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ShLi_2270861
Level 1
Level 1

Hi,

Using latest AN91445 RevG. (which is great, BTW) I am designing a PCB antenna.

Reading pages 12-13, I cannot figure out the correct direction in which I can get maximum gain.

In one place the picture shows that maximum gain is transmitted in the direction where the antenna's trace is "open".

In another place there is reference that actually all measurements were taken from the pioneer board - which I have in hand - and actually the actual antenna PCB on the pioneer board is flipped..

So both are using different axis systems and I cannot draw a definite conclusion - is it:

1) maximum gain is obtained in the direction where the antenna's trace is "open".

or

2) maximum gain is obtained in the direction where the antenna's trace is "closed".

I am attaching a "collage" of the relevant references from the AN.

Bottom line - my question is which direction will yield me maximum gain for a given orientation of the antenna.

I'd love to get your feedback on that.

Thanks,

Shachar

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1 Solution

Hi Sachar,

I found a different application note from Cypress about this Antenna (which is old and obsolete now). This has the radiation plot measurements from a test lab, but fails to record the references (as which direction is 0 degrees).  So I could not infer the answer to this question. I have attached the application note here for your information. I also found the patent details for this Antenna, but it fails to mention any thing about the radiation pattern.

So, I discussed with an Antenna expert about this. As per him, the radiation should be minimum near the Antenna tip (where the trace is open) and maximum near the Antenna feed,(where the trace is closed) theoretically, as the current distribution across antenna is maximum at the Antenna feed and zero at the Antenna tip. I found this answer convincing. But to put it across to customers, I need hands on data.

I have taken an action item to verify this practically and update the application note accordingly.

Thanks,

Guha

View solution in original post

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7 Replies
SayaniS_66
Moderator
Moderator
Moderator
10 likes received First like received

Hi,

For the MIFA antenna, the maximum gain is obtained in the direction where the antenna's trace is open. For obtaining maximum gain in that direction,you need to take into consideration other important factors like PCB thickness, antenna tip length, antenna leg length, RF trace width etc.

-Sayani.

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Hi sxsi,

Thanks a lot for your answer.

Can you please advise what do you base your answer on? Any citation of the source could be very helpful?

If this is based on the AN then as I said there are some conflicting figures there.

Or is this a known thing? I want to make sure this answer is solid before I take further actions in my design.

Please advise,

Shachar

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Hi Shachar,

If you look closely at the image that you have attached, the antenna trace used to represent the axis is inverted 180 degree as compared to the PCB antenna on the pioneer board. So, the axis system remains the same even after 180 degree flip. So, according to the AN91445, the maximum gain is obtained in the direction where the antenna's trace is open.

-Sayani.

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Hi Sayani,

"So, the axis system remains the same even after 180 degree flip" - I disagree, let me explain why.

I uploaded again the attached image, with marking A,B,C.. next to different statements/figure.

AN91445_Gain_Conflict_2.png

In sub-figure A "the direction where the antenna's trace is open" is towards plus X.

In sub-figure B "the direction where the antenna's trace is open" is towards minus X.

OK so A and B are inverted.

Now, from sub-figure C it is clear that More radiation is in "the direction where the antenna's trace is open".

But, from sub-figure E and statement F - the measurements are taken based on the pioneer board, deducting that More radiation is in "the OPPOSITE direction where the antenna's trace is open".

So, going back to my original post - Just by reading AN91445 these are conflicting statements, I still think that the conflict holds.

Sayani - I just might be missing something, please advide per above if you can spot my error.

Thanks,

Shachar

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Hi Sachar,

I acknowledge the discrepancy in the representation of Antenna coordinates in the gain plots and apologize for the inconvenience it has caused. Unfortunately, the person who prepared this content is not with Cypress now for me to get first hand clarification on the same. I will try to get this information from any of Cypress' internal documentation and update you at the earliest. Once I get the required information, I will also initiate an update to the application to rectify this confusion.

Thanks,

Guha

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Great, thanks for your answer.

I am looking forward for that update, as soon as you can get it.

Shachar

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Hi Sachar,

I found a different application note from Cypress about this Antenna (which is old and obsolete now). This has the radiation plot measurements from a test lab, but fails to record the references (as which direction is 0 degrees).  So I could not infer the answer to this question. I have attached the application note here for your information. I also found the patent details for this Antenna, but it fails to mention any thing about the radiation pattern.

So, I discussed with an Antenna expert about this. As per him, the radiation should be minimum near the Antenna tip (where the trace is open) and maximum near the Antenna feed,(where the trace is closed) theoretically, as the current distribution across antenna is maximum at the Antenna feed and zero at the Antenna tip. I found this answer convincing. But to put it across to customers, I need hands on data.

I have taken an action item to verify this practically and update the application note accordingly.

Thanks,

Guha

0 Likes