WO2007123504A1

WO2007123504A1 - Tunable frequency selective surface

Info

Publication number: WO2007123504A1
Application number: PCT/US2006/006025
Authority: WO
Inventors: Daniel Sievenpiper
Original assignee: Hrl Laboratories, Llc
Priority date: 2006-04-20
Filing date: 2006-04-20
Publication date: 2007-11-01
Also published as: GB0811956D0; GB2448626A; WO2007123504A8

Abstract

An apparatus and methods for operating a frequency selective surface are disclosed. The apparatus can be tuned to an on/off state or transmit/reflect electromagnetic energy in any frequency. The methods disclosed teach how to tune the frequency selective surface to an on/off state or transmit/reflect electromagnetic energy in any frequency.

Description

Tunable Frequency Selective Surface

FIELD '

This technology relates to a frequency selective surface that can be toned to an on-state, off-state and/or can transmit/reflect electromagnetic energy in any frequency band.

BACKGROUND AND PRIOR ART

Antennas 100 may be hidden behind a radome 110, see Figure 1, particularly if they are being used in an application where they could be exposed to the environment. The radome protects the antenna from both the natural environment such as rain and snow, and the man-made environment such as jamming signals. Often, the radome is made so that it transmits electromagnetic energy within a narrow band centered around the operating frequency of the antenna, so as to deflect or reflect jamming signals at other frequencies. This is done using a frequency selective surface (FSS), having a grid or lattice of metal patterns or holes in a metal sheet. The design and construction of FSSs is well known to those skilled in the art of radome design and electromagnetic material design.

Two surfaces are commonly used in FSS design, the "Jerusalem cross" structure 200, shown in Figure 2a, and its "Inverse structure" 300, shown in Figure 3a. A unit cell equivalent circuit 201 of the Jerusalem cross 200, FSS can be viewed as a lattice of capacitors 210 and inductors 220 in series, shown in Figure 2b. The capacitors 210 and inductors 220 are oriented in two orthogonal directions so that the surface can affect both polarizations. Near the LC resonance frequency, the series LC circuit has low impedance, and shorts out the incoming electromagnetic wave, thereby deflecting it off the surface. At other frequencies, the LC circuit is primarily transmitting, although it does provide a phase shift for frequencies near the stop band, shown in Figure 2c. The Inverse structure 300, shown in Figure 3a, has opposite characteristics. A unit cell equivalent circuit 301 of the Inverse structure 300, FSS can be viewed as a lattice of capacitors 310 and inductors 320 in parallel, shown in Figure 3b. It is transmisstve near LC resonance frequency and reflective at otter frequencies, shown in Figure 3c.

The radome typically transmits RF energy through the radome only at the operating frequency of the antenna, and reflects or deflects at other frequencies. In some applications, it may be desirable to tune the radome, particularly when a tunable antenna is used inside the radome. It may also be desirable to set the radome to an entirely opaque (off) state, so that it is deflective or reflective over a broad range of frequencies. It may also be desirable to program the radome so that different regions have different properties,_, either transmitting within a frequency band, or opaque as desired. To achieve these requirements the FSS needs to be tunable.

Throughout the years, different techniques have been implemented to achieve the tuning of the FSS. The tuning has been achieved by: varying the resistance, see Chambers, B., Ford, K.L., "Tunable radar absorbers using frequency selective surfaces", Antennas and Propagation, 2001. Eleventh International Conference on (IEEE Conf. Publ. No. 480), vol. 2, pp. 593-597, 2001; pumping liquids that act as dielectric loading, see Lima, A.C. deC, Parker, E.A., Langley, RJ., "Tunable frequency selective surface using liquid substrates", Electronics Letters, vol. 30, issue 4, pp. 281-282, 1994; rotating metal elements, see Gianvittorio, J.P., Zendejas, J., Rahmat-Sami, Y., Judy, J., "Reconfigurable MEMS-enabled frequency selective surfaces", Electronics Letters, vol. 38, issue 25, pp. 1627-1628, 2002; using a ferrite substrate, see Chang, T.K., Langley, RJ., Parker, E.A., "Frequency selective surfaces on biased ferrite substrates", Electronics Letters, vol. 30, issue 15, pp. 1193-1194, 1994; pressurizing a fluid, see Bushbeck, M.D., Chan, C.H., "A tunable, switchable dielectric grating", IEEE Microwave and Guided Wave Letters, vol. 3, issue 9, pp. 296-298, 1993; using a varactor tuned grid array that is a kind of quasi-optic oscillator, see Oak, A.C., Weikle, R.M. Jr., "A varactor tuned 16-element MESFET grid oscilator", Antennas and Propagation Society International Symposium, 1995; using an electro-optic layer, see Rhoads¹ patent (U.S. 6,028,692); using transistors, see Rhoads' patent (U.S. 5,619,366); using ferroelectrics between an absorptive state and a transmissive state, see Wheian's patent (U.S. 5,600,325).

Although the above-mentioned methods are used to tune the FSS₅ these methods are not ideal for use with a tunable antenna. Many of the above methods are not practical for rapid tuning because they use moving metal parts, or pumping dielectric liquids. Some of them include switching between discrete states using transistors, which is less useful than a continuous tunable surface. Others include only on and off states, and cannot be tuned in frequency. Others require bulk ferrite, ferroelectric, or electrooptic materials, which can be lossy and expensive. None of the prior art achieves the capabilities of the present technology, even though a need exists for those capabilities.

The present technology 420 is able to transmit electromagnetic energy 450 in a particular frequency band through the radome, and deflect or reflect electromagnetic energy in - other frequency bands, shown in Figure 4. It can also be tuned to an off state where it is deflective or reflective, or an on state where it is absorptive over a broad range of frequencies. Also some regions 440 of the surface can be tuned to different frequencies while other regions 430 of the surface can be set to an opaque state, shown in Figure 4. Further, it uses rapidly tunable varactor diodes and low cost printed circuit board construction.

BRIEF DESCRIPTION OF THE HGURES AND THE DRAWINGS

Figure 1 depicts an arrangement of the antenna and radome;

Figure 2a depicts a top view of the Jerusalem cross FSS;

Figure 2b depicts a unit cell equivalent circuit of the Jerusalem cross FSS;

Figure 2c depicts a transmission spectrum of the Jerusalem cross FSS; Figure 3a depicts a top view of the Inverse structure of the Jerusalem cross FSS;

Figure 3b depicts a unit cell equivalent circuit of the Inverse structure of the Jerusalem cross FSS;

Figure 3c depicts a transmission spectrum of the Inverse structure of the Jerusalem cross FSS;

Figure 4 depicts an arrangement of the steerable antenna and tunable radome where the radome has an opaque region and a transparent region, and the antenna sending a microwave beam through the transparent region;

Figure 5a depicts an inappropriate series LC unit cell equivalent circuit;

Figure 5b depicts an appropriate parallel LC unit cell equivalent circuit;

Figure 5c depicts an example of an appropriate TFSS unit cells;

Figure 5d depicts an example of an appropriate TFSS unit cells;

Figure 6a depicts a surface view of a circuit board containing conductors and varactor on both sides;

Figures 6b-c depict the front view of each surface of the circuit board in Fig. 6a;

Figure 6d depicts a transparent view of the first surface of the circuit board in Fig. 6a over the second surface of the circuit board in Fig. 6a;

Figure 6e depicts the results of modeling the circuit board in Fig. 6a on the Ansoft HFSS software; Figure 6f depicts tuning both sides of the circuit board in Fig. 6a to a resonance frequency;

Figure 6g depicts tuning the first surface of the circuit board in Fig. 6a to three different resonance frequencies;

Figure 6h depicts tuning the second surface of the circuit board in Fig. 6a to three different frequencies;

Figure 6i depicts a transparent view of the first surface over the second surface and the propagation of different resonance frequencies through the circuit board in Fig. 6a;

Figure 6j depicts setting the circuit board in Fig. 6a to an opaque state;

Figure 6k depicts tuning a region of the first surface to one frequency and setting the remaining region of the first surface in opaque mode;

Figure 61 depicts tuning a region of the second surface to one frequency and setting the remaining region of the second surface in opaque mode;

Figure 6m depicts a transparent view of the first surface over the second surface and the propagation of frequency and opaque mode through the circuit board in Fig. 6a;

Figure 7a depicts a surface view of a circuit board containing conductors and varactor on both sides;

Figures 7b-c depict the front view of each surface of the circuit board hi Fig. 7a;

Figure 7d depicts a transparent view of the first surface of the circuit board in Fig. 7a over the second surface of the circuit board in Fig. 7a; Figure 7e depicts the results of modeling the circuit board in Fig. 7a on the Ansoft HFSS software;

Figure 7f depicts tuning both sides of the circuit board in Fig. 7a to a resonance frequency;

Figure 7g depicts setting the circuit board in Fig. 7a to an opaque state;

Figure 8a depicts a surface view of a circuit board containing conductors and varactor on the first surface, conductors on the second surface and vias connecting first and second surface;

Figures 8b-c depict the front view of each surface of the circuit board in Fig. 8 a;

Figure 8d depicts a transparent view of the first surface of the circuit board in Fig. 8a over the second surface of the circuit board in Fig. 8a;

Figure 8e depicts the results of modeling the circuit board in Fig. 8a on the Ansoft HFSS software;

Figure 8f depicts tuning both sides of the circuit board in Fig. 8a to a resonance frequency;

Figure 8g depicts setting the circuit board in Fig. 8a to an opaque state;

Figure 9a depicts a surface view of a circuit board containing conductors on the first surface, conductors and varactor on the second surface and vias connecting the first and the second surface;

Figures 9b-c depict the front view of each surface of the circuit board in Fig. 9a; Figure 9d depicts a transparent view of the first surface of Hie circuit board in Fig. 9a over the second surface of the circuit board in Fig. 9a;

Figure 10a depicts a surface view of a circuit board containing varactors on the first layer, conductors on the second and third layers and vias connecting all the layers;

Figures lOb-d depict the front view of each layer of the circuit board in Fig. 10a;

Figure 1Oe depicts a transparent -view of the first layer of the circuit board in Fig. 10a over the second layer of the circuit board in Fig. 10a over the third layer of the circuit board in Fig. 10a;

Figure 11a depicts a surface view of a circuit board containing conductors and varactors on the first surface, conductors on the second surface and vias connecting first surface - and second surface;

Figures 1 lb-c depict the front view of each surface of the circuit board in Fig. 11a;

Figure 1 Id depicts a transparent view of the first surface of the circuit board in Fig. 11a over the second surface of the circuit board in Fig. 11a;

Figure lie depicts the results of modeling circuit board in Fig. 11 a on the Ansoft HFSS software;

Figure Hf depicts tuning the circuit board in Fig. 11 a to a resonance frequency;

Figure 1 Ig depicts setting the circuit board in Fig. 1 Ia to an opaque state;

Figure 1 Ih depicts tuning the circuit board in Fig. 6a to three different frequencies and an opaque state; Figure 12a depicts a surface view of a circuit board containing conductors on the first surface, conductors and varactors on the second surface and vias connecting the first surface and second surface.

Figures 12b-c depict the front view of each surface of the circuit board in Fig, 1 Ia;

Figure 12d depicts a transparent view of the first surface of the circuit board in Fig. 12a over the second surface of the circuit board in Fig. 12a;

Figure 13a depicts a surface view of a circuit board containing varactors on the first layer, conductors on the second and third layers and vias connecting all the layers.

Figures 13b-d depict the front view of each layer of the circuit board in Fig. 13a;

Figure 13e depicts a transparent view of the first layer of the circuit board in Fig. 13a over the second layer of the circuit board in Fig. 13a over the third layer of the circuit board in Fig. 13a;

DETAILED DESCRIPTION

Of the two surfaces that are commonly used in FSS design, the Inverse structure 300 is the most appropriate in designing a TFSS. The series LC circuit 510, shown in Figure 5a, used by the Jerusalem cross 200 is difficult to use because it lacks a continuous metal path throughout the surface, so it is difficult to provide DC bias to the internal cells. Whereas, the parallel LC circuit 511, shown in Figure 5b, used by Inverse structure 300, does not have this limitation.

The parallel circuit 512, which is an equivalent circuit for LC circuit 511, can be constructed as a varactor diode 530 in parallel with a narrow metal wire 540, which acts as an inductor, and in parallel with a DC blocking capacitor 550, as shown in Figure 5c. The parallel circuit 513, which is another equivalent circuit for LC circuit 511, can also be constructed as two varactor diodes 560 and 561 in parallel with a narrow metal wire 570, which acts as an inductor, as shown in Figure 5d.

Using varactor diodes has the advantage in that the opaque state is easy to achieve by simply forward-biasing the varactors, so that they are conductive. Although otter kinds of varactors or equivalent devices could be presently used, such as MEMS varactors or ferroelectric varactors, for clarity's sake, this discussion will concentrate on implementing this technology using varactor diodes.

In one embodiment, the TFSS includes a circuit board 600, with an array of conductors 640a-c, 650a-c and varactors 630 on a major surface 610 and an array of conductors 670a-c, 680a-c and varactors 660 on a major surface 620, as shown in Figure 6a. Figure 6a shows the side view of the substrate 600.

Figure 6b shows a schematic of a circuit on the major surface 610. The major surface 610 has varactors 630 organized in rows where the orientation of the varactors in one row is a mirror image of the varactors in the neighboring row, as shown in Figure 6b. Conductors 640a-c and 650a-c run across the major surface 610 between the rows of varactors 630.

Figure 6c shows a schematic of a circuit on the major surface 620. The surface 620 has varactors 660 organized in columns where the orientation of the varactors in one column is a mirror image of the varactors in the neighboring column, as shown in Fig. 6c. Conductors 670a-c and 680a-c run across the major surface 620 between the columns of varactors 660.

Although the conductors in Figures 6b and 6c are represented as straight lines, it shall be understood that the conductors can have different shapes, including but not limited to straight tines, crenulated lines and/or wavy lines, for this technology to work. Although the conductors in Figures 6b and 6c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors.

Structure 690 in Figure 6d shows an overlay of the circuit on the major surface 610 and the circuit on the major surface 620. Varactors and conductors on major surface 610 are oriented at an angle to the varactors and conductors on the major surface 620. Although the varactors and conductors on the major surface 610 are depicted at a 90° angle to the varactors and conductors on the major surface 620 as shown in structure 690 in Figure 6d, it needs to be appreciated that the angle can be varied.

The lattice period of structure 690 is represented by distance IB and 1C as shown in Figures 6b-d. For this technology to work the distances IB and 1C can range from 1/15 of the wavelength to 1/2 of the wavelength, It needs to be appreciated that the distances IB and 1C do not have to be equal for this technology to work.

The thickness IA of the circuit board 600, shown in Figure 6a, is sufficiently small to produce capacitive coupling between the conductors on major surface 610 and the conductors on major surface 620. Since capacitive coupling between conductors depends on the distance between the conductors and the width of the conductors, in this embodiment the width of all the conductors and thickness IA are matched so as to produce capacitive coupling between the conductors on major surface 610 and the conductors on major surface 620.

Structure 690 was modeled using Ansoft HFSS software. See Figure 6e. In the first simulation the lattice period was modeled at IB=IC =lcm, the conductors were modeled at lmm width, and substrate was modeled at IA= lmm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was tuned from 1 to 64 by factors of 2. Increasing the dielectric constant from 1 to 64 tuned the resonance frequency of the surface from 8 Ghz down to about 2 Ghz. In the second simulation, the lattice period was modeled at IB=IC =lcm, the conductors were modeled at lmm width, and the substrate was modeled at lA=7mm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was 8. Due to reduced capacitive coupling between conductors on the major surface 610 and the conductors on the major surface 620, the transmission level in the pass-band was reduced by about 50%, and the pass-band shifted in frequency.

Applying voltages to conductors on each major surface of the substrate controls the propagation of different frequencies through the TFSS. Depending on the voltages applied, the capacitance of the varactors is tuned and the resonance frequency of the TFSS is adjusted. Setting bias wires 640a-c and 670a-c to 0 volts and setting bias wires 650a-c and 680a-c to +10 volts, as shown in Figure 6f, will cause all of the varactors to be reverse biased and this will allow a certain resonance frequency to pass through the entire TFSS. The voltage numbers are just provided as an example; a person familiar with this technology would know that the voltage numbers could be varied to achieve desired resonance frequency.

In this embodiment different regions of the TFSS can be tuned to propagate different resonance frequencies along the length of the conductors on each major surface of the circuit board 600. The propagation of the resonance frequency with horizontal polarization through the TFSS can be controlled by applying appropriate voltages to the conductors on major surface 610 as shown in Figure 6h. Setting conductors 640a-c to 0 volts and setting conductor 650a to +10 volts will cause varactors in region Rl to be reverse biased and this will allow only a resonance frequency with horizontal polarization HFl to propagate through the Rl region of TFSS between the conductors 640a and 640b, as shown in Figure 6g. Setting conductor 650b to +15 volts will cause varactors in region R2 to be reverse biased and this will allow only a resonance frequency with horizontal polarization HF2 to propagate through the R2 region of TFSS between the conductors 640b and 640c, as shown in Figure 6g. Setting conductor 650c to +20 volts will cause varactors in region R3 to be reverse biased and this will allow only a resonance frequency with horizontal polarization HF3 to propagate through the R3 region of ¹TlFSS between the conductors 640c and 650c, as shown in Figure 6g. The voltage numbers are just provided as an example; the voltage numbers could be varied to achieve desired resonance frequency.

The propagation of the resonance frequency with vertical polarization through the TFSS can be controlled by applying appropriate voltages to the conductors on major surface 620 as shown in Figure 6h. Setting conductors 670a-c to 0 volts and setting conductor 680a to +10 volts will cause varactors in region R4 to be reverse biased and this will allow only a resonance frequency with vertical polarization VFl to propagate through the R4 region of TFSS between the conductors 670a and 67Ob₅ as shown in Figure 6h. Setting conductor 680b to +15 volts will cause varactors in region R5 to be reverse biased and this will allow only a resonance frequency with vertical polarization VF2 to propagate through the R5 region of TFSS between the conductors 670b and 670 c, as shown in Figure 6h. Setting conductor 680c to +20 volts will cause varactors in region R6 to be reverse biased and this will allow only a resonance frequency with vertical polarization VF3 to propagate through the R6 region of TFSS between the conductors 670c and 670c, as shown in Figure 6h. The voltage numbers are just provided as an example; the voltage numbers could be varied to achieve desired resonance frequency.

The propagation of the resonance frequency with horizontal and vertical polarization is achieved through structure 690 in Figure 6i. When structure 690 is set up as shown in Figures 6i there will be overlapping regions that will allow both a vertical and horizontal polarization of a single resonance frequency to propagate through the TFSS. Region R7, as shown in Figure 6i, allows the propagation of both HFl and YFl through the TFSS. Region R8, as shown in Figure 6i, allows the propagation of both HF2 and VF2 through the TFSS. Region R9, as shown in Figure 6i, allows the propagation of both HF3 and VF3 through the TFSS. The size and shape of the regions that allow both vertical and horizontal polarization resonance frequencies to propagate through TFSS shown here are just provided as an example. The size and shape of these regions can be adjusted by applying appropriate voltages to the appropriate conductors. When structure 690 is set up as shown in Figures 6i₃ there will also be overlapping regions that will allow both a vertical and horizontal polarization of different resonance frequencies to propagate through the TFSS. Region RlO, as shown in Figure 6i, allows the propagation of HFl and VF2 through the TFSS. Region RIl, as shown in Figure 6i, allows the propagation of HFl and VF3 through the TFSS. Region R12, as shown in Figure 6i, allows the propagation of HF2 and VFl through the TFSS. Region R13, as shown in Figure 6i, allows the propagation of HF3 and VFl through the TFSS. Region R14, as shown in Figure 6i, allows the propagation of HF3 and VF2 through the TFSS. Region R15, as shown in Figure 61, allows the propagation of HF2 and VF3 through the TFSS.

In this embodiment, the TFSS can also be set to an opaque (off) state. The opaque state is achieved by forward biasing the varactors, as shown in Figure 6j, which shorts across the continuously conductive loop. Setting conductors 640a-c and 670a-c to 0 volts and setting conductors 650a-c and 680a-c to -1 volts, as shown in Figure 6j, will cause all of the varactors to be forward biased thereby blocking all the resonance frequencies rrom propagating though the TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied and still cause all of the varactors to be forward biased.

In this embodiment, the region of the TFSS can be set to an opaque state while the remaining region is set to propagate a certain resonance frequency. The propagation of a particular resonance frequency with horizontal polarization through a region of the TFSS and blocking the remaining resonance frequencies with horizontal polarization through the rest of the TFSS can be controlled by applying appropriate voltages to the conductors on major surface 610 as shown in Figure 6k. Setting conductors 640a-c to 0 volts and setting conductors 650a and 650c to -1 volts will cause varactors in regions R16 and R18 to be forward biased and this will block any resonance frequency with horizontal polarization from propagating through the R16 and R18 regions of TFSS, as shown in Figure 6k. Setting conductors 650b to +15 volts will cause varactors in region R17 to be reverse biased and this will allow a resonance frequency with horizontal polarization HF2 to propagate through the Rl 7 region of TFSS, as shown in Figure 6k. The voltage numbers are just provided as an example. The voltage numbers could be varied to achieve desired resonance frequency or an opaque state.

The propagation of a particular resonance frequency with vertical polarization through a region of the TFSS and blocking the remaining resonance frequencies with vertical polarization through the rest of the TFSS can be controlled by applying appropriate voltages to the conductors on major surface 620 as shown in Figure 61. Setting conductors 670a-c to 0 volts and setting conductors 680a and 680c to -1 volts will cause varactors in the regions R19 and R21 to be forward biased and this will block any resonance frequency with vertical polarization from propagating through the R19 and R21 regions of TFSS, as shown in Figure 61. Setting conductor 680b to +15 volts will cause varactors in the region R20 to be reverse biased and this will allow a resonance frequency with vertical polarization VF2 to pass through the R20 region of TFSS, as shown in Figure 61. The voltage numbers are just provided as an example, the voltage numbers could be varied to achieve desired resonance frequency or an opaque state.

The propagation of a particular resonance frequency with horizontal and vertical polarization through a region of the TFSS and blocking of the remaining resonance frequencies through the rest of the TFSS is achieved through the structure 690 in Figure 6m. When structure 690 is set up as shown in Figure 6m there will be a region propagating a particular resonance frequency, regions with horizontal and vertical polarization, regions blocking all the frequencies, regions propagating only horizontal polarization of the particular frequency and regions propagating only vertical polarization of the particular resonance frequency. Region R30, as shown in Figure 6m, allows the propagation of HF2 and VH2 through the TFSS. Regions R22, R29, R27 and R25 as shown in Figure 6m, block all the vertical and horizontal polarizations of all the resonance frequencies from propagating through the TFSS. Regions R26 and R23 allow propagation of only VF2 through the TFSS. Regions R28 and R24 allow propagation of only HF2 through the TFSS. The size and shape of the region that allows both vertical and horizontal polarization resonance frequencies to pass through TFSS shown here are just provided as an example. The size and shape of these regions can be adjusted by applying an appropriate voltage to the appropriate conductors. The size and shape of the opaque regions shown here are also just provided as an example. The size and shape of these opaque regions can be adjusted by applying an appropriate voltage to the appropriate conductors.

In another embodiment, the TFSS includes a circuit board 700, with an array of conductors 740a-d, 730a-d and varactors 750 on the major surface 710, an array of conductors 760a-c, 770a-c and varactors 780 on the major surface 720 and vias 795 and 796 connecting major surfaces 710 and 720 as shown in Figure 7a-c. Figure 7a shows the side view of the substrate 700.

Figure 7b shows a schematic of a circuit on the major surface 710. The major surface 710 has a plurality of oppositely oriented varactors 750 connected in series and organized in rows where the orientation of the varactors in one row^' is a mirror image of the varactors in the neighboring row, as shown in Figure 7b. Conductors 740a-d run along the length of the major surface 710 between the rows of varactors 750. Conductors 730a- d run along the width of the major surface 710 between the varactors 750 connecting the Conductors 740a-d, as shown in Figure 7b.

Figure 7c shows a schematic of a circuit on the major surface 720. The major surface 720 has a plurality of oppositely oriented varactors 780 connected in series and organized in columns where the orientation of the varactors in one column is a mirror image of the varactors in the neighboring column, as shown in Figure 7c. Conductors 760 a-c run along the width of the major surface 720 between the columns of varactors 780. Conductors 770a-c run along the length of the major surface 720 between the varactors 780 connecting the conductors 760a-c, as shown in Figure 7c.

Although the conductors in Figures 7b and 7c are represented as straight lines, it is to be understood that the conductors can have different shapes, including but not limited to straight lines, crenulated lines and/or wavy lines, for this technology to work. Although the conductors in Figures 7b and 7c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors.

Although conductors 730a-d appear to be perpendicular to conductors 740a-d in Figure 7b, it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary.

Although conductors 760a-c appear to be perpendicular to conductors 770a-c in Figure 7c it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary.

Structure 790 in Figure 7d shows an overlay of the circuit on the major surface 71T) and the circuit on the major surface 720. Varactors and conductors on major surface 710 are oriented at an angle to the varactors and conductors on the major surface 720. Although the varactors and conductors on the major surface 710 are depicted at a 90° angle to the varactors and conductors on the major surface 720 as shown in structure 790 in Figure 7d, it needs to be appreciated that the angle can be varied.

Vias 796 connect the varactors 780 on the major surface 720 to conductors 730a-d on the major surface 710, shown in Figure 7d. Vias 795 connect the varactors 750 on the major surface 710 to conductors 770a-c on the major surface 720, shown in Figure 7d.

The lattice period of structure 790 is represented by distance 2B and 2C as shown in Figure 7d. For this technology to work, the distances 2B and 2C can range from 1/15 of the wavelength to 1/2 of the wavelength. The distances 2B and 2C do not have to be equal for this technology to work. The thickness 2A of the circuit board 700, shown in Figure 7a, is less important than the thickness IA of the circuit board 600 described above. Vias 796 and 795 make the circuit board 700 less susceptible to the variations in the thickness 2A.

Structure 790 was modeled using Ansoft HFSS software. See Figure 7e. In the first simulation the lattice period was modeled at 2B=2C =lcm, the conductors were modeled at lmm width, and the substrate was modeled at 2A=lmm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was tuned from 1 to 64 by factors of 2. Increasing the dielectric constant from 1 to 64 tuned the resonance frequency of the surface from 8 Ghz down to about 2 Ghz. In the second simulation the lattice period was modeled at 2B=2C =lcm, the conductors were modeled at lmm width, and the substrate was modeled at 2A=7mm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was 8. As can be seen by the results, shown in Figure 7e, this design is more resistant to variations in the substrate thickness. The transmission level in the pass-band was reduced by about 20%. This design is less concerned with maintaining capacitive coupling and is more resistant to variations in the thickness 2A.

Applying voltages to conductors on each major surface of the substrate controls the propagation of different frequencies through the TFSS. Depending on the voltages applied, the capacitance of the varactors is tuned and the resonance frequency of the TFSS is adjusted. Setting conductors on the major surface 710 to 0 volts and setting conductors on the major surface 720 to +10 volts, as shown in Figure 7f, will cause all of the varactors to be reverse biased and this will allow a certain resonance frequency to pass through the entire TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied to achieve desired resonance frequency.

In this embodiment, the TFSS can also be set into an opaque (off) state. The opaque state is achieved by forward biasing the varactors, as shown in Figure 7g, which shorts across the continuously conductive loop. Setting conductors on major surface 710 to 0 volts and setting conductors on major surface 720 to -1 volts, as shown in Figure 7g, will cause all of the varactors to be forward biased, thereby blocking all the resonance frequencies from propagating through the TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied and still cause all of the varactors to be forward biased.

In another embodiment, the TFSS includes a circuit board 800, with an array of conductors 840a-d, 830a-d and varactors 880 on the major surface 810, an array of conductors 860a-c, 870a-c on the major surface 820 and vias 895 connecting major surfaces 810 and 820 as shown in Figure 8a-c. Figure 8a shows the side view of the substrate 800.

Figure 8b shows a schematic of a circuit on the major surface 810. The major surface 810 has a plurality of oppositely oriented, interconnected varactors 880 organized in rows where the orientation of the varactors in one row is a mirror image of the varactors in the neighboring row, as shown in Figure 8b. Conductors 840a-d run along the length of the major surface 810 between the rows of varactors 880. Conductors 830a-d run along the Width of the major surface 810 between the varactors 880 connecting the conductors 840a-d, as shown in Figure 8b.

Figure 8c shows a schematic of a circuit on the major surface 820. The major surface 820 has conductors 860a-c running along the width of the major surface 820 and conductors 870a-c running along the length of the major surface 820 connecting the conductors 860a-c, as shown in Figure 8c.

Although the conductors in Figures 8b and 8c are represented as straight lines, it is to be understood that the conductors can have different shapes, including but not limited to straight lines, crenulated lines and/or wavy lines, for this technology to work.

Although the conductors in Figures 8b and 8c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors. Although conductors 830a-d appear to be perpendicular to conductors 840a-d in Figure 8b, it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to wort The angle between the intersecting conductors may vary.

Although conductors 860a-c appear to be perpendicular to conductors 870a-c in Figure 8c, it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary.

Structure 890 in Figure 8d shows an overlay of the circuit on the major surface 810 and the circuit on the major surface 820. Conductors on major surface 810 are oriented at an angle to the conductors on the major surface 820. Although the conductors on the major surface 810 are depicted at a 90° angle to the conductors on the major surface 820 as shown in structure 890 in Figure 8d, it needs to be appreciated that the angle can be varied.

Vias 895 connect the varactors 880 on the major surface 810 to the point of intersection of conductors 870a-c and 860a-c on the major surface 820, shown in Figure 8d.

The lattice period of structure 890 is represented by distance 3B and 3C as shown in Figure 8d. For this technology to work, the distances 3B and 3C can range from 1/15 of the wavelength to 1/2 of the wavelength. The distances 3B and 3C do not have to be equal for this technology to work.

The thickness 3 A of the circuit board 800, shown in Figure 8a, is less important than the thickness IA of the circuit board 600 described above. Vias 895 make the circuit board 800 less susceptible to the variations in the thickness 3 A.

Structure 890 was modeled using Ansoft HFSS software. See Figure 8e. In the first simulation, the lattice period was modeled at 3B=3C =lcm, the conductors were modeled at lmm width, and the substrate was modeled at 3A=lmm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was tuned from 1 to 64 by factors of 2. Increasing the dielectric constant from 1 to 64 tuned the resonance frequency of the surface from 8 Ghz down to about 2 Ghz. In the second simulation, the lattice period was modeled at 3B=3C =lcm thickness, the conductors were modeled at lmm width, and the substrate was modeled at 3A=7mm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was tuned from. 1 to 64 by factors of 2. As can be seen by the results, shown hi Figure 8e, this design is more resistant to variations in the substrate thickness and requires less varactors which offers simpler construction.

Applying voltages to conductors on each major surface of the substrate controls the propagation of different frequencies through the TFSS. Depending on the voltages applied, the capacitance of the varactors is tuned and the resonance frequency of the TFSS is adjusted. Setting conductors on the major surface 810 to 0 volts and setting conductors on the major surface 820 to +10 volts, as shown in Figure 8f, will cause all of the varactors to be reverse biased and this will allow a certain resonance frequency to pass through the entire TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied to achieve desired resonance frequency.

Ih this embodiment, the TFSS can be set into an opaque (off) state. The opaque state is achieved by forward biasing the varactors, as shown in Figure 8g, which shorts across the continuously conductive loop. Setting conductors on major surface 810 to 0 volts and setting conductors on major surface 820 to -1 volts, as shown in Figure 8g, will cause all of the varactors to be forward biased thereby blocking all the resonance frequencies from propagating though the TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied and still cause all of the varactors to be forward biased.

It should be apparent that this embodiment could be implemented in other ways.

For example, the TFSS includes a circuit board 900, with an array of conductors 940a-d, 930a-d on the major surface 910, an array of conductors 960a-c, 970a-c, varactors 980 oft the major surface 920 and vias 995 connecting major sides 910 and 920 as shown in Figure 9a-c. Figure 9a shows the side view of the substøtte 900.

Figure 9b shows a schematic of a circuit on the major surface 910. The major surface 910 has conductors 930a-d running along the width of the major surface 910 and conductors 940a-d running along the length of the major surface 910 connecting the conductors 930a-d, as shown in Figure 9b.

Figure 9c shows a schematic of a circuit on the major surface 920. The major surface 920 has a plurality of oppositely oriented, interconnected varactors 980 organized in rows where the orientation of the varactors in one row is a mirror image of the varactors in the neighboring row, as shown in Figure 9c. Conductors 970a-c run along the length of the ^' major surface 920 between the rows of varactors 980. Conductors 960a-c run along the width of the major surface 920 between the varactors 980 connecting the conductors 970a-c, as shown in Figure 9c.

Although the conductors in Figures 9b and 9c are represented as straight lines, it is to be understood that the conductors can have different shapes, including but not limited to straight lines, crenulated lines and/or wavy lines, for this technology to work.

Although the conductors in Figures 9b and 9c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors.

Although conductors 930a-d appear to be perpendicular to conductors 940a-d in Figure 9b it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary. Although conductors 960a-c appear to be perpendicular to conductors 970a-c in Figure 9c it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary.

Structure 990 in Figure 9d shows an overlay of the circuit on the major surface 910 and the circuit on the major surface 920. Conductors on major surface 910 are oriented at an angle to the conductors on the major surface 920. Although the conductors on the major surface 910 are depicted at a 90° angle to the conductors on the major surface 920 as shown in structure 990 in Figure 9d, it needs to be appreciated that the angle can be varied.

Vias 995 connect the varactors 980 on the major surface 920 to the point of intersection . of conductors 930a-d and 940a-d on the major surface 910, shown in Figure 9d.

In another example, the TTSS includes a circuit board 1000, with an array of conductors l040a-d, 1030a-d on the major surface 1010, an array of conductors 1060a-c, 1070a-c on the major surface 1020, varactors 1080 on the major surface 1025 and vias 1095 and 1096 connecting major sides 1010, 1025 and 1020 as shown in Figure 10a-d. Figure 10a shows the side view of the substrate 1000.

Figure 10b shows a schematic of a circuit on the major surface 1010. The major surface 1010 has conductors 1030a-d running along the width of the major surface 1010 and conductors 1040a-d running along the length of the major surface 1010 connecting the conductors 1030a-d, as shown in Figure 10b.

Figure 10c shows a schematic of a circuit on the major surface 1020. The major surface 1020 has conductors 1070a-c running along the length of the major surface 1020 and conductors 1060a-c running along the width of the major surface 1020 connecting the conductors 1070a-c, as shown in Figure 10c. Figure 1Od shows a schematic of a circuit on the major surface 1025. The major surface 1025 has a plurality of oppositely oriented, interconnected varactors 1080, as shown in Figure 1Od.

Vias 1095 connect the varactors 1080 on the major surface 1025 to the point of intersection of conductors 1030a-d and 1040a-d on the major surface 1010, shown in Figure 1Oe.

Vias 1096 connect the varactors 1080 on the major surface 1025 to the point of intersection of conductors 1070a-c and 1060a-c on the major surface 1020, shown in Figure 1Oe.

Although the conductors in Figures 10b and 10c are represented as straight lines, it is to be understood thaf the conductors can have different shapes, including but not limited to straight lines, crenulated lines and/or wavy lines, for this technology to work.

Although the conductors in Figures 10b and 10c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors.

Although conductors 1030a-d appear to be perpendicular to conductors 1040a-d in Figure 10b it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary.

Although conductors 1060a-c appear to be perpendicular to conductors 1070a-c in Figure 10c it is to be understood that these conductors do not have to be perfectly perpendicular for this technology to work. The angle between the intersecting conductors may vary. Structure 1090 in Figure 1Oe shows an overlay of the circuit on the major surface 1010, the circuit on the major surface 1025 and the circuit on the major surface 1020. Conductors on major surface 1010 are oriented at an angle to the conductors on the major surface 1020. Although the conductors on the major surface 1010 are depicted at a 90° angle to the conductors on the major surface 1020 as shown in structure 1090 in Figure 1Oe, it needs to be appreciated that the angle can be varied.

These are just some of the examples of implementing this embodiment; there are other implementations available although not specifically listed here.

In another embodiment, the TFSS includes a circuit board 1100, with an array of conductors 1130a-h and varactors 1150 on the major surface 1110, an array of conductors 114Oa-It on the major surface 1120 and vias 1160 connecting major sides 1110 and 1120 as shown as shown in Figure lla-c. Figure 11a shows the side view of the substrate 1100.

Figure lib shows a schematic of a circuit on the major surface 1110. The major surface 1110 has a plurality of oppositely oriented, interconnected varactors 1150 organized in columns where the orientation of the varactors in one column is a mirror image of the varactors in the neighboring column, as shown in Figure lib. Conductors 1130a-h run along the width of the major surface 1110 between the columns of varactors 1150, as shown in Figure lib.

Figure lie shows a schematic of a circuit on the major surface 1120. The surface 1120 has conductors 1140a!-h running across the length surface 1120, as shown in Figure lie.

Although (he conductors in Figures lib and lie are represented as straight lines, it is to be understood that the conductors can have different shapes, including but not limited to straight lines, crenulated lines and/or wavy lines, for this technology to work. Although the conductors in Figures lib and lie are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors.

Structure 1170 in Figure Hd shows an overlay of the circuit on the major surface 1110 and the circuit on the major surface 1120. Conductors on major surface 1110 are oriented at an angle to Hie conductors on the major surface 1120. Although the conductors on the major surface 1110 are depicted at a 90° angle to the conductors on the major surface 1120 as shown in structure 1170 in Figure Hd, it needs to be appreciated that the angle can be varied.

Vias 1160 connect the varactors 1150 on the major surface 1110 to conductors on the major surface 1120, shown in Figure Hd.

The lattice period of structure 1170 is represented by distance 6B and 6C as shown in Figures Hd. For this technology to work, the distances 6B and 6C can range from 1/15 of the wavelength to 1/2 of the wavelength. It needs to be appreciated that the distances 6B and 6C do not have to be equal for this technology to work.

The thickness 6A of the circuit board HOO, shown in Figure Ha, is sufficiently small to produce capacitive coupling between the conductors on major surface 1110 and the conductors on major surface 1120. The capacitive coupling between conductors depends on the distance between the conductors and the width of the conductors. In this embodiment, the width of all the conductors and thickness 6A are matched so as to produce capacitive coupling between the conductors on major surface 1110 and the conductors on major surface 1120.

Structure 1170 was modeled using Ansoft HFSS software. See Figure He. In the first simulation, the lattice period was set at 6B=6C =lcm, the conductors were modeled at lmm width, and the substrate was modeled at 6A=lmm thickness. The varactors were modeled as a cube of dielectric material whose dielectric constant was tuned from 1 to 64 by factors of 2. Increasing the dielectric constant from 1 to 64 tuned the resonance frequency of the surface from 8 Ghz down to about 2 Ghz. In the second simulation, the lattice period was modeled at 6B=SC =lcm, the conductors were modeled at lmm widih, and the substrate was modeled at 6A=7mm thickness. The varactors were modeled as a cϊibe of dielectric material whose dielectric constant was 8. As can be seen by the results, shown in Figure lie, this design is more resistant to variations in the substrate thickness. There was only minor degradation of transmission magnitude as the substrate thickness was increased.

Applying voltages to conductors on each major surface of the substrate controls the propagation of different frequencies through the TFSS. Depending on .the voltages applied, the capacitance of the varactors is tuned and the resonance frequency of the TFSS is adjusted. Setting bias wires 1130a-h to 0 volts and setting bias wires 114Oa-Ii to +10 volts, as shown in Figure Hf, will cause all of the varactors to be reverse biased and this will allow a certain resonance frequency to pass through the entire TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied to achieve desired resonance frequency.

In this embodiment the TFSS can be set into an opaque (off) state. The opaque state is achieved by forward biasing the varactors, as shown in Figure Hg, which shorts across the continuously conductive loop. Setting conductors 1130a-h to 0 volts and setting conductors 650a~c and 680a-c to -1 volts, as shown in Figure Hg, will cause all of the varactors to be forward biased, thereby blocking all the resonance frequencies from propagating though the TFSS. The voltage numbers are just provided as an example; the voltage numbers could be varied and still cause all of the varactors to be forward biased.

In this embodiment, different regions of the TFSS can also be tuned to propagate different resonance frequencies and be set to an opaque state. Setting conductors 1130d-e to 0 volts and setting conductors 1140d-e to +10 volts will cause varactors in region R39 to be reverse biased and this will allow a resonance frequency with horizontal and vertical polarization HVF4 to propagate through the R39 region of TFSS, as shown in Figure Hg. Setting conductosr 1130a-c and 1130f-h to +5.5 volts and conductors 114fla-c and 1140f-h to 4.5 volts will cause varactors in region R31, R33, R35 and R37 to be forward biased, thereby blocking the propagation of all horizontal and vertical resonance frequencies through the R31, R33, R35 and R37 regions of TFSS, as shown in Figure 6g. As a by-product, varactors in the regions R32 and R36 are also reverse biased and this will allow a resonance frequency with horizontal and vertical polarization HVFS to propagate through the R32 and R36 region of TFSS, as shown in Figure Hg. Varactors in the regions R38 and R34 are also reverse biased and this will allow a resonance frequency with horizontal and vertical polarization HVF6 to propagate through the R38 and R34 region of TFSS, as shown in Figure Hg. The voltage numbers are just provided as an example. A person familiar with this technology would know that the Voltage numbers could be varied to achieve any desired resonance frequency. The size and^* shape of the regions that allow the resonance frequencies to propagate or not propagate through TFSS shown here are just provided as an example. The size and shape of these regions can be adjusted by applying appropriate voltages to the appropriate conductors.

It should be apparent that this embodiment could be implemented in other ways.

For example, the TFSS includes a circuit board 1200, with an array of conductors 1230a- Ii on the major surface 1210, an array of conductors 1240a-h and varactors 980 on the major surface 1220, and vias 1260 connecting major sides 1210 and 1220 as shown in Figure 12a-c. Figure 12a shows the side view of the substrate 1200,

Figure 12b shows a schematic of a circuit on the major surface 1210. The major surface 1210 has conductors 1230a-h running along the width of the major surface 1210, as shown in Figure 9b.

Figure 12c shows a schematic of a circuit on the major surface 1220. The major surface 1220 has a plurality of oppositely oriented, interconnected varactors 1250 organized in rows where the orientation of the varactors in one row is a mirror image of the varactors in. the neighboring row, as shown in Figure 12c. Conductors 1240a~h run along the length of the major surface 1220 between the rows of varactors 1250, as shown in Figure 12c.

Although the conductors in Figures 12b and 12c are represented as straight lines, it is to be understood that the conductors ban have different shapes, including but not limited to straight lines, crenulated lines and/or wavy lines, for ibis technology to work.

Although the conductors in Figures 12b and 12c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance- between the conductors may vary throughout the length of the conductors.

Structure 1270 in Figure 12d shows an overlay of the circuit on the major surface 1210 and the circuit on the major surface 1220. Conductors on major surface 1210 are oriented at an angle to the conductors on the major surface 1220. Although the conductors on the major surface 1210 are depicted at a 90° angle to the conductors on the major surface 1220, as shown in structure 1270 in Figure 12d, it needs to be appreciated that the angle can be varied.

Vias 1260 connect the varactors 1250 on the major surface 1220 to conductors on the major surface 1210, shown in Figure 12d.

In another example, the TFSS includes a circuit board 1300, with an array of conductors 1330a-h on the major surface 1310, an array of conductors 1340a-h on the major surface 1320, varactors 1350 on the major surface 1325, and vias 1360 and 1365 connecting major sides 1310, 1325 and 1320 as shown in Figure 13a-d. Figure 13a shows the side view of the substrate 1000. Figure 13b shows a schematic of a circuit on the major surface 1310. The major surface 1310 has conductors 1330a-h running along the width of the major surface 1310, as shown in Figure 13b.

Figure 13c shows a schematic of a circuit on the major surface 1320. The major surface 1320 has conductors 134Oa-Ii running along the length of the major surface 1320, as shown in Figure 13c.

Figure 13d shows a schematic of a circuit on the major surface 1325. The major surface 1325 has a plurality of oppositely oriented, interconnected varactors 1350, as shown in Figure 13d.

Vias 1360 connect the varactors 1350 on the major surface 1025 to the conductors 1330a- b. on the major surface 1310, shown in Figure 13e.

Vias 1365 connect the varactors 1500 on the major surface 1025 to the conductors 1340a- h on the major surface 1320, shown in Figure 13e.

Although the conductors in Figures 13b and 13c are represented as straight lines, it is to be understood that the conductors can have different shapes, including but not limited to straight lines, crenulated lines and/or wavy tines, for this technology to work.

Although the conductors in Figures 13b and 13c are represented as parallel lines, it is to be understood that the conductors do not have to be perfectly parallel for this technology to work. The distance between the conductors may vary throughout the length of the conductors.

Structure 1370 in Figure 13d shows an overlay of the circuit on the major surface 1310, • the circuit on the major surface 1325, and the circuit on the major surface 1320. Conductors on major surface 1310 are oriented at an angle to the conductors on the major surface 1320. Although the conductors on the major surface 1310 are depicted at a 90° angle to the conductors on the major surface 1320, as shown in structure 1370, in Figure 13d, it needs to be appreciated that the angle can be varied.

These are just some of the examples of implementing this embodiment; there are other implementations available although riot specifically listed here.

While several illustrative embodiments of the invention have been shown and described, numerous variations and alternative embodiments will occur to those skilled in the art. Such variations and alternative embodiments are contemplated, and can be made without departing from the scope of the invention as defined in the appended claims.

Claims

What is claimed is:

1. A device, comprising:

a first substrate;

a first array of elongated, generally parallel to each other, conductors disposed along a

length of a first major surface of the first substrate;

a second array of elongated, generally parallel to each other, conductors disposed along a

width of a second major surface of the first substrate so as to be capacitively coupled and at a first angle to conductors in the first array; and

a plurality of first varactors containing an elongated axes and coupling the conductors.

2. The device of Claim 1, wherein the first angle is 90 degrees.

3. The device of Claim 1 or 2, further comprising a power supply circuit capable of supplying a plurality of voltages to conductors in the first array and the second array.

4. The device of any one of Claims 1 -3, wherein the plurality of first varactors are disposed on the first major surface of the first substrate and coupling neighboring ones of the conductors in the first array.

5. The device of Claim 4, further comprising a plurality of second varactors containing an elongated axes and disposed on the second major surface of the first substrate and coupling neighboring ones of the conductors in the second array, wherein the elongated axes of the first varactors are at a second angle to the elongated axes of the second varactors.

6. The device of Claim 5, wherein the elongated axes of the first varactors are disposed orthogonally to the elongated axes of the second varactors.

7. The device of any one of Claims 4-6, further comprising a plurality of vias coupling the plurality of first varactors to the conductors in the second array.

8. The device of any one of Claims 1-3, wherein the plurality of first varactors are disposed on the second major surface of the first substrate and coupling neighboring one of the conductors in the second array.

9. The device of Claim 8, further comprising a plurality of vias coupling the plurality of first varactors to the conductors in the first array.

10. The device of any one of Claims 1-3, further comprising:

a plurality of first vias;

a plurality of second vias; and

a second substrate comprising a major surface;

wherein the plurality of the first varactors are disposed on the major surface of the second substrate and the plurality of the first varactors are coupled to the conductors in the first array by the plurality of first vias and the plurality of the first varactors are coupled to the conductors in the second array through the plurality of second vias.

11. The device of any one of Claims 1-10, wherein a first distance between the conductors in the first array is between 1/15 of a wavelength and 1/2 of the wavelength and a second distance between the conductors in the second array is between 1/15 of a wavelength and 1/2 of the wavelength.

12. The device of Claim 11, wherein the first distance is 1 cm and the second distance is 1 cm.

13. The device of any one of Claims 1-12, wherein an opaque state is achieved by forward-biasing the plurality of first varactors.

14. The device of Claim 5, wherein an opaque state is achieved by forward-biasing the plurality of first varactors and the plurality of second varactors.

15. The device of Claim 7, wherein an opaque state is achieved by forward-biasing the plurality of first varactors.

16. The device of Claim 1, said device being a tunable selective surface.

17. The device of Claim 1, said device being a tunable frequency selective surface for covering an antenna.

18. A device, comprising:

a first substrate;

a first array of elongated, generally parallel to each other, conductors disposed along a length

of a first major surface of the first substrate;

width of the first major surface of the first substrate and coupled to the first array of conductors at a first angle;

a third array of elongated, generally parallel to each other conductors disposed along a width

of a second major surface of the first substrate at a second angle to conductors in the first array;

a fourth array of elongated, generally parallel to each other, conductors disposed along a length of the second major surface of the first substrate and coupled to the second array of conductors at a third angle;

a plurality of first vias; and a plurality of first oppositely oriented in series varactors containing an elongated axes and coupling the conductors.

19. The device of Claim 18, wherein the first angle is 90 degrees.

20. The device of Claim 18, wherein the second angle is 90 degrees.

21. The device of Claim 18, wherein the third angle is 90 degrees.

22. The device of any one of Claims 18-21, further comprising

a power supply circuit capable of supplying a first voltage to conductors disposed on the first major surface; and

a second voltage to conductors disposed on the second major surface.

23. The device of any one of Claims 18-22, wherein the plurality of first oppositely oriented in series varactors are disposed on the first major surface and coupling neighboring ones of the conductors in the first array.

24. The device of Claim 23, further comprising

a plurality of second oppositely oriented in series varactors containing an elongated axes and disposed on the second major surface and coupling neighboring ones of the conductors in the third array, wherein the elongated axes of the first oppositely oriented in series varactors are at a fourth angle to the elongated axes of the second oppositely oriented in series varactors; and

a plurality of second vias coupling the first surface to the second surface;

wherein the plurality of first vias couple the second array of conductors to the plurality of

second oppositely oriented in series varactors and the plurality of first vias couple the fourth array of conductors to the plurality of first oppositely oriented in series varactors.

25. The device of Claim 24, wherein the elongated axes of the plurality of first oppositely oriented in series varactors are disposed orthogonally to the elongated axes of the plurality of second oppositely oriented in series varactors.

26. The device of Claim 18, wherein the plurality of first vias couple the conductors on the second major surface to the first major surface and the plurality of first oppositely oriented in series varactors couple the conductors on the first major surface to the plurality of first vias.

27. The device of Claim 18, wherein the plurality of first vias couple the conductors on the first major surface to the second major surface and the plurality of first oppositely oriented in series varactors couple the conductors on the second major surface to the plurality of first vias.

28. The device of Claim 18, further comprising:

a plurality of second vias; and

a second substrate comprising^ major surface; _ __ _ _ __ __ -

wherein the plurality of first oppositely oriented in series varactors are disposed on the major

surface of the second substrate and the plurality of first oppositely oriented in series varactors are coupled to conductors on the first major surface through the plurality of first vias and the plurality of first oppositely oriented in series varactors are coupled to conductors on the second maj or surface though the plurality of second vias.

29. The device of Claim 18, wherein a first distance between the conductors in the first array is between 2/15 of a wavelength and 1 wavelength and a second distance between the conductors in the third array is between 2/15 of a wavelength and 1 wavelength.

30. The device of Claim 29, wherein the first distance is 1 cm and the second distance is 1 cm.

31. The device of Claim 18, wherein an opaque state is achieved by forward-biasing the plurality of first oppositely oriented in series varactors.

32. The device of Claim 24, wherein an opaque state is achieved by forward-biasing the plurality of first oppositely oriented in series varactors and the plurality of second oppositely oriented in series varactors.

33. The device of Claim 26, wherein an opaque state is achieved by forward-biasing the plurality of first oppositely oriented in series varactors.

34. The device of Claim 27, wherein an opaque state is achieved by forward-biasing the plurality of first oppositely oriented in series varactors.

35. The device of Claim 28, wherein an opaque state is achieved by forward-biasing the plurality of first oppositely oriented in series varactors.

36. The device of Claim 18, is a tunable frequency selective surface.

37. The device of Claim 18, is a tunable frequency selective surface for covering an antenna.

38. A method of achieving an opaque state in at least a region of a tunable frequency selective surface, the method comprising:

applying a plurality of voltages to conductors disposed on a first major surface and on a

second major surface of the tunable frequency selective surface so as to cause a plurality of varactors coupling the conductors to be forward-biased and to cause the at least a region of the tunable frequency selective surface to be in the opaque state.

39. The method of claim 38, wherein applying the plurality of voltages comprises:

applying a first voltage to alternating conductors disposed along a length of the first major surface and alternating conductors disposed along a width of the second major surface; applying a second voltage to remaining conductors disposed along the length of the first

major surface so as to cause the plurality of varactors coupling the conductors on the first major surface to be forward-biased; and

applying the second voltage to remaining conductors disposed along the width of the second

major surface so as to cause the plurality of varactors coupling the conductors on the second major surface to be forward-biased.

40. A method of tuning at least a region of a tunable frequency selective surface, the method comprising:

second major surface of the tunable frequency selective surface so as to cause aplurality of varactors coupling the conductors to be reverse biased and to cause the at least a region of the tunable frequency selective surface to be tuned to a frequency.

41. The method of Claim 40, wherein applying the plurality of voltages comprises:

applying a first voltage to alternating conductors disposed along a length of the first major surface and alternating conductors disposed along a width of the second major surface;

applying a second voltage to remaining conductors disposed along the length of the first

major surface so as to cause the plurality of varactors coupling the conductors on the first major surface to be reverse biased and tuned to a resonance frequency; and

major surface so as to cause the plurality of varactors coupling the conductors on the second major surface to be reverse biased and tuned to the resonance frequency.

42. Amethod of tuning each region of a tunable frequency selective surface to a different resonance frequency, the method comprising:

partitioning a tunable frequency selective surface into a plurality of regions, wherein each

region of the tunable frequency selective surface contains a first major surface and a second major surface;

determining which of the regions of the tunable frequency selective surface are to be tuned

to which resonance frequency;

providing the first major surface of each of the regions with a distinct first voltage;

applying the distinct first voltage to alternating conductors in each one of the regions, wherein the alternating conductors are disposed along a length of the first major surface;

providing the first major surface of each of the regions with a distinct second voltage;

applying the distinct second voltage to remaining conductors in each one of the regions, so

as to cause varactors in each of the regions to be reverse biased and tuned to a resonance frequency determined for that region, wherein the remaining conductors are disposed along the length of the first major surface;

providing the second major surface of each of the regions with a distinct third voltage;

applying the distinct third voltage to alternating conductors in each one of the regions,

wherein the alternating conductors are disposed along a width of the second major surface;

providing the second major surface of each of the regions with a distinct fourth voltage;

applying the distinct fourth voltage to remaining conductors in each one of the regions, so

as to cause varactors in each of the regions to be reverse biased and tuned to a resonance frequency determined for that region, wherein the remaining conductors are disposed along the width of the second major surface.

43. The method of Claim 42, wherein the conductors disposed on the first surface are capacitively coupled to conductors disposed on the second surface.

44. The method of Claim 42, wherein the first major surface and the second major surface of each of the regions are provided with the distinct first voltage that is equal to the distinct third voltage and the distinct second voltage that is equal to the distinct fourth voltage.

45. The method of Claim 38, wherein applying the plurality of voltages comprises;

applying a first voltage to conductors disposed on the first major surface;

applying a second voltage to conductors disposed on the second major surface so as to cause

a plurality of oppositely oriented in series varactors to be forward-biased;

wherein the plurality of oppositely oriented in series varactors couple the conductors on the

first major surface to conductors on the second major surface.

46. The method of Claim 40, wherein applying the plurality of voltages comprises:

applying a first voltage to conductors disposed on the first major surface;

the plurality of oppositely oriented in series varactors to be reverse biased;

first major surface to conductors on the second major surface.

47. The method of Claim 38, wherein applying the plurality of voltages comprises:

applying a first voltage to conductors disposed on the first major surface so as to cause a

plurality of first oppositely oriented in series varactors coupling the conductors on the first major surface to be forward-biased;

a plurality of second oppositely oriented in series varactors coupling the conductors on the second major surface to be forward-biased;

wherein the conductors on the first major surface are coupled to the plurality of second

oppositely oriented in series varactors and the conductors on the second major surface are coupled to the plurality of first oppositely oriented in series varactors.

48. The method of Claim 40, wherein applying the plurality of voltages comprises:

plurality of first oppositely oriented in series varactors coupling the conductors on the first major surface to be reverse biased;

a plurality of second oppositely oriented in series varactors coupling the conductors on the second major surface to be reverse biased;

49. The method of tuning each region of a tunable frequency selective surface to a different resonance frequency or an opaque state, the method comprising:

to a resonance frequency;

to the opaque state;

applying the distinct first voltage to alternating conductors in each one of the regions,

wherein the alternating conductors are disposed along a length of the first major surface;

as to cause varactors in each of the regions to be reverse biased and tuned to a resonance frequency or the opaque state as determined for that region, wherein the remaining conductors are disposed along the length of the first major surface;

providing the second major surface of each of the regions with a distinct fourth voltage; applying the distinct fourth voltage to remaining conductors in each one of the regions, so

as to cause varactors in each of the regions to be reverse biased and tuned to a resonance frequency or the opaque state as determined for that region, wherein the remaining conductors are disposed along the width of the second major surface.