Keith N Loi

US Patent:

6657521, Dec 2, 2003

Filed:

Apr 26, 2002

Appl. No.:

10/132949

Inventors:

Paul J. Tatomir - Fallbrook CA
James M. Barker - Torrance CA
Keith N. Loi - Monterey Park CA
Richard L. Bennett - Torrance CA
Louis W. Hendrick - Hermosa Beach CA
Rolf Kich - Redondo Beach CA

Assignee:

The Boeing Company - Seattle WA

International Classification:

H01P 710

US Classification:

333208, 333210

Abstract:

A microwave waveguide filter includes a main-line cavity structure with a group of at least two rectangular main-line cavities arrayed along a main propagation path and including a first main-line cavity and a second main-line cavity. Each main-line cavity includes a sidewall, and each pair of adjacent main-line cavities has a common transverse wall transverse to the main propagation path and a main-line aperture in the common transverse wall. A rectangular first feedback cavity is in microwave communication with each of the first main-line cavity and the second main-line cavity through the respective sidewall of the first main-line cavity and the second main-line cavity. There is a first-cavity feedback aperture between the first feedback cavity and the first main-line cavity, and a second-cavity feedback aperture between the first feedback cavity and the second main-line cavity. There may be additional feedback cavities as well.

US Patent:

6304160, Oct 16, 2001

Filed:

May 3, 1999

Appl. No.:

9/304458

Inventors:

Keith N. Loi - Rosemead CA
Paul J. Tatomir - Laguna Niguel CA

Assignee:

The Boeing Company - Seattle WA

International Classification:

H01P 120
H01P 706

US Classification:

333212

Abstract:

A cavity-coupled microwave filter that uses TE. sub. 011 and TE. sub. 01. delta. mode resonators. The cavity-coupled microwave filter includes an input port, a first resonator having a first opening, wherein the first opening receives electromagnetic energy from the input port, a second resonator having a second opening, wherein the second opening receives electromagnetic energy from the input port and wherein the first resonator and the second resonator are electromagnetically coupled. The cavity-coupled microwave filter further includes an output port, a third resonator having a third opening, wherein the third opening transfers electromagnetic energy to the output port and wherein the second resonator and the third resonator are electromagnetically coupled and a fourth resonator having a fourth opening, wherein the fourth opening transfers electromagnetic energy to the output port and wherein the third resonator and the fourth resonator are electromagnetically coupled. By using both positive and negative coupling between resonators and filter ports, both high side and low side transmission poles are created, thereby yielding a bandpass filter.

US Patent:

61183563, Sep 12, 2000

Filed:

Sep 16, 1998

Appl. No.:

9/154488

Inventors:

Keith N. Loi - Rosemead CA
Paul J. Tatomir - Laguna Niguel CA
Franz D. Davis - Annapolis MD
Robert J. Ahulii - Torrance CA
James W. Schultz - Redondo Beach CA

Assignee:

Hughes Electronics Corporation - El Segundo CA

International Classification:

H01P 120
H01P 1208
H01P 706
H01P 710

US Classification:

333209

Abstract:

A plurality of end caps engagable with a microwave cavity each have an underside configured differently to cause the microwave cavity to have different electrical responses depending on which end cap engages the microwave cavity. A microwave device includes a cylindrical cavity and an end cap movable within the cavity to change its axial position within the cavity thereby varying the volume and the electrical response of the cavity.

US Patent:

55348815, Jul 9, 1996

Filed:

Aug 31, 1994

Appl. No.:

8/298630

Inventors:

Frederick A. Young - Huntington Beach CA
Louis W. Hendrick - Hermosa Beach CA
Keith N. Loi - Rosemead CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

H01Q 330
H01P 1207
H01P 1213

US Classification:

343776

Abstract:

A microwave cavity filter (30, 30A) is formed of a section of waveguide (36, 114) terminated by end walls (38, 40, 44, 166, 168, 176) to form cavities (32, 34, 32A, 34A) wherein ridges (100, 102, 118, 120) are disposed longitudinally within a cavity and extend from the cavity wall partway to a central region (104, 124) of the cavity. In a preferred embodiment of the invention, the ridges are disposed symmetrically about a central plane (144), each ridge having a first component (106, 122) perpendicular to the central plane and a second component (108, 126) parallel to the central plane. A cross-sectional shape of a filter cavity may approximate a semicircle wherein one wall section (88, 130) of the filter cavity is disposed within a diametric plane (216) of the cavity. The end walls of the cavities may be constructed as iris plates with apertures (82, 182, 184, 186, 190) for coupling energy of selected modes of electromagnetic resonance within the respective cavities. Each cavity supports two orthogonal modes wherein, within the region, between the parallel second components of the two ridges, the electromagnetic fields of a first mode are parallel to the central plane and the electromagnetic fields of the second mode are perpendicular to the central plane.

US Patent:

56990294, Dec 16, 1997

Filed:

Apr 30, 1996

Appl. No.:

8/637967

Inventors:

Frederick A. Young - Huntington Beach CA
Keith N. Loi - Rosemead CA
Richard L. Bennett - Torrance CA

Assignee:

Hughes Electronics - Los Angeles CA

International Classification:

H01P 1208
H01P 1213

US Classification:

333212

Abstract:

A high performance bandpass filter is produced by adding one or more "simultaneous couplings" to a conventional resonant cavity filter. A "simultaneous coupling" is created when a filter's input or output signal, normally coupled to a filter's first or last cavity respectively, is coupled to one or more other cavities. Each simultaneous coupling causes a finite-frequency insertion loss pole to be created, which produces a quasi-elliptic frequency response on its side of the passband. These poles may be placed on the left and/or right sides of the passband, so that both symmetric and asymmetric quasi-elliptic frequency responses are realizable. A diplexer constructed from two such bandpass filters has the extremely sharp selectivity provided by two asymmetric bandpass filters, thus providing a high degree of receive/transmit isolation.

US Patent:

57606676, Jun 2, 1998

Filed:

Jul 12, 1995

Appl. No.:

8/501595

Inventors:

Frederick A. Young - Huntington Beach CA
Richard L. Bennett - Torrance CA
Keith N. Loi - Rosemead CA

Assignee:

Hughes Aircraft Co. - Los Angeles CA

International Classification:

H01P 1208
H01P 706

US Classification:

333212

Abstract:

A bandpass filter having 4-degrees of freedom includes a plurality of resonant cavities having respective Qs where at least one of the Qs is different. A plurality of main couplings couple successive resonant cavities to establish a main signal path that provides a first degree of freedom for controlling the shape of the filter's frequency response over its passband. A plurality of bridge couplings couple pairs of the resonant cavities so that the cavities are connected in a canonical circuit topology. The bridge couplings provide second and third degrees of freedom for controlling the sharpness of the frequency response 's transition between its passband and stopband and controlling the linearity of its phase, respectively. The cavities' non-uniform Qs provide a fourth degree of freedom for controlling the amplitude of the filter's frequency response in the passband so that the amplitude is within a predetermined tolerance of a desired passband shape.

US Patent:

60314346, Feb 29, 2000

Filed:

Sep 18, 1998

Appl. No.:

9/156245

Inventors:

Paul J. Tatomir - Laguna Niguel CA
Daniel J. Hoppe - La Canada CA
Christ P. Tzelepis - Redondo Beach CA
Keith N. Loi - Rosemead CA

Assignee:

Hughes Electronics Corporation - Los Angeles CA

International Classification:

H01P 512

US Classification:

333126

Abstract:

An ortho mode transducer (OMT)/multiplexer assembly having a corrugated junction and a coaxial dual mode waveguide resonator disposed around a central cylindrical waveguide. The corrugated junction diplexes signals, the higher frequencies passing through the central cylindrical waveguide and the lower frequencies passing through the coaxial dual mode resonator. Apertures in the dual mode resonator couple to an exit port and extract a first polarization from the lower frequencies passing through the dual mode resonator. The assembly may include a second aperture in the dual mode resonator for extracting a second polarization in a manner similar to the operation of the first aperture.

US Patent:

61509078, Nov 21, 2000

Filed:

May 3, 1999

Appl. No.:

9/304328

Inventors:

Keith N. Loi - Rosemead CA
Paul J. Tatomir - Laguna Niguel CA

Assignee:

Hughes Electronics Corporation - El Seguindo CA

International Classification:

H01P 1208

US Classification:

333212

Abstract:

The present invention is directed to improved coupling mechanisms for TE. sub. 011 and TE. sub. 01. delta. mode resonators. In one embodiment, the coupling mechanism provides an adjustable connection for transferring electromagnetic energy from a first resonator to a second resonator. Once the resonators are coupled, the coupling mechanism is adapted to allow adjustment of the magnitude and/or the phase of the electromagnetic energy while preserving the electromagnetic connection between the resonators. In another embodiment, the coupling mechanism provides a connection of the resonators using a waveguide. By varying the connection of the resonators with respect to the waveguide, positive relative coupling and/or negative relative coupling of the electromagnetic energy transferred between the waveguide and the resonators is provided.