Hi all,

For a product which will communicate over NB-IoT at around 800MHz we are currently busy with the design of the PCB. For best performance we would like to have a ground plane of at least 1/4 of the length wave which corresponds to roughly 90mm. Our PCB is due to mechanical constraints maximum 80mm.
Is there a way to determine roughly the performancy penalty we will receive for this smaller ground plane?
Also the PCB will have a right angle SMA connector which will connect to the antenna. Due to the fact this SMA connector is connected to the ground plane and is extending the physical length of the pcb. Could we count this SMA connector as part of the PCB and so as part of the ground plane?

Thanks for thinking with us.

 

Dielectric materials have an effect on the electrical velocity in the conductor they surround. So a dielectric coating might be the same as a longer antenna. At least for HAM radio antennas, insulated wire antennas often need to be a bit shorter than bare wire ones. So it might be the trick the TS is hoping for.

 

Yes, the Connector will increase the Ground-Plane length, but, at the same time,
the Main-Radiator will be shortened by the same amount.

Having the Main-Radiator and the Ground-Plane at a 90-degree-angle will result in
a lower than ideal Antenna-Impedance,
( it will be closer to ~30-Ohms, instead of the desired ~50-Ohms ).
With virtually zero Coaxial-Cable to take into consideration,
this may have very little effect, ( maybe ~10% loss ), but it "could" overload the Transmitter-Amplifier.

A 1/4-Wave "Vertical-Radiator" will have a definitely predictable radiation pattern that
is largely affected by the angle between the Main-Radiator and the Ground-Plane.
This matters when You start taking into consideration the Main-Coverage-Area that You are anticipating.
A Dipole-Antenna, may have a wider, more consistent, and larger, Coverage-Area,
but will have a smaller maximum-distance of useful coverage,
when compared to a 1/4-Wave-Vertical-Radiator.
A 1/4-Wave-Vertical-Radiator WILL HAVE dead-spots in certain directions,
possibly very large areas,
this can be a beneficial thing,
or a disastrous performance detriment.

A drawing of your proposed Transceiver,
where it will normally be mounted or placed,
and the desired coverage-area away from that general point or position,
would be highly desirable BEFORE settling on a final Antenna design.

If your device will be used for direct, "line-of-sight", "point-to-point", communications,
a highly-directional-Antenna-design can easily 10X the useful connection distance attainable.

If You want help with this, I can supply You with plenty-more Documents/Pictures,
that will show how all this can be done to your Project's advantage,
rather than possibly creating a big disappointment.
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