Sensor

A sensor for estimating a total number of living bodies, the sensor comprising:

• a complex transfer function calculator which calculates a complex transfer function from reception signals obtained by receiving, by M reception antenna elements in a predetermined period, signals transmitted from a transmitter including N transmission antenna elements to a predetermined space, M being a natural number greater than or equal to 2, N being a natural number greater than or equal to 2;
• a biological component extractor which extracts biological information that is a component corresponding to a living body possibly present in the predetermined space;
• a correlation matrix calculator which calculates a correlation matrix from the biological information extracted by the biological component extractor;
• a first number information calculator which calculates first number information that is a hypothesis of a total number of persons present in the predetermined space;
• a likelihood spectrum calculator which estimates a candidate of a position of the living body by a predetermined position estimation method using the correlation matrix, and outputs a likelihood spectrum indicating a likelihood of the living body being present at the position;
• and
• a second number information calculator which estimates second number information or a position by a predetermined method from first position information possibly including a plurality of position candidates, the second number information being a total number of living bodies with an increased degree of likelihood.