US 5,291,161 AGranted

Microwave band-pass filter having frequency characteristic of insertion loss steeply increasing on one outside of pass-band

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorHiroshi Saka

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Abstract

In a microwave band-pass filter provided with a main line having an input terminal and an output terminal on both ends thereof, first, second, third and fourth open-ended stubs having lengths L1, L2, L3 and L4 connected electrically in parallel to the main line at intervals L0, L0' L0", respectively. The lengths of two of the four open-ended stubs are selected to be substantially equal to a quarter of the wavelength of the first stop-band frequency signal on the band lower than the pass-band, and the lengths of the others thereof are selected to be substantially equal to a quarter of the wavelength of the second stop-band frequency signal on the band higher than the pass-band. In this case, the insertion loss thereof steeply increases on a boundary band from one stop-band to the pass-band. In particular, there can be obtained the microwave band-pass filter having a simpler structure, in which the insertion loss steeply increases on the band higher or lower than the pass-band, and the insertion loss on the band lower or higher than the pass-band is relatively large over a relatively wide band, respectively.

Claims22

Dependent claims

A microwave band-pass filter comprising:

a main line having an input terminal and an output terminal on both ends thereof;
and
first, second, third and fourth open-ended stubs having lengths L1, L2, L3 and L4, respectively, said first to fourth open-ended stubs connected electrically in parallel to said main line at intervals L0, L0' and L0", respectively,
wherein (a) the lengths L1 and L4 of said first and fourth open-ended stubs are selected to be substantially equal to a quarter of the wavelength of the first stop-band frequency signal on the band lower than the pass-band in such a manner that attenuation poles thereof are placed substantially within the band of the first stop-band frequency signal;
(b) the lengths L2 and L3 of said second and third open-ended stubs are selected to be substantially equal to a quarter of the wavelength of the second stop-band frequency signal on the band higher than the pass-band in such a manner that attenuation poles thereof are placed substantially within the band of the second stop-band frequency signal;
(c) the intervals L0, L0' and L0", and the lengths L1, L2, L3 and L4 are selected so as to satisfy either one of first conditions of 2L0'<L2.apprxeq.L3<L1.apprxeq.L4 <L0<2L1, and second conditions of 2L0'<L2=L3<L1=L4<L0<2L1 and so that L0"=L0 or L0".apprxeq.L0.

3 more elements

A microwave band-pass filter comprising:

a main line having an input terminal and an output terminal on both ends thereof;
and
first, second, third and fourth open-ended stubs having lengths L1, L2, L3 and L4, respectively, said first to fourth open-ended stubs connected electrically in parallel to said main line at intervals L0, L0' and L0", respectively,
wherein (a) the lengths L1 and L4 of said first and fourth open-ended stubs are selected to be substantially equal to a quarter of the wavelength of the first stop-band frequency signal on the band higher than the pass-band in such a manner that attenuation poles thereof are placed substantially within the band of the first stop-band frequency signal;
(b) the lengths L2 and L3 of said second and third open-ended stubs are selected to be substantially equal to a quarter of the wavelength of the second stop-band frequency signal on the band lower than the pass-band in such a manner that attenuation poles thereof are placed substantially within the band of the second stop-band frequency signal;
and
(c) the intervals L0, L0' and L0", and the lengths L1, L2, L3 and L4 are selected so as to satisfy either one of first conditions of 2L0<L1.apprxeq.L4<L2.apprxeq.L3<L0'<2L2, and second conditions of 2L0<L1=L4<L2=L3 <L0'<2L2 and so that L0"=L0 or L0".apprxeq.L0.

4 more elements

Dependencies are inferred from the claim text.