The radiation properties of electrically small folded spherical helix antennas

The radiation properties of several electrically small, folded spherical helix antennas are presented. The primary variables considered in the design of these antennas are the number of helical turns and the number of helical arms. The principle design objectives are to achieve self resonance, a low quality factor (Q), and a practical radiation resistance for small values of ka. Designs are presented for ka less than 0.5, where the antennas are self resonant, exhibiting an efficiency in excess of 95%, a Q within 1.5 times the fundamental limit, and a radiation resistance near 50 /spl Omega/. The relationship between the number of helical turns, the number of helical arms, and achieving self resonance at low frequencies is discussed.

[1]  H.A. Wheeler,et al.  Fundamental Limitations of Small Antennas , 1947, Proceedings of the IRE.

[2]  L. J. Chu.  Physical Limitations of Omni‐Directional Antennas , 1948 .

[3]  H. Wheeler.  Fundamental relations in the design of a VLF transmitting antenna , 1958 .

[4]  H. A. Wheeler.  The Radiansphere around a Small Antenna , 1959, Proceedings of the IRE.

[5]  R. Collin,et al.  Evaluation of antenna Q , 1964 .

[6]  Robert M. Fano,et al.  Electromagnetic Energy Transmission and Radiation , 1968 .

[7]  Andrew J. Poggio,et al.  Numerical Electromagnetic Code (NEC) , 1979, 1979 IEEE International Symposium on Electromagnetic Compatibility.

[8]  A. Safaai-Jazi,et al.  Spherical helical antenna with circular polarisation over a broad beam , 1993 .

[9]  Ahmad Safaai-Jazi,et al.  Radiation characteristics of a spherical helical antenna , 1996 .

[10]  Edward K. N. Yung,et al.  The input impedance and the antenna gain of the spherical helical antenna , 2001 .

[11]  R. L. Rogers,et al.  Folded conical helix antenna , 2001 .

[12]  S. Best,et al.  The performance properties of an electrically small folded spherical helix antenna , 2002, IEEE Antennas and Propagation Society International Symposium (IEEE Cat. No.02CH37313).

[13]  S.R. Best,et al.  On the resonant properties of the Koch fractal and other wire monopole antennas , 2002, IEEE Antennas and Wireless Propagation Letters.

[14]  E. Altshuler.  Electrically small self-resonant wire antennas optimized using a genetic algorithm , 2002 .

[15]  S.R. Best,et al.  The effectiveness of space-filling fractal geometry in lowering resonant frequency , 2002, IEEE Antennas and Wireless Propagation Letters.

[16]  S. Best,et al.  On the performance properties of the Koch fractal and other bent wire monopoles , 2003 .

[17]  A.D. Yaghjian,et al.  Impedance, bandwidth, and Q of antennas , 2003, IEEE Transactions on Antennas and Propagation.