Behavioral Modeling System for Non-Linear Radio Frequency Transmitters


Description of Technology

To address the challenge of accurately modeling highly nonlinear systems, researchers at the University of Calgary have developed the Nonlinear Behavior Modeling System (NBMS). The NBMS is a computational environment which integrates modules that perform signal generation and acquisition, forward/reverse model identification and model validation. The NBMS supports a broad range of models suitable for characterizing nonlinear systems, including proprietary models which are particularly adept at modeling nonlinear systems with strong memory effects (see UTI Ref. #720.1).

Modern 3G and 4G wireless communications standards use wideband signals which have highly-varying envelopes. Such signals are highly susceptible to distortion introduced by a radio frequency (RF) transmitter. The undesirable consequences of transmitter distortion include impaired error vector magnitude (EVM) and increased adjacent channel power ratio (ACPR) which result in reduced system capacity (bits/s/Hz) and impaired link performance.

To achieve satisfactory performance in these networks it is usually necessary to compensate for transmitter distortion through the use of linearization techniques such as digital pre-distortion. Effective linearization requires an accurate model of the dynamic behavior of the transmitter. Unfortunately many RF components such as power amplifiers are challenging to characterize because they exhibit highly non-linear behavior and memory effects, a problem the NBMS has been designed to address.

The model validation block can use the inverse model to produce pre-distorted stimulus signals which can be injected into the device under test or a system-level design simulator to validate the model. The inverse model can also be used to design pre-distortion circuits that can be implemented in an FPGA or DSP.

The NBMS application is a complete solution for modeling non-linear systems. It interfaces with and directly controls popular vector signal generators and vector signal analyzers to provide a complete solution that integrates signal generation and acquisition with sophisticated modeling and validation processes.

Areas of Application
  • Performance optimization of 3G, 4G, and 5G radio subsytems with dynamic nonlinearities
  • Design and evaluation of linearization mechanisms including pre-distorters
  • Characterization and validation on non-communication systems incorporating nonlinear elements
Competitive Advantages
  • Complete solution integrating signal generation and acquisition, model selection and verification
    • Model identification and validation can be done in software by simply clicking a button
    • Competing solutions cannot generally process the model identification
  • Memory effects can be easily distinguished and identified
  • Supports broad range of nonlinear system models, including proprietary models unavailable elsewhere
  • Accuracy of models can be easily validated using the real system
  • Software can be applied to other nonlinear systems such as optical communication systems