Patent Publication Number: US-6216020-B1

Title: Localized electrical fine tuning of passive microwave and radio frequency devices

Description:
This is a continuation-in-part application out of U.S patent application Ser. No. 08/656,537, filed May 31, 1996, now abandoned. 
    
    
     This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The Government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the things of passive microwave and RF devices, and, more specifically to localized electrical fine tuning of these devices. 
     BACKGROUND OF THE INVENTION 
     Often, in applications involving microwave/RF circuitry, it is necessary to tune the electrical characteristics of certain parts of the circuitry after it has been manufactured. Actually, with high-performance devices, such as high-Q microwave/RF resonators and several-pole microwave/RF filters, continual fine tuning often is required even after the initial tuning. Currently, both the initial tuning, and the subsequent fine tuning are achieved almost exclusively by mechanical means such as tuning screws, or by adding or removing wire-bonding from tuning pads placed on critical parts of the circuitry. This mechanical tuning is time consuming, and is found to be lacking in the area of controllability, accuracy and resolution. 
     Bulk ferrite materials also have been utilized for magnetically tunable microwave devices whose response can be tuned by applying a dc magnetic field. However, tunable and adaptive devices incorporating ferrites so far have had limited use due to their high unit cost, complexity, large size, high insertion loss, and low tuning speed. 
     The invention disclosed herein is related loosely to two previous issued to the inventor herein. These patents are: U.S. Pat. No. 5,538,941, issued Jul. 26, 1996, for SUPERCONDUCTOR/INSULATOR METAL OXIDE HETEROSTRUCTURE FOR ELECTRICALLY TUNABLE MICROWAVE DEVICES; and U.S. Pat. No. 5,604,375, issued Feb. 18, 1997, for SUPERCONDUCTING ACTIVE LUMPED COMPONENT FOR MICROWAVE DEVICE APPLICATION. 
     If possible, a way of tuning circuitry electrically which could be implemented in conventional planar microwave and RF circuitry with minimal modification in design and with negligible pertubation of device performance would be far superior to the conventional tuning regimes of the prior art. Tuning circuitry electrically also could provide a convenient means for adding adaptive features to the operation of the tuned device. 
     Electrical tuning of microwave/RF circuitry does provide many advantages over both mechanical and magnetic tuning. Among these advantages are convenience, reproducibility, controllability, versatility, speed, accuracy, resolution and adaptability. The method according to the present invention uses electric field induced changes in the permittivity of certain nonlinear dielectric thin film under specific bias configurations to effect electrical fine tuning of microwave/RF circuitry. The broad class of materials known as nonlinear dielectrics possess many characteristics which make them suitable for this application. Among these characteristics are high peak power capacity, short switching times, broadband capability, and easy integration into monolithic microwave/RF devices. 
     It is therefore an object of the present invention to provide apparatus and method for the localized electrical fine tuning of passive microwave and RF devices through local manipulation of the shunt and series capacitance of the devices. 
     It is another object of the present invention to provide apparatus and a general-purpose method for localized electrical fine tuning of conventional passive microwave and RF devices which provides improved speed, reproducibility and accuracy, without significant degradation of device performance. 
     It is yet another object of the present invention to provide apparatus and method for localized electrical fine tuning of conventional passive microwave and RF devices that can be incorporated into the devices either at the time of manufacture or after manufacture of the devices. 
     Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the combinations particularly pointed out in the appended claims. 
     SUMMARY OF THE INVENTION 
     To achieve the foregoing and other objects, a method of localized electrical fine tuning of a passive microwave or RF multiple element devices on a substrate, through the localized manipulation of either its shunt or series capacitance, comprising the steps of depositing nonlinear dielectric material onto a plurality of predetermined areas of the substrate in electrical contact with each of the multiple elements; depositing electrically conductive material onto a plurality of predetermined areas of the dielectric material and of the substrate, and forming electrodes; and applying individual, adjustable bias voltages to the electrodes. 
     In another aspect of the present invention there is provided an electrically fine tunable passive microwave or RF multiple element device comprising a multiple element passive microwave or RF device on a substrate with a nonlinear dielectric material on predetermined areas of the substrate and in electrical contact with each of the multiple elements. An electrically conductive material is on predetermined areas of the dielectric material and the substrate, and forms electrodes, with individual, adjustable bias voltages to applied to the electrodes. 
     In yet another aspect of the present invention there is provided a method of providing localized electrical fine tuning to a previously manufactured multiple element passive microwave or RF device on a substrate comprising the steps of depositing nonlinear dielectric material onto a plurality of predetermined areas of the substrate and in electrical contact with the multiple elements; depositing electrically conductive material onto a plurality of predetermined areas of the dielectric material and of the substrate, and forming electrodes; and applying individual, adjustable bias voltages to the electrodes. 
     In still another aspect of the present invention there is provided a method of manufacturing a multiple element passive microwave or RF device that provides localized electrical fine tuning comprising the steps of depositing an electrically conductive material onto a substrate at a plurality of predetermined positions to form multiple elements for the passive microwave or RF device desired; depositing nonlinear dielectric material onto the substrate at a plurality of predetermined areas and in electrical contact with each of the multiple elements; depositing electrically conductive material onto a plurality of redetermined areas of the dielectric material and of the substrate, and forming electrodes; and applying individual, adjustable bias voltages to the electrodes. 
     In still another aspect of the present invention there is provided an electrically fine tunable microwave or RF device comprising a multiple element passive microwave or RF device on a substrate with first contact pads and first resistive and inductive lines in electrical contact located at predetermined areas of the substrate, each of the first resistive and inductive lines terminating in a capacitive plate located a predetermined distance from a first end of each of the multiple elements. Second contact pads and second resistive and inductive lines are in electrical contact and are located at predetermined areas of the substrate, the second resistive and inductive line terminating in electrical contact with a second end of each of the multiple elements. A nonlinear dielectric material is deposited onto predetermined areas of the first end of each of the multiple elements and each of the capacitive plates, and individual, adjustable bias voltages are connected to each of the first and second contact pads. 
     In still another aspect of the present invention there is provided a method of providing localized electrical fine tuning to a previously manufactured multiple element passive microwave or RF device on a substrate comprising the steps of depositing a plurality of first contact pads and a plurality of first resistive and inductive lines onto predetermined areas of the substrate, each of the plurality of first contact pads and each of the plurality of first resistive and inductive lines being in electrical contact, with each of the first resistive and inductive lines terminating in a capacitive plate located at a predetermined distance from a first end of each of the multiple elements; depositing a plurality of second contact pads and a plurality of second resistive and inductive lines onto predetermined areas of the substrate, each of the plurality of second resistive and inductive lines terminating in electrical contact with a second end each of the multiple elements; depositing a plurality of nonlinear dielectric films onto predetermined areas of the first end of each of the multiple elements and each of the plurality of capacitive plates; and applying a plurality of individual, adjustable bias voltages between each of the pluralities of first and second contact pads. 
     In a still further aspect of the present invention there is provided a method of manufacturing a multiple element passive microwave or RF device that provides localized electrical fine tuning comprising the steps of depositing an electrically conductive material onto a substrate at a plurality of predetermined positions to form multiple elements for the passive microwave or RF device desired; depositing a plurality of first contact pads and a plurality of first resistive and inductive lines onto predetermined areas of the substrate, each of the plurality of first contact pads and each of the first resistive and inductive lines being in electrical contact, and each of the first resistive and inductive lines terminating at a predetermined distance from a first end of each of the multiple elements; depositing a plurality of second contact pads and a plurality of second resistive and inductive lines onto the substrate, each of the plurality of second contact pads and each of the second resistive and inductive lines being in electrical contact, and each of the second resistive and inductive lines terminating in electrical contact with a second end of each of the multiple elements; depositing a plurality of nonlinear dielectric films onto predetermined areas of the first end of each of the multiple elements and each of the capacitive plates; and applying a plurality of individual, adjustable bias voltages between each of the first and second contact pads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a schematical illustration of one embodiment of the present invention in which a conventional multi-pole coplanar waveguide filter device structure is modified with gaps in the groundplanes which do not significantly perturb the microwave performance but allow for low-frequency fine-tuning of different areas of the device independently. 
     with: 
     FIG. 1 is a schematical illustration of one embodiment of the present invention that allows independent low-frequency fine tuning of different areas of the device. 
     FIG. 2 is a top view of a coplanar waveguide, the cross-section of which is illustrated in FIG. 1, clearly showing the arrangement of an arbitrary number of groundplanes positioned at predetermined locations of the nonlinear dielectric layer and showing the gaps between each groundplane and between the groundplanes and the device&#39;s centerline. 
     with: 
     FIG. 2 is top view of the device illustrated in FIG. 1 clearly showing arrangement of the groundplanes. 
     FIG. 3 is a schematic illustration of the electrical configuration of the coplanar waveguide illustrated in FIGS. 1 and 2 showing electrical lengths as well as coupling capacitances which can be fine tuned through the application of bias voltages. 
     with: 
     FIG. 3 is a schematic illustration of the electrical configuration of the device illustrated in FIGS. 1 and 2. 
     FIG. 4 is a plot showing fine-tuned microwave reflection, S 11 , and transmission, S 21 , versus frequency for several average bias voltages applied to each pole of a coplanar waveguide 3-pole bandpass filter operating at a temperature of 4 K. 
     FIG. 5 is a schematical cross-sectional illustration of the layers involved in utilizing the present invention with a slotline device. 
     FIG. 6 is a schematical cross-sectional illustration of the layers involved in utilizing the present invention with a microstrip device. 
     FIG. 7 is a schematical cross-sectional illustration of the layers involved in utilizing the present invention with a stripline device. 
     FIG. 8 is a side view of another embodiment of the invention in which a coplanar waveguide is configured with the signal line and ground planes deposited onto a substrate, with the nonlinear dielectric film deposited over the signal line and groundplanes. 
     with: 
     FIG. 8, is a side view of another embodiment of the present invention. 
     FIGS. 9A and 9B are schematical top and sectional views respectively of a 3-pole bandpass filter modified after manufacture for localized tuning. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The primary purpose of the present invention is to provide a versatile electrical fine tuning method which is considerably superior to the conventional mechanical tuning methods used for passive microwave/RF multiple element devices, such as multi-pole filters. To achieve this fine electrical tuning, the present invention modifies the devices to allow for local fine-tuning and uses nonlinear dielectric thin films and bias electrodes deposited in specific bias configurations which do not degrade the microwave/RF performance of the device to which it is applied. This modification, which provides for manipulation of either the device&#39;s shunt or series capacitance, can occur at the design stage, prior to the manufacture of the device, or can be applied to manufactured devices, should it be necessary. 
     Reference numbers used in the drawings may be repeated in subsequent drawings when they refer to the same item in prior drawings that have been described in the specification. Because of this, certain items may not be re-identified in the discussion of a subsequent drawing if they have previously been so identified. 
     According to the present invention, a bias signal is applied to certain predetermined areas of the device that controls the permittivity of a nonlinear dielectric thin film in the region where the bias induces an electric field. The invention can be understood more easily from reference to the drawings. 
     In FIG. 1, a diagrammatic cross-sectional side view of one embodiment of the invention is illustrated in which the invention is integrated into a coplanar waveguide  10 . As shown, nonlinear dielectric film  11  is deposited over substrate  12  in certain predetermined areas, the process of which will be explained more fully below. In this embodiment, the bias electrodes are ground planes (gp)  13 , which then are deposited over nonlinear dielectric film  11  with specific gaps in those regions where control of the permittivity of nonlinear dielectric film  11  is desired, as will be more clearly shown in FIG. 2. A low-frequency bias voltage is applied through low pass filters (LPF)  14 , with high frequency signals shunted to ground  16  through high pass filters (HPF)  15 . The configuration shown in FIG. 1 is only one of many methods of applying the present invention so that it is effective in fine tuning passive microwave and RF devices without perturbing their efficacy. In other embodiments, the order of deposition could be in any desired order, as long as the bias electrodes, like groundplanes  13 , are in contact with nonlinear dielectric film  11 . 
     The nonlinearity of dielectric constant, ∈, of dielectric layer  11  leads to facile fine tuning of microwave/RF devices under appropriate bias voltages through manipulation of the shunt or series capacitance of coplanar waveguide  10  or other similar multielement device. Signal line (cl)  18  and ground planes  13  are comprised of electrically conductive materials, and in some applications superconducting materials can be used to minimize conductor losses. For any electrically conductive material used for signal line  18  and ground planes  13 , it will be necessary to verify the compatibility of the electrically conductive material with the particular nonlinear dielectric being used. In certain situations, a buffer layer between ground planes  13  and nonlinear dielectric film  11  may be required. Possible candidates for the electrically conductive material include normal conductors platinum, gold, or copper. Possible candidates for the applicable superconducting materials include low-temperature superconductors such a Nb or NbN, and high-temperature superconductors such as Y—Ba—Cu—O (YBCO) specifically YBa 2 Cu 3 O 7−x  (0≦×≦0.5), or Tl—BA—Ca—Cu—O (TBCCO). 
     A top view of coplanar waveguide  10  of FIG. 1 is illustrated in FIG.  2 . Here, an arbitrary number of segmented groundplanes gp  13  are shown formed by gaps  13   a  on nonlinear dielectric film  11 , with each ground plane  13 , except for groundplanes  13  at microwave input and microwave output, being biased through low pass filter  14  and high pass filter  15 . Gaps  13   a  between ground planes  13  are approximately 2 μm wide, and are chosen so that high frequency signals propagate along segments of ground planes  13  with little pertubation. As shown schematically, gaps  17  (also shown in FIG. 1) between groundplanes  13  and signal line (cl)  18  are much larger than gaps  13   a  between adjacent groundplanes  13 . This assures that the additional gaps  13   a  applied by the present invention will not affect the high frequency performance of coplanar waveguide  10  or any other device with which it is employed. Also illustrated are gaps  18   a  between signal line  18  segments. Gaps  18   a  can range in width between approximately 1 μm and 10 s of μm, and are a function of the design of the multiple element devices and their intended application. 
     The generic tunable coplanar waveguide  10  shown in FIGS. 1 and 2, can, for example, be configured as a standard multi-pole half-wave bandpass filter. In that configuration, dielectric layer  11  can be approximately 1.2 μm thick, and gaps  13   a  between adjacent groundplanes  13  can be approximately 0.4 μm thick. Dielectric film  11 , in one embodiment illustrated in FIGS. 3 and 4 is paraelectric Sr 3 TiO (e.g. Sr 1−x Ba x TiO 3 , where 0≦×≦1), and ground plane  13  is high temperature superconductor Y—Ba—Cu—O. However, dielectric film  11  could be any appropriate nonlinear dielectric material. Similarly, groundplanes  13  and signal line  18  for superconducting applications could be any suitable high or low temperature superconductor. For room temperature applications ground planes  13  and signal line  18  could be any normal electrically conductive material. Substrate  12  can comprise LaAlO 3 , although any other suitable substrate material could be used. 
     As illustrated in FIGS. 1 and 2, coplanar waveguide  10  defines gaps  17 , which are approximately 30 μm wide, between ground plane  13  and signal line  18 , and gaps  13   a  between adjacent ground planes  13 . These gaps  17 ,  13   a  allow biasing of dielectric layer  11  at predetermined areas of dielectric layer  11 , shown in FIG. 2 at points BIAS-1 through BIAS-4 and BIAS-M-1 and BIAS-M along with associated low pass filters  14  and high pass filters  15 , but are sized so that they do not degrade passing microwave fields. This nondegradation is due to the fact that the capacitance of gaps  17  is much smaller than the capacitance of gaps  13   a.    
     These modifications to the conventional coplanar waveguide allow the electrical fine tuning of the dielectric constant, ∈, of dielectric layer  11  at different locations within coplanar waveguide  10  without significantly affecting the performance of coplanar waveguide  10 . As schematically illustrated in FIG. 3, this effectively allows the independent fine tuning of each of the poles  21  (pole  1 ),  22  (pole  2 ) and  23  (pole  3 ), and of the coupling capacitances  24  (C 1 ),  25  (C 2 ),  26  (C 3 ) and  27  (C 4 ) of coplanar waveguide  10 . 
     FIG. 4 shows microwave reflection, S 11    43 , and transmission, S 21    44 , versus frequency for several average bias voltages, 25 V  45 , 40 V  46 , and 65 V  47 . These average bias voltages, 25 V  45 , 40 V  46 , and 65 V  47 , are the averages of varying biases individually applied to each pole  21 ,  22 , and  23  of coplanar waveguide  10  (FIG. 3) operated at a temperature of 76 K (as shown in the frame in FIG.  4 ). For each average voltage applied, the filter profile was fine tuned by applying an optimized bias voltage to each segment of ground plane la (FIGS.  1  and  2 ). 
     As seen in FIG. 4, with no applied bias voltage  41  (No Bias in FIG.  4 ), the insertion of coplanar waveguide  10  causes high filter insertion loss and the profile is asymmetric. Upon the application of bias voltages  45 ,  46 ,  47 , the electrical lengths of poles  21 ,  22 , and  23 , and the capacitances  24 ,  2 , and  2 , (FIG. 3) can be varied and the filter profile can be fine tuned over a wide range. This clearly illustrates how the application of fine tuning bias voltages optimizes the filter profile. 
     In the device according to the present invention, the level of the bias voltage needed to effectuate tuning of the electrical lengths of poles  21 ,  22 , and  23  (FIG. 3) is more than an order of magnitude greater than the bias voltage needed to fine tune the filter profile. Because of this, FIG. 4 illustrates only the average bias voltages for poles  21 ,  22 , and  23 , and not the bias voltages for capacitances  24 ,  25 , and  26 , although the fine tuning voltages are used to obtain a symmetric and optimized filter profile for poles  21 ,  22 , and  23 , and capacitances  24 ,  25 , and  26 . 
     As is shown in FIG. 4, at an average 95 V bias voltage  42 , the reflection coefficient, S 11    43 , exhibits three distinct local minima (designated by the dashed curve) related to coupled resonances in the half-wave segments of coplanar waveguide  10 . A simple simulation using similar data measured at 4 K yielded 0.5 dB/m attenuation loss for coplanar waveguide  10 . This value can be interpreted as an upper limit for the dielectric loss under bias at 4 K, with a corresponding maximum effective loss tangent of 5×10 −4 . It should be noted that the 95 V bias voltage  42  at 76 K corresponding to a peak transverse dc electric field of approximately 3×10 6  V/m in gaps  17  (FIG.  1 ), and the dc electric field falls off rapidly from the surface of dielectric layer  11  (FIG. 1) toward the back side of substrate  12 . 
     For the fine tuning of coplanar waveguide  10 , very thin dielectric layers  11  provide lower dielectric loss, and thus a superior filter profile. Work on the present invention has indicated that the use of thinner SrTiO 3  films as dielectric layers  11  (FIG.  1 ), as well as large dc bias voltages should reduce dielectric losses significantly. In addition, the required bias voltages can be reduced by designing coplanar waveguides  10  having smaller gaps  17 . 
     Coplanar waveguide  10 , according to the present invention is electrically tunable and adaptive. The three-pole band-pass filter configuration shown in FIG. 3 has a filter response centered around 2.6 GHz, having an approximate 2% bandwidth, and an adaptive range of greater than 15%. The bandwidth and insertion loss improve with increasing bias voltages and decreasing temperatures. At the temperature of liquid helium, and with 95 V bias voltage  42  (FIG.  4 ), coplanar waveguide  10  (FIG. 1) has an insertion loss of approximately 3 dB, and a return loss of approximately 27 dB at the center frequency of the passband. 
     The present invention is not limited to coplanar waveguides. For example, another configuration of the invention is illustrated in FIG. 5, where slot line device  50  is shown comprising ground plane (gp)  51  deposited onto substrate  52 . Nonlinear dielectric film layer  53  is deposited onto ground plane  51  and substrate  52 . Similar to the bias voltage in FIG. 1, bias voltage  54  is applied to ground plane  51  through low pass filter (LPF)  54   a , with high frequency components shunted to ground through high pass filter (HPF)  55 . Gaps  13   a  (FIG. 2) between adjacent groundplanes  51  are not illustrated in FIG. 5, but are present in the device to allow localized fine tuning. Again, gaps  13   a  (not shown) between adjacent groundplanes  51  are sufficiently small as to provide high capacitance so that passing microwaves are not significantly perturbed. 
     Similar depositions of nonlinear dielectric films, centerlines, bias electrodes and ground planes can be used for most any passive microwave/RF device, including microstrip lines and strip lines to allow for electrical tuning of those devices. 
     FIG. 6 illustrated the deposition layers for a microstrip device wherein substrate  61  has groundplane layer  62  deposited over it. Dielectric film layer  63  is deposited over groundplane layer  62 . Nonlinear dielectric film layer  64  is deposited over dielectric layer  63 . Because, in a microstrip device, groundplane layer  62  is deep within the device, separate bias tuning pad electrodes  65  are deposited onto nonlinear dielectric layer EA at predetermined locations, and define a small gap  66  with signal line (C 1 )  67  and the same gaps between adjacent areas of nonlinear dielectric film layer  64  as are illustrated as gaps  22  in FIG.  2 . It should be noted that bias electrodes  65  can be variously configured, as can nonlinear dielectric layer  64 , as long as they are in physical contact with each other. In fact, for any type device nonlinear dielectric layer  64  could overlie signal line  67  and bias electrodes  65 . 
     For a superconducting microstrip, bias electrodes  65  could also be a superconducting material. For a conventional microstrip, any electrically conductive material could be used as previously discussed. Bias voltage  68  is connected to bias electrodes  65  through low pass filter (LPF)  68   a , with high frequency signals either floated or shunted to ground through high pass filter HPF  68   b  as shown in FIG.  6 . 
     The configuration according to the present invention for a stripline device is shown in cross-section in FIG.  7 . Here, it can be seen that identical mirrored arrangements of substrate  71 , groundplane layer  72 , dielectric film layer  73 , and nonlinear dielectric layer  74 . Lying between the two arrangements are bias electrodes  75  and signal line (C 1 )  76 , with bias tuning pad electrodes  75  defining small gap  77  with signal line  76 . 
     Once again, the actual arrangement of bias electrodes  75  and nonlinear dielectric layer  74  can realize numerous configurations which could have dielectric layer overlying bias electrodes  75 , as well as signal line  76 . Also, bias electrodes  75  again could be made of superconducting or normal conductive material depending on whether the stripline device is superconducting. Bias voltage  78 , as before is connected to bias electrodes  75  with associated filter  78   a  (LPF), and optional filter  78  (HPF). 
     With the configurations of FIGS. 6 and 7, small gaps  66 ,  77 , respectively, again are sufficiently small that relatively low bias voltages yield appreciable electric fields. However, small gaps  66 ,  77  are sufficiently wide to prevent significant pertubation of high frequency device performance. 
     Another embodiment of coplanar waveguide  10  is illustrated in FIG.  8 . As is shown, for this embodiment, signal line (C 1 )  81  is deposited directly onto substrate  82 . Ground planes (gp)  83  also are deposited onto substrate  82  in predetermined areas, in close proximity to signal line  81 , defining gap  84 . Small gaps also are defined between each ground plane  83 . Nonlinear dielectric film  85  is then deposited over signal line  81  and ground planes  83 . In this embodiment, the predetermined areas of ground planes  83  contact the desired predetermined areas of nonlinear dielectric film  85 . As in previous embodiments, bias voltage (BIAS) is provided to ground planes 83 through the combination of low pass filters (LPF) and high pass filters (HPF). 
     Again, in other embodiments, the order of deposition of the various layers could be in any desired order, as long as bias electrodes, like groundplanes  13 , are in contact with nonlinear dielectric film  11 , as depicted in FIG.  1 . 
     Still another embodiment of the invention is illustrated schematically in FIG. 9A, a top view, and FIG. 9B, a sectional side view. As seen in FIG. 9A an exemplary passive multiple element device  90 , a, 3-pole bandpass, filter, is shown having input  91  and output  92 , and electrically conductive resonant elements  93 ,  94 , and  95 . The importance of FIGS. 9A and B is the illustration of use of the invention to either add local fine tuning to a previously manufactured device or to a device at its design stage, prior to its manufacture. 
     As shown in FIG. 9A nonlinear dielectric material  96  is deposited in contact with each electrically conductive resonant elements  93 ,  94 , and  95 , as well as with electrically conductive material  97 , its end segement  97   a , and contact pad  98 , to provide one pole of the individual bias voltages (shown in FIG.  9 B). Resistive and inductive material  99  connects the opposite end of each electrically conductive resonant elements  93 ,  94 , and  95  to contact pad  100  for the opposite pole of the individual bias voltages (shown in FIG.  9 B). 
     A schematical sectional side view of device  90  along section line  9 B is illustrated in FIG.  9 B. In FIG. 9B, it is easier to see the deposition order and the cooperation of the various materials. In the manufacturing process electrically conductive resonant elements  93 ,  94 , and  95  and inputs  91  and  92  would be deposited first. In a post manufacture situation, these elements would already be in place. Next, resistive and inductive material  99  and contact pads  98  and  100  are deposited to provide connection to the bias voltages. Finally, nonlinear dielectric material  96  is deposited from electrically conductive resonant elements  93 , and elements  94 ,  95  (FIG. 9A) to connect with resistive and inductive material  99 . As shown, contact pads  98  and  100  are connected through low pass filter  14  to the adjustable bias voltage. 
     The important point of the present invention is that it can be implemented in various ways in various devices so that it is applicable for most any multiple element passive microwave/RF device. The invention can be applied to an existing device to tailor its characteristics to meet certain criteria, but perhaps more effectively, could be incorporated into devices at the time of manufacture. In either case, the present invention allows for the precise localized fine tuning of passive devices so that they perform to their desired specifications. The intent of the invention remains constant in either regime to provide a novel method of localized fine tuning these devices through modification of the device structure and the control of the permittivity of nonlinear dielectric layers in certain predetermined areas. 
     The foregoing description of the preferred embodiments of the invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.