I have a very large and complex SimRF model. When I simulate my model, it takes a very long time to run. I would like to know how I can speed up the execution time of my model.
MATLAB: How to reduce the simulation time of the model in SimRF 4.0 (R2013a)
RF Blockset
Related Solutions
The two modeling techniques available in SimRF, Equivalent Baseband (EBB) and Circuit Envelope (CE), are two different approaches to solving the problem of high Nyquist sampling requirements for RF systems (since RF systems typically involve signals in the MHz-GHz range). Since the underlying modeling techniques used by EBB and CE are fundamentally different, the two types of blocks cannot be mixed with one another. An overview of these two techniques (and the differences between them) is as follows:
Equivalent Baseband:
An EBB model implements the following procedure during simulation:
1) Determine the RF Circuit based on the blocks in the model
2) Find the passband transfer function frequency response of the model
3) Find a transfer function that represents the same frequency response centered around 0Hz (baseband)
4) Derive an equivalent Finite Impulse Response (FIR) filter representation of the baseband transfer function.
These steps are illustrated in the figure below:
For more information on EBB modeling, please see the following link:
Circuit Envelope:
Rather than simulating the full passband carrier wave, CE only simulates the amplitude modulated outline of the carrier wave, as shown in the figure below. This reduces the sampling rate requirement to only 2*BandWidth_Envelope:
For more information on CE modeling, please see the following link:
http://www.mathworks.com/help/releases/R2013a/simrf/gs/minimize-computations-for-rf-simulations.html
Differences between EBB and CE:
There are various trade-offs when choosing between the two modeling approaches. Please see the table below for more information:
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:
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