Microstrip antenna array

The element spacing must be such that grating lobes will not occur. The formula can be found in any antenna books.

Since individual microstrip antenna radiats very small in θ=90 degree plane, the effect of grating lobe for microstrip array will be smaller than that of most other type antenna arrays. In many cases spacing close to λ shows small effect of grating lobe, but first look at your requirements.

If the elements space is large more than one wavelength , it occurs grating lobe.

If the elements space is small , it may cause mutual coupling .

thanks for replying, i am really new in designing the antenna. the formula i already know. what u mean by grating lobes ? can anyone add me in msn? su_yan_e212@hotmail.com

Grating lobes are the side lobes with the same level of gain as the main lobe, which are not desired by the proposed antenna radiation pattern.

then u know when designing an antenna array, what is feed line width? and how to calculate effective dielectric constant for right and left side impedence? i am using the book: "CAD Microstrip Antenna for wirless applications" and i am using the window application to use it.

You have to define a lot of requirements before select the inter-elements spaicng, at least:

- peak gain
- beamwidth (in both planes)
- radiator element size and coupling
- bandwidth

the grating lobes are not a concern if you don't have to scan the beam away the boresight direction, unless you have an inter-element spacing > 0.9/1.0 Lambda.

Typically the useful range is between 0.6-0.75 Lambda.

But without the above listed information you question is not complete !