DESIGN AND SIMULATION OF H-PLANE SECTORAL HORN ANTENNA...

Chandana & Prudhvi/ Star Vol.5 Issue 12(2), December (2017) ISSN: 2321-676X

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DESIGN AND SIMULATION OF H-PLANE SECTORAL HORN ANTENNA WITH

ENHANCED BANDWIDTH

CHANDANA VISWANADHAM1 & Prof. PRUDHVI MALLIKARJUNA RAO

2

1Ph.D., student Andhra University, Visakhapatnam, Andhra Pradesh, India.

2Professor, Department of ECE, Andhra University, Visakhapatnam, Andhra Pradesh, India.

ABSTRACT

Various standard methods for feeding the pyramidal, cylindrical and tapered horns are popular and used in

many applications. Numerous technical papers are published in the open literature explaining the advantages and disadvantages of these methods. However, it is evident that most of these methods are suitable for narrow band

applications like conventional radars and satellite communications with some limitations. Very few papers have been published which suitable for U.W.B applications. In this paper, an optimized technique to enhance the bandwidth of

H-plane sectoral horn antenna is presented, which is used as an array element for linear array of H-plane sectoral

horns. The enhancement of bandwidth is achieved through optimization of impedance of the feed pin with he suitable mechanical modification. The frequency enhancement, lower down to 6 GHz is achieved without changing the

dimensions of the sectoral horn. It is observed that the simulated and measured results are in agreement.

KEYWORDS: Band Width Ratio (BWR), Electronic Warfare, Impedance, Matching networks, Traveling Wave Tubes (T.W.T), Ultra

Wide Band (U.W.B).

INTRODUCTION

Electronic Counter Measures (E.C.M) systems

are configured with high power transmitters consisting of

Digital Radio Frequency Memory (D.R.F.M), high

power microwave amplifiers and highly directive and

electronically steerable antenna [1-2]. The antenna

should withstand high power signals and shall have good

matching with free space impedance (Z0) of 120π Ω. The

active V.S.W.R of the array is very critical parameter in

these applications and depends on V.S.W.R of each

element in the array. Many engineers have experimented

standard and modified techniques to improve V.S.W.R of

pyramidal horns, such as dielectric loading, stub

matching, etc., [3 – 5]. These authors also explained the

disadvantages of these methods like reduction in gain

and operating bandwidths, though V.S.W.R is improved

to great extent in the operating band. Recently, ridge gap

waveguides are considered as guiding structures in high-

frequency applications. One of the major drawbacks of

these guiding structures is the operating bandwidth and

mostly these structures are suitable for narrow bandwidth

applications. This is not suitable for wide and U.W.B

array applications. Further, to maintain the spacing in the

array of sectoral horn antennas operating in 18-40 GHz,

6-18 GHz and 2-6 GHz frequency range, it is desirable to

feed point of the H-plane sectoral horn antenna element

should be from the back wall of the waveguide adapter.

The wideband coaxial to ridge gap waveguide transition

is based on five different sections of matching networks.

The introduced transition shows excellent return loss,

which is better than 15 dB over the entire frequency

range. In this method the pin of the co-axial connector is

directly inserted in the ridge of the waveguide plate of

the horn body. The radiating elements have smoothly

curved bent in the ridged transmission line in the plates

of the horns, which is suitable for feeding from co-axial

pin. The H-plane sectoral horn, as an aperture control

device, is designed with selected flare angle and aperture

shape is in accordance with the laws of optics for

limiting the beam width in the plane orthogonal to the

plane of scanning of the array.

SPECIFICATIONS

The specifications of the 8-18 GHz sectoral

horn are considered as the targeted specifications of side

fed H-plane sectoral horn antenna with frequency range

of 6-18 GHz in this paper. These are tabulated in Table-1.

These specifications are derived from the open literature.

The objective is to enhance the frequency range of this

antenna down to 6 GHz without any dimensional

changes.

Original Article

STAR Research Journal

Availableonlineatwww.starresearchjournal.com(StarInternationalJournal)

ENGINEERING UGC Journal No: 63023


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TABLE 1

DESIGN SPECIFICATIONS

In the above Table, bandwidth enhancement is

considered by improving the V.S.W.R. without any

change in the dimensions. This is achieved by using

suitable probe for matching the impedance in 6-18 GHz

frequency range.

SPECIFICATIONS

Based on the above requirements, the

dimensional values have been computed using the design

equations [2] and the calculated values are tabulated at

Table-2. In the calculations, the dimension of the antenna

size is 130.55 x 8.2 x 225.35 mm, which is same as the

existing antenna. Now the objective is to design the H-

plane sectoral horn antenna with the same dimensions

with bandwidth enhancement up to 6 GHz. This is

achieved by designing a new feeding probe.

TABLE 2

DESIGN CALCULATIONS

Sl.

No.

Parameter Calculated specifications

1. Frequency

range

6–18 GHz or 8-18 GHz

2. DH (dBi) ~5.5 dBi @6 GHz

13.1dBi @18 GHz

3. DH 3.93 @ 7 GHz

20.46 @ 18 GHz

4. GH 80

5. b 8.2

6. X 8.69mm@ 7 GHz

15.06mm@18GHz

7. A 130.55 mm

8. R0 215.7 mm (Existing

dimensions)

9. lH 225.35 mm (Existing

dimensions)

Where, Hl Slant length of the horn, 0R Straight

length of the horn, A Aperture, H Flare angle,

HR Flare length and a Waveguide height, GH is

calculated constant.

DH is obtained from below equation.

50

HH

H

GbD

l

DESIGN SIMULATIONS

The simulated model of the proposed non

standard back feeding technique for sectoral horn is

shown at Figure-1 and the feeding mechanism is shown

at Figure-2. The impedance matching is carried out with

suitable probing pin to cater for 6-18 GHz frequency

ranges.

FIGURE I

SIMULATION MODEL – SINGLE ELEMENT

FIGURE 2

SIMULATION MODEL OF CONNECTOR PIN –

SINGLE ELEMENT

The design of the probing pin is carefully done

to ensure proper impedance matching between the source

and the free space over the entire frequency range of 6-

18 GHz. The mechanical structure and dimensions of the

probing pin is shown Figure-3.

Sl.

No.

Parameter Targeted specifications

1. Frequency range 6–18 GHz

2. V.S.W.R Max. 3.0:1 (at-least 85% of

band width)

3. Side Lobe Level

(S.L.L)

< -8.5 dB

4. Gain (Min.) 5.5 dBi

5. 3-dB E.P. Beam width 35° Max.

6. 3-dB A.P Beam width 120°Max.

7. Connectors S.M.A (F)

8. Dimensions in mm 130.55 x 8.2 x 225.35

9. Weight Max 15 Kgs

10. Power handling Min 300 Watts


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FIGURE 3

MECHANICAL STRUCTURE OF THE PIN

FIGURE 4

CURRENT DISTRIBUTION ON THE PIN

The current distribution on the pin is shown at

Figure-4. The Figure 4, the current distribution on the

feed pin used for transforming the co-axial to wave guide

transition. The high Power Probe provide accurate

measurement of high power devices up to 3 kV

(triaxial)/10 kV (coaxial) and 400 A (pulse) even at the

elevated temperature of up to 300 C. MPI’s gold plated

high power thermal chucks with evenly distributed

vacuum holes located across the chuck to secure

thin/warped wafers down to 50 Ω and provides excellent

backside wafer contact while achieving low contact

resistance for vertical device RDS (on) measurements.

The probe contains the radio frequency (R.F) coils, tuned

at specific frequencies for specific nuclei in a given

magnetic field. The probe also contains the necessary

hardware to control the sample temperature (when

combined with an external temperature controller). High

power probing solutions include dedicated high voltage

and high current probes are capable of low leakage

current.

The SMA connector is popularly used along

with the probe. The coaxial transmission line terminated

with SMA connectors is the most widely used

transmission line for high frequency (above 1 GHz)

applications. A coaxial line consists of an inner

conductor with diameter (1.43mm) which is surrounded

by concentric cylinder of insulating materials such as

TEFLON. The outer conductor is a concentric cylinder

with inner diameter (5.20mm). The coaxial cable is

unbalanced transmission line the outer conductor is

normally at grounded. Coaxial lines are non-radiating

since electromagnetic fields are confined in the insulator

between the inner and outer conductors. Coaxial line can

operate well up to 40 GHz due to development of

precision connectors for smaller diameter coaxial cables.

The S-parameters of SMA connector is shown below at

Figure-5.

FIGURE 5

S11 OF SMA CONNECTOR

The current distribution on the connector with

side plate is shown at Figure-6.

FIGURE 6

CURRENT DISTRIBUTION ON THE

CONNECTOR AND CONNECTOR PLATE

The simulated V.S.W.R of the antenna with

modified pin is shown at Figure-7.


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FIGURE 7

SIMULATED V.S.W.R OF MODIFIED HORN

The simulated gain is shown at Figure-8.

FIGURE 8

SIMULATED GAIN OF MODIFIED HORN

The simulated radiation patterns at 6 GHz, 10

GHz and 18 GHz are shown at Figure-9, 10 and

11respectively.

FIGURE 9

SIMULATED RADIATION PATTERN AT 6 GHZ

FIGURE 10



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FIGURE 11


The simulated model of eight element linear

array of sectoral horn is shown at Figure-12.

FIGURE 12

SIMULATION MODEL OF EIGHT ELEMENT

ARRAY

The simulated radiation patterns of the array are

shown at Figure-13 to 15. The simulated data with equal

phase to all eight ports are fed and hence the mai beam is

expected at center of the array.

FIGURE 13



12

FIGURE 14


FIGURE 15


MEASURED RESULTS

The measured V.S.W.R plot of the center

element of the assembled linear array of H-plane sectoral

horn with modified probe is shown at Figure-16. The

radiation pattern is carried out by connecting Rotman

lens to the ports of linear array of H-plane sectoral horns.

The measured radiation pattern of all the ports of the

array at 6 GHz, 7 GHz and 8 GHz are shown below at

Figure-17 to 19.

FIGURE 16

V.S.W.R PLOT OF MODIFIED H-PLANE

SECTORAL ANTENNA (6-18 GHZ)

FIGURE 17

RADIATION PATTERN OF MODIFIED H-PLANE

SECTORAL ANTENNA AT 6 GHZ

FIGURE 18



Expected

results


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FIGURE 19



CONCLUSION

A sectoral horn antenna with suitable

modification to feed point for extension of frequency up

to 6 GHz is simulated and presented in this paper. The

V.S.W.R of the antenna is close to the design

specification of 3:1 in the extended frequency range also.

The radiation patterns and gain parameters are also

simulated and presented. The simulation of array has

been carried out for all parameters. The array elements

and connectors are fabricated and is assembled with

modified pins. The measured radiation patterns of the

array are presented in the extended frequency range.

ACKNOWLEDGEMENT

The authors are thankful to the engineers

working at BEL for sparing their valuable time during

the simulation. We also extend our sincere thanks to

management of B.E.L for providing all the facilities like

Simulation tools, High end work stations, during the

simulation work. We sincerely extend our gratitude to

Prof. G Sashibhushana Rao, HOD, ECE department,

Andhra University, Visakhapatnam for his support

during the preparation of the paper.

REFERENCES

1. Hans Schantz, “Antenna as Transducers and

Antennas as transformer“, in the title of Art and

Science of Ultra Wide Band antennas” 1st edition,

2005, Artech publications

2. Pues H.F, “An impedance-matching techniques for

increasing the bandwidth of micro strip antennas”,

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06 Aug 2002.

3. Constantine A Balanis, “Antenna Theory Analysis

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edition, Wiley

India, reprint 2012.

4. Ronaldo O. dos Santos and Carlos Leonidas da S.

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9. Ch Viswanadham, Prof P Mallikarjuna Rao,

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10. M. J. May bell and P. S. Simon, “Pyramidal Horn

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1982.

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