Benchmarking a Commercial (Sub-)THz Focal Plane Array Against a Custom-Built Millimeter-Wave Single-Pixel Camera

Abstract

For the first time, the characteristics of an evolving commercial camera technology that can operate at millimeter-wave frequencies has been independently investigated. In this work, we benchmark the TeraSense camera against a custom-built single-pixel camera at W-band, for image quality and aperture reflectance. It is found that the Tera-1024 TeraSense camera exhibits limited image resolution and fidelity, with significant levels of systematic spatial noise. In a poor signal-to-noise ratio scenario, the addition of random noise exacerbates these problems. Possible causes of both beam and image distortion have been identified in quasi-optical applications, which gives important insight into the best use of (sub-)THz cameras and interpretation of their images. Inherent standing waves caused by the significant power reflectance of the camera aperture is investigated in detail. A simple W-band one-port quasi-optical scalar network analyzer is developed, to determine the levels of reflectance for both cameras, with its bespoke calibration routine derived from first principlesproviding a low-cost solution for many non-destructive testing applications. It is found that the TeraSense camera (with additional RAM) and single-pixel camera (having default RAM) have measured reflectance values of 27% and 3%, respectively, over a corresponding aperture area ratio of approximately 714:1. While our single-pixel camera provides excellent image resolution and fidelity, it inherently suffers from very slow raster-scanning speeds and operational bandwidth limitations. For this reason, the TeraSense camera technology is excellent for performing qualitative measurements in real time, with the caveats outlined in this paper.

Polymer-Based 3-D Printed 140-220 GHz Low-Cost Quasi-Optical Components and Integrated Subsystem Assembly

“…All electromagnetic measurements were undertaken within the Department of Electromagnetic and Electrochemical Technologies at the U.K.'s National Physical Laboratory, using their Keysight Technologies PNA-X N5247B vector network analyzerwith VDI WR-5.1 frequency extender heads [44] and the 1024 pixel TeraSense TERA-1024 (sub-)THz imaging camera [45] from Imperial College London.…”

“…To characterize the antenna beam profile within the far field, measurements are undertaken using the frequency extension heads (as a single-frequency source generator at 160 GHz) and the sub-THz imaging camera (having a peak in sensitivity at 160 GHz [45]), with its aperture located 80 cm from the antenna aperture, as shown in Fig. 14.…”

“…The TeraSense camera technology can perform qualitative measurements in real time. However, from our previous work on benchmarking this camera [45], it was found that the Tera-1024 TeraSense camera exhibits limited image resolution and fidelity, with significant levels of systematic spatial noise (due to faulty pixels and high pixel-to-pixel responsivity deviation). Moreover, it was also found that the TeraSense camera (with additional RAM) has an inherent limitation with its relatively high reflectance (e.g., 27% at 79 GHz) aperture [45].…”

“…With any focal plane array (FPA), image quality is dependent on both spatial resolution and pixel fidelity. The latter is a function of the number and distribution of pixels that are faulty and those with large deviations in responsivity [45]. The TeraSense camera has a specified permissible number of faulty pixels of up to 3% and the specified pixelto-pixel responsivity deviation from the mean value is within 20% [45].…”

“…Nevertheless, at 76 and 92 GHz, we previously showed that the spatial beam profile for a W-band rectangular horn antenna can be displayed by averaging-out pixel-related issues, using post image processing with the MATLAB 'disk smooth' filter [45]. For this reason, the same process is applied here.…”