Sensor and information acquisition apparatus using sensor

A sensor to transmit and detect an electromagnetic wave, the sensor comprising:

• a substrate;
• a transmitting unit and a receiving unit integrated on the substrate;
• and
• a polarization converting unit,
• wherein the transmitting unit includes:
• a generating element configured to generate a first electromagnetic wave, and
• a first antenna electrically connected with the generating element and configured to emit the first electromagnetic wave, wherein the first electromagnetic wave emitted by the first antenna has a first polarization direction,
• wherein the polarization converting unit is configured to convert the first electromagnetic wave into a third electromagnetic wave having a third polarization direction for reflection on a subject, and convert the reflected third electromagnetic wave into a second electromagnetic wave having a second polarization direction,
• wherein the receiving unit includes:
• a second antenna configured to receive the second electromagnetic wave having a second polarization direction, and
• a detecting device electrically connected with the second antenna and configured to detect the second electromagnetic wave received by the second antenna,
• wherein, to reduce a change of a characteristic of the generating element by reflected electromagnetic waves entering into the transmitting unit, the polarization converting unit converts a polarization state of the first electromagnetic wave such that combining a reflected electromagnetic wave, having a polarization state that differs from the polarization state of the reflected first electromagnetic wave, with the first antenna is more difficult than combining the reflected first electromagnetic wave with the first antenna.