Hello all. Hope all is well!

Did you ever see a antenna feed port going towards the coax line and at the same time the feedport being attached to ground?

Ty for the replies!

 

No, did you?

 

Hello all. Hope all is well!

Did you ever see a antenna feed port going towards the coax line and at the same time the feedport being attached to ground?

Ty for the replies!

Show us a picture(s). There are many RF matching systems with grounded elements at several GHz that make these stubs look like grounds to the uninitiated with microwave design principles.

Microwave slot antenna.


https://physicsopenlab.org/2021/01/21/light-diffraction-and-babinet-principle/

Slot antennas use the Babinet Principle for Microwave range RF.

In physics, Babinet’s principle states that the diffraction pattern generated by an opaque body is identical to that produced by a hole of the same size and shape except for the overall intensity of the light transmitted in the forward direction. It was formulated in the 1800s by the French physicist Jacques Babinet.

The explanation is relatively simple. Suppose that B is the original diffracting body and B’ is its complement, i.e. a transparent body where B is opaque and opaque where B is transparent. The sum of the radiation patterns caused by B and B’ must be equal to the radiation pattern of the unobstructed beam. In the points where the undisturbed beam would not have reached the screen the radiation patterns produced by B and B’ must therefore be opposite in phase, but equal in amplitude.

 

Show us a picture(s). There are many RF matching systems with grounded elements at several GHz that make these stubs look like grounds to the uninitiated with microwave design principles.

Microwave slot antenna.

View attachment 347337View attachment 347338
https://physicsopenlab.org/2021/01/21/light-diffraction-and-babinet-principle/

Slot antennas use the Babinet Principle for Microwave range RF.

Below, in the black and white pic, you can see the pads of the antenna on the left and right part of the bottom of the antenna . The leftmost pad is the WiFi/DSRC feed and the rightmost pad is the GPS/GLONASS feed.

The green colored pic shows the recommended PCB layout. So far so good.

Here is the question.

If we were to solder this antenna onto that PCB with that recommended PCB layout, it seems highly likely that the GPS/GLONASS pad of the antenna will contact both the pads labeled 1 and 3 ( shown in the pcb picture inside yellow boxes ) simultaneously.

This would be bad, I think, because Pad 3 is labeled as ground and it definitely seems to be connected to the larger ground plane that extends towards the right.
The GPS/GLONASS pad of the antenna will be soldered to both the Feed GPS ( Pad 1 ) and GROUND ( Pad 3 ) !!

Is the datasheet incorrect or is there more to this assembly?
https://www.digikey.lv/htmldatasheets/production/3646046/0/0/1/w3095.pdf

 

No, did you?

Yes. Please see the pics that I used to reply above.

 

Yes. Please see the pics that I used to reply above.

You are thinking DC shorts. Those stubs are not shorted at GHz RF. Connections per the datasheet have been validated to work at the frequency of interest.

 

You are thinking DC shorts. Those stubs are not shorted at GHz RF. Connections per the datasheet have been validated to work at the frequency of interest.

Ty. Is this because at GHz frequencies, the physical length of the pad wrt to the wavelength of the signal affects how it behaves?

Is this because the electrical length of the pad becomes a significant fraction of the wavelength, and its gonna act like a capacitor, inductor or a resonant open or short?