Signal Conditioning

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should I use Impedance Matching?

If a transmission line has a length greater than about 10% of a wavelength, then it will affect the circuit.

My antenna L is 0.03125m + .7m of more wire ( I may not have that much wire ) from the transmitters line. Than

L = 0.0315m + .7m = 0.7315m
λ = 0.125m

L is not >> λ so there is no transmission line problems.
Does this mean there is no Impedance Matching problems aswell?
Is Impedance Matching part of transmission line affect ?

I have a 2.4GHz transmitter device that has a built in impedance of 50Ω.
I am planning on wiring it up to a monopole antenna with a λ = 0.125m and L = 0.03125m. Do I have to some how remove the built in impedance of 50Ω with a Series Inductor ?

Also do you have to factor in Impedance Matching for a receiving antenna circuit?

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Impedance matching is always an important part in your system that will affect the operation of your circuit.  Mismatched impedances will cause signal reflections which could damage equipment, loss of output power, oscillations in your signal, etc.  To match impedances, you want to have your source, load, and characteristic impedance of your cable all be the same.  This DevZone is talking about RF Switches, but the first half is very insightful to impedance matching in RF systems. 


If you need to change the impedance, there are tutorials for doing so with series or parallel resistors, or other methods to change impedance of your load. 


You should always consider impedance matching to minimize signal reflections, eliminate loss of power due to reflections, and prevent possible damage to your system. 

Kyle A.
National Instruments
Senior Applications Engineer
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