In this paper, we present a new microfabricated fluxgate sensor structure having cascaded planar rings as the ferromagnetic core. A circular magnetic excitation is provided with a rod passing through the FeNi rings as a sewing thread. Planar coils placed under the edges of the core are used as sensing elements. The sensing coils and the excitation rod are made of AlSi, and the planar FeNi ferromagnetic core is electroplated in between the excitation rod metallization. The sensor with 18 cascaded cores has 623 mu V/mT sensitivity and +/- 300 mu T linear operation range for a sinusoidal current excitation at 1 MHz with 170 mA peak.