Abstract
Future sub millimeter imagers are being developed with large focal plane arrays (FPAs) of lenses to increase the field of view (FoV) and the imaging speed. A full-wave electromagnetic analysis of such arrays is numerically cumbersome and time-consuming. This article presents a spectral technique based on Fourier optics combined with geometrical optics for analyzing, in reception, lens-based FPAs with wide FoVs. The technique provides a numerically efficient methodology to derive the plane wave spectrum (PWS) of a secondary quasi-optical component. This PWS is used to calculate the power received by an antenna or absorber placed at the focal region of a lens. The method is applied to maximize the scanning performance of imagers with monolithically integrated lens feeds without employing an optimization algorithm. The derived PWS can be directly used to define the lens and feed properties. The synthesized FPA achieved scan losses much lower than the ones predicted by standard formulas for horn-based FPAs. In particular, an FPA with scan loss below 1 dB while scanning up to ±17.5° (~±44 beam-widths) is presented with directivity of 52 dBi complying with the needs for future sub millimeter imagers. The technique is validated via a physical optics code with excellent agreement.
Highlights
N EW generations of imaging cameras at-millimeter wavelengths are emerging [1]–[8]
We propose the characterization of wide field of view (FoV) imagers via the derivation of their plane wave spectrum (PWS) in reception
Imaging systems at millimeter and submillimeter wavelengths are entering a new era with the development of large format arrays of detectors
Summary
N EW generations of imaging cameras at (sub)-millimeter wavelengths are emerging [1]–[8]. We extend the FO approach for QO systems with multiple components and wide-angle applications by combining it with a numerical GO-based technique in reception. DABIRONEZARE et al.: CFO MODEL FOR THE SYNTHESIS OF LARGE FORMAT LENS-BASED FPAs. Various solutions have been proposed in the past to improve the scanning performance of QO systems either using Gaussian horn feeds combined with shaped reflector or lens antennas [19]–[22] (with most of the cases over sizing the radiating aperture) and/or determining an optimum focal surface [23], [24], where the array elements are placed [17]; or by using array clusters of feeds to achieve a conjugate field match condition with the focal plane field [25]–[27].
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