Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 24

Maxwell's EM‐theory was a controversial theory, and physicists such as Kelvin never accepted it. Hertz finally generated, transmitted, and detected the EM‐waves in 1887 at wavelengths of 5 m and 50 cm. In the process, he invented the loaded dipole as the transmitting antenna, rectangular wire‐loop receiving antenna, and spark‐gap both as transmitter and detector to detect the propagated EM-waves. Thus, he experimentally confirmed the validity of Maxwell equations and opened the magnificent gateway of wireless communication.

In the year 1895, Marconi transmitted and received a coded telegraphic message at a distance of 1.75 miles. Marconi continued his works and finally on December 12, 1901, he succeeded in establishing the 1700 miles long‐distance wireless communication link between England and Canada. The transmission took place using the Hertzian spark‐gap transmitter operating at the wavelength of 366m. In the year 1895 itself, J.C. Bose generated, transmitted, and detected the 6 mm EM‐wave. He used circular waveguide and horn antenna in his system. In 1897, Bose reported his microwave and mm‐wave researches in the wavelengths ranging from 2.5 cm to 5 mm at Royal Institution, London. Of course, the Hertzian spark‐gap transmitter was at the core of his communication system. Bose was much ahead of his time as the commercial communication system grew around the low frequency, and the microwave phase of communication was yet to come in the future. In 1902, Max Abraham introduced the concept of the radiation resistance of an antenna [J.11–J.13, B.1–B6].