Publicado 12 números por año
ISSN Imprimir: 0040-2508
ISSN En Línea: 1943-6009
Indexed in
ANALYSIS OF CHARACTERISTICS OF TWO-FREQUENCY (THREE-FREQUENCY) ANTENNAS WITH REACTIVE LOADS
SINOPSIS
The results of a theoretical and experimental study of distribution of the complex current amplitude, input impedances, voltage standing wave ratio, and the directional patterns of multifrequency and two-frequency linear microwave wire antennas with quarter-wave coaxial or two-wire shunts and with concentrated reactive loads are presented. As the result of the research it was determined that at a constant size of a quarter-wave shunt attached to the antenna and at different antenna dimensions with respect of the shunt, the antenna can either acquire or lose the multifrequency property. Namely, with the length of the wire rod protruding beyond the shunt equal to an odd number of quarters of the short wave in the upper frequency range the multifrequency mode is obeyed. Otherwise, the multifrequency mode is not respected. The principle of eliminating the above-mentioned drawback and creation of two-frequency antennas for operation with an arbitrary ratio of the compatible frequencies is suggested and experimentally tested. This principle consists in adjusting the electrical length of the wire rod of the antenna that protrudes beyond the shunt by serial connection of the concentrated reactive load into its gap, the value of which must satisfy two conditions–creation of the maximum potential difference in the aperture of the shunt at the upper operating frequency and ensuring the mode of the serial resonance of the antenna at the lower operating frequency. The results of the research are presented in the form of tables and graphs of current distribution, input impedances, VSWR and directional patterns of similar antennas, as well as the values of inductive loads calculated according to the suggested expression and connected into the protruding part of the antenna rod outside the shunt. The proposed method for calculating and optimizing two-frequency antennas for operation with an arbitrary ratio of compatible frequencies was experimentally tested. It is noted that the investigated two-frequency antenna with two-wire linear shunts and with connected inductive loads, is one of the promising options for development of the small-size two-frequency antennas and antenna arrays in the microstrip execution.