2arms & 4arms spiral antenna

hello everyone;

1-what is the difference between 2arms and 4arms spiral antenna?
2-which is better?
3-how should we supply 4 arms antenna?

One of the advantages of a multiple-arm antenna such as a spiral is that different radiating modes can be created by appropriately phasing the arms with respect to each other. For example, both sum and difference modes can be generated to provide monopole-type and dipole-type patterns. If only the sum mode is required, two arms are sufficient. All spirals will radiate circular polarization.

There are papers in the AP-S literature for spirals with up to 8 arms, and fed from the inside or outside regions. Some type of balun feed can be used to feed the opposing arms, or a more complicated beamforming network may be needed to phase the arms in the desired manner.

Also, the more arms the spiral has, the better the axial ratio (better CP).

do you know any reference for this balun design?

do you have equations for
4-arms log-spiral antenna or more than 2-arms
log-spiral antenna? because i must simulate and analyze that for
the addition for my final project.

thank you for helping me...
regards

Mosko and Corzine have a book on multi-arm spirals. They were at China Lake for many years and have compiled a useful reference. (I only have a paper copy).

hi all
any one know that how we could feed a four arms spiral antenna ?

It is discussed in detail in Corzine and Mosko

Dear SAJ25,

As spirals are pretty wideband, you will have to expect to use a wideband balun. For a two-arm spiral, I've seen people discussing about using a 100:1 coax wideband balun. The paper should be lying around the internet somewhere, do google or see if you could get a copy in this forum. Else, a microstrip version of the wideband balun should suffice.

As for the four-arm spirals, and if you want circular-polarisation, other than using phase-shifters with power-dividers, I can't seem to think how you could feed it. Perhaps other readers could comment on this.

Hope it helps,
Dave

thank heedavid and Azulykit

1. but if you have the Corzine and Mosko book?
2. are you know that if we want to feed a 6 arms spiral for sum and difference pattern what should i do in simulation? how i simulate the port excitation ?
thanks

Your question is not clear (to me.)

I have a paper copy of the book. I would expect that you could run a copy down on the net.

I don'tn recall that it discussed a six arm spiral.

hi Azulykit
i know that you didn't discuss about six arms! but i mean that are you have any information about feeding a six arms spiral or sinuous antenna?

hi any one know how to feed two arm spiral antenna using balus coaxial feed in CST MWS?
there r different types of baluns. (Unbalanced coaxial line, Bazooka balun, λ/4 coaxial balun 1:1, coaxial balun 1:1, ferrite core balun 1:1). which is suite for archimedean spiral arm?

thank you

There are a number of suitable types including tapered coax and microstrips, marchand variants.