Definitions in the Radar Field
"A",
"B",
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
"R",
"S",
"T",
"U",
"V",
"W",
"X",
"Y",
"Z"
"S" to "Sensi", "Senso" to "Spoi", "Spok" to "Sz"
Spoking: Periodic flashes of the rotating radial radar display. Sometimes caused by mutual interference.
Spot Jamming: Narrow frequency band jamming concentrated against a specific radar at a particular
frequency. The jamming bandwidth is comparable to the radar bandpass. Can deny range and angle information.
Spurious Emission: Electromagnetic radiation transmitted on a frequency outside the bandwidth required
for satisfactory transmission of the required waveform. Spurious emissions include harmonics, parasitic emissions, and
intermodulation products, but exclude necessary modulation sidebands of the fundamental carrier frequency.
Squint Angle: The angular difference between the axis of the antenna main-lobe and the geometric axis of the antenna
reflector, such as the constant angle maintained during conical scan as the main-lobe rotates around the geometric axis of the reflector.
Staggered PRF: Staggered PRF allows an increase in MTI blind speeds such that no zeros exist in the velocity response at lower velocities. In a two-period mode, the usual "blind speed" or occurrence of a zero in the velocity response
is multiplied by a factor which is a function of the ratio of the two repetition periods.
STAMO: [Stable Master Oscillator] A very stable (drift free) oscillatory used to provide a precise frequency for transmission and for comparison with the reflected radar signal returned to the receiver, such as in a Doppler
radar where a precise difference between transmitted and received signals must be measured to determine accurately the Doppler frequency.
Stand-Forward Jamming: A method which places the jamming vehicle between the enemy sensors and
attack aircraft.
STC: [Sensitivity Time Control] Gain control that reduces the radar receiver gain for nearby targets as compared to more distant targets. STC prevents receiver saturation from close-in targets.
Step Recovery Diode: A charge-controlled switch which ceases current conduction so rapidly that it can
be used to produce an impulse. Cyclic operation of the diode can produce a train of impulses which when used with a
resonant circuit can produce a single frequency output at any harmonic of the pulse frequency.
Steradian: Unit of solid angle. An entire sphere has 4B steradians.
Stub: A short section of transmission line connected in parallel with the main transmission line. Also refer to the related dictionary concerning PWB Terms.
Subharmonic: A frequency which is an integral submultiple of another frequency. For example, a sine wave
whose frequency is one-third of the frequency of another sine wave is called the third subharmonic. (3 MHz is the third sub-harmonic of 9 MHz).
Superheterodyne Receiver: A receiver that mixes the incoming signal with a locally generated signal (local oscillator) to produce a fixed, low intermediate frequency (IF) signal for amplification in the IF amplifiers. Refer to the general engineering dictionary for a AM Receiver Diagram.
Suppression: Elimination or reduction of any component of an emission, such as suppression of a harmonic of a transmitter frequency by band rejection filter.
Susceptibility: The degree to which an equipment or a system is sensitive to externally generated interference.
Switches: See also Diode Switch, Silicon Controlled Switch, Schottky Diode Switch. [RF Switch Manufacturers]
Sychrodyne: A klystron mixer amplifier stage in a transmitter, where two signal frequencies are applied as inputs and a single amplified signal is taken out.
Synthetic Array Radar: [SAR].
