Generate high-frequency FMCW radar from low-frequency FMCW radar

Abstract

Disclosed are a vehicle, a radar system for the vehicle, and a method for detecting parameters of an object. The radar system includes a base radar and a frequency converter. The base radar generates a first frequency source signal within a first frequency range and receives a first frequency reflected signal within the first frequency range. The base radar is configured to determine parameters of the object from the first frequency reflected signal. The frequency converter is configured to convert the first frequency source signal into a second frequency source signal within a second frequency range and convert the second frequency reflected signal within the second frequency range into the first frequency reflected signal.

Description

Technical Field

[0001] The present disclosure relates to a system and method for radar detection, and more particularly, to a system and method for converting radar signals between a low frequency range and a high frequency range to perform radar detection with increased resolution. Background Art

[0002] Radar systems can be used in vehicles to determine the position and velocity of various objects around the vehicle. Radar systems typically emit a radio frequency (RF) source signal, receive reflections of the source signal from objects, and determine parameters of the objects, such as distance, velocity, and angular position, by comparing the source signal and the reflected signal. The resolution of a radar system can be improved by increasing the operating frequency of the radar system's source signal. However, for vehicles with existing radar systems, increasing the resolution requires replacing the existing radar system with a radar system having a higher operating frequency, which can be expensive and labor-intensive. Therefore, it is desirable to provide a method for increasing the operating frequency of an existing radar system. Summary of the Invention

[0003] In one exemplary embodiment, a method for detecting parameters of an object is disclosed. A first frequency source signal within a first frequency range is obtained. A second frequency source signal within a second frequency range is generated from the first frequency source signal. A first frequency reflection signal within the first frequency range is generated from a second frequency reflection signal within the second frequency range, wherein the second frequency reflection signal indicates reflection of the second frequency source signal from the object. The parameter of the object is determined from the first frequency reflection signal.

[0004] In addition to one or more features described herein, the method further includes generating a reference signal within a third frequency range from the first frequency source signal, and combining the reference signal with the second frequency reflection signal to generate the first frequency reflection signal. The first frequency reflection signal is a difference signal obtained by multiplying the reference signal and the second frequency reflection signal. The second frequency range is greater than the first frequency range, and the third frequency range is between the first frequency range and the second frequency range. The method further includes generating a plurality of harmonic signals from the first frequency source signal, selecting a harmonic signal within the second frequency range from the plurality of harmonic signals as the second frequency source signal, and selecting another harmonic signal within the third frequency range from the plurality of harmonic signals as the reference signal. The first frequency source signal is a linear frequency modulation (LFM) signal within a first frequency range defined by a lower frequency limit B1 and an upper frequency limit B2, the second frequency source signal is an LFM signal within a second frequency range defined by N*B1 and N*B2, and the reference signal is an LFM signal within a third frequency range defined by (N-1)*B1 and (N-1)*B2. The parameter of the object is at least one of the range of the object, the relative radial velocity of the object, the azimuthal position of the object, and the elevation angle of the object.

[0005] In another exemplary embodiment, a radar system for a vehicle is disclosed. The radar system includes a base radar and a frequency converter. The base radar generates a first frequency source signal within a first frequency range and receives a first frequency reflection signal within the first frequency range. The base radar is configured to determine parameters of an object from the first frequency reflection signal. The frequency converter is configured to convert the first frequency source signal into a second frequency source signal within a second frequency range and convert the second frequency reflection signal within the second frequency range into the first frequency reflection signal.

[0006] In addition to one or more features described herein, the frequency converter is further configured to generate a reference signal within a third frequency range from the first frequency source signal, and combine the reference signal with the second frequency reflection signal to generate the first frequency reflection signal. The first frequency reflection signal is a difference signal obtained by multiplying the reference signal and the second frequency reflection signal. The second frequency range is greater than the first frequency range, and the third frequency range is between the first frequency range and the second frequency range. The frequency converter also includes: an amplifier circuit configured to generate a plurality of harmonic signals from the first frequency source signal; a filter circuit configured to apply a first filter to the plurality of harmonic signals to select the Nth harmonic signal within the second frequency range as the second frequency source signal; and a reference signal circuit configured to apply a second filter to the plurality of harmonic signals to select the (N-1)th harmonic signal within the third frequency range as the reference signal. The first frequency source signal is a linear frequency modulation (LFM) signal within a first frequency range defined by a lower frequency limit B1 and an upper frequency limit B2, the second frequency source signal is an LFM signal within a second frequency range defined by N*B1 and N*B2, and the reference signal is an LFM signal within a third frequency range defined by (N-1)*B1 and (N-1)*B2. The object parameter is at least one of the range of the object, the relative radial velocity of the object, the azimuthal position of the object, and the elevation angle of the object.

[0007] In another exemplary embodiment, a vehicle is disclosed. The vehicle includes a base radar and a frequency converter. The base radar generates a first frequency source signal within a first frequency range and receives a first frequency reflected signal within the first frequency range. The base radar is configured to determine parameters of an object from the first frequency reflected signal. The frequency converter is configured to convert the first frequency source signal into a second frequency source signal within a second frequency range and convert the second frequency reflected signal within the second frequency range into the first frequency reflected signal.

[0008] In addition to one or more features described herein, the frequency converter is further configured to generate a reference signal within a third frequency range from the first frequency source signal, and combine the reference signal with the second frequency reflection signal to generate the first frequency reflection signal. The first frequency reflection signal is a difference signal obtained by multiplying the reference signal and the second frequency reflection signal. The second frequency range is greater than the first frequency range, and the third frequency range is between the first frequency range and the second frequency range. The frequency converter also includes: an amplifier circuit configured to generate a plurality of harmonic signals from the first frequency source signal; a filter circuit configured to apply a first filter to the plurality of harmonic signals to select the Nth harmonic signal within the second frequency range as the second frequency source signal; and a reference signal circuit configured to apply a second filter to the plurality of harmonic signals to select the (N-1)th harmonic within the third frequency range as the reference signal. The first frequency source signal is a linear frequency modulation (LFM) signal within a first frequency range defined by a lower limit frequency B1 and an upper limit frequency B2, the second frequency source signal is an LFM signal within a second frequency range defined by N*B1 and N*B2, and the reference signal is an LFM signal in a third frequency range defined by (N-1)*B1 and (N-1)*B2.

[0009] The above features and advantages and other features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above features and advantages and other features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0011] Figure 1 An autonomous vehicle in one embodiment is shown;

[0012] Figure 2 A high frequency radar system in one embodiment is schematically shown;

[0013] Figure 3 A high frequency radar system in a selected embodiment is shown;

[0014] Figure 4 a graph showing a signal response in the time domain obtained using the method disclosed herein for determining a target at a selected distance of forty meters; and

[0015] Figure 5 Shown Figure 4 Frequency distribution diagram of the signal response in frequency space. DETAILED DESCRIPTION

[0016] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0017] According to an exemplary embodiment, Figure 1 An autonomous vehicle 10 is shown. In an exemplary embodiment, autonomous vehicle 10 is a so-called Level 4 or Level 5 automation system. A Level 4 system represents "high automation" and refers to the autonomous driving system's specific driving mode performance of all aspects of the dynamic driving task, even if the human driver does not appropriately respond to intervention requests. A Level 5 system represents "full automation" and refers to the autonomous driving system's full-time performance of all aspects of the dynamic driving task under all road and environmental conditions that a human driver can manage. It should be understood that the systems and methods disclosed herein can also be used with autonomous vehicles operating at any of Levels 1 through 5.

[0018] Autonomous vehicle 10 typically includes at least a navigation system 20, a propulsion system 22, a transmission system 24, a steering system 26, a braking system 28, a sensor system 30, an actuator system 32, and a controller 34. Navigation system 20 determines a road-level route plan for autonomous vehicle 10's automated driving. Propulsion system 22 provides power for generating propulsion for autonomous vehicle 10 and, in various embodiments, may include an internal combustion engine, an electric motor such as a traction motor, and / or a fuel cell propulsion system. Transmission system 24 is configured to transfer power from propulsion system 22 to two or more wheels 16 of autonomous vehicle 10 according to a selectable speed ratio. Steering system 26 influences the position of two or more wheels 16. Although described as including a steering wheel 27 for illustrative purposes, in some embodiments contemplated within the scope of the present disclosure, steering system 26 may not include a steering wheel 27. Braking system 28 is configured to provide braking torque to two or more wheels 16.

[0019] Sensor system 30 includes a radar system 40 that senses objects in the environment outside of autonomous vehicle 10 and determines various parameters of the objects that help determine the position and relative velocity of various remote vehicles in the autonomous vehicle's environment. These parameters can be provided to controller 34. In operation, radar system 40 emits a radio frequency (RF) source signal 48, which is reflected at autonomous vehicle 10 by one or more objects 50 in the radar system's field of view as one or more return signals or reflection signals 52, which are received at radar system 40. The one or more reflection signals 52 can be used to determine various parameters of the one or more objects 50, such as the range of the object, the object's Doppler frequency or relative radial velocity, azimuth, elevation, etc. Sensor system 30 may include additional sensors for identifying road features, such as digital cameras, lidar, etc.

[0020] Controller 34 establishes a trajectory for autonomous vehicle 10 based on the output of sensor system 30. Controller 34 may provide the trajectory to actuator system 32 to control propulsion system 22, drivetrain 24, steering system 26, and / or braking system 28 to navigate autonomous vehicle 10 relative to one or more objects 50 based on the determined parameters.

[0021] Controller 34 includes a processor 36 and a computer-readable storage device or storage medium 38. The computer-readable storage medium includes a program or instruction 39 that, when executed by processor 36, operates autonomous vehicle 10 based on the output of sensor system 30. Storage medium 38 may also include a program or instruction 39 that, when executed by processor 36, determines parameters of one or more objects 50 to allow autonomous vehicle 10 to navigate relative to the one or more objects 50.

[0022] Figure 2 A high-frequency radar system 200 in one embodiment is schematically illustrated. High-frequency radar system 200 includes a base radar system 202 operating in a first frequency range (i.e., a low-frequency range), a frequency converter 204, a transmitter 206, and a receiver 208. Base radar system 202 may be an existing radar system of autonomous vehicle 10, and transmitter 206 and receiver 208 may be existing antennas of the vehicle. Transmitter 206 may include multiple transmitters, and receiver 208 may include multiple receivers. Frequency converter 204 may be introduced between base radar system 202, transmitter 206, and receiver 208 to convert signals back and forth between the first frequency range and the second frequency range (i.e., a high-frequency range) of base radar system 202.

[0023] Basic radar system 202 generates a first frequency source signal S1 within a first frequency range, receives a first frequency reflection signal R1 within the first frequency range, and determines parameters of one or more objects 50 based on the first frequency source signal S1 and the first frequency reflection signal R1. The first frequency range is bounded by a lower frequency limit B1 and an upper frequency limit B2, as shown in first graph 230 and second graph 232. First frequency source signal S1 is a frequency modulated continuous wave signal (FMCW signal), also known as a chirp signal, whose frequency increases linearly over time, starting from lower frequency limit B1 and ending at upper frequency limit B2. First frequency reflection signal R1 is also an FMCW signal that falls between lower frequency limit B1 and upper frequency limit B2. Generally speaking, in various embodiments, multiple chirp signals can be transmitted in a sequence extending over a period of time.

[0024] Frequency converter 204 converts first frequency source signal S1 into second frequency source signal S2 within a second frequency range, which is a higher frequency range than the first frequency range. Second frequency source signal S2 is sent to transmitter 206, where it is transmitted into the environment. Source frequency source signal S2 is reflected by one or more objects 50 to generate a second frequency reflected signal R2 within a second frequency range. Receiver 208 receives second frequency reflected signal R2. Frequency converter 204 converts second frequency reflected signal R2 from the second frequency range to the first frequency range to obtain first frequency reflected signal R1. First frequency reflected signal R1 is received at basic radar system 202 for processing and determining parameters of one or more objects 50.

[0025] Frequency converter 204 includes an up-conversion channel 210, a down-conversion channel 212, and a reference signal circuit 214. Up-conversion channel 210 includes an amplifier circuit 216 and an up-conversion filter circuit 218. Amplifier circuit 216 is a nonlinear radio frequency (RF) amplifier, which can be an RF amplifier operating in a nonlinear or saturation range. In one embodiment, the nonlinear RF amplifier is a diode. Amplifier circuit 216 generates a plurality of harmonic signals from the first frequency source signal S1. The frequencies of the harmonic signals are integer multiples of the fundamental frequency (i.e., the frequency of the first frequency source signal S1).

[0026] The up-conversion filter circuit 218 applies a first bandpass filter to a plurality of harmonic signals to select harmonic signals that fall within a second frequency range. The selected harmonic signal is output from the up-conversion filter circuit 218 as a second frequency source signal S2. The first bandpass filter is centered around the Nth harmonic signal, where N>2 (N=1 is the fundamental signal or the first frequency source signal S1). Therefore, the second frequency source signal S2 is a chirped signal having a lower limit frequency of N*B1 and an upper limit frequency of N*B2, as shown in the third graph 234. Therefore, the second frequency reflected signal R2 is within a range of a lower limit frequency of N*B1 and an upper limit frequency of N*B2, as shown in the fourth graph 236.

[0027] The multiple harmonics are also sent from the amplifier circuit 216 to the reference signal circuit 214 to generate the reference signal S ref The reference signal circuit 214 applies a second bandpass filter to the plurality of harmonic signals. The second bandpass filter is centered on a harmonic frequency that is smaller than the second frequency source signal S2. In other words, since the first bandpass filter selects the Nth harmonic signal, the second bandpass filter selects the (N-1)th harmonic signal. As a result, the reference signal S ref is a chirp signal having a lower limit frequency of (N−1)*B1 and an upper limit frequency of (N−1)*B2, as shown in the fifth graph 238 .

[0028] The down-conversion channel 212 includes a mixing circuit 220 and a down-conversion filter circuit 222. The mixing circuit 220 combines the reference signal with the signal received at the receiver 208 (ie, the second frequency reflected signal R2). The mixing circuit 220 combines the reference signal S ref The second frequency reflected signal R2 is multiplied to generate at least a sum signal and a difference signal, both of which are sent to down-conversion filter circuit 222. The difference signal is within the first frequency range (i.e., between B1 and B2). Down-conversion filter circuit 222 applies a third bandpass filter centered on the fundamental frequency (i.e., N=1) to select the difference signal. The selected signal is sent to base radar system 202, which identifies the difference signal as the first frequency reflected signal R1.

[0029] Figure 3 A high frequency radar system 200 in a selected embodiment is shown. The high frequency radar system 200 uses a signal from a basic radar system 202 operating at 80 GHz to transmit a 240 GHz signal. The basic radar system 202 generates a low frequency chirp signal (i.e., a first frequency source signal S1) within a frequency range having a lower limit frequency of 80 GHz and an upper limit frequency of 81 GHz. After generating multiple harmonics at the amplifier circuit 216 and filtering the harmonics at the up-conversion filter circuit 218, the second frequency source signal S2 operates within a frequency range having a lower limit frequency of 240 GHz and an upper limit frequency of 243 GHz. The reference signal selected by the second bandpass filter operates within a frequency range having a lower limit frequency of 160 GHz and an upper limit frequency of 162 GHz. The second frequency reflected signal R2 is within a frequency range having a lower limit frequency of 240 GHz and an upper limit frequency of 243 GHz. By comparing the second frequency reflected signal R2 with the reference signal S ref The first frequency reflection signal R1 obtained by multiplying and filtering the product at the down-conversion filter circuit 222 is within a frequency range having a lower limit frequency of 80 GHz and an upper limit frequency of 81 GHz.

[0030] Figure 4 A graph 400 illustrates a signal response in the time domain obtained using the method disclosed herein for determining a target at a selected distance of forty meters. Graph 400 shows time in microseconds along the x-axis and frequency in gigahertz along the y-axis. High-frequency radar system 200 operates to generate a signal response 402 at a single frequency proportional to the target distance. For the illustrative embodiment, the frequency of the signal response is approximately 0.032 gigahertz.

[0031] Figure 5 Shown Figure 4FIG4 is a frequency distribution graph 500 of a signal response 402 in frequency space. The frequency distribution includes a central peak 502 at 0.032 GHz with an intensity of approximately 70 decibels (dB). Various sidelobes (e.g., sidelobes 504) surrounding the central peak 502 are less than approximately -15 dB. Therefore, the signal response 402 has a high signal-to-noise ratio.

[0032] While the high frequency radar system 200 discussed herein can be used to determine the distance or location of an object, the high frequency radar system can be used to determine additional parameters such as azimuth, elevation, and Doppler (or object velocity) using known methods. In addition, a second frequency converter can be coupled between the frequency converter 204 and the transmitter 206 and the receiver 208 to generate a frequency converter operating in a higher frequency range than that provided by the frequency converter 204 (i.e., for Figure 3 The additional frequency converter can up-convert the second frequency source signal S2 to a third frequency source signal for transmission at the transmitter 206 and can down-convert the third frequency reflected signal received at the receiver 208 to obtain the second frequency reflected signal S2.

[0033] Although the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the basic scope of the present disclosure. Therefore, it is intended that the present disclosure is not limited to the particular embodiments disclosed, but is intended to include all embodiments falling within its scope.

Claims

1. A method for detecting parameters of an object, comprising: Obtaining a first frequency source signal within a first frequency range; generating a second frequency source signal within a second frequency range from the first frequency source signal; generating a first frequency reflection signal within the first frequency range from a second frequency reflection signal within the second frequency range, wherein the second frequency reflection signal indicates reflection of the second frequency source signal from the object; determining a parameter of the object from the first frequency reflection signal; generating a reference signal within a third frequency range from the first frequency source signal, and combining the reference signal with the second frequency reflected signal to generate the first frequency reflected signal; generating a plurality of harmonic signals from the first frequency source signal; applying a first filter to the plurality of harmonic signals to select an Nth harmonic signal within a second frequency range as the second frequency source signal; and A second filter is applied to the plurality of harmonic signals to select an (N-1)th harmonic signal within a third frequency range as the reference signal. 2 . The method of claim 1 , wherein the second frequency range is greater than the first frequency range, and the third frequency range is between the first frequency range and the second frequency range.

3. The method of claim 1 , wherein the first frequency source signal is a linear frequency modulation (LFM) signal within a first frequency range defined by a lower limit frequency B1 and an upper limit frequency B2, the second frequency source signal is an LFM signal within a second frequency range defined by N*B1 and N*B2, and the reference signal is an LFM signal in a third frequency range defined by (N-1)*B1 and (N-1)*B2.

4. A radar system for a vehicle, comprising: a basic radar configured to generate a first frequency source signal within a first frequency range and receive a first frequency reflected signal within the first frequency range, the basic radar being configured to determine a parameter of the object from the first frequency reflected signal; a frequency converter configured to convert a first frequency source signal into a second frequency source signal within a second frequency range, and to convert a second frequency reflected signal within the second frequency range into a first frequency reflected signal, and to generate a reference signal within a third frequency range from the first frequency source signal, and to combine the reference signal with the second frequency reflected signal to generate the first frequency reflected signal; an amplifier circuit configured to generate a plurality of harmonic signals from the first frequency source signal; a filter circuit configured to apply a first filter to the plurality of harmonic signals to select an Nth harmonic signal within a second frequency range as the second frequency source signal; and A reference signal circuit is configured to apply a second filter to the plurality of harmonic signals to select an (N-1)th harmonic signal within a third frequency range as the reference signal. 5 . The radar system of claim 4 , wherein the second frequency range is greater than the first frequency range, and the third frequency range is between the first frequency range and the second frequency range.

6. The radar system according to claim 4, wherein the first frequency source signal is a linear frequency modulation (LFM) signal within a first frequency range defined by a lower limit frequency B1 and an upper limit frequency B2, the second frequency source signal is an LFM signal within a second frequency range defined by N*B1 and N*B2, and the reference signal is an LFM signal within a third frequency range defined by (N-1)*B1 and (N-1)*B2.

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