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youtube-at-vach edited this page Jul 23, 2026 · 2 revisions

Signal Analysis Modules

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MeasureLab provides a comprehensive suite of real-time and sweep-based signal analysis modules. These modules are built upon a standardized architecture that ensures consistent data handling, UI behavior, and high-performance DSP execution.

The system uses a pluggable architecture where each instrument is a subclass of MeasurementModule src/measurement_modules/base.py:4-9. This base class defines the interface for identification and GUI integration src/measurement_modules/base.py:11-28.

Measurement Module Architecture

The relationship between the core engine and specific analysis modules is illustrated below:

Module Integration Flow

graph TD
    subgraph "Core Entity Space"
        AE["AudioEngine"]
        MM["MeasurementModule (Base)"]
        AC["AudioCalc (DSP Utilities)"]
        FFTM["FFTManager"]
    end

    subgraph "Signal Analysis Modules"
        DA["DistortionAnalyzer"]
        LIA["LockInAmplifier"]
        FC["FrequencyCounter"]
        NP["NoiseProfiler"]
    end

    AE -- "Audio Callback" --> MM
    MM <|-- DA
    MM <|-- LIA
    MM <|-- FC
    MM <|-- NP
    
    DA -- "Harmonic Analysis" --> AC
    NP -- "PSD Calculation" --> FFTM
    LIA -- "Demodulation" --> AC
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Sources: src/measurement_modules/base.py:4-29, src/core/analysis.py:172-175, src/gui/widgets/distortion_analyzer.py:41-43

3.1 Spectrum and Time-Domain Analyzers

These modules provide fundamental visualization of signals in both time and frequency domains. They utilize the centralized FFTManager for optimized transforms and AudioCalc for envelope detection and windowing.

3.2 Distortion and Linearity Analyzers

Focuses on quantifying system non-linearities. The DistortionAnalyzer src/gui/widgets/distortion_analyzer.py:41 supports THD, THD+N, and SINAD using advanced sine-fitting and harmonic extraction src/gui/widgets/distortion_analyzer.py:103-195. The AdvancedDistortionMeter src/gui/widgets/advanced_distortion_meter.py:31 adds support for Multitone (MIM) and Intermodulation (PIM) tests.

  • Key Algorithms: Coherent multitone generation src/gui/widgets/advanced_distortion_meter.py:206-210, SMPTE/CCIF IMD analysis tests/logic_verification/analysis/test_imd.py:24-132.
  • For details, see Distortion and Linearity Analyzers.

3.3 Lock-in Suite

A family of high-precision detection tools based on dual-phase demodulation. The LockInAmplifier src/gui/widgets/lock_in_amplifier.py:40 extracts signal magnitude and phase even when buried in noise, utilizing an IIR post-mix LPF cascade for high dynamic reserve src/gui/widgets/lock_in_amplifier.py:79-85.

  • Key Components: LockInHarmonicAnalyzer, LockInFrequencyCounter, and LockInModeler.
  • For details, see Lock-in Suite.

3.4 Network and Impedance Analyzers

These modules characterize the transfer functions of devices. The NetworkAnalyzer produces Bode plots (Magnitude/Phase) and Group Delay, while the ImpedanceAnalyzer utilizes dual-channel lock-in detection to calculate equivalent circuits (ESR, L, C).

3.5 Nonlinear System Identification

Advanced modeling tools for nonlinear systems. They use Synchronized Swept Sine (SSS) excitation to extract Parallel Hammerstein Model (PHM) kernels.

3.6 Feedforward Compensator

Implements the Iterative LICFF (Linear-Inverse Compensated Feedforward) algorithm. It uses extracted Hammerstein kernels to pre-distort signals, effectively cancelling hardware nonlinearities.

3.7 Acoustic and Loudness Meters

A set of tools for environmental and broadcast standards. Includes the NoiseProfiler src/gui/widgets/noise_profiler.py:32 for PSD and 1/f noise analysis, and the FrequencyCounter src/gui/widgets/frequency_counter.py:122 for high-precision tracking with Allan Deviation src/gui/widgets/frequency_counter.py:82-83. The OnePPSMonitor src/gui/widgets/one_pps_monitor.py:30 provides experimental sample-clock drift monitoring.

3.8 Spatial Audio and Binaural Tools

Tools for rendering and measuring spatial audio. The HRTFPlayer src/gui/widgets/hrtf_player.py:162 loads SOFA files src/gui/widgets/hrtf_player.py:48-50 and performs real-time binaural convolution, calculating metrics like ITD and ILD src/gui/widgets/hrtf_player.py:95-116.

3.9 Utility and Auxiliary Widgets

Auxiliary tools for signal management and system benchmarking, including Recorder, BoxcarAverager, and the TransmissionAnalyzer for bit-perfect loopback tests.

Core DSP Utilities

Most modules rely on the AudioCalc static utility class for standardized DSP operations:

Function Description File Reference
resample Polyphase filtering for sample rate conversion src/core/analysis.py:195
design_a_weighting SOS coefficients for A-weighting filter tests/logic_verification/analysis/test_c_weighting_design.py:63
calculate_imd_smpte SMPTE Intermodulation Distortion analysis tests/logic_verification/analysis/test_imd.py:24
calculate_noise_profile Statistical noise characterization src/gui/widgets/noise_profiler.py:162

Sources: src/core/analysis.py:172-214, src/gui/widgets/noise_profiler.py:162, tests/logic_verification/analysis/test_imd.py:24-36

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