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A CPW-fed stepped slot UWB antenna for MIMO/diversity applications

Published online by Cambridge University Press:  01 June 2015

Raj Kumar*
Affiliation:
ARDE, Pashan, Pune 411 021, India
Neha Pazare
Affiliation:
DIAT (DU), Girinagar, Pune 411 025, India
*
Corresponding author: R. Kumar Email: raj34_shivani@yahoo.co.in
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Abstract

An ultra-wideband (UWB) slot antenna for diversity applications is introduced. The overall structure of the antenna consists of two similar coplanar waveguide (CPW)-fed stepped rectangular slots placed in an orthogonal position. The slots are asymmetric with respect to their placement in the ground plane. The CPW feeds are double stepped and terminated on hexagonal patches for better impedance matching. A wide impedance bandwidth (measured) from 3 to 12 GHz with an isolation better than 15 dB is obtained with this antenna. To improve the isolation, the design is modified and an I-shaped slot strip is introduced between the two slot antennas. With this, the isolation is brought about 25 dB of most of the band, while the impedance bandwidth remains the same (2.8–12 GHz for port 1, measured and 2.9–12 GHz for port 2, measured). The far-field radiation patterns are also measured and a peak gain of about 5 dBi is obtained. Finally, the diversity parameters such as envelope correlation coefficient and capacity loss are calculated and found to have low values. The antenna is expected to be useful for UWB diversity applications with good isolation.

Information

Type
Research Papers
Copyright
Copyright © Cambridge University Press and the European Microwave Association 2015 
Figure 0

Table 1. Comparison of performance of proposed antenna with references.

Figure 1

Fig. 1. (a) Geometry of antenna 1, (b) geometry of antenna 2, (c) slot details, and (d) isolation stub.

Figure 2

Table 2. Optimized dimension of antenna (mm).

Figure 3

Fig. 2. (a) Photograph of antenna and measured and simulated S-parameters for antenna 1. (b) Photograph of antenna and measured and simulated S-parameters for antenna 2 (proposed). (c) Comparision of simulated and measured S21 of antennas 1 and 2. (d) Comparison of simulated return loss of antenna 1 (single slot, ports 1 and 2).

Figure 4

Fig. 3. Improvement in isolation with different design stages.

Figure 5

Fig. 4. Current distribution for port 1 of antenna 2 at 4.2, 5, 6.5, and 8.2 GHz.

Figure 6

Fig. 5. Simulated results of (a) S11 and (b) S21 for different values of L2.

Figure 7

Fig. 6. Simulated results of (a) S11 and (b) S21 for different values of W2.

Figure 8

Fig. 7. Simulated results of (a) S11 and (b) S21 for different values of H.

Figure 9

Fig. 8. Simulated results of (a) S11 and (b) S21 for different values of L5.

Figure 10

Fig. 9. Simulated results of (a), (c) S11 and (b), (d) S22 for different values of L6 and W6, respectively.

Figure 11

Fig. 10. Simulated results of (a) S11 and (b) S22 for different values of W8.

Figure 12

Fig. 11. (a) Placement of the two port antenna in the co-ordinate system and identification of the E- and H-planes for the two ports. (b) Measured and simulated radiation patterns of port 1. (c) Measured and simulated radiation patterns for port 2.

Figure 13

Fig. 12. Peak gains (a) simulated of both antennas, (b) measured and simulated of antenna 2, port 1, and (c) measured and simulated of antenna 2, port 1.

Figure 14

Fig. 13. Simulated radiation efficiency of antennas 1 and 2 for both the ports.

Figure 15

Fig. 14. Correlation coefficients (a) antenna 1 and (b) antenna 2.

Figure 16

Fig. 15. Correlation coefficients (a) antenna 1 and (b) antenna 2.

Figure 17

Fig. 16. Capacity loss (a) antenna 1 and (b) antenna 2.