I would like to know how I can use SimRF together with Simulink, Communication Systems Toolbox, and the RF Toolbox.
MATLAB: How to interface SimRF 4.0 (R2013a) with other toolboxes
multidomainRF Blockset
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There are several methods by which it may be possible to model a custom RF component in SimRF:
1) Use some combination of existing blocks:
Can the component be represented as some equivalent circuit that can be expressed in terms of the blocks in the SimRF library? If so, then the component can be modeled using some combination of the existing blocks.
The custom component model can be converted to a subsystem, or imported as a model reference or library block in some larger model. For a list of the blocks that are available in SimRF, please see the following links:
2) Represent the component using the RF Toolbox:
In RF Toolbox, it is possible to create data objects to represent circuit elements including amplifiers, mixers, S-parameter networks, and other generalized circuit elements. In general, S-parameters and amplifier/mixer data can be represented as RFDATA objects, and generalized circuit networks such as RLC networks can be represented as RFCKT objects. In turn, some of the blocks in the Equivalent Baseband Library offer the ability to import these RF Toolbox objects to define the block parameters.
If the component can be represented as an equivalent circuit in terms of the circuit elements available in the RF Toolbox, then the component can be created in RF Toolbox and imported into SimRF using the technique outlined above.
For more information on the RF Toolbox modeling objects, please see the following link:
3) Represent the component as equivalent S-parameters:
Is S-parameter data available for the component of interest? If so, then the data can be imported using one of the S-parameter blocks that are available in the SimRF library. For more information on the S-parameter blocks available in SimRF, please see the following links:
4) Interfacing SimRF with Simulink:
SimRF offers blocks that can be used to interface signals back and forth between Simulink and SimRF. Using these blocks, it may be possible to model an RF component as follows:
- Export the RF signal to the Simulink domain
- Use Simulink blocks to process the signal in some way
- Import the signal back into SimRF
Simulink has a very large variety of blocks available that may be used to process the signal in some desired manner. In addition, Simulink also has access to custom blocks such as S-functions that can be used to implement arbitrary functionality.
Simulink blocks cannot model circuit loading effects (because signals in Simulink propagate in one direction only). To model the loading effects of the custom element on the rest of the SimRF model, you can include input and output impedances before and after the Simulink blocks, as shown in the figure below:
Please use caution when importing/exporting signals between SimRF and Simulink. It is important to keep track of how SimRF signals map to the Simulink domain, and vice versa. The mapping is different for Equivalent Baseband and Circuit Envelope modeling. For more information, please see the following links:
For Simulink signals, we assume by default the nominal 1 ohm impedance used by communication engineers (see attached example) where signal amplitudes are represented as binary numbers in DSP or FPGA implementation.
amp_qam16_with_powerhead.mdl
However, RF Blockset physical blockset supports more physically based impedances. For a full explanation of how the Input Port and Output blocks acts a gateway between nominal 1 ohm Simulink signals and physically based impedances, please see section "Key Blockset Concepts -> Interpretation of Simulink Signals" in the RF Blockset documentation.
If another impedance is desired, the best practice is to define a constant in the Base Workspace (MATLAB variable) by executing the following
Z0 = 50 % ohms
or in the Model Workspace ( define a Simulink parameter) and use that as a parameter in all amplitude settings in the source blocks. See attached example where this is illustrated:power_examples.mdl
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