A microstrip line influence on atenna they are near to each other

[inass57]

Hi guys,

I was wondering through google learning about rectangular patch antenna arrays, and it's been bugging me how near some lines are to antennas and if they had any influence, here attached is a picture i found on the internet and i circled the part i'm talking about.

Thank you in advance.

 

[FvM]

The feed lines impact the radiation characteristic in any case, not only because they are probably nearer to patches than necessary.

 

[Georgy.Moshkin]

Coupled length is important. In this case small distance area looks much shorter than quarterwave, so coupling would be very weak.
With a thicker substrate it may become a problem, because coupling will go further.
Fig.2 (a) arrangement may be used, although some symmetry is lost:
**broken link removed**
Here is my small article on patch antenna arrays.

 

[Azulykit]

Microstrip lines have significant energy outside the area outside the line and thus can easily interact with nearby objects. This is more pronounced when there are bends and twists in the lines. Unfortunately the drive to make antennas smaller often forces feed lines closer than one would like. Additional layers in a PCB to provide more isolation, stripline vs. microstrip, is often not a good idea for cost and increased complexity. Feedlines can also radiate and induce undesirable disturbances in the array radiation pattern. Arrays with microstrip feeds are notorious for this, particularly if they have been compressed by overall dimension requirements.

 

[Georgy.Moshkin]

Additional layers in a PCB to provide more isolation, stripline vs. microstrip, is often not a good idea for cost and increased complexity.

Azulykit, agreed. I want to add about exceptions from that rule. Last year I did some research on HB-100 X-band motion sensors, and designed sensor that is more cost effective but having greater performance. I used same board area, cut in half: one for aperture coupled patches (same antenna for TX/RX). For high volume production aperture coupled patches may be realized on plastic radome using metallization and air gap between board and radome, so second board for patches is not needed.