Miniaturization Research On Spherical Dipole Antenna

To prolong the life of electrical and electronic equipment systems and guarantee their stabilities, it is necessary to test their electromagnetic compatibility in the process of research and development. With the unceasing development of mechanical technology and electronics integration technology, the electronic equipment is also in constant miniaturization, which has the characteristics of high integration and portable. Therefore, the test antenna must have characteristics of small volume, wide frequency band and so on.As the carrier of signal, there are many parameters to evaluate antenna’s performance. But in terms of its availability, antenna’s bandwidth and size were paid more attention. As a new type of broadband antenna, the spherical radiation dipole antenna has the special signal processing function, which makes its miniaturization and broadband possible.Through the analysis of its mechanism and combined with domestic early work, the antenna with the fundamental frequency of30MHz is improved, the diameter of which was100mm. By changing antenna’s structure and improving its signal source circuit, the antenna’s miniaturization design has been realized, on the premise that its basic performances are unchanged. Several aspects as follows have been completed:First of all, with the help of Ansoft HFSS, a kind of electromagnetic simulation software, the antennas’model with different sizes was set up. In order to improve computational efficiency, through the analysis of the changing trends of antenna performances after its miniaturization, antenna’s size within the range of70mm-90mm was optimized based on the quasi-newton optimization algorithm of the software. By keeping antenna’s bandwidth unchanged and the analysis of frequency sweep, the ideal size of antenna is80mm.Then, there are two ways to improve the influence on the gain of antenna in low-frequency after its miniaturization. They are antenna loading technology and the way to increase the dipole effective length. Based on HFSS, the antenna model of80mm with different structure was set up. And by simulation, its result shows that the pre way has effectively improved its gain in low-frequency and suppressed its gain in high-frequency, while the latter approach has increased its radiation range but has no significant influence on antenna’s gain.In addition, the E plane direction of antennas with these two structure are in "8" figure, which shows that antennas keep omnidirectional radiation characteristics.Besides, the effect on wave was analyzed with different model and parameter of components in the core part of circuit on the basis of Multisim, a kind of circuit simulation software. Considering various factors, such as the circuit’s efficiency, etc., the appropriate model and parameter of components was chosen. Since then, the circuit experiment board was built and tested by the Agilent oscilloscope. And the result shows that the time of the rising edge of square wave is shorter after the improvement of the circuit.Finally, a rough draw of the front view and internal subdivision graph of the spherical dipole antenna after miniaturization and improvement was drawn by SolidWorks, the3D mechanical CAD software. And the miniaturization design of the whole spherical dipole antenna was completed.