High precision waterlevel gauge with an FMCW radar under limited bandwidth

Limitation of bandwidth, which is requested by the regulation for license-free radio systems, is a serious drawback for the ranging accuracy of a radar system. Nonetheless, a license-free radar application is favorable to users because of the easiness of adoption. In Japan, for example, available bandwidth is regulated within 76 MHz, which implies the range resolution cannot be less than 197 cm. Under such bandwidth limitation, an excellent S/N is required for an accurate ranging. We have developed a radar waterlevel gauge, which meets the bandwidth regulation and achieves a few centimeters in accuracy.