Optimization of a biband ms antenna on two substrate

[Orey]

Hello,

I am designing a microstrip antenna that will me connected to a PCB (signal, substrate and ground). I have some issue on the gain part. Here are the specifications I am looking for :

1. PCB with a 3 mm microstrip line
2. Biband microstrip antenna (900 MHz - 1800 MHz) on a substrate with: h=1.5 mm er= 2.8 tanD=0.008
3. Positive gain (around 2 dBi) for the two frequencies
4. As small as possible

So far, I have a positive gain at 900 MHz (1 dBi) but I am not satisfied with the gain and the size of the antenna (substrate is 110mm x 75mm). I am not an antenna guy and maybe there is more interesting design to increase the gain and/or reduce the size?

Sorry if the post is messy and if I missed some information.

 

[vfone]

I think a PIFA antenna is a better option for you.

https://www.researchgate.net/figure/a-Design-of-dual-band-PIFA-antenna-for-900-MHz-and-1800-MHz-and-b-S11-parameter-for_fig2_334775140

https://www.rroij.com/open-access/design-of-a-pifa-antenna-with-slots-onground-to-improve-bandwidth.pdf

https://highfrequencyelectronics.com/Archives/Oct13/1310_AntennaDesign.pdf

 

[Orey]

Hello, thank you for your reply.
Unfortunately, I cannot put ground via on the second substrate...

 

[volker@muehlhaus]

gain at 900 MHz (1 dBi) but I am not satisfied with the gain and the size of the antenna (substrate is 110mm x 75mm)

For your antenna type, there is not much you can do to reduce size, except meander routing of the radiator. Even higher substrate permittivity will not have much effect, because most of the field is in air.

For gain, +1dBi is not bad for this almost dipole-like radiation pattern. A lossless dipole would have +2.15dBi, so you are close. Higher gain is only possible if you build a directional antenna, not sure if that would make any sense from a system perspective?