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Technical
Glossary - R
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| W,X,Y,Z | Spec.
Char., Number |
Radiated
Frequency
The frequency of a signal that is transmitted
by a radio, radar, navigational aid, or other
radio frequency equipment. Radiated frequency
is abbreviated as "RF."
Radio
A collection of circuits that converts electromagnetic
energy gathered from free space to electrical
or sound energy, vice versa or both.
Radio
Frequency
Any electromagnetic frequency from a few hertz
up to frequencies in the infrared portion of the
spectrum, to approximately 300 THz (terahertz).
Ratio
The division of one quantity by another, thereby
indicating their relative magnitudes and phase.
Reactance
Frequency-dependent impedance that is capable
of storing but not dissipating energy. Reactance
can be capacitive or inductive.
Receiver
Protector
A circuit or device that prevents incident high
power, potentially-damaging signals from propagating
to sensitive receiver components.
Receiver
Sensitivity
The minimum received signal power level for which
a receiver can produce a discernible output signal.
The following equation for the sensitivity of
a receiver shows the parameters that affect a
receiving system's sensitivity
S = -114 dBm + NF0+10 log10B+10 log10 S/N,
where S is the receiver sensitivity in dBm, NFO
is the receiver overall noise figure in dB, B
is the receiver bandwidth in MHz, and S/N is the
minimum acceptable receiver signal to noise ratio
in dB.
Recovery
Time
The time interval required, after a sudden decrease
in input signal amplitude to a system or transducer,
to attain a stated percentage (usually 63 percent)
of the ultimate change in amplification or attenuation
due to this decrease.
Reflection
Coefficient
At a specified plane in a uniform transmission
line, the vector ratio of the reflected to the
incident waves. The symbol for reflection coefficient
is "G".
Reflection
Loss
The part of transmission loss due to power reflected
by a discontinuity (impedance mismatch) in a transmission
line.
Reliability
The probability that a device, component or system
will perform adequately for the expected time
under given conditions.
Repetition
Rate
The number of occurrences of an event per unit
time.
Residual
FM
Undesirable, apparent frequency modulation of
a signal source caused by noise or spurious signals.
Resistance
The frequency-invariant opposition to current
flow, abbreviated as "R." The unit of
resistance is the ohm (W).
Resonant
Frequency
The frequency at which the inductive and capacitive
reactances of a circuit are equal in magnitude,
thereby canceling each other's effects. The symbol
for resonant frequency is "fR."
Return
Loss
At a given point in a transmission system, the
difference between the incident and reflected
power.
Rex
Univariable Whisker Press
A machine invented at Microwave Associates (predecessor
of M/A-COM) to form and manufacture the precise,
sharply pointed whiskers that were required for
point contact diodes.
RF
(see "Radiated Frequency"). Also used
as an abbreviation for Radio Frequency, used as
a noun or adjective.
RF
Frequency
The frequency in the portion of the electromagnetic
spectrum that is loosely considered to be between
above the audio-frequency portion and the infrared
portion. It is normally 20 kHz to hundreds of
GHz.
RF
Impedance
The impedance of a circuit or component at high
frequencies.
RF
Impedance
The impedance of a circuit or component at high
frequencies.
Ripple
Variation in magnitude
RMS
or rms
(See "Root Mean Square")
Root-Mean-Square
The effective value of a periodic quantity, equal
to the square root of the average of the squares
of the values of a periodic quantity measured
throughout one complete cycle.
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