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# Optimization of a meandered antenna

#### Angelika Krasovec

##### Newbie level 4
Hey folks,

sorry for the question since it may seem to some of you to be very basic. I am an autodidact who is trying to learn about the voodoo of engineering which is antenna design. I am considering this antenna:

Whose full description is available on this link:
Which is a meandered antenna printed on a substrate and fed at the center with a coaxial feed.
Now being a beginner, I was trying to tamper with it and optimize it but I found that there are many "directions" to optimize it.
Has anyone any idea what kind of optimizations are possible for this antenna? or has anyone any articles that discuss this matter?
Thanks in advance, wish me good luck learning this.

Bruce array is a frequency scanning array antenna, which means the array radiation pattern is changing with scanned frequency. The array should scan the beam vs frequency from backward endfire (min frequency), through broadside (mid frequency), to forward endfire (max frequency).
Theoretically the horizontal and vertical segments should be λ/4 at the center of the frequency range.
If you need only broadside pattern (center frequency) you may optimize the element lengths for maximum broadside gain (usually the horizontal segments first).

Bruce array is a frequency scanning array antenna, which means the array radiation pattern is changing with scanned frequency. The array should scan the beam vs frequency from backward endfire (min frequency), through broadside (mid frequency), to forward endfire (max frequency).
Theoretically the horizontal and vertical segments should be λ/4 at the center of the frequency range.
If you need only broadside pattern (center frequency) you may optimize the element lengths for maximum broadside gain (usually the horizontal segments first).
I would like to do an analytic study first. So my question is: can I approximate this antenna model that I have for the most part as an array of dipoles (since the horizontal parts do not contribute to the radiation anyway)?

Yes, I think you can approximate this antenna with an array of vertical dipoles.
When radiating broadside, the EM source should produce in the active elements currents which are in phase with each other.

Yes, I think you can approximate this antenna with an array of vertical dipoles.
When radiating broadside, the EM source should produce in the active elements currents which are in phase with each other.
Thank you so much .
I will put myself to work now. Hopefully, I will not bother you again.

Yes, I think you can approximate this antenna with an array of vertical dipoles.
When radiating broadside, the EM source should produce in the active elements currents which are in phase with each other.
I have one question that is yet to be answered:
Normally the groundplane has fixed dimensions (I am interested in the length especially). And as I am giving the simulator different numbers of radiating elements (in the example it is 15 elements, but I am trying smaller numbers), I have noticed that the right and left sides are left empty with only the substrate and groundplane being present there as shown in a photoshop modified image I made of the antenna:

My question is:
should I also "trim" the excess groundplane and substrate? or do they play no role in influencing the radiation pattern?
is there generally a rule of the ratio that has to be there between, from one side the groundplane and substrate and from the other side the printed antenna?
Thanks once again and sorry for bothering you.

The original Bruce antenna patented in 1931 (which was a wire antenna), uses a wire reflector with the same shape and dimensions as the active antenna.

So your printed variant should have a ground plane at least the same dimnesnions as the antenna, but a bit bigger I think would be better.
Both, substrate height and ground dimmnension would affect the radiation pattern (the height maybe more), and the optimiziation of their ratio using an EM simulator could give the best performance results (better than some empirical equations).

Thanks a bunch for your input. I still have one issue lingering in the back of my head: is there any way to calculate ${\epsilon\}_{r,effective}$ for this antenna? I mean can there be a derived formula? since I noticed that for the patch antenna there is actually one approximation formula. Can that be done here too? Days are gone and I couldn't find a relevant information on the subject.
Thanks again