Broaband Microstrip Antenna for 3G mobile

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bguk80

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Hi Everyone

I am looking for some help to design a broadband antenna. I designed an E shaped antenna with 40% bandwidth using air substrate.. I am trying to design a miniturized broadband microstrip antenna from 1.9 GHz to 2.2-2.3 GHz using stacked patches or single layer E-shape. I am also using a specific material Duroid with Er=2.5 h=1.525.

I will be glad for any help

Thanks
 


well, how much miniaturization are you looking for? and what thickness can you use? i can help you more if you tell more about specifications. even pattern charasteristics is mportant.

rgrds, marti
 

Hi Marti

The dimension of the patch should be around 40mm for width and lenght

The thickness h=1.524 but if using stacked patches can get up to 3*1.524 when using three layer.
U see i have to use Duroid with Er = 2.5 and h=1.524.

But any paper for any broadband design could be useful

cheers
 


well, by thickness limitations, i meant the overall thickness you can have(with airgaps). your p@tche's size is now around 6cm? if you want to have such a broud-band functionality, you should use about 15mm airgap, so the board er is not critical. and bandwidth, what criterion do you mean for band-width? VSWR<2?, VSWR<1.5? or else? u wanna use it in handset or BTS? and patter, you didnt tell me abot pattern specifications. and, finally, what gain do you need?

marti
 

There will be no air gaps in the design. I need overall bandwidth with respect to the centre freguency around 13-14%.
return loss <-10 dB

I need the antenna to cover the frequency spectrum of UMTS from 1.825 to 2.1 - 2.2 GHz

VSWR<2

regards
 

bguk80 said:
There will be no air gaps in the design. I need overall bandwidth with respect to the centre freguency around 13-14%.
return loss <-10 dB

I need the antenna to cover the frequency spectrum of UMTS from 1.825 to 2.1 - 2.2 GHz

VSWR<2

regards
Click to expand...

well, did you get a 40% bandwidth with an E-shape p@tch on a 1.5mm substrait with no airgap? i should tell that this is impossible. you need a minimum aigap of 10mm for 15%BW.

marti
 

No

I achieved 40% bandwidth with an air gap of 14mm and antenna dimensions 105mm,40mm

The next step is to minimize the antenna, and instead of air substrate to use a supplied substrate with the specification mentioned before. The bandwidth target will be 14% for the new antenna.
 

if you easy replace air gap with Er+2.5 material you'll stil will have 6 mm thikness.(theory)
Seems you can not achive requested results with only replasing of substrate environment. What for my experience, i don't khow p@tch style antennas as you asking about.
 


dear bguk,
for such a wide-band operation, you have to use a low permittivity sub. you may use foam or airgap. noway to use a relative permittivity of 2.5, thickness of 1.5mm, and 15% BW. you can still use your substrate, but you should insert an airgap between the sub and the GP. and about dimentiones, again you shoul specify the gain and pattern charasteristics. i know methods to miniaturize this p@tch to about 28mmx28mm with airgap; but you should tell about gain and pattern specifications. and, these methods are often patented or patent pending, is it a commercial study, or just an educational one?

rgrds, marti
 

It is for my dissertation. Actually i met my supervisor today , this antenna has been designed by Nokia and operates from 1.95 GHz to 2.1 GHz. The dimensions of the antenna have to be reduced to minimum so it can be fitted to the handset. The bandwidth has to be achieved without air gaps. He told me their is a way using stached microstrip patches, coupling the patch, meander patches or using multiple dielectrics but not Er=1 (air)

Also for the gain and the pattern characteristic i dont have a good idea but it is something i have to consider during the design procedure. Anyway i ll keep u in mind for any help .

cheers
 


well, if you want it as a handset antenna, i should tell you that in handset antennas, the BW criterin is defined for S11<-5dB or less, instead of -15dB or -10dB. these antennas are often active (amplifying by a RF circuit) and printed on high permittivity subs to miniaturization. more often they are meander monopol, but complex p@tches such as PIFA is used too. i suggest you to use an apperture coupled stacked p@tch, with a near resonant aperture. bytheway, this high BW ishard to achieve. please specify more the thickness limitations (is it forexample 3mm, or less?).

marti
 


please go through this book ...
[b/]Compact and Broadband microstrip antennas[/b] by KIN-LU WONG
John Wiley publication
ISBN 0-471-22111-2

this book will certainly help you in your design

8)
 

most handset antena uses higher permitivity and multiple narrowband matches by shorting pins.

air and foam is not really suitable for handset. more used in base station. and no saving of size using air or foam
 

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