GSM MIMO pcb antenna reposition

[SWRmeter]

I have these antenna modules for GPS and multiband GSM.



The vertical bit is for GSM, but I need to reposition it due to some mechanical constraints of my enclosure.

Q1: Would it be feasible to de-solder from the two feed-points, insert a short gap (about 5mm-10mm), and rewire the feedpoints ?
Q2: Is this likely to completely destroy the antenna characteristics, or maybe just degrade them, or have no effect at all ?
Q3: What would be the best way to do this to minimise any possible degradation ?

Thanks !

 

[SWRmeter]

Cross posting, since the high-tech guys in RF section don't seem to have basic answers.

I have these antenna modules for GPS and multiband GSM.



The vertical bit is for GSM, but I need to reposition it due to some mechanical constraints of my enclosure.

Q1: Would it be feasible to de-solder from the two feed-points, insert a short gap (about 5mm-10mm), and rewire the feedpoints ?
Q2: Is this likely to completely destroy the antenna characteristics, or maybe just degrade them, or have no effect at all ?
Q3: What would be the best way to do this to minimise any possible degradation ?

Thanks !

 

[vfone]

Looks like the slanting feed line is just a 50 ohms transmission line, which (theoretically) its length has no much importance on in the radiation performance of the antenna.
Some problem would be with reducing the ground plane below the antenna (the bottom side triangles). Hopefully this could be no big issue because the antenna will use the ground from the horizontal PCB.
So I think will be no problem to introduce the gap that you want. At least a 5mm one.

 

[SWRmeter]

Looks like the slanting feed line is just a 50 ohms transmission line, which (theoretically) its length has no much importance on in the radiation performance of the antenna.

That is my thinking too. Though I was surprised when I calculated (using an online calculator - track width 1mm, gap width 1mm, FR4 board thickness 1mm) it came to ~73ohm, not 50ohm

Some problem would be with reducing the ground plane below the antenna (the bottom side triangles). Hopefully this could be no big issue because the antenna will use the ground from the horizontal PCB.
So I think will be no problem to introduce the gap that you want. At least a 5mm one.

My other concern is that -- Why is this particular length of transmission line even present ? Is it to make the entire antenna part at proper height above the lower PCB ground plane ?

The total height is ~5.5cm. The operational frequencies range from 700Mhz to 2700Mhz (GSM bands)
This height is exactly lambda/4 of the geometric mean of this freq range. So raising the whole bit by 5mm-10mm would possibly shift the effective band downwards .... IF this whole structure is supposed to be behaving like a monopole.

Or am I overthinking it ??

 

[vfone]

At the first sight looks like a Planar Inverted F Antenna (PIFA), but there is no ground connection to the radiating element.
I think it is a multi-band monopole antenna. The 75 ohms feddline impedance may be fine if this impedance match the antenna input impedance, and the impedance of the RX/TX stages.
A monopole antenna needs a ground plane. If the monopole is lifted from this ground plane will appear side lobes in the radiation pattern. For a cellular GSM antenna this may not be a big issue.