Where are equiangular spiral antennas used? (for my thesis)

[ayy2023]

hi all. i want to ask if any of you know what are the areas of equiangular spiral antennas? what are they used for? i know they have circular polarization. some tech guy told me they can be used to find explosive mines from a satellite. do you know other specific usages of equiangular antennas? i want to tell about specific applications of it in the introduction part of my thesis. all the help would be appreciated.

 

[chamonz]

Re: Where are equiangular spiral antennas used? (for my the

ayy2023
as i know, equiangular spiral antenna can be used to detection buried object in ground because of its gain and circular polarization. it is used for GPR (Ground Penetrating Radar) systems.

Added after 5 minutes:

hi all.....

do you know what is flare rate in log-spiral antenna?

what is the connection between flare rate and all of the
spiral's parameter like radiation pattern, polarization, impedance etc?

and what are the effects of flare rate to our log-spiral antenna?

is it correct that the limits in flare rate is 0.2<a<0.45?
if it's true, what is the background of that limitation?

sorry if i have a lot of question because it is for my final paper

thx

 

[ayy2023]

Re: Where are equiangular spiral antennas used? (for my the

hi
by flare rate
i think you mean "a"
which is on equation

r = r0 * e^(aφ)

in the paper of dyson it says they did 40 different spiral antennas all with different parameters
i also did 10 simulations with a=0.7 ; 1 ; 1.3 and 0.3987
the reason why you can think 0.2<a<0.45 is i think when a is at that range
you have an spiral antenna which is between a full turn and one and a half turn.
and at that range you have good pattern.
all my simulations i had different patterns and different VSWR.
some used to be good and some used to be bad in some ways.
it all depends on your needs. i mean which is good or which is bad.
so that's it. have a nice work. and i appreciate if you send your paper when your work is finished

 

[chamonz]

Re: Where are equiangular spiral antennas used? (for my the

but does it true that turn depends by theta? so how turn can be depended with flare rate?
does your 10 simulations not in between a full turn and one and a half turn?
when a=0.7, 1 and 1,5 how many is your turn? not in one half turn?

o ya i've got impedance 230 + j200 ohm, how to reduce that imaginary? and to match it with connector 50 ohm, what matching impedance can be used? must my spiral use balun? like what?
sorry if i have a lot of question

thx

 

[ayy2023]

what is your frequency range? if you're using uwb like 2-18 ghz then you can't match your imaginary impedance. it wont effect much.
turn depends to 2 parameters. first is a "flare rate"
second is beta which is the angle between two equiangular spirals which produce a hand of your spiral antenna. i think you've read Dyson's paper(year 1959)
it says same things as you but it doesnt say you have to limit that way. it says when you do like you say you'll have a good pattern. otherwise he doesnt say what happens. and answer to your question :
if you take r0=1 and a=1,1.3,0.7 both of them don't have a turn or one and a half turn which makes radiation pattern incomplete and broken. my study was to research those effects. you can see what you ask by using hfss yourself. if you need more help mail me from ayy2023@yahoo.com
and i didn't use a balun but i used something instead which made VSWR smaller than 2

 

[chamonz]

Re: Where are equiangular spiral antennas used? (for my the

my frequency range is 1.8 - 6 GHz.
why doesn't your spiral need balun? so how to balance your spiral impedance with coaxial 50 ohm?

 

[ayy2023]

we didn't use a coaxial 50 ohm
like i said we used a transition from coaxial to two wire cable. search for it on ieee as "1:100 balun transformer"
actually you can call it balun.

 

[chamonz]

Re: Where are equiangular spiral antennas used? (for my the

can i see your design, please? because i don't know a transition from coaxial to two wire cable or we can called it "1:100 balun transformer" .

do you know how to create balun or matching impedance
for my log-spiral antenna? i have an antenna with approximately 220 + j200 ohm,
in hfss design, i put lump port in center of spiral, between 2 spiral arms.
i want to match it with coaxial 50 ohm.i don't know too how to create
balun or matching impedance in hfss because i'm new in this software.

 

[heviraf]

Re: Where are equiangular spiral antennas used? (for my the

I used equilateral triangular for my final project to get circular polarizations for quasi zenit satelite.

 

[ayy2023]

Re: Where are equiangular spiral antennas used? (for my the

can i see your design, please? because i don't know a transition from coaxial to two wire cable or we can called it "1:100 balun transformer" .

do you know how to create balun or matching impedance
for my log-spiral antenna? i have an antenna with approximately 220 + j200 ohm,
in hfss design, i put lump port in center of spiral, between 2 spiral arms.
i want to match it with coaxial 50 ohm.i don't know too how to create
balun or matching impedance in hfss because i'm new in this software.

i didn't simulate it with balun. i simulated it as if it was fed with two wires.
it doesn't change radiation pattern but it does change VSWR and i found very very different VSWR's for my simulations.

and i know if you put your lump port in center of your radiation box you have to create a void volume. did you able to manage your simulation and simulate it? i have thesis presentation tomorrow. wish me good luck