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The red curve is an epicycloid traced as the small circle (radius r = 1) rolls around the outside of the large circle (radius R = 3).. In geometry, an epicycloid (also called hypercycloid) [1] is a plane curve produced by tracing the path of a chosen point on the circumference of a circle—called an epicycle—which rolls without slipping around a fixed circle.
The first antenna is the test antenna whose patterns are to be investigated; this antenna is free to point in any direction. The second antenna is a reference antenna, which points rigidly at the first antenna.
The biconical antenna has a broad bandwidth because it is an example of a traveling wave structure; the analysis for a theoretical infinite antenna resembles that of a transmission line. For an infinite antenna, the characteristic impedance at the point of connection is a function of the cone angle only and is independent of the frequency.
The first technique developed was the far-field range, where the antenna under test (AUT) is placed in the far-field of a range antenna. Due to the size required to create a far-field range for large antennas, near-field techniques were developed, which allow the measurement of the field on a distance close to the antenna (typically 3 to 10 ...
The rhombic antenna is a directional wire antenna used on MF and HF bands for shortwave reception. The antenna consists of a wire suspended above the ground in the shape of a rhombus , terminated at one end by a resistor equal the the wire's characteristic impedance, about 400 to 600 ohms, and at the other end connected to the feedline to the ...
Animation of an omnidirectional half-wave dipole antenna transmitting radio waves. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves ...
A reference antenna is an antenna with known performance. It is normally used to calibrate other systems. It is normally used to calibrate other systems. During a relative calibration, an antenna's phase center offset (PCO) and phase center variations (PCV) are computed with respect to the reference antenna which is normally assigned zero PCV ...
For most antennas the boresight is the axis of symmetry of the antenna. For example, for axial-fed dish antennas, the antenna boresight is the axis of symmetry of the parabolic dish, and the antenna radiation pattern (the main lobe) is symmetrical about the boresight axis. Most antennas boresight axis is fixed by their shape and cannot be changed.