Low-side injection results in symmetry in the translated message
spectrum about
$\pm {f}_{c}$ on each of the positive and negative half-axes.
High-side injection separates the undesired images
further from the lower frequency portion (which will ultimatelybe retained to reconstruct the message). This
eases the requirements on the bandpass filter.
Both high-side and low-side injection can place
frequency interferers in undesirable places.This highlights the need for adequate out-of-band rejection
by a bandpass filter before downconversion to IF.
Consider the system described in
[link] .
The message
$w\left(t\right)$ has a bandwidth of 22kHz
and a magnitude spectrum as shown.The message is upconverted by a mixer with carrier frequency
${f}_{c}$ .
The channel adds an interferer
$n$ .
The received signal
$r$ is downconverted to the IF signal
$x\left(t\right)$ by a mixer with frequency
${f}_{r}$ .
With
$n\left(t\right)=0$ ,
${f}_{r}=36$ kHz, and
${f}_{c}=83$ kHz,
indicate all frequency ranges (i)-(x) that include any partof the IF passband signal
$x\left(t\right)$ .
(i) 0-20 kHz,(ii) 20-40 kHz,
(iii) 40-60 kHz,(iv) 60-80 kHz,
(v) 80-100 kHz,(vi) 100-120 kHz,
(vii) 120-140 kHz,(viii) 140-160 kHz,
(ix) 160-180 kHz,(x) 180-200 kHz
With
${f}_{r}=36$ kHz and
${f}_{c}=83$ kHz,
indicate all frequency ranges (i)-(x) that include anyfrequency that causes a narrowband interferer
$n$ to appear
in the nonzero portions of the magnitude spectrum ofthe IF passband signal
$x\left(t\right)$ .
With
${f}_{r}=84$ kHz and
${f}_{c}=62$ kHZ,
indicate every range (i)-(x) that includes anyfrequency that causes a narrowband interferer
$n$ to appear
in the nonzero portions of the magnitude spectrum ofthe IF passband signal
$x\left(t\right)$ .
A transmitter operates as a standard AM with suppressed carrier transmitter
(as in
AM.m ). Create a
demodulation routine that operates in two steps:by mixing with a cosine of frequency
$3{f}_{c}/4$ and subsequently mixing with a cosine of
frequency
${f}_{c}/4$ . Where must pass/reject
filters be placed in orderto ensure reconstruction of the message?
Let
${f}_{c}=2000$ .
Consider the schematic shown in
[link] with the absolute bandwidth of the baseband signal
${x}_{1}$ of 4 kHz,
${f}_{1}=28$ kHz,
${f}_{2}=20$ kHz, and
${f}_{3}=26$ kHz.
What is the absolute bandwidth of
${x}_{2}\left(t\right)$ ?
What is the absolute bandwidth of
${x}_{3}\left(t\right)$ ?
What is the absolute bandwidth of
${x}_{4}\left(t\right)$ ?
What is the maximum frequency in
${x}_{2}\left(t\right)$ ?
What is the maximum frequency in
${x}_{3}\left(t\right)$ ?
Using your M
atlab code from Exercise
[link] , investigate
the effect of a sinusoidal interference:
at frequency
$\frac{{f}_{c}}{6}$ ,
at frequency
$\frac{{f}_{c}}{3}$ ,
at frequency
$3{f}_{c}$ .
Consider the PAM communication system
in
[link] .
The input
${x}_{1}\left(t\right)$ has a triangular baseband magnitude spectrum.
The frequency specifications are
${f}_{1}=100$ kHz,
${f}_{2}=1720$ kHz,
${f}_{3}=1940$ kHz,
${f}_{4}=1580$ kHz,
${f}_{5}=1720$ kHz,
${f}_{6}=1880$ kHz,
and
${f}_{7}=1300$ kHz.
Draw the magnitude spectrum
$|{X}_{5}\left(f\right)|$ between
$\pm 3000$ kHz.
Be certain to give specific values of frequency andmagnitude at all breakpoints and local maxima.
Specify values of
${f}_{8}$ and
${f}_{9}$ for which the system
can recover the original message without corruption with
$M=2$ .
This problem asks you to build a receiver from a limited
number of components.The parts available are:
two product modulators
with input
$u$ and output
$y$ related
by
and carrier frequencies
${f}_{c}$ of 12 MHz and 50 MHz
two linear bandpass filters with ideal rectangular magnitude spectrum
of gain one between
$-{f}_{U}$ and
$-{f}_{L}$ and between
${f}_{L}$ and
${f}_{U}$ and zero elsewhere with (
${f}_{L}$ ,
${f}_{U}$ ) of
(12MHz, 32MHz) and (35MHz, 50MHz).
two impulse samplers with input
$u$ and output
$y$ related by
The spectrum of the received signal is illustrated
in
[link] .
The desired baseband output of the receivershould be a scaled version of the triangular portion
centered at zero frequency with no other signalsin the range between
$-8$ and 8 MHz.
Using no more than four parts from the 10 available,build a receiver that produces the desired baseband signal.
Draw its block diagram.Sketch the magnitude spectrum of the output of each part
in the receiver.
For further reading
A friendly and readable introduction to analog transmission systems can be found in
P. J. Nahin,
On the Science of Radio , AIP Press, 1996.
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest.
Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.?
How this robot is carried to required site of body cell.?
what will be the carrier material and how can be detected that correct delivery of drug is done
Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
how did you get the value of 2000N.What calculations are needed to arrive at it