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How to determine which RF connector is suitable for 2.4GHz ?

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Advanced Member level 3
Feb 5, 2002
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RF connectors

I was wondering how to determine which connector is suitable for 2.4GHz application. What determines the suitability of a connector and WHY. Is it
a) the matterial of metal
b) the matterial of insulation
c) the distance between the center and shield
d) date of birth, zodiac sign, country of origin or some charm

How come 2 connectors looking much the same behave so differenetly in micorwave region. Or does it actually make such a big difference. Can a direct solder to PCB and antenna the best solution or we do need a connector.

I think:

a: gilded bras
b: teflon (PTFE, polytetrafluoroethylene) not teflex (polytrifluorchlorethylen) they looks the same, but Q is very different.
c: distance make an impedance, but on all other dimensions a SWR depends.
d: depend on concrete manuf.

- losses depend on quality of connection with a cable and material of cable.


If for wireless use,should care with IP3 which depend on material,plate and solder.

impedance bump

There are two main considertions. Impedance of the connecting process. Variations of diameter will cause reflections. The circumfrence of the outer conductor must be under half of a wavelength to prevent multimoding. This last consideration also applies to cables. Lesser ones are attenuation which is set by the material discussed above. Also the quality of the contact will cause IMD as discussed above.


The answer is not so simple as it could seem.
1) connector or direct sold; it depends if the board has to be removed ( for example for maintenance ) it is a must installa a connector to avoid to use a solder iron for the manitenance people; consider also that soldering a cable directly to the board can lead in losses and pick-up noise and radiations ( for example LO oscillator ) and transfer it to the antennas. If you look at the MIL461 & 462 they are very strict about radiation from the antenna connector ( for the receivers of course ! )
2) type of connector, depends on the size, working frequency and power handling. For the enviromental point of view, take care about the temperature limits and overall the vibration environment; i wold never use a BNC an a flying box.
3) availability on the market and price: if you plan to sell thousand of pieces a cent saved means a lot of money and you care a lot about the final price of the connector; if you sell 10 items the matter is more flexible
4) Intermodulation; if your connector is used on an instrument or a box installed in the same mast as the receiver take care the materials the connector is made; for example avoid Nickel.

These are few instructions to help the choice.

At 2,4 GHz my choce is made as following:
a) Mechanical dimensions
b) Enviroment
c) echnical specifications
d) Price

At this frequency I would suggest or SMA or metter MCX, in any case depends on the specific application

Just a few more thoughts, high SWR is not just caused by the connector itself but at the point where it is soldered to the board. This often gives a substantial impedance step. Secondly high losses often shows up as GOOD SWR, i.e. do not trust perfect match 8O


sharp corners

One classic trick to compensate for the inductance produced by the right angle corner on the center conductor path of connectors that mount on the surface (as opposed to the edge) of a board is to add a shunt capacitance at the corner by making the trace wider. This forms a low pass filter with the inductance. By selecting the proper value of capacitance an filter which has the same impedance as the line will be formed. This is counterproductive if the filter with good imput impedance cuts off lower than your signal frequency.

SMA is my choice. And be sure that the connector to PCB transition is done correctly. A year ago I did a board, the return loss was only 20 dB because the center pin to PCB transistion was not done correctly. I EM simulate all this stuff now.

for 2.4Ghz application,there are several choice:N,TNC,7/16,SMA etc.if you are just a connector custom,you can choose the suitable connector according vendor catalog.for connector eveluation,impedance and vswr and power handle capability are important.In general,for pcb application miniture connector such as SMA is good choice.

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