<p>4.1 Array Antennas
We have already introduced array antennas. All elements in the array are ac-
tive, requiring a direction connection to the voltage or current source. The ra-
diation patterns they produce is due to the interference between the different
elements. Furthermore, this interference can also be further influenced by set-
ting the source at each element be out of phase. The drawback to array antennas
is that exciting many elements can lead to an overly complex and possibly ex-
pensive design. In addition, it will be rather sensitive to changes in operating
frequency and thus have low bandwidth</p>
<p>4.2 Yagi Antennas
The Yagi-Uda, or simply the “Yagi,” antenna can be understood as related to
the array antenna. Instead of exciting each separate wire element, the Yagi only
requires one (the driver) to be connect to the voltage or current source. This
makes the Yagi more simple than the array antenna. Additional parasitic wires
are placed very close to the driver and not directly driven. Nonetheless, they
will have induced current. Again, the inteference between these elements creates
the radiation pattern. We can explain their effect by first examining one driven
half wavelength wire and one parasitic wire of equal length placed extremely
close–at 0.04 ¸ away for example. Since this parasitic element is placed so close,
it is excited by the driver element with roughly equally amplitude. The current
on this parasitic element will have equal amplitude but opposite phase of the
driver element. This is almost equivalent to the array antenna scenario of two
elements of opposite phase but equal amplitude producing an endfire pattern
with two main lobes. If we increase the length of the parasitic element, we can
see one lobe on the parasitic element side decrease and the other on the driver
side increase. Therefore this parasitic element is called a “reflector” because it
appears to reflect part of radiation of the driver. If we place a short parasite on
the other side of the driver, the beam becomes enhanced in that direction. Thus
these elements are called the “directors.” Using both the reflector and multiple
directors causes the antenna to form one major beam which is usually very
desirable. This configuration is shown in Figure 5.</p>
<p>The exact size and spacing of
the parasitic elements is a design issue. Modeling the parasitic effects of wires
placed close to each other as in the Yagi antenna and possibly in the array
antenna is difficult to do analytically so use of numerical methods like FD-TD
provides a suitable solution.
4.3 Genetic Algorithm Optimized
Another very popular method to generate antenna design for best gain or greater
bandwidth is to use a genetic algorithm to test the effects of random bends
and curves in the wire. This method can surprisingly converge on very optimal
solutions. Furthermore, the spacing and wire lengths of Yagi antennas can also
be optimized through genetic algorithms.
6</p>
<p>4.2 Yagi Antennas
The Yagi-Uda, or simply the “Yagi,” antenna can be understood as related to
the array antenna. Instead of exciting each separate wire element, the Yagi only
requires one (the driver) to be connect to the voltage or current source. This
makes the Yagi more simple than the array antenna. Additional parasitic wires
are placed very close to the driver and not directly driven. Nonetheless, they
will have induced current. Again, the inteference between these elements creates
the radiation pattern. We can explain their effect by first examining one driven
half wavelength wire and one parasitic wire of equal length placed extremely
close–at 0.04 λ away for example. Since this parasitic element is placed so close,
it is excited by the driver element with roughly equally amplitude. The current
on this parasitic element will have equal amplitude but opposite phase of the
driver element. This is almost equivalent to the array antenna scenario of two
elements of opposite phase but equal amplitude producing an endfire pattern
with two main lobes. If we increase the length of the parasitic element, we can
see one lobe on the parasitic element side decrease and the other on the driver
side increase. Therefore this parasitic element is called a “reflector” because it
appears to reflect part of radiation of the driver. If we place a short parasite on
the other side of the driver, the beam becomes enhanced in that direction. Thus
these elements are called the “directors.” Using both the reflector and multiple
directors causes the antenna to form one major beam which is usually very
desirable. This configuration is shown in Figure 5. The exact size and spacing of
the parasitic elements is a design issue. Modeling the parasitic effects of wires
placed close to each other as in the Yagi antenna and possibly in the array
antenna is difficult to do analytically so use of numerical methods like FD-TD
provides a suitable solution.</p>
<p>lma000, you found that online?</p>
<p>That’s the project Im currently working on ;)</p>
<p>6 Project Details
The final project for 6.013 will require you to implement a wire antenna of your
own design. You may use up to 1 meter of wire which you can cut, bend, and
arrange in any manner. You may choose any operating frequency under 100
GHz. You must document the performance of your antenna in a report that is
a maximum of 5 pages including figures. Possible topics to cover in your report:
• Design choices and how you went about choosing the design for your an-
tenna. Guess and check? Genetic algorithm? Found a paper? Use of outside
research is acceptable both in 6.013 and in real life.</p>
<hr>
<p>sounds cool, what major?</p>
<p>Yeah l0l XD</p>
<p>Im working on the bandwidth stuff at the moment :)</p>
<p>ggggggggggggggggggggggggggggggggggggggg</p>
<p>xfkjyggggggggggggggggggggggggggggggg</p>
<p>lllllllllllllllllllllllllllllllllllllllll</p>
<p>10 until 1900</p>
<p>~~~~~</p>
<p>ooowwwwwwwwwwww</p>
<p>mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm</p>
<p>6 more! :_) (im going to get 1900) ;)</p>
<p>yayyyyyyyyyyyyyyyy</p>
<p>0000001000001001000000011000</p>
<p>l0llll binary? muahh</p>
<p>Ffffffffffffff</p>
<p>Hahahahah!!! 1899!!</p>
<p>muahhhh 1900th reply will be mine</p>
<p>yarrrrrrrrrrrrrrr</p>