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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

Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
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
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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali 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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