A voice band Hilbert transformer using switched capacitor technology

A voice band (300 Hz to 3000 Hz) Hilbert transformer used for the modulatio n and demodulation of SSB waves and synchronous detection of AM signals by the phase synthesis method is realized by cascade connection of linear all- pass filters. In order to reduce the total normalized capacitance and the n umber of analog switches, a novel all-pass filter using switched capacitors (SCAPF) is proposed. Further, by using the multifrequency sampling techniq ue, the capacitance ratio can be kept below 28. A sensitivity analysis of t he phase difference on the capacitance is carried out. II is found by simul ation that the phase difference is within 90 +/- 0.75 degrees if a 0.1% var iation of the capacitance ratio is allowed. By means of experiments with in dividual components, stable operation of the SCAPF is confirmed. (C) 1999 S cripta Technica, Electron Comm Jpn Pt 2, 82(6): 8-16, 1999.