# blindvelocitymap

## Syntax

## Description

`blindvelocitymap(___)`

plots the blind velocity
map.

## Examples

### Display Blind Velocity Map

A 10 GHz X-band medium PRF radar has a rejection notch to reject slow moving targets with velocities up to 20 m/s. Plot a blind velocity map for pulse repetition frequencies between 5 kHz and 15 kHz, assuming that velocities from 90 m/s to 115 m/s and from 155 m/s to 165 m/s are obstructed due to clutter.

Set up velocities and PRF.

V = linspace(0,500,1000); PRF = linspace(5e3,15e3,1000);

Set the radar frequency to 10 GHz.

`fc = 10e9; % Rejection notch half-width (m/s)`

Set the velocity obstructions.

obstructions = [90 115;155 165];

Set the rejection notch half-width to 20 meters/sec.

vmin = 20;

Create the blind velocity map.

blindvelocitymap(V,PRF,fc,vmin,obstructions)

## Input Arguments

`V`

— Velocities

length-*J* real-valued vector

Radar velocities, specified as a length-*J* real-valued vector of
positive values. The function computes the blind velocity map at these velocities Units
are in meters/sec.

**Example: **`[4000,4500,6000]`

**Data Types: **`double`

`PRF`

— Pulse repetition frequencies

length-*N* vector of positive values

Pulse repetition frequencies, specified as a length-*N* vector of
positive values. Units are in Hz.

**Example: **`[10000,15000]`

**Data Types: **`double`

`fc`

— Radar waveform carrier frequency

positive scalar (default) | length-*N* vector of positive values

Radar waveform carrier frequency, specified as a positive scalar or
length-*N* vector of positive values. If the radar transmits pulses
at a fixed carrier frequency, the input `fc`

is a scalar. If the
radar employs frequency diversity using a different carrier frequency for each PRF
value, `fc`

is a length-*N* vector where
*N* is the size of `PRF`

.

**Example: **`3e9`

**Data Types: **`double`

`vmin`

— Minimum detectable velocity

scalar (default) | length-*N* real-valued vector

Minimum detectable velocity, specified as a scalar or length-*N*
real-valued vector. A blind zone due to a non-zero minimum detectable velocity extends
from -`vmin`

to +`vmin`

for all
`PRF`

values.

If the radar has the same minimum detectable velocity for all

`PRF`

s,`vmin`

is a scalar and the size of the blind zone is constant for all`PRF`

values.If the minimum detectable velocity varies with

`PRF`

,`vmin`

is a length-*N*vector and the size of the blind zone is different for each`PRF`

.

Due to ambiguities in velocity, blind zones also appear around integer
multiples of the blind speed *V _{B}* and extend
from

*V*to

_{B}*i - V_{min}*V*, where

_{B}*i + V_{min}*V*,

_{B}= PRF*c/(2*fc)*c*is the signal propagation speed, and

*i*is an integer. The input

`vmin`

can represent the half-width of a rejection notch that is
used to reject main lobe clutter and slow moving targets. Units are in
meters/sec.**Example: **`15.0`

**Data Types: **`double`

`obstr`

— Obstructions in velocity

*Q*-by-2 matrix

Obstructions in velocity, specified as a *Q*-by-2 matrix of
positive values. The `q`

row specifies a
velocity obstruction in the form ^{th}`[vstartq,vstopq]`

where
`vstartq`

is the start velocity of the
`q`

^{Th} obstruction and
`vstopq`

is the stop velocity of the
`q`

obstruction, such that
^{th}`vstopq`

≥ `vstartq`

. Targets moving with the
specified obstructed velocities or velocities ambiguous to the specified obstructed
velocities are not visible to the radar. Such obstructions can occur due to clutter.
Entries in `BVM`

that correspond to the obstructed velocities are set
to a logical one (`true`

). Units are in meters/second.

**Example: **`[30000;31000]`

**Data Types: **`double`

## Output Arguments

`BVM`

— Blind velocity map

*J*-by-*N* logical matrix

Blind velocity map, returned as a *J*-by-*N*
logical matrix. The `j`

row of
^{th}`BVM`

represents a velocity cell with the velocity equal to the
`j`

entry in ^{th}`V`

.
The `n`

column of ^{th}`BVM`

corresponds to the `j`

pulse repetition
frequency in ^{th}`PRF`

. If the
`j`

velocity in ^{th}`V`

is visible to the radar at the `n`

PRF,
^{th}`BVM`

`(j,n)`

is a logical zero
(`false`

), otherwise `BVM`

`(j,n)`

is a logical one (`true`

).

**Data Types: **`logical`

## Extended Capabilities

### C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

## Version History

**Introduced in R2023a**

## See Also

## Open Example

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