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### 116 Cards in this Set

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 Modulation put information on high frequency carrier intelligence single low frequency information demodulation remove in the intelligence from the modulation transducer converts energy from one form to another deciels (db) calculated values in noise analysis with respect to a standard or specific reference reference voltage equation db = 10 log P2/ P1 or 10 log V2^2 / V1^2 voltage gain equation db = 20 log V2/V1 1 mw equals how many db? 0db db micoV equation 20 log V2 / 1 microV electrial noise undesired voltages or currents or static external noise noise in receiver introduced by transmission medium internal noise noise caused by the receiver wave propogation movement of radio signals through the atmosphere from transmitter to receiver atmosperic noise external noise caused by disturbances in Earth atmosphere Space noise from outer space solar noise cycle, peaks about every 11 years cosmic noise from other stars not our sun thermal, Johnson, or white noise caused by interaction between the free electrons in vibrating ions in a conductor power noise equation Pn = KT deltaF = watts K = 1.38e-23, T = resistor temp in kelvin, deltaF = Freq band width of the system (RMS) noise voltage equation en = sqr(4K * T * deltaF * R) how do you convert Celsius to Kelvin? Add 273 low-noise resistor resistor with low level of thermal noise shot noise noise introduced by carriers in that pn junctions of semiconductors excess (flicker, pink) noise at <1kHz, varying in aptitude inversely proportional to frequency Transit-time noise in semiconductors, when transit time of the carriers crossing a junction is close to the signals., some defuse back to the source or a meter of the semi conductor signal-to-noise ratio equation signal power / noise power = 10 log Ps / Pn = db (P = V^2/R) noise figure how noisy a device is in db's NF noise figure equation 10 log NR = db NR noise ratio input / output (Si/Ni) / (So/No) S = signal, N = noise octave upper frequency is double lower frequency Equivalent bandwidth equation DeltaFeq = (pi/2)*BW Friiss's formula purpose method determined total noise in multistate system (amplifier stages in cascade) equivalent noise temperature usually for microwave receivers (>1GHz) especially space systems equivalent noise temperature equation Teq = To( NR - 1) To = 290 K (kelvin) SINAD the effects of noise and distortion on an amplifier or receiver diode noise generator use a diode that produces a known noise unto the amplifier under test DUT device under test an electronic part or system that you are testing noise ratio equation NR = 20 Idc * R I = amps, R = impedance of DUT, T = 290k (room temp) what is kelvin room temperature 290k tangential method method of measuring the amplitude of noise on a signal using an oscilloscope display information theory concerned with optimization of transmitted information channel a band of frequencies Hartley's law greater bandwidth, more information sent information * bandwidth * time of transmission fourier analysis method of representing complex repetitive waveforms by sinusoidal (sinewave) components FFT fast fourier transform a technique for converting time-varying information to its frequency component Frequency domain record data points generated by a time to frequency conversion using the FFT Aliasing errors that occur when the input frequency exceeds one-half the sample rate practical inductors (chokes or coils) used at RF (radio frequency) and above Q quality ratio of energy stored to, energy loss in a component leakage loss of electrical energy between the plates of a capacitor inductor Q equation reactance / resistance = w L / R Capacitor Q equation susceptance / conductance = w C / G 1000 is a good Q dissipation D 1/Q (check on this) resonace circuit a condition whereby the inductive and capacitive reactance have been balanced (Xl = Xc) Resonant frequency equation Fr = 1 /[ 2pi sqr(L*C) ] = Hz voltage out equation e out = e in * R2 / (R1 + R2) = volts total impedance equation Z total = sqr[ (R1 + R2)^2 + (Xl - Xc)^2] = ohms XL inductive reactance equation 2pi * F * L F = ohms XC capacitive reactance equation 1 / (2pi * F * C ) = ohms Z out equation sqr[ R2^2 + (Xl - Xc)^2] = ohms filters bandwidth equation BW = R / 2pi * L BW(Hz), R = resistance total, L = circuit inductance filter quality factor equation Q = Fr / BW what is a tank circuit? A parallel LC circuit L = inductor, C = capitor Poles Number of RC or LC sections in a filter constant-K filter filter whose capacitive and inductive reactance are equal to a constant value k m-derived filters filters that uses a two circuit to provide nearly infinite attenuation at a specific frequency roll-off the rate the attenuation in a filter stray capacitance undesired capacitance between two points in a circuit or a device when does an inductor start to look like a complex RLC circuit? At high frequency Z max equation Q^2 * R (maximum impedance) Harmonics is the nth multiple of the base frequency (it spikes on every odd harmonic) oscillator converts energy from DC to AC flywheel affect repetitive ex change of energy in a LC circuit from the inductor to the capactor and back damped the gradual reduction of a repetitive signal to resistive losses continuous wave on dampened sinusoidal waveform produced by an oscillator in a radio transmitter Barkhausen criteria two requirements for oscillations: loop gain must be at least unity and looked phase shift must be 0° What is the advantage of an crystal oscillator? Have high Q's > 20,000 -> a million over a wide temperature range. Grade I keep in frequency +/- .001 % or +/- 10 ppm (parts per million) Frequency synthesizer oscillator that generates a wide range of output frequencies use in one reference crystal oscillator modulation impressing a low-frequency intelligence signal onto a higher-frequency carrier signal nonlinear device characterized by a nonlinear output versus input signal relationship (hua?) AM waveform (envelope) equation e = (Ec + Ei * Sin wi * t) sin wc * T Ec = peak amplitude of carrier signal, Ei = peak amplitude of intelligence signal, Wi T = radio and frequency of intelligence, Wc T = radio and frequency of carrier signal, w = 2pi * F Upper sideband (USB) band of frequency produced in a modulator from a creation of sum frequencies between the carrier and the information signals lower sideband(LSB) same as USB, just lower end angular velocity (w) the rate of phasor rotation percentage modulation measure of the extent to which a carrier voltage is varied by the intelligence (for AM systems) percentage modulation equation %m = Ei / Ec * 100% (ratio remove 100%) modulation index percentage modulation from 0 - 1 (m = Ei / Ec) over modulation excessive intelligence signal overdrive's an AM modulator producing > 100% modulation sideband splatter distortion resulting in an over modulated AM transmission creating excess of bandwidth What is ei? Intelligence signal side-frequency aptitude equation Esf = (m * Ec) / 2, Esf = side-frequency aptitude, m = modulation index, Ec = carrier amplitude transmitted power Total equation Pt = Pc (1 + M^2 / 2) = Watts, Pt = transmitted power (sideband's and carrier), Pc = carrier power, m = modulation index transmitted current total equation It = Ic*sqr( 1 + M^2 / 2), It = total transmitted current, Ic = carrier current, M = modulation index effective modulation index equation (when modulated by more than one signal) Meff = sqr( M1^2 + M2^2 + ...) Base modulation a modulation system in which the intelligence is injected into the base of a transmitter high-level modulation intelligence superimposed on the carrier at the last point before the antenna (for AM), most efficient for high power AM radio low-level modulation intelligence superimposed on the care, and THEN amplified before the antenna neutralizing capacitor a capacitor that cancels fed-back signals to suppress self-oscillation parasitic oscillations higher-frequency self-oscillations in RF amplifiers Modulated amplifier stage that generates the AM signal driver amplifier amplifier stage that amplifies a signal prior to reaching the final amplifier stage in a transmitter Keying concerns that oscillator starts by a turning DC on and off Low excitation improper bias or locator signal power in an AM modulator downward modulation the decrease in DC output current in an AM modulator usually caused by low excitation spectrum analyzer instrument used to measure the harmonic content of a signal by displaying a plot of amplitude versus frequency spurious frequency extra frequencies components that appear in the spectral display of a single, signifying distortion Spurs undesired frequency components of a signal noise floor the baseline on a spectrum analyzer display relative harmonic distortion expression specifying the fundamental frequency component of a signal with respect to is large is harmonic in db THD total harmonic distortion a measure of distortion that takes all significant harmonics into account THD equation THD = sqr ( V2^2 + V3^2 + ...) / V1^2) Dummy antenna resistive load in place of an antenna for testing so there is no output signal TRF (tuned radio frequency) the most elementary receiver design, consisting of RF amplifier stages, a detector and audio amplifier stages sensitivity the minimum input RF signal to a receiver required to produce a specified audio signal at output noise floor the baseline on a spectrum analyzer display, represent an input noise of the system under test selectivity how much the receiver can differentiate the desired signals and other signals