“Self-complementary antenna”

“Log-periodic antenna”

     The “Self-complementary antenna” was originated and its constant-impedance property was discovered in 1948 by Y. Mushiake. Several years later, Professor V. H. Rumsey in the USA studied the antenna with log-periodic shape for the purpose of developing “Frequency-independent antenna” by making use of such a property of self-complementary antenna. For this reason, his antenna was actually “log-periodic self-complementary antenna”. In the meantime, his coworkers developed an extremely broadband practical antenna by modifying his original structure, and it advanced further to the log-periodic dipole array. These antennas which are derived from the original log-periodic self-complementary antenna structure are generally called “Log-periodic antenna” or “LP antenna”. It is well-known that these so-called “Log-periodic antennas” have extremely broadband property.

     However, it should be clearly noted here that the log-periodic shape does not provide any broadband property to antennas. In fact, log-periodic antennas arranged in an anti-complementary manner do not have broadband property. Similarly, the log-periodic dipole array does not have broadband property unless it has transposed excitation which is an unavoidable outcome of the modification from the original self-complementary shape. In this connection an example of non-log-periodic LP antenna, a serious claim, is explained in another page.

     From the facts explained above, it is well understood that these so-called “Log-periodic antennas” with extremely broadband property are practical antennas that have been developed from the self-complementary antenna. Nowadays these antennas are quite popular in practice. This means that the “Principle of self-complementarity” is an extensively spread theoretical principle and it is a definitely effective technological principle.

    Consequently, the restriction to the log-periodic shape should be abolished for this type of extremely broadband antennas, and more suitable broadband derivatives of self-complementary antennas should be pursued with raised freedom to meet practical demands, from now on.

See: Y. Mushiake, “A report on Japanese developments of antennas: From the Yagi-Uda antenna to self-complementary antennas, IEEE Antennas and Propagation Magazine, Vol. 46, No. 4, pp. 47-60, August 2004.
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