Patent ID: 7539470

Claim:
A tracking filter for selecting a channel of a wideband frequency, which is for increasing the selectivity of a wideband frequency, comprising: a first tracking portion for filtering and amplifying a specific frequency band, wherein the first tracking portion has a low input impedance and a high output impedance; a second tracking portion for filtering and amplifying the specific frequency band while increasing the selectivity Q of a frequency outputted from the first tracking portion, wherein the second tracking portion has a high input impedance and a high output impedance; and a third tracking portion coupled to an output of the second tracking portion for filtering the specific frequency band, wherein the third tracking portion has a high input impedance and a low output impedance, wherein the first tracking portion comprises: an LC series type filter formed by connecting an inductor and a capacitor in series; and a common gate low noise amplifier (CG LNA) being connected to the output terminal of the LC series type filter and having a MOS transistor.