Pulse doppler flow speed meter

Claim 2

A pulse doppler flow speed meter comprising: a sound wave transmission means for transmitting, a pulsed continued ultrasonic sound wave at at least a first and second transmission intervals interatively toward an object; sound wave reception means for detecting, a sound wave signal reflected by said object; phase detection means for detecting, a phase signal in the reflected signal by mixing the reflected signal at each reception with a reference signal; an MTI filter which performs filtering with the same filtering characteristics for phase signals corresponding to said first transmission interval and phase signals corresponding to said second transmission interval among the phase signals provided sequentially by said phase detection means by employing an unchanged delay time on respective filtering operations; first phase difference detecting means for detecting, sequentially a phase difference between a phase signal at the present time point and a phase signal at a preceding time point among phase signals passing sequentially through said MTI filter; second phase difference detection means for detecting, a phase difference between a first phase difference ascribed to said first transmission interval and a second phase difference ascribed to said second transmission interval among phase differences detected sequentially by said first phase difference detection means; and means for transforming the output of said second phase difference detection means into the speed of said object.

Claim 3

A pulse doppler flow speed meter according to claim 1, wherein said first and second transmission intervals take place alternately, and wherein said MTI filter including means for filtering based on the difference between the phase signal of a present time point and a phase signal of two time points ago.

Claim 4

A pulse doppler flow speed meter according to claim 1, wherein said first and second transmission intervals take place alternately, and wherein said MTI filter includes means for filtering by an operation using at least both of a phase signal of the present time point and a phase signal retarded for a sum of said first and second transmission intervals.

Claim 5

A pulse doppler flow speed meter according to claim 1, wherein said first transmission interval (T) and said second transmission interval (T+Ts) have an interval ratio p:q and said first and second transmission intervals each take place for a plurality of number of times consecutively, and wherein said MTI filter includes means for filtering by an operation using at least both a phase signal of the present time point and a phase signal retarded for Td which is given by the following equation: Td=r·T=s(T+Ts) where r=c/q, s=c/p, and c is a common multiple of p and q which provided an integral ratio.

Claim 6

A pulse doppler flow speed meter according to claim 1, wherein said sound wave transmission means has a further period of transmission in which said second transmission interval and a third transmission interval take place alternately.

Claim 7

A pulse doppler flow speed meter according to claim 5, wherein said sound wave transmission means has a further period of transmission in which said third transmission interval and a fourth transmission interval take place alternately.

Claim 8

A pulse doppler flow speed meters comprising: sound wave transmission means for transmitting, a pulsed continuous ultrasonic sound wave at a first transmission interval toward an object for a plurality of number of time and for transmitting a pulsed continuous ultrasonic sound wave at a second transmission interval toward said object for a plurality of number of times; sound wave reception means for detecting a sound wave signal reflected by said object; phase detection means for detecting a phase signal in the reflected signal by mixing the reflected signal at each reception with a reference signal; a first MTI filter which performs filtering with the same filtering characteristics for phase signals corresponding to said first transmission interval and phase signals corresponding to said second transmission interval among the phase signals provided sequentially by said phase detection means by employing an unchanged delay time on respective filtering operations; first phase difference detection means for detecting sequentially a phase difference between a phase signal at the present time point and a phase signal at a preceding time point among phase signals passing sequentially through said MTI filter; second phase difference detection means for detecting a phase difference between a first phase difference ascribed to said first transmission interval and a second phase difference ascribed to said second transmission interval among the phase differences detected sequentially by said first phase difference detection means; a second MTI filter which eliminates stationary object signals in the phase signals provided sequentially by said phase detection means; third phase difference detection means for detecting a phase difference based on at least one of a first set of phase signals corresponding to said first transmission interval and a second set of phase signals corresponding to said second transmission interval among the phase signals passing sequentially through said second MTI filter; modification means for modifying the output of said third phase difference detection means using the output of said second phase difference detection means; and means for transforming the modified phase difference into the speed of said object.

Claim 9

A pulse doppler flow speed meters comprising: sound wave transmission means for transmitting, a pulsed continuous ultrasonic sound wave at a first transmission interval toward an object for a plurality of number of time and for transmitting a pulsed continuous ultrasonic sound wave at a second transmission interval toward said object for a plurality of number of times; sound wave reception means for detecting a sound wave signal reflected by said object; phase detection means for detecting a phase signal in the reflected signal by mixing the reflected signal at each reception with a reference signal; a first MTI filter which performs filtering with the same filtering characteristics for phase signals corresponding to said first transmission interval and phase signals corresponding to said second transmission interval among the phase signals provided sequentially by said phase detection means by employing an unchanged delay time on respective filtering operations; first phase difference detection means for detecting sequentially a phase difference between a phase signal at the present time point and a phase signal at a preceding time point among phase signals passing sequentially through said MTI filter; second phase difference detection means for detecting a phase difference between a first phase difference ascribed to said first transmission interval and a second phase difference ascribed to said second transmission interval among the phase differences detected sequentially by said first phase difference detection means; a second MTI filter which eliminates stationary object signals in the phase signals provided sequentially by said phase detection means; third phase difference detection means for detecting a phase difference based on at least one of a first set of phase signals corresponding to said first transmission interval and a second set of phase signals corresponding to said second transmission interval among the phase signals passing sequentially through said second MTI filter; modification means for modifying the output of said third phase difference detection means using the output of said second phase difference detection means; and means for transforming the modified phase difference into the speed of said object.

Claim 10

A pulse doppler flow speed meter according to claim 7, wherein said second MTI filter including means for performing a filtering process of second order or higher.

Claim 11

A pulse doppler flow speed meter according to claim 7, wherein said third phase difference detection means including means for detecting phase differences based on the first and second sets of phase signals.