Terms starting with ‘S’
- Sectorial Antenna
- A directive antenna with a radiation pattern aperture (3 dB beamwidth) larger than 45°. Sectorial antennas are generally used for point-to-multipoint systems or combined with several antennas to create a base station.
- Shadow Loss
- 1. The attenuation caused to a radio signal by obstructions in the propagation path. 2. In a reflector antenna, the relative reduction in the effective aperture of the antenna caused by the masking effect of other antenna parts, such as a feed horn…
- Shield Effectiveness
- A measurement of how well the shielding material (braid, solid tape, etc.) protects the external environment from radiation produced by the center conductor.
- Side Lobe
- The radiation pattern of most antennas shows a pattern of "lobes" at various angles/directions where the radiated signal strength reaches a maximum, separated by "nulls", angles at which the radiation falls to zero. In a directional antenna the…
- Side Lobe Level (SLL)
- The ratio, in decibels (dB), of the amplitude at the peak of the main lobe to the amplitude at the peak of a side lobe.
- Side Lobe Suppression
- Any process, action or adjustment to reduce the level of the side lobes or to reduce the degradation of the intended antenna system performance resulting from the presence of side lobes. For WLAN antennas, the first side lobe above the horizon is…
- Single-polarized Antenna
- An antenna that radiates or receives radio waves with a specific polarization. Note: For a singly polarized antenna, the desired sense of polarization is usually maintained only for certain directions or within the major portion of the radiation…
- Skip Zone
- An annular region within the transmission range of an antenna, within which signals from the transmitter are not received. Note: The skip zone is bounded by the locus of the farthest points at which the ground wave can be received and the nearest…
- Sky Wave
- A radio wave that travels upward from the antenna and may be reflected to Earth by the ionosphere.
- 1. Rotating a directional antenna or transducer rapidly about one or more axes. 2. Changing the frequency or pulse repetition rate of a signal source. 3. Changing the tuning of a receiver, usually by sweeping through many or all frequencies. 4.…
- Slot Antenna
- A radiating element formed by a slot in a conducting surface or in the wall of a waveguide.
- Slotted Waveguide
- A slotted waveguide has no reflector but emits directly through the slots. The spacing of the slots is critical and is a multiple of the wavelength used for transmission and reception.
- Space Diversity
- Also known as antenna diversity, is any one of several wireless diversity schemes that uses two or more antennas to improve the quality and reliability of a wireless link. Often, especially in urban and indoor environments, there is no clear…
- In an antenna, the part of the radiated energy from the feed that does not impinge on the reflectors.
- Spot Beam
- In satellite communications systems, a narrow beam from a satellite station antenna that illuminates, with high irradiance, a limited area of the Earth by using beam (directive) antennas rather than Earth-coverage antennas.
- Standing Wave Ratio (SWR)
- See also: Voltage Standing Wave Ratio (VSWR)