there is no dominant target in the sensing environment, the noise in the received signal 108 will be more dominant than the residual, and the REST process will not be as helpful as when there is a dominant target.

[0037] For these reasons, the processor 200 determines whether to perform REST by analyzing the predetermined REST criteria using the REST determination code and criteria 212. For example, for each receive bin, the processor 200 determines the total amplitude of the bin to preliminarily determine whether there is a dominant target. The total amplitude is then compared with the noise estimate from the previous signal receive frame. If the ratio of the total amplitude in the current bin to the noise estimate from the previous frame is greater than a predetermined ratio threshold, it is determined that there is a dominant target in the sensing environment, and the processor 200 continues to perform REST on the current receive signal bin. If the ratio is less than the predetermined ratio threshold, the amplitude is close to the noise, which indicates that there is no dominant target in the environment. In this case, the processor 200 determines that the current receive signal bin does not require REST processing. The noise estimate from the previous frame is used because the noise estimate is not determined until the processing after the Doppler FFT processing described below. Therefore, the processor 200 uses the most recent noise estimate from the previous frame to determine the ratio of amplitude to noise for evaluating the REST criteria and determining whether REST processing should be performed.

[0038] After determining whether to perform REST processing, the processor 200 then uses the window selection code 214 stored in the memory 202 to select the window function to be used to perform the Doppler FFT. A window function is, for example, a mathematical function that is zero-valued outside a selected interval. For example, the window function may be symmetrical, approaching a maximum value near the middle of the interval, and then gradually decreasing from the middle. When the window function is applied to another waveform or data sequence, the resulting product becomes zero-valued outside the interval, and the non-zero remainder is the portion of the waveform or data sequence that overlaps with the window function, thereby creating a view of the waveform or data sequence through the window function, that is, the portion of the waveform or data sequence that overlaps with the window function.

[0039] As described above, the Chebyshev window function can be used for Doppler FFT processing and provides a relatively high dynamic range and a relatively low and uniform SLL for the Doppler FFT compared to other window functions. For example, for a given main lobe width, the Chebyshev window function minimizes the Chebyshev norm (also referred to as the consistent norm, the supremum norm, or the infinity norm) of the side lobes of the function. However, the use of the Chebyshev window function may result in SNR loss. For example, a Chebyshev window function with a 40dB SLL may have a 1.07dB SNR or processing loss compared to a rectangular window. When there is a dominant target, the increased SNR loss is not a problem because the dominant target can still be detected even in the case of increased SNR loss. In this way, the higher dynamic range of the Chebyshev window function can be used for an increased dynamic range to possibly show smaller targets.

[0040] However, the residual level can be significantly higher than the sidelobe level of the Chebyshev window used. For example, for a double-dwell radar implementation using 512 chirps per frame, the average BPM residual level is about 28dB lower than the peak, with a maximum of 20dB. For a single-dwell radar implementation using 256 chirps per frame, the average BPM residual is 26dB lower than the peak, with a maximum of 16dB. When a dominant target is present and REST is performed, the residual is subtracted and the SLL of the Doppler FFT using a Chebyshev window can be utilized. However, when REST is not performed, the 26dB / 28dB residual level remains unchanged, and the lower Chebyshev SLL will not beneficially affect the processing of the Doppler FFT.

[0041] In this way, when REST processing is not performed, the system and method of the present disclosure advantageously utilize and select different window functions for Doppler FFT processing of the bin. For example, the system and method of the present disclosure can select and utilize a window function with a higher correlation SNR. For another example, for bins that do not perform REST, a Taylor window function with a higher SNR (i.e., lower SNR loss) can be used in Doppler FFT processing compared to a Chebyshev window function. When REST processing is not performed, the use of the Taylor window function can increase the probability of detecting a smaller target at a longer distance. In this way, when there is a dominant target and REST processing is performed, the system and method of the present invention can select and utilize a window function with a higher dynamic range with a larger SNR loss (i.e., higher SNR degradation), such as a Chebyshev window function. In addition, when there is no dominant target and REST processing is not performed, the system and method of the present disclosure can select and utilize a window function with a lower dynamic range and a higher SNR (i.e., less SNR loss or less SNR degradation), such as a Taylor window function. The Taylor window function is similar to the Chebyshev window function, except that the Taylor window function allows a trade-off between mainlobe width and sidelobe level, while the Chebyshev window has the narrowest possible mainlobe for a specified sidelobe level. Thus, the Taylor window function provides an approximation that avoids the discontinuity at the edges of the Chebyshev window due to the equiripple condition by allowing the equiripple to weaken at the edges.

[0042] refer to Figure 3 , graph 300 shows the relationship between the processing loss and SLL of the Taylor window function and the Chebyshev window function. In graph 300, the processing loss (dB) is shown on the vertical axis and the maximum SLL (dB) is shown on the horizontal axis. In graph 300, curve 302 represents the Taylor window function, and curve 304 represents the Chebyshev window function. As shown, when the maximum SLL is greater than 37dB, the Chebyshev window function has a smaller processing loss and a smaller resulting SNR loss than the Taylor window function. As further shown, for a maximum SLL less than 37dB, the Taylor window function has a smaller processing loss and a smaller resulting SNR loss than the Chebyshev window function.

[0043] In an example implementation of the system and method of the present disclosure, when there is a dominant target and REST is performed, the processor 200 may select and utilize a Chebyshev window function with an SLL of 40dB and a processing / SNR loss of -1.07dB. In addition, when there is no dominant target and REST is not performed, the processor 200 may select and utilize a Taylor window function. A Taylor window function at least 3dB lower than the maximum residual level of the BPM cross-code may be selected to avoid false detection. In addition, different Taylor window functions may be selected based on whether the radar system 100 uses a single dwell waveform (i.e., 256 chirps per frame) or a dual dwell waveform (i.e., 512 chirps per form). For example, with a single dwell implementation, when there is no dominant target and REST is not performed, the maximum residual level is approximately 16dB. In this case, the processor 200 may select a Taylor window function with an SLL of 20dB and a processing / SNR loss of approximately -0.16dB. Compared with the Chebyshev window function with a processing / SNR loss of -1.07dB, selecting this Taylor window function improves SNR and reduces SNR loss by about 0.91dB. Similarly, for dual-dwell implementation, when there is no dominant target and REST is not performed, the maximum residual level is about 20dB. In this case, the processor 200 can select a Taylor window function with a SLL of 25dB and a processing / SNR loss of about -0.34dB. Compared with the Chebyshev window function with a processing / SNR loss of -1.07dB, selecting this Taylor window function improves SNR and reduces SNR loss by about 0.73dB.

[0044] Reference again Figure 1 and Figure 2 Once the processor 200 selects the window function for the current receive bin signal 108, the processor 200 uses the Doppler FFT code 216 stored in the memory 202 and performs a Doppler FFT on the received signal 108 using the selected window function. After performing the Doppler FFT on the received signal 108, and if the processor 200 previously determined that REST was needed, the processor performs REST using the REST code 218.

[0045] Processor 200 may then perform object detection based on the processed signals using detection code 218 stored in memory 202 and determine information about object 106 , such as the location, size, direction, velocity, and acceleration of object 106 .

[0046] In addition, the processor 200 can transmit information about the object 106 (such as the location, size, orientation, speed, and acceleration of the object 106) to other vehicle systems 220, such as an autonomous driving system and / or an advanced driver assistance system (ADAS), etc. The other vehicle systems can then utilize and process the information about the object 106 to appropriately control the steering, braking, throttle, and / or other vehicle operations of the vehicle 102 based on the information about the object 106.

[0047] refer to Figure 4 , a method 400 for selecting a window function and performing a Doppler FFT using the selected window function according to the present disclosure is shown. The method 400 can be executed by the processor 200 using code stored in the memory 202 and starts at step 404. At step 406, the processor 200 performs BPM modulation on the transmit signal 104 transmitted by different transmit channels. As described above, different BPM codes 208 are used for different transmit channels so that the signals received by the receive channels can be distinguished and differentiated from each other. At step 408, the processor 200 receives the reflected signal 108. At step 410, the processor 200 performs a ranging FFT on the received signal 108 using the range FFT code 210 stored in the memory.

[0048] In step 412, the processor 200 determines whether REST is required. For example, as described above, the processor 200 analyzes a predetermined REST criterion to determine whether REST is required for the current received signal bin using the REST determination and criterion code 212 stored in the memory 202. For example, the processor 200 determines whether there is a dominant target based on the total amplitude of the current bin and the noise estimate from the previous frame. If the ratio of the total amplitude in the current bin to the noise estimate from the previous frame is greater than a predetermined ratio threshold, the processor 200 determines that there is a dominant target in the environment and REST processing should be performed. If the ratio is less than a predetermined ratio threshold, the amplitude is close to the noise, which indicates that there is no dominant target in the environment. In this case, the processor 200 determines that the current received signal bin does not require REST processing.

[0049] When the processor 200 determines that REST is needed at step 412, it has been determined that a dominant target exists and a higher dynamic range is preferred. In this case, the processor 200 proceeds to step 416 and selects a Chebyshev window function for Doppler FFT processing of the received signal bin.

[0050] When the processor 200 determines that REST processing is not required at step 412, it is not determined that a dominant target exists, and a higher SNR is preferred. In this case, the processor 200 proceeds to step 418 to select a Taylor window function for Doppler FFT processing of the received signal bin.

[0051] After selecting the appropriate window function at step 416 or step 418, the processor 200 then proceeds to step 420 or step 422 and uses the selected window function to perform Doppler FFT processing. Specifically, at step 420, when REST is required, the processor 200 uses the Chebyshev window function to perform Doppler FFT. Specifically, at step 422, when REST is not required, the processor 200 uses the Taylor window function to perform Doppler FFT. Corresponding to applicable window functions (e.g., Chebyshev and Taylor window functions), different sets of window coefficients 215 can be stored in the memory 202. At steps 420 and 422, the processor 200 loads the appropriate window coefficient set 215 for the selected window function by retrieving and loading the appropriate window coefficient set 215 from the memory 202. Then, the processor 200 uses the Doppler FFT code 216 stored in the memory 202, using the appropriate window coefficient corresponding to the selected window function, to perform Doppler FFT processing on the received signal bin.

[0052] At step 423, having determined at step 412 that REST is required and after performing the Doppler FFT using the Chebyshev window function, the processor 200 then performs REST processing on the current receive signal bin using the REST code 218 stored in memory.

[0053] After performing REST at step 423, and after performing Doppler FFT using a Taylor window function without performing REST at step 422, the processor 200 then performs object detection at step 424 based on the received signal processed using the detection code 219 stored in the memory 202. For example, the processor 200 can perform object detection based on the processed signal and determine information about the object 106, such as the position, size, direction, velocity, and acceleration of the object 106. For example, the processor 200 can perform object detection using the detection code 218 stored in the memory 202.

[0054] The processor then loops back to step 406 and performs another iteration of sending, receiving and processing signals.

[0055] Thus, the present disclosure provides systems and methods for adaptive Doppler window function selection and received signal processing based on characteristics of the sensed environment.

[0056] The foregoing description of the embodiments has been provided for the purpose of illustration and description, and is not intended to be exhaustive or limit the present disclosure. The individual elements or features of a particular embodiment are generally not limited to the particular embodiment, but where applicable, they are interchangeable and can be used in another embodiment, even if not explicitly shown or described. Various embodiments may also be changed in many ways. Such changes should not be considered as departing from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure. Although each embodiment is described as having certain features above, any one or more of those features described with respect to any embodiment of the present disclosure may be implemented in the features of any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the replacement of one or more embodiments with each other is still within the scope of the present disclosure.

[0057] Exemplary embodiments are provided so that the present disclosure will be thorough and will fully convey its scope to those skilled in the art. Specific details, including examples of specific components, devices, and methods, are set forth to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that exemplary embodiments may be embodied in many different forms, and that they should not be construed as limiting the scope of the present disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known techniques are not described in detail.

[0058] In the written description and claims, one or more steps within a method may be performed in a different order (or simultaneously) without changing the principles of the present disclosure. Similarly, one or more instructions stored in a non-transitory computer-readable medium may be executed in a different order (or simultaneously) without changing the principles of the present disclosure. Unless otherwise indicated, numbering or other labeling of instructions or method steps is for ease of reference and does not indicate a fixed order.

[0059] The spatial and functional relationships between elements (e.g., between modules) are described using various terms, including "connected," "joined," "interfacing," and "coupled." Unless explicitly described as "directly," when describing a relationship between a first element and a second element in the above disclosure, the relationship includes a direct relationship between the first element and the second element without other intermediate elements, and an indirect relationship between the first element and the second element with one or more intermediate elements (spatially or functionally) present.

[0060] The phrase "at least one of A, B, and C" should be interpreted to mean a logical (A or B or C), using a non-exclusive logical OR, and should not be interpreted to mean "at least one of A, at least one of B, and at least one of C". The term "set" does not necessarily exclude the empty set. The term "non-empty set" may be used to indicate the exclusion of the empty set. The term "subset" does not necessarily require a proper subset. In other words, a first subset of a first set may be coextensive with (equal to) the first set.

[0061] In the drawings, the direction of the arrow indicated by the arrow generally indicates the flow of information (e.g., data or instructions) of interest to the illustration. For example, when element A and element B exchange various information but the information sent from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not mean that no other information is sent from element B to element A. In addition, for information sent from element A to element B, element B may send a request for the information to element A or receive an acknowledgement of the information.

[0062] In this application, including the following definitions, the term "module" or the term "controller" may be replaced with the term "circuit". The term "module" may refer to processor hardware (shared, dedicated, or group) that executes code and memory hardware (shared, dedicated, or group) that stores code executed by the processor hardware, which is part of the processor hardware or includes the processor hardware.

[0063] The module may include one or more interface circuits. In some examples, the interface circuit may implement a wired or wireless interface connected to a local area network (LAN) or a wireless personal area network (WPAN). Examples of LANs are Institute of Electrical and Electronics Engineers (IEEE) standard 802.11-2016 (also referred to as WIFI wireless networking standards) and IEEE standard 802.3-2015 (also referred to as Ethernet wired networking standards). Examples of WPANs are Bluetooth wireless networking standards from Bluetooth Special Interest Group (SIG) (including core specification versions 3.0, 4.0, 4.1, 4.2, 5.0, and 5.1 from Bluetooth SIG).

[0064] The module can communicate with other modules using interface circuits. Although the module can be described in the present disclosure as being in logical communication directly with other modules, in various implementations, the module can actually communicate via a communication system. The communication system includes physical and / or virtual networking devices, such as hubs, switches, routers, and gateways. In some implementations, the communication system is connected to or passes through a wide area network (WAN) such as the Internet. For example, the communication system can include multiple LANs connected to each other through the Internet or point-to-point leased lines using technologies including multi-protocol label switching (MPLS) and virtual private networks (VPNs).

[0065] In various implementations, the functionality of a module may be distributed among multiple modules connected via a communication system. For example, multiple modules may implement the same functionality distributed by a load balancing system. In another example, the functionality of a module may be split between a server (also referred to as a remote or cloud) module and a client (or user) module. For example, a client module may include a native or web application that executes on a client device and communicates with a server module over a network.

[0066] As described above, the term code may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. Shared processor hardware includes a single microprocessor that executes some or all of the code from multiple modules. Group processor hardware includes a microprocessor that, in combination with an additional microprocessor, executes some or all of the code from one or more modules. References to multiple microprocessors include multiple microprocessors on discrete dies, multiple microprocessors on a single die, multiple cores of a single microprocessor, multiple threads of a single microprocessor, or a combination of the above.

[0067] Shared memory hardware includes a single memory device that stores some or all code from multiple modules. Group memory hardware includes a memory device that combines with other memory devices to store some or all code from one or more modules.

[0068] The term memory hardware is a subset of the term computer-readable medium. The term computer-readable medium as used herein does not include transient electrical or electromagnetic signals propagating through a medium (e.g., on a carrier wave); the term computer-readable medium is therefore considered to be tangible and non-transitory. Non-limiting examples of non-transitory computer-readable media are non-volatile memory devices (e.g., flash memory devices, erasable programmable read-only memory devices, or mask read-only memory devices), volatile memory devices (e.g., static random access memory devices or dynamic random access memory devices), magnetic storage media (e.g., analog or digital magnetic tape or hard drive), and optical storage media.

[0069] The apparatus and methods described in this application may be implemented in part or in whole by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions contained in a computer program. Such apparatus and methods may be described as computerized apparatus and computerized methods. The above-described functional blocks and flow chart elements serve as software specifications, which may be translated into a computer program by the routine work of a skilled technician or programmer.

[0070] The computer program includes processor executable instructions stored on at least one non-transitory computer readable medium. The computer program may also include or rely on stored data. The computer program may include a basic input / output system (BIOS) that interacts with the hardware of the special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0071] The computer program may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language) or JSON (JavaScript Object Notation), (ii) assembly code, (iii) object code generated by a compiler from source code, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. By way of example only, the source code may be written in a language including C, C++, C#, Objective C, Swift, Haskell, Go, SQL, R, Lisp, Fortran, Perl, Pascal, Curl, OCaml, HTML5 (Hypertext Markup Language Fifth Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Visual Lua, MATLAB, SIMULINK, and

Claims

1. A radar system, comprising a processor and a memory, wherein the processor and the memory are configured to: transmitting radar signals using the plurality of transmit channels by performing BPM on respective transmit channels of the plurality of transmit channels using different binary phase modulation (BPM) codes; receiving, using a receive channel, a radar signal reflected from at least one object; determining, based on the received radar signal, whether a dominant target exists in a sensing environment of the radar system; selecting one of a first window function and a second window function based on whether the dominant target exists in the sensing environment; Performing a Doppler Fast Fourier Transform (FFT) process using a window function selected from the first window function and the second window function, wherein the first window function and the second window function have different signal-to-noise ratio (SNR) degradations when being used to perform the Doppler FFT process; as well as Based on performing the Doppler FFT process, information about the at least one object is determined, the information including at least one of a position, a size, an orientation, a velocity, and an acceleration of the at least one object.

2. The radar system according to claim 1, wherein: The SNR degradation of the first window function is less than the SNR degradation of the second window function.

3. The radar system of claim 2, wherein: In response to determining that the dominant target is not present in the sensing environment of the radar system, the first window function is selected by the processor for performing the Doppler FFT; as well as In response to determining that the dominant target is present in the sensing environment of the radar system, the second window function is selected by the processor for performing the Doppler FFT.

4. The radar system according to claim 1, wherein: The processor and the memory are further configured to, in response to determining that the dominant target is present in the sensing environment of the radar system, perform a residual estimation and subtraction technique REST to remove residuals resulting from performing BPM on each of the plurality of transmit channels using a different BPM code.

5. The radar system according to claim 1, wherein: The radar system is located in a vehicle, and information about the object is transmitted to a vehicle system, which controls at least one of a steering system, a braking system, and a throttle system of the vehicle based on the information about the object.

6. The radar system according to claim 5, wherein: The vehicle system includes at least one of an autonomous driving system and a driver assistance system.

7. The radar system according to claim 1, wherein: The processor and the memory are further configured to determine whether the dominant target exists in the sensing environment of the radar system by the following steps: determining a total amplitude of a received signal in a current receive bin and a noise estimate from a previous frame; as well as In response to a ratio of the total amplitude to the noise estimate being greater than a predetermined ratio threshold, it is determined that the dominant target is present.

8. A method for performing adaptive Doppler window function selection to detect an object, the method comprising the following steps: Using a radar system having a processor and a memory, performing BPM on each of a plurality of transmit channels by using different binary phase modulation (BPM) codes, and transmitting radar signals using the plurality of transmit channels; Using the radar system, receiving a radar signal reflected from at least one object using a receive channel; determining, using the radar system, whether a dominant target exists in a sensing environment of the radar system based on the received radar signal; Based on whether the dominant target exists in the sensing environment, selecting, by the radar system, one of a first window function and a second window function, the first window function and the second window function having different signal-to-noise ratio (SNR) degradations; Using the radar system, performing a Doppler Fast Fourier Transform (FFT) process using a window function selected from the first window function and the second window function; as well as Using the radar system, information about the at least one object is determined based on performing the Doppler FFT process, the information including at least one of a position, a size, an orientation, a velocity, and an acceleration of the at least one object.

9. The method according to claim 8, wherein: The SNR degradation of the first window function is less than the SNR degradation of the second window function.

10. The method according to claim 9, wherein: In response to determining that the dominant target is not present in the sensing environment of the radar system, selecting the first window function to perform the Doppler FFT; as well as In response to determining that the dominant target is present in the sensing environment of the radar system, the second window function is selected to perform the Doppler FFT.

11. The method according to claim 8, further comprising the steps of: In response to determining that the dominant target is present in the sensing environment of the radar system, a residual estimation and subtraction technique REST is performed with the radar system to remove residuals resulting from performing BPM on each of the plurality of transmit channels using a different BPM code.

12. The method according to claim 8, wherein: The radar system is located in a vehicle, and the method further includes the step of transmitting information about the object to a vehicle system, the vehicle system controlling at least one of a steering system, a braking system, and a throttle system of the vehicle based on the information about the object.

13. The method according to claim 12, wherein: The vehicle system includes at least one of an autonomous driving system and a driver assistance system.

14. The method according to claim 8, wherein: Determining whether the dominant target exists in the sensing environment of the radar system includes: determining, using the radar system, a total amplitude of a received signal in a current receive bin and a noise estimate from a previous frame; and With the radar system, the presence of the dominant target is determined in response to a ratio of the total amplitude to the noise estimate being greater than a predetermined ratio threshold.

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