US3611197A

US3611197A - Yig resonator microstrip coupling device

Info

Publication number: US3611197A
Application number: US889514A
Authority: US
Inventors: Robert A Moore; Theodore M Nelson; James M Flaherty
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1969-12-31
Filing date: 1969-12-31
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05

Abstract

A microstrip manifold providing a plurality of frequency selective outputs from a single input signal including a common input microstrip transmission line terminated at one end and a plurality of output microstrip transmission lines disposed substantially normal to the input transmission line and coupled thereto by means of respective yttrium iron garnet (YIG) sphere resonators, each being tuned to a predetermined resonant frequency by a separate magnetic field to provide isolation between each of the output transmission lines. Additionally, each of the output transmission lines are terminated at a short circuit in proximity to the respective YIG sphere. The input conductor is not grounded at the YIG spheres but is terminated at the end of the line.

Description

United States Patent [72] Inventors Robert A. Moore Severna Park; Theodore M. Nelson, Catonsvllle; James M. Fhherty, Catonnvllle, all of Mr].

[Zl] Appl. No. 889,514

[22] Filed Dec. 31, I969 451 Patented on. s, 1971 73] Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

50 Field olSeareh 333/l.l,6, 10, 24.2, 73, 73 c, 73 s, 73 w [56] RelerencesClted UNITED STATES PATENTS 2,816,270 12/1957 Lewis, 3; 3 7 w x Primary Examiner-Herman Karl Saalbach Assistant ExaminerPaul L. Gensler Attorneyr- F. H. Henson, E. P. Klipfel and J. L. Wiegretfe ABSTRACT: A microstrip manifold providing a plurality of frequency selective outputs from a single input signal including a common input microstrip transmission line terminated at one end and a plurality of output microstrip transmission lines disposed substantially normal to the input transmission line and coupled thereto by means of respective yttrium iron garnet (YIG) sphere resonators, each being tuned to a predetermined resonant frequency by a separate magnetic field to provide isolation between each of the output transmission lines. Additionally, each of the output transmission lines are terminated at a short circuit in proximity to the respective YlG sphere. The input conductor is not grounded at the YIG spheres but is terminated at the end of the line.

l8 SIGNAL 2 l SIGNAL OUT l SIGNAL OUT PATENTED UN 5 B?! SHEET 2 [IF 2 T T RooR TEMPERATURE 6 (LINEAR (FILTER BANK] POLARIZATION I |ooc [FILTER BANK) 5 f 4 ROOM TEMPERATURE 5 POLAR'ZAT'OM |00C(SINGLE FILTER] E 2 LL! 2 0 l l 1 1 FIG-4 .2 l3 .4 R gr 20 1 E r. FIGS -5-4-3-2|o|2345 ONE HALF RESONATOR BANDWIDTHS Bl36-VA6 YIG RESONATOR MICROS'I'RIP COUPLING DEVICE The invention herein described was made in the course of or under a contract or subcontract thereunder the Department of the Air Force per AF l9(628)5 l 67.

BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates generally to the field of microwave energy transmission apparatus and more particularly to an electronically tunable manifold coupler having a single input transmission line and a plurality of frequency responsive output channels employing YiG resonators tuned to selected frequencies by means of respective unidirectional magnetic fields.

2. Description of the Prior Art Frequency selective waveguide coupling devices having ferrite elements biased to difierent resonant frequencies are disclosed in U.S. Pat. No. 3,214,519 issued to L. Nathanmn. Magnetically tunable band-stop and band-pass filters including YlG resonators in combination with stripline apparatus are disclosed in U.S. Pat. No. 3,268,838 issued to G. L. Matthaei. Also a YlG preselector is disclosed in U.S. Pat. No. 3,299,376 issued to R. Blau, et al. Additional prior art disclosing various embodiments of YlG filters are the following: U.S. Pat. No. 3,290,625, to R. .l. Bartram, et al. U.S. Pat. No. 3,368,169, to R. S. Caner, et al. U.S. Pat. No. 3,426,297, to M. Cohen; and U.S. Pat. No. 3,435,385, to M. Cohen.

The prior art requires the use of a circularly polarized input signal or a grounded termination of the input transmission line at the YIG resonator. Both of these requirements in the embodiments disclosed preclude the provision of multiple output channels coupled to a single input channel. The present inven tion provides for coupling of a plurality of YIG resonators to the input channel wherein neither circularly polarized energy nor a shorted terminal input terminal immediately at each of the YIG resonators is required.

SUMMARY Briefly, the subject invention is directed to a manifold coupler for microwave electromagnetic energy wherein .a plurality of frequency selective outputs is obtained from a single transmitted input signal and comprises, inter alia, an input microstrip transmission line coupled at one end to a source f microwave energy and terminated at its other end by a predetermined impedance connected to a point of reference potential. A plurality of output microstrip transmission lines are parallely disposed transverse to the input transmission line and separated therefrom by a ground plane. Each of the plurality of output transmission lines is terminated at one end by a short circuit in the ground plane. The ground plane contains an opening or an iris between each of the output transmission lines and the transverse input transmission line wherein a YlG sphere is located. The YIG sphere additionally is in close proximity to the short circuit termination of the respective output transmission line. A separate magnetic field is applied through each of the YlG sphere elements to separately resonate each of the V16 spheres to a predetermined frequency whereby each of the output transmission lines transmit separate frequency signals without interaction between adjacent output transmission lines or channels. The magnetic field is applied through each of the '10 spheres by means of a separate magnet located above the respective output transmission line in proximity to the iris and the sphere contained therein.

BRIEF DESCRIPTION OF THE DRAWINGS F 1G. I is an exploded perspective view of the preferred embodiment of the subject invention;

FIG. 2 is a fragmentary top view of the preferred embodiment of the subject invention;

FIG. 3 is a cross-sectional view of the embodiment shown in FIG. 2 taken along the lines 3-3;

FIG. 4 is a diagram illustrative of the insertion loss vs. frequency characteristic of the subject invention; and

FIG. 5 is a diagram illustrative of the obtainable bandwidth characteristics from the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Before proceeding to a detailed description of the subject invention. it should be pointed out that ferrite resonators in the form of a sphere of yttrium iron garnet (YIG) are well known to those skilled in the art. These elements comprise highly polished single crystals having a narrow line width in the neighborhood of 0.3 to 0.5 oersteds. These elements, moreover are available commercially and are fabricated from a single crystal by a tumbling process in which successively finer and finer grits are used. Although the orientation of the crystallographic axis of the elements affects the frequency response, this is not of primary significance in the device comprising the subject invention. A more detailed explanation of the crystal structure and the nomenclature used to define it can be found in "Introduction to Solid State Phyics" by Kittie (John Wiley and Sons, inc., 1953).

The ferrite elements act as they do because of Larmor recession. That is to say the electrons in the ferrites have a magnetic moment or spin and because of this spin, tend to precess when subjected to the action of a DC field. The plane of this processional movement, moreover, is at right angles to the field lines. For example, consider a YlG spherical element situated at the origin of a X-Y-Z coordinant system wherein RF energy is coupled in along the X-axis and coupled out along the Y-axis The frequency at which coupling will occur from the input to the output depends upon the magnitude of the unidirectional or DC magnetic field directed along the Z- axis When the YIG sphere is not magnetized, there is no power transfer between the axes. When a DC magnetic field indicated by the arrow H in FIG. I, is applied along the Z-axis the orthogonal E-vector of the input RF energy causes the electrons in the YIG sphere to precess around the Z-axis This produces of RF magnetic movement along the Y-axis to induce a voltage therein. Precession for a YIG sphere is strongest at ferrimagnetic resonance and coupling from input to output is also strongest at resonance. Coupling varies ofi resonance as detennined by the degree of coupling of the input and output to the YIG sphere. Thus the loaded 0 of such a device is determined not only by the unloaded Q of the YIG material, but by the tightness of the coupling between the input and the output. It has been observed that increasing 0 makes possible an approximate constant bandwidth as a function of frequency.

Referring to the drawings, the apparatus comprising the subject invention as disclosed in FIGS. I, 2 and 3 includes an input microstrip transmission line I0 comprised of a strip of current conducting material disposed on a dielectric member 12 which may be, for example, a sheet of alumina having a predetermined thickness. The input transmission line It) is disposed on one outer surface 13 of the dielectric member 12 and extends the entire length thereof to provide a first and a second

terminal end

14 and 16, respectively as shown by FIG. 2. Coupled to the terminal ends I4 and 16 are a pair of

RF connectors

18 and 20. The RF connector II is adapted to receive an input microwave signal. The RF connector 20 is adapted to be coupled to a suitable RF termination 22. which may be, for example, a dummy load, or the like and which is shown schematically as a load impedance connected to a point of reference potential illustrated as ground. A second dielectric member 24 similar to the first dielectric member 12 and having substantially the same dimensions such as length, width and thickness includes a plurality of output microstrip transmission lines 26 of current conducting material disposed in substantially parallel relationship on one outer surface 27 of the layer 24 as shown by FIGS 1 and 2. The outer ends 28 of the transmission lines 26 terminate at the edge of the insulating layer 24 while the other ends 30 of the lines 26 extend through the openings or holes 32 through the entire thickness of the dielectric member 24 to the mutually opposite surface 33 as shown by FIG. 3, where they terminate in a metal ground plane 34. Moreover, the output microstrip transmission lines 26 cross the input transmission line at substantially right angles. The metal ground plane 34 as shown by FIG. 3 separates the

dielectric members

12 and 24 and is contiguous with the surfaces and 33 thereof which are seen to be opposite from the surfaces containing the input transmission line 10 and the plurality of output transmission lines 26. The metal ground plane 34 has substantially the same length and width dimensions of the insulated layers 12 and 2A and is electrically common to the point of ground reference potential. The metal ground plane 34 ha a predetermined thickness and includes a plurality of round apertures or irises 36 corresponding in number to the plurality of output transmission lines 26. Moreover. the irises 36 are respectively located at a point directly beneath the output transmission lines 26 and directly above the input transmission line 10 such that the plurality of irises 36 are substantially in line with the length of conducting material forming the input transmission line 10. A sample of ferrimagnetic material comprised of a single crystal garnet compound such as yttrium iron garnet (YIG) in the form of a sphere 38 is located within each of the irises 36 between the input transmimion line 10 and the respective output transmission line 26. When desirable gallium yttrium iron garnet (GaYIG) may be used. This is shown by means of the exploded perspective view of FIG. I and the cross sectional view thereof as shown by FIG. 3.

While the configuration thus described comprises the preferred embodiment of the invention, two other forms of TEM transmission line e.g. coaxial and stripline could be used when desirable. Also another embodiment visualized consists in a configuration wherein all of the conductors are on one surface rather than being disposed on both sides of the ground plane.

Associated with each of the YIG spheres 38 is a respective circular permanent magnet which is situated over each of the output transmission lines 26 so that its magnetic I-I-field intersects the YIG sphere orthogonally with respect to the direction of the electric field of the RF energy which would exist in the input transmission line 10 in the plurality of parallel output transmission line III in the plurality of parallel output transmission lines 26. This is disclosed with reference to the exploded view of the present invention as disclosed by FIG. I and the fragmentary top view thereof as shown in FIG. 2. Although a permanent magnet is shown, any type of apparatus for generating a unidirectional magnetic field may be utilized.

The plurality of output transmission lines 26 are shorted to the ground plane 34 through the holes 32 in the second insulating layer 24 as shown in FIG. 3. It should be pointed out, however, that this termination is preferably less than a quarter of a wavelength from the YIG spheres 38 of the range of frequencies being transmitted in the input transmission line 10. The magnitude of the magnetic field H of each of the magnets 40 selectively establish a resonant frequency of the respective YIG spheres 38 so that each of the plurality of output transmission lines 26 have energy coupled thereto from the input transmission at the respective resonant frequency of its YIG sphere 38. Thus each of the YIG spheres 38 couples to the input transmission line 10 at its resonant frequency while leaving energy undisturbed at other frequencies.

By coupling the terminated input transmission line 10 to a single source of microwave energy having a spectrum of various frequencies, the subject invention will selectively channel certain selected frequencies on each of the output transmission lines 26, thereby providing a RF manifold of microwave energy.

While the reference to prior art devices normally utilize circularly polarized electromagnetic energy or a grounded termination of the input line at the resonator for obtaining resonant coupling from an input transmission line to an output transmission line by means of a YlG resonator, it has been observed that the subject invention as embodied by the configuration shown in FIGS. 1-3 is operable with a linearly polarized energy input with a substantial transfer to the plurality of parallel output transmission line strips 26 with only an approximately 3 db. insertion loss as evidenced by FIG. 4 which dis- 5 closes the insertion loss for both linear and circular polarization at room temperature and 100' C. operating between the frequency range of l to 1.5 GHz (IXIO' Hz.). Although the data for FIG. 4 was obtained for operation in the frequency range of l.0 to 1.5 GHz, by utilizing GaYIG as the resonators l0 operation can be achieved covering the frequency range from below 200 MHz to above l.8 Gl-Iz; however, theexact insertion loss and bandwidth characteristics will depend upon the actual frequency range utilized.

Each of the resonantly tuned YIG spheres 38 act as a 15 frequency filter so that selective tuning of each of the output channels by means of its respective magnet 40 can produce a filter bank having frequency characteristics such as shown by FIG. 5a and 5b. Both sets of curves disclose a tuning of each of the YIG spheres 38 to provide a series of filters which exhibit frequency overlap. For example. FIG. 5a discloses a bandwidth characteristic of a single tuned filter whereas FIG. 5b discloses a bandwidth characteristic for double tuned filter.

What has been shown and described, therefore, is a manifold directional coupler providing selective coupling between a single input line and a plurality of output channel lines by means of respective tuned YIG resonators.

What is claimed is:

1. A manifold for microwave energy providing a plurality of frequency selective output signals from a single input signal comprising in combination:

a common input transmission line for microwave energy including means on one end adapted to receive an input signal and means terminating the other end in a predetermined load;

at least three output transmission lines of microwave energy coupled to said input transmission line intermediate the ends thereof;

a ferrimagnetic resonator coupling each of said plurality of 40 outjput transmission lines to said input transmission line;

means generating unidirectional magnetic fields of different intensity through the respective fcrrimagnetic resonators for selectively tuning each resonator so that it is resonant to a selected frequency band of the frequencies included in said input signal and means terminating each of said output transmission lines in a short circuit in proximity to its respective fcrrimagnetic resonator.

2. Apparatus for manifold coupling microwave energy from a common input source to a plurality of output channels comprising in combination:

a first dielectric member; an input strip-transmission line for electromagnetic energy located on one surface of said first dielectric member;

a metallic ground plane having one surface contiguous with the opposite surface of said first dielectric member and having a plurality of apertures therein located in proximi ty to and along the direction of said input strip-transmission line;

a respective ferrimagnetic resonator located in each of said plurality of apertures;

a second dielectric member having one surface contiguous with the opposite surface of said metallic ground plane; a plurality of output strip-transmission lines located on the opposite surface of said second dielectric member traversing a respective aperture of said plurality of apertures substantially at right angles to said input strip-transmission line and having one end thereof terminated in a short circuit connection to said ground plane at a predetermined distance from the respective ferrimagnetic resonator; and

means for establishing unidirectional magnetic fields of dif ferent intensity through the respective ferrimagnetic resonators to establish respectively selected gyromagnetic resonant frequencies in said channels.

3. The invention as defined by claim 2 and wherein said plurality of apertures are comprised of substantially round irises.

4. The invention as defined by claim 2 wherein said ferrimagnetic resonator comprises a sphere of ferrimagnetic material.

5. The invention as defined by claim 4 wherein said ferrimagnetic material comprises a single crystal gamet compound.

6. The invention as defined by claim 4 wherein said ferrimagnetic material comprises yttrium iron garnet.

7. The invention as defined by claim 2 and additionally including a transmission line termination coupled to one end of said input strip-line transmission line.

8. The invention as defined by claim 7 wherein said transmission-line termination comprises impedance coupled from said one end of the input strip-transmission line to a point of reference potential common to said ground plane.

9. The invention as defined by claim 2 wherein said plurality of output strip-transmission lines are substantially mutually parallel to each other.

10. The invention as defined by claim 9 wherein said plurality of substantially parallel output strip-transmission lines have one end thereof extending through said dielectric member.

11. The invention as defined by claim 10 wherein said ferrimagnetic resonator comprises a YlG sphere.

Claims

2. Apparatus for manifold coupling microwave energy from a common input source to a plurality of output channels comprising in combination: a first dielectric member; an input strip-transmission line for electromagnetic energy located on one surface of said first dielectric member; a metallic ground plane having one surface contiguous with the opposite surface of said first dielectric member and having a plurality of apertures therein located in proximity to and along the direction of said input strip-transmission line; a respective ferrimagnetic resonator located in each of said plurality of apertures; a second dielectric member having one surface contiguous with the opposite surface of said metallic ground plane; a plurality of output strip-transmission lines located on the opposite surface of said second dielectric member traversing a respective aperture of said plurality of apertures substantially at right angles to said input strip-transmission line and having one end thereof terminated in a short circuit connection to said ground plane at a predetermined distance from the respective ferrimagnetic resonator; and means for establishing unidirectional magnetic fields of different intensity through the respective ferrimagnetic resonators to establish respectively selected gyromagnetic resonant frequencies in said channels.
3. The invention as defined by claim 2 and wherein said plurality of apertures are comprised of substantially round irises.
4. The invention as defined by claim 2 wherein said ferrimagnetic resonator comprises a sphere of ferrimagnetic material.
5. The invention as defined by claim 4 wherein said ferrimagnetic material comprises a single crystal garnet compound.
6. The invention as defined by claim 4 wherein said ferrimagnetic material comprises yttrium iron garnet.
7. The invention as defined by claim 2 and additionally including a transmission line termination coupled to one end of said input strip-line transmission line.
8. The invention as defined by claim 7 wherein said transmission-line termination comprises impedance coupled from said one end of the input strip-transmission line to a point of reference potential common to said ground plane.
9. The invention as defined by claim 2 wherein said plurality of output strip-transmission lines are substantially mutually parallel to each other.
10. The invention as defined by claim 9 wherein said plurality of substantially parallel output strip-transmission lines have one end thereof extending through said dielectric member.
11. The invention as defined by claim 10 wherein said ferrimagnetic resonator comprises a YIG sphere.