This is a Meander Inverted-L type antenna. From my experience you will get very low antenna gain with this kind of antenna in GSM band (aprox. -8dBi, due to high Radiation Resistance).
GSM spec for antenna gain is much harder to meet compared to Bluetooth.
Inverted-F or PIFA are good choices for GSM antenna, but these designs require bigger space than yours.
1. "This is a Meander Inverted-L type antenna. Inverted-F or PIFA are good choices for GSM antenna, but these designs require bigger space than yours."
How about a meande iverted F type antenna then ? Mabe the size can be small. But will the band width be broader ? Or the gain be larger ?
2. "you will get very low antenna gain with this kind of antenna in GSM band (aprox. -8dBi, due to high Radiation Resistance). "
Do U mean that both IFA(iverted F type antenna ) and ILA(Inverted-L type antenna) have poor gain ? Or IFA better than ILA ?
3. "GSM spec for antenna gain is much harder to meet compared to Bluetooth. "
The directivity for GSM antnenna should be better than Bluetooth. So though IFA is good for Bluetooth, it is bad for GSM. Am I right ?
I said that Meander Inverted-L antenna for GSM (900MHz) on PCB has poor gain.
Even a Meander Inverted-F will have low gain at these dimensions and frequency, but this one allow for a better matching compared with Inverted-L.
There are a few factors that affect radiated resistance in a meander type compared with other antenna types: loss in RF conductor resistance, eddy current loss, corona loss, ground resistance loss, etc.
GSM handset antenna shouldn’t be a directive antenna and its pattern shall be close to an omnidirectional pattern (in the limits to pass SAR).
Because GSM is a cellular network (Blootooth isn’t), cannot make too much compromise for antenna gain, because the required radiated power of the handset is very well specified in the specs (e.g. ETSI-TS 151 010).
I don’t know who said that Bluetooth antenna should be directional, even if can be in a point-to-point application.
IFA is good for GSM900, but not Meander type. I arrived to this conclusion after a lot of time spent with this topology.
Probably the best option for GSM900 is PIFA, which anyway is chosen by the majority of phone manufacturers. PIFA has better BW and better SAR behavior compared with standard IFA.
To make the two antennas to resonate independently you need some space between them. Even if you get some second resonance, the gain still will be very low.
A good antenna shall be straight as possible in a line. When start to fold, bend, zigzag, or curve (especially in the high current areas) the gain goes dramatically down. The high currents areas shall keep away from other conductors (or second meander in your case).
To make the two antennas to resonate independently you need some space between them. Even if you get some second resonance, the gain still will be very low.
A good antenna shall be straight as possible in a line. When start to fold, bend, zigzag, or curve (especially in the high current areas) the gain goes dramatically down. The high currents areas shall keep away from other conductors (or second meander in your case).
U said the Gain will be low, then what the major reason for that , the Directivity or the efficency ?
Added after 56 minutes:
Now, I want to feed the tow meander inverted L antennas only though one point.
So the distance between them can not be too far.
Another question:
If I feed the tow antennas just as dipole, i.e. coaxial + connect to one, coaxial - connect to another, and the - on the other side of the coaxial connect to GND.
Does the GND below the antennas still have big impat on the antennas ?
The gain is low because the efficiency is low.
If you change the topology to a dipole there will not be anymore a monopole (inverted L or F are monopoles). Monopoles needs a ground in the nearby to create the mirror image of the element, when the dipole don’t need and don’t like a ground in vicinity. This is just antenna basics.