os disk scheduling algorithm

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    V.RAGHAVENDRA12881A04C9

    [email protected]

    Department of Electronics and Communication Engineering

    TECHNICAL SEINAR C!"!NENT#IRECEIVERS

    VARDHAMAN CO!"! O# !N"$N!!R$N"$A%T!N!!%S&

    S'ams'a(ad) H*dera(ad # +,--/

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    RECEIVERS 

    R!C!$V!R%

    2

      Radio r&c&iv&r is a' &l&c(ro'ic&)ui*m&'( +hich *ic, u*s (h& d&sir&dsig'al- r&&c( (h& u'+a'(&d sig'al a'dd&modula(& (h& carri&r sig'al (o g&( /ac,

    (h& origi'al modula(i'g sig'al.

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    RECEIVERS 

    Function of Radio Receivers

    Intercept the incoming modulated signal

    Select desired signal and reject unwanted signals

    Amplify selected R.F signal

    Detect modulated signal to get back original modulating

    signal

    Amplify modulating frequency signal

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    RECEIVERS 

    Design of Receiver

    4

    he radio recei!er has to be cost effecti!eRequirements"#as to work according to application as for A$

    or F$ signalsune to and amplify desired radio stationFilter out all other stationsDemodulator has to work with all radio stations

    regardless of carrier frequency

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    RECEIVERS 

    Classification of Radio Receivers

     Depending upon application 

    A$ Recei!ers % recei!e broadcast of speech or music from A$

    transmitters which operate on long wa!e& medium wa!e or short wa!e

     bands.

    F$ Recei!ers ' recei!e broadcast programs from F$ transmitters

    which operate in (#F or )#F bands.

    *ommunication Recei!ers % used for reception of telegraph and short

    wa!e telephone signals.

    ele!ision Recei!ers % used to recei!e tele!ision broadcast in (#F or)#F bands.

    Radar Recei!ers ' used to recei!e radio detection and ranging signals.

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    RECEIVERS 

     Depending upon fundamental aspects

    uned Radio Frequency +RF,Recei!ers

    Super%heterodyne Recei!ers

    uned Radio Frequency +RF, Recei!er"

    *omposed of RF amplifiers and detectors.

     -o frequency con!ersion

    It is not often used.

    Difficult to design tunable RF stages.

    Difficult to obtain high gain RF amplifiers

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    RECEIVERS 

    3

    Super%hetrodyne Recei!er 

    Downcon!ert RF signal to lower IF frequency

    $ain amplification takes place at IF

    *ommunication Recei!er 

    Downcon!ert RF signal to two IF frequency

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    RECEIVERS 

    TRF (Tuned Radio frequency) RECEIVER 

    8

     u'&d radio5r&)u&'c6am*li7&r

    d&(&c(orA. #.

    am*li7&r

    Modula(i'g sig'al

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    RECEIVERS 

    RF recei!er includes an

    RF stage a detector stage

     and an audio stage .

    wo or three RF amplifiers are required to filterand amplify the recei!ed signal to a le!el sufficient

    to dri!e the detector stage.

    9

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    RECEIVERS 

    10

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    RECEIVERS 

    RF section +Recei!er front end,

    used to detect the signal

     bandlimit the recei!ed RF signal

    and amplifying the recei!ed RF signal.A$ detector 

    Demodulates the A$ wa!e and con!erts it to the

    original information signal.Audio section

    )sed to amplify the reco!ered signal

    11

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    RECEIVERS 

    Advantages of TRF

    RF recei!ers are simple to design and allow the

     broadcast frequency /0/ 1#2 to 3456 1#2.

    #igh sensti!ity.

    Disadvantages of TRFAt the higher frequency& it produces difficulty in design.

    It has poor audio quality.

    Drawbacks

    Instability

    (ariation in 78

    9oor Selecti!ity

    12

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    RECEIVERS 

    SUER !ETR"D#$E RECEIVER 

     h& shor(comi'gs o5 (h& R# r&c&iv&r ar&ov&rcom& /6 (h& su*&r h&(&rod6'&r&c&iv&r.

    1

    R# am*li7&r

    ocaloscilla(or

    mi&r$#

     am*li7&rd&(&c(or

    A#am*li7&r

    Modula(i'g sig'al

    "a'g&d(u'i'g

    5s

    5o

    $#5o: 5s

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    RECEIVERS 

     Heterodyne ' to mix two frequencies together in a nonlinear

    device or to transmit one frequency to another using

    nonlinear mixing. 

    Also known as  frequency conversion  & high frequency down

    con!erted to low frequency.+IF,A super heterodyne recei!er con!erts all incoming radio

    frequency +RF, signals to a lower frequency known as an

    intermediate frequency +IF,.

    14

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    RECEIVERS 

    1

    RF section

    *onsists of a pre%selector and an amplifier 

    9re%selector is a broad%tuned bandpass filter

    with an adjustable center frequency used to rejectunwanted radio frequency and to reduce the

    noise bandwidth.

    RF amplifier determines the sensiti!ity of the

    recei!er and a predominant factor in determiningthe noise figure for the recei!er.

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    RECEIVERS 

    %i&er'converter section

    *onsists of a radio%frequency oscillator and a mier.

    *hoice of oscillator depends on the stability and

    accuracy desired.$ier is a nonlinear de!ice to con!ert radio

    frequency to intermediate frequencies +i.e.

    heterodyning process,.

    he shape of the en!elope& the bandwidth and theoriginal information contained in the en!elope

    remains unchanged although the carrier and sideband

    frequencies are translated from RF to IF.1

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    RECEIVERS 

    IF section

    *onsists of a series of IF amplifiers and bandpass

    filters to achie!e most of the recei!er gain and

    selecti!ity.he IF is always lower than the RF because it is

    easier and less epensi!e to construct high%gain&

    stable amplifiers for low frequency signals.

    IF amplifiers are also less likely to oscillate than

    their RF counterparts.

    13

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    RECEIVERS 

    FR:;):-*< *=-(:RSI=- in the mier stage is

    identical to the frequency con!ersion in the modulator

    ecept that in the recei!er& the frequencies are down%

    con!erted rather that up%con!erted.

    In the mier& RF signals are combined with the local

    oscillator frequency

    he local oscillator is designed such that its frequency

    of oscillation is always abo!e or below the desired RFcarrier by an amount equal to the IF center frequency.

    herefore the difference of RF and oscillator frequency

    is always equal to the IF frequency

    18

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    RECEIVERS 

    he adjustment for the center frequency of the pre%selector and the

    local oscillator frequency are gang%tune +the two adjustments are tied

    together so that single adjustment will change the center frequency of

    the pre%selector and at the same time change the local oscillator,

    when local oscillator frequency is tuned abo!e the RF ' high side

    injection

    when local oscillator frequency is tuned below the RF ' low side

    injection

    $athematically epressed "

    #igh side injection

    >ow side injection

     

    19

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    RECEIVERS 

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    RECEIVERS 

    COM;AR$%ON

    21

     R# R&c&iv&r

    No 5r&)u&'c6co'v&rsio'

    No $# 5r&)u&'c6

    $'s(a/ili(6 -varia(io' i' cul( (o d&sig'(u'a/l& R# s(ag&s.

    Rar&l6 us&d

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    RECEIVERS 

    COM;AR$%$ON

    22

    %u*&r h&(rod6'&R&c&iv&r#r&)u&'c6

    co'v&rsio'

    Do+'co'v&r( R#sig'al (o lo+&r $#5r&)u&'c6

    No i's(a/ili(6- varia(io' i'

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    RECEIVERS 

    C!ARACTERISTICS "F RADI"

    RECEIVERS

    2

    Sensiti!ity

    Selecti!ity

    Fidelity

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    RECEIVERS 

    Sensitivity

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    Ability to amplify weak signals.$inimum RF signal le!el that can be detected at the input

    to the recei!er and still produce a usable demodulatedinformation signal.

    7roadcast recei!ers? radio recei!ers should ha!e reasonablyhigh sensiti!ity so that it may ha!e good response to thedesired signal

    7ut should not ha!e ecessi!ely high sensiti!ity otherwiseit will pick up all undesired noise signals.

     It is function of recei!er gain and measures in decibels.

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    RECEIVERS 

    2

    Sensiti!ity of a recei!er is epressed in micro!olts of therecei!ed signal.

    ypical sensiti!ity for commercial broadcast%band A$

    recei!er is /6 @(.

    Sensiti!ity of the recei!er depends on "

    3. -oise power present at the input to the recei!er 

    .Recei!er noise figure

    0.7andwidth impro!ement factor of the recei!er 

    he best way to impro!e the sensiti!ity is to

    reduce the noise le!el.

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    RECEIVERS 

    2

      Selecti!ity of radio recei!er is its ability to differentiatedesired signal from unwanted signals.

    Selectivity

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    RECEIVERS 

    0idelit*

    23

    Fidelity is defined as ' a measure of the ability of acommunication system to produce an exact replica of the

    original source information at the output of the receiver.

    Any !ariations in the demodulated signal that are not in the

    original information signal is considered as distortion.Radio recei!er should ha!e high fidelity or accuracy.

    :ample% In an A.$. broadcast the maimum audio

    frequency is / 1#2 hence recei!er with good fidelity must

     produce entire frequency up to /1#2.

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    RECEIVERS 

    28

       HAN? O

    References1