US 5,479,142 AGranted

Strip dual mode filter in which a resonance width of a microwave is adjusted and dual mode multistage filter in which the strip dual mode filters are arranged in series

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsKazuaki Takahashi, Munenori Fujimura, Hiroyuki Yabuki, Mitsuo Makimoto

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Abstract

A strip dual mode filter consists of a strip line ring resonator having an electric length equivalent to a resonance wavelength .lambda..sub.o for resonating microwaves at the resonance wavelength .lambda..sub.o according to a characteristic impedance thereof, an input coupling capacitor for transmitting the microwaves from an input terminal to a coupling point A of the ring resonator, an output coupling capacitor for outputting the microwaves resonated in the ring resonator from a coupling point B of the ring resonator to an output terminal, and a phase-shifting circuit connected to a coupling point C and a coupling point D of the ring resonator for changing the characteristic impedance of the ring resonator by shifting a phase of the microwave by a multiple of a half-wavelength of the microwaves. The coupling point B is spaced a quarter-wavelength of the microwaves apart from the coupling point A, the coupling point C is spaced the half-wavelength of the microwaves apart from the coupling point A, and the coupling point D is spaced the half-wavelength of the microwaves apart from the coupling point B.

Claims21

Dependent claims

A strip dual mode filter in which a first microwave signal and a second microwave signal are resonated and filtered, comprising:

a ring-shaped strip line in which the first microwave signal is resonated and filtered according to a first characteristic impedance thereof and the second microwave signal is resonated and filtered according to a second characteristic impedance thereof, the ring-shaped strip line having a first terminal, a second terminal, a third terminal, and a fourth terminal positioned at even intervals and in that order;
a first input terminal coupled to the first terminal of the ring-shaped strip line in electromagnetic coupling to transfer the first microwave signal to the first terminal;
a second input terminal coupled to the second terminal of the ring-shaped strip line in electromagnetic coupling to transfer the second microwave signal to the second terminal;
a first resonance capacitor connected to the first and third terminals of the ring-shaped strip line to adjust the first characteristic impedance of the ring-shaped strip line for the first microwave signal, the second characteristic impedance of the ring-shaped strip line for the second microwave signal being not changed by the first resonance capacitor;
a first output terminal coupled to the third terminal of the ring-shaped strip line in electromagnetic coupling to output the first microwave signal from the ring-shaped strip line;
and
a second output terminal coupled to the fourth terminal of the ring-shaped strip line in electromagnetic coupling to output the second microwave signal from the ring-shaped strip line.

4 more elements

A dual mode multistage filter comprising:

a plurality of ring-shaped strip lines arranged in series which each have a first terminal A, a second terminal C, a third terminal B, and a fourth terminal D positioned at even intervals in that order to resonate a first microwave signal according to a first characteristic impedance thereof and to resonate a second microwave signal according to a second characteristic impedance thereof;
a plurality of first resonance capacitors which each connect the first and third terminals A and B of the ring-shaped strip line to adjust the first characteristic impedance of each of the ring-shaped strip lines, a phase of the first microwave signal being varied by the first resonance capacitors;
a plurality of first inter-stage capacitors which each couple the third terminal B of the ring-shaped strip line arranged in an N-th stage (N is an integral number) with the first terminal A of the ring-shaped strip line arranged in an (N+1)-th stage, the first terminal A of the ring-shaped strip line arranged in a first stage being coupled to a first input terminal to receive the first microwave signal, the third terminal B of the ring-shaped strip line arranged in a final stage being coupled to a first output terminal to output the first microwave signal;
and
a plurality of second inter-stage capacitors which each couple the fourth terminal D of the ring-shaped strip line in the N-th stage with the second terminal C of the ring-shaped strip line in the (N+1th) stage, the second terminal C of the ring-shaped strip line in the first stage being coupled to a second input terminal to receive the second microwave signal, and the fourth terminal D of the ring-shaped strip line in the final stage being coupled to a second output terminal to output the second microwave signal.

2 more elements

Dependencies are inferred from the claim text.