We have implemented a fully integrated CMOS magnetic spectrometer that can detect, quantify, and characterize magnetic materials from 1.1 to 3.3GHz frequency range. Frequency responses of various magnetic beads are measured and magnetic multiplexing capability is demonstrated with a mixture of two different kinds of 1μm sized beads for the first time. The sensor consumes less than 2mW, requires no external biasing magnetic fields, and can be powered and operated completely from a USB interface.