M-Sequence Modulated Microwave Level Meter and Its Application

Abstract

A high-resolution version of the M-sequence modulated microwave level meter has been developed. This level meter consists of a continuous wave radar where the 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 cross-correlation between the received and the reference signals can be simple, and high sensitivity and accuracy can be obtained. Moreover, using high resolution M-sequence which is a three-valued random signal in stead of the conventional two-valued M-sequence, a high resolution in tearms of range is obtained and it becomes easy to distinguish the desired signal and unwanted signals which may be receiving and transmitting anntena leakage or reflection from walls nearby.
Due to the improvement of resolution of the level meter, its application has been widely ranged for iron and steel making process. Covering a level measurement of the molten iron in a moving ladle, a molten steel level meter in a tundish of the Horizontal Continuous Casting (HCC), and foamed slag level measurement in a converter, the effectiveness of the sophisticated level meter is confirmed.