**Acknowledgements**

overlapping between the two radiation patterns. For MIMO antenna system to ensure the diversity performance as good, the ECC with value below 0.5 is adopted in most the cases. **Figure 15(a)** shows the simulated and measured ECC of the proposed antenna. The simulated ECC is about 0.005 and measured ECC is below

*(a) Simulated and measured ECC, (b) Simulated and measured diversity gain, (c) Simulated and measured*

�

<sup>2</sup> <sup>þ</sup> j j *<sup>S</sup>*<sup>21</sup> <sup>2</sup> � � � �

*DG* ¼ 10

s

ð Þ *S*<sup>11</sup> þ *S*<sup>12</sup>

in **Figure 15(d)**. The group delay is almost uniform and is below 1 ns in the

The simulated and measured diversity gain plots are given in **Figure 15(b)**. The diversity gain of >9.95 dB is found in the UWB band. And, **Figure 15(c)** shows the simulated and measured TARC. It is observed that the TARC of less than �28 dB is obtained in the whole UWB band. The group delay of the proposed antenna is measured in face to face and side by side situations with the space of 30 cm is shown

<sup>11</sup>*S*<sup>12</sup> <sup>þ</sup> *<sup>S</sup>* <sup>∗</sup>

The diversity gain (DG) and total active reflection coefficient (TARC) are also essential parameters to study the MIMO antenna diversity performance. The diversity gain and total active reflection coefficient of the proposed antennas can be

� �

<sup>21</sup>*S*<sup>22</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi <sup>1</sup> � *ECC*<sup>2</sup> <sup>p</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

2

<sup>2</sup> <sup>þ</sup> ð Þ *<sup>S</sup>*<sup>21</sup> <sup>þ</sup> *<sup>S</sup>*<sup>22</sup>

� 2

<sup>2</sup> <sup>þ</sup> j j *<sup>S</sup>*<sup>12</sup> <sup>2</sup> � � � � , (7)

2

(8)

(9)

1 � j j *S*<sup>22</sup>

0.008 from 2.2 to 11.4 GHz.

*TARC, (d) Group delay of the proposed antenna.*

*Innovations in Ultra-WideBand Technologies*

**Figure 15.**

**62**

*ECC* <sup>¼</sup> *<sup>S</sup>* <sup>∗</sup>

1 � j j *S*<sup>11</sup>

estimated by using the equations (8) and (9) [33] as follows:

*TARC* ¼

Authors would like to express their gratitude towards University College of Engineering & Technology, Acharya Nagarjuna University, Guntur and management of Koneru Lakshmaiah Education Foundation, Guntur for their continuous support and encouragement during this work. Further, Dr. J. Chandrasekhar Rao and Dr. N. Venkateswara Rao would like to acknowledge with thanks DST through FIST grant SR/FST/ETI-316/2012, ECR/2016/000569 and Dr. B.T.P. Madhav, Prof. of ECE, KLEF for providing measurement facility in LCRC lab. I would like to thank Mr. P. Ramakoti Reddy, Electro Circuit Systems, Hyderabad, Mr. K. Vijaya Saradhi Reddy, Excel Radio Frequency Technologies, Hyderabad and Mr. Krishna Prasad, Scientist-ECIL, Hyderabad for their help in the fabrication and measurements of the prototype developed in this work.

*Innovations in Ultra-WideBand Technologies*

**References**

[1] Federal Communications

FCC 02-48, Adopted: Feb. 2002;

[2] Kaiser T, Zheng F, Dimitrov E. An overview of ultra-wide-band systems with MIMO. Proceedings of the IEEE.

Released, Apr. 2002.

60(10):4866-74.

2006 Aug 3;42(16):1.

2009 Feb 27;97(2):285-312.

[3] Mabrouk IB, Talbi L, Nedil M, Hettak K. MIMO-UWB channel

[4] Tran VP, Sibille A. Spatial multiplexing in UWB MIMO communications. Electronics letters.

2003 May 7;49(5):1073-96.

15;61(8):4257-64.

[5] Zheng L, Tse DN. Diversity and multiplexing: A fundamental tradeoff in multiple-antenna channels. IEEE Transactions on information theory.

[6] Liu L, Cheung SW, Yuk TI. Compact MIMO antenna for portable devices in UWB applications. IEEE Transactions on antennas and propagation. 2013 May

[7] Zhang S, Ying Z, Xiong J, He S. Ultrawideband MIMO/diversity antennas with a tree-like structure to enhance wideband isolation. IEEE Antennas and Wireless Propagation Letters. 2009 Nov 24;8:1279-82.

[8] Luo CM, Hong JS, Zhong LL. Isolation enhancement of a very compact UWB-MIMO slot antenna with two defected ground structures.

IEEE Antennas and Wireless

1766-9.

**65**

Propagation Letters. 2015 Apr 15;14:

characterization within an underground mine gallery. IEEE Transactions on Antennas and Propagation. 2012 Jul 10;

Commission (FCC), Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems First Rep. and Order, ET Docket 98-153,

*DOI: http://dx.doi.org/10.5772/intechopen.93809*

[9] Tao J, Feng Q. Compact

30;16:792-5.

*UWB-MIMO Antenna with Band-Notched Characteristics for Portable Wireless Systems*

60(3):1596-600.

(17):1-9.

2108-18.

21;15:166-9.

41-9.

ultrawideband MIMO antenna with half-slot structure. IEEE Antennas and wireless Propagation letters. 2016 Aug

[10] Gallo M, Antonino-Daviu E, Ferrando-Bataller M, Bozzetti M, Molina-Garcia-Pardo JM, Juan-Llacer L. A broadband pattern diversity annular slot antenna. IEEE Transactions on Antennas and propagation. 2011 Dec 20;

[11] Rao JC, Rao NV. CPW-fed compact ultra wideband MIMO antenna for portable devices. Indian Journal of Science and Technology. 2016 May;9

[12] Bassi M, Caruso M, Khan MS, Bevilacqua A, Capobianco AD, Neviani A. An integrated microwave imaging radar with planar antennas for

breast cancer detection. IEEE Transactions on microwave theory and techniques. 2013 Feb 26;61(5):

[13] Capobianco AD, Khan MS, Caruso M, Bevilacqua A. 3–18 GHz compact planar antenna for short-range radar imaging. Electronics letters. 2014

[14] Zhang S, Pedersen GF. Mutual coupling reduction for UWB MIMO

[15] Li H, Liu J, Wang Z, Yin YZ.

with enhanced isolation for

neutralization line. IEEE antennas and wireless propagation letters. 2015 May

Compact 1 2 and 2 2 MIMO antennas

ultrawideband application. Progress In Electromagnetics Research. 2017;71:

[16] Kerkhoff A, Ling H. Design of a planar monopole antenna for use with

Jun 27;50(14):1016-8.

antennas with a wideband
