A broad-bandwidth, electrically small, near-field resonant parasitic (NFRP) dipole antenna has been designed, analyzed, and measured. Unlike conventional active external matching network approaches, a non-Foster component with a negative reactance slope was incorporated into the NFRP element of an Egyptian-axe dipole antenna to significantly increase its bandwidth. The measurement results showed approximately a 25.3 MHz 10 dB bandwidth around 300 MHz for the active system (ka = 0.49), which is 6.02 and 3.89 times greater than, respectively, the simulated and measured values of the original passive design.
The compact TV antenna composed of the unbalanced fed ultra low profile inverted L antenna is proposed. The antenna size is 40 mm by 244 mm by 32 mm. The return loss less than -10 dB is satisfied at the frequencies from 470 MHz to 713 MHz. The directivity is 2.83 dBi to 3.25 dBi.
Applying an iterative scheme, the differential phase shift provided by the circular waveguide with a coaxial dielectric cylinder and an azimuthally magnetized ferrite toroid, is figured in normalized form for normal TE01 mode. The method is based on a repeated numerical solution of the structure's characteristic equation, derived by the complex Tricomi and the real Bessel function, followed by a calculation of the normalized in a suitable way guide radius and phase constant of the wave. The phase shift is found as a difference between the computed numerical equivalents of constants in question for negative and positive magnetization at selected values of the dielectric cylinder to guide radius ratio and the off-diagonal ferrite tensor element. The relative permittivity of the dielectric is assumed larger than that of the ferrite. The results are presented graphically and debated.
This study presents an implementation of direction-of-arrival estimation using signals received from a Rotman lens array antenna. The algorithm is based on the magnitude comparison method. The Rotman lens array provides multiple beams toward different directions simultaneously. The beam port outputs, which are converted to the video band using envelope detectors, form an output vector. It is used to find the most likely arriving angle based on a higher order interpolation process. In this work, a planar Rotman lens consists of 6 antenna ports and 13 beam ports was fabricated with an FR4 printed circuit board. The lens was connected to 6 broadband Vivaldi horns to form the receiving array. Array patterns are verified in a spherical near field chamber, while the direction finding algorithm was implemented offline using data taken from an open site. Improved direction finding accuracy demonstrates the effectiveness of the proposed Rotman lens array antenna and the developed algorithm.
