Methods and systems for monitoring blood pressure in a person are disclosed. A method for monitoring a blood pressure in a person involves transmitting millimeter range radio waves over a three-dimensional (3D) space below the skin surface of a person, receiving radio waves on multiple receive antennas, the received radio waves including a reflected portion of the transmitted radio waves that is reflected by blood in a blood vessel in the 3D space, isolating a signal that corresponds to the portion of the transmitted radio waves that is reflected by blood in the blood vessel in response to receiving the radio waves on the multiple receive antennas, and outputting a signal that corresponds to a blood pressure level in the person in response to the isolated signal.