Log-periodic temporal apertures for grating lobe suppression in k-space tomography

Area of Science:

• Electromagnetic Wave Propagation
• Optical Engineering
• Signal Processing

Background:

• Millimeter-wave (mmW) imaging receivers utilize phased antenna arrays and photonic up-conversion for radio-frequency (RF) wave imaging.
• K-space tomography extends mmW imaging to 3D sensing by incorporating frequency detection and a temporal aperture (arrayed waveguide grating).
• Existing k-space tomography systems face limitations due to grating lobes, restricting the spatial-spectral monitoring of RF sources.

Purpose of the Study:

• To address the limitations of grating lobes in k-space tomography for 3D RF sensing.
• To enhance the free spectral range (FSR) of the temporal aperture in mmW imaging systems.
• To enable improved spatial-spectral monitoring of RF sources.

Main Methods:

• Implementation of an arrayed waveguide grating as a temporal aperture for spectral beam-forming.
• Application of tomographic algorithms to reconstruct RF signal power distribution from 3D phase information.
• Introduction of non-uniform log-periodic array sampling for the k-space tomographic time-delay based aperture.

Main Results:

• The non-uniform log-periodic array sampling significantly increases the free spectral range of the system.
• This sampling strategy effectively mitigates grating artifacts that limit the field of regard.
• The number of system channels is maintained while enhancing the spatial-spectral monitoring capabilities.

Conclusions:

• Non-uniform log-periodic array sampling is a viable method to overcome limitations in k-space tomography for mmW imaging.
• This technique improves the performance of 3D RF sensing systems by expanding the FSR and reducing artifacts.
• The proposed method offers a pathway to more comprehensive spatial-spectral monitoring of RF environments.