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Doppler estimation

The `phased.DopplerEstimator`

System
object™ estimates
Doppler frequencies of targets. Input to the estimator consists of
detection locations output from a detector, and a range-Doppler response
data cube. When detections are clustered, the Doppler frequencies
are computed using cluster information. Clustering associates multiple
detections into one extended detection.

To compute Doppler values for detections:

Define and set up your Doppler estimator using the Construction procedure that follows.

Call the

`step`

method to compute the Doppler of detections, using the properties you specify for the`phased.DopplerEstimator`

System object.

Instead of using the `step`

method to perform
the operation defined by the System
object, you can call the object
with arguments, as if it were a function. For example, ```
y
= step(obj,x)
```

and `y = obj(x)`

perform
equivalent operations.

`estimator = phased.DopplerEstimator`

creates
a Doppler estimator System
object, `estimator`

.

`estimator = phased.DopplerEstimator(`

creates
a System
object, `Name`

,`Value`

)`estimator`

, with each specified
property `Name`

set to the specified `Value`

.
You can specify additional name and value pair arguments in any order
as (`Name1,Value1`

,...,`NameN,ValueN`

).

step | Estimate target Doppler |

Common to All System Objects | |
---|---|

`clone` | Create System object with same property values |

`getNumInputs` | Expected number of inputs to a System object |

`getNumOutputs` | Expected number of outputs of a System object |

`isLocked` | Check locked states of a System object (logical) |

`release` | Allow System object property value changes |

The `phased.DopplerEstimator`

System
object estimates
the Doppler frequency of a detection by following these steps of the
Doppler estimator are

Input a Doppler-processed response data cube obtained from the

`phased.RangeDopplerResponse`

System object. The first dimension of the cube represents the fast-time or equivalent range of the returned signal samples. The second dimension represents the spatial information, such as sensors or beams. The last dimension represents the response as a function of Doppler frequency. Only this dimension is used to estimate detection Doppler frequency. All others are ignored. See Radar Data Cube.Input the matrix of detection indices that specify the location of detections in the data cube. Each column denotes a separate detection. The row entries designate indices into the data cube. To return these detection indices as an output of the

`phased.CFARDetector`

or`phased.CFARDetector2D`

detectors. To return these indices, set the detector`OutputFormat`

property of either CFAR detector to`'Detection index'`

.Optionally input a row vector of cluster IDs. This vector is equal in length to the number of detections. Each element of this vector assigns an ID to a corresponding detection. To form clusters of detections, the same ID can be assigned to more than one detection. To enable this option, set the

`ClusterInputPort`

property to`true`

.When

`ClusterInputPort`

is`false`

, the object computes Doppler frequencies for each detection. The algorithm finds the response values at the detection index and at two adjacent indices in the cube along the Doppler dimension. Then, the algorithm fits a quadratic curve to the magnitudes of the Doppler response at these three indices. The peak of the curve indicates the detection location. When detections occur at the first or last sample in the Doppler dimension, the object estimates the detection location from a two-point centroid. The centroid is formed using the location of the detection index and the sample next to the detection index.When the object computes Doppler frequencies for each cluster. The algorithm finds the indices of the largest response value in the cluster. Then, the algorithm fits a quadratic curve to that detection in the same way as for individual detections.

The object converts the fractional index values to Doppler frequency or speed by using appropriate units from the

`dopgrid`

input argument of the`step`

method. You can obtain values for`dopgrid`

using the`phased.RangeDopplerResponse`

System object.

[1] Richards, M. *Fundamentals of Radar Signal
Processing.* 2nd ed. McGraw-Hill Professional Engineering,
2014.

[2] Richards, M., J. Scheer, and W. Holm, * Principles
of Modern Radar: Basic Principles*. SciTech Publishing,
2010.

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