Rectangular microstrip p atch antenna-CST Microwave

[sas11]

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Hi all!

I need to design a wideband rectangular microstrip p atch antenna.
The required resonance frequency is approximately 900 MHz,
the substrate is Air (Er=1).
The simulation tool is CST-microwave.
Attached please find my first designed model.
Any comment will be wellcome,
and any relevant essay as well .

regards...

 

[loucy]

is it practical to have a patch attenna without a substrate? (air subrate)?

 

[eirp]

Hi, sas11!

My few thoughts here:

- substrate seems quite thick
look at radiation patter at fundamental mode ~400MHz (not the 900MHz, it's second mode!!) , it's slightly assymetric (maximum not in the antenna's normal direction).
I guess, pattern degradation is thus caused by unwanted surface waves excitation.

added: ground plane is also very thick, why?

- simulation frequency
for TEM/QTEM feeders (with no cut-off frequency), simulation from f=0 speeds up calculation time-due to the shape of time excitation signal which becames gaussian pulse. for TE/TM you should set fmin>fcut-off, then it's excited by "sinus*gaussian" taking always more time to pass. It comes from the fourier properties of band-limited signals.

added: for high Q structures like this, increase accuracy (energy stop limit) in solver setting to say -50dB

- boundaries
at X, Y boun. there should be rather "open add space" due to accounting intensive fringing fields. It will also put S11 closer to measurement, it approaches real-life problem more accurately. At Zmin you can put open only because of p atch radiation principle. With open at Zmin you'll simulate real life antenna with finite ground. Of course you need to add groundplane PEC brick there.

- symmetry planes
for calculating only fundamental mode is OK but some higher modes will (thanks to this symmetry) not be accounted!!

Hope it helps..

eirp

 

[jjantenna]

is it practical to have a fix attenna without a substrate? (air subrate)?

It's practical to have a fix antenna without a substrate. You can use Teflon post to support the antenna, or you can even use Expanded Polystyrene(EPS) to support it. Using air as substrate can basically improve the bandwidth performance.

 

[Lupin]

How much is the required bandwidth?
Is it your one requirement?

Let us know.

Regards
Lupin