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The unit cells are usually backed by a ground plane, and the incident wave reflects off them towards the direction of the beam, but each cell adds a different phase delay to the reflected signal. A phase distribution of concentric rings is applied to focus the wavefronts from the feeding antenna into a plane wave (to account for the varying ...
In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflection from water bodies and terrestrial objects such as mountains and buildings.
To prevent sound waves reflecting directly to the receiver, a diffusor is introduced. [16] A diffusor has different depths in it, causing the sound to scatter in random directions evenly. It changes the disturbing echo of the sound into a mild reverb which decays over time. Diffraction is the
Sound from ultrasound is the name given here to the generation of audible sound from modulated ultrasound without using an active receiver. This happens when the modulated ultrasound passes through a nonlinear medium which acts, intentionally or unintentionally, as a demodulator .
With an operating frequency of 106 MHz and a wavelength of 3 m (10 ft) this large antenna was required to generate a sufficiently narrow beamwidth to locate enemy aircraft. In telecommunications and radar , a reflective array antenna is a class of directive antennas in which multiple driven elements are mounted in front of a flat surface ...
Sound waves in air, in a tube. Sound waves in a solid experience a phase reversal (a 180° change) when they reflect from a boundary with air. [2] Sound waves in air do not experience a phase change when they reflect from a solid, but they do exhibit a 180° change when reflecting from a region with lower acoustic impedance. An example of this ...
In acoustics, acoustic dispersion is the phenomenon of a sound wave separating into its component frequencies as it passes through a material. The phase velocity of the sound wave is viewed as a function of frequency. Hence, separation of component frequencies is measured by the rate of change in phase velocities as the radiated waves pass ...
In other words, it is the point in space at which the combined amplitude of all the reflected echoes are the same as the amplitude of the sound coming directly from the source (D = R). This distance, called the critical distance d c {\displaystyle d_{c}} , is dependent on the geometry and absorption of the space in which the sound waves ...