Baseband Signal Processing and Digital to Analog Converters

[SriHarsha Korada]

Hi Guys,
I have a question on the need for Digital to analog converters in Transmitters. To elaborate bit further:

1) Because of the advantages of the Digital signals, most go the signal processing in wireless communications is performed in baseband. But my question is: Since digital modulation is also a part of baseband processing, how can we still say its baseband as a carrier signal (which has high centre frequency) is used for modulation?
and

2) The output of baseband processing block In the transmitter side, is given to Digital to Analog converter in order to transform the digital signal to analog signal that can be sent over the wireless Channel Here my question is: Anyway due to to digital modulation, analog signal is present at the output of Modulation block and why still the point of DAC?

Even though, these questions seem basic, I need some explanation on this stuff. Hope to hear some valuable answers.

BR,
Sri

 

[sophiecentaur]

A digital signal processor is usually designed around a particular clock frequency, which would probably not be related to the wanted transmit carrier frequency. As with nearly all comms processes (analogue or digital) it is usual to produce a standard IF (analogue intermediate frequency) signal with suitable spectrum filtering which is mixed down or up to the required carrier frequency. The aggravation of making a DSP unit that would work at all carrier frequencies would be just too great.

 

[SriHarsha Korada]

A digital signal processor is usually designed around a particular clock frequency, which would probably not be related to the wanted transmit carrier frequency. As with nearly all comms processes (analogue or digital) it is usual to produce a standard IF (analogue intermediate frequency) signal with suitable spectrum filtering which is mixed down or up to the required carrier frequency. The aggravation of making a DSP unit that would work at all carrier frequencies would be just too great.

So, you mean to say that the carrier frequency being used at digital modulator is some kind of Intermediate frequency? Even in that scenario also, the output would be analog in nature. But again why DAC?