Why most of the antenna has an input impedance of 50 ohm

[sugart]

I am currently designing a bowtie antenna using ansoft hfss for my final year project. Can anyone help me to explain why does most of the antenna has an input impedance of 50ohm. Is 50ohm consider as an effective impedance matching?If yes why?

 

[Eugen_E]

It is because the standard coax impedance in RF&MW is 50Ω, and also virtually all test&measurement instruments use this refference impedance, also many devices and circuits are matched to 50Ω.

50Ω was chosen for coax as a tradeoff for both TX and RX operation. By optimizing the coax size, 2 optimum values were obtained:
- approx 37 ohms for maximum power handling;
- aprox 76 ohms for minimum attenuation.
50Ω is a tradeof between the two.

Where only reception is needed, or low power, 75Ω is used - TV, and old analog telecom lines.

 

[santom]

Hi,
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SAntom

 

[Kral]

sugart,
See **broken link removed**. It's an article by Howard Johnson called "Why 50 Ohms?". It appeared in the 9/14/2000 issue of EDN magazine. It has a nice explanation of why 50 Ohms is used for PCB traces as well as coaxial cables.
Regards,
Kral

 

[xulfee]

bcoz coax has 50 ohm resistance,if we use any other impedence instead of 50 ohms,we'll face some reflection

 

[sugart]

tanx mates for all ur answers...it really helped me alot

 

[electronics_kumar]

It is because the standard coax impedance in RF&MW is 50Ω, and also virtually all test&measurement instruments use this refference impedance, also many devices and circuits are matched to 50Ω.

50Ω was chosen for coax as a tradeoff for both TX and RX operation. By optimizing the coax size, 2 optimum values were obtained:
- approx 37 ohms for maximum power handling;
- aprox 76 ohms for minimum attenuation.
50Ω is a tradeof between the two.

Where only reception is needed, or low power, 75Ω is used - TV, and old analog telecom lines.

i really proud of my friend

Added after 1 minutes:

your answer hit the nail ..simply awesome