Ultrasonic doppler flow meter

An ultrasonic pulse Doppler flow meter comprising:

• transmitter-receiver means for transmitting ultrasonic pulsed continuous wave towards an object with a predetermined interval and receiving wave reflected by said object to obtain a reception signal;
• phase detecting means for generating a phase vector indicating the phase of said reception signal, each time said reception signal is obtained;
• first average phase difference calculating means for obtaining the phase difference .DELTA..theta. between the phase vector at current time point and the phase vector at the time preceding by one time period, each time said phase vector is obtained, decomposing it into a cosine component and a sine component, and calculating the angle represented by the average of a plurality of cosine components and the average of a plurality of sine components as a first average phase difference;
• second average phase difference calculating means for adding arguments of said phase difference vector to obtain the average thereof as a second average phase difference;
• and
• selecting means for selecting one of said first and said second average phase difference, depending on the magnitude of the speed of said object, as a signal indicating the speed of said object.

An ultrasonic pulse Doppler flow meter comprising:

• transmitter-receiver means for transmitting ultrasonic pulsed continuous wave towards an object with a predetermined interval and receiving wave reflected by said object to obtain a reception signal;
• phase detecting means for generating a phase vector indicating the phase of said reception signal each time said reception signal is obtained;
• first average phase difference calculating means for obtaining the phase difference .DELTA..theta. between the phase vector at current time point and the phase vector at the time preceding by one time period, each time said phase vector is obtained, decomposing it into a cosine component and a sine component, and calculating the angle represented by the average of a plurality of cosine components and the average of a plurality of sine components as a first average phase difference;
• second average phase difference calculating means for adding said phase difference .DELTA..theta. a plurality of times to obtain the average thereof as a second average phase difference;
• and
• correcting means for correcting said second average phase difference, using said first average phase difference, so that the addition and averaging in said second average phase difference calculating means is substantially effected by using the angle of said first average phase difference as the reference axis for the angle,
• wherein the average phase difference corrected by said correcting means is adopted as the signal indicating the speed of said object.

An ultrasonic pulse Doppler flow meter comprising:

• transmitter-receiver means for transmitting ultrasonic pulsed continuous wave towards an object with a predetermined interval and receiving wave reflected by said object to obtain a reception signal;
• phase detecting means for generating a phase vector indicating the phase of said reception signal, each time said reception signal is obtained;
• first average phase difference calculating means for obtaining the phase difference .DELTA..theta. between the phase vector at current time point and the phase vector at the time preceding by one time period, each time said phase vector is obtained, decomposing it into a cosine component and a sine component, and calculating the angle represented by the average of a plurality of cosine components and the average of a plurality of sine components as a first average phase difference;
• second average phase difference calculating means for adding arguments of said phase difference vector to obtain the average thereof as a second average phase difference;
• and
• correcting means for correcting said second average phase difference, using said first average phase difference, so that the addition and averaging in said second average phase difference calculating means is substantially effected by using the angle of said first average phase difference as the reference axis for the angle,
• wherein the average phase difference corrected by said correcting means is adopted as the signal indicating the speed of said object.

An ultrasonic pulse Doppler flow meter comprising:

• transmitter-receiver means for transmitting ultrasonic pulsed continuous wave towards an object at predetermined intervals T and receiving wave reflected by said object to obtain a reception signal;
• phase detecting means for detecting the phase of said reception signal and generating phase vectors sampled at said intervals T;
• first auto-correlating means for obtaining a first phase difference vector by correlating phase vectors having said interval T therebetween among said phase vectors sampled at said intervals T to calculate the argument thereof;
• second auto-correlating means for obtaining a second phase difference vector by correlating phase vectors having an interval nT (n being an integer not smaller than 2) therebetween among said phase vectors sampled at said intervals T to calculate the argument thereof;
• and
• selecting means for selecting the argument of said first phase difference vector for a high speed region and the argument of said second phase difference vector for a low speed region to obtain a signal indicating the speed of said object.

An ultrasonic pulse Doppler flow meter comprising:

• transmitter-receiver means for transmitting ultrasonic pulsed continuous wave towards an object at predetermined intervals T and receiving wave reflected by said object to obtain a reception signal;
• phase detecting means for detecting the phase of said reception signal and generating phase vectors sampled at said intervals T;
• first auto-correlating means for obtaining a first phase difference vector by correlating phase vectors having said interval T therebetween among said phase vectors sampled at said intervals T to calculate the argument thereof;
• second auto-correlating means for obtaining a second phase difference vector by correlating phase vectors having an interval nT (n being an integer not smaller than 2) therebetween among said phase vectors sampled at said intervals T to calculate the argument thereof;
• and
• correcting means for judging in which region the argument of said first phase difference vector is among angular regions devided by .+-..theta..sub.L1 and .+-..theta..sub.L2, wherein .theta..sub.L1 is .pi./n and .theta..sub.L2 is an angle at which spectral characteristics of said first auto-correlation means is a little higher than that of said second auto-correlation means, and effecting corrections on the argument of said second phase difference vector, depending on the judgement result to obtain a signal indicating the speed of said object.