Wideband Two-Ray Channel

Wideband two-ray channel environment

• Library:

• Radar Toolbox

• 

Description

The Wideband Two-Ray Channel block propagates wideband signals from one point in space to multiple points or from multiple points back to one point via both the direct path and the ground reflection path. The block propagates wideband signals by (1) decomposing them into subbands, (2) propagating subbands independently, and (3) recombining the propagated subbands. The block models propagation time, propagation loss, and Doppler shift. The block assumes that the propagation speed is much greater than the object's speed in which case the stop-and-hop model is valid.

Ports

Input

X — Wideband input signal

M-by-N complex-valued matrix | M-by-2N complex-valued matrix

• Wideband nonpolarized scalar signal, specified as an

  • M-by-N complex-valued matrix. The quantity M is the number of samples in the signal and N is the number of two-ray channels. Each channel corresponds to a source-destination pair. Each column contains an identical signal that is propagated along the line-of-sight and reflected paths.

  • M-by-2N complex-valued matrix. The quantity M is the number of samples of the signal and N is the number of two-ray channels. Each channel corresponds to a source-destination pair. Each adjacent pair of columns represents a different channel. Within each pair, the first column represents the signal propagated along the line-of-sight path and the second column represents the signal propagated along the reflected path.

The quantity M is the number of samples of the signal and N is the number of two-ray channels. Each channel corresponds to a source-destination pair.

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.

Example: [1,1;j,1;0.5,0]

Data Types: double
Complex Number Support: Yes

Pos1 — Position of signal origin

3-by-1 real-valued column vector | 3-by-N real-valued matrix

Origin of the signal or signals, specified as a 3-by-1 real-valued column vector or 3-by-N real-valued matrix. The quantity N is the number of two-ray channels. If Pos1 is a column vector, it takes the form [x;y;z]. If Pos1 is a matrix, each column specifies a different signal origin and has the form [x;y;z]. Position units are in meters.

Pos1 and Pos2 cannot both be specified as matrices — at least one must be a 3-by-1 column vector.

Example: [1000;100;500]

Data Types: double

Pos2 — Position of signal destination

3-by-1 real-valued column vector | 3-by-N real-valued matrix

Origin of the signal or signals, specified as a 3-by-1 real-valued column vector or 3-by-N real-valued matrix. The quantity N is the number of two-ray channels. If Pos2 is a column vector, it takes the form [x;y;z]. If Pos2 is a matrix, each column specifies a different signal origin and has the form [x;y;z]. Position units are in meters.

Pos1 and Pos2 cannot both be specified as matrices — at least one must be a 3-by-1 column vector.

Example: [-100;300;50]

Data Types: double

Vel1 — Velocity of signal origin

3-by-1 real-valued column vector | 3-by-N real-valued matrix

Velocity of signal origin, specified as a 3-by-1 real-valued column vector or 3-by-N real-valued matrix. The dimensions of Vel1 must match the dimensions of Pos1. If Vel1 is a column vector, it takes the form [Vx;Vy;Vz]. If Vel1 is a 3-by-N matrix, each column specifies a different origin velocity and has the form [Vx;Vy;Vz]. Velocity units are in meters per second.

Example: [-10;3;5]

Data Types: double

Vel2 — Velocity of signal destination

3-by-1 real-valued column vector | 3-by-N real-valued matrix

Velocity of signal origin, specified as a 3-by-1 real-valued column vector or 3-by-N real-valued matrix. The dimensions of Vel2 must match the dimensions of Pos2. If Vel2 is a column vector, it takes the form [Vx;Vy;Vz]. If Vel2 is a 3-by-N matrix, each column specifies a different origin velocity and has the form [Vx;Vy;Vz]. Velocity units are in meters per second.

Example: [-1000;300;550]

Data Types: double

Output

Out — Propagated signal

M-by-N complex-valued matrix | M-by-2N complex-valued matrix

• M-by-N complex-valued matrix. To return this format, set the CombinedRaysOutput property to true. Each matrix column contains the coherently combined signals from the line-of-sight path and the reflected path.

• M-by-2N complex-valued matrix. To return this format set the CombinedRaysOutput property to false. Alternate columns of the matrix contain the signals from the line-of-sight path and the reflected path.

The output Out contains signal samples arriving at the signal destination within the current input time frame. Whenever it takes longer than the current time frame for the signal to propagate from the origin to the destination, the output may not contain all contributions from the input of the current time frame. The remaining output will appear in the next execution of the block.

Parameters

Signal propagation speed (m/s) — Signal propagation speed

physconst('LightSpeed') (default) | real-valued 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'). Units are in meters per second.

Example: 3e8

Data Types: double

Signal carrier frequency (Hz) — Signal carrier frequency

300e6 (default) | positive real-valued scalar

Signal carrier frequency, specified as a positive real-valued scalar. Units are in hertz.

Data Types: double

Number of subbands — Number of processing subbands

64 (default) | positive integer

Number of processing subbands, specified as a positive integer.

Example: 128

Specify atmospheric parameters — Enable atmospheric attenuation model

off (default) | on

Select this parameter to enable to add signal attenuation caused by atmospheric gases, rain, fog, or clouds. When you select this parameter, the Temperature (degrees Celsius), Dry air pressure (Pa), Water vapour density (g/m^3), Liquid water density (g/m^3), and Rain rate (mm/hr) parameters appear in the dialog box.

Data Types: Boolean

Temperature (degrees Celsius) — Ambient temperature

15 (default) | real-valued scalar

Ambient temperature, specified as a real-valued scalar. Units are in degrees Celsius.

Dependencies

To enable this parameter, select the Specify atmospheric parameters check box.

Data Types: double

Dry air pressure (Pa) — Atmospheric dry air pressure

101.325e3 (default) | positive real-valued scalar

Atmospheric dry air pressure, specified as a positive real-valued scalar. Units are in pascals (Pa). The default value of this parameter corresponds to one standard atmosphere.

Dependencies

To enable this parameter, select the Specify atmospheric parameters check box.

Data Types: double

Water vapour density (g/m^3) — Atmospheric water vapor density

7.5 (default) | positive real-valued scalar

Atmospheric water vapor density, specified as a positive real-valued scalar. Units are in g/m³.

Dependencies

To enable this parameter, select the Specify atmospheric parameters check box.

Data Types: double

Liquid water density (g/m^3) — Liquid water density

0.0 (default) | nonnegative real-valued scalar

Liquid water density of fog or clouds, specified as a nonnegative real-valued scalar. Units are in g/m³. Typical values for liquid water density are 0.05 for medium fog and 0.5 for thick fog.

Dependencies

To enable this parameter, select the Specify atmospheric parameters check box.

Data Types: double

Rain rate (mm/hr) — Rainfall rate

0.0 (default) | non-negative real-valued scalar

Rainfall rate, specified as a nonnegative real-valued scalar. Units are in mm/hr.

Dependencies

To enable this parameter, select the Specify atmospheric parameters check box.

Data Types: double

Inherit sample rate — Inherit sample rate from upstream blocks

on (default) | off

Select this parameter to inherit the sample rate from upstream blocks. Otherwise, specify the sample rate using the Sample rate (Hz) parameter.

Data Types: Boolean

Sample rate (Hz) — Sampling rate of signal

1e6 (default) | positive real-valued scalar

Specify the signal sampling rate as a positive scalar. Units are in Hz.

Dependencies

To enable this parameter, clear the Inherit sample rate check box.

Data Types: double

Ground reflection coefficient — Ground reflection coefficient

-1 (default) | complex-valued scalar | complex-valued 1-by-N row vector

Ground reflection coefficient for the field at the reflection point, specified as a complex-valued scalar or a complex-valued 1-by-N row vector. Coefficients have an absolute value less than or equal to one. The quantity N is the number of two-ray channels. Units are dimensionless.

Example: -0.5

Combine two rays at output — Option to combine two rays at output

on (default) | off

Select this parameter to combine the two rays at channel output. Combining the two rays coherently adds the line-of-sight propagated signal and the reflected path signal to form the output signal. You can use this mode when you do not need to include the directional gain of an antenna or array in your simulation.

Example: on

Maximum one-way propagation distance (m) — Maximum one-way propagation distance

10.0e3 (default) | positive real-valued scalar

Maximum one-way propagation distance, specified as a real-valued positive scalar. Units are in meters. Any signal that propagates more than the maximum one-way distance is ignored. The maximum distance must be greater than or equal to the largest position-to-position distance.

Example: 5000.0

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 run faster with generated code than in 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).

Algorithms

When the origin and destination are stationary relative to each other, the block output can be written as y(t) = x(t – τ)/L. The quantity τ is the delay and L is the propagation loss. The delay is computed from τ = R/c where R is the propagation distance and c is the propagation speed. The free space path loss is given by

$$L_{fsp}=\frac{{(4\pi R)}^2}{{\lambda }^2},$$

where λ is the signal wavelength.

This formula assumes that the target is in the far-field of the transmitting element or array. In the near-field, the free-space path loss formula is not valid and can result in losses smaller than one, equivalent to a signal gain. For this reason, the loss is set to unity for range values, R ≤ λ/4π.

When there is relative motion between the origin and destination, the processing also introduces a frequency shift. This shift corresponds to the Doppler shift between the origin and destination. The frequency shift is v/λ for one-way propagation and 2v/λ for two-way propagation. The parameter v is the relative speed of the destination with respect to the origin.

Extended Capabilities

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