WO1999066584A1

WO1999066584A1 - Ferroelectric phase shifters incorporating ferrite materials

Info

Publication number: WO1999066584A1
Application number: PCT/US1999/013900
Authority: WO
Inventors: Frank S. Barnes
Original assignee: University Technology Corporation
Priority date: 1998-06-19
Filing date: 1999-06-18
Publication date: 1999-12-23
Also published as: AU4826299A

Abstract

An apparatus (100) for altering the velocity of a radio frequency signal generally comprises a first material (114) having an electrically tunable dielectric, and a second material (118) having a magnetically tunable permeability. The permittivity can be adjusted by varying a voltage (V1) applied to the first material, while the permeability of the second magnetic material can be adjusted by varying the strength of a magnetic field applied to the second magnetic material. Furthermore, the apparatus provides a circuit having a characteristic impedance which can be adjusted to match the characteristic impedance of electrical interconnect circuits.

Description

FERROELECTRIC PHASE SHIFTERS INCORPORATING FERRITE MATERIALS

FIELD OF THE INVENTION

The present invention relates generally to electrically tunable devices and specifically to electrically tunable devices utilizing materials having an electrically tunable permittivity and materials having a magnetically tunable permeability. More specifically, the present invention relates to devices utilizing electrically tunable dielectric materials in conjunction with magnetically tunable materials.

BACKGROUND OF THE INVENTION The speed at which an electromagnetic wave travels through a material is dependent in part on the permittivity of that material. Therefore, altering the permittivity of a material can be used to delay an electromagnetic wave in time. This can be understood as a change in the index of refraction of the material. This effect can be beneficially used in devices such as phase shifters and delay lines. However, altering the permittivity of a material also alters the dielectric properties of the material (i.e. the dielectric "constant" is changed when the electrical permittivity is changed). Therefore, changing the permittivity of a material has the effect of changing the capacitance of the material. Devices using voltage tunable material in connection with a thin film dielectric include the phase shifters disclosed in U.S. Patents 5,472,935 and 5,589,845. In such phase shifters, the changes in capacitance can cause the characteristic impedance of the transmission line to change, thereby causing impedance mismatch with the rest of the circuit and thus increased power losses due to reflection of the signal. Additionally, the high capacitance of transmission lines containing dielectric layers can increase conductor losses in the transmission line.

The velocity at which an electromagnetic wave propagates through a material can also be varied by changing the magnetic permeability of the material. This effect can be understood as a change in the index of refraction of the material. Raising the electrical permeability of the material decreases the velocity of an electromagnetic wave through that material. In this instance, the increased magnetic permeability will increase the inductance seen by the wave as it travels through the device. Again, the increased inductance can cause an impedance mismatch between the phase shifting device and the remainder of the electrical circuit. This mismatch decreases the efficiency of the device. SUMMARY OF THE INVENTION It is an objective of the present invention to provide a device and method for tuning a signal (e.g., an RF signal) that can not only rapidly and effectively tune the signal but also can do so without significantly increased insertion losses for the device. Related objectives include providing a device and method for tuning a signal that can use tuning signals of differing frequencies to more effectively tune the signal.

These and other objectives are realized by the various embodiments of the present invention. In a first embodiment, a tunable electronic device is provided for altering a characteristic (i.e., phase, frequency, and/or amplitude) of a signal (e.g., a microwave, millimeter wave, radio waves, and optics). The device includes:

(a) at least two conductors for passing the RF signal;

(b) a gap between said at least two conductors;

(c) a power source electrically connected to said at least two conductors to define a capacitance across the gap; (d) a first material at least a portion of which is located at least one of beside or in the gap such that at least a portion of the RF signal passes through said first material, wherein said first material has a permittivity that is a function of a voltage applied to the first material by the power source; and

(e) a second material at least a portion of which is located at least one of beside or in the gap such that at least a portion of the RF signal passes through said second material, wherein said second material has a permeability that is a function of a magnetic field applied to the second material. The signal can be any signal having an electromagnetic wave.

The conductors can be any suitable material having a relatively low resistivity. Preferred conductors include (a) normal metals, such as gold, silver, and platinum, (b) superconductors, such as Y-Ba-Cu-O (YBCO), Ti-Ba-Ca-Cu-O (TBCCO), Bismuth superconductor and mercury superconductor. The conductors can be arranged in any suitable configuration, including in a coplanar or microstrip configuration.

The gap can be any separation between, discontinuity of, hiatus in, or any other interruption in the conductors). The gap has a preferred width ranging from about 1 to about 100 microns and more preferably from about 20 to about 50 microns. The gap can be a gas(e.g., air)-filled space or a space filled by a material, including the first and/or second materials.

The power source can be any suitable voltage source with a variable voltage source being preferred. The first and second materials can be any suitable electrically tunable material and magnetically tunable material, respectively. The electrically tunable and magnetically tunable materials can be either thin film, thick film, or bulk materials. A thin film material preferably has a thickness of about 1500 angstroms or less, a thick film a thickness ranging from about 1500 angstroms to about 5 microns, and a bulk material a thickness of at least about 1mm. It is preferred that the dielectric material have a dielectric constant which is small, ranging from about 1.5 to about 10 and more preferably less than 50, and that the magnetically tunable material have a large magnetic permeability. To maintain conductor losses to a relatively low level, the electrically and magnetically tunable materials preferably have relatively low loss and delta for the materials themselves. It is important to select the electrically tunable and magnetically tunable materials so that the characteristic impedance of the device (Z₀) matches the characteristic impedance of the remainder of the circuit into which the device is inserted. Reflection losses are substantially minimized by matching the characteristic impedance (Z₀) of the device with that of the remainder of the circuit. Since the characteristic impedance (Z₀) is given by the ratio of the magnetic impedance to the electrical capacitance, altering either of these parameters without altering the other can cause the characteristic impedance of the device to change significantly, thus increasing reflection losses at the location where the tunable element joins the nontunable portion of the circuit. Mathematically, the characteristic impedance is expressed as:

where L is inductance and C is capacitance. Typically, the inductance (L) and capacitance (C) will be electrically connected in parallel in the device. Most microwave circuits have characteristic impedance values between about 10 and about 100 ohms, thus it is advantageous to design the tunable portion of the circuit also to have values in this range so as to minimize the reflection losses. More preferably, the characteristic impedance of the device is at least about 80% and no more than about 120% of the impedance of the remainder of the circuit. Since magnetic inductance is proportional to magnetic permeability and electrical capacitance is proportional to dielectric constant, the change in characteristic impedance and thus reflection losses arising from tuning either the magnetic permeability or dielectric constant can be substantially minimized by also tuning the other property by a similar amount.

The electrically tunable material is a dielectric in which the value of ε can be adjusted. Preferably, the tunable dielectric material is a ferroelectric material, more preferably a paraelectric. The dielectric may be a material selected from the group consisting of barium strontium titanate, barium titanate, strontium titanate (which can collectively be characterized by the equation Sr-Ba_1-xTiO₃, where O≤x≤ 1), potassium tantalate, potassium niobate, lead zirconium titanate, PZT and composites thereof.

The magnetically tunable material is a material in which the value of μ can be adjusted. The magnetic material is preferably a ferrite material and more preferably a magnetic material selected from the group consisting of lithium ferrite, yttrium aluminum ferrite, gadolinium aluminum ferrite, magnesium ferrite, barium ferrite and composites thereof. As used herein, a "ferrite" includes any material having iron in a body-centered cubic form and/or any material containing iron oxide. In the above-noted devices, a radio frequency signal is introduced to one of the conductors. Associated with the radio frequency signal is an electromagnetic wave, portions of which will pass through or adjacent to the gap formed between the conductors. The velocity of the wave's propagation will vary depending on the properties of any material through which it passes. When the electromagnetic wave passes through a dielectric material, it is affected by the permittivity of the material, in addition to other characteristics of the material. When the wave or a portion thereof passes through a magnetic material, it is affected by, among other things, the permeability of that material. By adjusting the permittivity and permeability of material through which the wave passes, the speed of the wave may be altered. The device can be in any number of configurations. In all of these configurations, the first and second materials are located beside (e.g., adjacent or next to) the gap and/or in the gap. Either of the materials can be adjacent to the gap or separated from the gap by another material. Because the strongest electric field, and therefore greatest alteration, in the dielectric constant typically occurs and immediately adjacent to the gap, it is preferred that at least one of the materials, more preferably the first material, be located in or adjacent to the gap. In these various configurations, the second material can be located above the first material or vice versa and the conductors can be located between, on one side of, or on opposing sides of the first and second materials.

In yet another configuration, the device includes a substrate (which can be electrically or magnetically tunable or nontunable) and the second material is located between the first material and the substrate. The substrate preferably has a low loss and a low dielectric constant to substantially minimize the portion of the RF signal passing through the substrate (which is not tuned by the device). The substrate should be selected to provide substantially optimal conditions for deposition of the desired materials on top of the substrate. By way of example, for epitaxially grown films the substrate is selected to provide an excellent lattice match with and thermal coefficient close to that of the film(s).

In a further configuration, the first material has at least a first portion and a second portion. The first portion has a greater dielectric constant than the second portion to provide an asymmetrical electric field in the gap. Preferably, the first portion has a dielectric constant ranging from about 2 to about 20 while the second portion has a dielectric constant ranging from about 10 to about 2500. The first and second portions can have the same or different chemical compositions. The first material can further include a one or more other portions having a different dielectric constant than both the first and second portions. The use of an electrically tunable material in connection with a magnetically tunable material can result in reduced reflection/insertion losses relative to known electrically tunable dielectric devices. In particular, changes in the capacitance of a phase shifter or other electrical device constructed in accordance with the present invention as a result of changes to the permittivity of a material, may be offset by changing the permeability of a material to maintain the characteristic impedance at a desired optimum level. Changing the permeability alters the magnetic inductance of the device. Therefore, the unique combination of such materials allows the speed of propagation of an electromagnetic wave to be adjusted, while maintaining an optimum characteristic impedance for the device.

The combination of electrically and magnetically tunable materials into a common device therefore provides surprising and unexpected improvements in the independent performances of each. As noted, tunable devices using only electrically tunable materials, such as those disclosed in U.S. Patents 5,472,935, 5,721,194; 5,694,134; and U.S. Patent Application Serial os.08/896,688 (filed July 18, 1997); 08/764,173 (filed December 13, 1996); 08/140,770 (filed October 21, 1993); 08/807,334 (filed February 28, 1997); 08/883,653 (filed June 27, 1997); 08/890,721 (filed July 9, 1997), 08/957,793 (filed

October 24, 1997); 09/200,281 (filed November 24, 1998); 09/281,609 (filed March 30, 1999) which are all incorporated by reference herein, and devices using only magnetically tunable materials suffer from undesirable, substantial fluctuations in the characteristic impedance of the device during normal operation. The combination of the two tuning mechanisms in a common device provides heretofore unknown improvements in the performances of such tuning devices.

In another embodiment, a tunable device for altering a characteristic of an RF signal is provided. The device includes:

(a) at least two conductors in a spaced apart relationship to one another such that a gap is formed therebetween;

(b) an electrically tunable dielectric material, at least a portion of which is located at least one of beside and in the gap such that at least a portion of the RF signal passes therethrough, wherein the dielectric constant of said electrically tunable material can be varied by applying a voltage to said electrically tunable material; and (c) a magnetically tunable material, at least a portion of which is located at least one of beside and in the gap such that at least a portion of the RF signal passes therethrough, wherein the magnetic permeability of said magnetically tunable material can be varied by applying a magnetic field to said magnetically tunable material. The device is particularly useful for tuning the phase or the time required for a microwave signal to propagate through a fixed physical length of transmission line. The device can be of a microstrip or coplanar geometry, with at least a portion of the dielectric material and at least a portion of the magnetic material being disposed adjacent to one another.

In yet another embodiment, a device for shifting the phase of a radio frequency signal is provided. The device includes: (a) a dielectric material having a dielectric constant that depends on the magnitude of a voltage applied to the dielectric material;

(b) voltage means (e.g., a power source) for applying a voltage to said dielectric material;

(c) a magnetic material having a magnetic permeability that depends on the strength of a magnetic field applied to the magnetic material;

(d) magnetic field means (e.g., a magnet, a coil, a combination of a magnet and a coil, and the like) for providing a magnetic field to said magnetic material; and

(e) spaced apart conductors for conducting the radio frequency signal. The voltage means for applying a voltage to the dielectric material and magnetic means for applying a magnetic field to the magnetic material can be any number of devices. The voltage means preferably applies a variable voltage to the dielectric material and the magnetic means a variable strength magnetic field to the magnetic material. Tuning of the magnetic permeability is normally accomplished by winding an insulated metal wire into a coil around the magnetic material and passing a current through the wire, or by placing a coil of such wire in the vicinity of the magnetic material. This induces a magnetic field within the volume enclosed by the wire and in areas proximate to the wire. The intensity of the magnetic field can be increased by increasing the current passed through the wire, increasing the number of wire turns which form the coil, or decreasing the volume enclosed by the coils. Alternatively, the magnetic material can be tuned using a permanent magnet.

In yet another embodiment of the present invention, a method of shifting the phase of a radio frequency signal is provided. The method includes the steps of:

(a) passing a first portion of the radio frequency signal through at least a portion of a first material having an electric permittivity that varies according to a voltage applied to the at least a portion of the first material; (b) applying a voltage to the at least a portion of the first material when the first portion passes through the at least a portion of the first material;

(c) simultaneously passing a second portion of the radio frequency signal through at least a portion of a second material having a magnetic permeability that varies according to a magnetic field applied to the at least a portion of the second material; and

(d) applying a magnetic field to said second material when the second portion passes through the at least a portion of the second material. As will be appreciated, these steps can be used in devices having any number of configurations, including those set forth above. To vary the degree of tuning to realize a desired RF output signal, the method can further include, after steps (a)-(d), the steps of:

(e) selecting a second voltage that is different from the voltage;

(f) selecting a second magnetic field that is different from the magnetic field; and (g) repeating step (b) using the second voltage and step (d) using the second magnetic field.

In steps (a)-(d), the method can use control signals of differing frequencies for more effective tuning. By way of example, the voltage corresponds to a first electrical signal having a first frequency and the magnetic field to a second electrical signal having a second frequency. The first frequency is different from the second frequency. As will be appreciated, the selected characteristic of the outputted RF signal is proportional to the sum and difference of the two control signals.

The method and device of the present invention may be used in a variety of devices, including, but not limited to, tunable delay lines, phase shifters, resonators, oscillators, antennas, filters, parametric amplifiers, parametric oscillators, and harmonic generators. More specific applications include in tunable cavities and resonators, tunable frequency and wavelength filters, ferrite thin film isolators, phase shift feed networks for patch antennas, coplanar lines with variable impedance using voltage-tuned meander lines as the center conductor of the coplanar line, tunable resonant antennas, tunable electrically small antennas, tunable, and one-dimensional confocal (i.e., having the same focus) resonators which can provide higher Q. Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is an end on cross sectional view of a tunable device according to a another embodiment of the present invention;

Fig. 2 is a side view of the device of Fig. 1;

Fig.3 illustrates the interaction of the electromagnetic wave of the radio frequency signal and the magnetic field of a magnetic material;

Fig.4 is an end on cross sectional view of a tuning device according to yet another embodiment of the present invention;

Fig. 5 is an end on cross sectional view of a tuning device according to an additional embodiment of the present invention; Fig. 6 is a top view of a tuning device according to an additional embodiment of the present invention;

Fig. 7 is a top view of a tuning device according to yet another embodiment of the present invention;

Fig. 8 is an end on cross sectional view of a tuning device according to an embodiment of the present invention;

Fig. 9 is an end on cross sectional view of a tuning device according to an embodiment of the present invention;

Fig. 10 is an end on cross sectional view of a tuning device according to an embodiment of the present invention; Fig. 11 is an end on cross sectional view of a tuning device according to an embodiment of the present invention;

Fig. 12 is an end on cross sectional view of a tuning device according to an embodiment of the present invention;

Fig. 13 is an end on cross sectional view of a tuning device according to an embodiment of the present invention; Fig. 14 is an end on cross sectional view of a tuning device according to an additional embodiment of the present invention;

Fig. 15 is a top view of a tuning device according to yet another embodiment of the present invention; Fig. 16 is a side sectional view of the embodiment of Fig. 15;

Fig. 17 is an end on cross sectional view of a tuning device according to an embodiment of the present invention;

Fig. 18 is an end on cross sectional view of a tuning device according to an embodiment of the present invention; and Fig. 19 is an end on cross sectional view of a tuning device according to an embodiment of the present invention.

DETAILED DESCRIPTION The addition of a high-permeability material to a voltage-tunable ferroelectric phase shifter can greatly improve the performance of the phase shifter. The basic derivation of this approach is as follows. For the propagation of electromagnetic waves, the distance d traveled by the wave in a time t is given by

d = v x t

where v is the velocity of the wave. In a homogeneous media, the velocity is given by

v = l/(με)^,/j

where μ is the magnetic permeability and G is the dielectric permeability. Thus,

t = d(με)^H

and

Δt = ¹/₂d[( /ε)¹²Δε+(ε/μ) Δμ] The phase shift is given by

ΔΦ=ωΔt

where ω is the angular frequency and ΔΦ is the phase shift obtained by applying a voltage to the ferroelectric material. Here it is clearly seen that increasing μ from its normal value for free space increases the phase shift as the square root of μ. Since values of μ may be much larger than that of free space, if a μ of 900 is attained, for example, an increase of 30 times ΔΦ in bulk material may be obtained with little increase in the loss. YIG is shown to have this value of μ at frequencies up to about 1 GHz. Higher values of μ occur near resonance, at the expense of increased losses. In a coplanar line structure, as shown in Fig. 6, this value is reduced by a filling factor which will depend on the fraction of the magnetic field which goes through the ferrite film. Where the effective value of μ is tuned with an external magnetic field, a term is added to the phase shift equation to yield the following:

ΔΦ = ωΔt = ^,/₂ωd[(μ/ε)¹²Δε + (ε/μ)^1/2 Δμ]

It is also to be noted that, if a magnetic field is at an angular frequency ω and an electric field is at an angular frequency ω, a phase shift which is proportional to the product of the frequencies can be obtained. In addition, a microwave output that is proportional to the product of the voltage across the material and the magnetic field can be generated by modulating the losses in the ferrite and the losses in the ferroelectric material independently. An embodiment of the device of the present invention is illustrated in cross section in Fig. 1. A side elevation of the device of Fig. 1 is shown in Fig. 2. The tunable electronic device of Figs. 1 and 2, identified generally as electronic device 100, is comprised of two conductors 104 and 108. The conductors 104 and 108 are separated by a gap 112. A material with electrically tunable permittivity 114 and a material with a magnetically tunable permeability 118 are located within the gap 112. A coil 122 of conductive wire, electrically connected to a current source I_t is wrapped about a horseshoe magnet 126, positioned so that its magnetic field passes through the material having a tunable permeability 118. Voltage source V_x is electrically connected to the conductors 104 and 108. When used as a phase shifter, the tunable electronic device 100 will have a radio frequency signal 204 introduced at a first end. As the radio frequency signal 204 propagates along the conductor 104, the electromagnetic wave associated with the signal will cross at least portions of the material having a tunable permeability 118, and the material having a tunable permittivity 114. Accordingly, the speed of the wave, and therefore the radio frequency signal, can be adjusted by altering the permeability of the material having a tunable permeability 118 and by altering the permittivity of the material having a tunable permittivity 114. The phase shifted radio frequency wave 208 exits the device 100 at a second end, opposite the one into which the radio frequency wave 204 entered the device 100.

The tuning of the material having an adjustable permeability 118 is accomplished by passing a magnetic field through the material. In the embodiment illustrated in Figs. 1 and 2, the magnetic field is generated by a horseshoe magnet 126. The strength of the magnetic field from the horseshoe magnet can be altered by passing a current through the coil of conductive wire 122. The strength of the magnetic field introduced to the material 118 can be increased by increasing the current passed through the coil 122 or decreased by decreasing that current. Fig. 3 illustrates the relationship between the electromagnetic wave 300, the associated radio frequency signal 204, the conductor 104, and the magnetic field 304. Generally, to achieve the largest effect on the electromagnetic wave 300 for a given change in the current l it is preferable that the magnetic field 304 be orthogonal or perpendicular to the radio frequency signal 204. This configuration allows the magnetic field 304 to have the greatest effect on the electromagnetic wave 300. Other configurations may be used, i.e., the magnetic field 304 may be at a non-zero angle to the electromagnetic wave 300, however, a given change in the strength of the magnetic field 304 will have a lesser effect on the speed of the wave 300 through the device in such a configuration. Referring again to Fig. 1, the permittivity of the dielectric material 114 may be adjusted by adjusting the magnitude of a voltage supplied by source V_x to the material 114 through conductive wires 130. Generally, increasing the voltage applied to the dielectric material 114 will decrease the permittivity of that material, while decreasing the voltage increases the permittivity. Increasing the permittivity of the material 114 will decrease the velocity that the electromagnetic wave 300 associated with the radio frequency signal 204 passes through the material 114.

As described above, changing the permeability of the magnetically tunable material 118 changes the magnetic inductance (L) of the tunable electronic device 100. Similarly, changing the permittivity of the electrically tunable dielectric 114 changes the capacitance seen by a radio frequency signal 204 introduced to the tunable electronic device 100. The inductance (L) and capacitance (C) of a circuit determine that circuit's characteristic impedance (Z₀) As set forth above, the characteristic impedance (Z₀) equals the square root of L/C. The impedance of the bulk material is given by the square root of μ/ε. Therefore, by careful balancing of the relative permeability and permittivity of the material 118 and 114, and hence the relative magnetic inductance and capacitance of the device 100, the impedance of a device constructed in accordance with the present invention can be controlled. Therefore, the present invention provides a method and device for altering the velocity of a radio frequency signal while at the same time allowing the impedance of the device to be matched to the overall characteristic impedance of the circuit. Matching the impedance of circuit elements limits power losses in a circuit. Therefore, the present invention limits power losses from the radio frequency signal 204.

The voltage supplied by voltage source V- to the tunable dielectric material 114 may be controlled by a controller 134. The magnetic field applied to the magnetically tunable material 118 may also be controlled by the controller 134, which can be used to vary the current supplied to the coil 122 by current source I-. The connection between the controller 134 and the voltage source V_x is represented by a first control signal line

138. The connection between the controller 134 and the current source Ii is represented by a second control signal line 142. The controller 134 can comprise a digital logic circuit that includes a look-up table. The look-up table generally includes data regarding the voltage to be applied to the electrically adjustable material 114 and the current to be supplied to coil 122, and thus the strength of the magnetic field applied to magnetically adjustable material 118, to achieve a certain phase shift in a radio frequency signal 204 while maintaining a desired characteristic impedance of the device 100. The controller 134 may also vary the signals directed to the voltage source V- and the current source I_x depending on the frequency of the incoming signal 204. In another embodiment, the controller 134 varies only the voltage supplied by V- to the dielectric. In addition, the voltage applied to the electrically adjustable material 114 can have a frequency/ and magnetic field applied to the magnetically adjustable material 118 can have a frequency/. This results in a multiplication of the frequencies/ and/ according to the following formula: cos(a)*cos(b)=l/2[cos(a+b)+cos(a-b)] Thus it can be seen that, where a is the frequency term of the applied voltage and b is the frequency term of the magnetic field, two signals at different frequencies result.

The electrically adjustable material 114 may be any material having the characteristic of an adjustable dielectric strength. For example, the electrically adjustable material 114 may be a ferroelectric material. The magnetically tunable material 118 may be any material having an adjustable permeability. For example, the magnetically tunable material 118 may be a ferrite. It should be noted that the material having an electrically adjustable permittivity 114 may be the same as the material having a magnetically adjustable permeability 118. All that is required is two discrete portions of material where one of the discrete portions has an electrically adjustable permittivity, and the second discrete portion has a magnetically adjustable permeability. Therefore, a material that had both of these qualities could be used in each of the discrete portions.

With respect to the geometry of the device, the present invention includes devices having distributed capacitances, and devices having lumped capacitances. The tuning effect achieved by the tunable materials is maximized when a large portion of the electromagnetic wave of the radio frequency signal passes through the tunable materials.

Therefore, it is generally preferable that the tunable materials be located within or proximate to the gap or gaps defined between the center or main conductor of the device, and the ground plane or planes. The device may also be constructed using a variety of techniques. Accordingly, the device may be constructed using thin films of the described materials, by using bulk materials, or by a combination of thin film and bulk materials.

Where a devices is to be constructed using deposition techniques, it is important that the materials used be compatible. As an example, the ferromagnetic material barium strontium titanate may serve both as a substrate and a magnetically tunable material. A center conductor and one or more ground conductors may be deposited in the form of a conductor metal on top of the substrate. A ferrite layer can then be grown on top of the substrate and the conductors.

Another embodiment of the present invention is illustrated in Fig. 4. According to this embodiment, the device 400 features a magnetically tunable substrate 404, which may be comprise a ferrite material. Deposited on a surface of the substrate 404 is a center conductor 408 and ground planes 412. The center conductor 408 and ground planes 412 may be made from any electrically conductive material, including a superconducting material. An electrically tunable material 416 is deposited in a layer over and between the center conductor 408 and the ground planes 412. The electrically tunable material 416 may comprise a dielectric material, such as a paraelectric or a ferroelectric. A magnetically tunable material 420, for example a ferrite, is deposited over the electrically tunable material 416.

Although the description of the device 400 illustrated in Fig. 4 is in terms of thin film materials, the device 400 may also be constructed from bulk materials. In constructing the device 400, it is preferable that the materials other than the center conductor 408 and the ground planes 412 have a high impedance. As with all of the other embodiments of the present invention, the permittivity of the electrically tunable material 416 may be adjusted by applying a voltage to the material 416. Also as with all of the other described embodiments of the present invention, the permeability of the magnetically tunable material 420 may be adjusted by directing a magnetic field through the magnetically tunable material 420. The magnetic field may be created through magnetic means such as a permanent magnet in the proximity of the magnetically tunable material 420, or by an electrical current sent through a coil of wire placed in the proximity of the material 420.

An additional embodiment of the present invention is illustrated in Fig. 5. In this embodiment the device 500 includes a magnetically tunable substrate 504. The substrate 504 may be constructed of a ferrite material. A first layer of electrically tunable dielectric material 508 is deposited on top of the magnetically tunable substrate 504. On top of this first layer of dielectric material 508 is a center conductor 512, and ground planes 516. The center conductor and the ground planes 516 maybe constructed from any electrically conductive material. A second dielectric layer 520 is then deposited over and between the center conductor 512 and the ground planes 516. Referring now to Fig. 6, a top view of another embodiment of the present invention, identified as device 600, is illustrated. According to this embodiment, the positive pole of voltage source V_x is electrically connected by a first wire 604 to two ground planes 608, and the negative pole is electrically connected by a second wire 612 to a center conductor 616. The voltage source Vj therefore applies an electrical potential to the electrically tunable dielectric material 620 deposited between and below the ground planes 608 and the center conductor 616. The permittivity of the dielectric material 620 may be varied by varying the voltage supplied to it by voltage source W

The embodiment illustrated in Fig. 6 also includes a wire coil 624, which is supplied with an electrical current by current source l_γ. The coil 624 overlays the device 600, and introduces a magnetic field to the device. The magnetic field may be used to adjust the permeability of a ferrite substrate (not shown).

As described above, the voltage supplied by the voltage source Vj may have a frequency/, and the current supplied to the coil 624 may have a frequency/. Therefore the device may be used to effect a frequency multiplication of/ and/. As with all the other embodiments of the present invention, the electrically tunable material 620 and the magnetically tunable material may be adjusted to create a phase shift in a radio frequency signal 628 passed through the device. Also as with all the other embodiments of the present invention, the impedance presented by the device 600 to the circuit supplying the radio frequency signal 628 can be adjusted to match the impedance of that supply circuit, minimizing losses in the power of the signal 628 introduced by the device 600. The amount of voltage and of current needed to match the impedance of the connecting circuitry to the device 600 may be determined and controlled by controller 632.

With reference now to Fig. 7, an embodiment of the present invention is generally identified as device 700. The device 700 generally includes ground planes 704 and a center conductor 708. Interspersed between the conductive ground planes 704 and the center conductor 708 is a dielectric material 712. A voltage source V_t is electrically connected to the ground planes 704 and the center conductor 708. Therefore, as with the embodiment of Fig. 6, the permittivity of the dielectric material 712 of device 700 may be adjusted by selectively applying a voltage through voltage source V_x . The means for supplying a magnetic field to the device 700 comprises a horseshoe magnet 716, placed about the device 700. The magnetic field may be used to alter the permeability of a ferrite, magnetically tunable material (not shown) comprising a layer of the device 700. The magnitude of the magnetic field may be varied by varying the electrical current supplied to a coil 720 by a current source I_x. The voltage supplied by V_x and the current supplied by I_x may be controlled by a digital controller or controllers (not shown). In an alternative embodiment, the magnetic field introduced to a device constructed in accordance with the present invention may be supplied by a permanent magnet, such as a bar magnet. According to such an embodiment, the strength of the magnetic field used to adjust the permeability of a magnetically tunable material may be varied by changing the distance between a pole of the bar magnet and the magnetically tunable material. This embodiment may include a voltage source interconnected to a dielectric to change the permittivity of the dielectric material.

An additional embodiment of the present invention is illustrated in Fig. 8, and is generally identified as device 800. The device 800 includes substrate 804, supporting center conductor 808 and ground planes 816. Between and above the center conductor 808 and the ground planes 816 is a material having an electrically adjustable permittivity

820, which may be a ferroelectric material. Overlaying the ferroelectric layer 820 is a material having a magnetically adjustable permeability 824, which may be a ferrite.

An additional embodiment of the invention is illustrated in Fig. 9 and identified generally as device 900. The device 900 has a first layer 904 having an electrically adjustable permittivity. The first layer 904 may be made from a ferroelectric material. In the device 900, the material 904 is a bulk material. Placed on top of the first layer 904 is center conductor 908, and ground planes 912. Forming a sandwich type construction, a second layer 916 having a magnetically adjustable permeability, completes the device 900. Therefore, it can be seen that the device of the present invention may be constructed from bulk materials. A further embodiment of the device of the present invention is illustrated in Fig. 10 and is generally identified as device 1000. The device 1000 includes a ferrite substrate 1004 having a magnetically tunable permeability. Layered on top of the substrate 1004 is a first ferroelectric layer 1008. The first dielectric layer 1008 may have a low dielectric constant, and a voltage tunable permittivity. Directly above the first ferroelectric layer

1008 is second ferroelectric layer 1012. The second ferroelectric layer 1012 may have a high dielectric constant, and the permittivity of the material may also be voltage adjustable. Center conductor 1016 and ground planes 1020 are deposited on top of the second ferroelectric layer 1012. The device 1000 is completed by the addition of a third ferroelectric layer 1024 deposited between and on top of the center conductor 1016 and ground planes 1020. The third ferroelectric layer 1024 may have either a high or low dielectric constant, and the permittivity of the material may be voltage adjustable.

A further embodiment of the device of the present invention identified as device 1100 is illustrated in Fig. 11. The device 1100 includes a ferrite substrate 1104, having a magnetically tunable permeability. Layered on top of the substrate 1104 is a first dielectric material 1108. Directly on top of the first dielectric material 1108 are the center conductor 1112 and the ground planes 1116. Deposited above and between the center conductor 1112 and the ground planes 1116 is a second ferroelectric layer 1120. Both the first dielectric layer 1108 and the second layer 1120 may be provided with voltage tunable permittivities. According to this embodiment, the first dielectric 1108 may have a low dielectric constant, while the second dielectric 1120 may have a high dielectric constant.

Still another embodiment of the device of the present invention is illustrated in Fig. 12 and identified as device 1200. The device 1200 may be provided with a non-tunable substrate 1204. Alternatively, the substrate 1204 may have an adjustable permittivity or permeability. On top of the substrate 1204 a center conductor 1208 and conductive ground planes 1212 are deposited. Layered above and between the center conductor 1208 and the ground planes 1212 is ferroelectric layer 1216. The ferroelectric layer 1216 may have an electrically adjustable permittivity. Layered above the dielectric 1216 is a ferrite 1220 having a magnetically tunable permeability. An additional embodiment of the device of the present invention is illustrated in Fig. 13 and identified generally as device 1300. Device 1300 includes substrate 1304, which may have a tunable permeability or permittivity, or may be non-tunable in those respects. Above the substrate 1304 is a ferrite layer 1308 having an electrically tunable permittivity. Above the ferrite 1308 is a center conductor 1312 and ground planes 1316.

Above and between the center conductor 1312 and the ground planes 1316 is ferroelectric layer 1320. The top ferroelectric layer 1320 may have the property of an electrically tunable dielectric.

A further embodiment of the present invention, illustrated in Fig. 14, is generally identified as device 1400. The device 1400 is a layered construction with a substrate 1404 constructed from a non-tunable material, or alternatively from a material having a tunable permeability or a tunable permittivity. On top of the substrate 1404 is a layer of ferroelectric material 1408, which has an electrically tunable permittivity. On top of the ferroelectric material 1408 is a center conductor 1412 and ground planes 1416. As with the other embodiments of the device, the center conductor 1412 and/or the ground planes

1416 may be constructed from any conducting or superconducting material. Filling the gaps between the center conductor 1412 and the ground planes 1416, and overlaying those structures is a material having a magnetically tunable permeability 1420, such as a ferrite. Fig. 15 is a side view of a device according to a further embodiment of the present invention, identified as device 1500. Fig. 16 is a top view of the device of Fig. 15. The device includes ground planes 1510a,b, center conductor 1514, magnetically tunable material 1518 and 1520, and electrically tunable dielectric material 1522. Ground planes 1510a,b and center conductor 1514 can be composed of any highly conductive material, including normal conductors, such as gold, and superconductors, such as YBCO. The magnetically tunable material 18 is a bulk material that serves as a substrate for supporting the other components of the device. The magnetically tunable material 1520 and the electrically tunable dielectric material 1522 are preferably thin film materials. Voltage means V_x (depicted schematically in Fig. 15) is electrically connected to the electrically tunable dielectric material 1522 through ground planes 1510a and/or b and the center conductor 1514. Magnetic means 1524 is magnetically connected to the magnetically tunable material 1518 and/or 1520 to provide tuning of the radio frequency signal propagating through the device. The magnetic means 1524 may be any structure capable of generating a magnetic field, such as a current through a coil of conductive wire or a permanent magnet. In operation, the radio frequency signal 1525 propagates through the device from the input end 1526 of the device to the output end 1530. A capacitance exists on either side of the center conductor 1514 with respect to each of the ground planes 1510a,b. On each side of the center conductor 1514, a first portion of the capacitance is across the magnetically tunable material 1518, a second portion is across the magnetically tunable material 1520, and a third portion is across the dielectric material 1522. Separate portions of the radio frequency signal pass through the magnetically tunable materials 1518 and 1520 and the dielectric material 1522 such that the first, second and third capacitances on either side of the center conductor 1514 are electrically connected in parallel. In this manner, the total capacitance can be varied by selectively varying the first, second and/or third capacitances and thereby tuning the radio frequency signal. Furthermore, the magnetically tunable material 1518 and 1520 present an inductive load to the radio frequency signal. As described above, balancing the capacitances of the ferroelectric material with the inductance of the ferrite material allows the characteristic impedance of the device 1500 to be matched to the connecting circuits. An embodiment of the present invention having a microstrip configuration is illustrated in Figure 17. The microstrip device is generally identified as device 1700. The device includes a substrate 1704, which is preferably a ferrite material having a magnetically tunable permeability. Underlaying the substrate 1704 is ground plane 1708. The ground plane 1708 maybe constructed of any electrical conductor or superconductor. On top of the substrate 1704 is center conductor 1712. The center conductor may also be constructed from any electrically conductive material such as a metal or a superconductor. Layered over the center conductor 1712 and the substrate 1704 is a layer of material having an electrically tunable permittivity 1716. Overlaying the electrically tunable layer 1716 is a layer of magnetically tunable material 1720. Encasing the top, bottom and sides of the device is a material having a magnetically tunable permeability

1724. Figure 18 illustrates an embodiment of the device of the present invention wherein the impedance experienced by the electromagnetic wave is symmetrical about the conductors. This device, identified generally as device 1800 includes a substrate 1804 whose permeability is magnetically tunable. On top of the magnetically tunable substrate 1804 is a material having an electrically tunable permittivity 1808, which is a first dielectric layer. On top of the first dielectric layer 1808 is a center conductor 1812 and ground conductors 1816. Overlaying the semiconductor 1812, the ground planes 1816, and the first dielectric layer 1808 is a second dielectric layer 1820. Like the first dielectric layer 1808, the second dielectric layer 1820 has an electrical permittivity that can be electrically adjusted. On the top layer is a magnetically tunable material 1824, which like the substrate 1804 has a permeability that can be tuned by the application of a magnetic field.

In figure 19 another embodiment of the present invention having a symmetrical impedance is illustrated, and is identified generally as device 1900. The device 1900 may include a substrate 1904, which may be a low dielectric material, a tunable material, or a non-tunable material. Overlaying the substrate 1904 is a magnetically tunable material 1908. The magnetically tunable material 1908 is tunable in that its permeability may be adjusted by the application of a magnetic field to that material. On top of the magnetically tunable layer 1908 is a first dielectric layer 1912 having a permittivity that is electrically adjustable. On top of the first dielectric layer 1912 is a center conductor 1916 and ground planes 1920. Overlaying the center conductor 1916, the ground planes 1920, and the first dielectric layer 1912, is a second dielectric layer 1924. As with the first dielectric layer 1912, the second dielectric layer 1924 has a permittivity that can be electrically adjusted. Specifically, the permittivity of these materials can be adjusted by the application of a voltage to them. Overlaying the second dielectric layer 1924 is the second magnetically tunable layer 1928.

The devices of the present invention can be used as bandpass and band reject filters, resonators, phase shifters, delay lines, correlators, and comparators.

The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent peπnitted by the prior art.

Claims

What is claimed is:

1. A tunable electronic device for altering a characteristic of a signal, comprising: at least two conductors for passing the signal; a gap between said at least two conductors; a power source electrically connected to said at least two conductors to define a capacitance across the gap; a first material at least a portion of which is located at least one of beside or in the gap such that at least a portion of the signal passes through said first material, wherein said first material has a permittivity that is a function of a voltage applied to the first material by the power source; and a second material at least a portion of which is located at least one of beside or in the gap such that at least a portion of the signal passes through said second material, wherein said second material has a permeability that is a function of a magnetic field applied to the second material.

2. The tunable electronic device of Claim 1, wherein the second material is located above the first material.

3. The tunable electronic device of Claim 2, further comprising a substrate located below the at least two conductors and the first and second materials.

4. The tunable electronic device of Claim 1, wherein the at least two conductors are located between the first and second materials.

5. The tunable electronic device of Claim 1, wherein the first material is contained in the gap.

6. The tunable electronic device of Claim 1, wherein the second material is located between the first material and a substrate.

7. The tunable electronic device of Claim 1 , wherein the first material includes at least a first portion and a second portion, the first portion having a greater dielectric constant than the second portion.

8. The tunable electronic device of Claim 7, wherein the first and second portions have different chemical compositions.

9. The tunable electronic device of Claim 7, wherein the first material includes a third portion having a different dielectric constant than the first and second portions.

10. The tunable electronic device of Claim 1, wherein the first material is selected from the group consisting of a paraelectric and a ferroelectric material.

11. The tunable electronic device of Claim 1, wherein the first material is selected from the group consisting of barium strontium titanate, barium titanate, strontium titanate, potassium tantalate, potassium niobate, lead zirconium titanate, and mixtures thereof.

12. A tunable device for altering a characteristic of a signal, comprising: at least two conductors in a spaced apart relationship to one another such that a gap is formed therebetween; an electrically tunable dielectric material, at least a portion of which is located at least one of beside and in the gap such that at least a portion of the signal passes therethrough, wherein the dielectric constant of said electrically tunable material can be varied by applying a voltage to said electrically tunable material; and a magnetically tunable material, at least a portion of which is located at least one of beside and in the gap such that at least a portion of the signal passes therethrough, wherein the magnetic permeability of said magnetically tunable material can be varied by applying a magnetic field to said magnetically tunable material.

13. The tunable radio frequency phase shifting device of Claim 12, wherein said magnetically tunable material is a ferrite.

14. The tunable radio frequency phase shifting device of Claim 12, wherein said electrically tunable material is a ferroelectric.

15. The tunable radio frequency phase shifting device of Claim 12, further comprising an electric current loop to produce said magnetic field.

16. The tunable radio frequency phase shifting device of Claim 12, further comprising a magnetic material to produce said magnetic field.

17. A method of shifting the phase of a signal, comprising:

(a) passing a first portion of the signal through at least a portion of a first material having an electric permittivity that varies according to a voltage applied to the at least a portion of the first material; (b) applying a voltage to the at least a portion of the first material when the first portion passes through the at least a portion of the first material;

(c) simultaneously passing a second portion of the signal through at least a portion of a second material having a magnetic permeability that varies according to a magnetic field applied to the at least a portion of the second material; and

(d) applying a magnetic field to said second material when the second portion passes through the at least a portion of the second material.

18. The method, as claimed in Claim 17, further comprising, after steps (a)-(d), the steps of: selecting a second voltage that is different from the voltage; selecting a second magnetic field that is different from the magnetic field; and repeating step (b) using the second voltage and step (d) using the second magnetic field.

19. The method, as claimed in Claim 18, wherein the voltage corresponds to a first electrical signal having a first frequency and the magnetic field to a second electrical signal having a second frequency and the first frequency is different from the second frequency.

20. A device for shifting the phase of a signal, comprising: a dielectric material having a dielectric constant that depends on the magnitude of a voltage applied to the dielectric material; voltage means for applying a voltage to said dielectric material; a magnetic material having a magnetic permeability that depends on the strength of a magnetic field applied to the magnetic material; magnetic field means for providing a magnetic field to said magnetic material; and spaced apart conductors for conducting the radio frequency signal.

21. The device of Claim 20, further comprising a substrate and wherein the substrate has an impedance that is more than the impedance of the dielectric material, magnetic material, and spaced apart conductors.

22. The device of Claim 20, further comprising a substrate and wherein the substrate includes at least a portion of the magnetic material.

23. The device of Claim 20, further comprising a substrate and wherein the substrate includes at least a portion of the dielectric material