Rectangular microstrip p atch antenna-CST Microwave

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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...

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

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

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.

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

Let us know.

Regards
Lupin

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