What is use of SMA connector

what is use of SMA connector?
I saw most of the RF circuit and signal related circuit having such connector's.
We also can use wire or not?

>> what is use of SMA connector?
Small, low cost RF connector good to 18GHz used in low power applications.

>> We also can use wire or not?
Please rephrase question.

means
instead of SMA connector can use wire?

You can use a wire instead of a SMA conector if you understand the performance and properties of your circuits. Usually, the SMA is for high frequency usage and for a repeatable constant-impedance transition. If using a wire instead of a SMA connector does not influence your circuit operation, use the wire.

Twisted pair of wires if dimension of wire and insulation can have about 50ohms impedance:
**broken link removed**

If you have this in mind? It may work for few cm of distance up to 1GHz if all electronics is in metal box.

no actually i don't know difference of this. What parameter actually affect i don't know.

SMA is a coaxial connector. It has two conductors: signal and ground.
https://en.wikipedia.org/wiki/Coaxial_cable

What is the application where you want to replace coax connector with a "wire"? Picture?

Application is RF itself.But i saw maximum of people using same. so i confuse.

just a suggestion,

the use SMA/SMB is all to be about screening,insertion loss of the connector,size of the connector, impedance of the connector
availability of the connector,ease of termination, (no special tools required to make off)
miniature RF cables are availability for these connectors, like rigid 50R (100% screened) and also semi-rigid
and flexible cables like RG174U,
if one is working with RF, you may want to test your design its a lot
better to use a RF connector than soldered wires because the termination match can not be all that repeatable especial at high frequencies.
The mind boodles when you think of the number of RF connectors there
are available to day, companies with lots of cash just go out and design
their own connectors, why???, miniaturization, but there don't seem to
be any standard ones. excepting sma,smb,smc,bnc,tnc,snc,n, ect..

Hi,
To help ease your confusion I would say that if your application is RF based, use of coax cables and SMA connectors will be a better than just using wires.
To put it in simple form, the signal which flows in your PCB trace needs some required impedance requirements for it to flow smoothly. The SMA connectors will satisfy that requirement. As suggested in the above post, you have many options in the market for connectors and might be confusing. I think SMA connectors will suit your application if the Maximum frequency content in your required application is within 18 GHz.