very small sub 1GHz patch antenna

[AndreyG]

I started seeing designs of very small sub 1GHz patch antenna.

As shown on picture below:


Curious what is the structure of such antenna? The four arms on top plane – are they connected to central conductor or GND plane? What is resulting polarization - linear or circularly polarized?

 

[FvM]

Without seeing the full structure, you can at best guess about the antenna characteristic. Circular would be reasonable for 900 MHz RFID, but there must be a phase shifter on the bottom side then.

 

[AndreyG]

... but there must be a phase shifter on the bottom side then.

Most likely but not necessarily. For example patch with truncated corners does not use phase shifter yet generates CP.

It's only recently I started seeing this structure, curious how it works.
I hoped somebody in this forum has experience with this design and share it with us.

 

[FvM]

Most likely but not necessarily. For example patch with truncated corners does not use phase shifter yet generates CP.

It's not the truncate corners, it's the asymmetrical feed position that makes the 90° phase shift required for circular polarisation. Something similar will be used in the photo.

 

[Bety]

RFID antenna ANSOFT HFSS:
I aim to develop a conception where I will integrate a RFID tag; and I can not simulate the antenna + chip (dipole antenna + chip) on HFSS, please can you explain me how can I simulate a chip on HFSS ??? can you give me some instructions or tutorial for my first simulation in this solver.
Thank you in advance.

 

[sudokubk38]

I remember not clairly that we can define a chip impedance and the gamma in HFSS (located in output variables of result table) by input the equations. And you can simulate again.
Best regards.

 

[AndreyG]

So nobody knows what kind of antennas shown on that picture? They sure look good.