Mimo detector device useful for automated vehicles

BACKGROUND

0001Innovations in electronics and technology have made it possible to incorporate a variety of advanced features on automotive vehicles. Various sensing technologies have been developed for detecting objects or monitoring the surroundings in a vicinity or pathway of a vehicle. Such systems are useful for parking assist, lane departure detection and cruise control adjustment features, for example.

0002More recently, automated vehicle features have become possible to allow for autonomous or semi-autonomous vehicle control. Sensors for such systems may incorporate LIDAR (light detection and ranging) or RADAR for detecting an object or another vehicle in the pathway of or otherwise near the vehicle. Depending on the approach speed, the cruise control setting may be automatically adjusted to reduce the speed of the vehicle based on detecting another vehicle in the pathway of the vehicle, for example.

0003One proposal to improve such sensing technologies includes using a multiple-input-multiple-output (MIMO) signaling technique that includes multiple, simultaneous signal transmissions. There are known ways to modulate such signals so that the different signals can be distinguished from each other at a receiver. One modulation technique includes a distinct modulation code for each signal. The codes allow for distinguishing the different signals from each other at the receiver in a known manner.

0004One difficulty introduced by MIMO techniques is the residue or noise associated with the multiple signal reception. Such residue reduces the signal-to-noise ratio and decreases the dynamic range of the device or system. It would be useful to be able to reduce the effect of such residue so that the other advantages of MIMO techniques can be realized with an automotive sensing device. Previously proposed approaches to removing or reducing the effects of such residue tend to be too computationally expensive and require too much processor capacity to be included on automotive vehicles.

SUMMARY

0005An illustrative example embodiment of a detector device includes a receiver configured to receive radiation comprising a plurality of codes. Each of the codes is associated with one of a plurality of transmissions and each of the codes is distinct from the other codes. A processor is configured to obtain information corresponding to at least one predetermined phase code spectrum for the codes, determine a demodulated signal spectrum of radiation received by the at least one receiver, determine at least one characteristic of the determined demodulated signal spectrum, adjust the at least one predetermined phase code spectrum based on the determined characteristic to generate an adjusted phase code spectrum, and refine the determined demodulated signal spectrum based on the adjusted phase code spectrum to generate a refined demodulated signal spectrum.

0006An illustrative example method of detecting includes receiving radiation comprising a plurality of codes that are distinct from each other and determining a demodulated signal spectrum of the received radiation. There is at least one predetermined phase code spectrum for the codes. The method includes determining at least one characteristic of the determined demodulated signal spectrum, adjusting the predetermined phase code spectrum based on the determined characteristic to generate an adjusted phase code spectrum, and refining the determined demodulated signal spectrum based on the adjusted phase code spectrum to generate a refined demodulated signal spectrum.

0007Various features and advantages of at least one disclosed embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

0008<figref idref="DRAWINGS">FIG. 1</figref> schematically illustrates a vehicle including detector devices designed according to an embodiment of this invention.

0009<figref idref="DRAWINGS">FIG. 2</figref> schematically illustrates selected components of an example detector device designed according to an embodiment of this invention.

0010<figref idref="DRAWINGS">FIG. 3</figref> is a flowchart diagram summarizing an example detecting method according to an embodiment of this invention.

0011<figref idref="DRAWINGS">FIG. 4</figref> schematically illustrates a phase code spectrum of a modulation code.

0012<figref idref="DRAWINGS">FIG. 5</figref> schematically illustrates a demodulated signal spectrum of received radiation including at least two modulation codes and residue.

0013<figref idref="DRAWINGS">FIG. 6</figref> schematically illustrates an adjusted phase code spectrum corresponding to the phase code spectrum of <figref idref="DRAWINGS">FIG. 4</figref> adjusted based on information from the demodulated signal spectrum of <figref idref="DRAWINGS">FIG. 5</figref>.

0014<figref idref="DRAWINGS">FIG. 7</figref> schematically illustrates a refined demodulated signal spectrum that is based on the demodulated signal spectrum of <figref idref="DRAWINGS">FIG. 5</figref> and the adjusted phase code spectrum of <figref idref="DRAWINGS">FIG. 6</figref>.

DETAILED DESCRIPTION

0015Embodiments of this invention include detector devices that provide an ability to remove residue or noise from received radiation including a plurality of codes used for MIMO transmissions. Such devices are useful for a variety of vehicle applications, such as detectors on automated vehicles or semi-autonomous vehicles. Such detectors are also useful for assisting drivers of automotive vehicles.

0016<figref idref="DRAWINGS">FIG. 1</figref> schematically illustrates an example vehicle <b>20</b> including a detector device <b>22</b> that is configured for use with MIMO transmission or signaling techniques. In some examples, the detector device <b>22</b> is capable of detecting RADAR radiation that is reflected off at least one object <b>24</b> in the vicinity or path of the vehicle <b>20</b>. Two objects <b>24</b>A and <b>24</b>B are illustrated in <figref idref="DRAWINGS">FIG. 1</figref>. The transmitted radiation is schematically illustrated at <b>26</b> and the reflected wave or radiation is shown at <b>28</b>. The transmitted and detected radiation may be considered signals or waves, for example.

0017<figref idref="DRAWINGS">FIG. 2</figref> schematically illustrates an example configuration of the detector device <b>22</b>. In this example, the detector device <b>22</b> has components for transmitting and receiving radiation. Some embodiments do not include the transmitting components as part of the detector device <b>22</b> but, instead, have separate transmitting and receiving or detecting devices.

0018A radiation generator <b>30</b> provides or produces radiation, such as RADAR. A first modulation module <b>32</b> modulates the radiation by applying or inserting a first modulation code into radiation emitted by a first transmitter element <b>34</b>, such as an antenna. A second modulation module <b>36</b> modulates the radiation by applying or inserting a second modulation code into radiation emitted by a second transmitter element <b>38</b>, which comprises an antenna in this example. The first and second modulation codes effectively establish first and second transmissions <b>26</b>A, <b>26</b>B that are distinguishable from each other by demodulating or otherwise recognizing the respective codes of the transmissions. While two transmitter elements and two codes are included in the illustration, more than two are useful in many embodiments. Each modulation code is distinct from other codes used for transmissions from the device <b>22</b>.

0019The device <b>22</b> includes at least one receiver element <b>40</b>, such as an antenna, that receives or detects the reflected radiation <b>28</b> that includes a reflection of the first transmission <b>26</b>A and the second transmission <b>26</b>B from each of the objects <b>24</b>. The received or detected radiation includes the first and second modulation codes. A processor <b>42</b> includes a reception processing module <b>44</b> that includes programming that configures the processor <b>42</b> to be able to discern between the modulation codes in the received radiation and to otherwise process the received radiation according to this description.

0020A memory <b>46</b> contains information regarding at least one predetermined phase code spectrum for the plurality of codes used by the device <b>22</b>. In some examples, the memory <b>46</b> includes a unique phase code spectrum for each code that may be used for transmissions <b>26</b>. In some examples, the predetermined phase code spectrum is based on more than one code using a known combination technique.

0021Although the memory <b>46</b> is schematically shown as part of the processor <b>42</b> in the illustration, the memory <b>46</b> need not be physically part of the processor <b>42</b>. In some embodiments the memory <b>46</b> comprises components that are separate or distinct from components of the processor <b>42</b>. In such examples, the processor <b>42</b> has access to the memory <b>46</b> to obtain the predetermined phase code spectrum information as needed by the processor <b>42</b>.

0022In some embodiments the phase codes spectrum is determined in real time by the processor <b>42</b>. There may not be any requirement for a memory to store phase code spectrum information on an ongoing basis in such embodiments.

0023A target information determination module <b>48</b> includes programming that configures the processor <b>42</b> to be able to determine information regarding an object, such as the object <b>24</b>. The information regarding such an object may be a location of the object, a direction of movement of the object, a speed of movement of the object relative to the vehicle <b>20</b>, or a combination of those.

0024The processor <b>42</b> may be a dedicated processor having its own components used exclusively to perform the functions of the processor <b>42</b> described in this document. In some embodiments the processor <b>42</b> is part of a controller or processor that is used for other features or purposes on the vehicle <b>20</b>. The processor <b>42</b> is schematically illustrated as a single device but some embodiments include a processor realized through the functionality of components or software associated with a plurality of devices. The processor in this example includes at least one computing device configured to make the determinations described in this document and suitable programming for those purposes.

0025<figref idref="DRAWINGS">FIG. 3</figref> is a flowchart diagram <b>50</b> that summarizes an example detecting method designed according to an embodiment of this invention. The example method begins at <b>52</b> where the processor <b>42</b> obtains information regarding the predetermined phase code spectrum information, which may be accomplished by accessing such information stored in the memory <b>46</b> or by determining the phase code spectrum in real time. <figref idref="DRAWINGS">FIG. 4</figref> includes a plot <b>54</b> representing an example phase code spectrum for one of the plurality of known codes. The memory <b>46</b> in this example includes information sufficient to allow the reception processing module <b>44</b> to use the relevant aspects of the predetermined phase code spectrum. Those skilled in the art who have the benefit of this description will realize what aspects of the phase code spectrum should be stored in memory or determined in real time to meet the needs of their particular implementation. In some examples, the predetermined phase code spectrum will be based on more than one of the plurality of known codes.

0026At <b>56</b> in <figref idref="DRAWINGS">FIG. 3</figref>, radiation is received or detected by the receiver element <b>40</b> after that radiation reflected off the object <b>24</b>. In some instances the received radiation will not necessarily be reflected off an object although in a RADAR implementation as schematically shown, the reflected radiation provides the information needed for the target information determination module <b>48</b> to provide the desired information regarding an object of interest.

0027At <b>58</b> the demodulated signal spectrum of the received radiation is determined by the reception processing module <b>44</b> of the processor <b>42</b>. <figref idref="DRAWINGS">FIG. 5</figref> includes a plot <b>60</b> of such a demodulated signal spectrum. In this example, the demodulated signal spectrum includes a plurality of peaks but only one peak at <b>62</b> has a magnitude that exceeds a preselected threshold <b>63</b>.

0028At <b>64</b> the processor <b>42</b> determines at least one characteristic of the demodulated signal spectrum shown at <b>60</b>. In this example, the characteristic is based on the peak <b>62</b>. In particular, the characteristic in this example includes information regarding the peak such as the complex amplitude of the spectrum plot at the peak <b>62</b> and the frequency at which the peak <b>62</b> occurs.

0029The processor adjusts the predetermined phase code spectrum at <b>66</b>. The adjustment is based on the determined characteristic of the determined demodulated signal spectrum <b>60</b> of the received radiation. In this embodiment, the predetermined phase code spectrum is shifted by an amount corresponding to the frequency at which the peak <b>62</b> occurs. The shifted spectrum is multiplied by the corresponding complex amplitude. A result of the adjustment is shown at <b>68</b> in <figref idref="DRAWINGS">FIG. 6</figref> and can be referred to as an adjusted phase code spectrum. The adjusted phase code spectrum <b>68</b> corresponds to the residue in the received radiation, which is caused by the reflection from the objects <b>24</b>.

0030Where there are multiple codes in the received radiation and there is one predetermined phase code spectrum for each code in the memory <b>46</b>, the processor <b>42</b> determines an adjusted phase code spectrum for each code and determines a sum of the adjusted spectrums to estimate the residue. That residue estimate is then used as the adjusted phase code spectrum for refining the determined demodulated signal spectrum of the received radiation at <b>70</b> in <figref idref="DRAWINGS">FIG. 3</figref>.

0031The reception processing module <b>44</b> of the processor <b>42</b> refines the determined demodulated signal spectrum at <b>70</b> based on the adjusted phase code spectrum to generate a refined demodulated signal spectrum. In this example, the adjusted phase code spectrum is subtracted from the determined demodulated signal spectrum resulting in a refined demodulated signal spectrum as represented by the plot <b>72</b> in <figref idref="DRAWINGS">FIG. 7</figref>. Subtracting the adjusted phase code spectrum from the determined demodulated signal spectrum effectively removes the residue from the received radiation.

0032As can be appreciated from <figref idref="DRAWINGS">FIG. 7</figref>, the peak <b>62</b>′ is more pronounced than the peak <b>62</b> in <figref idref="DRAWINGS">FIG. 5</figref>. Additionally, a second peak <b>74</b> corresponding to the second object <b>24</b>B from which the received radiation reflected is discernable in <figref idref="DRAWINGS">FIG. 7</figref> because the residue, which effectively masked the second peak <b>74</b> in the demodulated signal spectrum <b>60</b> of <figref idref="DRAWINGS">FIG. 5</figref>, has been removed.

0033<figref idref="DRAWINGS">FIG. 7</figref> also includes a dashed line plot <b>76</b> representing a result if a single signal transmission were reflected from the objects <b>24</b> without using a MIMO technique. <figref idref="DRAWINGS">FIG. 7</figref> demonstrates how well the example detecting technique addresses the problems or complications introduced by the residue associated with MIMO reception and allows for identifying characteristics of received or detected radiation for obtaining information regarding an object in the vicinity or pathway of the vehicle <b>20</b>. The example device and process makes it possible to enjoy the benefits or advantages of MIMO techniques while maintaining a desired signal-to-noise ratio and dynamic range.

0034The process summarized in <figref idref="DRAWINGS">FIG. 3</figref> includes a single iteration of refining the determined demodulated signal spectrum of the received radiation. Some embodiments include multiple iterations in which the adjusting and refining portions of the process are repeated to further refine the determined demodulated signal spectrum. Using multiple iterations increases accuracy in estimating the residue and identifying information or characteristics of an object such as the objects <b>24</b>A and <b>24</b>B in at least some cases.

0035The disclosed embodiment allows for estimating residue at a much lower computational cost than that associated with previously proposed techniques. The residue estimation and removal of the disclosed embodiment can be accomplished without extensive or complicated transform or convolution calculations. Instead, the disclosed example utilizes the property of the convolution of a signal with an impulse signal.

0036The convolution of a signal, S(f) with an impulse, δ(f-f₀) is a shifted version of SW, which is given by S(f-f₀). With the original signal spectrum S(f) known, the shifted spectrum, S(f-f₀) is known immediately and no additional computation is needed. The disclosed embodiment includes obtaining the residue estimate in this way.

0037A convolution with an impulse or delta function, δ(f-f₀) is of particular interest because the Fourier spectrum of an object of interest is given by a delta function, δ(f-f₀). The residue is given by the following equation, which uses the property of a discrete Fourier transform (DFT),

0000<maths id="MATH-US-00001" num="00001"><math overflow="scroll"><mtable><mtr><mtd><mtable><mtr><mtd><mrow><mrow><msub><mi>R</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow><mo>=</mo><mi /><mo></mo><mrow><mi>D</mi><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mi>F</mi><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mi>T</mi><mo></mo><mrow><mo>{</mo><mrow><mrow><mi>code</mi><mo></mo><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow><mo>×</mo><mrow><mi>s</mi><mo></mo><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow><mo>×</mo><mrow><mi>Win</mi><mo></mo><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow></mrow><mo>}</mo></mrow></mrow></mrow></mtd></mtr><mtr><mtd><mrow><mo>=</mo><mi /><mo></mo><mrow><mi>D</mi><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mi>F</mi><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mi>T</mi><mo></mo><mrow><mrow><mo>{</mo><mrow><mrow><mi>code</mi><mo></mo><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow><mo>×</mo><mrow><mi>Win</mi><mo></mo><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow></mrow><mo>}</mo></mrow><mo>⊗</mo><mi>D</mi></mrow><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mi>F</mi><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mi>T</mi><mo></mo><mrow><mo>{</mo><mrow><mi>s</mi><mo></mo><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow><mo>}</mo></mrow></mrow></mrow></mtd></mtr><mtr><mtd><mrow><mrow><mo>=</mo><mi /><mo></mo><mrow><mrow><msub><mi>code</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow><mo>⊗</mo><mrow><msub><mi>S</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow></mrow></mrow><mo>,</mo></mrow></mtd></mtr></mtable></mtd><mtd><mrow><mi>Equation</mi><mo></mo><mstyle><mspace width="0.8em" height="0.8ex" /></mstyle><mo></mo><mn>1</mn></mrow></mtd></mtr></mtable></math></maths>

0038where R_f(k) is the residue, code_f(k) is the spectrum of the phase code, S_f(k) is the spectrum of the radiation reflected from the object, k is the discrete Doppler index, and is the convolution symbol.

0039The radiation reflected from an object is modeled in this example as a point target or single frequency complex signal. In this case, the spectrum of the received radiation, S_f(k), is given by a delta function, δ(k-k₀). Then the residue in Equation 1 can be rewritten using the following equation.

0000<maths id="MATH-US-00002" num="00002"><math overflow="scroll"><mtable><mtr><mtd><mtable><mtr><mtd><mrow><mrow><msub><mi>R</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow><mo>=</mo><mi /><mo></mo><mrow><mrow><msub><mi>code</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow><mo>⊗</mo><mrow><mi>δ</mi><mo></mo><mrow><mo>(</mo><mrow><mi>k</mi><mo>-</mo><msub><mi>k</mi><mn>0</mn></msub></mrow><mo>)</mo></mrow></mrow></mrow></mrow></mtd></mtr><mtr><mtd><mrow><mo>=</mo><mi /><mo></mo><mrow><mrow><msub><mi>code</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mrow><mi>k</mi><mo>-</mo><msub><mi>k</mi><mn>0</mn></msub></mrow><mo>)</mo></mrow></mrow><mo>.</mo></mrow></mrow></mtd></mtr></mtable></mtd><mtd><mrow><mi>Equation</mi><mo></mo><mstyle><mspace width="0.8em" height="0.8ex" /></mstyle><mo></mo><mn>2</mn></mrow></mtd></mtr></mtable></math></maths>

0040It follows that the residue corresponding to one object is the cyclic shift of the spectrum of the code. If there are multiple objects, the residue is given by the sum of the cyclic shift of the code spectrum with different amounts of shift. This can be represented by the following relationship.

0000<maths id="MATH-US-00003" num="00003"><math overflow="scroll"><mtable><mtr><mtd><mtable><mtr><mtd><mrow><mrow><msub><mi>R</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow><mo>=</mo><mi /><mo></mo><mrow><munder><mo>∑</mo><mi>i</mi></munder><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mrow><mrow><mrow><msub><mi>code</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></mrow><mo>⊗</mo><msub><mi>α</mi><mi>i</mi></msub></mrow><mo></mo><mrow><mi>δ</mi><mo></mo><mrow><mo>(</mo><mrow><mi>k</mi><mo>-</mo><msub><mi>k</mi><mi>i</mi></msub></mrow><mo>)</mo></mrow></mrow></mrow></mrow></mrow></mtd></mtr><mtr><mtd><mrow><mo>=</mo><mi /><mo></mo><mrow><munderover><mo>∑</mo><mi>i</mi><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle></munderover><mo></mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo></mo><mrow><msub><mi>α</mi><mi>i</mi></msub><mo></mo><mrow><msub><mi>code</mi><mi>f</mi></msub><mo></mo><mrow><mo>(</mo><mrow><mi>k</mi><mo>-</mo><msub><mi>k</mi><mi>i</mi></msub></mrow><mo>)</mo></mrow></mrow></mrow></mrow></mrow></mtd></mtr></mtable></mtd><mtd><mrow><mi>Equation</mi><mo></mo><mstyle><mspace width="0.8em" height="0.8ex" /></mstyle><mo></mo><mn>3</mn></mrow></mtd></mtr></mtable></math></maths>

0041Delta functions like those included above are generally known and those skilled in the art who have the benefit of this description will realize how to configure or program a processor to utilize appropriate delta functions for their particular implementation.

0042One of the aspects of the disclosed embodiment is that all calculations and determinations are accomplished in the frequency domain. This approach avoids any need to convert between time and frequency domains. Additionally, the disclosed embodiment avoids using multiple FFTs and IFFTs between the time and frequency domains. A detecting device and method designed according to an embodiment of this invention requires less computation and processing capacity than other approaches. Instead, embodiments of this invention utilize the property of the frequency domain convolution and the point-target property of radiation reflected from an object to estimate the residue. By reducing computational complexity, the benefits of MIMO signaling techniques become more readily available for automobile detector arrangements without the drawbacks that otherwise accompany MIMO processing.

0043The preceding description is exemplary rather than limiting in nature. For example, two transmitter elements and one receiver element are shown but other numbers of each type of component may be used. Additionally, more transmissions and more codes may be used. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.