FMCW Radar
An FMCW radar emits a continuous wave whose frequency is swept over a defined band. Mixing the returned signal with a reference produces a beat frequency related to propagation delay. After calibration, peaks in the range profile can be associated with surfaces or internal interfaces.
Bandwidth sets a fundamental scale for separating echoes, but practical performance also depends on sweep linearity, phase noise, windowing and the dielectric properties of the sample. A 150 GHz architecture developed for non-destructive testing reported a dynamic range up to 100 dB and measurement rates up to 7.62 kHz. These figures describe that implementation and should remain attached to it.
Spatial imaging can be obtained by mechanical or optical beam scanning, and coherent synthetic-aperture processing can trade acquisition geometry and computation for improved lateral resolution. FMCW radar is consequently a ranging platform as much as an imaging device, with the reconstruction strategy forming part of the instrument.
Frequency-modulated continuous-wave radar for depth-resolved inspection, guided reflectometry, teaching, and application-driven demonstrators.
FMCW Radar in the terahertz measurement chain
This technology forms one part of a larger measurement chain that includes sources, detectors, optics or antennas, positioning, acquisition, calibration, and data processing. Its value depends on how well those elements are matched to the sample and to the information that must be recovered.
Performance figures must therefore be read in context. Frequency range and bandwidth affect material contrast and depth resolution; aperture and working distance affect lateral resolution; dynamic range determines which weak interfaces remain measurable; and acquisition strategy controls speed, stability, and the amount of data available to a reconstruction algorithm.
Design constraints and performance limits
Propagation, coupling losses, coherent reflections, dispersion, alignment, and calibration can dominate an experiment even when the individual components perform well. Research on this technology combines modelling and measurement so that limitations are identified rather than hidden by post-processing. The final criterion is whether the recovered quantity remains reproducible and useful for the intended scientific or application question.
Related publications
- Aeronautics composite material inspection with a terahertz time-domain spectroscopy system — DOI
- Art Painting Diagnostic Before Restoration with Terahertz and Millimeter Waves — DOI
- Terahertz frequency modulated continuous wave imaging advanced data processing for art painting analysis — DOI
- Guided Reflectometry Imaging Unit Using Millimeter Wave FMCW Radars — DOI
The study demonstrates a new generation of terahertz‑frequency radar probes that combine a frequency‑modulated continuous‑wave (FMCW) transmitter with a thin‑wall hollow‑core dielectric waveguide. By guiding the millimetre‑wave signal directly inside a polymer pipe, the device eliminates the need for large quasi‑optical components such as lenses and mirrors, simplifying the overall system layout and reducing alignment effort. Two embodiments are explored: a high‑performance III‑V based 100 GHz module and a compact, low‑cost 122 GHz silicon‑based chip. Both configurations deliver reliable distance measurements and imaging with…
- TeraPulse Lx for terahertz imaging of painting on canvas — DOI
Abstract The goal of this study was to detect and inspect the paint layers below the surface independently of any surface features. Using the for THz-TDS imaging system, we obtained contrast images of layers of paint applied to the back side of the canvas. The most difficult task that the researchers have set themselves has not yet been fully resolved. When we try to read the signatures through several layers of paint, background and canvas, we cannot get a clear image of the letters,…