phased.Transmitter
Transmitter
Description
The phased.Transmitter
System object™ models a waveform transmitter. The object supports system-level multi-channel
transmitter chain modelling including impairments such as non-linear gain, system noise, and
phase offsets.
To create a transmitter:
Create the
phased.Transmitter
object and set its properties.Call the object with arguments, as if it were a function.
To learn more about how System objects work, see What Are System Objects?
Creation
Description
creates a
transmitter System object, transm
= phased.Transmittertransm
.
creates a transmitter object, transm
= phased.Transmitter(Name
=Value
)transm
, with each specified property
Name
set to the specified Value
.
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Properties
The order that transmitter effects are applied to the signal is fixed. The following list describes the order in which effects are applied to the input signal. All properties need not be included but if they are, they will be applied in this order regardless of the order in which their properties are listed:
The input signal is scaled according to
PeakPower
property.System noise is added according to the method specified in
NoiseMethod
property.The signal gain is applied according to the method specified in
GainMethod
property. “This gain may be linear or non-linear as a function of input power.A phase offset is added to the signal according to the
PhaseOffset
property.A random phase shift is applied based on the
CoherentOnTransmit
property
Properties can be applied to N channels by specifying properties as an N-element vector. If a property is specified as a scalar, it will be expanded to match the size of vector properties. Scalars are expanded to length-N vectors containing the scalar value.
Unless otherwise indicated, properties are nontunable, which means you cannot change their
values after calling the object. Objects lock when you call them, and the
release
function unlocks them.
If a property is tunable, you can change its value at any time.
For more information on changing property values, see System Design in MATLAB Using System Objects.
PeakPower
— Transmit peak power
5000
(default) | positive scalar | length-N vector of positive values
Transmit peak power, specified as a positive scalar or length-N
vector of positive values where N is the number of channels. The
transmitted signal has a maximum input power of 1 Watt. If
PeakPower
is a scalar, the same value will be applied to all
channels. Units are in Watts.
Data Types: double
GainMethod
— Gain method
'Linear'
(default) | 'Cubic polynomial'
| 'Lookup table'
Method for applying gain to the transmitted signal, specified as
'Linear'
, 'Cubic polynomial'
or 'Lookup
table'
.
When set to
'Linear'
, a linear gain is applied.When set to
'Cubic polynomial'
, a cubic polynomial model is used to apply non-linear gain.When set to
'Lookup Table'
, a lookup table is defined to directly specify output power and phase shift as a function of input power.
Data Types: char
| string
Gain
— Gain
20
(default) | real scalar | length-N vector of real values
Linear transmitter gain, specified as a scalar or length-N vector
of real values. N is the number of channels. If
Gain
is a scalar, the same value is applied to all channels.
Units are in dB.
Dependencies
To enable this property, set the GainMethod
property to
'Linear'
or 'Cubic polynomial'
.
Data Types: single
| double
LossFactor
— Transmit loss factor
0
(default) | nonnegative scalar | length-N vector of nonnegative values
Transmit loss factor, specified as a nonnegative scalar or
length-N vector of nonnegative values. N is the
number of channels. If LossFactor
is a scalar, the same value is
applied to all channels.
Dependencies
To enable this property, set the GainMethod
property to
'Linear'
.
Data Types: double
| single
OIP3
— Output IP3
Inf
(default) | scalar | length-N vector of real values
Output third-order intercept point (OIP3). specified as a scalar or length-N vector of real values. N is the number of channels. OIP3 expresses the non-linearity of the transmitter or receiver. If OIP3 is a scalar, the same value is applied to all channels. See Nonlinearities and Noise in Idealized Baseband Amplifier Block (RF Blockset) for a detailed discussion of OIP3. Units are in dBm.
Dependencies
To enable this property, set the GainMethod
property to 'Cubic polynomial'
.
Data Types: single
| double
Table
— AM/AM-AM/PM lookup table
[-25, 5, -1; -10, 20, -2; 0, 27, 5; 5, 28,
12]
(default) | M-by-N real-valued matrix | M-by-N real-valued matrix
AM/AM-AM/PM lookup table, specified as a 3-by-M-by-N real-valued array. The lookup table specifies amplifier power characteristics. M is the number of table entries and N is the number of channels. Each row in the table expresses the relationship between output power or phase change as a function of input power. Specify AM/AM (in dB/dB) and AM/PM (in deg/dB) characteristics in a [Pin(dBm),Pout(dBm),Phase shift(degrees)]-by-M matrix or [Pin(dBm),Pout(dBm),Phase shift(degrees)]-by-M-by-N array. Use the table to linear interpolate or extrapolate power values. The column 1 input power must increase monotonically. There must be at least 3 rows in the table. The power output can be written as:
Dependencies
To enable this property, set the GainMethod
property to
'Lookup table'
.
Data Types: single
| double
NoiseMethod
— Noise method
'Noise figure'
(default) | 'None'
| 'Noise factor'
| 'Noise temperature'
Method for defining the system noise, specified as 'None'
, 'Noise figure'
, 'Noise factor'
or 'Noise temperature'
.
When set to
'None'
, no noise is applied.When set to
'Noise figure'
, theNoiseFigure
property determines the noise level.When set to
'Noise temperature'
, theNoiseTemperature
property determines the noise level.When set to
'Noise factor'
, theNoiseFactor
property determines the noise level.
The noise bandwidth is derived from the input signal sample rate.
Example: 'Noise figure'
Data Types: char
| string
NoiseFigure
— Noise figure
3
(default) | real scalar | length-N vector or real values
Transmitter noise figure, specified as a real scalar or length-N
vector of real values. N is the number of channels. If
NoiseFigure
is a scalar, the same value is applied to all
channels. Noise is generated with respect to the temperature defined by the
ReferenceTemperature
property.
Dependencies
To enable this property, set the NoiseMethod
to
'NoiseFigure'
.
Data Types: single
| double
NoiseFactor
— Noise factor
2
(default) | positive scalar | length-N vector of positive values
Transmitter noise factor, specified as a positive scalar or
length-N vector of positive values. N is the
number of channels. If NoiseFactor
is a scalar, the same value is
applied to all channels. Noise is generated with respect to the temperature defined by
the ReferenceTemperature
property.
Dependencies
To enable this property, set the NoiseMethod
property to
'Noise factor'
.
Data Types: single
| double
NoiseTemperature
— Equivalent noise temperature
290
(default) | positive scalar | length-N vector of positive values
Equivalent noise temperature, specified as a positive scalar or length-N vector of positive values. N is the number of channels. If NoiseTemperature
is a scalar, the same value is applied to all channels. Units are in K.
Dependencies
To enable this property, set the NoiseMethod
to 'Noise temperature'
.
Data Types: single
| double
ReferenceTemperature
— Reference temperature
290
(default) | positive scalar | length-N vector of positive values
Reference temperature, specified as a positive scalar or a length-N vector of positive values. N is the number of channels. If ReferenceTemperature
is a scalar, the same value is applied to all channels.
Dependencies
To enable this property, set the NoiseMethod
property to 'Noise figure'
or 'Noise factor'
.
Data Types: single
| double
SampleRate
— Sample rate
1e6
(default) | positive scalar
Sample rate of the input signal, specified as a positive scalar. Use this property to add noise to the signal. The SampleRate
is only used to derive the noise bandwidth of the signal.
Dependencies
To enable this property, set the AddInputNoise
property to true
or set the NoiseMethod
property to 'Noise figure'
, 'Noise factor'
, or 'Noise temperature'
.
Data Types: single
| double
PhaseOffset
— Phase offset
0
(default) | scalar | length-N vector of real values
Phase offset, specified as a real scalar or length-N vector of real values. N is the number of channels. If PhaseOffset
is a scalar, the same value is applied to all channels. Units are in degrees.
Data Types: single
| double
InUseOutputPort
— Enable transmitter status output
false
(default) | true
To obtain the transmitter in-use status for each output sample, set this property to
true
and use the corresponding output argument of the object
function. In this case, 1's indicate the transmitter is on and 0's indicate the
transmitter is off. If you do not want to obtain the transmitter in-use status, set this
property to false
.
Data Types: logical
CoherentOnTransmit
— Preserve coherence among pulses
true
(default) | false
Specify whether to preserve coherence among transmitted pulses. When you set this
property to true
, the transmitter does not introduce any random phase
to the output pulses. When you set this property to false
, the
transmitter adds a random phase noise to each transmitted pulse. The random phase noise
is introduced by multiplication of the pulse by
ejϕwhere ϕ is a uniform random variable
on the interval [0,2π].
Data Types: logical
PhaseNoiseOutputPort
— Enable pulse phase noise output
false
(default) | true
To obtain the introduced transmitter random phase noise for each output sample, set
this property to true
and use the corresponding output argument of
the object function. You can use in the receiver to simulate-coherent-on receive
systems. If you do not want to obtain the random phase noise, set this property to
false
.
Dependencies
To enable this property, set the CoherentOnTransmit
property
to false
.
Data Types: logical
SeedSource
— Source of seed for random number generator
'Auto'
(default) | 'Property'
'Auto' | The default MATLAB® random number generator produces the
random numbers. Use 'Auto' if you are using this
object with Parallel Computing Toolbox™ software. |
'Property' | The object uses its own private random number generator to
produce random numbers. The Seed property of
this object specifies the seed of the random number generator. Use 'Property' if
you want repeatable results and are not using this object with Parallel Computing Toolbox software. |
Dependencies
To enable this property, set the CoherentOnTransmit
property
to false
or specify that the NoiseMethod
is
not set to a value other than 'None'
. To use this object with the
Parallel Computing Toolbox, set this property to 'Auto'
.
Data Types: char
| string
Seed
— Random number generator seed
0
(default) | nonnegative integer between 0
and
232–1
Random number generator seed, specified as a nonnegative integer between 0 and 232–1.
Dependencies
To enable this property, set the CoherentOnTransmit
property
to false
, set the SeedSource
property to
'Property'
, and set the NoiseMethod
property to 'None'
.
Data Types: double
| single
Usage
Description
Input Arguments
X
— Transmitter Input signal voltage
complex-valued vector | complex-valued matrix
Transmitter Input signal voltage, specified as a complex-valued vector or complex-valued matrix. The number of rows is equal to the number of samples.
If X
is a vector, the number of rows in
Y
equals the number of rows in X
.The
number of columns in Y
equals the number of channels in the
receiver.
In the case where X
is a vector, the number of channels is
determined by the active properties that indicate a channel number, such as
NoiseFigure
, ReferenceTemperature
,
Gain
, PhaseOffset
, etc.
Receiver effects are applied to the signal in a fixed order although some effects can be omitted. The order in which effects are applied to the input signal:
Input noise is added according to the
AddInputNoise
property.System noise is added according to the method specified in
NoiseMethod
property.Signal gain is applied according to the method specified in the
GainMethod
property.Phase offset is added to the signal according to
PhaseOffset
.
Data Types: single
| double
Complex Number Support: Yes
Output Arguments
Y
— Transmitter output signal voltage
same dimension as X
Transmitter output signal voltage, returned as a complex-valued vector or
complex-valued matrix. If X
is a matrix, the size of
Y
is equal to the size of X
. The
transformation is based on transmitter characteristics, such as the gain,
nonlinearity, and noise. Power is calculated from signal voltage assuming a reference
impedance of 1 Ohm.
Data Types: single
| double
Complex Number Support: Yes
TR
— on/off status
logical vector
On/off status of the transmitter, returned as false
or
true
.TR
is a logical vector where
true
indicates the transmitter is on for the corresponding sample
time, and false
indicates the transmitter is off. TR is a logical
matrix with the same size as the input X
argument.
Dependencies
To enable this argument, set the InUseOutputPort
property
is true
.
PHNOISE
— Random phase noise
complex-valued vector | complex-valued matrix
Random phased noise, returned as complex-valued vector or complex-valued matrix.
PHNOISE
is the random phase noise added to each transmitted
sample when the CoherentOnTransmit
property is
false
and the PhaseNoiseOutputPort
property
is true
. PHNOISE
is a vector having the same
size as Y
. Each element in PHNOISE
contains
the random phase between 0 and 2*pi, added to the corresponding sample in
Y
by the transmitter.
Object Functions
To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named obj
, use
this syntax:
release(obj)
Specific to phased.Transmitter
viewGain | Plot output transmitter power or output phase shift as a function of input transmitter power |
Examples
Transmit LFM Pulse
Transmit a pulse containing a linear FM waveform with a bandwidth of 5 MHz and a sample rate of 10 MHz.
fs = 1e7;
waveform = phased.LinearFMWaveform(SampleRate=fs, ...
PulseWidth=1e-5,SweepBandwidth=5e6);
x = waveform();
transmitter = phased.Transmitter(PeakPower=5e3);
y = transmitter(x);
Three-Channel Transmitter for LFM Pulse
Transmit a pulse containing a linear FM waveform. The transmitter has three channels with different gains, OIP3 values, and phase offsets.
First, create an LFM waveform. The sample rate is 10 MHz, the pulse width is 10 microseconds, and the sweep bandwidth is 5 MHz.
fs = 10e6; waveform = phased.LinearFMWaveform('SampleRate',fs, ... 'PulseWidth',1e-5,'SweepBandwidth',5e6); x = waveform();
Transmit the waveform over three channels..
tx = phased.Transmitter(GainMethod="Cubic polynomial", ... Gain=[19,21,25],OIP3=[11,32,29],PhaseOffset=[0,30,45]); y = tx(x);
Display gains for each channel.
viewGain(tx,'ChannelIndex',1,'Parent',gca); hold on viewGain(tx,'ChannelIndex',2,'Parent',gca); viewGain(tx,'ChannelIndex',3,'Parent',gca); legend('Channel 1, Gain = 19','Channel 2, Gain = 21','Channel 3, Gain = 25', ... 'Location','SouthEast') hold off
Algorithms
OIP3
Cubic polynomials can be used to model nonlinear amplifier power gain. The general form of the cubic nonlinear AM-AM amplifier is characterized by
where u is the input power and
FAM-AM(u) is the output
power. c1 represents the linear gain in the
Gain
property.
and OIP3 is the third-order intercept point specified by the
OIP3
property.
Lookup Table
A lookup table expresses the relationship between output power or phase change as a function of input power at discrete points. The table contains values for TAM-AM and TAM-PM. The output power is derived by linear interpolation or extrapolation of
between these values.
References
[1] Edde, B. Radar: Principles, Technology, Applications. Englewood Cliffs, NJ: Prentice Hall, 1993.
[2] Richards, M. A. Fundamentals of Radar Signal Processing. New York: McGraw-Hill, 2005.
[3] Skolnik, M. Introduction to Radar Systems, 3rd Ed. New York: McGraw-Hill, 2001.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
See System Objects in MATLAB Code Generation (MATLAB Coder).
Version History
Introduced in R2011aR2022a: Transmitter Impairments
The System object lets you create multichannel data that incorporates impairments such as gain nonlinearities, signal noise, phase offsets, and random phase shifts.
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