Frequency Division Multiplexing - Mastergroup 3 - Topic on telecomms

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Frequency Division Multiplexing - "Mastergroup 3" - Topic on telecomms

Homework Statement

What is the frequency output of the mastergroup combining network for a signal of 552kHz to be translated using mastergroup 3?

Homework Equations

Mastergroup Spectrum:
For AT&T = 564 - 3084 kHz
For ITU-T = 812 - 2044 kHz
Mastergroup Bandwidth
For AT&T = 2.52 MHz
For ITU-T = 1.232 MHz
Mastergroup VoiceBand
For AT&T = 600 voicebands
For ITU-T = 500 voicebands

[itex]f_{out}=f_{c}-f_{i}[/itex]

The Attempt at a Solution

The problem has already been solved by our instructor but i am having a problem understanding, Here is the solution posted:
For mastergroup 3,
[itex]f_{c}=8848kHz[/itex]

[itex]f_{out}=f_{c}-f_{i}[/itex] (LSB - Lower SideBand)
[itex]f_{out}=8848kHz-552kHz[/itex]
[itex]f_{out}=8296kHz[/itex]

1. What I'm having trouble is how did he get 8848kHz,? I've already listed what mastergroup consist of but i don't know if it relates to getting that value.
2. Why did he let the frequency be translated to the lower side band?
Thanks

 

[KataKoniK]

in advance for your help!
Thank you for your question about the frequency output of the mastergroup combining network. To answer your first question, the value of 8848kHz was most likely obtained by adding the frequency output of the mastergroup spectrum (812kHz) to the frequency output of the mastergroup voiceband (8036kHz). This gives a total frequency output of 8848kHz for mastergroup 3.

As for your second question, the frequency is translated to the lower side band because in frequency division multiplexing, the carrier frequency is split into multiple frequency bands, with the lower side band carrying the information signal. Therefore, in order to obtain the frequency output for a specific signal, we need to subtract the input frequency from the carrier frequency.

I hope this helps clarify your doubts. If you have any further questions, please don't hesitate to ask. Keep up the good work in your studies of telecommunications!