# 0.16 Appendix h  (Page 3/4)

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As indicated in [link] , pulses are initiated at intervals of ${T}_{t}$ seconds, and each is scaled by the 4-PAM symbol value. This translates the discrete-time symbol sequence $s\left[i\right]$ (composed of the messages interleaved with the preamble) into a continuous time signal

$s\left(t\right)=\sum _{i}s\left[i\right]\delta \left(t-i{T}_{t}-{ϵ}_{t}\right).$

The actual transmitter symbol period ${T}_{t}$ is required to be within some tolerance of the nominal symbol period $T$ , but the ${B}^{3}$ $I$ $G$ Transmitter allows the introduction of a non-ideal clock that is slightly different from the specified (true)clock at the receiver. The transmitter symbol period clock is assumed to be steady enough that the timing offset ${ϵ}_{t}$ and its period ${T}_{t}$ are effectively time-invariant over the duration of a single frame.

The pulse-shaping filter $P\left(f\right)$ is a square-root raised cosine filter symmetrically truncated to a specified number ofsymbol periods. The rolloff factor $\beta$ of the pulse-shaping filter is fixed within some range and is known at the receiver,though it could take on different values with different transmissions. The pulse-shaped signal is then converted to theRF frequency and passed through the channel. Since the receiver is assumed to employ a sampled IF architecture,the IF frequency completely specifies the behavior of the signal in the frequency domain.While it might seem preferable to build a transmitter that operates at the RF frequency to more accurately model the real transmitter, the number of samples necessary to represent such a signal is large enough that it is rarely desirable.

The channel may be near ideal, i.e. a unit gain multi-symbol delay, or it may have significant intersymbol interference. In addition it can be time-varying, and the ${B}^{3}$ $I$ $G$ code allows two ways to introduce time variation. The first permits specification of the channel impulse response ${\stackrel{\to }{c}}_{1}$ at the start of the transmission and the channel impulse response ${\stackrel{\to }{c}}_{2}$ at the end of the transmission. At any time in between, the actual impulse response moves linearly from ${\stackrel{\to }{c}}_{1}$ to ${\stackrel{\to }{c}}_{2}$ . The second method of introducing time variation is to model the channel variation as a random walk. The variance of therandom walk process can be specified. In either case, the impulse response of the channel is unknownat the receiver, though an upper bound on its delay spread may be available in practice.There are also other disturbances which may be present, including interference from adjacent channels and narrowband interferers.These disturbances can also be controlled using the ${B}^{3}$ $I$ $G$ Transmitter, and they are assumed to be unknown at the receiver.

The achieved intermediate frequency is required to be within some user-specified tolerance of its assigned value.The carrier phase $\theta \left(t\right)$ is unknown to the receiver and may vary over time, albeit slowly, due to phase noise.This means that the phase of the intermediate frequency signal presented to the receiver sampler may also vary.

The frontend of the sampled IF receiver, as shown in [link] , consists of a low noise amplifier, a preselect filter, AGC, mixer for downconversion to IF, and the sampler. The preselect filter partially attenuates adjacentFDM user bands. The automatic gain control is presumed locked and fixed over each transmission, and outputs a signalwhose average power is unity. The free-running sampler frequency ${f}_{s}$ needs to be well above twice the baseband bandwidth of the user of interest to allow proper functioning of thebaseband analog signal interpolator in the DSP timer in the the receiver. However, ${f}_{s}$ need not be twice the highest frequency of the IF signal. This implies that the sampled received signal hasreplicated the spectrum of the user transmission at the output of the front-end analog downconverter lowpass filter to frequencies betweenzero and IF.

#### Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
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