Recursive switched-capacitor Hilbert transformers

Efficient implementation of discrete-time Hilbert transformers using switched-capacitor techniques is presented. The proposed network is composed of structurally allpass filters as basic building blocks. As a result, the phase difference of 90 degrees is obtained, for the Hilbert transform pair, with very small sensitivity with respect to capacitance ratio errors. A design example is considered, which includes experimental results obtained in the laboratory with a prototype Hilbert transformer