Electronic Communcations part 1

put information on high frequency carrier

low frequency information

remove in the intelligence from the modulation

converts energy from one form to another

calculated values in noise analysis with respect to a standard or specific reference

db = 10 log P2/ P1 or 10 log V2^2 / V1^2

db = 20 log V2/V1

0db

20 log V2 / 1 microV

undesired voltages or currents or static

noise in receiver introduced by transmission medium

noise caused by the receiver

movement of radio signals through the atmosphere from transmitter to receiver

external noise caused by disturbances in Earth atmosphere

from outer space

cycle, peaks about every 11 years

from other stars not our sun

caused by interaction between the free electrons in vibrating ions in a conductor

Pn = KT deltaF = watts K = 1.38e-23, T = resistor temp in kelvin, deltaF = Freq band width of the system

en = sqr(4K * T * deltaF * R)

Add 273

resistor with low level of thermal noise

noise introduced by carriers in that pn junctions of semiconductors

at <1kHz, varying in aptitude inversely proportional to frequency

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 power / noise power = 10 log Ps / Pn = db (P = V^2/R)

how noisy a device is in db's

10 log NR = db

input / output (Si/Ni) / (So/No) S = signal, N = noise

upper frequency is double lower frequency

DeltaFeq = (pi/2)*BW

method determined total noise in multistate system (amplifier stages in cascade)

usually for microwave receivers (>1GHz) especially space systems

Teq = To( NR - 1) To = 290 K (kelvin)

the effects of noise and distortion on an amplifier or receiver

use a diode that produces a known noise unto the amplifier under test

an electronic part or system that you are testing

NR = 20 Idc * R I = amps, R = impedance of DUT, T = 290k (room temp)

290k

method of measuring the amplitude of noise on a signal using an oscilloscope display

concerned with optimization of transmitted information

a band of frequencies

greater bandwidth, more information sent information * bandwidth * time of transmission

method of representing complex repetitive waveforms by sinusoidal (sinewave) components

a technique for converting time-varying information to its frequency component

data points generated by a time to frequency conversion using the FFT

errors that occur when the input frequency exceeds one-half the sample rate

(chokes or coils) used at RF (radio frequency) and above

ratio of energy stored to, energy loss in a component

loss of electrical energy between the plates of a capacitor

reactance / resistance = w L / R

susceptance / conductance = w C / G 1000 is a good Q

1/Q (check on this)

circuit a condition whereby the inductive and capacitive reactance have been balanced (Xl = Xc)

Fr = 1 /[ 2pi sqr(L*C) ] = Hz

e out = e in * R2 / (R1 + R2) = volts

Z total = sqr[ (R1 + R2)^2 + (Xl - Xc)^2] = ohms

2pi * F * L F = ohms

1 / (2pi * F * C ) = ohms

sqr[ R2^2 + (Xl - Xc)^2] = ohms

BW = R / 2pi * L BW(Hz), R = resistance total, L = circuit inductance

Q = Fr / BW

A parallel LC circuit L = inductor, C = capitor

Number of RC or LC sections in a filter

filter whose capacitive and inductive reactance are equal to a constant value k

filters that uses a two circuit to provide nearly infinite attenuation at a specific frequency

the rate the attenuation in a filter

undesired capacitance between two points in a circuit or a device

At high frequency

Q^2 * R (maximum impedance)

is the nth multiple of the base frequency (it spikes on every odd harmonic)

converts energy from DC to AC

repetitive ex change of energy in a LC circuit from the inductor to the capactor and back

the gradual reduction of a repetitive signal to resistive losses

on dampened sinusoidal waveform produced by an oscillator in a radio transmitter

two requirements for oscillations: loop gain must be at least unity and looked phase shift must be 0°

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)

oscillator that generates a wide range of output frequencies use in one reference crystal oscillator

impressing a low-frequency intelligence signal onto a higher-frequency carrier signal

characterized by a nonlinear output versus input signal relationship (hua?)

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

band of frequency produced in a modulator from a creation of sum frequencies between the carrier and the information signals

same as USB, just lower end

the rate of phasor rotation

measure of the extent to which a carrier voltage is varied by the intelligence (for AM systems)

%m = Ei / Ec * 100% (ratio remove 100%)

percentage modulation from 0 - 1 (m = Ei / Ec)

excessive intelligence signal overdrive's an AM modulator producing > 100% modulation

distortion resulting in an over modulated AM transmission creating excess of bandwidth

Intelligence signal

Esf = (m * Ec) / 2, Esf = side-frequency aptitude, m = modulation index, Ec = carrier amplitude

Pt = Pc (1 + M^2 / 2) = Watts, Pt = transmitted power (sideband's and carrier), Pc = carrier power, m = modulation index

It = Ic*sqr( 1 + M^2 / 2), It = total transmitted current, Ic = carrier current, M = modulation index

Meff = sqr( M1^2 + M2^2 + ...)

a modulation system in which the intelligence is injected into the base of a transmitter

intelligence superimposed on the carrier at the last point before the antenna (for AM), most efficient for high power AM radio

intelligence superimposed on the care, and THEN amplified before the antenna

a capacitor that cancels fed-back signals to suppress self-oscillation

higher-frequency self-oscillations in RF amplifiers

stage that generates the AM signal

amplifier stage that amplifies a signal prior to reaching the final amplifier stage in a transmitter

concerns that oscillator starts by a turning DC on and off

improper bias or locator signal power in an AM modulator

the decrease in DC output current in an AM modulator usually caused by low excitation

instrument used to measure the harmonic content of a signal by displaying a plot of amplitude versus frequency

extra frequencies components that appear in the spectral display of a single, signifying distortion

undesired frequency components of a signal

the baseline on a spectrum analyzer display

expression specifying the fundamental frequency component of a signal with respect to is large is harmonic in db

a measure of distortion that takes all significant harmonics into account

THD = sqr ( V2^2 + V3^2 + ...) / V1^2)

resistive load in place of an antenna for testing so there is no output signal

the most elementary receiver design, consisting of RF amplifier stages, a detector and audio amplifier stages

the minimum input RF signal to a receiver required to produce a specified audio signal at output

the baseline on a spectrum analyzer display, represent an input noise of the system under test

how much the receiver can differentiate the desired signals and other signals