Parts per million (PPM) Commonly used as a measurement of the frequency accuracy and in Software

Generating Code 128B in Software Parts per million (PPM) Commonly used as a measurement of the frequency accuracy and

specified as being frequency accurate to within 01 PPM However, since this oscillator is rated as accurate to within 01 PPM, then we know that its frequency may vary by a maximum of 1550 Hz from the rated frequency, or 01/106 155 MHz = 155 Hz

The average peak power of a linear signal with 100% modulation applied to the carrier, specified in watts or dBm A circuit used to confine a signal s maximum output amplitude

The Phy, or physical, layer defines the modulation and signaling attributes for wireless data transmission

Poles A mathematical solution that is used in filter design to describe the points of a filter s transfer function that have infinite insertion loss, and that form a rolloff of 6 dB/octave A series capacitor will thus act as a pole an open circuit at DC, while a series inductor acts as a pole at infinite frequency Therefore, lowpass filters of the all-pole variety, such as Chebychev and Butterworth types, will have their poles all located at infinite frequency Port The location within a circuit or device that a signal can be inserted or extracted, either

Power spectral density (PSD) The measure of the RF power within a given bandwidth, specified in dBm/Hz, VRMS2/Hz, or W/Hz Processing gain In direct-sequence spread spectrum (DSSS) communications, a modulated

signal is sent into a correlator that spreads the signal over a much wider bandwidth than is actually required for the information being carried The signal is then received, and the information is despread This action creates processing gain, specified in dB Processing gain in DSSS systems is obtained by the multiplication of data by the PN code, since it spreads the information out over a low spectral power density due to the much higher rate of the PN code over that of the information The processing gain can simply be viewed as the difference in amplitude between the unspread and the spread signal Because the transmitter spreads the intelligence out before it transmits it, and the receiver despreads it (ie, converts it back to a narrowband signal), any interference at the receiver is converted to wider band, low-amplitude signals with a very low power spectral density This means that the higher the processing gain, the more an interferer s ability to damage or destroy DSSS communications is reduced

Radial stub A microstrip open stub on a PCB, flared like a trumpet bell at its open end, that permits a broad range of frequencies to pass as an RF short circuit Radials A simulated earth ground It is a groundplane or counterpoise, normally consisting of four or more quarter-wavelength wires laid on or in the earth, that are used when insufficient conditions exist for grounding a quarter wavelength vertical antenna Radiation pattern The typical two-dimensional graphical polar representation of the

antenna s far field and relative radiation amplitude versus a spatial direction angle, in degrees, in both the azimuth (0 to 360 ) and the elevation (0 to 90 ) planes, normally in dB

contributes to the RF signal s radiation, as opposed to the loss resistance, which is the resistive portion of the antenna s input impedance that only contributes to heating of the antenna s structure In other words, the radiation resistance is the only part of an antenna s input impedance that actually performs useful work

Radio frequency interference (RFI) Interference created by a generator of RF, such as a wireless transmitter, computer, or even the local oscillator of a radio receiver, into any other electronic device Received signal strength indicator (RSSI) meter A relative or real power indicator of the

strength of the RF signal reaching a receiver This signal strength is obtained from the AGC or RSSI circuits