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On the transmitter side, the digital I and Q data – which are already processed by a digital-to-analog converter, filtered and amplified – are up-converted by quadrature mixers to the carrier frequency of interest. After combining, the signal is again filtered to contain the spectral content of the signal in the required bandwidth stipulated by the emission mask. After that, it is applied to the power amplifier and transmitted over the air with an antenna (Figure 2).

Now let's get into the details for each of the blocks in the transmitter and receiver.

Antennas

Antennas are coupling circuits to space that radiate or receive information-bearing electromagnetic waves. In a receiving antenna, the EM wave impinging on the surface produces currents, which in a 50-ohm system are applied to an LNA for amplification and subsequent processing. On the transmitter side, the surface current density on the antenna produces a magnetic field around the antenna. If the current density is time-varying, an accompanying electric field is also produced; propagation takes place in a direction perpendicular to both the electric and magnetic fields. The total radiated power is given by a surface integral of the Poynting vector over any surrounding surface. The value of resistance that would dissipate this amount of power is called the radiation resistance, which is caused by the power radiated. The total resistance of the antenna comprises radiation resistance and resistance due to power loss. For high efficiency, the value of radiation resistance should be large.

Filters

Filters remove the effect of broadband noise and thereby increase the SNR of a desired signal. They are also used to select channels in multiple transmission environments and to remove image frequencies in broadband services and other out-of-band interference. In the transmitter, digital pulse-shaping filters are used for efficient utilization of the RF spectrum and externally to suppress RF splatter in adjacent channels.

Amplifiers

The RF signal at a receiver’s antenna is very small in magnitude. The IEEE 802.15.4 standard defines a minimum signal of -85 dBm = 3.16 pW, whose voltage in a 50-ohm system is 12.6 µV. At the detector, the typical signal requirement is at 1 mVp-p for detection and decoding of digital waveforms. To achieve this, low-noise amplifiers are used in the front end to amplify the signal up to the detection stage. The gain required in the receiver is usually between 60-90 dB – very high. Therefore, to avoid oscillations, this gain is distributed over different stages of the radio-frequency integrated circuit.

On the transmitter side, power amplifiers (PAs) are used to transmit the EM wave. PAs come in various classes and can be linear and nonlinear. They usually employ matching circuits between the output and the load. In practice, the output impedance of the active device is complex and varies with load; thus nonlinear complex impedance must be matched to a linear load. More often, the antenna impedance may be complex and vary with both the position of the transceiver and surrounding objects. This makes PA input and output matching a nontrivial task. In practice, a technique called load pull is applied to a matching circuit design. In this test, the output power is measured and plotted as a function of the complex impedance load seen by the transistor output stage. A tuner can accurately vary the output impedance while a power meter measures the power, keeping it constant. The impedance gives a contour on the Smith chart. As the output impedance varies, this changes the input impedance of the transistor, thus requiring the use of a second tuner such that the impedance seen by the generator remains constant.

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, Senior project guide to texas instruments components. OpenStax CNX. Feb 12, 2013 Download for free at http://cnx.org/content/col11449/1.3
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