Assume we have a signal repeater, a simple repeater that amplifies the signal then transmits it as is. Does the output power of the repeater is dependent on the received signal at the repeater ? for example:

  • Case-1: A repeater received power of the original signal is -60 dbm.
  • Case-2: A repeater received power of the original signal is -90 dbm.

will there be 30 dbm difference of power at the output of the repeater? If no which component of the repeater is responsible for discarding the input power?

  • $\begingroup$ I suspect there's some context to your question that you're not including. What you are describing is an ideal amplifier, and the output indeed has a 30 dB difference in the cases you list. But a repeater is not (just) an amplifier. $\endgroup$ – MBaz Mar 18 '18 at 16:58
  • $\begingroup$ A repeater i'm talking about will usually include some kind of filter and a mixer to change frequency and power amplifier and an antennas. I just want to know if the output of a repeater is constant regardless of the received power or if it is dependent on the receiver power? $\endgroup$ – Hosam Amleh Mar 18 '18 at 17:12

I don't think there's a single unique answer to your question: it depends on the type of repeater and how it was designed. Many different repeaters are described here, including some details about input/output their power relationship.

A repeater with a constant output power could be designed in at least two ways:

  • The repeater first decodes the received signal to recover the information it carries: it will perform matched filtering, symbol synchronization, and maybe even FEC decoding. Then, it re-creates the corresponding analog signal and transmits it with the specified transmitter power. This type of repeater is also called a "signal regenerator".

  • The repeater has an automatic gain control (AGC) circuit controlling a variable-gain amplifier to keep the output at a constant power level. This repeater could be much simpler than the previous one, and the implementation could (potentially) be completely analog. Its main drawback is that noise and distortion are also amplified along with the original signal.


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