The $B!H(BSelf-complementary antenna$B!I(B 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 $B!H(BFrequency-independent antenna$B!I(B by making use of such a property of self-complementary antenna. For this reason, his antenna was actually $B!H(Blog-periodic self-complementary antenna$B!I(B. 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 $B!H(BLog-periodic antenna$B!I(B or $B!H(BLP antenna$B!I(B. It is well-known that these so-called $B!H(BLog-periodic antennas$B!I(B 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 $B!H(BLog-periodic antennas$B!I(B 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 $B!H(BPrinciple of self-complementarity$B!I(B 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, $B!H(BA report on Japanese developments of antennas: From the Yagi-Uda antenna to self-complementary antennas$B!I(B, IEEE Antennas and Propagation Magazine, Vol. 46, No. 4, pp. 47-60, August 2004.|