AC Magnetic Field Detection of Coplanar Line Type Thin Film Magnetic Field Sensor with Optimized Narrow Slits

We have proposed coplanar line type thin-film magnetic field sensor with narrow slits. The slit is employed to flow more carrier current on the signal line by improving the impedance matching. Several sensors having 6, 10, 26, 36, and 50 μm slit widths were fabricated and evaluated from the phase and the amplitude of the transmission coefficient (S21) and reflection coefficient (S11) measured by the network analyzer. The amplitude of S21 with slit was improved about five times larger than the sensor without one at around 2 GHz. The appropriate slit width was evaluated as around 10 μm for the coplanar line type thin film magnetic field sensor and the sensitivity will enhance more than 10 times higher than the sensor without slits.

I. Introduction

In recent years, magnetic field sensors have been applied to biological application and nondestructive testing. Superconducting quantum interference device (SQUID) is known for its high sensitivity [1]. But it needs to be cooled down to -269K and measurement frequency range is narrower than other sensors [2]. Then high sensitive sensors that work at room temperature in wide measurement frequency is needed.