4. Description: TITLE: A method and device for a passive reconfigurable frequency selective surface.

FIELD OF THE INVENTION

The field of the invention relates to the frequency selective surface (FSS) design for wide band tuning. More specifically, a reconfigurable frequency selective surface devoid of active elements exhibiting wide band tuning by varying the gap between the rows vertically with mechanical adjustment

BACKGROUND OF THE INVENTION

Frequency selective surfaces (FSSs) are periodic elements of metallic patches (capacitive FSS) or apertures (inductive FSS) on a substrate, providing total reflection or transmission over the desired frequency range. FSSs are widely used in radomes, spatial filters, spatial phase shifters, polarizer, antenna beam steering applications, dichroic reflector etc., Emerging trends in technologies demand frequency agility in functionality of the electronic systems. The tunability of the frequency characteristics of FSSs makes it suitable for use in adaptive environment. The agility in FSS functioning as EM filters is realized using reconfigurable FSS (RFSS). Current RFSSs involves the use of varactor diodes, MEMS devices or mechanical movements to achieve re-configurability. Problems associated with the conventional tunable FSSs such as longevity, durability, etc., demands new mechanisms to overcome the aforesaid issues.

Many techniques are found in the literature related to RFSS. In most of the cases configurability/variation in the frequency response of the FSS is achieved by introducing certain change in the substrate properties, implementing varactor diodes, using MEMS devices or by mechnical movement. MEMS actuated planar elements are used to realize reconfigurable FSS. Spring resonator element based FSS uses the concept of height adjustment with applied pressure to achieve the ^configurability or to change the frequency response of the FSS. Another technique based on varactor diodes to achieve wide band tuning over 65% is also present in the prior art. Yet another technique for varying the frequency response is achieved by altering the properties of the substrate material is also reported in prior art. The present invention provides single layer wide band tunable FSS achieved by mechanical method.

OBJECTIVE OF THE INVENTION

1. The primary object of the present invention is to design a single layer reconfigurable FSS made of novel unit cells.

2. It is yet another object of the present invention to provide wide band tuning by varying the vertical gap between the rows mechanically.

SUMMARY OF THE INVENTION

It will be understood that this disclosure is not limited to the particular systems, and methodologies described, as there can be multiple possible embodiments of the present disclosure which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present disclosure.

The present invention deals with the design and prototype development of a reconfigurable FSS. A prototype of the reconfigurable FSS consisting of 15 identical array of unit cells each containing 20 elements is developed. The unit cell of the proposed RFSS contains a pair of shorted square loops separated by a uniform distance. Frequency tunability of the proposed RFSS is achieved by varying the vertical gap between the rows mechanically. The present invention provides wide band tuning of the frequency response with its simpler and thin FSS geometry. The FSS offers 20dB attenuation over a wide range from 3.3 GHz to 9.6 GHz. The major contribution of the invention is the design of the RFSSs which involves the displacement of adjacent cells to achieve re-configurability rather than the use of active devices as in the conventional RFSSs

BRIEF DESCRIPTION OF DRAWINGS:

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

Fig 1 illustrates an exemplary embodiment of a unit cell design. . Fig 2 illustrates an exemplary embodiment of the periodic arrangement of RFSS for different k values.

DETAILED DESCRIPTION OF THE INVENTION:

The following detailed description illustrates by way of example and not by way of limitations.

Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shown. Embodiments of the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples and are merely examples among other possible examples.

In the disclosure herein, consideration or use of a particular element number in a given FIGURE or corresponding descriptive material can encompass the same, an equivalent, or an analogous element number identified in another FIGURE or descriptive material corresponding thereto. Some embodiments of this invention, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items.

It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred, systems and methods are now described.

Some embodiments may be described using the expression "one embodiment" or "an embodiment" along with their derivatives. These terms mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment. Further, some embodiments may be described using the expression "coupled" and "connected" along with their derivatives. These terms are not necessarily intended as synonyms for each other. For example, some embodiments may be described using the terms "connected" and/or "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. The term "coupled," however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.

Referring to the drawings, Fig 1, illustrates an exemplary embodiment of a unit cell design 100, wherein the RFSS comprises of a single side printed unit cell dimension of 15mm x 15mm 110 on a single substrate. The unit cell geometry resembles the shape of the shorted square loops. Furthermore, the inner square side dimension L is 4.5mm 115, the gap between the unit cell g is 0.15mm 120 and the width dimension Wl and W3 is 1mm 125 and that of W2 is 3mm 130.

Figure 2 illustrates an exemplary embodiment of the periodic arrangement of RFSS for different k values 200 wherein the reconfigurable FSS comprises of 15 identical array of unit cells 210 each containing 20 elements 215. The unit cell 210 of the said RFSS comprises of a pair of shorted square loops separated by a uniform distance. Frequency tunability of the proposed RFSS is achieved by varying the vertical gap 215 between the rows mechanically. The present invention provides a wide band tuning of the frequency response with its simpler and thin FSS geometry. As mentioned earlier, the FSS offers 20dB attenuation over a wide range from 3.3 GHz to 9.6 GHz. The major contribution of the invention is the design of the RFSSs which involves the displacement of adjacent cells to achieve re-configurability rather than the use of active devices as in the conventional RFSSs

As illustrated in Figure 3 which illustrates the mechanical method of the RFSS design 300, wherein, the said mechanical method comprises of a spring based setup 310 in which the proposed frequency selective surface in the size of 15mm x 30cm is attached to each arm. A total of 15 such elements are attached to the spring setup. A knob 315 is used to vary the distance between the FSS gap distance K vertically to alter the frequency response.

It is emphasized that the Abstract of the Disclosure is provided to allow a reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein," respectively. Moreover, the terms "first," "second," "third," and so forth, are used merely as labels, and are not intended to impose numerical requirements on their objects.

What has been described above includes examples of the disclosed architecture. It is, of course, not possible to describe every conceivable combination of components and/or methodologies, but one of ordinary skill in the art may recognize that many further combinations and permutations are possible. Accordingly, the novel architecture is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the illustrative examples, make and utilize the present invention and practice the claimed methods. It should be understood that the foregoing discussion and examples merely present a detailed description of certain preferred embodiments. It will be apparent to those of ordinary skill in the art that various modifications and equivalents can be made without departing from the spirit and scope of the invention.

5. Claims:

We claim:

1. A device for a passive reconfigurable frequency selective surface comprising: single side printed unit cell of dimension of 15mm x 15mm on a single substrate; spring based mechanical setup wherein the said setup comprises of an arm wherein the frequency selective surface of size 15mm X 30cm; and a knob to vary the distance between FSS gap distance vertically to alter the frequency response.

2. A device for a passive reconfigurable frequency selective surface as claimed in claim 1, wherein the said unit cell resembles the shape of the shorted square loop with inner square side dimension L is 4.5mm, the gap between the unit cell g is 0.15mm and the width dimension Wl and W3 is 1mm and that of W2 is 3mm 130.

3. A device for a passive reconfigurable frequency selective surface as claimed in claim 15 wherein the said unit cells comprises of identical array each containing 20 elements.

4. A device for a passive reconfigurable frequency selective surface as claimed in claim 1, whereinthe said unit cells comprises of a pair of shorted square loops separated by a uniform distance.

5. A method for a passive reconfigurable frequency selective surface comprising: tuning of frequency response by varying the gap between the rows vertically, whereby the coupling effect changes and affects the frequency response of the FSS; and achieving wide band tuning of 9.6GHz with 20 dB attenuation.

6. A method for a passive reconfigurable frequency selective surface as claimed in claim 5, wherein the varying the row distance is done using a knob.