| 摘要 |
An apparatus to control a tuneable Gm-C filter, including and a filter that can be reconfigured as a free running oscillator by toggling the feedback sign of an output amplifier (304), a digital controller (42), sensitive to the output of the filter in the calibration configuration, and a DAC (44) to provide an analogue control signal (48) to the gm inputs of the transconductance amplifiers (310, 320) composing the filter. |
| 主权项 |
1. Apparatus for tuning a Gm-C filter, comprising:
a Gm-C filter including one or several interconnected Gm-C cells, the Gm-C cells having a transconductance amplifier, a tuning terminal, and a transconductance gain (gm) that is dependent from an electric value present on the tuning terminal; the Gm-C filter including one or more switching elements, allowing to configure the Gm-C filter in a calibration configuration and in a filtering configuration; a digital controller, operatively arranged to measure a response of the Gm-C filter in the calibration configuration, and to generate a digital tuning value depending on the response measured; a digital-to-analogue converter, converting said digital tuning value into an analogue tuning signal, fed to the tuning terminals of the Gm-C cells; and an amplitude regulation unit operatively arranged to limit the forward gain when the Gm-C filter is in the calibration configuration; wherein the apparatus is operatively arranged to converge, in the calibration configuration, to a predefined response, and the digital-to-analogue converter is operatively arranged to maintain the resulting tuning signal in the filtering configuration. |
