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

A microwave radiometer (MWR) is an instrument used to measure the microwave power emitted from the natural origin as a brightness temperature ( T_{B} ). 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 T_{B} measurement. Although measuring T_{B} values in high-frequency resolution is an effective way to detect and remove the effect of RFI from measured T_{B} , it is difficult to fundamentally increase the number of simultaneously measurable T_{B} in the conventional MWR due to space issues. Therefore, we developed a new MWR - direct RF sampling hyperspectral microwave radiometer (DS \mu 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 \mu RAD can measure the microwave power of the vertical and horizontal polarizations to decompose each into a T_{B} spectrum from 512 MHz to 40.96 GHz at 16-MHz intervals. We expect that DS \mu 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 \mu RAD design in detail and the initial evaluation results of the instrument's performance.