Improved performance of Microstrip Antenna Arrays through Electromagnetic

Coupling(EMCP) at Ka-band

Pratigya Mathur and Girish Kumar

Antenna Lab, Electrical Engineering Department,

IIT Bombay, India

pratigya.mathur@gmail.com, pmathur@iitb.ac.in

gkumar@ee.iitb.ac.in

Forum for Electromagnetic Research Methods and Application Technologies

(FERMAT)

Copyright

The use of this work is restricted solely foracademic purposes. The author of this work ownsthe copyright and no reproduction in any form ispermitted without written permission by theauthor.

Indian Institute Of Technology Bombay, India 2

Abstract

Corporate fed Microstrip Antenna Array (MSAA) and Electromagnetically

Coupled Microstrip Antenna Array (EMCP-MSAA) : A comparison

Based on the analysis of different microstriplines of varying line widths, a

low loss feed network is proposed.

Gain improvement of 25% (1.5 dB) is achieved using the proposed feed

network in 2×2 EMCP-MSAA.

8×8 MSAA - designed and fabricated at Ka-band. Measured Bandwidth:

4.3% and Gain: 24dB.

Bandwidth enhancement done by designing and fabricating EMCP-MSAA.

Bandwidth:17% for 8×8 array.

Keywords: Antenna array, Bandwidth, Electromagnetically Coupled (EMCP), High Gain, Microstrip.

Indian Institute Of Technology Bombay, India 3

Biography

Girish Kumar is a professor at Indian Institute of Technology

Bombay and has 30 years of experience in designing

antennas and microwave circuits. He has published more

than 290 papers in the national and international journals and

conference proceedings. He has written two books and filed

for 6 patents.

Pratigya Mathur is currently pursuing Ph.D. at Indian

Institute of Technology Bombay. Her research interests are

RF, Microwaves, Microstrip Antennas and Arrays. She has

been working on various project in collaboration with Indian

Space Research Organization (ISRO) and Defence

Research and Development Organisation (DRDO).

Indian Institute Of Technology Bombay, India 4

Presentation Outlines

Introduction

Analysis of Single Patch and Electromagnetically Coupled (EMCP) Antennas

Design of Corporate feed Microstrip Antenna Array at Ka-band and its Measured Results

Design of Low-Loss Feed Network

Design of Broadband EMCP Antenna Array and its Measured Results

Conclusions

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Introduction

• Millimeter-Waves Applications are of increasing interestbecause of the wide bandwidth available and small size.

• Wide bandwidth supports high speed data transmissionand video distribution.

• High gain antennas are required to overcomeatmospheric attenuation due to absorption of microwaveenergy by water vapors or molecular oxygen in longrange communication systems.

• High gain Microstrip Antenna Array and BroadbandEMCP antenna arrays have been designed.

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Analysis of Single Patch and EMCP Antennas

Substrate para: εr=2.2, h=0.254mm, tan δ = 0.001

Patch antenna with its Top and Side view

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Patch

Substrate

GND

SMA Connector

2.64mm

2.8

mm

Patch1Substrate

SMA Connector2h+

0.5

mm

Patch2

2.26mm

2.59mm

3.2

mm

EMCP antenna with its Top and Side view

0.4mm0.9 mm

Edge impedance for single patch at 35.5GHz is approximately 200 Ω and for EMCP

patch is nearly 50 Ω.

Analysis of Single Patch and EMCP Antennas

EMCP Antenna gives larger bandwidth from 33-42GHz (24%) and Patch

antenna gives bandwidth from 34.3-36GHz (2.4%)

EMCP Antenna gives larger gain of 8.8dB over its bandwidth and Patch

antenna gives gain of 7dB

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Design of Microstrip Antenna Array

Microstrip lines of 0.44mm (70.7 Ω)

and 0.22mm (100 Ω ) are used. W2,

W3, W4 and W6 are 0.44mm (70.7 Ω).

W5 and W7 are 0.22mm (100 Ω).

• Substrate para: εr=2.2, h=0.254mm, tan δ = 0.001

• Patch length 2.6mm and width 2.8mm

• Distance between the patches is taken as 5.8mm (0.697λo)

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Patch & feed network

SubstrateGND

SMA Connector

Results of Microstrip Antenna Array

Array SizeFreq

(GHz)

Gain

(dB)

Bandwidth

(GHz)

2×2 35.7 12.7 35.3-36.2(2.5%)

4×4 35.3 18.4 34.8-35.8(2.8%)

8×8 35.75 24.2 34.8-35.8(2.8%)

As the size of the antenna array increases, gain increases and bandwidth also increases.

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Measured Results of 8x8 MSA Array

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5cm5cm

Fabricated 8×8 MSAA Measured bandwidth (S11<-10dB) :

33.6-35.3GHz (4.3%)

SLL better than -13dB

Atenuation vs Frequency of ….

Indian Institute Of Technology Bombay, India 12

Gain of the antenna is

improved by using low loss

feed lines at Ka-band

50 Ω line becomes more lossy

at Ka-band than a frequency

below 10GHz

Order of losses at higher

frequency:

50 Ω > 70.7 Ω > 100Ω

Width of the lines of feed

network must be chosen

depending upon frequency of

operation to reduce losses to

improve the antenna gain.

Design of Low Loss Feed Network for MSAA

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Low Loss

Feed

Network

Gain improvement of >1.5 dB using the low loss network in 2×2 EMCP-MSAA

Design of EMCP Antenna Array

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Array SizeGain

(dB)

Bandwidth

(GHz)

2×2 13.6 32.3-40 (19.9%)

4×4 18.7 32.9-39.3(17.7%)

8×8 24.2 33.6-39.4(15.8%)

.

• Bandwidth of the antenna increases

due to electromagnetic coupling of

the patches

• As the size of the antenna array

increases, gain increases but

bandwidth decreases slightly

Results of 8x8 EMCP Antenna Array

Indian Institute Of Technology Bombay, India 15

6.5cm

Measured BW: 32-38GHz (17%)

SLL better than -13dB

Gain of 25dB

Simulated BW: 33.6- 39.4GHz (15.8%)

Conclusions

EMCP Antenna Array technique gives broadbandwidth and high gain.

It has been analyzed that order of losses in microstriplines at higher frequency is as follows:

50 Ω > 70.7 Ω > 100Ω

Gain improvement of 1.5 dB using the low loss network in achieved in 2×2 EMCP-MSAA

Due to low loss feed network EMCP antenna arraygives gain of at least 25 dB.

With lossy feed network the gain would have beeneven lower than Microstrip Antenna Array.

Indian Institute Of Technology Bombay, India 16

References

1. G. Kumar and K. P. Ray Broadband Microstrip Antenna, Artech House, USA 2003.

2. R. Garg, P. Bhartia, I. Bahl, and A. Ittipiboon, Microstrip Antenna Design Handbook. Boston, MA: Artech House, 2000.

3. Yiwei Wu; Qi Zhu, "Design of a Ka-band microstrip antenna array with sharped-beam pattern and high gain," Antennas and Propagation Society International Symposium (APSURSI), 2013 IEEE , pp.1582-1583, 7-13 July 2013

4. Sabban, A., "Ka band microstrip antenna arrays with high efficiency," Antennas and Propagation Society International Symposium, 1999. IEEE , vol.4, pp.2740- 2743 vol.4, 11-16 July 1999

5. Aixin Chen; et. al, "A -Band High-Gain Circularly Polarized Microstrip Antenna Array," Antennas and WirelessPropagation Letters, IEEE , vol.9, pp.1115,1118, 2010

6. Yi-Chun Lilia Liu; Yuanxun Ethan Wang, "A 16×16 ka band aperture-coupled microstrip planar array," Antennasand Propagation Society International Symposium, 2007 IEEE , pp.4373,4376, 9-15 June 2007

7. Huang, J., "A Ka-band circularly polarized high-gain microstrip array antenna," IEEE Transactions on Antennasand Propagation, vol.43, no.1, pp.113,116, Jan 1995

8. Wolansky, D.; Vsetula, P.; Puskely, J.; Raida, Z., "Broadband small patch antenna array for Ka-band application," ,2013 7th European Conference on Antennas and Propagation (EuCAP), pp.907- 910, 8-12 April 2013

9. Wilke, R.; et.al., "Multi-layer patch antenna array design for Ka-band satellite communication," Microwave &Optoelectronics Conference (IMOC), 2013 SBMO/IEEE MTT-S International ,pp.1,4, 4-7 Aug. 2013.

10. Mentor Graphics Corp., IE3D EM Design System, Ver. 15.0, Wilsonville, USA, 2010.

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