Patent ID: 6233293
Filing Date: 2001-05-15
Classification: H03C,H03H,H03L,H04L

Abstract:
A frequency-tracking filter circuit for a communication device having a frequency synthesizer and current-controlled oscillator circuit which generates an output frequency in linear proportion with a control current therefor, comprising a tunable filter stage, operational characteristics of which are controllable in accordance with said control current, such that said tunable filter stage has a cut-off frequency that is linearly proportional to said control current, wherein said tunable filter stage comprises a tunable transconductance-containing filter stage and a transconductance tuning stage coupled thereto, operational characteristics of said tunable transconductance containing filter stage and said transconductance tuning stage being controllable in accordance with said control current in such a manner that said tunable transconductance containing filter stage has a cut-off frequency that is linearly proportional to said control current.