Contents
What is the effect of mismatch in characteristic impedance?
Any mismatch in the impedance of these three components in an RF system will cause a portion of the signal power traveling from source to load to be reflected back to the source.
What happens reflected power?
If there is reflected power as a result of a reactive load, the load line becomes an open curve. This means that for a portion of the cycle, substantial voltage exists across the tube at the same time high current is being drawn through it. This results in the large plate dissipation.
Why is reflected power bad?
The reflected power from a bad load will put additional stresses on the transmission lines. As an example, if the normal transmitter power is 10,000 watts and the load has a VSWR of 1.05:1, the maximum RMS voltage in a 50-ohm transmission line will be 725 volts with a peak voltage of 1,025 volts.
How does a mismatch in impedance affect a RF system?
Any mismatch in the impedance of these three components in an RF system will cause a portion of the signal power traveling from source to load to be reflected back to the source.
How does the magnitude of a mismatch affect power?
The magnitude of the mismatch will determine the portion of the power that keeps traveling down the cable towards the load and the portion that gets reflected back to the source. Figure 4.
What are the effects of impedance matching and switch?
For an air dielectric, maximum power handling occurs near 30 Ω, while minimum loss occurs around 75 Ω. Filling the cable with a dielectric other than air will have an effect on the frequency at which maximum power handling and minimum loss occur. We have discussed the importance of impedance matching in RF systems.
Why is mismatch loss important in an amplifier?
Consequently, not all of the available power generated by the amplifier gets transferred to the load. This is most important in antenna systems where mismatch loss in the transmitting and receiving antenna directly contributes to the losses the system—including the system noise figure.