WO2011159262A1

WO2011159262A1 - Metamaterial based ultra thin microstrip antennas

Info

Publication number: WO2011159262A1
Application number: PCT/TH2010/000019
Authority: WO
Inventors: Nantakan Wongkasem; Boonying Charoen; Chakkrit Kamtongdee
Original assignee: The Office Of National Telecommunications Commission
Priority date: 2010-06-15
Filing date: 2010-06-15
Publication date: 2011-12-22
Also published as: KR101515871B1; JP2013532436A; JP5663087B2; KR20130054315A

Abstract

An antenna structure and a method of producing an antenna structure for wireless communications are disclosed. A radiating element of the antenna exhibits self similar structural properties for reduction in physical size and to improve antenna performance properties such as return loss and gain. To further reduce the energy loss and further increase the gain of the antenna, metamaterial resonating structures are disposed on the same plane as the radiating element of the antenna and on the same surface of a dielectric substrate. By disposing the metamaterial resonating structures on the same plane and on the same surface of the dielectric substrate as the radiating element, thickness of the overall antenna structure is minimized.

Description

METAMATERIAL BASED ULTRA THIN MICROSTRIP ANTENNAS Technical Field

The present disclosure relates generally to antenna designs involving fractal elements and metamaterials. More particularly, aspects of the present disclosure are directed to antenna designs involving a radiating element that exhibits self similar structural features, and a set of metamaterial resonating structures disposed peripheral to the radiating element, where the radiating element and the set of metamaterial resonating structures share a common plane with respect to a planar dielectric substrate.

Background Technological advances in the modern day have escalated the demand for wireless communication. Wireless communication is the transfer of information over varying distances without the need for electrical conductors or wires and this information transfer is carried out by using electromagnetic energy. An antenna is an integral component to facilitate wireless communication in a wireless communication network. Antennas are connected to many wireless devices such as mobile phones, personal digital assistants and portable television sets.

An antenna is used to radiate and/or receive electromagnetic signals in the area of wireless communication. Essentially, an antenna is a transducer that converts electromagnetic waves in the radio frequency of the electromagnetic spectrum into electrical currents. As such, parameters such as antenna gain, directivity and efficiency are taken into consideration when designing antennas. Antennas can operate at a single frequency band or multiple frequency bands. The former is generally known as a single band antenna and the latter is often referred to as a multiband antenna. While multiband antennas are more commonly used today as compared to single band antennas, their size and complex circuitry has resulted in higher costs. Recently, the trend of miniaturizing communication devices and other personal electronic wireless gadgets has correspondingly led to an increasing need for miniaturizing the size of antennas. A microstrip patch antenna, or simply a patch antenna, is a narrowband, wide-beam antenna fabricated by etching an antenna element pattern in a metal patch bonded to an insulating dielectric substrate. A continuous metal layer bonded to the opposite side of the dielectric substrate forms a groundplane. The use of patch antennas has gained popularity which is mainly due to their outstanding physical properties such as light weight, low profile, low production cost, conformability, reproducibility, reliability. A patch antenna also provides ease of fabrication and is easily integrated with solid state devices and wireless technology equipment. A patch antenna can be available in different shapes such as square, rectangular, circular or elliptical. Recently, some drawbacks relating to patch antennas have surfaced. The size of a conventional patch antenna is typically large when designed in the microwave frequency range, and consequently that has an adverse impact when mounting such an antenna on transmitter/receiver and repeater systems. These antennas also have limitations in terms of their narrow bandwidth, low gain, and weak radiating patterns. The gain reduction is a result of the overall reduction in the antenna size and may also be attributed to the substrate characteristics which may lead to surface wave excitation and hence a reduction in gain. Therefore, current research efforts are devoted to designing microstrip antennas to have enhanced radiating properties and at the same time, a smaller size.

Generally, there is an important relationship between antenna dimensions and wavelength such that if the antenna size is less than λ 4 (where λ is the operating wavelength), then the antenna is not efficient because radiation resistance, gain and bandwidth are reduced and therefore antenna size must be increased. One effective method adopted to circumvent the problem of size and radiating properties is to use a fractal radiating patch or a fractal patch antenna. A fractal patch antenna is one that utilizes a fractal or self similar design to maximize the length or increase the perimeter of the material that can receive or transmit electromagnetic signals within a given total surface area or volume. As such, fractal patch antennas can achieve radiation pattern and input impedance that are analogous to a longer antenna, yet overcome the size constraints due to the many contours of their shape. The self similar design is generated by applying an iterative sequence to a starting microstrip structure. However, one shortcoming of these fractal patch antennas arises due to energy loss resulting from the magnetic-electric imbalance. Figure 1 shows an antenna substrate with split ring resonators. To circumvent the problem of reducing the energy loss due to a magnetic-electric imbalance, magnetic resonating structures in the form of split ring resonators have been placed around the perimeter of an antenna substrate. The split ring resonators were placed normal to an antenna patch. This setup is designed according to (most or typical) electric and magnetic field directions. One drawback of such designs is that the thickness of the antenna substrate is increased due to the placement of the split ring resonators.

Summary

In accordance with one aspect of this disclosure, there is disclosed an antenna for transmission and reception of electromagnetic signals at one or more frequency bands. The antenna comprises a dielectric substrate having a first side, a second side opposite the first side, and a third side and a fourth side extending between the first and second sides. The antenna also comprises at least one radiating element disposed on a surface of the dielectric substrate. The at least one radiating element exhibits a set of self similar structural features. The at least one radiating element can include a set of voids. The set of voids of the at least one radiating element can be symmetrically disposed on the at least one radiating element. There is at least one feed line coupled to the at least one radiating element, and the feed line extends between the at least one radiating element and the first side.

Furthermore, there is at least one metamaterial resonating structure disposed on the same said surface of the dielectric substrate as the at least one radiating element, and the at least metamaterial resonating structure is peripheral to the at least one radiating element. The at least one metamaterial resonating structure can be disposed on at least one of the first side, the second side, the third side and the fourth side of the dielectric substrate. For instance, in some embodiments, the at least one metamaterial resonating structure can be disposed on at least one of the dielectric substrate's third side and fourth side. In certain embodiments, the at least one metamaterial resonating structure can comprise a plurality of metamaterial resonating structures vertically disposed or stacked adjacent to each other.

In accordance with another aspect of this disclosure, there is disclosed a method of producing an antenna for transmission and reception of electromagnetic signals at one or more frequency bands. The antenna comprises a dielectric substrate having a first side, a second side opposite the first side, a third side and a fourth side extending between the first and second sides. The antenna also comprises at least one radiating element disposed on a surface of the dielectric substrate. The at least one radiating element exhibits a set of self similar structural features. There is at least one feed line coupled to the at least one radiating element and the feed line extends between the at least one radiating element and the first side. Furthermore, there is at least one metamaterial resonating structure disposed on the same said surface of the dielectric substrate as the at least one radiating element, and the at least one metamaterial resonating structure is peripheral to the at least one radiating element. The method comprises the steps of scaling the at least one radiating element to operate at a desired frequency, determining a direction of an electric field and a magnetic field of the at least one radiating element, wherein the direction of the electric field and the magnetic field is dependent on a shape and a geometry of the at least one radiating element, and determining a set of locations for placement of the at least one metamaterial resonating structure on the dielectric substrate. The set of locations for placement of the at least one metamaterial resonating structure can be on at least one of the first side, the second side, the third side and the fourth side of the dielectric substrate. For instance, in some embodiments, the set of locations for placement of the at least one metamaterial resonating structure can be on at least one of the third side and the fourth side of the dielectric substrate. The method can further comprise at least the step of generating a set of specifications of the antenna and iteratively determining a shape of the at least one radiating element.

The method can further comprise the steps of disposing the at least one radiating element on a surface of the dielectric substrate and disposing the at least one metamaterial resonating structure on a same plane and on the same said surface of the dielectric substrate as the at least one radiating element. Brief description of drawings

Figure 1 shows an antenna substrate with split ring resonators.

Figures 2a and 2b show a top view and side view, respectively, of a schematic diagram of an antenna according to particular embodiments of the disclosure. Figures 3a and 3b show a top view and a side view, respectively of a structure of an antenna according to an embodiment of the disclosure.

Figure 4 is a block diagram illustrating a communication system with a mobile transceiver that comprises an antenna according to an embodiment of the disclosure.

Figures 5a and 5b show the top view and side view of an antenna according to some embodiments of this disclosure.

Figure 6 shows some representative embodiments of antennas in accordance with the disclosure.

Figure 7 shows some other representative embodiments of antennas in accordance with the disclosure. Figure 8 shows a representative embodiment of a metamaterial resonating structure according to some embodiments of the disclosure.

Figure 9 shows a set of split ring resonators (SRRs) with different orientations according to some embodiments of the disclosure.

Figure 10 shows at least one radiating element in accordance with some embodiments of the disclosure.

Figure 11 shows a radiating element having a set of voids according to some embodiments of the disclosure. Figure 12 shows a flow diagram depicting a method of producing the antenna in accordance with representative embodiments of the present disclosure.

Figures 13a and 13b show a simulated electric field and magnetic field, respectively, generated by at least one radiating element according to an embodiment of the disclosure. Detailed description

Embodiments of the present disclosure relate to antennas and/or methods of producing antennas for transmission and reception of electromagnetic signals at one or more frequency bands.

More particularly, this disclosure relates to an antenna structure with at least one radiating element and at least one metamaterial resonating structure disposed on or proximate to the periphery of the radiating element. In various embodiments, a metamaterial resonating structure and the radiating element share a common plane; thus, at least one surface or portion of at least one metamaterial resonating structure resides on the same plane as the radiating element. In some embodiments, the at least one metamaterial resonating structure includes a plurality of metamaterial resonating structures stacked vertically adjacent to each other.

A method of developing such an antenna structure is also disclosed. The antenna structure with at least one metamaterial resonating structure operates with low loss capabilities. By disposing the at least one metamaterial resonating structure on the same plane as the at least one radiating element and peripheral to the at least one radiating element, the energy loss due to magnetic-electric imbalance is minimized while maintaining an antenna structure of minimal thickness.

For the purpose of clarity, the description in this disclosure is directed to antennas operating at wireless frequency ranges of about 2.4 GHz and 5 GHz. However, this does not preclude various embodiments of this disclosure from other applications that require similar operating capabilities as the wireless applications associated with such frequency ranges. It should be appreciated that operating antennas in accordance with the present disclosure at a different frequency band or within a plurality of frequency bands can also be achieved. In the disclosure provided hereinafter and corresponding figures, like elements are identified with like reference numerals.

For the purpose of clarity, Figures 2a and 2b show a top view and side view, respectively, of the schematic diagram of an antenna 100 according to particular embodiments of this disclosure. Figures 2a and 2b facilitate a description of spatial orientations defined with respect to particular embodiments of the disclosure. In such embodiments, the antenna 100 has a dielectric substrate 102 which has a first side 104, a second side 106 which is disposed opposite to the first side 104, and a third side 108 and a fourth side 110 extending between the first side 104 and the second side 106. At least one feed line 112 extends between the first side 104 and at least one radiating element 114. From Figure 2b, the antenna 100 has a top side 116 and a bottom side 118, which is on the opposite side of the top side 116. The radiating element 114 is disposed on the top side 116 and a ground plane layer 120 is disposed on the bottom side 118. For clarity, the surface of the dielectric substrate where the at least one radiating element 114 is disposed on will henceforth be referred to as the top side 116.

Figures 3a and 3b show a top view and a side view, respectively of a structure of an antenna 100 according to an embodiment of this disclosure. The antenna 100 has at least one radiating element 114 disposed on a surface of the a top side 116 of a dielectric substrate 102. The at least one radiating element 114 is configured for the transmission and reception of signals and exhibits a set of self similar structural features 122, as further detailed below. As seen in Figure 3b, the at least one radiating element 114 is elevated above (e.g., extends above or beyond) and parallel to the surface of the top side 116 of the dielectric substrate 102, and the at least one radiating element 114 is electrically coupled to the ground plane layer 120. At least one feed line 112 is connectable to the at least one radiating element 114 for providing powering up and transmitting signals to and from the at least one radiating element 114. The at least one feed line 112 extends between the at least one radiating element 114 and the first side 104. The at least one feed line 112 can be electrically coupled to a connector 124. The at least one radiating element 114 is substantially planar and is formed on a substantially planar dielectric substrate 102. At least one metamaterial resonating structure 126 is disposed on the periphery of and on the same surface of the top side 116 of the dielectric substrate 102 as the at least one radiating element 114. The at least one radiating element 114 and the at least one metamaterial resonating structure 126 share or reside on a same or common plane. As can be understood from Figures 3a and 3b, the at least one metamaterial resonating structure 126 is disposed on the dielectric substrate 102 such that a planar surface of the at least one resonating structure 126 is facing the top side 116 of the dielectric substrate 102. Figure 4 is a block diagram illustrating a communication system 200 with a mobile transceiver 202 that comprises an antenna 100 according to an embodiment of this disclosure. A feed line 112 is coupled to the at least one radiating element 114 for providing the powering up and transmission of signals to and from the radiating element 114. The feed line 112 is electrically coupled to a connector 124. The connector 124 is in turn, coupled to the mobile transceiver 202. A base station 250 has an antenna system 260 for communicating with the antenna 100 by way of the radiating element 114 via a first communication path 300, so that the radiating element 114 can receive a first set of signals 310. A second communication path 320 can also be established such that a second set of signals 330 can be transmitted from the antenna 100 to the base station 250. Due to the interaction of electromagnetic waves during the transmission and reception of signals, gain of the antenna 100 is reduced. The at least one metamaterial resonating structure 126 is disposed on a top side 116 surface of the dielectric substrate 102 and on a same plane as the at least one radiating element 114 to reduce the interaction of the electromagnetic waves. Since a planar surface of the at least one metamaterial resonating structure 126 is disposed on the same said surface of the dielectric substrate 102 as the at least one radiating element 114, the antenna 100 demonstrates a compact structure. The resonant frequency of the metamaterial resonating structure 126 can be designed to operate coincidently with the operating frequency of the antenna 100.

Disposing at least one metamaterial resonating structure 126 on the same plane as the at least one radiating element 114 can result in higher values of permeability and increase gain of the antenna 100. As will be understood by a person skilled in the art, permeability is directly proportional to magnetic energy and disposing the at least one metamaterial resonating structure 126 peripheral to the at least one radiating element 114 will minimize the energy loss of the antenna 100 due to magnetic-electric imbalance. As will be explained later, a manner of disposing the at least one metamaterial resonating structure 126 is dependant on the electric and magnetic field configuration of the at least one radiating element 114. Figures 5a and 5b show a top view and a side view of an antenna 100 according to some embodiments of this disclosure. As shown in Figure 5a, at least one metamaterial resonating structure 126 is disposed peripheral to the at least one radiating element 114 and on the same surface of the dielectric substrate 102 as the radiating element 114. In some embodiments, the at least one metamaterial resonating structure 126 can comprise a plurality of metamaterial resonating structures vertically disposed adjacent to each other to form at least one stack of metamaterial resonating structures 128.

Figure 6 shows some representative embodiments of this disclosure. In some embodiments, there is at least one metamaterial resonating structure 126 disposed on at least one of a first side 104, a second side 106, a third side 108 and a fourth side 110 of the dielectric substrate 102. In some other embodiments, there is at least one metamaterial resonating structure 126 disposed on at least one of the third side 108 and the fourth side 110 of the dielectric substrate 102. In addition to the at least one metamaterial resonating structure 126 on at least one of the third side 108 and the fourth side 110, there can be at least one metamaterial resonating structure 126 on at least one of the first side 104 and the second side 106 of the dielectric substrate 102. The at least one metamaterial resonating structure 126 can be at least one stack of metamaterial resonating structures 128. The at least one metamaterial resonating structure 126 or the at least one stack of metamaterial resonating structures 128 shares a common plane with or is disposed on a same plane as the at least one radiating element 114.

Figure 7 shows some other representative embodiments of this disclosure. As shown in Figure 7, at least one stack of metamaterial resonating structures 128 is disposed on at least one of a first side 104, a second side 106, a third side 108 and a fourth side 110 of a dielectric substrate 102. The at least one stack of metamaterial resonating structures 128 is disposed peripheral to at least one radiating element 114. The at least one stack of metamaterial resonating structures 128 and the at least one radiating element 114 are disposed on a same surface of the dielectric substrate 102. The at least one stack of metamaterial resonating structures 128 shares a common plane with or is disposed on a same plane as the at least one radiating element 114. The quantity of metamaterial resonating structures 126 to be disposed on a dielectric substrate 102 can be determined by an electric and a magnetic field characteristic of the at least one radiating element 114. Placement of the at least one metamaterial resonating structure 126 can be based upon the electric and magnetic field characteristics. The at least one metamaterial resonating structure 126 can be oriented in different directions to provide different magnetic-electric characteristics and the orientations can influence the electromagnetic interactions with the at least one radiating element 114, as further detailed below.

Figure 8 shows a representative embodiment of a metamaterial resonating structure 126 or portions of a metamaterial resonating structure stack 128 according to some embodiments of this disclosure. The at least one metamaterial resonating structure 126 and/or at least one stack of metamaterial resonating structures 128 can be split ring resonators (SRRs). As seen in Figure 8, the metamaterial resonating structure 126 has a plurality of gap bearing sides 134. The resonant frequency of the at least one metamaterial resonating structure 126 or the at least one stack of metamaterial resonating structures 128 can be designed to operate coincidently with the operating frequency of the at least one radiating element 114. In some embodiments of this disclosure, the resonant frequency of the at least one metamaterial resonating structures 126 and/or the at least one stack of metamaterial resonating structures 128 can have a tolerance of ±0.5-5% of the operating frequency of an antenna 100. Split ring resonators can generate a magnetic resonance to cause a large positive peak right before a negative real part of permeability. This high positive value, occurring before its resonance, will stabilize the energy loss resulting from the magnetic electric energy imbalance. These values typically occur at the resonance of the resonating structure.

Figure 9 shows a set of split ring resonators (SRRs) with different orientations according to some embodiments of this disclosure. The directions of excitation wave (k), electric (E) and magnetic (H) fields influence the occurrences of magnetic resonance. Four different orientations of the split ring resonator, categorized by direction of excitation wave k, electric field E, and magnetic field H are shown in Figure 9. Magnetic resonance can be excited through the electromagnetic wave only if the external magnetic field H is normal to a structure plane, as shown in Figures 9a and 9b. For the split ring resonator in Figure 9c, there is no excitation from the magnetic field H, as the magnetic field H is not normal to the structure plane. Therefore, the orientation of Figure 9c may not be suitable to increase the gain of an antenna 100. As the electric field E is parallel to the gap bearing sides 134 of the split ring resonators and the direction of excitation wave k is perpendicular to the split ring resonator plane (Figure 9d), there is an electric resonance occurring at the same resonance. Hence there are three possible ways to arrange the orientations of the split ring resonators (Figures 9a, 9b and 9c) in order to provide the resonance dip.

To avoid undesirably affecting the radiation and permeability of the antenna 100, the at least one metamaterial resonating structure 126 or the at least one stack of metamaterial resonating structures 128 should not be in contact with another metamaterial resonating structure 126 or a stack of metamaterial resonating structures 128 adjacent to it or the at least one radiating element 114. In general, the metamaterial resonating structures 126 or the stack of metamaterial resonating structures 128 which are adjacent to each other should have a gap of at least approximately λ/200, where λ is the operating wavelength of the antenna 100. Preferably, the metamaterial resonating structure 126 or the stack of metamaterial resonating structures 128 should also be spaced approximately λ/200 away from the at least one radiating element 114.

Figure 10 shows the at least one radiating element 114 in accordance with some embodiments of this disclosure. The at least one radiating element 114 is conductive and can be made of copper (Cu), gold (Au) or indium tin oxide (ITO). By way of fractal geometry, the at least one radiating element 114 has a set of self similar structural features 122 resulting from the repetition of a design or motif, where the design or motif is replicated by rotation, translation and/or scaling. In some embodiments, any combination of rotation, translation and scaling can be adopted to achieve the set of self similar structural features 122. To the skilled person in the art, the set of self similar structural features 122 can be known as a plurality of fractal elements 130. The plurality of fractal elements 130 can have at least one feature of a triangular shape, a rectangular shape or a pentagonal shape. The plurality of fractal elements 130 has x-axis and y-axis coordinates for a next iteration N+l defined by XN+i=f(x_N, ybN) and yN+i=g(xN, yN), where X , are coordinates of a preceding iteration, and where f(x,y) and g(x,y) are functions defining the fractal motif and behaviour. Koch pattern, Blackman-koch pattern, lotus pods pattern, Sierpinski pattern, hexagonal pattern and polygonal are self similar patterns that can be adopted for the plurality of fractal elements 130 in this disclosure. As will be understood by a person skilled in the art, the self similar patterns of the fractal elements 130 can be arranged to obtain a desired operating frequency or a range of operating frequencies.

According to some embodiments in this disclosure, the plurality of fractal elements 130 are generated by an iteration factor of 2 or 3 of various shapes such as a triangle, rectangle and pentagon. Preferably, only two iteration numbers, 1^st and 2^nd are adopted in most embodiments of this disclosure. In the area of fractal geometry, the iteration factor and iteration number represent the construction law of fractal generation and how many iterating processes are performed. The resonant frequency of the radiating element 114 decreases as the iteration number and iteration factor increase due to the extension of the average electrical length of the radiating element 114.

The plurality of fractal elements 130 can be configured to provide a dipole response pattern for transmission and/or reception. Alternatively, other antenna designs such as a phased array design can be implemented. These other antenna designs can be implemented independent of the dipole design or in combination with the dipole design. To extend the frequency range of the antenna 100, additional structures in the form of conductors can be included in the antenna 100. These conductors can be conductive traces or wires.

Figure 11 shows a radiating element 114 where a set of voids 132 is created according to some embodiments of this disclosure. This set of voids 132 can be symmetrically disposed on the radiating element 114. The set of voids 132 can be created by using the array concept and this normally improves the radiating properties of the antennas 100. The generated set of voids 132 makes the radiating element 114 behave as if there are two or more radiating elements 114 adjacent to each other.

In accordance with some embodiments of this disclosure, the dielectric substrate 102 can be of any shape including a square, a rectangle or a circle. The permittivity of the dielectric substrate 102 can be in the range of 2 - 40. Preferably, the permittivity of the dielectric substrate 102 is in the range of 2 - 3. Depending on the applications, the size of the dielectric substrate 102 can vary. Many different types of non-conductive materials can be used as the dielectric substrate 102. It can be a silicon wafer, a plastic-like material which can be rigid or flexible, paper, epoxy, glass, fiber glass, ceramic materials and other materials which can impede the flow of electricity. In a preferred embodiment of this disclosure, the dielectric substrate 102 is made of woven fiberglass/PTFE composite materials.

As will be understood by a skilled person in the art, the at least one feed line 112 and the ground plane layer 120 can be of any conducting material such as Cu, Au and ITO. The connector 124 can include a 7/16 DIN connector, a BNC connector, a C connector and a Dezifix connector.

Figure 12 shows a flow diagram depicting a method 400 of producing the antenna 100 in accordance with representative embodiments of the present disclosure. The steps of 402, 404, 406, 408 and 410 according to this method 400, can be performed by way of computer or processing unit execution of program instructions (e.g., software). However, it should be noted that some other ways of performing these steps without the use of software can also be carried out. In a representative embodiment, the software can be CST Microwave studios (Darmstadt, Germany). The method 400 can start with step 402 which is to generate a set of specifications of an antenna 100 to operate at a desired frequency. There are several factors to consider in this step. They include the material and type of a dielectric substrate 102, the material of at least one radiating element 114, operating frequency of the antenna 100 and a set of self similar patterns to adopt for a plurality of fractal elements 130. In some embodiments, a location of at least one feed line 112 is also determined.

After step 402 where the at least one radiating element 114 is designed to operate at a desired frequency, the next step of iteratively determining a shape of the at least one radiating element 404 is performed. The shape of the at least one radiating element 114 is initially set in rectangular shape, analogous to a microstrip antenna, to operate at a desired frequency. Following that, fractal techniques known in this field will be applied. Shapes applied in the fractal technique include a generally triangular shape, a generally rectangular shape and a generally pentagonal shape. The iteration techniques of step 404 can affect the operating frequency of the at least one radiating element 114 due to some misalignments of the radiating element 114 and to rectify this, a scaling of the at least one radiating element 406 is performed to fine tune the at least one radiating element 114 to operate at the desired operating frequency. Following that, in step 408, a direction and strength of an electric field and a magnetic field of the at least one radiating element 114 can be determined. In some embodiments of this disclosure, the direction and strength of the electric field and magnetic field are simulated by software. The direction and strength of the electric field and the magnetic field is dependant on a shape and a geometry of the radiating element 114. During this step, various parameters of the at least one radiating element 114, such as the return loss, VSWR bandwidth and gain can be determined. If the outcome of step 408 satisfies the requirements of the antenna 100, the subsequent step is to determine a set of locations for placement of the at least one metamaterial resonating structure 410. From the simulated electric field and magnetic field of the at least one radiating element 114 obtained from step 408, a set of locations for the placement of the at least one metamaterial resonating structure 410 can be determined.

In some embodiments of this disclosure, the set of locations for placement of the at least one metamaterial resonating structure 126 is on at least one of the first side 104, the second side 106, the third side 108 and the fourth side 110 of the dielectric substrate 102. In some other embodiments of this disclosure, the set of locations is on at least one of the third side 108 and the fourth side 110 of the dielectric substrate 102. The at least one metamaterial resonating structure 126 can comprise of a plurality of metamaterial resonating structures vertically disposed adjacent on each other to form at least a stack of metamaterial resonating structures 128.

Figures 13a and 13b show the simulated electric field and magnetic field, respectively, generated by the at least one radiating element 114 according to an embodiment of this disclosure. As can be seen in Figure 13a, the electric fields, depicted by the arrows, are present on the first side, the second side, the third side and the fourth side of the dielectric substrate 102. As shown, in Figure 13b, the magnetic fields, depicted by arrows, are present near the feed line 112, on the second side, the third side and the fourth side of the dielectric substrate 102. As mentioned previously, there are three orientations in which the split ring resonators can be placed in order to generate the magnetic resonance and obtain the positive peak of permeability. The orientations are shown in Figures 9a, 9b and 9d. The orientations of these three orientations are arranged by the directions of electric field, E, magnetic field, H and excitation wave, k. Based on the simulated electric and magnetic fields shown in Figures 13a and 13b, the set of locations for placement of the at least one metamaterial resonating structure 126 can be determined by focusing on the electric field E and magnetic field H directions.

Preferably, the set of locations for the placement of the at least one metamaterial resonating structure 126 is determined to be at the locations where the electric field and the magnetic field of the at least one radiating element 114 have the highest intensity. The intensities of the electric and magnetic fields can be observed from the simulated data. However, this may not always present the best locations to compensate for the energy loss due to the magnetic- electric imbalance. This can be due to the electric and magnetic couplings between the at least one radiating element 114 and the at least one metamaterial resonating structure 126. It should be evident to the skilled person in the art that the locations where the intensities of the electric field and the magnetic field are the highest can be good starting points to determine the locations for the placement of the at least one metamaterial resonating structure 126. In this step, orientation of the at least one metamaterial resonating structure 126 is also important as this can affect the return loss, VSWR bandwidth and gain of the at least one radiating element 114. Depending on the response of the at least one radiating element 114, based on the return loss, VSWR bandwidth and gain characteristics, the at least one metamaterial resonating structure 126 can comprise a plurality of metamaterial resonating structures. In some embodiments, the plurality of metamaterial resonating structures is vertically disposed adjacent to each other to form at least one stack of metamaterial resonating structures 128. In some embodiments, the plurality of metamaterial resonating structures can each be oriented in the same direction. In some other embodiments, the plurality of metamaterial resonating structures can be oriented in a plurality of directions. In yet some other embodiments, each metamaterial resonating structure within the stack of metamaterial resonating structures 128 can be oriented in a plurality of directions.

Once the set of locations for placement of the at least one metamaterial resonating structure 410 has been determined, the at least one radiating element is disposed on a surface of the dielectric substrate 412. In some embodiments, at least one feed line 112 is also disposed at this stage. Subsequently, the at least one metamaterial resonating structure is disposed on a same plane and on the same said surface of the dielectric substrate as the at least one radiating element 414. According to a representative method, lithography techniques are performed during this stage. As known to a skilled person in the art, the shape of the at least one radiating element 114 and the location and orientation of the at least one metamaterial resonating structure 126 will first be printed onto the dielectric substrate 102 using lithographic techniques. In some embodiments of this disclosure, the dielectric substrate 102 has a conductive coated surface and upon printing, the unwanted conductive surface will be etched away. As discussed, the at least one metamaterial resonating structure 126 to be disposed can comprise a plurality of metamaterial resonating structures and in some embodiments, each of the plurality of metamaterial resonating structures is vertically disposed adjacent to each other to form at least a stack of metamaterial resonating structures 128. Instead of using lithographic techniques, it should be understood that there can be some other ways of fabricating an antenna 100 according to the different embodiments of this disclosure.

In some embodiments of this disclosure, at least one of the steps of generating a set of specifications of an antenna to operate at a desired frequency 402, iteratively determining a shape of a radiating element 404, scaling of the at least one radiating element to operate at a desired frequency 406, determining a direction of an electric field and a magnetic field 408 and determining a set of locations for placement of the at least one metamaterial resonating structure 410 is performed at least once. In some embodiments, depending on the outcome of each step, a step that has been performed can be repeated. For example, after scaling the at least one radiating element to operate at a desired frequency 406, the step of iteratively determining a shape of a radiating element 404 can be repeated. In some other embodiments, all these steps are performed at least once. In yet some other embodiments, the steps of scaling of the at least one radiating element to operate at a desired frequency 406, determining a direction of an electric field and a magnetic field 408 and determining a set of locations for placement of the at least one metamaterial resonating structure 410 is performed at least once.

The method 400 as shown in Figure 12 is merely in accordance with some representative embodiments of this disclosure. It should be understood by a person skilled in the art that the specific order or hierarchy of steps in the foregoing method disclosed is an example of representative approaches. Based on design preferences, it is understood that the specific order or hierarchy of steps in the method may be rearranged without departing from the scope in this disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. For example, the step of scaling the at least one radiating element to operate at a desired frequency 406 can be performed after the step of determining a direction of an electric field and a magnetic field of the at least one radiating element 408. Based on the foregoing disclosure, it should be understood that various changes in the form and design of the antenna can be made without departing from the scope and spirit of this disclosure. The form, method and design described herein are merely an explanatory embodiment thereof and it is the intention of the following claims to encompass and include such changes. In the foregoing manner, an antenna with at least one metamaterial resonating structure and a method of developing an antenna with at least one metamaterial resonating structure which operates with low loss capabilities are disclosed. Although only a number of embodiments are disclosed, it becomes apparent to one skilled in the art in view of this disclosure that numerous changes and/or modification can be made without departing from the scope and spirit of this disclosure.

Claims

1. An antenna for transmission and reception of electromagnetic signals at one or more frequency bands comprising, a dielectric substrate having a first side, a second side opposite the first side, a third side and a fourth side extending between the first and second sides; at least one radiating element disposed on a surface of the dielectric substrate, wherein the at least one radiating element exhibits a set of self similar structural features; at least one feed line coupled to the at least one radiating element, wherein the feed line extends between the at least one radiating element and the first side; and at least one metamaterial resonating structure disposed on the same said surface of the dielectric substrate, wherein the at least one metamaterial resonating structure is peripheral to the at least one radiating element.

2. An antenna according to claim 1 , wherein the at least one metamaterial resonating structure is disposed on at least one of the first side, the second side, the third side and the fourth side of the dielectric substrate.

3. An antenna according to claim 1, wherein the at least one metamaterial resonating structure is disposed on at least one of the third side and the fourth side of the dielectric substrate.

4. An antenna according to claim 1, wherein the at least one metamaterial resonating structure comprises a plurality of metamaterial resonating structures vertically disposed adjacent to each other.

5. An antenna according to claim 4, wherein the plurality of metamaterial resonating structures is disposed on at least one of the first side, the second side, the third side and the fourth side of the dielectric substrate.

6. An antenna according to claim 1, wherein the at least one metamaterial resonating structure is disposed on the same plane as the at least one radiating element.

7. An antenna according to claim 1, wherein the set of self similar structural features of the at least one radiating element includes a plurality of fractal elements.

8. An antenna according to claim 1 wherein the at least one radiating element is

substantially planar.

9. An antenna according to claim 1 wherein the at least one radiating element is

formed on a substantially planar dielectric substrate.

10. An antenna according to claim 7 wherein the plurality of fractal elements

comprises at least one feature having a generally triangular shape, a generally rectangular shape and a generally pentagonal shape.

11. An antenna according to claim 1 wherein the at least one radiating element

comprises at least one of Cu, Au and ITO.

12. An antenna according to claim 7 wherein the plurality of fractal elements include at least one of a koch pattern, a Blackman-koch pattern, a lotus pods pattern, a Sierpinski pattern, a hexagonal pattern and a polygonal pattern.

13. An antenna according to claim 7 wherein the plurality of fractal elements are

generated by an iteration factor of at least 2.

14. An antenna according to claim 1 wherein the at least one radiating element includes a set of voids.

15. An antenna according to claim 14 wherein the set of voids is symmetrically

disposed on the at least one radiating element.

16. An antenna according to claim 1 wherein the at least one metamaterial resonating structure comprises split ring resonators.

An antenna according to claim 1 wherein the resonant frequency of the at least one metamaterial resonating structure has a tolerance of ±0.5-5% of an operating frequency of the antenna.

18. A method of producing an antenna for transmission and reception of

electromagnetic signals at one or more frequency bands, wherein the antenna includes a dielectric substrate having a first side, a second side opposite the first side, a third side and a fourth side extending between the first and second sides; at least one radiating element disposed on a surface of the dielectric substrate, wherein the at least one radiating element exhibits a set of self similar structural features; at least one feed line coupled to the at least one radiating element, wherein the feed line extends between the at least one radiating element and the first side; and at least one metamaterial resonating structure disposed on the same said surface of the dielectric substrate; wherein the at least one metamaterial resonating structure is peripheral to the at least one radiating element, the method comprising the steps of: scaling the at least one radiating element to operate at a desired frequency; determining a direction of an electric field and a magnetic field of the at least one radiating element, wherein the direction of the electric field and the magnetic field is dependent on a shape and a geometry of the at least one radiating element; and determining a set of locations for placement of the at least one metamaterial resonating structure on the dielectric substrate.

The method of producing an antenna according to claim 18, wherein the set of locations for placement of the at least one metamaterial resonating structure is on at least one of the first side, the second side, the third side and the fourth side of the dielectric substrate.

20. The method of producing an antenna according to claim 18, wherein the set of locations for placement of the at least one metamaterial resonating structure is on at least one of the third side and the fourth side of the dielectric substrate.

21. The method of producing an antenna according to claim 18 further comprising at least one of the following steps, generating a set of specifications of the antenna; and iteratively determining a shape of the at least one radiating element.

22. The method of producing an antenna according to claim 21 wherein at least one of the steps of: scaling the at least one radiating element to operate at a desired frequency; determining a direction of an electric field and a magnetic field of the at least one radiating element; determining a set of locations for placement of the at least one metamaterial resonating structure on the dielectric substrate; generating a set of specifications of the antenna; and iteratively determining a shape of the at least one radiating element is performed at least once.

23. The method of producing an antenna according to claim 21 wherein the steps of: scaling the at least one radiating element; determining the direction of an electric field and a magnetic field of the at least one radiating element; determining a set of locations for placement of the at least one metamaterial resonating structure on the dielectric substrate; generating a set of specifications of the antenna; and iteratively determining a shape of the at least one radiating element are performed at least once.

24. The method of producing an antenna according to claim 18 wherein each of the steps of: scaling the at least one radiating element to operate at a desired frequency;

determining the direction of an electric field and a magnetic field of the at least one radiating element; and determining a set of locations for placement of the at least one metamaterial resonating structure on the dielectric substrate are performed at least once.

25. The method of producing an antenna according to claim 18 further comprising, disposing the at least one radiating element on a surface of the dielectric substrate; and disposing the at least one metamaterial resonating structure on a same plane and on the same said surface of the dielectric substrate as the at least one radiating element.

26. The method of producing an antenna according to claim 18 wherein the at least one metamaterial resonating structure comprises of a plurality of metamaterial resonating structures and each metamaterial resonating structure is vertically disposed adjacent to each other.

27. The method of producing an antenna according to claim 18 wherein at least one of the steps is performed by way of computer software.