Deep rejection reflectionless filters
AssigneeAssociated Universities, Inc.
InventorMatthew A. Morgan
Life of this patent
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Abstract
Reflectionless electronic filters, as well as a method for designing such filters is disclosed, along with a method of realizing critical subcircuits within those filters that mimic the behavior of tee- and pi-networks having negative elements, though the critical subcircuits themselves are entirely passive. This allows a much broader range of transmission responses to be realized in reflectionless form than in the prior art, and especially with lower ripple factor for deeper rejection in equal-ripple Chebyshev responses. Reflectionless filters preferably function by absorbing the stop-band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications.
Claims15
A reflectionless electronic filter comprising:
- an electrically symmetric, two-port circuit, wherein the symmetrical behavior defines an even-mode equivalent circuit and an odd-mode equivalent circuit when the two ports are driven in-phase and 180 degrees out-of-phase, respectively;
- at least one substantially lossless element;
- at least one substantially lossy element or impedance-matched internal subnetwork;
- and
- at least one critical subcircuit comprising a transformer and one or more lumped-elements;
- wherein the at least one critical subcircuit has only positively valued lumped elements, and has an electrical response equivalent to a tee- or pi-network having at least one lumped-element of a negative value, such that:
- a normalized input impedance of the even-mode equivalent circuit is substantially equal to a normalized input admittance of the odd-mode equivalent circuit;
- and
- a normalized input admittance of the even-mode equivalent circuit is substantially equal to a normalized input impedance of the odd-mode equivalent circuit.
Dependencies are inferred from the claim text.