Twin-T dual notch filter

Details Twin-T dual notch filter Twin-T dual notch filter

2006-10-24

2006-10-24

Urban, Edward F. (Department: 2618)

Telecommunications

Receiver or analog modulated signal frequency converter

Noise or interference elimination

C455S307000, C455S306000, C327S551000, C327S556000

Reexamination Certificate

active

07127226

ABSTRACT:
A communication filter circuit useful in a dual-mode receiver comprises a cascade of an active twin-T filter and a passive twin-T filter sections defining sharp notches at the center of second adjacent and of third adjacent channels, respectively, and specifically providing most attenuation at 60 kHz and at 90 kHz, for operation in the ISM136 band which has 30 kHz channel spacing. Since communication is channelized and limited in bandwidth, an active/passive twin-T notch filter structure is effective for signal attenuation. In a circuit in which real and imaginary signal components are processed, active-passive twin-T filters are provided in each of four signal paths, namely I and −I, Q and −Q.

REFERENCES:
patent: 3577179 (1971-05-01), West
patent: 3579135 (1971-05-01), Anderson
patent: 3683130 (1972-08-01), Kahn
patent: 5107491 (1992-04-01), Chew
patent: 5587924 (1996-12-01), Rossi
patent: 6035213 (2000-03-01), Tokuda et al.
patent: 6370211 (2002-04-01), Carsello
patent: 2002/0000874 (2002-01-01), Thomasson
patent: 2002/0168956 (2002-11-01), Murtojarvi
patent: 2003/0087622 (2003-05-01), Jayaraman et al.

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