Ultrasonic measuring method and ultrasonic measuring apparatus

An ultrasonic measuring apparatus that uses a coded spread spectrum ultrasonic signal, which has a predetermined carrier frequency and which has been modulated with codes that have a coding period synchronized with the carrier frequency, to estimate at least one of the propagation distance and propagation orientation of the coded spread spectrum ultrasonic signal, the apparatus comprising:

• a receiving section for receiving the coded spread spectrum ultrasonic signal in at least two receivers, and generating at least two received signals;
• an quadrature detection section for performing an quadrature detection on the at least two received signals using the carrier frequency, and producing I and Q components of the received signals;
• a vector operation section for performing phase difference processing on the I and Q components of the received signals with a coding period that is synchronized with the period of the carrier frequency, and obtaining I′ and Q′ components from which a phase shift caused by a Doppler shift has been canceled;
• a despreading section for despreading the I′ and Q′ components of the received signals using different codes from the codes at time intervals that are synchronized with the carrier frequency, and obtaining despread I″ and Q″ components;
• a demodulating section for obtaining information about the amplitudes and phases of the respective received signals by carrying out computations on the I″ and Q″ components of the received signals;
• and
• a distance/orientation calculating section for calculating at least one of the propagation distance and propagation orientation of the ultrasonic wave based on the information about the amplitudes and phases that has been obtained from the respective received signals.