ROTATIONAL FREQUENCY DETECTION DEVICE, ROTATION DETECTION DEVICE, AND ROTOR POSITION DETECTION DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a rotational frequency detection device, a rotation detection device, and a rotor position detection device, capable of detecting rotation with a simple structure even under a bright environment.;SOLUTION: A space S1 is formed between a transmitting antenna 2 and a radio wave reflection surface 44, and a space S2 is formed between the transmitting antenna 2 and a receiving antenna 3. The space S1 is surrounded by the radio wave reflection surface 44 and a radio wave absorber 5, and the space S2 is surrounded by the radio wave absorber 5. The transmitting antenna 2 is separated from the radio wave reflection surface 44 as long as a distance of about λ/4. A radio wave (reflected wave) of the transmitting antenna 2 reflected by the radio wave reflection surface 4 has a phase inverted following reflection, and negates mutually a radio wave (direct wave) proceeding directly from the transmitting antenna 2 to the receiving antenna 3. Hereby, a null point state wherein a null point at which each radio wave is weakened mutually is formed is generated. When a line member 9 is positioned in the space S2, the level of the radio wave in the space S2 is changed, and the null point state is affected thereby.;COPYRIGHT: (C)2011,JPO&INPIT