Backscatter Bicyclist

R2026b

Backscatter signals from bicyclist

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backscatterbicyclistblock block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Radar Toolbox

Description

The Backscatter Bicyclist block simulates backscattered radar signals reflected from a moving bicyclist. The bicyclist consists of the bicycle and its rider. The object models the motion of the bicyclist and computes the sum of all reflected signals from multiple discrete scatterers on the bicyclist. The model ignores internal occlusions within the bicyclist. The reflected signals are computed using a multi-scatterer model developed from a 77-GHz radar system.

Scatterers are located on five major bicyclist components:

• bicycle frame and rider

• bicycle pedals

• upper and lower legs of the rider

• front wheel

• back wheel

Excluding the wheels, there are 114 scatterers on the bicyclist. The wheels contain scatterers on the rim and spokes. The number of scatterers on the wheels depends on the number of spokes per wheel, which can be specified using the NumWheelSpokes property.

Examples

Display Micro-Doppler Shift of Moving Bicyclist

Use Simulink^® to display the micro-Doppler shift of a moving bicyclist.

• Open Script

Ports

Input

X — Incident radar signals

complex-valued M-by-N matrix

Incident radar signals on each bicyclist scatterer, specified as a complex-valued M-by-N matrix. M is the number of samples in the signal. N is the number of point scatterers on the bicyclist and is determined partly from the number of spokes in each wheel, N_ws. See Bicyclist Scatterer Indices for the column representing the incident signal at each scatterer.

The size of the first dimension of the input matrix can vary to simulate a changing signal length. A size change can occur, for example, in the case of a pulse waveform with variable pulse repetition frequency.

Data Types: double
Complex Number Support: Yes

AngH — Bicyclist heading

0.0 | scalar

Heading of the bicyclist, specified as a scalar. Heading is measured in the xy-plane from the x-axis towards the y-axis. Units are in degrees.

Example: -34

Data Types: double

Ang — Directions of incident signals

real-valued 2-by-N vector

Directions of incident signals on the scatterers, specified as a real-valued 2-by-N matrix. Each column of Ang specifies the incident direction of the signal to the corresponding scatterer. Each column takes the form of an [AzimuthAngle;ElevationAngle] pair. Units are in degrees. See Bicyclist Scatterer Indices for the column representing the incident arrival angle at each scatterer.

Data Types: double

Speed — Bicyclist speed

nonnegative scalar

Speed of bicyclist, specified as a nonnegative scalar. The motion model limits the speed to 60 m/s. Units are in meters per second.

Example: 8

Data Types: double

Coast — Bicyclist coasting state

false (default) | true

Bicyclist coasting state, specified as false or true. This property controls the coasting of the bicyclist. If set to true, the bicyclist does not pedal but the wheels are still rotating (freewheeling). If set to false, the bicyclist is pedaling and the Gear transmission ratio parameter determines the ratio of wheel rotations to pedal rotations.

Tunable: Yes

Data Types: Boolean

Output

Y — Combined reflected radar signals

complex-valued M-by-1 column vector

Combined reflected radar signals, returned as a complex-valued M-by-1 column vector. M equals the number of samples in the input signal, X.

Data Types: double
Complex Number Support: Yes

Pos — Positions of scatterers

real-valued 3-by-N matrix

Positions of scatterers, returned as a real-valued 3-by-N matrix. N is the number of scatterers on the bicyclist. Each column represents the Cartesian position, [x;y;z], of one of the scatterers. Units are in meters. See Bicyclist Scatterer Indices for the column representing the position of each scatterer.

Data Types: double

Vel — Velocity scatterers

real-valued 3-by-N matrix

Velocity of scatterers, returned as a real-valued 3-by-N matrix. N is the number of scatterers on the bicyclist. Each column represents the Cartesian velocity, [vx;vy;vz], of one of the scatterers. Units are in meters per second. See Bicyclist Scatterer Indices for the column representing the velocity of each scatterer.

Data Types: double

Ax — Orientation of scatterers

real-valued 3-by-3 matrix

Orientation axes of scatterers, returned as a real-valued 3-by-3 matrix.

Data Types: double

Parameters

Number of wheel spokes — Number of spokes per wheel

20 (default) | positive integer

Number of spokes per wheel of the bicycle, specified as a positive integer from 3 through 50, inclusive. Units are dimensionless.

Data Types: double

Gear transmission ratio — Ratio of wheel rotations to pedal rotations

1.5 (default) | positive scalar

Ratio of wheel rotations to pedal rotations, specified as a positive scalar. The gear ratio must be in the range 0.5 through 6. Units are dimensionless.

Data Types: double

Signal carrier frequency (Hz) — Carrier frequency

77e9 (default) | positive scalar

Carrier frequency of narrowband incident signals, specified as a positive scalar. Units are in Hz.

Example: 1e9

Data Types: double

Initial position (m) — Initial position of bicyclist

[0;0;0] (default) | 3-by-1 real-valued vector

Initial position of the bicyclist, specified as a 3-by-1 real-valued vector in the form of [x;y;z]. Units are in meters.

Data Types: double

Initial heading direction (deg) — Initial heading of bicyclist

0 (default) | scalar

Initial heading of the bicyclist, specified as a scalar. Heading is measured in the xy-plane from the x-axis towards y-axis. Units are in degrees.

Data Types: double

Initial bicyclist speed (m/s) — Initial speed of bicyclist

4 (default) | nonnegative scalar

Initial speed of bicyclist, specified as a nonnegative scalar. The motion model limits the speed to a maximum of 60 m/s (216 kph). Units are in meters per second.

Tunable: Yes

Data Types: double

Propagation speed (m/s) — Signal propagation speed

physconst('LightSpeed') (default) | positive scalar

Signal propagation speed, specified as a real-valued positive scalar. The default value of the speed of light is the value returned by physconst('LightSpeed').

Data Types: double

RCS pattern — Source of RCS pattern

Auto (default) | Property

Source of the RCS pattern, specified as either Auto or Property. When you specify Auto, the pattern is a 1-by-361 matrix containing values derived from radar measurements taken at 77 GHz.

Azimuth angles (deg) — Azimuth angles

[-180:180] (default) | 1-by-P real-valued row vector | P-by-1 real-valued column vector

Azimuth angles used to define the angular coordinates of each column of the matrix specified by the Radar cross section pattern (square meters) parameter. Specify the azimuth angles as a length P vector. P must be greater than two. Angle units are in degrees.

Example: [-45:0.1:45]

Dependencies

To enable this parameter, set the RCS pattern parameter to Property.

Data Types: double

Elevation angles (deg) — Elevation angles

[-90:90] (default) | 1-by-Q real-valued row vector | Q-by-1 real-valued column vector

Elevation angles used to define the angular coordinates of each row of the matrix specified by the Radar cross section pattern (square meters) parameter. Specify the elevation angles as a length Q vector. Q must be greater than two. Angle units are in degrees.

Dependencies

To enable this parameter, set the RCS pattern parameter to Property.

Data Types: double

Radar cross section pattern (square meters) — Radar cross-section pattern

1-by-361 real-valued matrix (default) | Q-by-P real-valued matrix | 1-by-P real-valued vector

Radar cross-section (RCS) pattern as a function of elevation and azimuth angle, specified as a Q-by-P real-valued matrix or a 1-by-P real-valued vector. Q is the length of the vector defined by the ElevationAngles property. P is the length of the vector defined by the AzimuthAngles property. Units are in square meters.

You can also specify the pattern as a 1-by-P real-valued vector of azimuth angles for one elevation.

The default value of this property is a 1-by-361 matrix containing values derived from radar measurements taken at 77 GHz found in backscatterBicyclist.defaultRCSPattern.

Dependencies

To enable this parameter, set the RCS pattern parameter to Property.

Data Types: double

Simulate using — Block simulation method

Interpreted Execution (default) | Code Generation

Block simulation, specified as Interpreted Execution or Code Generation. If you want your block to use the MATLAB^® interpreter, choose Interpreted Execution. If you want your block to run as compiled code, choose Code Generation. Compiled code requires time to compile but usually runs faster.

Interpreted execution is useful when you are developing and tuning a model. The block runs the underlying System object™ in MATLAB. You can change and execute your model quickly. When you are satisfied with your results, you can then run the block using Code Generation. Long simulations usually run faster as compiled code than interpreted execution. You can run repeated executions without recompiling, but if you change any block parameters, then the block automatically recompiles before execution.

This table shows how the Simulate using parameter affects the overall simulation behavior.

When the Simulink model is in Accelerator mode, the block mode specified using Simulate using overrides the simulation mode.

Acceleration Modes

Block Simulation	Simulation Behavior
	Normal	Accelerator	Rapid Accelerator
Interpreted Execution	The block executes using the MATLAB interpreter.	The block executes using the MATLAB interpreter.	Creates a standalone executable from the model.
Code Generation	The block is compiled.	All blocks in the model are compiled.

For more information, see Choosing a Simulation Mode (Simulink).

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"radarlib/Backscatter Bicyclist"

Example: add_block("radarlib/Backscatter Bicyclist","myModel/myBlock",MakeNameUnique="on")

More About

Bicyclist Scatterer Indices

Bicyclist scatterer indices define which columns in the scatterer position or velocity matrices contain the position and velocity data for a specific scatterer. For example, column 92 of bpos specifies the 3-D position of one of the scatterers on a pedal.

The wheel scatterers are equally divided between the wheels. You can determine the total number of wheel scatterers, N, by subtracting 113 from the output of the getNumScatterers function. The number of scatterers per wheel is N_sw = N/2.

Bicyclist Scatterer Indices

Bicyclist Component	Bicyclist Scatterer Index
Frame and rider	1 … 90
Pedals	91 … 99
Rider legs	100 … 113
Front wheel	114 … 114 + Nsw - 1
Rear wheel	114 + Nsw … 114 + N - 1

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2021a