Abstract: In the is paper, several wideband digital quadrature technique are discussed, including FFT transforming and discrete filter based on Hilbert transforming. A special quadrature sampling technique for arbitrary bandpass signal within bassband sample rate is also presented.Their performances with the quadrature principles of Gram-Schmidt are analyzed the errors of I and Q correction are given The computer stimulations show that in wide range of input frequency expect for discrecte filter,the other methods can obtain very low image power relative to the primary response.