Dipole multiband antenna using two ceramic chip monopole antennas

[podoljano]

Hi guys,
I got a very small GSM based product, which implies a very small ground plane.
Experience and literature has proven that having a small ground plane is very bad for monopole antenna efficiency.

Would it be possible to make a dipole antenna using monopole chip antenna elements?
This would in theory be independent of the ground plane. And by placing a balun between the antennas I could get a proper 50 ohm feed.

An antenna example could be: https://www.soselectronic.cz/a_info/resource/c/2J/2JE03.pdf

Any toughs?

 

[FvM]

The total antenna size won't be increased and and related performance limitations not eliminated by using two instead of one chip antenna. The directional characteristic will be somewhat different. The behaviour will be also different if cables are connected and changing the antenna characteristic.

A "monopole" with small ground plane is acting as (asymmetrical) dipole anyway. What you have to do in any case is to match the actual antenna impedance to your GSM transceiver.

 

[podoljano]

A "monopole" with small ground plane is acting as (asymmetrical) dipole anyway. What you have to do in any case is to match the actual antenna impedance to your GSM transceiver.

Wouldn't a dipole antenna be a good way to remove the asymmetry, and therefore increase the antenna efficiency?

For clarity i have attached a drawing of the concept:

 

[FvM]

Asymmetry doesn't per se involve lower efficiency. But the directional characteristic will be different. Theoretically, a symmetrical dipole doesn't radiate via the attached ground plane, this can be an advantage regarding ground plane hand effect.

On the other hand, as the dipole uses only a part of the total instrument volume, a smaller bandwidth must be expected. And the strongest hand effect will be probably observed near the resonant chip antennas.

 

[Borber]

RF block diagram is like a Lego. But if you can not check matching between each element and power losses end result can be disaster. Not to mention change in radiation patterns which can become directional.

 

[E Kafeman]

For a limited antenna design volume, you have the choice:
1. A short monopole, reflected in ground.
2. Two half as long dipole elements, low ground reflection.

Alt 1. will in any case result in biggest effective antenna size. If ground length is long enough can alt 1 be twice as big antenna compared to alt 2.

 

[volker@muehlhaus]

Wouldn't a dipole antenna be a good way to remove the asymmetry

The required ground plane from the appnote is parallel to the antenna. That ground plane orientation and location is different from the line of symmetry (=virtual ground) in your sketch with two antennas.