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Technical
Glossary - I
| 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 | Spec.
Char., Number |
IC
(see "integrated circuit")
IF
(See "intermediate frequency")
IF
Bandwidth
The frequency interval in a receiver over which
the amplifiers, filters and other components that
process the IF are deigned to operate.
IF
Impedance
The average of the time varying impedance of a
mixer diode at some nominal IF frequency (usually
30 MHz). It is measured with an admittance bridge
at a constant rectified current (normally 1 mA)
produced by the LO signal. Most Schottky diodes
will have IF impedances in the range of 150 -
400 ohms at 1 mA.
Image
Frequency
The frequency of an unwanted signal that may be
incident on a down converter mixer that can produce
the same IF as the desired signal. For example,
if the desired frequency is 2 GHz and the LO frequency
is 1.9 GHz, the image frequency is 1.8 GHz since
the differences between 2.0 GHz and 1.9 GHz and
between 1.9 GHz and 1.8 GHz are both 100 MHz.
Image
Rejection Mixer
A mixer that is designed to reject signal at the
image frequency.
IMPATT
Acronym for "Impact Avalanche Transition
Time", which describes a class of semiconductor
devices that can produce negative resistance.
An IMPATT diode typically consists of 4 layers:
N+-p-i-p+ or p+-n-i-n+. In either case, when the
p-n junction is under avalanche, there is a 90°
phase shift between the resultant AC voltage across
and current through the junction. The thickness
of the I layer is designed to provide an additional
90° phase shift, thereby totaling 180°.
Impedance
The vector ratio of voltage to current, the reciprocal
of admittance. The unit of impedance is the ohm
(×). Impedance is typically abbreviated
as "z" or "Z". The frequency-invariant,
real component of impedance is resistance. The
frequency-variant, imaginary component of impedance
is reactance. The reciprocal of impedance is admittance.
Impedance
Matching
The act of designing a circuit such that if the
circuit is opened at any point, the impedance
measured in either of the two resulting branches
is equal. Maximum power is transferred through
a circuit when impedances are matched.
In
Phase
When two or more periodic, time-varying waveforms
are simultaneously at the same phase angle and
trending in the same direction.
Incident
Wave
The wave front that impinges upon a device
Inductance
The property of a circuit or component that tends
to oppose changes in current due to the magnetic
field that is a result of the current itself.
The unit of inductance is the henry, abbreviated
"H". The schematic representation of
inductance is designated as "L."
Inductive
Coupling
Magnetic linkage between physically unconnected
signal paths or devices.
Inductive
Reactance
The opposition to alternating current flow presented
by a capacitance. The symbol for capacitive reactance
is XC. The unit is the ohm. The formula for capacitive
reactance is XL = 2ðfL, where f is the frequency
of the alternating current signal, and L is the
inductance.
Input
The part of a circuit or device into which a signal
is directed or applied. The signal that is applied
to a circuit or device.
Insertion
Loss
The ratio between the amplitude of the output
signal of a device or circuit compared to the
amplitude of its input signal. Insertion loss
is normally expressed in decibels (dB).
Insulating
Layer
A coating or volume of dielectric material.
Integrated
Circuit
A monolithic device that contains more than one
component.
Intercept
Point
The point at which two lines intersect.
Intermediate
Frequency
The desired output frequency from the down conversion
mixing process, which is normally the difference
between the LO and signal frequencies, i.e., (LO-RF)
or (RF-LO).
Intermodulation
Distortion
The distortion produced by nonlinear impedance
in a component or system when two or more signals
with distinct frequencies are present. Intermodulation
products occur at the sums and differences of
all harmonics of the original signals.
Intermodulation
Frequencies
Frequencies of signals that are generated as a
result of the combination of harmonic generation
and mixing action of multiple input signals by
nonlinear impedances in a system or device. For
the case where there are two input signals, the
intermodulation frequencies that are produced
are given by
IMm+n = m*f1 ± n*f2,
where m and n are positive integers beginning
with 1, and m+n is defined as the order of the
Intermodulation product.
Ion
Implantation
The introduction of free ions into a material
by accelerating them, under the influence of a
large electromagnetic field, through space into
a target material such as a semiconductor wafer.
Ion implantation is used in the semiconductor
industry to add dopants to wafers at low temperature,
rather than to use high temperature diffusion
or epitaxial deposition techniques.
IS-95
A digital mobile telephony air interface standard
that uses CDMA transmission.
Isolation
The difference in power, expressed in dB, between
the input level and output level when unit is
in high loss condition.
Isolator
A three port circulator with one of its ports
terminated with its characteristic impedance.
I-V
Transfer Characteristics
The curve that is produced when the current that
flows in a device is plotted against the voltage
that is impressed across the device. The I-V transfer
characteristic of a passive component, such as
a resistor, capacitor or inductor is linear. The
I-V transfer characteristic of a semiconductor
junction is exponential.
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