Wideband Two-Ray Channel
Broadband dual beam propagation channel.
Description
The Wideband Two-Ray Channel block represents a broadband two-beam propagation channel, modelling both a direct reflected beam and a beam re-reflected from the earth’s surface. The block generates broadband signals by decomposing them into sub-bands, simulates their independent propagation and recombines the propagated sub-bands. The block models propagation time, Doppler shift and propagation loss. The block assumes that the propagation velocity is much greater than the object velocity, in which case the stop-and-hop model is valid.
Ports
Input
X - wideband input signal
complex matrix M by N | complex matrix M by 2N
A broadband unpolarised scalar signal given as:
-
``Complex matrix M over N''. M is the number of samples of the signal and N is the number of two beam channels. Each channel corresponds to a source-destination pair. Each column contains an identical signal propagating along the line of sight and along the reflected path.
-
``Complex matrix M by 2N''. M is the number of signal samples, N is the number of two-beam channels. Each channel corresponds to a source-destination pair. Each adjacent pair of columns represents a separate channel. In each pair, the first column represents the signal propagating along the line-of-sight path and the second column represents the reflected path.
*Example: [1,1;j,1;0.5,0]
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Support for complex numbers: Yes
Pos1 is the position of the signal source
valid column vector 3 by 1 | valid matrix 3 by N
The position of the signal source or signals given as a valid vector-column 3 by 1 or a valid matrix 3 by N. N is the number of two-beam channels. If Pos1 is a column vector, it takes the form . If Pos1 is a matrix, each column specifies a different signal source and takes the form .
At least one of the ports of Pos1 and Pos2 must be a 3 by 1 column vector.
*Example: [1000;100;500]
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Pos2 - position of the signal destination location
valid column vector 3 by 1 | valid matrix 3 by N
The position of the irradiated point (target) of the space given as a valid vector-column 3 by 1 or a valid matrix 3 by N. N is the number of dual beam channels.
If Pos2 is a column vector, it takes the form . If Pos2 is a matrix, each column specifies a different signal destination and takes the form .
At least one of the Pos1 and Pos2 ports must be a 3 by 1 column vector.
*Example: [-100;300;50]
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
Vel1 - velocity of the signal source
valid column vector 3 by 1 | valid matrix 3 by N
The velocity of the signal source as a valid vector-column 3 by 1 or a valid matrix 3 by N. N is the number of two-beam channels. The dimensions of Vel1 must match the dimensions of Pos1.
If Vel1 is a column vector, it takes the form . If Vel1 is a matrix, each column specifies a different signal onset rate and takes the form .
*Example: [-10;3;5]
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64
*Vel2` is the velocity of the signal destination
valid column vector 3 by 1 | valid matrix 3 by N
The velocity of the irradiated point (target) space as a valid vector-column 3 by 1 or a valid matrix 3 by N. N is the number of two-beam channels. The dimensions of Vel2 must coincide with the dimensions of Pos2.
If Vel2 is a column vector, it takes the form . If Vel2 is a matrix, each column specifies a different signal destination velocity and takes the form .
*Example: [-1000;300;550]
Output
Out - propagated signal
complex matrix M over N | complex matrix M over 2N
-
Complex matrix M over N. To return this format, set theCombinedRaysOutputproperty totrue. Each column of the matrix contains a coherently combined direct and re-reflected ray. -
Combined matrix M by 2N. To return this format, set theCombinedRaysOutputproperty tofalse. The alternating columns of the matrix contain the direct and the re-reflected ray.
The Out output contains the signals reflected to the source location during the current time interval. If the signal propagation from source to target takes longer than the current time interval, the output may not contain all the data from the input in the current time interval. The remaining data will appear the next time the block is executed.
Parameters
Signal propagation speed - signal propagation speed, m/c
3e8 (by default) | positive scalar
Signal propagation speed as a real positive scalar. By default, the value of the speed of light is 3e8 m/c.
The unit of measurement is metres per second.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Signal carrier frequency (Hz) - carrier frequency of the signal
3e8 (By default) | positive scalar
The carrier frequency of the signal as a positive real scalar.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Specify atmospheric parameters - atmospheric attenuation model
Off (by default) | `On
Select this checkbox to add signal attenuation caused by atmospheric gases, rain, fog or clouds.
When selected, the parameters Temperature (degrees Celsius), Dry air pressure (Pa), Water vapour density (g/m^3), Liquid water density (g/m^3), and Rain rate (mm/hr) appear in the dialogue box.
Temperature (degrees Celsius) is the ambient temperature
15 (By default).
Ambient temperature specified as a real scalar.
Dependencies
To use this parameter, select the Specify atmospheric parameters checkbox.
Dry air pressure (Pa) is the atmospheric pressure of dry air
101.325e3 (By default).
Dry air atmospheric pressure, specified as a positive real scalar.
The value of this parameter by default corresponds to one standard atmosphere.
Dependencies
To use this parameter, select the Specify atmospheric parameters checkbox.
Water vapour density (g/m^3) is the density of water vapour in the atmosphere
`7.5 (By default).
The density of water vapour in the atmosphere, given as a positive real scalar.
Dependencies
To use this parameter, select the Specify atmospheric parameters checkbox.
Liquid water density (g/m^3) - liquid water density
`0.0 (By default).
The density of liquid water in fog or clouds, given as a non-negative real-valued scalar. Typical values of liquid water density are 0.05 for medium fog and 0.5 for dense fog.
Dependencies
To use this parameter, select the Specify atmospheric parameters checkbox.
Rain rate (mm/hr) - precipitation rate
`0.0 (By default).
Precipitation rate specified as a non-negative real scalar.
Dependencies
To use this parameter, select the Specify atmospheric parameters checkbox.
Inherit sample rate - inherit sample rate
On (By default) | Off.
Select the checkbox to inherit sample rate from upstream blocks. Otherwise, set the sample rate using the Sample rate (Hz) parameters.
Sample rate (Hz) - sampling rate
1e6 (By default) | Positive scalar
The sampling frequency of the signal as a positive scalar. The unit of measurement is Hz.
Dependencies
To use this parameters, clear the Inherit sample rate checkbox.
Ground reflection coefficient - ground reflection coefficient
`-1 (By default).
The ground reflection coefficient for the field at the reflection point, given as a complex scalar or complex vector-string 1 over N. Coefficients have an absolute value less than or equal to one. N is the number of dual-beam channels.
Combine two rays at output - switch off data combining at output
On (By default) | Off
Select the checkbox to combine two rays at channel output. Two-beam combining coherently adds the propagated line-of-sight signal and the reflected signal to form the output signal. This mode can be used when the antenna or array gain is not required to be considered in the simulation.
Maximum one-way propagation distance (m) - maximum one-way propagation distance
`10e3 (By default)
The maximum distance in metres between the starting point and the destination as a positive scalar quantity. The amplitudes of any signals that propagate beyond this distance will be set to zero.
Algorithms
Propagation delay, Doppler shift and path loss in free space
When the source and target are stationary relative to each other, the block output can be written as . The value represents the delay and represents the propagation loss. The delay is calculated from , where is the propagation distance and is the propagation velocity. The free-space path loss is defined by the expression
where is the wavelength of the signal.
This formula assumes that the target is in the far zone of the transmitting element or array. In the near zone, the free-space propagation path loss formula is invalid and may result in a loss less than unity, which is equivalent to signal gain. For this reason, the loss is set equal to unity for range values .
When there is relative motion between source and target, processing also introduces a frequency shift. This shift corresponds to the Doppler shift between the source and target points. The frequency shift is for one-way propagation and for two-way propagation. The parameters is the relative velocity of the target relative to the source.