Saw-based ladder filter including multiple coUpling coefficients

Details Saw-based ladder filter including multiple coUpling coefficients Saw-based ladder filter including multiple coUpling coefficients

1996-01-30

1997-08-05

Lee, Benny

Wave transmission lines and networks

Coupling networks

Electromechanical filter

333196, 310313D, 310313C, H03H 964

Patent

active

056546807

ABSTRACT:
A full duplex radio (10) having improved properties obtained by using surface acoustic wave (SAW) filters (92, 100, 100') having asymmetric frequency responses (76', 76", 140). The filters (92, 100, 100') are composed of series (50.sub.1, 50.sub.1 ') and parallel (50.sub.2, 50.sub.2 ') coupled SAW resonators. Asymmetry is obtained by altering the metallization thickness of either of the series (50.sub.1, 50.sub.1 ') or parallel (50.sub.2, 50.sub.2 ') resonators of each filter (92, 100, 100') to increase or decrease the SAW coupling coefficient of some of the resonators (50.sub.1, 50.sub.1 ', 50.sub.2, 50.sub.2 ') relative to the remainder of the resonators (50.sub.1, 50.sub.1 ', 50.sub.2, 50.sub.2 '). The filters (92, 100, 100') are desirably in pairs arranged with mirror image frequency asymmetry such that the steeper skirts (93, 95) of the frequency responses (76', 76", 140) are adjacent. Greater passband bandwidths (91', 91") can be obtained without adverse affect on transmitter and receiver isolation.

REFERENCES:
patent: 5313177 (1994-05-01), Hickernell et al.
patent: 5327626 (1994-07-01), Cho et al.
patent: 5434464 (1995-07-01), Hickernell et al.
patent: 5471178 (1995-11-01), Hickernell
patent: 5486800 (1996-01-01), Davenport
patent: 5499003 (1996-03-01), Davenport
patent: 5506552 (1996-04-01), Seki et al.

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