# Microstrip patch antenna. Need help

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#### Salving

##### Member level 1
Please, anybody. help me. Give me any idea why increasing the height of the substrate gives better radiation efficiency.

#### chaitu_b99

##### Junior Member level 3
Please, anybody. help me. Give me any idea why increasing the height of the substrate gives better radiation efficiency.

Hello,
Go through the book "Antenna Theory by Balanis", you can good idea of the radiation efficiency wrt height of substrate.

#### Salving

##### Member level 1
I've already read it twice) there is decreasing in efficiency with substrate increasing

#### chaitu_b99

##### Junior Member level 3
You can increase the height to some extent...beyond one point the standing wave will appear, which will result in the decrease in the efficiency.

#### Salving

##### Member level 1
due to the theory efficiency must come down with increasing the height, that is what in Balanis

V

#### volker_muehlhaus

##### Guest
due to the theory efficiency must come down with increasing the height, that is what in Balanis

Where did you find that?

Quote from the Balanis book:

"There are numerous substrates that can be used for the design of microstrip antennas,
and their dielectric constants are usually in the range of 2.2 ≤ Ir ≤ 12. The ones that
are most desirable for good antenna performance are thick substrates whose dielectric
constant is in the lower end of the range because they provide better efficiency, larger
bandwidth, loosely bound fields for radiation into space, but at the expense of larger
element size [38]"

#### Salving

##### Member level 1
That's what i found in Balanis, Antenna Theory - page 763, fig. 14.26
efficiency goes down

V
Points: 2

#### streamlet

##### Full Member level 3
The influence of substrate height on the radiation efficiency should be described by two stages. Stage 1: When the height is small, dielectric loss (and maybe together with conductor loss) dominates. In this stage, the radiation efficiency increases with substrate height, since larger height leads to smaller dielectric loss and stronger radiation. Stage 2: When the height is large, surface-wave loss dominates and this loss increases with substrate height. Thus keeping increasing the substrate height cannot improve the radiation efficiency infinitely.

#### redcrtystalline

##### Junior Member level 1
hi increasing substrate height is equivalent to increasing permittivity and as you know it decrease radation
regards

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