High frequency signal response of impedance matched UHF carrier type head

We examined the response to a high frequency signal field of a UHF carrier type thin-film head, which employs a permeability change at UHF. The use of a core/lead/core head element with a multilayer film core and the impedance matching technique made it possible to obtain a large output, a high sensitivity, and a broad bandwidth. We achieved a sensitivity of 4 mV//spl mu/m/spl middot/Oe and a field resolution of /spl sim/10/sup -6/ Oe for a 5 MHz-signal field in the 50 /spl Omega/-matched head. In order to examine bandwidth, we proposed using a leak field from a microstripline as a constant signal field for various frequencies. A 3 dB bandwidth of >100 MHz was estimated from experiment and calculation.