BasicB-008-005-004
Why should the impedance of a filter match the transmission line where it is inserted?
A
Answer
Safety
Type
A
To avoid unwanted reflection
B
To minimize noise in the receiver
C
To prevent spurious emissions
D
To preserve the balance of the line
Answer Notes
In any RF system, maximum power transfer occurs when the impedance of the source, the transmission line, and the load (including inserted components like filters) are perfectly matched. If you insert a filter with a mismatched impedance into a transmission line, it creates a discontinuity in the system.
This electrical discontinuity causes some of the forward RF energy to bounce back toward the transmitter. This is known as an unwanted reflection, which results in a higher Standing Wave Ratio (SWR). Matching the impedance ensures the RF energy flows smoothly through the filter without bouncing back.
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What type of filter attenuates RF energy above and below a certain range of frequencies?
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