Electrical filter structure

Patent metadata

Field	Value
Publication number	US-12176591-B2
Application number	US-202217721939-A
Country	US
Kind code	B2
Filing date	Apr 15, 2022
Priority date	Feb 10, 2020
Publication date	Dec 24, 2024
Grant date	Dec 24, 2024

Abstract

An electrical filter structure for forwarding an electrical signal from a first port, e.g. P 1 , to a second port, e.g. P 2 , in a frequency selective manner, wherein the filter is a microwave filter, the electrical filter structure comprising: a plurality of pairs of an open stub and a short-circuited stub coupled electrically in parallel to a transmission line comprising a plurality of transmission line portions at a plurality of respective junctions between adjacent transmission line portions, e.g. Cross junction; and wherein the first port is connected with a first of the junctions having a first pair comprising a first open stub and a first short-circuited stub; wherein the second port is connected with a last of the junctions having a last pair comprising a last open stub and a last short-circuited stub; wherein lengths of the pair of the open stub and the short-circuited stub coupled to a same of the junctions are chosen such that electrical lengths of the open stub and short-circuited stub of the respective pairs are equal within a tolerance of +/−10%.

First claim

The invention claimed is:

1. A microwave filter structure for forwarding an electrical signal from a first port to a second port in a frequency selective manner, the microwave filter structure comprising:
a plurality of pairs of an open stub and a short-circuited stub coupled in parallel, wherein the plurality of pairs is coupled electrically to a transmission line, and wherein the transmission line comprises a plurality of transmission line portions and wherein the plurality of pairs couple to the plurality of transmission line portions at a plurality of junctions between adjacent transmission line portions; and
wherein the first port is coupled with a first junction of the plurality of junctions that is coupled to a first pair comprising a first open stub and a first short-circuited stub;
wherein the second port is coupled with a last junction of the plurality of junctions that is coupled to a last pair comprising a last open stub and a last short-circuited stub; and
wherein lengths of a pair of an open stub and a short-circuited stub coupled to a same one of the plurality of junctions are sized such that electrical lengths of the open stub and short-circuited stub of a respective pair are longer by at least 2% than a fourth of a wavelength of a signal having a frequency of a passband center frequency of the microwave filter structure and equal within a tolerance of +/−10%.

2. The microwave filter structure according to claim 1 , wherein lengths of the plurality of transmission line portions are sized wherein electrical lengths of each of the plurality of transmission line portions are shorter, by at least 10 percent, than a fourth of a wavelength of a signal having a frequency of a passband center frequency of the microwave filter structure.

3. The microwave filter structure according to claim 1 , wherein the lengths of the plurality of transmission line portions are sized wherein electrical lengths of each of the plurality of transmission line portions are shorter, between 15 to 50 percent than a fourth of a wavelength of a signal having a frequency of a passband center frequency of the microwave electrical filter structure.

4. The microwave filter structure according to claim 1 , wherein the plurality of pairs and the plurality of junctions create a symmetrical structure, and wherein the plurality of pairs and the plurality of transmission line portions comprise:
N short-circuited stubs having lengths, SST(s);
with 1≤s≤N, N open stubs having lengths, OST(s); and
N−1 transmission line portions having lengths, TLs; and
wherein the N short-circuited stubs are configured to fulfil a formula (1), the N open stubs are configured to fulfil a formula (2) and the N−1 transmission line are configured to fulfil a formula (3);

SST
⁡

(
k
)

⁢

=

S
⁢
S
⁢

T
⁡

(

N
+
1
-
k

)

,

[

k
≤

floor
⁢

⁢

(

N
/
2

)

]

(
1
)

OST
⁡

(
k
)

=

OST
⁡

(

N
+
1
+
k

)

,

[

k
≤

floor
⁢

⁢

(

N
/
2

)

]

(
2
)

TL
⁡

(
k
)

=

T
⁢

L
⁡

(

N
-
k

)

,

[

k
≤

floor
⁢

⁢

(

Assignees

• Advantest Corp

Inventors

• Bianchi Giovanni

Classifications

• H01P1/203

  Strip line filters · CPC title

• H01P7/086

  Coplanar waveguide resonators (H01P7/088 takes precedence) · CPC title

• H01P1/2013 Primary

  Coplanar line filters · CPC title

• H01P1/2039 Primary

  Galvanic coupling between Input/Output · CPC title