RF Interference Cancellation for Microwave Thermometry

This paper presents a method for cancelling external interference in a passive medical sensor for internal body temperature measurements. In microwave thermometry, a radiometric receiver measures the black-body radiation emitted by tissues inside the body. At room temperature and with a few tens of MHz bandwidth, black body radiation has a power around -100 dBm. With such low signal strengths, any transmitter (intentional or not) in the environment becomes a source of RFI. To reduce error in radiometric measurements, a simple and computationally inexpensive method for interference cancellation based on an auxiliary antenna and receiver is presented. Using this technique, temperature fluctuations due to RFI are significantly improved, which have a standard deviation in the error temperature of 3.5K and max of 56 K, down to 0.38K and a max of 2K.