Direct RF Sampling Hyperspectral Microwave Radiometer (DSμRAD) for Ground Use

• Published in: IEEE geoscience and remote sensing letters Vol. 18; no. 6; pp. 1084 - 1088
• Main Authors: Maeda, Takashi, Kawaguchi, Noriyuki, Harada, Ken-Ichi, Ozeki, Kensuke, Chikahiro, Yuichi, Onuki, Hirofumi, Hayashi, Yoshinori, Ema, Kenji, Naoki, Kazuhiro, Nakayama, Masashige, Takano, Tadashi
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.06.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: <italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Y -factor method; Antialiasing filter (AAF); Brightness temperature; Communication; Converters; Extremely high frequencies; flash A/D converter (ADC); Frequency measurement; Horizontal polarization; Microwave antennas; Microwave communication; Microwave measurement; Microwave oscillators; Microwave radiation; Microwave radiometers; Microwave radiometry; Microwaves; quad-ridged feed horn (QRFH); Radio frequency; Radio frequency interference; Radiometers; Remote sensing; Sampling; Surface radiation temperature; ultrawide bandwidth; Ultrawideband; Vertical polarization; Wireless communications
• ISSN: 1545-598X; 1558-0571
• DOI: 10.1109/LGRS.2020.2990707

A microwave radiometer (MWR) is an instrument used to measure the microwave power emitted from the natural origin as a brightness temperature (<inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula>). A more active use of microwaves below the Ka-band is being planned for wireless communication in the near future, thereby increasing the risk of artificial radio frequency interference (RFI) with natural origin <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula> measurement. Although measuring <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula> values in high-frequency resolution is an effective way to detect and remove the effect of RFI from measured <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula>, it is difficult to fundamentally increase the number of simultaneously measurable <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula> in the conventional MWR due to space issues. Therefore, we developed a new MWR - direct RF sampling hyperspectral microwave radiometer (DS<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>RAD) that adopts multiple A/D converters of 10-GSPS order [samples per second (SPS)] to digitize microwave power received by an ultrawideband antenna. DS<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>RAD can measure the microwave power of the vertical and horizontal polarizations to decompose each into a <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula> spectrum from 512 MHz to 40.96 GHz at 16-MHz intervals. We expect that DS<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>RAD will open up new possibilities for microwave remote sensing, including a drastic response to increased RFI risk, i.e., effective detection and removal (or extraction) of RFI. This letter presents the DS<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>RAD design in detail and the initial evaluation results of the instrument's performance.