Biconical AntennaAntenna and Propagation

By :

WHY BICONNICAL ANTENNA ?

• Since 2002, the Federal Communication Commission (FCC) regulated the frequency band from 3.1-10.6 GHz for low-powered ultra-wideband (UWB) wireless communication [1].

• UWB's combination of larger spectrum, lower power and pulsed data improves speed and reduces interference with other wireless spectra.

• Based on the Regulation for UWB communications, one of the most crucial components is the antenna.

• Biconical antenna configuration is one of many configurations [2]-[4] that can be used to achieve broadband characteristics.

DESIGN OF BICONNICAL ANTENNA

The configuration of a biconical antenna fed by coaxial cable is shown in Fig. 1.

The one length is l, cone top radius is , cone bottom radius is the radius of the coaxial cable, flare angle between the two cones is Ψ .

The upper and lower cones are symmetrical.

The cones are excited symmetrically at the apices with the feed gap g.

INPUT IMPEDANCE

The input impedance of the antenna with conical length / and cone angle as given by Papas and King [5] is

where

And

INPUT IMPEDANCE

Where :, : wavelength in free-space,

: Characteristic impedance of the antenna,

: Legendre polynomial of order n, (4)

: complex auxiliary function of the real variable kl,

: spherical Hankel function of the 2nd kind,

: ratio of reflected and outwardly propagating TEM wave in antenna region.

RADIATION PATTERN

where and the summation is over odd integral.

The antenna was considered to be an isolated source in free-space with azimuthally independent radiation in the H -plane. The E-plane far-field radiation pattern normalized to the field at broadside has been analyzed by Papas and King [6], is

RADIATION CHARACTERISTICS

1) Azimuth radiation patterns:

from the antenna configuration (Fig. 1) exhibiting rotational symmetry (around z-axis), hence the radiation characteristic would also be symmetrical (omni-directional) in the azimuth (H-) plane (Fig. 13) [8]-[10].

RADIATION CHARACTERISTICS

2) Elevation radiation patterns:

From the simulation results ( by 2011 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS) ) at different flare angles Ψ (100°, 80°, 60°, 40°, and 20°), for the fixed cone length l equals one wavelength of the center frequency ( ,= 7 GHz), feed gap g 0.5 mm, brass conductivity σ 2.57 x 107 S/m, and at minimum frequency 2 GHz; it was noticed (Fig. 2) that the (E-plane) radiation patterns were bidirectional towards the broadside direction. The beam width became wider with respect to the narrower flare angle of the antenna.

RADIATION CHARACTERISTICS

Radiation Pattern when value of minimum frequency range (f=2GHz)applied to Biconical antenna Design :

RADIATION CHARACTERISTICS

Radiation Pattern when center value of frequency range (f=7GHz)applied to Biconical antenna Design :

RADIATION CHARACTERISTICS

Radiation Pattern when Maximum value of frequency range (f=7GHz)applied to Biconical antenna Design :

RADIATION CHARACTERISTICS

Comparation of Radiation Pattern

at different cone length

RETURN LOSS

RETURN LOSS

RETURN LOSS

GAIN

PHYSICAL DESIGN OF BICONNICAL ANTENNA

REFERENCES

[1] First Report and Order in the Matter of Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems, Released by Federal Communications Commission ET-Docket, pp_ 98-153, 2nd Apr. 2002_ [2] C. Yu, W_ Hong, L. Chiu, G_ Zhai C. Yu, W. Qin, and Z. Kuai, "Ultrawideband printed Log-Periodic dipole antenna with multiple notched bands," IEEE Trans. Antennas Propagat, vol. 59, pp. 725-732, Mar. 2001. [3] P_ Jirasakulporn and P. Akkaraekthalin, "A conpact ultra-wideband rectanllli lar slot antanna tuned with T -shape fractal stub," Electrical Engineering Conference-32, vol. 2, pp. 785-788, Oct 2009_ Prachinburi. Thailand_ [4] H. Schantz, The Art and Science of Ultrawideband Antennas, Artech House Publishers, 2005_ [5] C. H. Papas and R. W_ P_ King, "Input impedance of wide angle conical antennas fed by a coaxial line," Proc_ IRE, vol. 37, pp_ 1269-1271, Nov_ 1949. [6] C. H. Papas, and R. W. P_ King, "Radiation from wide-angle conical antennas fed by a coaxial line," Proc. IRE , vol. 39, pp.49-51, Jan. 1951. [7] CST Microwave Studio, User's Manual, 2011. [8] S_ S. Sandler and R. W_ P. King, "Compact conical antenna for wide band coverage," IEEE Trans Antennas Propagat, vol. 42, no 3, pp. 436-439, Mar_ 1994_ [9] S_ N_ Samadder and E. L. Mokole, "Biconical antenna with unequal cone angles," IEEE Trans_ Antennas Propagat, vol. 46, no 2, pp_ 181-192, Feb_ 1998_ [10] C. Ghosh and T. K. Sarkar, "Design of a wide-angle biconical antenna for wideband communications," Progress in Electromagnetics Research B, vol. 16, pp_ 229-245, 2009_ [11] H. T_ Friis, "A note on a simple transmission fonnula," Proc_ IRE, vol. 34, no 5, pp_ 254-256, May 1946_