Patent Description:
The general field of the invention relates to unique electromagnetic components having electrical characteristics that are variable. The components can be used for radiating and non-radiating electromagnetic devices. Embodiments of the invention also relate to electrical devices having elements structured on LCD, such that the operation of the LCD changes the characteristics of the electrical devices.

Various electrical devices/components are known in the art for receiving, transmitting, and manipulating electrical signals and electro-magnetic radiation. The feed or transmission lines or network conveys the signal between the radiating antenna and the transceiver. However, the feed network may comprise different type of transmission lines, bends, power splitters, filters, ports, phase shifters, frequency shifters, attenuators, couplers, capacitors, inductors, diplexers, hybrids of beam forming networks, and may also include radiating elements. Similar arrangement may be in transmission lines which do not transmit wirelessly, e.g., coaxial transmission of television programming. These elements may be static or variable. For example, a capacitor may have a given, i.e., static capacity, or it may be variable, e.g., by mechanically changing the distance between the capacitor plates. Other devices, such as transmission lines, for example, are static in that their electrical characteristics (such as resistance or impedance) do not change.

While the devices disclosed herein are generic and may be applicable to multitude of applications, one particular application that can immensely benefit from the subject devices are the transmission of signals in mobile devices which operate in several frequencies. In such devices, an elaborate network of switches and filters are used to couple one of several transceivers to the antenna. Such network increases the cost of the devices and leads to losses which attenuate the signal, thus requiring increasing the power of the transmitter to thereby consume more battery power.

There are several types of microstrip antennas (also known as a printed antennas), the most common of which is the microstrip patch antenna or simply patch antenna. A patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating substrate. Some patch antennas eschew a substrate and suspend a metal patch in air above a ground plane using dielectric spacers; the resulting structure is less robust but provides better bandwidth. Because such antennas have a very low profile, are mechanically rugged and can be conformable, they are often mounted on the exterior of aircraft and spacecraft, or are incorporated into mobile radio communications devices.

An advantage inherent to patch antennas is the ability to have polarization diversity. Patch antennas can easily be designed to have Vertical, Horizontal, Right Hand Circular (RHCP) or Left Hand Circular (LHCP) Polarizations, using multiple feed points, or a single feedpoint with asymmetric patch structures. This unique property allows patch antennas to be used in many types of communications links that may have varied requirements.

<FIG> illustrates an example of a microstrip antenna of the prior art. As shown in <FIG>, four conductive patches <NUM>-<NUM> are provided over insulating substrate <NUM>. A base "common" ground conductor is provided below the dielectric <NUM>, but is not shown in <FIG>. Conductive lines <NUM>'-<NUM>' provide electrical connection to main line <NUM>, which is connected to a central feed line <NUM>.

A liquid crystal display (commonly abbreviated LCD) is a thin, flat display device made up of any number of color or monochrome pixels arrayed in front of a light source or reflector. Each pixel of an LCD consists of a layer of perpendicular molecules aligned between two transparent electrodes, and two polarizing filters, the axes of polarity of which are perpendicular to each other. The liquid crystal material is treated so as to align the liquid crystal molecules in a particular direction. This treatment typically consists of a thin polymer layer that is unidirectionally rubbed using a cloth (the direction of the liquid crystal alignment is defined by the direction of rubbing).

Before applying an electric field, the orientation of the liquid crystal molecules is determined by the alignment at the surfaces. In a twisted nematic device (the most common liquid crystal device), the surface alignment directions at the two electrodes are perpendicular, and so the molecules arrange themselves in a helical structure, or twist. Because the liquid crystal material is birefringent, light passing through one polarizing filter is rotated by the liquid crystal helix as it passes through the liquid crystal layer, allowing it to pass through the second polarized filter. Half of the light is absorbed by the first polarizing filter, but otherwise the entire assembly is transparent.

When a voltage is applied across the electrodes, a torque acts to align the liquid crystal molecules parallel to the electric field, distorting the helical structure (this is resisted by elastic forces since the molecules are constrained at the surfaces). This reduces the rotation of the polarization of the incident light, and the device appears darker. If the applied voltage is large enough, the liquid crystal molecules are completely untwisted and the polarization of the incident light is not rotated at all as it passes through the liquid crystal layer. This light will then be polarized perpendicular to the second filter, and thus be completely blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts, correspondingly illuminating the pixel.

<FIG> illustrates a cross-section of an LCD of the prior art. As shown in <FIG>, the LCD <NUM> comprises a back panel <NUM> which may be glass, a front panel <NUM> which is also generally made of glass, a liquide crystal <NUM> positioned between the two panels, a back electrode <NUM>, which may be indium/titanium/oxide (ITO), aluminum, etc, and front electrodes <NUM>, which are coupled to potential <NUM> and are generally made of ITO. The potential <NUM> may be applied individually to each electrode <NUM>. As potential is applied to an electrode <NUM>, the liquide crystal below it changes its orientation and, thereby changes the local dielectric constant between the powered electrode and the section of the rear electrode corresponding to the area of the front electrode. Document <CIT> describes an antenna and antenna array. Radiating elements and corresponding feed lines are provided over a variable dielectric constant material sandwiched between two panels. The sandwich may be in the form of an LCD. The dielectric constant in a selected area under the conductive line can be varied to control the phase of the radiating element. The dielectric constant in a selected area under the radiating element can be varied to control the resonance frequency of the radiating element. The dielectric constant in a selected area under the conductive line can be varied to also control the polarization of the radiating element. "<NPL>, describes a tunable parallel-coupled microstrip lines filter based on nematic liquid crystals (LC) substrate for applications at mm-wave frequencies. <CIT> describes a frequency variable filter and a variable resonator with a simple configuration that can electrically control the center frequency of the frequency variable filter and the band or the resonance frequency of the resonator without mounting active components or the like on the frequency variable filter and the variable resonator. This variable resonator is provided with a dielectric material layer made of a dielectric material whose dielectric constant changes with an electric control signal, a couple of electrodes opposed to each other via the dielectric material layer or placed in parallel on one side of the dielectric material layer, and a power source for applying a voltage to a couple of the electrodes. Thus the variable resonator controls the voltage applied from the power source to a couple of the electrodes to change the dielectric constant of the dielectric material layer thereby varying the resonance frequency.

The dependent claims provide embodiments thereof.

The accompanying drawings, which are incorporated in and constitute a part of this specification and, together with the description, serve to explain and illustrate principles. The drawings are intended to illustrate major features of the examples and exemplary embodiments in a diagrammatic manner. The drawings are not intended to depict every feature of actual embodiments nor relative dimensions of the depicted elements, and are not drawn to scale.

Various embodiments of the invention are generally directed to a structure of electronic devices or components provided over a variable dielectric structure, providing variable control over the operating characteristics of the components. In the context of the description of the various embodiments, an LCD forms the variable dielectric structure so as to simplify the explanation; however, other variable dielectric elements may be used. For example, while an LCD may be used for the inventive electronic devices or components, the LCD need not include an illumination source unless it is also used to project an image. The various embodiments described herein may be used, for example, in connection with stationary and/or mobile platforms. Of course, the various electronic devices or components described herein may have other applications not specifically mentioned herein. Various applications where the inventive electronic devices or components may be particularly beneficial include smartphones, pads, laptops, etc. The various techniques may also be used for two-way communication and/or other receive-only applications.

The description of aspects of the invention will proceed with reference to different embodiments. Each description of a certain embodiment may highlight specific features. However, it should be understood that the described features may be incorporated in other embodiments as well and that different combination of these features may be assembled to form further embodiments.

<FIG> depicts an example of a power splitter <NUM> according to an example useful for understanding the invention. The power splitter <NUM> consists of a conductive input line <NUM> having input port <NUM>, an optional expanded coupler <NUM>, a splitter conductive line <NUM> having a first output port <NUM> and a second output port <NUM>, all provided on an insulating substrate <NUM>. Conductive input line <NUM>, expanded coupler <NUM>, and splitter conductive line <NUM> may all be strips of conductive material, e.g., copper or aluminum. In one implementation the substrate <NUM> is an LCD, while in others it is an insulating substrate having variable dielectric constant regions <NUM>, <NUM> and <NUM> having addressable electrodes.

Using this configuration, the power input at the input port <NUM> is split into spreader line <NUM> and some power is output at the first output port <NUM> and the rest of the power is output at the second output port <NUM>. In its natural un-energized condition, the split of the power is <NUM>-<NUM> (assuming a symmetrical physical structure), meaning half of the power is output at the first output port <NUM> and half of the power is output at the second output port <NUM>, and the power output from the first and second output ports is in phase. However, when electrical potential is applied to the variable dielectric elements <NUM>, <NUM>, and/or <NUM>, the power output and the power split can be varied. That is, by separately changing the dielectric constant of the material <NUM>, <NUM>, and/or <NUM>, the impedance of the corresponding element can be changed.

More specifically, the phase, Φ, can be expressed as: <MAT> wherein λg is the wavelength in the matter, i.e., conductive line, and d is the length of the propagation line. On the other hand, λg can be expressed as: <MAT> wherein λ<NUM> is the wavelength in air, ε eff the effective dielectric constant as a function of εr, line width, and other physical parameters of the microstrip line, and εr is the dielectric constant of the propagation material. Then the phase can be expressed as: <MAT> Therefore, by separately controlling the dielectric constant of a section of the variable dielectric material <NUM>, <NUM>, and/or <NUM> under each of the corresponding conductive line <NUM> and <NUM>, the signal propagation in the line can be changed. Also, the phase can also be controlled by the length, d, of the section of the variable dielectric material that is controlled. That is, each of variable dielectric material <NUM>, <NUM>, and/or <NUM> may have a single addressable electrode such that the entire area of the variable dielectric material <NUM>, <NUM>, and/or <NUM> experiences the same applied voltage potential. Conversely, each of variable dielectric material <NUM>, <NUM>, and/or <NUM> may have a plurality of electrodes, arranged as pixels, each addressed separately so that only a section of the variable dielectric material experiences the applied voltage potential depending on which pixels are being addressed. In this manner, the device is software controlled, since software can be used to address different pixels and thereby modify the behavior of the electrical component.

For example, element <NUM> can serve as an attenuator. When no potential is applied to variable dielectric section <NUM>, all of the supplied power propagates into conductor <NUM>. On the other hand, when potential is applied to variable dielectric <NUM>, the effective inductance of element <NUM> changes, so that attenuator <NUM> can reflect back some of the power, such that not all of the power is delivered to conductor <NUM>, i.e., total output power is attenuated. Similarly, when potential is applied to variable dielectric section <NUM>, it can reflect some of the power, such that less power is output through the first output port <NUM>, meaning the split of power between the first and second output ports can be changed so that one output port receive more power than the other output port. In each of these cases, the amount of power reflected depends on the voltage applied to the electrodes of the variable dielectric and to the effective size of the variable dielectric. The effective size of the variable dielectric can be changed by addressing more or less of the pixels controlling the variable dielectric.

<FIG> illustrate a cross-section of the spreader line <NUM> of the example of <FIG>. In this example, the dielectric constant is controlled using an LCD or any other material having variable dielectric constant that can be controlled using a signal line. In <FIG>, spreader line <NUM> is provided over insulating layer <NUM>, which may be a glass panel, resin, air, etc. Variable dielectric elements <NUM> and <NUM> are provided in insulating layer <NUM> and each is provided over a respective section of the spreader line <NUM>. The liquid crystal may be provided in one or more zones over each section of the spreader line <NUM>. Each of the variable dielectric elements <NUM> and <NUM> is coupled to a respective activation signal line <NUM> and <NUM>. When the potential on any of the signal lines <NUM> and <NUM> changes, the dielectric constant of the corresponding variable dielectric element <NUM> and <NUM> changes, thereby inducing a phase change in a corresponding section of the spreader line <NUM>. The phase change can be controlled by choosing the amount of voltage applied to the transparent electrode signal lines <NUM> and <NUM>, i.e., controlling εr, and also by controlling the number of dielectric elements the voltage is applied to, i.e., controlling the effective length of d.

It should be noted that the example is not limited to the use of an LCD. That is, any material that exhibits a controllable variable dielectric constant can be used. For example, any ferroelectric material may be used instead of the liquid crystal. The example shown here uses LCD, as the LCD technology is mature and readily available, which makes the example very attractive and easy to implement.

<FIG> illustrates a construction of a variable filter according to one embodiment. This particular example illustrates a four-element filter, also referred to as a four-level filter. Of course, the number of elements or levels can be changed to fit any desired implementation. In <FIG> four conductive lines <NUM>, <NUM>, <NUM> and <NUM> are formed over a dielectric plate <NUM>. An input <NUM> is connected to one side of conductive line <NUM> and an output <NUM> is connected to one side of conductive line <NUM>. The input <NUM> and output <NUM> may be any standard connectors, such as, e.g., coaxial connectors, SMA (SubMiniature version A) connectors, etc. Also, taps T can be provided at the end of each lines <NUM>, <NUM>, and <NUM>, and each tap may have the same connector as input and output <NUM> and <NUM>. In such a configuration, in essence the filter has one input and four outputs, each output can be tuned to a different frequency and/or phase.

Generally, the inductance of each of the conductive lines <NUM>, <NUM>, <NUM> and <NUM> can be modeled as a series connection of a capacitor and inductor, as shown in callouts <NUM>, <NUM>, <NUM> and <NUM>, respectively. An area or zone having a controllable variable dielectric constant (VDC) is provided under each of the conductive lines: VDC <NUM> is provided under line <NUM>, VDC <NUM> is provided under conductive line <NUM>, VDC <NUM> is provided under conductive line <NUM>, and VDC <NUM> is provided under conductive line <NUM>. Each of the VDC's may have a single electrode or a plurality of electrodes addressed collectively or individually to thereby apply a voltage potential to change the effective dielectric constant of the VDC. By changing the effective dielectric constant of a VDC provided under one of the conductive lines, the effective inductance of the line is changed. A change of the inductance of a line causes a change in the bandwidth of the signal traveling on the line. Since in this embodiment each conductive lines has a VDC zone under it, the bandwidth or each line can be changed, thereby making this filter a variable bandwidth filter. Also, if the VDC under all of the lines is biased, the center of frequency of the filter is changed. Since the voltage may be applied using software to address various electrodes of the VDC's, the filter is software controlled. That is, the bandwidth and center of frequency can be controlled using software to apply various potentials to the VDCs.

In the filter of <FIG> the signal travels from one line to the next via capacitive coupling between the lines. For example, a section of line <NUM> is placed in parallel to a section of line <NUM>, thus forming a capacitor there-between. As the signal travels on line <NUM>, it capacitively couples to line <NUM> and start propagating on line <NUM>. The same goes for the other lines. The efficiency of the coupling depends on the amount of line sections that are overlapped, and the effective separation between these overlapping lines. The effective separation relates to the distance between the lines and the dielectric constant between the lines. The dielectric constant between the lines is controlled by a zone of VDC, such that VDC <NUM> controls coupling between lines <NUM> and <NUM>, VDC <NUM> controls coupling between lines <NUM> and <NUM>, and VDC <NUM> controls coupling between lines <NUM> and <NUM>, as exemplified by callouts <NUM>, <NUM> and <NUM>, respectively. By changing the potential applied to any of VDC <NUM>, <NUM> and <NUM>, the bandpass and the rejection slope of the filter can be varied and controlled. Thus, the filtering characteristics of the filter <NUM> can be made to be software controlled, i.e., by providing software that controls the potential applied to the various VDC's the operation of the filter <NUM> can be controlled.

Another operational characteristic of the filter <NUM> is its center frequency. In static filters the center frequency is a constant. However, in the arrangement of <FIG> the center frequency can be changed by concurrently applying voltage potential to all of the VDC's under the lines and between the lines. Thus, by appropriately controlling the voltage potential on the VDC's of filter <NUM>, one can control its center frequency, its bandwidth, it bandpass, and its rejection slope.

Power dividers (also called power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. A directional coupler designed to split power equally between two ports is called a hybrid coupler. The most common form of directional coupler is a pair of coupled transmission lines. They can be realized in a number of technologies including coaxial and the planar technologies (stripline and microstrip). An implementation in stripline is shown in <FIG> of a quarter-wavelength (λ/<NUM>) directional coupler. The power on the coupled line flows in the opposite direction to the power on the main line, so it is sometimes called a backward coupler. The main line is the section between ports <NUM> and <NUM> and the coupled line is the section between ports <NUM> and <NUM>.

In the example of <FIG>, a main line <NUM> and a coupled line <NUM> are formed on dielectric plate <NUM>. The main line <NUM> and coupled line <NUM> may be, e.g., microstrips on a dielectric plate, printed conductors on a Rogers (FR-<NUM> printed circuit board), etc. In the example of <FIG> port <NUM> is the input of the main line and port <NUM> is the output of the main line, while port <NUM> and port <NUM> are the input and output of the coupled line, respectively. Normally the output at port <NUM> would be in phase with the input at port <NUM>, while the output at port <NUM> would be <NUM><NUM> phase shifted from the input at port <NUM>.

In order to make the coupler of <FIG> variable, a VDC zone <NUM> is provided under dielectric plate <NUM> and is positioned in between the main line <NUM> and coupled line <NUM>. By applying voltage potential onto the electrodes of VDC zone <NUM>, the phase shift on the coupled line can be controlled. Moreover, optionally additional VDC zones <NUM>, <NUM>, <NUM> and <NUM> may be provided under the main and coupled lines to further control the phase shift on each port. For example, by changing the voltage potential on VDC zone <NUM> the inductance of output port <NUM> changes, such that the ratio of output from the main line and coupled line can be changed.

As illustrated by the top callout of <FIG>, the main and coupled lines may be positioned on top of the dielectric plate <NUM>. Conversely, the main and coupled lines may be formed one over each other, with the dielectric plate <NUM>, VDC zone <NUM> and bottom dielectric plate <NUM> in between.

<FIG> illustrates an example for variable three port coupler. As before, all metal lines are formed over a dielectric plate and a VDC's are provided under the dielectric plate. However, for clarity and brevity, the description of the various examples continues without showing or referring to the dielectric plate. Main line <NUM> has input port <NUM> and output port <NUM>, having no phase change. Coupled line <NUM> has output port <NUM>, having variable phase with respect to the signal propagating on main line <NUM>. The phase of the signal on the coupled line <NUM> is controlled by the voltage potential applied to the VDC zone <NUM>.

<FIG> illustrates another example of a four-ports hybrid coupler <NUM>. Without any VDC's the signal input at port <NUM> splits into output to port <NUM> without phase change and into port <NUM> at <NUM> deg phase change. Similarly, a signal input to port <NUM> splits into output to port <NUM> without phase change and into port <NUM> at <NUM> deg phase change. This is captured by the table shown in <FIG>. However, in the example of <FIG> several optional placement for VDC's are shown, all or some of which may be implemented, depending on the desired control over the operation of the hybrid coupler <NUM>.

For example, VDC <NUM> is provided under the line of input port <NUM>. By applying voltage potential to the electrodes of VDC <NUM>, the phase of the input signal can be controlled. Consequently, the phase at both output ports <NUM> and <NUM> would be varied together based on the phase change caused by the voltage potential at VDC <NUM>. This means that the phase at output <NUM> can be different from the phase of the input signal at input port <NUM>. On the other hand, the phase at output <NUM> can be changed independently by voltage potential at VDC <NUM>. Consequently, the phase at output port <NUM> would remain <NUM><NUM> from the input at input port <NUM>, but the phase at output port <NUM> would be different from zero, depending on the voltage potential applied to VDC <NUM>. Additionally, a voltage potential can be applied to the electrodes of VDC <NUM> to vary the phase at output port <NUM> independent of the output at port <NUM>. Thus, the output at port <NUM> can remain at the same phase as the input at port <NUM>, but the output at port <NUM> can be modified from <NUM><NUM> with respect to the input at port <NUM>. The same effect can be applied to the input of input port <NUM> by applying voltage potential to VDC's <NUM>, <NUM> and <NUM>. Moreover, normally an input signal at port <NUM> would be split at equal energies between output ports <NUM> and <NUM>. However, by controlling the voltage potential at VDCs <NUM>, <NUM>, 715A and 715B, the amount of energy delivered to each output port can be changed, thus the amplitude of the output at each port can be controlled.

Examples useful for understanding the invention also provide two-port devices. For example, <FIG> illustrates a phase shifter element <NUM> according to an example useful for understanding the invention. Signal is input at port <NUM> and propagates on conductor line <NUM>. Normally the output signal at port <NUM> would be at constant amplitude and at the same phase as the input signal. However, as shown by the table of <FIG>, as voltage potential is applied to the electrodes of VDC <NUM>, the phase of the output signal at port <NUM> can be changed with respect to the input at port <NUM>.

Another example of a two-port element is shown in <FIG> illustrates an attenuator according to an example useful for understanding the invention. The input signal on port <NUM> traverses main line <NUM> and output at port <NUM> at the same phase, but under controlled amplitude. Specifically, two attenuators are provided on main line <NUM>. The attenuators are made by conductive attenuation patch <NUM> and <NUM>, provided over VDC <NUM> and <NUM>. Depending on the voltage potential applied to the electrodes of VDCs <NUM> and <NUM>, the amplitude of the signal output at port <NUM> can be controlled, i.e., attenuated.

Examples useful for understanding the invention also provide single-port devices. For example, <FIG> illustrates a single port load element <NUM> according to an example useful for understanding the invention. In the example of <FIG> the load is in the form of a variable capacitor at a dead-end of a conductive line <NUM>. Specifically, a capacitor plate <NUM> is formed at and is in electrical contact with a dead-end of main line <NUM>. The ground electrode of the VDC <NUM> may form the complementary capacitor plate, or a complementary capacitor plate can be formed below the VDC <NUM>. The capacitance of this load can be varied by applying voltage potential to the electrodes of the VDC <NUM>.

<FIG> illustrate how elements according to disclosed embodiments can be used to simplify the construction of a switching array, as implemented in, e.g., cellphones. <FIG> illustrates the prior art switching arrangement. As illustrated, in this example both arrangements include four antennas, identified as Tx/Rx1- Tx/Rx4. Each antenna is designed to operate at a different frequency. In the prior art, illustrated in Figure 7A, each antenna is connected to a dedicated fixed filter F1-F4, and each switch is connected to a dedicated switch S1-S4. Then, each two switches are connected to a single intermediate switch, i.e., switches S1 and S2 can be selected by intermediate switch S5 and switches S3 and S4 can be selected by intermediate switch S6. Switches S5 and S6 are connected to master switch S7. Thus, for example, if antenna Tx/Rx1 is to be selected, then switches S7, S5 and S1 are closed, while all other switches are switched to open position. Conversely, if antenna Tx/Rx3 is to be selected, then switches S7, S6 and S3 are closed, while all other switches are switched to open position. Thus, this arrangement requires four fixed filters and seven switches. Conversely, in the embodiment of <FIG>, a single variable filter is connected to all of the antennas Tx/Rx1-Tx/Rx4. Depending on which antenna is selected, a different voltage potential is applied to the electrodes of the VDC of variable filter <NUM>. The variable filter <NUM> may be constructed according to the teachings provided herein using, e.g., the embodiment of <FIG>.

Finally, it should be understood that processes and techniques described herein are not inherently related to any particular apparatus and may be implemented by any suitable combination of components. Further, various types of general purpose devices may be used in accordance with the teachings described herein. It may also prove advantageous to construct specialized apparatus to perform the method steps described herein. The present invention has been described in relation to particular examples, which are intended in all respects to be illustrative rather than restrictive. Those skilled in the art will appreciate that many different combinations of hardware, software, and firmware will be suitable for practicing the present invention.

Claim 1:
An electrical element having variable properties, comprising:
a dielectric panel (<NUM>) having electrically insulating properties;
a bottom dielectric plate (<NUM>; <NUM>);
a conductive line (<NUM>) provided over the dielectric panel (<NUM>);
a variable dielectric zone (<NUM>) provided at a defined area below the conductive line (<NUM>), the variable dielectric zone (<NUM>) comprising a variable dielectric constant material (VDC) sandwiched between the bottom dielectric plate (<NUM>; <NUM>) and the dielectric panel (<NUM>), and having electrodes coupled to a voltage source;
wherein the electrical element comprises:
a variable filter (<NUM>) wherein the conductive line (<NUM>) comprises an input line (<NUM>) of the variable filter (<NUM>), and wherein the variable filter (<NUM>) comprises an output line (<NUM>) provided on top of the dielectric panel (<NUM>), having no ohmic contact to the input line (<NUM>), wherein the variable filter (<NUM>) further comprises a second variable dielectric zone (<NUM>) between the input line (<NUM>) and the output line (<NUM>);
wherein the second variable dielectric zone (<NUM>) is configured to have a changeable potential applied thereto such that a dielectric constant between the input line (<NUM>) and the output line (<NUM>) is controlled by the second variable dielectric zone (<NUM>).