Return loss of a stand-alone antenna is 10 dB. One 6 dB attenuator with return. loss of 40 dB is connected at the input of that antenna. What will be the approximate return loss of the combined (Antenna + Attenuator) port?

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  1. 40 dB
  2. 22 dB
  3. 16 dB
  4. 10 dB

Answer (Detailed Solution Below)

Option 2 : 22 dB
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Concept:

Return loss (RL) measures how well a device or system matches its load. It is defined as the ratio (in dB) of the power sent into a device to the power reflected back due to impedance mismatch.

When an attenuator is placed in front of an antenna, it improves the effective return loss at the input port of the system.

The formula for combined return loss is:

\(RL_{\text{combined}} = RL_{\text{antenna}} + 2 \times \text{attenuation}\)

Given:

Return loss of antenna = 10 dB

Attenuator = 6 dB (with own return loss = 40 dB, but only antenna return is affected here)

Calculation:

\(RL_{\text{combined}} = 10 + 2 \times 6 = 10 + 12 = 22~dB\)

 

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