Corrugated waveguide filter having coupled resonator cavities

Details Corrugated waveguide filter having coupled resonator cavities Corrugated waveguide filter having coupled resonator cavities

1999-05-10

2001-01-02

Lee, Benny (Department: 2817)

Wave transmission lines and networks

Coupling networks

Wave filters including long line elements

C333S034000

Utility Patent

active

06169466

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention is directed to the field of electronic filters. More particularly, the present invention provides a compact waveguide filter providing band-pass or low-pass response in the microwave frequency range.
2. Description of the Related Art
Waveguide filters are known in this art. There are two primary types of filters for use in the microwave frequency range (i.e. from about 2-20 GHz)—symmetrically corrugated filters and iris filters. However, both of these types of filters suffer from many disadvantages.
An example of a symmetrically corrugated filter is shown in U.S. Pat. No. 3,597,710 to Levy (“the '720 patent”).
FIG. 1
of the '720 patent shows a standard E-plane corrugated structure having a uniform waveguide channel with a plurality of symmetrical corrugations. But as noted in the '720 patent, these types of corrugated filters are typically low-pass only. Such a filter typically cannot provide a band-pass response.
The '720 patent purports to have advantages over the standard corrugated structure by forming a plurality of capacitive irises. Instead of forming a uniform waveguide channel, the '720 patent provides a series of iris structures (FIGS.
2
and
6
), which have different heights. Although the irises and the corrugations are of different height, for any one iris or corrugation the structure is symmetrical. Another example of an iris filter (known as an H-plane iris filter) is shown in U.S. Pat. No. 2,585,563 to Lewis, et al. This type of iris filter suffers from many disadvantages, however. First, it typically provides band-pass response only, i.e., it is incapable of providing a combination response, such as low-pass and band-pass, or just a low-pass response. Secondly, the iris filter is typically a large structure, as the irises are generally separated along the waveguide channel by a half of a wavelength (&lgr;g/2). Since the number of irises typically correlates to the order of the filter, when the order of the filter is high, such as 5th order or greater, the filter is very large.
Other types of filters include resonant iris filters (as shown in U.S. Pat. No. 1,788,538 to Norton and U.S. Pat. No. 1,849,659 to Bennett) and evanescent-mode ridged filters (as shown in U.S. Pat. No. 4,646,039 to Saad). The resonant iris filter utilizes a plurality of resonant diaphragms as resonating elements that are separated by a quarter of a wavelength (&lgr;g/4). The evanescent-mode ridged filter is based on a wavelength structure with a ridged cross section. However, a common problem with both of these types of filters is that they typically cannot handle high-powered signals.
Therefore, there remains a general need in this field for a compact waveguide filter that provides multi-order band-pass or low-pass response, and is capable of handling high-powered signals in the GHz range.
SUMMARY OF THE INVENTION
A corrugated waveguide filter is provided having a plurality of coupled resonator cavities arranged in a horizontal or vertical manner. The filter may also include an input transformer section and an output transformer section for matching the filter to external waveguide lines. Each resonator includes at least two extracted slots (or cavities) that are grouped in close proximity to each other, and which may be symmetrically or asymmetrically implemented in the waveguide. The resonators each contribute one reflection zero and two transmission zeros to the frequency response of the filter, the reflection zero being located within the pass-band of the filter, and the two transmission zeros located either at the high-side or low-side of the pass-band, depending upon whether the resonator is a low-pass type or a high-pass type. The dimensions of the resonator, including the depth of the slots and the distance between the slots, determines the position of the reflection zero and whether the resonator is low-pass or high-pass.
According to one aspect of the invention a corrugated waveguide filter is provided that includes an input transformer section and an output transformer section for connecting the waveguide filter to external waveguide lines, wherein each transformer section includes at least one stepped waveguide section and provides a reflection zero to the frequency response of the filter, and a filter section coupled between the input transformer section and the output transformer section, the filter section including a waveguide channel and a plurality of coupled resonator cavities, wherein each coupled resonator cavity provides a reflection zero and two transmission zeros to the frequency response of the filter.
Another aspect of the invention provides a corrugated waveguide filter having a waveguide channel and a plurality of coupled resonator cavities extracted from the waveguide channel, each resonator cavity including two extracted slots, wherein the distance between the slots in each resonator determines its resonant frequency.
Still another aspect of the invention provides a corrugated waveguide filter having a plurality of horizontally-spaced coupled resonator cavities, wherein each resonator contributes one reflection zero and two transmission zeros to the frequency response of the filter, and a plurality of coupling transformers for connecting the resonator cavities, wherein each coupling transformer vertically connects two resonator cavities.
It should be noted that these are just some of the many aspects of the present invention. Other aspects not specified will become apparent upon reading the detailed description set forth below.
The present invention overcomes the disadvantages of presently known filters and also provides many advantages, such as: (1) compact size; (2) high-powered capability; (3) sharp roll-off on both sides of the pass-band; (4) low insertion loss; (5) wide and deep rejection response; (6) optional transformer units; and (7) either horizontal or vertical implementations.
These are just a few of the many advantages of the present invention, which is described in more detail below in terms of the preferred embodiments. As will be appreciated, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the spirit of the invention. Accordingly, the drawings and description of the preferred embodiments set forth below are to be regarded as illustrative in nature and not restrictive.


REFERENCES:
patent: 1788538 (1931-01-01), Norton
patent: 1849656 (1932-03-01), Bennett
patent: 2540488 (1951-02-01), Mumford
patent: 2585563 (1952-02-01), Lewis et al.
patent: 3046503 (1962-07-01), Cohn
patent: 3271706 (1966-09-01), Rooney
patent: 3597710 (1971-08-01), Levy
patent: 3611214 (1971-10-01), Gerlack
patent: 3621483 (1971-11-01), Craven
patent: 3634788 (1972-01-01), Craven
patent: 3639862 (1972-02-01), Craven et al.
patent: 3819900 (1974-06-01), Ironfield
patent: 3838368 (1974-09-01), Ironfield
patent: 3949327 (1976-04-01), Chapell
patent: 4155056 (1979-05-01), Cross et al.
patent: 4492020 (1985-01-01), Cobb
patent: 4626809 (1986-12-01), Mizumura et al.
patent: 4646039 (1987-02-01), Saad
patent: 4673903 (1987-06-01), Saad
patent: 4749973 (1988-06-01), Kaneko et al.
patent: 5004993 (1991-04-01), Reindel
patent: 5243618 (1993-09-01), Dolezal et al.
patent: 5357591 (1994-10-01), Jiang et al.
patent: 5381596 (1995-01-01), Ferro
patent: 5598300 (1997-01-01), Magnusson et al.
patent: 5600740 (1997-02-01), Asfar
patent: 5715271 (1998-02-01), Huang et al.
“Tapered Corrugated Waveguide Low-Pass Filters”, R. Levy, IEEE Transactions On Microwave Theory And Techniques, Aug. 1973, vol. MTT-21, pp. 526-532.
“Microwave Filters, Impedance-Matching Networks, and Coupling Structures”, G. Matthaei, L. Young, E. Jones, Artech House, Inc., 1980, pp. 380-381.

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