1 Introduction

MIMO antenna is extensively utilized in contemporary wireless RF communication system to improve the diversity problem in a single input single output-SISO antenna. The UWB system operates in a wide range of frequency among small spectral power. The signal to noise ratio is also less at the receiver end. That’s why; band-notch is the only opportunity to mitigate the interference from UWB applications through wireless protocols like WiMAX, LTE, and WLAN. The electromagnetic bandgap is used to improve the isolation of the MIMO antenna and co-design approach provides better diversity results [1, 2]. Isolation of MIMO is improved by introducing carbon black film, which can be absorbing the intrusion among antenna elements [3]. Moreover, high isolation is attained by T-shaped slot and stub on the ground plane and dual-polarization (Linear to circular) is achieved by using two perpendicular feeding lines at the patch [4, 5]. In addition, to achieve good isolation performance, T-shaped protuberant ground and Y-shaped quadrate patch are suggested for UWB applications [6]. An extruded T-shaped decoupling structure is introduced in UWB–MIMO antenna to achieve a good diversity performance [7] and orthogonal monopole radiators are also used to attain high isolation without introducing decoupling structure in the ground [8]. Furthermore, by using a T-shaped slot and two-line slots on the ground, high isolation and impedance bandwidth have been achieved [3]. Moreover, inverted L-shaped slits are introduced to produce good diversity performance [9].

By using Monopole antennas, it is achieved UWB operation from 3.1 to 10.6 GHz. In addition, T-shaped slot and stub in the ground are used to minimize the mutual coupling by − 15 dB and two ground-strips are produced an excellent band-notch characteristic for WLAN (5.15–5.85 GHz) to suppress interference [10]. A tapered feed microstrip line with two identical triangular shaped patch radiators and two triangles with J-shaped slit ground are built to get the WLAN notch-band characteristic from 5.10 to 5.85 GHz and INSAT and extended C-band from 6.7 to 7.1 GHz [11]. Henceforth, folded printed monopole antenna is designed to enhance the bandwidth, which is joined with an inverted-L parasitic element and introduced an open-stub to eliminate the WLAN (5.15–5.85 GHz) band [12, 13]. A rectangle shaped stub and split ring resonator (SRR) are providing to attain good isolation and rejection of band simultaneously. Results have shown improved matching of impedance with the required radiation pattern and constant gain also achieved in the operating bandwidth [14]. Moreover, a compact rectangular dielectric resonator (DRA) MIMO antenna with microstrip feed is designed to achieve good bandwidth and inserted two stubs in the ground to get high isolation between antennas [15]. The wireless communication system has various generations (1G–5G), which is supported by SISO to MIMO systems and large bandwidth of the system is one of the foremost factors for high transmission data rate, to enhance the services like triple play i.e. data, audio, and video. Hence, at user end the capacity directly influence the communication system quality. Although MIMO system provides these features in a challenging world to provide high data rate, low channel capacity loss and high signal to noise ratio (SNR) [16] and orthogonal radiating staircase shaped patches with modified co-planer waveguide feed MIMO antenna is designed with 5.5 GHz band-notched characteristics [17]. To provide high isolation and UWB bandwidth with notched band applications, MIMO antennas are presented [18,19,20]. Henceforth, two antennas placed orthogonally to each other and decoupling structure designed in the ground plane to accomplish better isolation between two radiator elements. To improve isolation in MIMO antenna system, two defective complementary open-loop resonators also used to get required results between antennas [21, 22].

In this paper, two-element tapered fed high diversity gain, WLAN notched UWB–MIMO antenna is proposed and it has fabricated on FR-4 substrate with a compact size of 36 × 22 × 1.6 mm3. A band-notch characteristic is obtained through two open-ended stubs on the ground. Furthermore, the diversity characteristic of “mean effective gain” MEGi/MEGj ratio and channel capacity loss (CCL) has also studied. Section 2 presents the proposed antenna design procedure. Section 3 elucidates the proposed antenna results and discussion and Section 4 depicts the diversity performance of the proposed antenna. The achieved results of measurement and simulation are in better concurrence.

2 MIMO Antenna Design Procedure

Numerous wideband applications such as microwave medical imaging, ground penetrating radar (GPR) and RFID tag for inventory control and asset management require a compact and inexpensive UWB–MIMO wireless transceivers. UWB–MIMO base station receiver architecture with different blocks is shown in Fig. 1.

Fig. 1
figure 1

A generic block diagram of two-element UWB–MIMO antenna-based receiver station

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Impulse data is transmitted using UWB–MIMO antenna and after that UWB–MIMO receiver antenna receives the data in a different path and produces the base-band signal, where the information is first encoded, digitally modulated, and then converted into pulse using pulse generator. This UWB–MIMO antenna has shown in Fig. 2a and b with WLAN notch is fabricated on FR-4 substrate of height (h) 1.6 mm with relative permittivity (εr) of 4.4, loss tangent (tanδ) of 0.02 by the dimension of 36 mm × 22 mm. The antenna is designed by a circular with triangular notched patches and to enhance the isolation between two radiated patches, a T–I shaped slot in the ground is groomed, which improves the isolation better than − 30 dB in wished-for UWB bandwidth. The resonant frequency of circular patch for TM11 mode is 7.15 GHz which is used to calculate the patch radius to achieve desired bandwidth (3.1–11.2 GHz).

Fig. 2
figure 2

Two-element UWB planar monopole MIMO antenna a front view, b bottom view

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UWB bandwidth in MIMO antenna including notch band characteristic is achieved by using a tapered feed line together with the partial tailored ground plane. The fundamental resonance frequency of the monopole antenna is prearranged by Eq. (1).

$${\text{f}}_{\text{r}} = \frac{144}{{{\text{l}}_{1} + {\text{d}}_{1} + {\text{h}} + \frac{{{\text{A}}_{1} }}{{2\uppi\sqrt { \in_{\text{r}} + 1} }} + \frac{{{\text{A}}_{2} }}{{2\uppi\sqrt { \in_{\text{r}} + 1} }}}}$$
(1)

where A1, A2 is the area of anticipated radiation patches and ground plane, l1, length of the ground plane, d1, diameter of circular radiated patches. Step by step procedure of the proposed UWB-MIMO antenna design is ushered in Fig. 3 and corresponding return loss and isolation are presented in Fig. 4a and b respectively. Antenna-1 provides unsatisfactory return loss and isolation in intentional UWB range. By changing the feeding line width of antenna-1, return loss and isolation is improved as depicted in antenna-2.

Fig. 3
figure 3

Geometrical design steps of a designed antenna with WLAN band-notch characteristic

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Fig. 4
figure 4

Simulated (using CST MWS) results of a return loss, b isolation of the antennas shown in Fig. 3

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In antenna-3, a triangular shape etched from patches which improve isolation as well as return loss. Hence, an antenna-4, impart vertical stubs on the ground plane to get better return loss from 3.1 to 4.8 GHz and it also provides a notch band characteristics for WLAN (5.1–5.9 GHz) although poor isolation in the intended lower frequency region. Therefore, to improve isolation in entire UWB bandwidth, fixed another T and I shaped slot in ground, the same as shown in antenna-5.

The notched band can be achieved by varying the ground stubs length (Ls) at the notch frequency, \({\text{f}}_{\text{n}} = {\text{c}}/\left( {2 \times {\text{L}}_{\text{s}} \times \sqrt {\upvarepsilon_{{{\text{reff}}}} } } \right)\), where c is the speed of the signal in a vacuum (3 × 108 m/s), εreff is the effective relative permittivity [23] of the substrate and approximated length of Ls is 6.3 mm at notched frequency.

Frequency selectivity of the rejection band is an important parameter to design a UWB antenna with notch band. For selectivity of the notched band of the UWB–MIMO antenna, another ubiquitous parameter is ‘Roll off rate’ i.e. control required a bandwidth of the WLAN band. Furthermore, RoC-Roll off criteria is the ratio of the bandwidth at − 5 dB and − 10 dB, i.e. RoC = BW− 5 dB/BW− 10 dB and the RoC of proposed antenna is 0.44, which is acceptable for practical design. The bandwidth of notched band is also controlled by the length of stubs (Ls) in ground plane and the results of return loss, centered at 5.6 GHz as made known in Fig. 5. By varying Ls from 5.8 to 6.8 mm, return loss curve shifts from higher to lower frequency and value of return loss at the intended notch (6.3 mm) is − 2.0 dB. Impedance bandwidth is also maintained significantly, in the entire bandwidth throughout optimization of Ls.

Fig. 5
figure 5

Simulated results of return loss and Isolation of antenna with a variation of length of stubs (Ls) in the ground plane

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It is hardnosed from Fig. 6a, where strong current accumulates around vertical stubs in the ground plane, which produces a notched for WLAN band in UWB bandwidth to mitigate interference. Figure 6b shows the distribution of current on the antenna at various frequencies like 4.1, 6.6 and 9.6 GHz respectively. It is too observed that the flows of current on the tapered feed line to circular element while a small current pours across the second element of MIMO. The slot in ground plane works as an isolator between the two elements and this is preventing the coupling of the electromagnetic energy.

Fig. 6
figure 6

Surface current distributions at a notch band frequency i.e. 5.6 GHz and b 4.1, 6.6 and 9.6 GHz when port-2 terminated with 50 Ω impedance and port-1 is excited

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3 Results and Discussion

The scattering parameter results (measured and simulated) are shown in Fig. 7. Eventually, measured S12 shows better isolation than the simulation results and isolation between two antenna radiators is < −30 dB for the entire UWB bandwidth. Results illustrate that the return loss of proposed MIMO antenna is ≤ − 10 dB except for notched band (WLAN) and bandwidth of the antenna is 8.1 GHz (from 3.1 to 11.2 GHz), that fulfills the FCC requirement for UWB applications without interference.

Fig. 7
figure 7

Simulated and measured a S-parameter (Return and Isolation) b peak gain, radiation efficiency and total radiation efficiency of UWB–MIMO antenna

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Maximum peak gain of antenna has revealed the better conformity between simulated and measured results and the maximum value of gain is 4.85 dB. The radiation efficiency of antenna throughout the requisite band is higher than the permissible limit except for the notched band, is centered at 5.6 GHz. Consequently, proposed MIMO can appropriate to work in the high interference surrounding as presented in Fig. 7b.

Figure 8a–c shows the 3D radiation pattern of proposed MIMO antenna at 4.1, 6.6 and 9.6 GHz frequency correspondingly, when port-1 is excited and port-2 is terminated with 50 Ω or vice versa. Radiation patterns are slightly directional because power radiated towards the left of the yz-plane when port-1 is excited and when port-2 of MIMO antenna is excited, the power is radiating towards the right of the yz-plane to achieved pattern diversity performance of an antenna. Co-polarization is the power level of an electromagnetic wave in an intended direction on the other hand cross-polarization is the power level of an electromagnetic wave in an un-intended direction due to interference at reception or transmission antenna. Co-polarization and Cross-polarization at different frequencies are calculated by the simulator (CST-Microwave studio) and validate these results by Vector Network Analyzer so we use two terms simulated, by CST-Microwave studio and measured by VNA. The prototype of proposed MIMO antenna on FR-4 substrate is fabricated by conventional printed circuit board design procedure and antenna under test in an anechoic chamber associated with VNA for measurement of radiation characteristics as shown in Fig. 8d and e.

Fig. 8
figure 8

The 3D radiation pattern of MIMO antenna at a 4.1 GHz, b 6.6 GHz, c 9.6 GHz only port-1 is excited and port-2 terminated by 50 Ω load, d fabricated prototype, e antenna under test in an anechoic chamber for radiation pattern measurement

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Figure 9 shows the simulated/measured yz-plane (left) and xz-plane (right) radiation pattern of antenna at three different frequencies as 4.1, 6.5 and 9.6 GHz respectively with an acceptable agreement. Whereas the UWB–MIMO antenna consists of two indistinguishable radiated antenna elements and so the time of measurement of the 2D radiation pattern, port-1 is excited and port-2 is terminated by the 50 Ω load. It is observed that at operating frequency band the radiation patterns are omnidirectional in H (xz)-plane and dipole like in E (yz)-plane except for WLAN band. The splitting of the radiation lobes is also observed due to higher-order mode propagation at higher frequencies.

Fig. 9
figure 9

Measured and simulated 2D radiation pattern at 4.1, 6.6 and 9.6 GHz for yz-plane (left) and xz-plane (right)

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Specific absorption rate: SAR is a vital parameter in the antenna at which the human body is absorbed electromagnetic field energy when exposed, means the power absorbed per mass of body/head tissue as shown Fig. 10. It is typically averaged either over a small sample volume (typically 1 g or 10 g of tissue) or over the entire body. The SAR value of any RF and microwave electronic devices is obtained by penetration of electric field intensity in the human head tissue at near field environment [24, 25]. Furthermore, SAR estimation on the head at 4.1, 6.6 and 9.6 GHz frequency, the skin radius, bone radius, and brain radius are 79.324 mm, 75 mm and 65 mm respectively are used and other parameters are also listed in Table 1. The calculated value of SAR is less than 1.6 W/kg for the proposed antenna design as shown in Table 2 but this SAR performance investigates without any plastic jacket or cover, thus when we wrap proposed antenna into a plastic jacket or cover then SAR performance may be increased more. SAR for electromagnet energy is calculated by Eq. (2).

$${\text{SAR}} = \frac{1}{\text{V}}\int {\frac{{\upsigma({\text{r}})\left| {{\text{E}}({\text{r}})} \right|^{2} }}{{\uprho({\text{r}})}}} {\text{dr}}$$
(2)

where σ = thermal conductivity of sample in S/m, Erms = electric field in V/m, ρ = sample density in kg/m3, V = volume of the sample in m3.

Fig. 10
figure 10

Calculation of specific absorption rate near the human head in presence of the proposed MIMO antenna

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Table 1 Parameters of the human head for calculation of specific absorption rate (SAR) by the proposed antenna at constant permeability (i.e. 1)
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Table 2 SAR values near the human head at different resonant frequencies when the distance between the human head and MIMO antenna is 13 mm
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4 MIMO Diversity Performance

MIMO diversity performance of the proposed antenna is evaluated in terms of Envelope Correlation Coefficient, Total Active Reflection Co-efficient, Diversity Gain, Multiplexing Efficiency and Channel Capacity Loss. The mutual coupling between two radiation patches and the amount of correlation between them is examined by ECC. It is calculated through using S-parameters by following Eq. (3a) and this equation is valid for measuring of ECC when the antenna is lossless and radiated power is uniformly distributed along with the antennas.

$$\hbox{ECC} = \frac{{\left| {\hbox{S}_{11}^{*} \hbox{S}_{12} + \hbox{S}_{21}^{*} \hbox{S}_{22} } \right|^{2} }}{{\left( {1 - \left| {\hbox{S}_{11} } \right|^{2} - \left| {\hbox{S}_{21} } \right|^{2} } \right) \times \left( {1 - \left| {\hbox{S}_{22} } \right|^{2} - \left| {\hbox{S}_{12} } \right|^{2} } \right)}}$$
(3a)

But lossless is a hypothetical result which varies from empirical result so, the computation the ECC of the MIMO antenna by Eq. (3b) in terms of radiated fields

$$\hbox{ECC} = \frac{{\left| {\iint\limits_{4\pi } {\left[ {\hbox{E}_{{\rm i}} \left( {\theta ,\phi } \right) \times \hbox{E}_{{\rm j}} \left( {\theta ,\phi } \right)} \right]\hbox{d}\Omega }} \right|^{2} }}{{\iint\limits_{4\pi } {\left| {\hbox{E}_{{\rm i}} \left( {\theta ,\phi } \right)} \right|^{2} \hbox{d}\Omega \times \iint\limits_{4\pi } {\left| {\hbox{E}_{{\rm j}} \left( {\theta ,\phi } \right)} \right|^{2} \hbox{d}\Omega }}}}$$
(3b)

where Ei and Ej are the radiated electric fields vector of the ith and jth elements of the MIMO antenna system and Ω denotes beam area.

The ideal value of ECC is zero for uncorrelated MIMO antenna but their acceptable value for practical MIMO antenna is ≤ 0.5 and as per Fig. 11a the value of ECC of designed MIMO antenna is less than 0.01 in UWB bandwidth excluding notched band. Hence, the above result specifies pretty low correlation between the two antenna ports, which shows the excellent diversity performance. The diversity gain can be calculated by \({\text{DG}} = 10 \times \sqrt {\left( {1 - {\text{ECC}}^{2} } \right)}\) and for satisfactory operation of MIMO antenna diversity gain should be closed to 10 dB and the value of diversity gain of UWB-MIMO antenna is 9.95 dB apart from the notched band as depicted in Fig. 11a.

Fig. 11
figure 11

Simulated and measured results of the proposed antenna a envelope correlation coefficient and diversity gain, b simulated result of multiplexing efficiency

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In addition, to optimize the antenna channel capacity, the multiplexing efficiency is a maneuver parameter which is not only explored the total antenna efficiency, but also the co-relation and efficiency disparity. In addition, multiplexing efficiency (ηMUX) is the ratio of the power requirement of an antenna to the reference antenna. Figure 11b shows the multiplexing efficiency of the MIMO antenna and ηMUX is calculated by \(\upeta_{\text{MUX}} = \sqrt {\left( {1 - \left| {\uprho_{\text{c}} } \right|^{2} } \right)\upeta_{1}\upeta_{2} }\), where ρc is a complex correlation between two side by side antenna i.e. ECC = ρ2c and η1, η2 is the antenna total efficiency of MIMO antenna elements. The result shows that the total efficiency (shown in Fig. 7b) and multiplexing efficiency are almost identical and its value goes downward at notched WLAN band.

The two-port antenna system, contiguous antenna elements impinge on each other and when working concurrently they influence the overall desirable gain, efficiency, and bandwidth. Actual MIMO antenna system performance will not be predicted by S-parameters only, therefore TARC has initiated this effect into account. It is the square root of the ratio of total reflected to total incident power and hence, it gives the information about the apparent return loss of the MIMO antenna system. For side by side two port radiated antenna system, it can be evaluated by Eq. (4).

$$\hbox{TARC} = \sqrt {\frac{{\left( {\hbox{S}_{11} + \hbox{S}_{12} } \right)^{2} + \left( {\hbox{S}_{22} + \hbox{S}_{21} } \right)^{2} }}{2}}$$
(4)

Ideally, the value of TARC should be less than 0 dB for MIMO antenna based system. Figure 12a shows the simulated and measured TARC of the proposed MIMO antenna and it is observed that the value of TARC is less than − 28 dB and − 40 dB correspondingly in the entire UWB range except for the notched band, it shows the excellent diversity performance of the designed antenna. With increasing the number of elements, the channel capacity of MIMO system is linearly increased, so the element matrix properly characterizes the performance of a MIMO system as it provides the information about the phase and gain characteristics of the transmitting and receiving elements. However, in the presence of the correlation factor in MIMO antennas, the channel capacity losses are also increased. Therefore, diversity performance of proposed antenna pretentious and channel capacity losses are calculated by the following Eq. (5)

$$\hbox{CCL(dB)} = - \log_{2} \left[ {\det \left( {\phi^{{\rm R}} } \right)} \right]$$
(5)

where φR is the 2 × 2 co-relation matrix in terms of S-parameter \({\upvarphi }_{\text{ii}} = 1 - \left| {{\text{S}}_{\text{ii}} } \right|^{2} - \left| {{\text{S}}_{\text{ij}} } \right|^{2} ,\;{\upvarphi }_{\text{ij}} = - \left( {{\text{S}}_{\text{ii}} \times {\text{S}}_{\text{ij}} + {\text{S}}_{\text{ji}} \times {\text{S}}_{\text{jj}} } \right)\). Figure 12a shows the CCL losses and it is less than 0.35 bits/s/Hz over the entire bandwidth except for notch band, which offer a better diversity results of the proposed MIMO antenna. Moreover, the mean effective gain (MEG) is the ratio of the mean received power by the ith antenna to the mean incident power of the jth antenna with the same route, MEGi = εTotal/2, where  εTotal is implying total effective efficiency of the ith antenna, i.e.\({\varepsilon}_{\text{Total}}^{\text{i}} = {\varepsilon}_{\text{mis}}^{\text{i}} \times {\varepsilon}_{\text{rad}}^{\text{i}} ,\) and where \({\varepsilon}_{\text{mis}}^{\text{i}} = 1 - \sum\nolimits_{{{\text{j}} = 1}}^{\text{N}} {\left| {{\text{S}}_{\text{ij}} } \right|^{2} } ,{\varepsilon{E}}_{\text{rad}}^{\text{i}} = \sum\nolimits_{{{\text{j}} = 1}}^{\text{N}} {\left| {{\text{S}}_{\text{ij}} } \right|^{2} }\) where \({\varepsilon}_{\text{mis}}^{\text{i}}\), and \({\varepsilon}_{\text{rad}}^{\text{i}}\) are mismatch efficiency and radiation efficiency of ith antenna as shown in Fig. 12b. MEG ratio for the proposed MIMO antenna is to be extracted by Eq. (6)

$$\hbox{MEG}_{{\rm i}} = \frac{{\hbox{P}_{{\rm rec}} }}{{\hbox{P}_{{\rm inc}} }} = \oint {\left[ {\frac{{\hbox{XPR} \times \hbox{G}_{\theta i} \left( \Omega \right) + \hbox{G}_{\phi {\rm i}} \left( \Omega \right) \times \hbox{P}_{\phi } \left( \Omega \right)}}{1 + \hbox{XPR}}} \right]\hbox{d}\Omega }$$
(6)

where, XPR is the cross-polarization ratio, Gθi (Ω), GΦi (Ω) and PΦ(Ω) is the gain and power density function of the incident wave, Ω = beam area.

Fig. 12
figure 12

Simulated and measured results of a channel capacity loss (CCL) and total active reflection coefficient (TARC), b simulated results of the mean effective gain (MEG) and group delay of proposed MIMO antenna

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The acceptable ratio of mean effective gain of ith and jth antenna elements should be less than or equal to ± 3 dB and as from Fig. 12b, the MEG ratio of the projected MIMO antenna found in acceptable limit throughout the UWB range, which is a high-quality channel performance for wireless communication. Finally, to verify the time domain analysis of the intended MIMO antenna, two identical antennas have located in front of each other as a receiver and transmitter at a distance of 100 cm and group delay (ns) is calculated. Group delay is the rate of change of transmission phase angle with respect to frequency and it is almost constant in entire the intended band. Group delay in terms of return loss (S11) is defined by equation \({\text{T}}_{\text{d}} \left(\upomega \right) = -\updelta \upphi /\updelta \upomega\), where Φ = phase of S11 and ω = angular frequency in rad/s. The group delay deviation of proposed MIMO antenna is ≤ 0.3 ns entire the UWB frequency span excluding notched band as shown in Fig. 12b.

The MEG is also represented in isotropic and Gaussian mediums, to investigate the diversity performance at XPR = 0 dB (outdoor) and 6 dB (indoor) as shown in Fig. 13a and Table 3 of the proposed antenna. The MEG for the isotropic medium at 0 dB and 6 dB XPR is constant at − 3.0 dB and lies between − 3.1 and − 5.1 dB respectively. Similarly, the MEG for Gaussian medium at 0 dB and 6 dB XPR is lying between − 2.7 and − 4.2 dB, and − 4.6 to − 6.5 dB respectively for entire UWB bandwidth.

Fig. 13
figure 13

a A simulated mean effective gain in Isotropic and Gaussian medium at various XPR values of proposed antenna applications, b power associated with proposed MIMO antenna for various diversity performances

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Table 3 Simulated MEG results of proposed MIMO antenna at various frequencies
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The power loss, power accepted, power outgoing, power radiated, and power stimulated of the proposed antenna is used to calculate the parameters like SAR, CCL, ECC, DG and radiation efficiency as shown in Fig. 13b. 0.5 W stimulated power is used to calculate all MIMO antenna parameters. Stimulated power, accepted power, and power radiated is having the same nature with different values due to various losses like a dielectric, conductor, surface wave, and port losses. Therefore, stimulating power is always greater than accepted and radiated power. Power going to all ports is highly interfere at the notched band (5.1–5.85 GHz) so that the maximum power is correlated between ports and not used for radiation.

An evaluation of the proposed MIMO antenna with existing referred MIMO antennas is represented in Table 4. It is observed that the designed antenna achieves the better results in comparison with the most of the MIMO antennas at various specifications, which is highly appreciable as small in size, low in cost, improved radiation efficiency (0.75–0.97) with enhanced isolation, better ECC and diversity gain (> 9.95 dB).

Table 4 Comparison of proposed UWB-MIMO antenna including WLAN notched band with existing references at various aspects
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5 Conclusion

A MIMO antenna has been designed for UWB bandwidth (3.1–11.2 GHz) with better isolation (≤ − 30 dB), radiation efficiency (> 0.75), and sharp rejection at WLAN (5.1–5.85 GHz) band. Diversity performance of antenna has also been verified in terms of ECC (≤ 0.008), TARC (≤ − 25 dB), CCL (≤ 0.3 bits/s/Hz), Mean effective gain ratio (MEGi) ≅ 1 and Directive Gain (≥ 9.95 dB). Apart from the above-mentioned antenna performance, the SAR value of antenna, when it is used in human interface devices is less than the permissible limit as mentioned in Table 2, hence the antenna prototype is appropriate for UWB bandwidth at high interference surroundings in indoor or outdoor applications.