Patent ID: 6744883
Filing Date: 2004-06-01
Classification: H04M

Abstract:
A filter system that suppresses interference imposed on at least one communications channel by at least one signal component outside of a specified amplitude range, the filter system comprising:at least one filter stage having an amplitude-dependent transfer function, the amplitude-dependent transfer function implemented using at least one bi-directional current limiting filter, the at least one bi-directional current limiting filter comprising: a first terminal; a second terminal, the at least one bi-directional current limiting filter suppressing current outside a first specified amplitude range when the current enters the first terminal and exits the second terminal and suppressing current outside a second specified amplitude range when the current enters the second terminal and exits the first terminal; a first transistor having a first current carrying electrode, a second current carrying electrode, and a first control electrode activated by a first variable; a second transistor having a third current carrying electrode, a fourth current carrying electrode, and a second control electrode activated by a second variable, the second variable being inversely related to the first variable; a first diode having its anode connected to a first internal node and having its cathode connected to the first terminal; a second diode having its anode connected to a second internal node and having its cathode connected to the second terminal; the first transistor with the first control electrode, the first current carrying electrode, and the second current carrying electrode, the first control electrode being connected to a third internal node, the first current carrying electrode being connected to the first internal node, and the second current carrying electrode being connected to the first terminal; the second transistor with the second control electrode, the third current carrying electrode, and the fourth current carrying electrode, the second control electrode being connected to a fourth internal node, the third current carrying electrode being connected to the second internal node, and the fourth current carrying electrode being connected to the second terminal; and a load network connected to the first internal node, the second internal node, the third internal node, and the fourth internal node.