Magnetoresistive power sensor for measurement "in situ" of RF power absorbed by tissue

A new magnetoresistive sensor for its use in medicine apparatus of RF heating and hyperthermia is present. This sensor has DC output signal which is proportional to RF power absorbed in tissue. The operating principle of the sensor consists of multiplication of the instantaneous value of the RF current and voltage in a microstrip transmission line by using the special constructed magnetoresistive element. At an operating frequency 915 MHz in a 20% bandwidth it has a sensitivity of 22 μV/W, insertion losses less than 0.1 dB and no linearity less than 3% up to 300 Watts. The uncertainties caused by the reflected waves with arbitrary phase are less than 3.5% up to VSWR=3.