Year: 1991
Type: article
Abstract: An extremely sensitive, accurate and simple microwave level meter has been developed. This level meter consists of a continuous wave radar in which carrier is modulated by the M-sequence (Maximal-length-sequence). Employing two M-seq. which are the same in code but generated by the slightly different clock frequencies, the implementation of the crosscorrelation between the received and the reference signals can be simple. This radar successfully gains the sensitivity and suppresses the noise. Moreover, the quantization error of this radar can be designed smaller than the conventional FMCW (Frequency-Modulated-Continuous-Wave) microwave radar. The principle of this microwave level meter is studied and its design criteria are described.This microwave level meter is useful in the case that exclusive performance in terms of sensitivity and accuracy is required for the crucial measurement conditions in the environment such as the iron and steel making process where dust and flare may make it difficult to employ the laser beam or supersonic as sensing waves. The application of the M-seq. modulated microwave level meter is discussed in the experiments measuring the metallurgical slag and the molten metal levels.In the prototype microwave level meter, the carrier frequency is 10GHz, the output power 40mW, the clock frequencies driving the two M-sequence generators about 220MHz, the difference of the two clock frequencies 5.4kHz or 10kHz, and the lengths of the M-seq. 127bit or 1, 023 bit. The water-cooled horn antennas with the gain of 17dB are used. The slag level in a mini-converter was continuously measured with the accuracy of ±88mm. The sensitivity was high enough to detect the weak reflected wave from the slag surface whose reflection coefficient was -40dB. The molten metal level in a tundish of a continuous casting process was measured with the good accuracy of ±20mm.
Authors: Akio NAGAMUNE, Kouichi TEZUKA
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2329970960