Accelerating the pace of engineering and science

SimRF

Key Features

  • Circuit envelope simulation of multiple carrier-frequency models
  • Test bench generation from the RF Budget Analyzer app
  • General N-port models and S-parameter data files for time-domain and frequency-domain simulation
  • Passive components, including RLC elements, transmission lines, filters, switches, junctions, and general impedance blocks
  • Enhanced highly-nonlinear models of 3-port mixers and 2-port amplifiers specified by noise figure, IP2, IP3, and data files
  • Model authoring using the Simscape™ language
  • Equivalent baseband technology for discrete-time simulation of single-carrier cascaded systems

SimRF™ extends Simulink® with blocks for designing RF systems and simulating their performance, taking into account the effects of impedance mismatches, wideband spectral regrowth, and interfering and blocking signals.

Communication system model, including a direct-conversion receiver modeled with SimRF blocks.
Example of a direct-conversion receiver modeled with SimRF (center). The RF input includes the desired wideband signal and an adjacent interfering waveform (left). The constellation of the demodulated output signal (right) is recovered and shows the effects of RF imperfections in the receiver.

Wireless System Simulation Using SimRF

SimRF enables you to model and rapidly simulate RF front ends for wireless applications such as radar or communication systems.

You can use SimRF to build system-level executable specifications and perform what-if analyses with different RF front-end architectures, or you can commit to a particular architecture and use simulation to develop digital signal processing algorithms to mitigate RF impairments. With SimRF, you can refine the executable specifications of the RF subsystem while improving communication between system architects and RF or analog engineers.

By integrating SimRF models with communications algorithms you can model digitally-assisted RF systems such as those with adaptive automatic gain control (AGC) and digital pre-distortion (DPD) architectures based on feedback loops.

You can improve the accuracy of your model following a bottom-up approach by importing measurement data such as Touchstone files and AM/AM AM/PM data. You can use S-parameters in SimRF models and estimate frequency-dependent impedance mismatches between linear and nonlinear components in the time and frequency domains.

The set of RF impairments you can model in SimRF includes:

  • Thermal noise, local oscillator phase noise, and noise with colored distribution
  • Even-order and odd-order intermodulation distortion due to in-band or out-of-band signals
  • Spurious, interferer, and blocking signals
  • Image effects due to mixing products
  • Impedance mismatch, reflection, finite isolation, and leakage effects
  • Phase offsets
  • I/Q amplitude and phase mismatches
  • DC conversion and DC offset
SimRF model of the receiver from an Analog Devices AD9361 Agile Transceiver.
SimRF model of the receiver from an Analog Devices AD9361 Agile Transceiver. The RF front end is controlled by the automatic gain control (AGC) state machine. Timing aspects, RF impairments, and quantization effects from the RF front end to the digital down conversion filters are captured in this model.

Top-Down Design of RF Systems

You can build RF receivers and transmitters by connecting blocks from the SimRF component library, or you can automatically generate a SimRF model using the RF Budget Analyzer app. With the RF Budget Analyzer app you can graphically build and analyze a cascade of RF components and automatically generate a SimRF model and test bench for circuit envelope simulation.

The RF Budget Analyzer app lets you rapidly start modeling RF transmitters and receivers for wireless applications and validate simulation results in different operating conditions by comparing them with analytical predictions. You can use this app to determine the system-level specs of your RF transceiver instead of relying on custom spreadsheets and complex computations.

You can use the automatically generated model as a baseline for further elaboration of the RF architecture and for simulation effects of imperfections that cannot be accounted for analytically, such as leakage and interferers.

: Example of a receiver built and analyzed with the RF Budget Analyzer App. The automatically generated SimRF model can be simulated using the circuit envelope solver.
Example of a receiver built and analyzed with the RF Budget Analyzer App (top). The automatically generated SimRF model (bottom) can be simulated using the circuit envelope solver.

RF Simulation Technology

SimRF provides two modeling libraries for describing RF systems at different abstraction levels. Digital signal processing engineers can use the Equivalent Baseband library to estimate the impact of RF phenomena on overall system performance. RF designers can use the Circuit Envelope library to refine transceiver architectures with increased modeling fidelity.

At a higher level of abstraction, you can model a chain of RF components using blocks from the Equivalent Baseband library. You can perform budget analysis and simulations of your system, including RF impairments such as noise and odd-order nonlinearity. When you use blocks from the Equivalent Baseband library, the simulation is performed using a baseband equivalent model of the RF chain. This enables single-carrier simulation of super heterodyne transceivers, taking into account in-band spectral regrowth, noise, and impedance mismatches among blocks.

Equivalent baseband model of an RF receiver for radar applications and an example of noise link-budget analysis.

Equivalent baseband model of an RF receiver for radar applications (left) and an example of noise link-budget analysis (right). The Equivalent Baseband library provides 2-port behavioral models of RF subsystems for budget analysis and single carrier simulation.

At a lower level of abstraction, blocks from the Circuit Envelope library let you model arbitrary topologies, examine alternative architectures for your RF system, and track the effects of RF impairments through the model. When you use blocks from the Circuit Envelope library, signals in the SimRF models are represented as voltages and currents. As a result, impedance mismatch, reflection, and finite isolation are correctly taken into account.

: Example of a 16 channel receiver for wireless DVB using RF beamforming and analysis of the radiation pattern of the antenna array performed with Antenna Toolbox.

Example of a 16 channel receiver for wireless DVB using RF beamforming (left) and analysis of the radiation pattern of the antenna array (right) performed with Antenna Toolbox™. Antenna and antenna array patterns can be integrated in Simulink simulations using Phased Array System Toolbox.

RF Component Modeling

SimRF provides models of amplifiers, mixers, impedances, transmission lines, filters, and other RF components. For amplifiers and mixers, you can specify linear and nonlinear properties such as component gain, noise figure, second- and third-order intercept points (IP2 and IP3), 1dB compression point, and saturation power. With components such as power combiners, splitters, circulators, switches, and transformers you can build arbitrary RF networks based on data sheet parameters and define the system specifications following a top-down approach. Frequency dependent components enable you to evaluate the effects of impedance mismatch, reflection, finite, isolation, and leakage.

You can describe components using S-parameters and AM/AM AM/PM data. By specifying the input/output impedance of linear and non-linear components you can estimate the effect of frequency-dependent impedance mismatches on noise and power transfer.

You can author your own RF models using the Simscape language and build custom RF components. With Simscape you can model low-frequency analog electronics chains and simulate them with SimRF.

Circuit envelope model of a low-IF Hartley receiver with an interface for setting amplifier parameters and a visualization of the S-parameters of the receiver SAW filter.

Circuit envelope model of a low-IF Hartley receiver (left) and a visualization of the S-parameters of the receiver surface acoustic wave (SAW) filter (right).

RF Design of Digitally Controlled RF Transmitters and Receivers

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