Patent ID: 7161416

Claim:
A programmable filter for a signal, comprising: an input stage providing a signal to be filtered; a tunable tank circuit coupled to the input stage and defining a pole of the filter at a first defined frequency, the tunable tank circuit including: a first filter network including a first voltage tunable device, a capacitor and an inductor, the first filter network having an input and an output, wherein the signal to be filtered is applied to the input of the first filter network; a first amplification stage having an input and an output, wherein the input of the first amplification stage is connected to the output of the first filter network; a peak detector coupled to the output of the amplification stage; a first sample and hold circuit having an input and an output, wherein the input of the first sample and hold circuit is connected to the peak detector; and a first single pole double throw switch connected between the first voltage tunable device and the input and output of the first sample and hold circuit, to selectively connect either the input or the output of the first sample and hold circuit to the first voltage tunable device; a tuning signal source providing a tuning signal at a selectively controllable frequency; a second single pole double throw switch connected between the input of the first filter network, and the input stage and the tuning signal source, to selectively provide either the signal to be filtered from the input stage or the tuning signal to the first filter network; and a controller coupled to the first and second switches and operative to: (a) control the tuning signal source to provide the tuning signal at the first defined frequency; (b) first control the first and second switches so that the tuning signal is applied to the input of the first filter network and the input of the first sample and hold circuit is applied to the first voltage tunable device; and (c) then control the first and second switches so that the signal to be filtered from the input stage is applied to the input of the first filter network and the output of the first sample and hold circuit is applied to the first voltage tunable device.