B. V. Sychev – Ph.D. (Eng.), Senior Research Scientist, Director of SPP “Axion-RTI” (Moscow)

N. B. Ablin – Chief Specialist,

SPP “Axion-RTI” (Moscow)

E-mail: mail@axion-rti.ru

E. Yu. Lozovskij – Senior Lecturer,

Russian University of Transport (Moscow)

E-mail: elozovskiy@miit.ru

Matching of an antenna connected to a receiver or a transmitter with a feed line in the frequency range is relevant for both the single antennas and for the antenna systems such as phased array antennas. There are several ways to suppress the reflected waves in the frequency range of VHF and higher, however when creating broadband HF antennas the task becomes much more complicated, especially in the case of cable feeding because it is not desirable to violate the integrity of the cable to include matching elements. In this paper, we propose to use a tuning element in the form of a short (l /λ = 0,015–0,075) directional coupler with strong coupling (k  0,5), secondary line of which at Zvh < Wl is switched to the generator by a short circuit (the second line end without load). Due to the phase shift at the input of the directional coupler the reflected wave partially goes back to the generator in antiphase and thus the input impedance of the line from the generator approaches the pure active one. A part of the power is reflected from the directional coupler in phase with the main signal, which is equivalent to increase power allocated to the load, that is, improving the degree of matching. When Zvh > Wl  the directional coupler is included by the short circuit at the load side. The effect of improving matching is similar. Matching is maintained in a sufficiently wide bandwidth. As an example of the effectiveness the calculated and experimental results with real antennas of type TW-Axi-1 have been shown.

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