Glossary of EE Terms


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  • Packet

    A digital communications technique involving the transmission of short bursts of data in a protocol format that contain addressing, control, and error-checking information, along with the field information, in each transmission burst.

  • Particle Analysis

    A laser or light source is used to illuminate small particles. The reflection of the light source is detected by a photodiode array. This is used to measure the angle and magnitude of the reflection, and from this the size of the particles can be computed.

  • Pass Band

    Frequency band in which any input applied therein passes unattenuated to the DAC output.

  • Periodic Motion

    Periodic motion is motion that repeats itself at definite intervals of time.

  • Phase Locked Loop (PLL)

    A circuit containing a voltage-controlled oscillator whose output phase or frequency can be "steered" to keep it in sync with a reference source. A PLL circuit is generally used to lock onto and "up-convert" the frequency of a stable source.

  • Phase Shift Keying (PSK)

    A digital modulation technique whereby the phase of a carrier frequency is shifted to represent a digital "1" or "0" state. In "Quadri-phase-shift keying" systems, the phase angle locations of 0°, ±90°, and 180° are used as reference points to represent sixteen possible digital states (24).

  • Phased Array

    In wave theory, a phased array is an array of antennas. When transmitting the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions. When receiving, the variance of the signal, as observed at each antenna element, can be utilized or weighted to manipulate the beam pattern of the array or to determine the angle of arrival of the signal.

  • Pitch Axis

    Pitch axis is the Y rotation axis in a 3D system. (See Figure 1)


  • Platform Stabilization

    Compensating for platform instability or unwanted motion caused by shock, vibration, pitch and/or roll. Typically, motion sensors such as gyros and accelerometers detect and calculate the motion of the platform, providing input to digital signal processing functions which enable the unwanted effects of the motion to be mathematically corrected or counteracted.

  • PLC - Programmable Logic Controller

    A programmable logic controller (PLC) or programmable controller is a digital computer system for automation of electromechanical processes, such as the control of machinery on factory assembly lines. PLCs are designed for multiple input and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.

  • Positive Emitter Coupled Logic (PECL)

    An ECL (Emitter Coupled Logic) device biased to a positive power supply voltage.

  • Positive Full Scale Error

    For bipolar input ADCs, this is the deviation of the last code transition from the ideal +FS – 3/2 LSB after the Bipolar Offset Error has been adjusted out.

  • Power Supply Rejection Ratio (PSRR)

    The ratio of the change in supply voltage to the equivalent (differential) input voltage it produces in the op-amp, often expressed in decibels. An ideal op-amp would have infinite PSRR. The data sheet specification is usually at DC (zero frequency); often an operational amplifier will also have its PSRR over frequency in a performance graph.

  • Power Supply Sensitivity - PSS

    Power supply sensitivity is the sensitivity of a converter to changes in the power-supply voltages. This is normally expressed in terms of the percent of full-scale change in the output for a 1% dc change in the power supply.

  • Programmable Gain (PGA)

    An amplifier with an analog- or digitally-controlled gain amplifier function. A PGA can be used in front of an A/D converter to effectively increase its dynamic range.

  • Pseudo-noise

    Any group of code sequences that exhibit a noise-like characteristic.

  • Psophometric Weighting

    Psophometric weighting is a special noise weighting used in measuring noise of telecommunications circuits.

  • PSRR

    Power Supply Rejection Ratio, in dB, larger absolute value is better.

  • Pulse Code Modulation

    A method of quantizing audio-range analog signals into a digital form for transmission in digital communications systems or for processing in DSP. Effectively the same as Analog-to-Digital conversion.

  • Pulse Modulation

    Pulse modulation is one of several means for transmitting digital information in the form of a pulse train. The techniques include PAM (pulse amplitude modulation), PWM (pulse width modulation), PFM (pulse frequency modulation), and QAM (quadrature amplitude modulation). These are successively more sophisticated techniques that improve on the noise immunity of the transmission, and ultimately, through multi-level QAM, send more information with the same bandwidth.

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