Patent ID: 8357096

Claim:
An ultrasound system, comprising: a transmission/reception unit operable to transmit/receive ultrasound signals in a pulse repetition frequency (PRF) to form an n number of Doppler signals; a signal processing unit operable to compute a first mean frequency based on an n th Doppler signal and an (n−1) th Doppler signal and a second mean frequency based on an n th Doppler signal and an (n−k) th Doppler signal, respectively, wherein k is a positive integer equal to or greater than 2, the signal processing unit being further operable to check whether the first and second mean frequencies exist within predetermined frequency ranges associated with the PRF, respectively, to determine occurrence of aliasing in the Doppler signals and compensate for the aliasing of the Doppler signals to thereby produce Doppler signals with the aliasing compensated; wherein the signal processing unit includes a quadrature demodulating unit operable to demodulate the Doppler signals into baseband signals consisting of an I signal of an in-phase component and a Q signal of a quadrature component, and wherein the signal processing unit is operable to compute the first and mean frequencies through following equations, First ⁢ ⁢ mean ⁢ ⁢ frequency = P ⁢ ⁢ R ⁢ ⁢ F 2 ⁢ ⁢ π ⁢ tan - 1 ⁢ ∑ n = 1 N ⁢ i ⁡ ( n - 1 ) ⁢ q ⁡ ( n ) - i ⁡ ( n ) ⁢ q ⁡ ( n - 1 ) ∑ n = 1 N ⁢ i ⁡ ( n ) ⁢ i ⁡ ( n - 1 ) + q ⁡ ( n ) ⁢ q ⁡ ( n - 1 ) , and Second ⁢ ⁢ mean ⁢ ⁢ frequency = P ⁢ ⁢ R ⁢ ⁢ F 2 ⁢ ⁢ k ⁢ ⁢ π ⁢ tan - 1 ⁢ ∑ n = 1 N ⁢ i ⁡ ( n ) ⁢ q ⁡ ( n - k ) - i ⁡ ( n - k ) ⁢ q ⁡ ( n ) ∑ n = 1 N ⁢ i ⁡ ( n ) ⁢ i ⁡ ( n - k ) + q ⁡ ( n ) ⁢ q ⁡ ( n - k ) wherein i(n) represents and nth I signal outputted from the quantrature demodulating unit, q(n) represents an nth Q signal outputted from the quadrature demodulating unit, i(n−1) represents an (n−1)I signal, q(n−1) represents an (n−1) th Q signal, n represents an ensemble length, i(n−k) represents an (n−k) th I signal outputted from the quadrature demodulating unit, and q(n−k) represents an (n−k) th Q signal outputted from the quadrature demodulating unit; and an image processing unit operable to form a Doppler mode image based on the Doppler signals produced by the signal processing unit.