U.S. patent number 3,740,675 [Application Number 05/064,361] was granted by the patent office on 1973-06-19 for yig filter having a single substrate with all transmission line means located on a common surface thereof.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to Robert A. Moore, Theodore M. Nelson.
United States Patent |
3,740,675 |
Moore , et al. |
June 19, 1973 |
YIG FILTER HAVING A SINGLE SUBSTRATE WITH ALL TRANSMISSION LINE
MEANS LOCATED ON A COMMON SURFACE THEREOF
Abstract
One or more non-overlapping transmission line conductors
fabricated on one planar surface of a single slab of an electric
material mounted on a ground plane. At least one YIG resonator
element is located in a cavity formed in the surface of the
substrate facing the ground plane. The YIG resonator element,
moreover, is positioned in close proximity to said one or more
transmission line conductors a selected distance below the outer
surface of the substrate and below the transmission line
circuitry.
Inventors: |
Moore; Robert A. (Severna Park,
MD), Nelson; Theodore M. (Catonsville, MD) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
Family
ID: |
22055411 |
Appl.
No.: |
05/064,361 |
Filed: |
August 17, 1970 |
Current U.S.
Class: |
333/205; 333/204;
333/202 |
Current CPC
Class: |
H01P
1/218 (20130101) |
Current International
Class: |
H01P
1/218 (20060101); H01P 1/20 (20060101); H01p
003/08 (); H03h 007/08 () |
Field of
Search: |
;333/73R,24.1,24.2,24.3,1.1,84M,84,10,11,76,73S |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Lewin - "A Resonance Absorption Isolator," in Microstrip for 4GC/S
Proceedings of IEE Part B Supplement 1957; Title Page & pp.
364-365. .
"Ferrites Can be Replaced With Yttrium Iron Garnet," in Electronic
Design, Aug. 6, 1958, single page. .
Matthaei, "Magnetically Tunable Band-Stop Filters," in IEEE
Transactions on Microwave Theory and Techniques, March, 1965; pp.
203-212. .
Barret - "Microwave Printed Circuits-A Historical Survey," in IRE
Transactions on Microwave Theory and Techniques, March, 1955; Cover
Page and pp. 1-7 .
Mariner - "Introduction to Microwave Practice" Academic Press,
Inc., New York, 1961; Title Page & pp. 33-35..
|
Primary Examiner: Rolinec; Rudolph V.
Assistant Examiner: Nussbaum; Marvin
Claims
We claim as our invention:
1. A magnetic tunable microstrip transmission line filter,
comprising in combination:
a. dielectric substrate means having inner and outer faces;
b. ground plane means having inner and outer faces, said outer face
thereof abutting the inner face of said dielectric substrate
means;
c. first and second microstrip transmission line means for
transmitting electromagnetic wave energy located on said outer face
of said substrate means;
d. ferrimagnetic resonator means positioned to selectively couple
said electromagnetic wave energy between said first and second
microstrip transmission line means;
e. means for magnetically biasing said ferrimagnetic resonator
means; wherein
f. said first and second transmission lines include substantially
equal parallel line portions and wherein said resonator means
comprises at least one yttrium iron garnet sphere located in close
proximity to said parallel line portions.
2. The invention as defined by claim 1 wherein said sphere is
located between said parallel line portions beneath said outer face
of said dielectric substrate means.
3. The invention as defined by claim 1 wherein said first and
second transmission line means comprise first and second line
conductors, and a short circuit conductor contacting said first and
second line conductors, said first and second line conductors and
said short circuit conductor being located in substantially a
common plane on said outer face of said dielectric substrate means,
and wherein said resonator means comprises at least one YIG
resonator element located in close proximity to said first and
second line conductors.
4. The invention as defined by claim 3 wherein said at least one
YIG resonator is located directly beneath at least one line
conductor.
5. The invention as defined by claim 1 wherein said first and
second transmission line means comprise first and second line
conductors, and a short circuit conductor contacting said first and
second line conductors, said first and second line conductors and
said short circuit conductor being located in substantially a
common plane on said outer face of said dielectric substrate means,
wherein said resonator means comprises a plurality of YIG
resonators located in close proximity to said first and second line
conductors.
6. The invention as defined by claim 5 wherein said plurality of
YIG resonators are comprised of a first and a second sphere of
single crystal yttrium-iron-garnet respectively located beneath
said first and second line conductors.
7. The invention as defined by claim 1 wherein said first and
second transmission line means comprise first and second line
conductors located in substantially a common plane on said outer
face of said dielectric substrate and passing through said
dielectric means at a point in proximity to said resonator means
and respectively terminating in an electrical short circuit on said
outer face of said ground plane.
8. The invention as defined by claim 7 wherein said resonator means
comprises at least one YIG resonator element located in close
proximity to said first and second line conductor and said
electrical short circuit.
9. The invention as defined by claim 7 wherein said resonator means
comprises a plurality of YIG resonators.
10. The invention as defined by claim 9 wherein said plurality of
YIG resonators comprises at least three YIG resonators arranged in
a row beneath said outer face of said substrate substantially
perpendicular to said first and second line conductor and within a
boundary defined by said line conductors.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetically tunable
filters and more particularly to magnetically tunable bandpass and
band stop filters which utilize ferrimagnetic resonators in
combination with deposited or etched microstrip line conductors on
a dielectric substrate.
2. Description of the Prior Art
The basic principles and theory of operation of ferrimagnetic
resonators used as filters in waveguides, strip transmission lines
and the like appears in a publication entitled "Design of
Magnetically Tunable Microwave Filters Using Single Crystal
Yttrium-Iron-Garnet Resonators," by P. S. Carter, Jr. appearing in
the IRE Transactions by Microwave Theories and Techniques, Volume
MTT-9, pages 252- 260 (May, 1961). Also reference is made to a text
entitled MIcrowave Filters, Impedance-Matching Networks and
Coupling Structures, George L. Matthaei, et al., McGraw-Hill, Inc.,
1964, pp. 1043- 1085, inclusive.
Ordinarily, strip transmission line YIG filters are comprised of
overlapping or crossing strip transmission lines at right angles to
each other with a YIG sphere located between the transmission line
at the point of overlap. If the point of overlap is an RF short
circuit and a magnetic field of the proper magnitude is applied to
the YIG sphere at right angles to the two transmission lines,
filtering and power limiting will occur. Such apparatus is
mentioned as being known prior art in U.S. Pat. No. 3,289,112
issued to Charles E. Brown. This patent, however, additionally
discloses the concept of locating the YIG sphere beneath the
overlapping lines in a cavity of one of the dielectric wall members
instead of between the overlapping striplines. The overlapping
striplines are printed on a pair of opposing dielectric wall
members and the two lines are peeled back and extended through one
of the two dielectric wall members to a ground plane associated
therewith in order to form an RF short circuit for signals applied
to the conductors. While the Brown patent teaches a novel means of
coupling two stripline elements to a single pole or resonator and
has an advantage over certain types of YIG filters in that the YIG
sphere need not be between the two coupled lines, it has the
disadvantage of most types of YIG filters in that it is restricted
to a single YIG sphere coupling both lines and therefore only
single pole filters can be realized by this technique.
SUMMARY OF THE INVENTION
The present invention is an improvement in apparatus of the type
referred to above and is particularly suitable for fabrication into
integrated circuitry. In the present invention a single or
multi-pole YIG filter is disclosed which comprises a single
dielectric substrate mounted on a ground plane so that its inner
face is contiguous with one surface of the ground plane. One or
more non-overlapping microstrip line conductors are fabricated on
the outer face of the substrate and terminate at input and output
couplers of electromagnetic energy located at the edges of the
substrate. A selected number, one or more, YIG resonator elements
are located in a cavity formed in the inner face of the substrate
so that said selected number of resonator elements are positioned
beneath the outer face in close proximity to said one or more line
conductors. A magnetic field is applied substantially orthogonal to
the outer face to tune said selected number of YIG resonators to
provide a predetermined filtering action of electromagnetic signals
being transmitted between said input and output couplers.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a first embodiment of the subject
invention and being illustrative of a single pole bandstop
filter;
FIG. 2( a) is a fragmentary view of FIG. 1 taken along the line
2--2 illustrating the location of a YIG sphere in the
substrate;
FIG. 2(b) is a fragmentary view of FIG. 1 taken along the line 2--2
illustrating a YIG disc resonator element mounted in the
substrate;
FIG. 3 is a perspective view of a second embodiment, being
illustrative of a single pole filter having two non-crossing
microstrip line conductors on the outer face of the substrate;
FIG. 4 is a fragmentary view of the embodiment shown in FIG. 3
taken along the line 4--4 illustrating the location of a YIG sphere
in relation to the two microstrip line conductors;
FIG. 5 is a perspective view of a third embodiment of the subject
invention being illustrative of a two pole filter and including two
microstrip line conductors fabricated on the outer face of the
substrate and terminating in a short circuit thereon;
FIG. 6 is a fragmentary view of FIG. 5 taken along the line 6--6
illustrating the location of two YIG resonators in relation to the
microstrip line conductors;
FIG. 7 is a perspective view of a fourth embodiment of the subject
invention similar to the embodiment shown in FIG. 5;
FIG. 8 is a fragmentary view of the embodiment shown in FIG. 7
taken along the line 8--8;
FIG. 9 is a partial cut away view of the embodiment shown in FIG. 7
modified to embody a three pole YIG filter; and
FIG. 10 is a partial cut away view of the embodiment shown in FIG.
7 modified to embody a four pole YIG filter.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 and 2(a), a single microstrip line conductor
10 is deposited or etched on the outer face 12 of a dielectric
substrate 14 which may be comprised of for example alumina,
sapphire or some other ceramic material. The dielectric substrate
14 is mounted on a metallic ground plane 16 which is coextensive
with its inner face 18. The microstrip line conductor 10 is of a
substantially constant width and thickness and extends between
opposite edges of the dielectric substrate 14 terminating at each
end in an electrical connector 20 and 22 which is adapted to couple
electromagnetic energy to and from the line conductor 10. A cavity
24 is fabricated into the inner face 18 directly beneath the line
conductor 10 between the RF connectors 20 and 22. In the present
embodiment the cavity 24 comprises a round dimple wherein a YIG
sphere resonator element 26 is positioned so that it lies a
predetermined distance, for example 0.005 inches below the upper
surface 12 of the substrate 14. Additionally, the inner face 28 of
the ground plane 16 contains a recess 30 including a dimple 32 for
accepting the protrusion of the YIG sphere 26 when it is of such a
size relative of the thickness of the substrate 14 that it would
otherwise prevent mating of the surfaces 18 and 28.
When RF signals are applied to the line conductor 10 by means of
the connectors 20 and 22 and a DC biasing magnetic field H of the
proper magnitude is applied to the YIG sphere 26 substantially
orthogonal to the line conductor 10, signals within a predetermined
frequency range will not pass the point of the YIG sphere when it
is at or near its point of resonance, thereby providing a bandstop
filter. If for example RF energy is coupled into connector 20 only
those frequencies which have been passed will exit at the other
connector 22.
While it is desirable in certain applications to utilize a YIG
sphere 28 such as shown in FIG. 2(a) as the resonator element, it
sometimes becomes desirable to utilize a YIG resonator in the form
of a disc which is shown in FIG. 2(b) and identified by reference
numeral 34. In the embodiment shown, the disc 34 has a diameter
substantially equal to the circular dimension of the cavity 25 and
does not protrude below the inner face 18 of the substrate.
The second embodiment of the subject invention is shown in FIGS. 3
and 4. It comprises a single pole bandpass or bandstop filter
including a pair of non-overlapping microstrip line conductors 36
and 38 of substantially equal width dimensions fabricated on the
outer face 12 of the dielectric substrate 14 so that a portion of
their respective lengths run parallel to each other and then
diverge into respective RF connectors located at the edges of the
substrate. More particularly, microstrip line conductor 36 runs
diagonally across a portion of the outer face 12 terminating in the
RF connectors 40 and 42 while line conductor 38 also runs
diagonally across the outer face 12 separated from the other
conductor 36 by predetermined separation and terminating in
respective RF connectors 44 and 46. Midway between the parallel
portions of the two line conductors 36 and 38 is a selected number
of, in this case one, YIG resonator elements shown as a YIG sphere
26 located in the substrate 14 beneath the outer face 12. Rather
than being located directly beneath the line conductor 10 as shown
in the embodiment in FIG. 1, the present embodiment locates the YIG
sphere 26 between the parallel line portions of the conductors 36
and 38. By applying a DC biasing magnetic field H through the YIG
sphere 26 selective coupling of electromagnetic energy occurs
between the line conductors 36 and 38 because of the resonance
characteristic of the YIG sphere. This configuration is adapted to
provide low insertion loss bandpass coupling between the
transmission lines 36 and 38.
For minimum insertion loss bandpass transmission an RF short must
be applied at the location of the sphere 26. This can be provided
in the embodiment shown in FIG. 3 for example, by external short
circuits shown schematically by the reference numerals 41 and 45
directly connected from the connectors 40 and 44, respectively, to
the ground plane 16. When this is done input signals applied to one
of the opposite connectors 42 or 46 will be coupled out of the
other connector. By selectively adjusting these short circuits for
example by means of sliding shorts, not shown, the effect of the
short circuit will be transformed on each line 36 and 38 to a
position adjacent the sphere 26 wherein the tightest coupling will
occur and best transmission effects will result. It should be
noted, however, when desirable the short circuits could be applied
to connectors 42 and 46 and connectors 40 and 44 utilized as the
input-output ports for coupling between microstrip line conductors
36 and 38.
A third embodiment of the subject invention is shown in FIGS. 5 and
6 and comprises a first and a second microstrip line conductor 48
and 50 fabricated on the upper face 12 of the substrate 14 and
which terminate in a short circuit 52 also fabricated on the upper
face 12. The first line conductor 48 extends to one edge of the
substrate 14 but turning at a substantially right angle inwardly of
the edge to contact the short circuit 52. The second line conductor
50 extends to an adjacent edge of the substrate 14 and running in a
substantially straight line to the short circuit 52 but being
substantially parallel to a relatively small portion of the line
conductor 48 in proximity to the short 52. A cavity 54 is formed in
the inner face 18 of the substrate 14 directly beneath the portions
of the line conductors 48 and 50 which are adjacent to the short
52. A first and a second YIG resonator element 56 and 58 in the
form of a sphere are located in the cavity 54 respectively beneath
the line conductor 48 and 50 by means of the dimples 60 and 62
formed therein. Both YIG resonator elements 56 and 58, however, do
not contact the respective line conductors but lie beneath the
upper face 12 of the substrate 14 by predetermined separation. This
separation was illustrated in reference to the first embodiment
described with respect to FIGS. 1 and 2(a). Additionally, the
ground plane 16 includes a recess 64 beneath the cavity 54 in order
to accommodate a portion of the YIG resonator elements 56 and 58.
Whereas the embodiment shown in FIGS. 3 and 4 required four RF
connectors, the third embodiment requires only two connectors 66
and 68 respectively coupled to the extremities of the line
conductors 48 and 50 which appear at the adjacent edges of the
substrate 14. When RF signals are applied to line conductors 48 and
50 by means of the RF connectors 66 and 68 and a DC biasing
magnetic field H of proper magnitude is applied to the YIG
resonator elements 56 and 58, a two pole filter of the bandpass
type will be provided and selective coupling between line
conductors 48 and 50 will occur due to the resonance phenomenon of
the YIG resonator elements.
Referring now to FIGS. 7 and 8 there is illustrated a fourth
embodiment of the subject invention which is similar to the
embodiment shown in FIG. 5 with the exception that the electrical
short 52 on top of the substrate 14 is deleted and the microstrip
conductors 48 and 50 are terminated in a short near the YIG spheres
56 and 58 on the upper or inner face 28 of the ground plane 16.
This is provided by the holes 49 and 51 completely through the
substrate 14. By a suitable metal plating procedure the conductors
48 and 50 are extended into the holes 49 and 51, respectively and
an electrical contact made with the ground plane 16. This is shown
in greater detail in FIG. 8.
Although up to this point one and two pole YIG filters have been
considered, the present invention particularly as regards the last
embodiment shown in FIGS. 7 and 8 is adapted to be configured with
three or more poles or YIG resonators. For example, FIG. 9
discloses a modification of the embodiment shown in FIG. 7 to
include three equally spaced YIG resonators 56, 57, and 58 located
in the recess 64 along a row transverse to the line conductors 48
and 50 under the surface 12 of the substrate 14. FIG. 10, on the
other hand, illustrates a four pole YIG filter and includes four
resonators 56, 58, 59 and 61 arranged in a row transverse to the
line conductors 48 and 50.
What has been shown and described, therefore, is an improvement in
YIG filter apparatus requiring one substrate, and one ground plane
with all of the microstrip line conductor means being located on a
common surface or face in a non-overlapping fashion with the YIG
resonator element means being located in the substrate beneath the
microstrip line conductors.
* * * * *