Radar signal transmit power shaping and processing

Abstract

A radar apparatus includes a radar front end and a radar processor. The radar front end includes a transmit signal generation circuit for generating a radar transmit signal sequence including a plurality of radar transmit signals, and a power shaping component configured to receive the plurality of radar transmit signals and output the plurality of radar transmit signals having a plurality of different power levels. The radar front end includes a transmitter for transmitting the plurality of radar transmit signals based on the plurality of different power levels, where the plurality of different power levels are based on a power distribution associated with a window of digitized samples applied to reflections of the transmitted plurality of radar transmit signals. The radar processor is configured to apply the window for a slow time of the digitized sample of the reflection prior to velocity processing.

Description

Technical Field

[0001] The present invention relates to a radar device and method for shaping and processing radar signal transmission power. Background Art

[0002] Many systems rely on radar to provide accurate information about the surrounding environment. For example, modern vehicles use radar to implement advanced driver assistance systems (ADAS) and autonomous driving (AD), which perform functions such as adaptive cruise control, automatic steering, and emergency braking. In some cases, vehicle radar systems use radar modulation schemes (e.g., frequency-modulated continuous wave (FMCW) radar), which modulate the frequency of radar signals in a sequence commonly referred to as a radar chirp or simply a chirp within the 76 gigahertz (GHz) to 81 GHz frequency band. Radar systems using these types of radar modulation schemes sense the surrounding environment by transmitting a sequence of radar chirps, receiving the reflections of the radar chirps after they are reflected from one or more objects, and processing the received reflections to obtain the distance distribution of one or more objects and the speed of the objects. To provide a more robust and accurate perception of the surrounding environment, radar systems implement various radar transmission and signal processing methods. Summary of the Invention

[0003] In a first embodiment, a radar front end includes a transmission signal generation circuit, a power shaping component, and a transmitter. The transmission signal generation circuit is configured to generate a radar transmission signal sequence including a plurality of radar transmission signals. The power shaping component is configured to receive the plurality of radar transmission signals of the radar transmission signal sequence and output the plurality of radar transmission signals having a plurality of different power levels. The transmitter is configured to transmit the plurality of radar transmission signals of the radar transmission signal sequence based on the plurality of different power levels.

[0004] In some aspects of the first embodiment, the plurality of different power levels correspond to a power distribution associated with a window applied to digitized samples of the received reflections of the plurality of transmitted radar transmission signals at a radar processor coupled to the radar front end. In some aspects, the window is applied in the slow time domain of the digitized samples. In some aspects, if the window is only applied at the radar processor, the power distribution corresponds to the square root of the weighted coefficient values of the window. In some aspects, the radar processor applies the window before performing a velocity fast Fourier transform (FFT) process. In some aspects, the radar processor performs distance FFT processing on the digitized samples in the fast time domain to estimate the distance distribution based on the digitized samples of the received reflections before applying the window. In some aspects, the radar processor applies a first window in the fast time domain before the distance FFT.

[0005] In some aspects of the first embodiment, the transmitter includes a power amplifier that is configured to receive the output from the power shaping component and convert the output into a signal including the plurality of radar transmission signals at a plurality of different amplification power levels before transmission.

[0006] In some aspects of the first embodiment, the transmission signal generation circuit generates the radar transmission signal sequence including the plurality of radar transmission signals with an initial power distribution including a constant power level, and the power shaping component modifies the initial power distribution into the plurality of different power levels. In some aspects, the transmitter includes a normalization component that further modifies the output of the power shaping component such that the total transmission power budget for transmitting the plurality of radar transmission signals is substantially the same as if the plurality of radar transmission signals were transmitted at a constant power level. In some aspects, the plurality of different power levels are determined based on a power distribution associated with a window applied to digital samples of reflections of the plurality of transmitted radar transmission signals prior to slow-time velocity processing.

[0007] In a second embodiment, a radar device includes a radar front end and a radar processor. The radar front end includes a transmission signal generation circuit configured to generate a radar transmission signal sequence including a plurality of radar transmission signals; and a power shaping component configured to receive the plurality of radar transmission signals and output the plurality of radar transmission signals with a plurality of different power levels. The radar front end includes a transmitter configured to transmit the plurality of radar transmission signals based on the plurality of different power levels, wherein the plurality of different power levels are based on a power distribution associated with a window applied to digital samples of reflections of the plurality of transmitted radar transmission signals. The radar processor is configured to apply the window in the slow time of the digital samples of the reflections prior to velocity processing.

[0008] In some aspects of the second embodiment, the radar front end includes a receiver configured to receive the reflections of the plurality of transmitted radar transmission signals, the receiver including an analog-to-digital converter (ADC) configured to convert the reflections into the digital samples.

[0009] In some aspects of the second embodiment, if the window is applied only at the radar processor, the power distribution corresponds to the square root of the weighted coefficient value of the window.

[0010] In some aspects of the second embodiment, the transmitter includes a power amplifier configured to receive the output from the power shaping component and convert the output into a signal including the plurality of radar transmission signals at a plurality of different amplification power levels prior to transmission.

[0011] In some aspects of the second embodiment, the transmit signal generation circuit generates the radar transmit signal sequence including the plurality of radar transmit signals with an initial power distribution including a constant power level, and the power shaping component modifies the initial power distribution to the plurality of different power levels based on the power distribution.

[0012] In a third embodiment, a method includes generating a plurality of radar transmit signals at a constant power level and modifying the constant power level of the plurality of radar transmit signals to a plurality of power levels according to a power distribution. The method further includes transmitting the plurality of radar transmit signals based on the plurality of power levels.

[0013] In some aspects of the third embodiment, the method includes: receiving reflections of the plurality of radar transmit signals; converting the received reflections into digital samples; applying a first window in the fast time of the digital samples; performing a first fast Fourier transform (FFT) process on the digital samples to generate a range spectrum; applying a second window in the slow time of the range spectrum; and performing a second FFT process on the range spectrum to generate a range-velocity spectrum. In some aspects of the third embodiment, the power distribution is associated with the second window. In some aspects of the third embodiment, if the second window is applied only after performing the first FFT process and before performing the second FFT process, the power distribution corresponds to the square root of the weighted coefficient value of the second window.

[0014] In some aspects of the third embodiment, the method includes modifying the power distribution based on maintaining the average output power of the transmitted plurality of radar transmit signals to be substantially the same as when the plurality of radar transmit signals are transmitted at a constant power. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present disclosure can be better understood by reference to the accompanying drawings, and the numerous features and advantages of the present disclosure will be apparent to those skilled in the art. Like reference symbols are used in different figures to indicate similar or identical items.

[0016] Figure 1 and 2 illustrate examples of a radar front end and a radar main controller processing unit in a radar system configured to implement transmit power shaping and corresponding signal processing techniques according to various embodiments, respectively.

[0017] Figure 3Illustrates examples of vehicle control systems including radar systems (e.g., Figure 1 and 2 radar systems).

[0018] Figure 4 Illustrates examples of matrices representing digitized samples of radar signals received in fast time and slow time, according to various embodiments.

[0019] Figure 5 Illustrates examples of radar systems that shape the transmit power of radar signals according to a power distribution based on a slow time window applied by a radar signal processor, according to various embodiments.

[0020] Figure 6 Illustrates examples of method flowcharts for transmit power shaping and signal processing techniques, according to various embodiments. DETAILED DESCRIPTION

[0021] Some challenges in designing high-performance radar systems include limiting the power required to transmit robust radar signals and improving the signal quality of received radar signals. For example, radar systems that rely on high transmit power levels may be inappropriate because, in addition to higher power consumption, hardware complexity and hardware cost also increase, while radar systems that are more susceptible to noise or interference may not be able to provide accurate and timely information about the surrounding environment. Additionally, according to conventional methods, reducing the power of the transmitted radar signals typically reduces the signal quality of the received radar signals (e.g., signal-to-noise ratio SNR), while attempting to improve the signal quality of the received radar signals typically requires increasing the transmit power. Figures 1-6 Transmit power shaping and signal processing techniques are provided that improve the signal quality at the receiver without the need to increase the transmit power budget (i.e., the transmit power utilized over a period of time). Alternatively, these techniques can be used to reduce the transmit power budget while maintaining a relatively high signal quality at the receiver.

[0022] For illustration, in some embodiments, a radar system senses its surroundings by transmitting a chirp sequence and receiving reflections of the chirps after the chirps bounce off one or more objects (also referred to as targets) in the surrounding environment. After converting the received reflections into digitized samples, the radar system processes the digitized samples to obtain an estimate of a range distribution including ranges to one or more targets. This range processing step is sometimes referred to as fast-time range processing and involves applying a first window (e.g., multiplying by a first window function) in the fast time of the digitized samples and then applying a first fast Fourier transform (FFT) to the windowed samples in the fast time to produce a series of range distributions. Then, the range distributions produced by the fast-time range processing are processed in a velocity (or Doppler) processing step, which is referred to herein as slow-time velocity (or Doppler) processing. Slow-time velocity processing involves applying a second window (e.g., Gaussian window, Chebyshev window, Hanning and Hamming windows, Blackman window, etc.) in the slow time of the digitized samples. Applying the second window involves multiplying the digitized samples by a second window function, which includes a plurality of weighting coefficients that are zero-valued outside a selected interval in the slow-time domain. Subsequently, a second FFT is applied in the slow time to estimate the phase evolution of different targets over time. The second window equally weights the samples of a single range distribution, and thus the second window can be performed at an individual chirp level (i.e., each chirp in a plurality of chirps in a chirp sequence). The present disclosure takes advantage of this property and moves a portion of the weighting coefficients of the second window (e.g., the square root of the second window function) from the signal processor to the transmitter of the radar system. That is, contrary to the conventional method of applying the entire second window only on the signal processing side before slow-time velocity processing, the techniques described herein divide the second window into two parts. The first of these two parts is applied at the transmitter before transmitting the chirp sequence, while the second of these two parts is applied before slow-time velocity processing (i.e., the second part remains in its original location). Shifting a portion of the second window to the transmitter side modifies the power envelope of the chirp sequence transmitted by the radar system from having a constant power level to having multiple different power levels. Thus, and different from the conventional method of transmitting radar chirp sequences at a constant power level, the techniques described herein transmit radar chirp sequences at different power levels corresponding to a portion of the processing imparted by the weighting coefficients of the second window that are moved from the radar signal processor to the transmitter. Thus, the techniques described herein reduce the transmit power of the chirps corresponding to the samples whose values will be mitigated by the second window during signal processing. In this way, the transmit power shaping and second window techniques described herein change the degree to which noise and signals are affected by the second window applied during signal processing by reducing the transmit signal power of the samples that are more affected by the second window (e.g., minimized or set to zero).Thus, a greater portion of the power budget of the chirp sequence in the transmitted radar signal can be allocated to the chirps associated with the samples occurring during the focusing interval of the second window. If the total transmitted power budget remains constant (i.e., the average transmitted power of the radar chirps is the same), this results in an SNR gain. Alternatively, if the SNR at the receiver remains at the same or a similar level as that which supports fully implementing the power budget of the second window during signal processing of the received signal, this approach reduces the transmitted power budget for transmitting the radar chirps.

[0023] In some embodiments, any element, component, or block shown in the figures is implemented as one of software executed on a processor, hard-wired hardware (e.g., circuitry) that performs the various operations described herein, or a combination thereof. For example, one or more of the described blocks or components (e.g., the block or component associated with shaping the power distribution of the radar signal for transmission, the block or component associated with applying a window to digitized samples prior to FFT processing, the block or component associated with fast-time or slow-time FFT processing, etc.) represent software instructions executed by hardware such as a digital signal processor, an application specific integrated circuit (ASIC), a set of logic gates, a field programmable gate array (FPGA), a programmable logic device (PLD), a hardware accelerator, a parallel processor, or any other type of hard-coded or programmable circuitry. As another example, one or more of the described blocks or components (e.g., the block or component associated with shaping the power distribution of the radar signal for transmission, etc.) represent hardware such as a multi-stage power amplifier.

[0024] Figure 1 and 2 shows an example of a radar system 100 (including Figure 1 a first radar system portion 100-1 and Figure 2 a second radar system portion 100-2) according to various embodiments, the radar system 100 implementing power shaping of the transmitted radar signal based on a second window applied prior to slow-time velocity processing at a radar processor. Figure 1 shows the radar front end 102 of the radar system 100, and Figure 2 shows the radar main controller processing unit (MCPU) 138 of the radar system 100.

[0025] Reference Figure 1, in some embodiments, the radar front end 102 includes a plurality of transmitters 104-1 to 104-N (collectively referred to as transmitters 104). In some embodiments, each transmitter 104 includes a power amplifier (PA) 106 and a radio frequency (RF) conditioning (cond.) component 108. The PA 106 converts a lower power RF signal into a higher power RF signal before transmission. For example, in some embodiments, the PA 106 is configured to convert a lower power RF signal including a plurality of chirps into a higher power RF signal. In some cases, as described herein, the higher power RF signal includes a plurality of different power levels. For example, the PA 106 can be an N-stage PA, configured to output a higher power RF signal at N different levels based on an input voltage control signal, where N is an integer greater than one. In some embodiments, the PA 106 is a three-stage PA, configured to receive a lower power RF signal from the RF Cond 108 and output a higher power RF signal at three different higher power levels. The RF conditioning component 108 includes hardware and / or software for modifying (i.e., conditioning) the signal before providing the signal received from the chirp generator 137 to the PA 106. For example, in some embodiments, the RF conditioning component 108 includes one or more filters that filter the RF signal before the signal power is amplified at the PA 106.

[0026] In some embodiments, the radar front end 102 receives program, control trigger, and reference clock signals 136 for chirp generation at the chirp generator 137 or received signal processing in the receiver 110. For example, the reference clock signal is a local oscillator (LO) signal, and the control trigger is a chirp start trigger signal that is input to the chirp generator 137 to generate radar chirp sequences that are further processed (e.g., by the RF conditioning component 108 and the PA 106) before being transmitted by the transmit antenna 120 of the radar front end 102. The chirp generator 137 includes a phase-locked loop (PLL) that generates a chirp sequence. For example, the PLL in the chirp generator 137 generates an FMCW chirp sequence for transmission by the transmitter 104. In the illustrated embodiment, the transmit signal generation component is the chirp generator 137. In other embodiments, the transmit signal generation component is a pulse generator or a digital radar modulation component. Thus, while the following embodiments describe transmit power shaping and signal processing techniques for chirp-based radar waveforms, in other embodiments, the transmit power shaping and signal processing techniques can also be applied to pulse-based and digitally modulated radar waveforms.

[0027] The radar front end 102 also includes a transmit antenna 120. In some embodiments, each transmitter 104 is configured with its own transmit antenna 120 (i.e., transmitter 104-1 with transmit antenna 120-1, transmitter 104-2 with transmit antenna 120-2, transmitter 104-3 with transmit antenna 120-3, and transmitter 104-N with transmit antenna 120-N). The transmitter 104 sends a transmitted signal 124 to one or more targets 126 (one is shown for clarity). The transmitted signal is reflected from the target 126, and the signal 128 reflected by the target (collectively referred to as the target radar signal) is directed back to the radar system 100. The signal 128 reflected by the target is received by the receive antennas 130-1 to 130-M. In some embodiments, each receiver 110 is configured with its own receive antenna 130 (i.e., receiver 110-1 with receive antenna 130-1, receiver 110-2 with receive antenna 130-2, receiver 110-3 with receive antenna 130-3, receiver 110-M with receive antenna 130-M). In addition to receiving the target reflected signal 128, the receiver 110 also receives other unwanted signals. For example, an interference source 132 (in this example, a radar signal from another vehicle) transmits interference 134, which is also received by the receiver 110.

[0028] In some embodiments, the radar front end 102 also includes a plurality of receivers 110-1 to 110-M (collectively referred to as receivers 110). One or more of the receivers 110 include a low noise amplifier (LNA) 112, a de-ramp mixer 114, a high pass filter (HPF) 116, a power amplifier 118, a low pass filter (LPF) 120, and an analog-to-digital converter (ADC) 122, which digitizes the received radar signal before providing the received radar signal to a radar signal processor to estimate the distance and velocity of the target 126.

[0029] Now refer to Figure 2, in some embodiments, the radar system 100 includes a radar master controller processing unit (MCPU) 138. In some embodiments, the radar MCPU 138 includes a radar controller 140 and a receiver (RX) processor 142. The radar controller 140 provides the programs, control triggers, and reference clock signal 136 as described above. The receiver processor 140 receives digitized signals from the radar front end 102, such as digitized signals from the ADC 122 of the receiver 110. In some embodiments, the RX processor 140 includes an interference cancellation component 144, and the interference cancellation component 144 provides interference-suppressed ADC samples 146. The fast-time (range) spectrum component 148 receives and processes the interference-suppressed ADC samples 146. For example, the fast-time spectrum component 148 applies a first window in the fast time to the interference-suppressed ADC samples 146, and then applies an FFT within the fast time of the windowed samples. In this way, the fast-time spectrum component 148 provides range chirp data 150 indicating the chirp reflections received at the receiving antenna 130. In some embodiments, the range chirp data 150 is cubed with an x-axis and a y-axis consisting of fast-time data and a z-axis representing the data of each of the receiving antennas 130. The range chirp data 150 is received and processed by the slow-time (velocity or Doppler) spectrum component 152. For example, the slow-time spectrum component 152 applies a second window in the slow time to the range chirp data 150, and then applies an FFT within the slow time of the windowed samples. In this way, the slow-time spectrum component 152 provides range-Doppler data 154, and the range-Doppler data 154 is cubed with an x-axis and a y-axis consisting of slow-time data and a z-axis representing the data of each of the receiving antennas 130. In some embodiments, the range-Doppler data 154 is received and processed by a constant false alarm rate (CFAR) detection component 156. The detection component 156 provides detected range and Doppler cell data 158. The multiple-input multiple-output (MIMO) array measurement construction component 160 receives and processes the detected range and Doppler cell data 158. The MIMO array measurement construction component 160 provides an array measurement vector 162. The array measurement vector is received and processed by the target angle of arrival (AoA) estimation component 164. The target AoA estimation component 164 provides target information 166 attributed to the target 126 detected by the radar system 100 to other components via the data interface 170. For example, other components include software modules executed by a processor to implement an advanced driver assistance system (ADAS) or an autonomous driving (AD) perception and vehicle control system.

[0030] In some embodiments, a radar system 100 including a radar front end 102 and a radar MCPU 138 is configured to perform the transmit RF signal power shaping and signal processing techniques described herein. For example, one or more of the transmitters 110 are configured to generate a plurality of radar chirps according to a power distribution having different transmit power levels. In some embodiments, the power distribution is determined based on a window applied in slow time prior to (e.g., by the slow time spectral component 152) slow time FFT processing. Thus, in some embodiments, the transmitter 110 is equipped with a multi-stage power amplifier, such as PA106, that receives a lower power RF signal at its input and outputs a higher power RF signal at a plurality of discrete power levels for transmission as a radar signal 124. The radar front end 102 also receives the reflected radar signal 128 after the reflected radar signal 128 bounces off the target 126, and digitizes the received radar signal (the received radar signal including the reflection of the transmitted radar chirp) for further processing at the radar MCPU 138. The radar MCPU 138 includes software and / or hardware for performing signal processing on the digitized signals received from the radar front end 102. For example, the slow time spectral component 152 is configured to apply a portion of a second window in the slow time of the digitized samples compared to a second window applied in a conventional radar signal processing method. In some cases, the slow time spectral component 152 applies half of the second window in the slow time of the digitized samples, with the effect of applying the other half of the second window at the transmitter 110 by modifying the power level of the chirp prior to transmission.

[0031] Figure 3 An example of a vehicle control system 300 according to some embodiments is shown. The vehicle control system 300 is implemented, for example, in an automobile and can be used to assist driver assistance or autonomous driving functions. As shown, the vehicle control system 300 includes a radar system that includes radar front ends 306, 308 and a radar MCPU 304. In some embodiments, the radar front ends 306, 308 correspond to Figure 1 the radar front end 102 in Figure 2 and the radar MCPU 304 corresponds to

[0032] the radar MCPU 138 in Figure 3Two radar front ends 306, 308 are shown, but this number is for clarity and can be extended to a larger number. In some embodiments, the radar front ends 306, 308 are located at various positions around the vehicle that houses the vehicle control system 300. For example, one radar front end 306 is located at the front end of the vehicle, while another radar front end 308 is located at the rear end of the vehicle. In some embodiments, the radar front end 306 includes a plurality of antennas 316, 318. For example, the plurality of antennas 316 are transmit antennas, while the plurality of antennas 318 are receive antennas. Similarly, in some embodiments for the radar front end 308, the plurality of antennas 326 are transmit antennas, while the plurality of antennas 328 are receive antennas. In some embodiments, the plurality of antennas associated with each of the radar front ends 306, 308 support a MIMO radar configuration. Although two antennas are shown for each of the plurality of antennas 316, 318, 326, 328, this number is for clarity and in some embodiments can be extended to a larger number (e.g., three, four, or more antennas).

[0033] In some embodiments, the radar MCPU 304 is implemented as a microcontroller unit (MCU) or other processing unit configured to perform radar signal processing tasks, which are calculations of, for example but not limited to, object identification, object distance, object speed, and object direction (collectively referred to as "radar information"). In some embodiments, the radar MCPU 304 is additionally configured to generate control signals based on the radar information. The radar MCPU 304 is configured, for example, to generate calibration signals, receive data signals, receive sensor signals, generate spectral shaping signals (e.g., signals associated with the FCMW radar technology described herein), and / or state machine signals for a radio frequency (RF) circuit enable sequence. Additionally, in some embodiments, the radar MCPU 304 is configured to program the radar front ends 306, 308 to operate in a coordinated manner by transmitting MIMO waveforms to construct a virtual aperture from the combination of distributed apertures formed by the plurality of transmit and receive antennas shown Figure 3 to form a combined virtual aperture.

[0034] In some embodiments, radar front ends 306, 308 include radar front-end chip circuits that are coupled to respective plural antennas to transmit radar signals (e.g., in the form of a radar chirp sequence), receive reflected radar signals, and digitize these received radar signals for forwarding via interface 320 to radar MCPU 304. In some embodiments, radar MCPU 304 performs radar processing tasks based on the digitized radar signals received from radar front ends 306, 308 to provide radar information to ECU 302. ECU 302 uses this radar information to control one or more actuators 310, such as a steering actuator, a braking actuator, or a throttle actuator, to assist driver assistance or autonomous driving functions. In some embodiments, ECU 302 displays the radar information or associated information via a user interface 312 (e.g., a screen display, a speaker, or a light) (e.g., on a side mirror or a dashboard) to alert the driver of an object nearby.

[0035] Figure 4 An example of a matrix 400 showing digitized samples of radar signals received in fast time 402 and slow time 404 is shown. For example, matrix 400 represents ADC samples 146 for interference suppression in the fast-time spectral component 148 of an RX processor 142 that is input to Figure 2 and includes samples 415 (one sample 415 is labeled for clarity) having dimensions in both fast time 402 and slow time 404.

[0036] A first FFT component in the RX processor, such as the fast-time spectral component 148 of RX processor 142, processes the digitized samples represented by matrix 400 in fast time 402 by applying a first window 412 to each column of matrix 400 and then performing an FFT within the fast time 402 of the windowed samples. A second FFT component in the RX processor, such as the slow-time spectral component 152 of RX processor 142, processes the digitized samples represented by matrix 400 in slow time by applying a second window 414 to each row of matrix 400 and then performing an FFT within the slow time 404 of the windowed samples. In this way, matrix 400 is processed by the FFT processing components to output a corresponding range-Doppler matrix (also referred to as a range-velocity matrix) that is used to determine the range and velocity of detected targets in the environment surrounding the radar system.

[0037] According to some embodiments, each of the windows 412, 414 is implemented as a function that is zero-valued (or a mitigation value) outside of a selected interval. In some cases, the window includes a series of weighting coefficients that are symmetric about the selected interval therein. For example, the window can be represented as a bell curve that approaches a maximum value in the middle and tapers down to lower (e.g., zero) values away from the middle. Mathematically, when a signal waveform or data sequence is "windowed", this means that the signal waveform or data sequence is multiplied by a window having weighting coefficient values, which weights the portion of the signal waveform or data sequence that falls within the selected interval of the window (e.g., a row or column of matrix 400), and eliminates the signal waveform or data sequence values by zeroing or minimizing the signal waveform or data sequence values that fall outside of the "window". Since the second window 414 is applied within the slow time 404 of the matrix 400, it equally weights the samples 415 of a single range distribution, which means that the second window 414 can be performed at a separate chirp level. The techniques described herein utilize this aspect to move a portion of the second window 414 to the transmit side by modifying the transmit power of the chirps individually transmitted among multiple chirps. That is, prior to slow time FFT processing, a portion of the effect of the second window 414 is implemented on the transmit side by reducing the transmit power of the chirps that fall outside of the chirp range that is the focus of the second window 414. The overall effect in the output of the second window 414 applied prior to slow time FFT processing remains the same, but by performing the techniques described herein, the transmit power of the chirps corresponding to the window samples with lower magnitudes is reduced. If the total transmit power budget for transmitting multiple chirps in a radar chirp sequence remains the same, this results in an SNR gain (e.g., within a range of 1.5 dB to 2 dB, e.g., ~1.8 dB). Alternatively, the transmit power budget can be reduced while maintaining a similar signal quality (e.g., SNR) of the received radar signal.

[0038] Figure 5 FIG. shows a radar system 500 configured to shape the transmit power of radar signals according to a power distribution of a slow time window applied by a radar signal processor prior to slow time processing. In some embodiments, the radar system 500 corresponds to Figure 1 and 2 radar system 100 of Figure 3 radar system.

[0039] The transmit chain of radar system 500 includes a phase-locked loop (PLL) circuit 502 that is configured to generate a radar transmit signal including a sequence of radar transmit signals that includes, for example, radar chirps 532 (one chirp is labeled for clarity); and a TX front end 510 coupled to one or more transmit antennas 511, the TX front end 510 transmitting the radar signal into the surrounding environment. For example, in some embodiments, the PLL circuit 502 generates a chirp signal, such as a frequency-modulated continuous wave (FMCW) signal having a plurality of frequency-modulated chirps. The chirp sequence includes a plurality of chirps 532 that increase in frequency f (i.e., ramp up) over the duration t of each corresponding chirp, as shown in block 512. Additionally, at the output of the PLL 502 shown in block 512, a sequence of chirps 532 is generated with a constant power profile (P 1 ) 542. Different from conventional systems that amplify the constant power of the chirp sequence to a higher constant power before transmission, the radar system 500 includes an additional transmit signal component 504 that modifies the power profile of the chirp sequence in the radar signal to be transmitted by the TX front end 510. In the illustrated embodiment, a radar transmit signal sequence including a plurality of radar transmit signals is described as a radar chirp sequence including a plurality of radar chirps. In other embodiments, the radar transmit signal sequence is a pulse-based radar sequence or a digitally modulated radar sequence that includes a plurality of radar pulses or a plurality of digitally modulated radar symbols, respectively.

[0040] The additional transmit signal component 504 includes hardware, software, or a combination thereof, and employs the constant power profile P 1 512 of the sequence of chirps 532 generated by the PLL circuit 502 and converts the power profile to a modified power profile including a plurality of different power levels. In some embodiments, this modified power profile is based on a portion of a second window that is typically applied during slow-time signal processing of the received radar signal at the transmitter prior to signal transmission. That is, in contrast to conventional systems that apply the second window only in slow time during signal processing of the received radar signal, the radar system 500 applies a portion of this window at the additional transmit signal component 504 at the power shaping component 506 prior to transmitting the radar signal. For example, half of the weighted coefficient value typically applied by the second window is applied at the power shaping component 506, and the other half of the weighted coefficient value is applied (i.e., retained) at a signal processing component in the receive chain, such as at the modified window 2 528. Accordingly, the power shaping component 506 is configured to adjust the constant power profile P 1 542 generated by the PLL 502 to a modified power profile P 2 544 at its output 516. Thus, the power shaping component 506 outputs the modified power profile P 2544 outputs a sequence of chirps 534. In some embodiments, the modified power distribution P 2 544 follows the square root of the weighting factor of a second window applied over slow time.

[0041] In some embodiments, the additional transmit signal component 504 includes a normalization component 508 for increasing the power level of the modified power distribution P 2 544. For example, the normalization component 508 multiplies the modified power distribution P 2 544 by a normalization factor to increase the modified power distribution P 2 544 to an output based on one of two options shown in outputs 518-1, 518-2. In the first option 518-1, the normalization component 508 multiplies the power of the power distribution P 2 544 by a first normalization factor to output a power distribution P 3A 546-1. The power distribution P 3A 546-1 has the same average output power as the constant power distribution P 1 542. That is, the area under the power distribution P 3A 546-1 and the area under the constant power distribution P 1 542 are the same (or substantially the same). In this way, the total transmit power budget for transmitting radar signals is maintained, but the SNR in the received signal increases due to variations in the degree to which noise and the signal experience the second window (i.e., the window applied over slow time) effect. In the second option 518-2, the normalization component 508 multiplies the power of the power distribution P 2 544 by a second normalization factor to output a power distribution P 3B 546-2. The power distribution P 3B 546-2 corresponds to a power distribution that achieves the same SNR output as achieved by transmitting a radar chirp sequence at a constant high power level according to conventional techniques, but with a lower total transmit power budget. Thus, the techniques described herein are capable of achieving a higher SNR for transmitting a radar chirp sequence with the same transmit power budget (as shown in option 1 518-1), or achieving the same SNR with a lower transmit power budget for transmitting a radar chirp sequence (as shown in option 2 518-2).

[0042] The radar system 500 also includes a receive chain that includes an RX front end 520, an ADC 522, a window 1 524, a range FFT 526, a modified window 2 528, and a velocity FFT 530. The RX front end 520 includes Figure 1The receiver 110 up to the ADC 122 of these components. In some embodiments, the RX front end 520 includes, for example, a low noise amplifier such as the LNA 112, a mixer such as the mixer 114 that receives the signal 512 from the PLL circuit 502, a high pass filter such as the HPF 116, a power amplifier such as the PA 118, and a low pass filter such as the LPF 120. In some embodiments, the ADC 522 corresponds to Figure 1 the ADC 122, and outputs digitized samples of the radar signal received by the RX front end 520. The receive chain also includes window 1 524 and range FFT 526 as well as modified window 2 528 and velocity FFT 530. In some embodiments, for example, at Figure 2 the fast time (range) spectral component 148 shown, window 1 524 and range FFT 526 are implemented, and for example, at Figure 2 the slow time (Doppler) spectral component 152 shown, modified window 2 528 and velocity FFT 530 are implemented.

[0043] According to the techniques described herein, a second window that is typically only applied in the receive chain (i.e., a window applied to the slow time of the digitized samples) is divided into two parts. The first of these parts is moved to the power shaping component 506 to modify the power distribution of the chirp sequence to be transmitted by the radar system 500, while the second of these parts remains in its position at the modified window 2 528 prior to being processed by the velocity FFT 530 (also referred to as slow time velocity processing, slow time Doppler processing, second FFT processing, etc.). For example, in some embodiments, the part of the second window that is moved to the power shaping component 506 is the square root of the values of the second window, while the remaining square root of the values of the second window remains at the modified window 2 528.

[0044] In some embodiments, the second window is defined according to the requirements of the radar system. For example, the second window can be defined according to considerations attributable to the use of the radar system in ADAS or AD vehicle applications. Thus, in some aspects, the cascading of the second window between the transmitter and the signal processing at the RX processor (i.e., dividing the second window between the Figure 5 power shaping component 506 and the modified window 2 528) should be the same as if the second window were fully applied during signal processing at the RX processor. In some aspects, this includes dividing the second window equally between the transmitter (e.g., at the Figure 5 power shaping component 506) and the signal processor (e.g., at the Figure 5 modified window 2 528). For example, for illustrative purposes, referring to Figure 5, since the second window is applied to the signal by multiplying the signal by the weighting coefficient of the second window, this equal division causes the power shaping component 506 to apply the square root of the weighting coefficient of the second window to its input to produce a modified power distribution at its output, and the modified window 2 528 applies the square root of the weighting coefficient of the second window to its corresponding input to produce windowed samples for velocity FFT processing. At the same average transmit power (i.e., once the normalization component 508 applies the first normalization factor according to the option at output 518-1), in some embodiments, this results in an SNR gain of ~1.8 dB. Alternatively, at the same SNR on the receiver side (i.e., once the normalization component 508 applies the second normalization factor according to the option at output 518-2), in some embodiments, this results in a transmit power reduction of ~1.8 dB.

[0045] Figure 6 An example of a flowchart 600 illustrating the transmit power shaping and signal processing techniques according to some embodiments is shown. Flowchart 600 includes a first part 610 implemented by the transmit components (e.g., Figure 5 the power shaping component 506, the normalization component 508, and the TX front-end component 510) of the radar device, and a second part 620 implemented by the receive components (e.g., Figure 5 the RX front-end 520 and the ADC 522) and the signal processing components (e.g., Figure 5 window 1 524, range FFT 526, modified window 2 528, and velocity FFT 530) of the radar device.

[0046] At 602, the transmitter modifies the power distribution of the radar transmit signal sequence before transmission. For example, referring to Figure 5 , the radar chirp sequence is generated by the PLL circuit 512 with a constant power distribution P 1 542. The power shaping component 506 modifies the constant power distribution P 1 542 to a modified power distribution P 2 544. In some embodiments, the modified power distribution P 2 544 is associated with the window in the slow time of the digitized samples of the received reflections that the signal processor applies to the multiple radar chirps. Additionally, in some embodiments, the radar chirp sequence with the modified power distribution P 2 544 is further processed by the normalization component 508 to increase the power level in the power distribution.

[0047] At 604, the transmitter transmits a radar signal including a sequence of radar transmission signals based on a modified power distribution. For example, the transmitter includes a multi-stage power amplifier, such as PA106, that transmits the sequence of radar transmission signals at multiple discrete power levels based on the modified power distribution. For example, the multi-stage power amplifier includes 2 to 10 different power gain settings that transmit multiple chirps in a radar chirp sequence at corresponding numbers of different power levels.

[0048] At 606, the receiver digitizes the received reflections of the radar transmission signal sequence in the transmitted radar signal. For example, this includes an ADC (such as Figure 1 ADC 122 or Figure 5 ADC 522) that converts the received signal from an analog signal to a plurality of discrete digitized samples.

[0049] At 608, after applying a first window and a first FFT to the digitized samples to generate a range distribution of the received reflections, a signal processor (e.g., Figure 2 RX processor 142) applies a modified window in slow time (e.g., via Figure 5 modified window 2 528). In some embodiments, the modified window in slow time is associated with the modified power distribution applied by the transmitter in step 602. In some embodiments, when a multi-stage power amplifier is used in the transmitter, the modified window in slow time matches the number of power gain settings of the multi-stage power amplifier. After applying the modified window in slow time, the signal processor performs slow-time FFT processing to generate a range-velocity distribution of the received reflections.

[0050] In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system that executes software. The software includes one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer-readable storage medium. The software may include instructions and certain data that, when executed by one or more processors, cause the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer-readable storage medium may include, for example, a disk or optical disk storage device, a solid-state storage device such as a flash memory, a cache memory, a random access memory (RAM), or other one or more non-volatile memory devices, and the like. The executable instructions stored on the non-transitory computer-readable storage medium may be in the form of source code, assembly language code, object code, or in other instruction formats that can be interpreted or otherwise executed by one or more processors.

[0051] A computer-readable storage medium can include any storage medium or combination of storage media that can be accessed by a computer system during use to provide instructions and / or data to the computer system. Such storage media can include, but are not limited to, optical media (e.g., compact disc (CD), digital versatile disc (DVD), Blu-ray disc), magnetic media (e.g., floppy disk, magnetic tape, or magnetic hard disk drive), volatile memory (e.g., random access memory (RAM) or cache memory), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer-readable storage medium can be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., magnetic hard disk drive), removably attached to the computing system (e.g., optical disc or universal serial bus (USB)-based flash memory), or coupled to the computer system via a wired or wireless network (e.g., network-attached storage device (NAS)).

[0052] It should be noted that not all of the activities or elements described above in the general description are required, that a particular activity or device may not be part of what is needed, and that one or more additional activities or elements may be performed or included in addition to those described. Further, the order of the listed activities is not necessarily the order in which they are performed. Additionally, concepts have been described with reference to specific embodiments. However, those skilled in the art will understand that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0053] The benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, these benefits, advantages, solutions to problems, and any features that may cause any benefit, advantage, or solution to occur or become more pronounced should not be construed as critical, required, or essential features of any or all of the claims. Moreover, the specific embodiments disclosed above are merely illustrative, as the disclosed subject matter can be modified and practiced in different but equivalent ways that will be apparent to those skilled in the art benefiting from the teachings herein. Except as described in the appended claims, no intention is made to limit the details of the construction or design shown herein. Thus, it is apparent that the specific embodiments disclosed above can be varied or modified, and all such variations are considered to be within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the appended claims.

Claims

1. A radar front end, characterized in that: include: a transmit signal generating circuit configured to generate a radar transmit signal sequence including a plurality of radar transmit signals; a power shaping component, the power shaping component being configured to receive the plurality of radar transmit signals of the radar transmit signal sequence and output the plurality of radar transmit signals having a plurality of different power levels; as well as A transmitter is configured to transmit the plurality of radar transmit signals of the radar transmit signal sequence based on the plurality of different power levels.

2. The radar front end according to claim 1, characterized in that: The plurality of different power levels correspond to power distributions associated with windows applied to digitized samples of received reflections of a transmitted plurality of radar transmit signals at a radar processor coupled to the radar front end.

3. The radar front end according to claim 1, characterized in that: The transmitter includes a power amplifier for receiving the output from the power shaping component and converting the output to a signal including the plurality of radar transmit signals at a plurality of different amplified power levels prior to transmission.

4. The radar front end according to claim 1, characterized in that: The transmit signal generation circuit generates the radar transmit signal sequence including the plurality of radar transmit signals with an initial power profile including a constant power level, and the power shaping component modifies the initial power profile to the plurality of different power levels.

5. The radar front end according to claim 4, characterized in that: The transmitter includes a normalization component that further modifies the output of the power shaping component so that a total transmit power budget for transmitting the plurality of radar transmit signals is substantially the same as if the plurality of radar transmit signals were transmitted at a constant power level.

6. A radar device, characterized in that: include: A radar front end, the radar front end comprising: a transmit signal generating circuit configured to generate a radar transmit signal sequence including a plurality of radar transmit signals; a power shaping component configured to receive the plurality of radar transmit signals of the radar transmit signal sequence and output the plurality of radar transmit signals having a plurality of different power levels; and a transmitter for transmitting the plurality of radar transmit signals based on the plurality of different power levels, wherein the plurality of different power levels are based on a power distribution associated with a window applied to digitized samples of reflections of the transmitted plurality of radar transmit signals; and A radar processor is provided for applying the window in a slow time of the digitized samples of the reflections before performing a fast Fourier transform (FFT) on the digitized samples of the reflections.

7. The radar device according to claim 6, characterized in that The transmitter includes a power amplifier for receiving the output from the power shaping component and converting the output to a signal including the plurality of radar transmit signals at a plurality of different amplified power levels prior to transmission.

8. The radar device according to claim 6, characterized in that The transmit signal generation circuit generates the radar transmit signal sequence including the plurality of radar transmit signals with an initial power profile including a constant power level, and the power shaping component modifies the initial power profile to the plurality of different power levels based on the power profile.

9. A method, characterized in that The method comprises: generating multiple radar transmit signals at a constant power level; modifying the constant power level of the plurality of radar transmit signals to a plurality of power levels according to a power profile; and The plurality of radar transmit signals are transmitted based on the plurality of power levels.

10. The method according to claim 9, characterized in that Also includes: receiving reflections of the plurality of radar transmit signals; converting the received reflections into digitized samples; Applying a first window in a fast time of said digitized samples; Performing a first fast Fourier transform (FFT) process on the digitized samples to generate a distance spectrum; applying a second window in the slow time of the range spectrum; and A second FFT process is performed on the range spectrum to generate a range-velocity spectrum.

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