# How quarter wave transformer is used for impedance matching.

How quarter wave transformer is used for impedance matching.

In all applications of transmission line, it is required that the load be matched to line, Which requires tuning out the unwanted load reactance and the transformation of resulting impedance to the required value especially at high frequencies. The impedance of the quarter line depends on load impedance and characteristics impedance as shown

When the length S is exactly quarter wavelength line then the line is lossless. If the Zo is varied, the impedance seen at the input to the λ/4 transformer will also vary accordingly, so that load may be matched to characteristic impedance of the main line. This is similar to varying turns ratio of a transformer to obtain the required value of input impedance to match the load impedance. Quarter wave transformer works as filter to prevent unwanted frequencies from reaching the load such as antenna. The name transformer is given to quarter wavelength transmission line since it behaves as a transformer depending upon the value of ZL.

If ZL = Zo then it acts as 1 : 1 transformer.

If ZL >Zo then it acts as a Step down transformer

If ZL <Zo then it acts as a Step up transformer

## Related questions

Description : A load of 200 ohm is used to match 300 ohm transmission line to achieve SWR=1. Find out the required characteristic impedance of a quarter of a quarter wave transformer connected directly to the load.

Description : List and explain the properties of quarter wave transformer.

Answer : Properties of quarter wave transformer: 1. Impedance transfomation: it provides impedance transformation upto the highest frequencies and is compatible with transmission line. 2. Impedance inversion: if ZL is ... or step up transformer,depending on whether ZL IS greater than or less than ZO.

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Answer : Stub:- Stub is the piece of short circuited transmission line which is used to tune out the reactance of the load when connected across the transmission line as close as possible. ... but lengths are independently adjustable. The double stub matching provides wide range of impedance matching.

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Answer : Stub is a piece of short circuited transmission line which is used to tune out the reactance of the load when connected across the transmission line as close as possible. Single Stub Matching : ... The single stub match is perhaps the most widely used matching circuit and can match any load.

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Answer : L=0.5 mH/Km C=0.08 µF

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