tclfftw - FFTW3 Tcl Extension

A Tcl extension providing a high-performance interface to the FFTW3 library for Fast Fourier Transform operations.

Features

• FFT Operations: Forward and inverse FFT transformations
• Flexible Data Access: Multiple data formats (nested lists, flat lists, integers)
• In-Place/Out-of-Place: Support for both transformation modes
• Multi-Carrier Waveform Generation: Advanced signal generation with:
  • Newman phase sequences for low PAPR
  • Frequency flatness correction
  • Sideband suppression calibration
  • Pseudorandom amplitude generation
  • Binary file output for AWG/DAC hardware

Quick Start

Installation

cd rcompile/tclfftw
autoconf
./configure
make
make install

Basic Usage

package require fftw

# Create FFT plan
set plan [fftw::plan 1024 1]

# Set input data
fftw::clear $plan
fftw::setAt $plan 0 0 {1.0 0.0}

# Execute FFT
fftw::execute $plan 0

# Get results
set output [fftw::get $plan 0]

# Cleanup
fftw::destroy $plan

Multi-Carrier Waveform Example

# Generate 5-tone signal with Newman phases
array set result [fftw::calcMcWaveform \
    -center 14250 \
    -startFreqList {14248 14249 14250 14251 14252} \
    -spacing 1.0 \
    -phaseSeed 2]

puts "RMS Power: $result(-rms) dBm"
puts "Samples: [llength $result(-pattern)]"

Documentation

Complete API documentation is available in doc/fftw.md

API Overview

Plan Management

• fftw::plan - Create FFT plan
• fftw::destroy - Destroy plan
• fftw::cleanup - Free FFTW resources

Data Operations

• fftw::set - Set multiple values
• fftw::setAt - Set single value
• fftw::get - Get values as nested lists
• fftw::getFlat - Get values as flat list
• fftw::getFlatInt - Get integer values
• fftw::getAt - Get single value
• fftw::clear - Zero all arrays

Transformations

• fftw::execute - Run FFT/IFFT
• fftw::scale - Scale output values

Waveform Generation

• fftw::calcMcWaveform - Generate multi-carrier waveforms

Running Tests

make test

All 21 tests should pass:

Tests running in interp:       D:/CM.work/tcltk86/release/bin/tclsh86.exe
all.tcl:	Total	21	Passed	21	Skipped	0	Failed	0

Requirements

• Tcl 8.6 or higher
• FFTW3 library (libfftw3-3)
• C++ compiler with C++11 support

Windows

Ensure libfftw3-3.dll is in your PATH or in the same directory as the extension.

Linux

Install FFTW3 development package:

# Debian/Ubuntu
sudo apt-get install libfftw3-dev

# RedHat/CentOS
sudo yum install fftw-devel

Version

Current Version: 3.3.4

Changelog

• 3.3.4 (2023, H. Danzer): Added -sigma parameter for pseudorandom amplitudes
• 3.3.3 (2022, H. Danzer): Minimum spacing changed to 1 Hz
• 1.0 (2010, Peter Schurek): Initial release

Authors

• Peter Schurek (Original implementation, 2010)
• H. Danzer (Enhancements, 2022-2023)

License

See LICENSE file for details.

Example Applications

Signal Processing

• Spectral analysis
• Filter design and implementation
• Convolution and correlation

RF/Microwave Engineering

• Multi-carrier signal generation
• PAPR optimization
• AWG pattern creation
• Channel simulation

Test and Measurement

• Frequency domain analysis
• Signal characterization
• Calibration data application

Support

For bugs and feature requests, please contact the maintainers or file an issue in the project repository.

References

• FFTW3: http://www.fftw.org/
• Tcl/Tk: https://www.tcl.tk/