초록 ▼

A full duplex radio (10) having improved properties is obtained by using asymmetric surface acoustic wave (SAW) filters (70, 92, 100, 100', 112). The filters (70, 92, 100, 100', 112) are composed of series (50.sub.1, 50.sub.1 ') and parallel (50.sub.2, 50.sub.2 ') coupled SAW resonators. Asymmetry i

A full duplex radio (10) having improved properties is obtained by using asymmetric surface acoustic wave (SAW) filters (70, 92, 100, 100', 112). The filters (70, 92, 100, 100', 112) 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 covering either of the series (50.sub.1, 50.sub.1 ') or parallel (50.sub.2, 50.sub.2 ') resonators of each filter (70, 92, 100, 100', 112) with a dielectric layer (96) to increase the SAW coupling coefficient (Cs, Cp) of the covered resonators (50.sub.1 ', 50.sub.2 ') relative to the uncovered resonators (50.sub.1, 50.sub.2). The filters (70, 92, 100, 100', 112) are desirably in pairs arranged with mirror image frequency asymmetry such that the steeper skirts (87, 79) of the frequency response (91', 91") are adjacent. Greater pass-band bandwidths (77, 77', 77") can be obtained without adverse affect on transmitter and receiver isolation.

대표청구항 ▼

[ We claim:] [1.] A filter device utilizing surface acoustic wave (SAW) resonators comprising:a first filter with first series coupled SAW resonators with a first SAW coupling coefficient and second parallel coupled SAW resonators with a second SAW coupling coefficient, anda second filter with third

[ We claim:] [1.] A filter device utilizing surface acoustic wave (SAW) resonators comprising:a first filter with first series coupled SAW resonators with a first SAW coupling coefficient and second parallel coupled SAW resonators with a second SAW coupling coefficient, anda second filter with third series coupled SAW resonators with a third SAW coupling coefficient and fourth parallel coupled SAW resonators with a fourth SAW coupling coefficient, wherein a first ratio of said first SAW coupling coefficient divided by said second SAW coupling coefficient has a first value and a second ratio of said third SAW coupling coefficient divided by said fourth SAW coupling coefficient has a second value different than said first value.