design and analysis of simple dual band multimode conical

International Journal of Electrical Electronics & Computer Science Engineering

Volume 5, Issue 2 (April, 2018) | E-ISSN : 2348-2273 | P-ISSN : 2454-1222

Available Online at www.ijeecse.com

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Design and Analysis of Simple Dual Band Multimode Conical Horn for C Band

Balvant J. Makwana1, S. B. Sharma

1Assistant Professor, EC Department, Government Engineering College, Rajkot, Gujarat, India

[email protected]

Abstract: A very simple multimodal horn used for dual band

(at 4 and 6 GHz) has been designed and simulated. The horn

radiates hybrid mode pattern over C band with centre

frequency of 5.8 GHz. By simple calculation without any

optimization symmetric radiation patterns and coincident

phase centers in the principal planes with cross polarization

better than -25 dB is obtained about 39% bandwidth in lower

frequency band and 18.80 % in higher frequency band is

achieved.

Keywords: Cylindrical Horn, Dual Band, Multimode,

Smooth Wall Broadband Horn.

I. INTRODUCTION

Many applications, associated with radio astronomy and

satellite communication, require feed horns with

symmetric E- and H-plane patterns with low side lobes

and low cross-polarization. This can be achieved using

“scalar” feed, which has a beam response that is

independent of azimuthal angle. Corrugated feeds [1]

approximate this idealization by providing the

appropriate boundary conditions for the hybrid

mode at the feed aperture. Alternatively, an

approximation to a scalar feed can be obtained with a

multimode feed design. First of this kind is “dual-mode”

Potter horn [2]. In this an appropriate mixture of is

generated from the initial mode using a step

discontinuity in the waveguide. The two modes are then

phased to achieve the proper field distribution at the feed

aperture using a length of waveguide. The length of the

phasing section limits the bandwidth due to the

dispersion between the modes. Lier [3] has reviewed the

cross-polarization properties of dual-mode horn antennas

for selected geometries. Other authors have produced

variations on this basic design concept [4], [5].

Improvements in the bandwidth have been realized by

decreasing the phase difference between the two modes

by [6], [7].

To increase the bandwidth, it is possible to add multiple

concentric step continuities with the appropriate modal

phasing [8], [9]. A variation on this technique is to use

several distinct linear tapers to generate the proper

modal content and phasing [10], [11]. Operational

bandwidths of 15–20% have been reported using such

techniques. A related class of devices is realized by

allowing the feed horn profile to vary smoothly rather

than in discrete steps. Examples of such smooth-walled

feed horns with appx 15% fractional bandwidths exist in

the literature [12], [13].

Carpanter E.[14] uses a corrugated input section to

excite the desired ratio of the and modes in

a smooth-wall horn to achieve low cross-polarization

performance. This corrugated-to-smooth-wall transducer

has substantially more bandwidth and is less dispersive

than the conventional Potter step. But the fabrication of

this kind of horn will be somewhat complex due to

presence of corrugated section.

In this paper, we describe the design of a very simple

smooth horn for dual band having downlink frequency

of 3.7 to 4.2 GHz and uplink frequency of 5.9 GHz to

6.5 GHz .It utilize mode in addition to

fundamental mode in proper amplitude and phase

which results in low crosspolarization and axisymmetric

radiation pattern with and return loss below -20 dB over

designated band.

This kind of feed can be used as a feed for symmetrical

reflector for wideband operation.

II. DESIGN PROCEDURE

The horn is exited by fundamental mode at the input

waveguide the radius a must be large enough for support

the mode but small enough to ensure that the

is cut-off (i.e., l.84 < ka < 3.83).

The mode, has a cut-off wave number

Therefore input horn radius must be

(1)

Length ( ) of input waveguide is chosen as a .

Where

(2)

and

(3)

Mode conversion from to is obtained by

either symmetric or asymmetric discontinuity. Here

instead of using a step discontinuity we use tapered

section.

The tapered section between two smooth wall cylindrical

waveguide acts as a symmetrical discontinuity and it

may excite higher order modes.

The flare angle could be between 25 to 30 degrees. We

have chosen 28 degree flare angle.

The discontinuity is suitable for mode conversion

because it perturb the incident wave in such way as

it produce a component of field in direction of

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propagation. At discontinuity the conducting surface is

transverse to direction of proportion therefore as per

boundary condition electric field produce in propagation

direction

The amount of generated in this way increases

with the ratio b/a, but b should not be so large as to

permit the mode to propagate (3.8 < kb < 5.33).

The amount of power transferred from to

will dependent on difference of diameter of circular

waveguide. The power in mode should be 10% to

20 % of power in mode. This power is required to

make surface current approximately zero at the aperture

and get symmetry in all planes.

The radius of output waveguide is chosen keeping mind

the above consideration as

(4)

once input and output radius and flaring angle is

determined we can calculate length of flaring section by

simple geometry

(5)

Due to addition of and mode there will be a

phase different between two modes because phase

velocity of both modes is different. At the mouth of horn

antenna to make surface current very small we need both

the modes are in phase. Hence we have to choose perfect

length for phasing section ( )

If represents the launch phase and represents the

differential phase in the constant-phasing section then

the condition for reinforcement of the electric fields at

the aperture center is,

(6)

Where

(7)

(8)

(9)

= 1.841 for = 3.832 for

Using Equation 5 to Equation 9 we can calculate length

of phasing section (L3) which will ensure the correct

phase difference between modes at the aperture..

III. IMPLEMENTATION

Following the above procedure we come up with the

dimensions of horn given in table I. The dimensions are

derived directly from the equations without any

optimization.

Table I.

Central Frequency Fc 5.8 GHz

Theta 28 degrees

Input Waveguide Radius (D1/2) 24.7 mm

Aperture Radius (D2/2) 36.28 mm

Length of Input Waveguide ( ) 65.51 mm

Length of Flaring Section ( ) 21.78 mm

Length of Phasing Section ( ) 124.72 mm

Total Length (L) 212.01 mm

Using these dimensions the horn is designed and

simulated in FEM based general purpose software

(HFSS) as shown in fig 1.

Fig. 1. The Geometry of Proposed Dual Band

Multimode Horn (a) Side view (b) Front View

The far field patterns of the simulated horn are shown in

Appendix I. As horn is designed for dual band (in C

Band) which ranges from 3.7 GHz to 4.2 GHz for

Downlink and 5.9 GHz to 6.5 GHz for Uplink. There is

a good axisymmetric radiation pattern over this bands

having crosspolarisation level below -25 dB.

Figure 2 and Fig 3 shows return loss and copolar gain of

antenna. The return loss is acceptable which is less than

-20dB in both the bands also the co polar gain is

increasing with the frequency.

Fig. 2. The Return Loss Performance of the Dual Band

Multimode Horn




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Fig. 3. Copolar Gain Variation in C Band for the

Proposed Dual Band Multimode Horn

Fig 4 shows the peak crosspolarisation in diagonal plane

(45 degree). the bandwidth for lower Frequency band is

about 39% and in higher frequency band it is 18.80 %.

Fig. 4. Peak Crosspolarisation in Diagonal Plane (45

Degree) for the Proposed Dual Band Multimode Horn

IV. CONCLUSION

A new dual-band multimode smooth-walled horn

designed for C band satellite communication using very

simple formulae without any optimization..it offers

complete pattern symmetry in all the planes having

moderate gain and lower crosspolarisation at uplink and

downlink frequency bands with acceptable return loss.

Also the percentage bandwidth achieved in lower

frequency band is 39% and at higher frequency band it is

about 19%..so a wide band performance is obtained by a

single feed .

V. REFERENCES

[1]. P. J. Clarricoats and A. D. Olver “Corrugated

Horns for Microw. Antennas”1984, Peter

Peregrinus

[2]. P. D. Potter "A new horn antenna with suppressed

sidelobes and equal beamwidths" Microw. J., pp.

71-78, 1963

[3]. E. Lier "Cross polarization from dual mode horn

antennas" IEEE Trans. Antennas Propag., vol. AP-

34, no. 1, pp. 106-110, 1986

[4]. R. Turrin "Dual mode small-aperture antennas"

IEEE Trans. Antennas Propag., vol. 15, no. 2, pp.

307-308, 1967

[5]. G. Ediss "Technical memorandum: Dual-mode

horns at millimetre and submillimetre

wavelengths" IEEE Proc. H Microw. Antennas

Propag., vol. 132, no. 3, pp. 215-218, 1985

[6]. H. M. Pickett , J. C. Hardy and J. Farhoomand

"Characterization of a dual-mode horn for

submillimeter wavelengths" IEEE Trans. Microw.

Theory Tech., vol. 32, no. 8, pp. 936-937, 1984

[7]. S. P. Skobelev , B.-J. Ku , A. V. Shishlov and D.-

S. Ahn "Optimum geometry and performance of a

dual-mode horn modification" IEEE Antennas

Propag. Mag., vol. 43, no. 1, pp. 90-93, 2001

[8]. T. S. Bird "A multibeam feed for the Parkes radio-

telescope" Proc. IEEE Antennas Propagation

Symp., pp. 966-969, 1994

[9]. S. M. Tun and P. R. Foster "Computer optimised

wideband and dual-mode horn" Electron. Lett.,

vol. 38, no. 15, pp. 768-769, 2002

[10]. G. Yassin , P. Kittara , A. Jiralucksanawong , S.

Wangsuya , J. Leech and M. Jones "A high

performance horn for large format focal plane

arrays" Proc. 18th Int. Symp. on Space Terahertz

Technology, pp. 199-210, 2007

[11]. P. Kittara , A. Jiralucksanawong , G. Yassin , S.

Wangsuya and J. Leech "The design of potter

horns for THz applications using a genetic

algorithm" Int. J. Infrared Millimeter Waves, vol.

28, pp. 1103-1114, 2007

[12]. C. Granet , G. L. James , R. Bolton and G. Moorey

"A smooth-walled spline-profile horn as an

alternative to the corrugated horn for wide band

millimeter-wave applications" IEEE Trans.

Antennas Propag., vol. 52, no. 3, pp. 848-854,

2004

[13]. J. M. Neilson "An improved multimode horn for

Gaussian mode generation at millimeter and

submillimeter wavelengths" IEEE Trans. Antennas

Propag., vol. 50, no. 8, pp. 1077-1081, 2002

[14]. Carpenter E. 1980, 'A Dual-Band Corrugated Feed

Horn,' Anten, and Prop. Society Int. Symp., Vol.

18, 213-216.

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[15]. D. Olver , P. J. B. Clarricoats , A. A. Kishk and L.

Shafai "Microw. Horns and Feeds "1994, IEEE

Press

[16]. W. Love (ed.), Electromagnetic Horn Antennas

(New York: IEEE Press, 1976).

[17]. K. K. Agarwal and E. R. Nagelberg, “Phase Characteristics of a Circularly Symmetric Dual-

mode Transducer,” IEEE Trans. Microwave

Theory Tech., vol. MTT-18 (December 1970): 69–

71.

[18]. W. J. English, “The Circular Waveguide Step-

discontinuity Mode Transducer,” IEEE Trans.

Microwave Theory Tech., vol. MTT-21 (October

1973): 633–636

[19]. T. Satoh, “Dielectric Loaded Horn Antennas,” IEEE Trans. Antennas Propagat., vol. AP-20

(March 1972): 199–201.

[20]. K. Tomiyasu, “Conversion of TE11 Mode by a

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1969): 277–279.

APPENDIX I

(A)

(B)

(C)

(D)

Fig. 5. Far Field Radiation Pattern Of Propose Multimode D Horn for Downlink Communication (A) Radiation Pattern at

3.7 GHz. (B) Radiation Pattern at 3.9 GHz (C) Radiation Pattern at 4.1 GHz (D) Radiation Pattern at 4.3 GHz.




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(E)

(F)

(G)

(H)

Fig. 6. Far Field Radiation Pattern of Propose Multimode D Horn for Uplink Communication (E) Radiation Pattern at

5.7 GHz (F) Radiation Pattern at 5.9 GHz (G) Radiation Pattern at 6.1 GHz (H) Radiation Pattern at 6.3 GHz.

design and analysis of simple dual band multimode conical

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