SimRF

Key Features

  • Circuit envelope solver for multiple carrier-frequency simulation
  • Arbitrary network descriptions, enabling N-port block modeling and intra-model signal probing
  • S-parameter data files for time-domain and frequency-domain simulations
  • Passive components, including resistors, capacitors, inductors, transmission lines, and general impedance blocks
  • 3-port mixer and 2-port amplifier models specified by noise figure, IP2, IP3, P1dB, and Psat
  • Equivalent Baseband library for discrete-time simulation of single-carrier cascaded systems

SimRF works with Simscape™ to simulate the performance of the RF system defined by the block diagram. Gateways to Simulink® enable signal generation and analysis features found in Communications System Toolbox™ and DSP System Toolbox™, respectively.

Communication system model, including a direct-conversion receiver modeled with SimRF blocks.
Communication system model (top right), including a direct-conversion receiver modeled with SimRF blocks (bottom left), a spectrum scope display of the input signal and interfering waveforms (top left), and constellation diagram of the demodulated output waveform (bottom right). SimRF integrates with Communications System Toolbox and DSP System Toolbox to simulate the effects of RF architectures on system performance.

Defining RF Components

SimRF lets you represent RF amplifiers, mixers, impedances, transmission lines, and filters by specifying physical properties. For amplifiers and mixers, you can specify linear and nonlinear properties such as component gain, noise figure, IP2 and IP3, 1dB compression point, and saturation power. You can also specify linear networks by importing S-parameter data files directly into SimRF models. You can simulate frequency-dependent mismatches between linear and nonlinear components in the time and frequency domains. You can author your own RF models using the Simscape language.

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 (top) with an interface for setting parameters of the amplifier (bottom left) and a visualization of the S-parameters of the receiver SAW filter (bottom right).

SimRF blocks are defined by linear and nonlinear specifications, noise figure, and industry-standard Touchstone data files. For time-domain simulation, SimRF applies a general rational function model to the measured S-parameters. The S-Parameters block lets you plot the data and the result of the rational fitting.

Designing RF Subsystems

You can build RF receivers and transmitters by connecting blocks from the SimRF libraries. SimRF provides two modeling libraries for describing RF systems at different abstraction levels. The Equivalent Baseband library is suitable for digital signal processing engineers to estimate the impact of RF phenomena on the overall system performances. RF designers use the Circuit Envelope library to refine transceiver architectures with increased modeling fidelity.

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 the RF impairments.

With SimRF, you can refine the executable specifications of the RF subsystem by adopting a top-down design methodology. This improves the communication between system architects and RF or analog engineers.

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 link-budget analysis, and frequency-selective components are described in terms of lumped and distributed elements or S-parameter files.
Detail of an RF beamforming receiver architecture for a home digital audio broadcasting system using blocks from the Circuit Envelope library.
Detail of an RF beamforming receiver architecture (bottom right) for a home digital audio broadcasting system (top left) using blocks from the Circuit Envelope library.

The circuit envelope solver enables the simulation of networks with arbitrary topologies. In the illustration, N-port S-parameter blocks are used to model 3-port combiners. These blocks read standard Touchstone .snp files containing measured or simulated component data.

Simulating Wireless Systems Using SimRF

At a higher level of abstraction, you can model a chain of RF components using blocks from the Equivalent Baseband library. You can perform link-budget analysis and simulation of your system, including RF impairments such as noise and odd-order nonlinearity.

If 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.

At a lower level of abstraction, blocks from the Circuit Envelope library let you model arbitrary topologies and examine alternative architectures for your RF system. The probing capabilities of SimRF enable you to track the effects of the RF impairments through the model.

If you use blocks from the Circuit Envelope library, the signals in these SimRF models are represented as voltages and currents. You can generate signals in Simulink and pass them to SimRF using the input port, or generate them using SimRF sources. Each signal is associated with a carrier frequency. The set of all carrier frequencies simulated in a SimRF model is defined in the Configuration block. To capture the relevant spectral content of the signals, you can select the total number of harmonics used for simulation, or the solver can determine it automatically.

SimRF integrates with Simscape for modeling the low-frequency analog electronics chain.

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

  • Noise
  • Even-order and odd-order intermodulation distortion due to in-band or out-of-band signals
  • Spurious signals
  • Image effects due to mixing products
  • Phase offsets
  • I/Q mismatches
  • DC conversion
  • DC offset
  • Local oscillator phase noise
Circuit envelope model of a low-IF receiver, including an active analog polyphase filter modeled in Simscape.
Circuit envelope model of a low-IF receiver, including an active analog polyphase filter modeled in Simscape. Impairments analyzed in this model include interference, even-order and odd-order intermodulation distortion, image effects, I/Q mismatches, and local oscillator phase noise.

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Design and Verify RF Transceivers for Wireless Communication

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