[0001] The present disclosure relates to the field of antennas, and more particularly the present disclosure relates to MIMO antenna.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Wideband antennas include number of features that includes higher data rate transmission, multiple channel transmission, very low consumption of power, and ability to capture and transmit higher resolution of images. Scattering of signal causes multiple path-fading which not only reduces the overall efficiency but also reduces bandwidth. Above said problems are encountered by using Multiple-Input-Multiple-Output (MIMO) technology. However, design of MIMO antenna configuration faces design challenges such as maintaining high isolation between radiating elements. There are techniques that are used to achieve higher isolation between the radiating elements. These techniques involve adding separate isolating structures to the antenna design. This increases complexity and cost of the MIMO antenna design.
[0004] There is, therefore, a requirement to have an improved MIMO antenna with reduced interference between bands and different antenna’s radiating elements without adding any separate isolation structures.

OBJECTS OF THE PRESENT DISCLOSURE
[0005] It is an object of the present disclosure to provide a MIMO antenna with suppressed interference between the operating bands.
[0006] It is an object of the present disclosure to provide a MIMO antenna without any separate isolation structure.

SUMMARY
[0007] The present disclosure relates to the field of antennas, and more particularly the present disclosure relates to MIMO antenna.
[0008] An aspect of the present disclosure relates to a multiple input multiple output (MIMO) antenna. The antenna includes a substrate made of dielectric material and one or more radiating elements configured on a first side of the substrate. The one or more radiating elements are configured with a ground on an opposite second side of the dielectric substrate. The one or more radiating elements are positioned orthogonal to one another.
[0009] In an Aspect, the one or more radiating elements may be configured to operate in one or more bands, and may comprise one or more stop band filters for mitigating interference between one or more bands.
[0010] In an Aspect, the one or more stop band filters may include any or combination of an inverted T-shaped stub and a etched C-shaped slot.
[0011] In an Aspect, the one or more bands may include any or combination of Wireless interoperability for Microwave Access (WiMAX), and Wireless Local Area Network (WLAN).
[0012] In an Aspect, the inverted-T shaped stub may provide blocking of the WiMAX band.
[0013] In an Aspect, the C-shaped slot may eliminate WLAN interfering bands.
[0014] In an Aspect, the one or more radiating elements may be symmetrical in geometry.
[0015] In an Aspect, the substrate may have absolute permittivity value in range of about 2.0-2.3 and may have a value of loss tangent lower than about 0.001.
[0016] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS
[0017] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0018] FIG. 1A illustrates an exemplary inclined plane view of single unit cell fractal antenna, FIG. 1B illustrates an exemplary Front View without Notched Bands of single unit cell fractal antenna, FIG. 1C illustrates an exemplary Front View with Notched Bands of single unit cell fractal antenna, and FIG. 1D illustrates an exemplary side view of single unit cell fractal antenna, in accordance with an embodiment of the present disclosure.
[0019] FIG. 2 illustrates an operating bandwidth of the single unit fractal antenna without interfering bands, in accordance with an embodiment of the present disclosure.
[0020] FIG. 3A illustrates parametric study of notched band sat different values of length of ground ‘Lg’, FIG. 3B illustrates parametric study of notched bands at different values of radius of radiating element ‘R’,FIG. 3C illustrates parametric study of notched bands at different values of WiMAX ‘T3’, and FIG. 3D illustrates parametric study of notched bands at different values of WLAN ‘C3’, in accordance with an embodiment of the present disclosure.
[0021] FIG. 4A illustrates real and imaginary impedance of antenna without notched bands, FIG. 4B illustrates real and imaginary impedance of antenna with filtering bands, FIG. 4C illustrates Surface Current Density distribution at 3.50GHz, and FIG. 4D illustrates Surface current density distribution at 5.50GHz, in accordance with an embodiment of the present disclosure.
[0022] FIG. 5A illustrates time response of single unit cell in terms of group delay, FIG. 5B illustrates time response of single unit cell in terms of Impulse response, in accordance with an embodiment of the present disclosure.
[0023] FIG. 6 illustrates an exemplary 2×2 MIMO antenna configuration, in accordance with an embodiment of the present disclosure.
[0024] FIG. 7A illustrates S-Parameters (S11, S22, S33, S44), FIG. 7B illustrates Surface Current Density Distribution at 3.56GHz, and FIG. 7C illustrates Surface Current Density Distribution at 5.48GHz for 2X2 MIMO antenna, in accordance with an embodiment of the present disclosure.
[0025] FIG. 8A illustrates Envelope Correlation Coefficient of the 2×2 MIMO antenna, FIG. 8B illustrates Directive Gain of the 2×2 MIMO antenna, FIG. 8C illustrates Total Active Reflection Coefficient of the 2×2 MIMO antenna, and FIG. 8D illustrates Channel Capacity Loss of the 2×2 MIMO antenna, in accordance with an embodiment of the present disclosure.
[0026] FIG. 9A illustrates an exemplary 4×4 MIMO antenna configuration in simulated environment, FIG. 9B illustrates Surface Current Density Distribution of 4×4 MIMO antenna at 3.52GHz, FIG. 9C illustrates Surface Current Density Distribution of 4×4 MIMO antenna at SCFD at 5.58GHz, FIG. 9D illustrates Simulated S-Parameters of 4×4 MIMO antenna, and FIG. 9E illustrates Measured S-Parameters of 4×4 MIMO antenna at (D), in accordance with an embodiment of the present disclosure.
[0027] FIG. 10A illustrates Simulated and measured S-Parameters at S21/S31/S41, FIG. 10B illustrates Simulated and measured S-Parameter sat S32/S42/S43,FIG. 10C illustrates Simulated Envelope Correlation Coefficient and Directive Gain, and FIG. 10D illustrates Measured Envelope Correlation Coefficient and Directive Gain, in accordance with an embodiment of the present disclosure.
[0028] FIG. 11A illustrates VSWR comparison (Simulated and Measured), and FIG. 11B illustrates measured gain and radiation efficiency, in accordance with an embodiment of the present disclosure.
[0029] FIG. 12A illustrates two dimensional radiation pattern of proposed antenna at 4.50GHz, FIG. 12B illustrates two dimensional radiation pattern of proposed antenna at 6.85GHz, and FIG. 12C illustrates two dimensional radiation pattern of proposed antenna at 11.0GHz, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0030] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0031] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0032] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0033] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. The invention disclosed may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.
[0034] The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non – claimed element essential to the practice of the invention.
[0035] The present disclosure relates to the field of antennas, and more particularly the present disclosure relates to MIMO antenna.
[0036] In an embodiment of the present disclosure elaborates upon a multiple input multiple output (MIMO) antenna. The antenna includes a substrate made of dielectric material and one or more radiating elements configured on a first side of the substrate. The one or more radiating elements are configured with a ground on an opposite second side of the dielectric substrate. The one or more radiating elements are positioned orthogonal to one another.
[0037] In an embodiment, the one or more radiating elements can be configured to operate in one or more bands, and can comprise one or more stop band filters for mitigating interference between one or more bands.
[0038] In an embodiment, the one or more stop band filters can include any or combination of an inverted T-shaped stub and a etched C-shaped slot.
[0039] In an embodiment, the one or more bands can include any or combination of Wireless interoperability for Microwave Access (WiMAX), and Wireless Local Area Network (WLAN).
[0040] In an embodiment, the inverted-T shaped stub can provide blocking of the WiMAX band.
[0041] In an embodiment, the C-shaped slot can eliminate WLAN interfering bands.
[0042] In an embodiment, the one or more radiating elements can be symmetrical in geometry.
[0043] In an embodiment, the substrate can have absolute permittivity value in range of about 2.0-2.3 and can have a value of loss tangent lower than about 0.001.
[0044] FIG. 1A illustrates an exemplary inclined plane view of single unit cell fractal antenna, FIG. 1B illustrates an exemplary Front View without Notched Bands of single unit cell fractal antenna, FIG. 1C illustrates an exemplary Front View with Notched Bands of single unit cell fractal antenna, and FIG. 1D illustrates an exemplary side view of single unit cell fractal antenna, in accordance with an embodiment of the present disclosure.
[0045] FIG. 2 illustrates an operating bandwidth of the single unit fractal antenna without interfering bands, in accordance with an embodiment of the present disclosure.
[0046] As illustrated, the proposed single unit cell fractal antenna can includes a substrate 102 that can be made of dielectric material and can have absolute permittivity value in a range about 2.0-2.3 and can have a value of loss tangent lower than about 0.001. The substrate 102 can be but not limited to a Rogers RTDuroid5880 having a width ‘Ws’, length ‘Ls’, and height ‘hs’. FIG. 1A illustrates an isometric view of the single unit fractal antenna. The single unit cell fractal antenna can include one or more radiating element 104 (also referred as radiating patch 104, herein) on a first side of the substrate and a rectangular ground 106 at an opposite second side of the substrate 102. The radiating element 104 can include a ground 106 on an opposite second side of the substrate 102. The radiating elements 104 (also referred as one or more radiating elements 104, herein) can be configured to operate in one or more bands, and can be positioned orthogonal to each other. The radiating elements 104 can include one or more stop band filters for mitigating interference between the one or more bands. The one or more stop band filters can include but not limited to an inverted T-shaped stub 110 and an etched C-shaped slot 112. The one or more radiating element 104 can be annular in shape with a plurality of semicircles on the circumference of the radiating element to give it a flower like shape. The FIG. 1B shows side view of the antenna. FIG. 1C and 1D illustrates a front view of the single unit cell fractal antenna.
[0047] A radius of the radiating element can be represented by “R”, a length and width of the rectangular ground 106 can be represented by ‘Lg’ and ‘Wg’, respectively. ‘R’ can be represented by an equation:
R =
F=
Where,
hs= height of the substrate,
fr = operating frequency in GHz
ae = effective radius in mm,
R = patch radius in mm
er = dielectric permittivity of the substrate

ae=a
A radius of the plurality of semicircles can be represented by ‘r’. The radiating element 104 can be connected to 50O micro-strip line and which can be connected to a matched SMA connector 108 for microwave signal input for characterization of antenna in both, near and far-field. The length and width of the micro-strip can be represented as ‘Lm’ and ‘Wm’, respectively.
FIG 1C illustrates insertion of stop band filters to mitigate interference caused by WiMAX and WLAN notched bands. Inverted T-shaped stub 110 provides blocking of WiMAX band while, C-type etched slot 112 on radiating results in eliminating WLAN interfering bands. Table 1 illustrates optimum values of the single unit cell fractal antenna:

Parameter (mm) Parameter (mm) Parameter (mm)
Ws 22.0 Wm 2.00 T2 8.50
Ls 22.0 Lm 5.60 T3 2.50
hs 0.787 Wg 15.0 C1 10.50
R 6.50 Lg 5.00 C2 4.25
r 1.00 T1 4.50 C3 1.75

Table: 1
The single unit cell fractal antenna can provide a working bandwidth of 3.32GHz-12.24GHz as illustrated in FIG .2.
[0048] FIG. 3A illustrates parametric study of notched bands at different values of length of ground ‘Lg’, FIG. 3B illustrates parametric study of notched bands at different values of radius of radiating element ‘R’,FIG. 3C illustrates parametric study of notched bands at different values of WiMAX ‘T3’, and FIG. 3D illustrates parametric study of notched bands at different values of WLAN ‘C3’, in accordance with an embodiment of the present disclosure.
[0049] As illustrated, FIG. 3A illustrates change in impedance bandwidth when length of the ground plane is varied. When, Wg is varied from 4.00mm to 6.00mm, there is improvement in matching of impedance and for Wg=5.00mm, intended impedance bandwidth of 3.20GHz-12.33GHz is achieved. Similarly, when the radius R of the radiating element is changed from 6.00mm to 7.00mm, there is change in upper cut-off frequency. Value of R=6.50mm achieves desirable operating bandwidth of 3.22GHz-13.02GHz with good impedance matching. FIGs 3C-3D illustrates effect of notched band effective length impact on rejected bands, WiMAX and WLAN. For notched bands, effective length of stub/slot is calculated by following equation:
LNotch Band = , and

For WiMAX notched band, variation of T3 from 2.00mm to 3.00mm observes in shifting of bandwidth from 3.45GHz-3.95GHz with maximum voltage standing wave ratio (VSWR) of 48 at 3.64GHz, to 3.27GHz-3.76GHz with maximum voltage standing wave ratio of 42 at 3.43GHz. For optimized value of T3=2.50mm, intended WiMAX notch band of bandwidth 3.34GHz-3.83GHz can be achieved with maximum VSWR of 28 at 3.50GHz. Overall length of T-shaped stub 110 can be calculated as LWiMAX=T1+T2+2T3 mm.
Similarly, for WLAN notched band, variation of C3 from 1.50mm to 2.00mm leads to shifting of bandwidth from 4.93GHz-6.29GHz with maximum voltage standing wave ratio of 26.86 at 5.57GHz, to 5.06GHz-6.51GHz with maximum voltage standing wave ratio of 24.67 at 5.76GHz. For optimized value of C3=1.75mm, required notched band of 5.01GHz-6.44GHz with maximum VSWR of 25.49 at 5.72GHz can be achieved. Also, total length of the etched C-type slot 112 can be calculated as LWLAN=C1+2C2+2C3 mm. It is worth noting that during optimization of WiMAX and WLAN interfering bands, operating bandwidth is not compromised.
[0050] FIG. 4A illustrates real and imaginary impedance of antenna without notched bands, FIG. 4B illustrates real and imaginary impedance of antenna with filtering bands, FIG. 4C illustrates Surface Current Density distribution at 3.50GHz, and FIG. 4D illustrates Surface current density distribution at 5.50GHz, in accordance with an embodiment of the present disclosure.
[0051] As illustrated, FIGs.4A-4B shows impedance graphs for single unit cell antenna without notched bands and with notched bands. For antenna without notched bands, in ideal case, real impedance and imaginary should be 50O and 0O respectively, but for proposed single cell unit fractal antenna, real and imaginary impedance nearly follow the said values. For notched band filters, WiMAX and WLAN, there is mismatch of impedance as observed in FIG. 4B. For WiMAX band, real and imaginary values correspond to (92.23-94j)O, which is very high mismatch condition. Similarly, for WLAN notched band, the values are (2-12j) O which is again a mismatch situation. This mismatch condition for both notched bands ensures reflection of input signal and hence filter characteristics is achieved. FIGs. 4C-4D illustrates surface current density distribution at notched bands centre frequency. For 3.50GHz, maximum surface current density can be observed within inverted T-shaped stub. Also, for 5.50GHz, maximum surface current can be observed around C-shaped slot used to notch WLAN band. Maximum surface current distribution ensures high mismatch of impedance thereby, reflecting all the input signals and resulting in notched band characteristics.
[0052] FIG. 5A illustrates time response of single unit cell in terms of group delay, FIG. 5B illustrates time response of single unit cell in terms of Impulse response, in accordance with an embodiment of the present disclosure.
[0053] As illustrated, FIG. 5A illustrates group delay of proposed antenna that can shows that the variations are less than 0.2ns for bandwidth of 3GHz-9GHz and the variations are less than 0.5ns for remaining operating bands. FIG.5B illustrates impulse response of the proposed antenna in Face-to-Face orientation and Side-to-Side orientation. Gaussian pulse can be applied at the transmitting antenna. In Face-to-Face orientation, larger amplitude signals can be received compared to Side-to-Side orientation as expected.
[0054] FIG. 6 illustrates an exemplary 2×2 MIMO antenna configuration, in accordance with an embodiment of the present disclosure.
[0055] FIG. 7A illustrates S-Parameters (S11, S22, S33, S44), FIG. 7B illustrates Surface Current Density Distribution at 3.56GHz, and FIG. 7C illustrates Surface Current Density Distribution at 5.48GHz for 2X2 MIMO antenna, in accordance with an embodiment of the present disclosure.
[0056] As illustrated, the single unit cell can be converted to 2×2 Multiple-Input-Multiple-Output (MIMO) configuration to increase the efficiency and also to encounter multiple fading effects. Figure 6A illustrates the proposed 2×2 MIMO configuration which can be obtained by placing two identical radiating elements orthogonally and spacing of ?/2 between them. FIG. 7A illustrates plot of S-parameters for reflection and transmission coefficients. It can be seen from the figure that for the radiating elements, parameters (S11/S22) can achieve intended -10dB operational bandwidth while rejecting two interfering bands (WiMAX and WLAN). Also, antenna can observe good isolation of -20dB in pass band which can provide acceptable diversity performance. Figure 7B & 7C illustrates surface current density distribution simulated for 3.56GHz and 5.48GHz, respectively. The simulation is carried out by matching port of antenna B(also referred as Ant. B in FIGs) and providing input to antenna A (also referred ad Ant. A in FIGs). Maximum surface current density distribution can be observed within T-shaped inverted stub and around C-shaped slot. Thus, high mismatch of impedance can be occurred and hence input signals can be reflected back leading to notched band characteristics as observed from S11/S22 graph in the FIG. 7B.
[0057] FIG. 8A illustrates Envelope Correlation Coefficient of the 2×2 MIMO antenna, FIG. 8B illustrates Directive Gain of the 2×2 MIMO antenna, FIG. 8C illustrates Total Active Reflection Coefficient of the 2×2 MIMO antenna, and FIG. 8D illustrates Channel Capacity Loss of the 2×2 MIMO antenna, in accordance with an embodiment of the present disclosure.
[0058] In an embodiment, operation of the proposed 2×2 MIMO antenna configuration is verified by studying diversity performance of the antenna. These results can be obtained on the basis of S-Parameter graph. As illustrated in FIG. 8Aenvelope correlation coefficient can be calculated by means of radiating field pattern and based on S-Parameters. For radiating field pattern, ECC can be given by:

The above equation signifies that radiation pattern of ith port is calculated by matching all the remaining ports to 50OO which can be represented as . For any MIMO system, say S number of radiating elements, than considering any two antenna system with m and n, ECC can be is given by:
(a)
Where, Cm,n(S) is given by:
Cm,n(S)= (b)
From the above equations (a) & (b):

For 2×2 MIMO configuration antenna, from S-Parameter, ECC can be given by:
ECC=
The above equation calculates ECC from S-Parameter. For any uncorrelated MIMO system, ideally ECC should be zero. In non-ideal case, value of ECC should be below 0.2and for the reported MIMO antenna configuration, values are 0.03 as can be seen in the FIG. 8A. FIG.8B illustrated directive gain performance of the proposed 2X2 MIMO antenna. The directive gain can be given by equation:
DG=10
FIG. 8C illustrates the total active reflection coefficient (TARC) performance of the proposed 2X2 MIMO antenna. The total active reflection coefficient can be given by equation:
TARC=
For ideal condition, value of TARC is expected to be less than 0dB and it can be seen in the FIG. 8C that for proposed MIMO configuration, these values are >-20dB in the entire operating band of interest.FIG. 8D illustrated channel capacity loss of the proposed 2X2 MIMO antenna. The channel capacity signifies faithful transmission of information without any distortion. Channel capacity loss (CCL) for 2×2 MIMO can be given by equation:

Where:





It can be seen from the FIG. 8D, the CCL value of the proposed 2X2 MIMO antenna is below 0.4bits/s/Hz, which is permissible value.
[0059] FIG. 9A illustrates an exemplary 4×4 MIMO antenna configuration in simulated environment, FIG. 9B illustrates Surface Current Density Distribution of 4×4 MIMO antenna at 3.52GHz, FIG. 9C illustrates Surface Current Density Distribution of 4×4 MIMO antenna at SCFD at 5.58GHz, FIG. 9D illustrates Simulated S-Parameters of 4×4 MIMO antenna, and FIG. 9E illustrates Measured S-Parameters of 4×4 MIMO antenna at (D), in accordance with an embodiment of the present disclosure.
[0060] As illustrated, the 2×2 MIMO can be converted to 4×4 MIMO configuration by addition of two more identical radiating elements which are placed orthogonal to one another. The proposed 4X4 MIMO antenna occupies compact space with antenna dimension 2Ls×2Ws mm2.Figure 9B & 9C illustrates surface current density distribution at bandwidth of 3.52GHz and 5.58GHz. It can be observed that maximum surface current density is more within inverted T-shaped stub for WiMAX notched band and around C-shaped slot in case of WLAN notched band. Thus, high mismatch of impedance occur leading to non-radiation of input signals. FIG. 9D illustrates S-parameters of proposed antenna with notched bands. It can be observed that required bandwidth with notched bands are achieved by noting S11/S22/S33/S44 S-parameters. FIG. 9E illustrates measured S-parameters (reflection coefficients).
[0061] FIG. 10A illustrates Simulated and measured S-Parameters at S21/S31/S41, FIG. 10B illustrates Simulated and measured S-Parameters at S32/S42/S43,FIG. 10C illustrates Simulated Envelope Correlation Coefficient and Directive Gain, and FIG. 10D illustrates Measured Envelope Correlation Coefficient and Directive Gain, in accordance with an embodiment of the present disclosure.
[0062] As illustrated, FIG. 10C & 10D illustrates diversity performance of the proposed 4X4 MIMO antenna. ECC for 4×4 MIMO configuration can be given by equation:
?e(1,2,4)=
For the proposed antenna, simulated values of ECC are <0.05 and for measured results, the values of ECC are <0.1.
Directive Gain of the proposed antenna can be calculated by equation:
DG=
For any MIMO configuration DG>9.95dB and in proposed antenna, both simulated and measured values are well above 9.95dB except in notched bands as can be seen from FIG. 10D.
[0063] FIG. 11A illustrates VSWR comparison (Simulated and Measured), and FIG. 11B illustrates measured gain and radiation efficiency, in accordance with an embodiment of the present disclosure.
[0064] As illustrated, FIG. 11 compares near and Far-Field results of proposed 4×4 MIMO antenna configuration. Table 2 represents comparison of simulated and measured VSWR comparison for the WiMAX and WLAN bands in FIG. 11A. It can be seen that, simulated results are very close to the measured result. FIG. 11B illustrates a plot of Far-Field result in terms of measured gain and radiation efficiency. Proposed MIMO antenna can maintain average gain of 4.07dB in operating band. There is sharp fall of gain in notched bands as illustrates in FIG. 11B. This steep fall in gain can correspond to -12.78 at 3.59GHz and -14.96 at 5.58GHz, respectively. Similarly, proposed antenna can offer maximum radiation efficiency of 89% and also, there is decrease in efficiency to 28% at 3.69GHz and 23% at 5.59GHz respectively.
WiMAX (GHz) WLAN (GHz) Bandwidth (GHz)
Simulated 3.31-3.98 5.12-6.59 3.02-15.98
Measured 3.36-3.86 5.03-6.46 2.84-15.88
Table: 2
[0065] FIG. 12A illustrates two dimensional radiation pattern of proposed antenna at 4.50GHz,FIG. 12B illustrates two dimensional radiation pattern of proposed antenna at 6.85GHz, and FIG. 12C illustrates two dimensional radiation pattern of proposed antenna at 11.0GHz, in accordance with an embodiment of the present disclosure.
[0066] In an embodiment, the present disclosure pertains to a UWB-Extended bandwidth compact monopole 4×4 MIMO antenna with better isolation <-15dB in operating band of interest. Antenna also offers resistance to WiMAX and WLAN interfering bands by introduction of notched band filters on radiating patch, Also, antenna offers peak average gain of 3.52dBi including maximum radiating efficiency of 89%. Different several diversity metrics including ECC, DG and TARC are calculated which is found to be within permissible limits. The proposed MIMO antenna can be suitable for portable UWB devices/gadget.
[0067] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive patent matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “includes” and “including” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc. The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practised with modification within the spirit and scope of the appended claims.
[0068] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0069] The proposed invention provides a MIMO antenna with suppressed interference between the operating bands.
[0070] The proposed invention provides a MIMO antenna without any separate isolation structure.
[0071] The proposed invention provides an improved MIMO antenna with better isolation and improved performance in operating band of interest.

Claims:1. A multiple input multiple output (MIMO) antenna comprising:
A substrate made of dielectric material; and
one or more radiating elements configured on a first side of the substrate, and the one or more radiating element are configured with, a ground on an opposite second side of the substrate, wherein the one or more radiating elements are positioned orthogonal to one another.
2. The antenna as claimed in claim 1, wherein the one or more radiating elements are configured to operate in one or more bands, and comprise one or more stop band filters for mitigating interference between the one or more bands.
3. The antenna as claimed in claim 2, wherein the one or more stop band filters comprises any or combination of an inverted T-shaped stub and an etched C-shaped slot.
4. The antenna as claimed in claim 1, wherein the one or more bands comprise any or combination of Wireless interoperability for Microwave Access (WiMAX), and Wireless Local Area Network (WLAN).
5. The antenna as claimed in claim 3, wherein the inverted-T shaped stub provides blocking of the WiMAX band.
6. The antenna as claimed in claim 3, wherein the C-shaped slot eliminates WLAN interfering bands.
7. The antenna as claimed in claim 1, wherein the one or more radiating elements are symmetrical in geometry .
8. The antenna as claimed in claim 1, wherein the substrate has absolute permittivity value in range of about 2.0-2.3 and has a value of loss tangent lower than about 0.001.