# How to calculate the pattern of microstrip

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if i have get the currents distribution of the microstrip patch surface,how to calculate the pattern of the microstrip antenna? i have read some books,but all the formulars to calculate pattern of the microstrip antenna must be used in spectral domain,is there formular in space domain?
THX

The radiation pattern in the spatial domain can be calculated using the same procedure as for the spectral domain,but the spectral domain Green's function has to be transformed into spatial domain using Hankel transformation (Sommerfeld integrals).

if the microstrip antenna is fed by coxial probe,should the current on the probe to be considered when calculating the pattern of the microstrip antenna?
should the substrate loss tangent be used to compute the microstrip antenna pattern?or where should the substrate loss tangent be used in calculating the parameters of the antenna?

Thanks a lot

In order to get the radiated field pattern, you have to consider the model you are using.Transmission line model would be the easiest, and the intergral equation would be abit rigorous.

for a coaxial fed antenna , you dont consider the current in the coaxial.in any case the antenna can be a transmitting or a recieving antenna.
The excitation fields could could be fields of a plane wave coming from infinity(recieving antenna), or the local fields created by a finite source located within the microstrip structure(transmitting antenna) .
the excitation fields induce surface currents on both sides of the mettallic patch and on the upper side of the ground plane. therefore model the patch as a sheet of current whose value at any point is the algebraic sum of the upper and lower currents.

Antenna designers have found that the most sensitive parameter in microstrip antenna performance estimation is the dielectric constant of the substrate material.this will come more clear when using the transmission line model because the constant will be appearing in the formulas especially when calculating the resonant frequency.

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