Fig. 2: A comparison of the measured input resistances.

Y. Mushiake, “Log-Periodic Structure Provides
No Broad-Band Property for Antennas.”

The Journal of The Institute of Electronics, Information and Communication Engineers, Vol. 82, No. 5, pp. 510-511, May 1999 [1].

This is a short note in Japanese that was prepared to refute a falsified and wrong explanation [2, 3] about the broad-band property of “Self-complementary Antennas”.

The main point of this paper is briefly explained below.

Non-constant-impedance property of incorrectly arranged Log-Periodic Antenna was experimentally verified in 1965 [1] to avoid the necessity of this sort of argument. For that purpose, two exactly identical half-structures of a log-periodic antenna were prepared. At first, they were arranged in self-complementary manner as shown in Fig. 1A, which is a modified self-complementary antenna, and the input impedance was measured. Then only the lower half-structure was rearranged upside down as shown in Fig. 1B. That is evidently a log-periodic antenna too, but the arrangement is in
anti-complementary manner. Then the input impedance was also measured.


Fig. 1A: LP antenna arranged in self-complementary manner.	Fig. 1B: LP antenna arranged in anti-complementary manner.

Fig. 2: A comparison of the measured input resistances.

The measured input resistances for these two antennas are compared in Fig. 2. The results show that the value of input resistance for the antenna 1B which is arranged in anti-complementary manner varies distinctively with the source frequency, while it remain almost constant for the antenna 1A which is arranged in self-complementary manner. This test shows that the incorrectly arranged log-periodic antennas are indisputably not frequency-independent. Furthermore, it can be well understood from the results of these measurements that the “Principle of self-complementarity” is an undoubtedly useful principle for extremely broad-band antennas.

References.

1. Y. Mushiake, “Constant-impedance antennas,” J. IECE Japan, 48, 4, pp. 580-584, April 1965.

2. P. E. Mayes, “Frequency-independent antennas and broad-band derivatives thereof,” Proc. IEEE, 80, pp. 103-112, January, 1992.

3. K. Nagai, “Toward creative research of antennas,”　A record of lectures, J. IEICE, vol. 80, no. 5, p. 424, Upper portion of the right column, May 1997.

(There are seriously wrong explanations about the broadband property of antennas in the references [2] and [3]. Be careful!)

The two figures in this note are reproduced from his old paper published in April

[1].

Self-Complementary Antenna

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