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Analysing an RF splitter and power levels

A splitter is a device that has a single input and several outputs. It is used to send a signal to several different locations. For example, your apartment or house might have cable TV that delivers a wideband signal via a coaxial cable. A splitter can be used to send the same signal to different rooms so that individual TV sets can receive all the programs and channels that are available from the cable TV company. This problem is about a splitter with three outputs.

A broadband signal with analog TV signals from 50 MHz to 600 MHz is connected to the input of the splitter. At a channel frequency of 50 MHz the input power is -20 dBm. The output power at each of the three splitter output terminals is - 27 dBm.

a. What is the power at the splitter input in mW?

b. What is the power at each splitter output in mW?

c. What is the total output power from the splitter (add the three outputs together)?

d. Why is the total output power not equal to the input power?

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Solution Preview

(a) Input power to splitter quoted as

P(in)dBm = -20 dBm

Now we find Power at the input (quoted in mW) by the definition of P(in) dBm which is given by general expression given below.

P(in) dBm = 10.Log{ P(in mW)/1 mW) (1)

Taking the 10 multiplier from RHS to LHS we get (2) thus

P(in) dBm/10 = Log{ P(in mW)/1 mW) (2)

Raising both sides of (2) to the power ...

Solution Summary

Analysing an RF splitter and determining power levels at each input/output. Conversion of lvels from units of dBm to mW