    Omnidirectional plane-wave destruction  Next: Additional constraint Up: 2D linear phase approximation Previous: 2D linear phase approximation

## 2D maxflat condition

The frequency response of the objective phase shift operator is , where, are frequencies in radius in vertical and horizontal directions. We must design the coefficients so that the allpass system can obtain a similar linear phase response. The frequency response of is (8)

where is the phase of , which takes the following form: (9)

The phase approximating error is . In order to obtain an analytical , we remove and redefine the phase approximating error as     (10)

The sine function in the numerator can be expressed by 2D Taylor's expansion as   We use the maxflat phase criterion (Thiran, 1971), which means that the filter has a phase response as flat as the desired linear response. In the 2D case, the criterion is equivalent to the mathematical expression that the partial derivatives of the error function should be as small as possible. We set them to be zero: (11)

which is equivalent to the following 2D maxflat condition: (12)    Omnidirectional plane-wave destruction  Next: Additional constraint Up: 2D linear phase approximation Previous: 2D linear phase approximation

2013-08-09