Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Bandwidth transmitted signal and lowpass equivalent signal

Status
Not open for further replies.

zzungboy

Newbie level 3
Joined
Sep 20, 2009
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,306
Hi,

I have simple question.
I think it is basic concept for digital communication.
However, I'm a little bit confusion on this.
Maybe, I'm missing some point.

In many books, when the bandwidth of lowpass equivalent signal is B, the BW of the transmitted signal is 2B.
Why? Do you provide the reason or give me some reference to understand this?

Thanks in advance.
 

industry.2009

Newbie level 2
Joined
Sep 28, 2009
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
England
Activity points
1,289
Re: Bandwidth transmitted signal and lowpass equivalent sign

zzungboy said:
Hi,

I have simple question.
I think it is basic concept for digital communication.
However, I'm a little bit confusion on this.
Maybe, I'm missing some point.

In many books, when the bandwidth of lowpass equivalent signal is B, the BW of the transmitted signal is 2B.
Why? Do you provide the reason or give me some reference to understand this?

Thanks in advance.

Hi Deares,

The formula of that is
BW=(B+1)F
F is central frequency that is carrier frequency
B is modulation index
B could be between 1 to 5 (I think)

Best regards,
Kevin
 

EngrAdnan

Junior Member level 1
Joined
Jan 8, 2008
Messages
15
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
1,363
Re: Bandwidth transmitted signal and lowpass equivalent sign

At the baseband the real bandwidth of signal is B, when the signal is modulated for passband (IF) the complex envelope of signal is shifted from 0 Hz to Centre frequency and the -ve frequency spectrum goes into +ve axis and doubles the BW.
 

Gemini1706

Member level 5
Joined
Jul 3, 2002
Messages
81
Helped
3
Reputation
6
Reaction score
2
Trophy points
1,288
Activity points
1,120
If a real signal bandwidth is 2B, then its "equivelent" low-pass model would be B becasue the low pass model is complex, it has I and Q components EACH one is B in bandwidth, thus retaining the 2B bandwidth of the "real" signal.
 
Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top