The Front End of a Digital Transceiver The first question that might arise is: What is the digital front end? The notion of the digital front end (DFE) has been introduced by the author in several publications (. [13]). Nonetheless it is useful to introduce the concept of the DFE at the beginning of this chapter. Several candidate receiver and transmitter schemes have been presented by Beach et al. in Chapter 2. They all have in common that they are different from the so-called ideal software radio insofar as the signal has to undergo some signal processing steps before the baseband. | Software Defined Radio Edited by Walter Tuttlebee Copyright 2002 John Wiley Sons Ltd ISBNs 0-470-84318-7 Hardback 0-470-84600-3 Electronic 6 The Digital Front End - Bridge Between RF and Baseband Processing Tim Hentschel and Gerhard Fettweis Technische Universität Dresden Introduction The Front End of a Digital Transceiver The first question that might arise is What is the digital front end The notion of the digital front end DFE has been introduced by the author in several publications . 13 . Nonetheless it is useful to introduce the concept of the DFE at the beginning of this chapter. Several candidate receiver and transmitter schemes have been presented by Beach et al. in Chapter 2. They all have in common that they are different from the so-called ideal software radio insofar as the signal has to undergo some signal processing steps before the baseband processing is performed on a software programmable digital signal processor DSP . These signal processing stages between antenna and DSP can be grouped and called the front end of the transceiver. Historically the notion of a front end was applied to the very part of a receiver that was mounted at or near the antenna. It delivered a signal at an intermediate frequency which was carried along a wire to the back end. The back end was possibly placed apart from the antenna. In the current context the notion of the front end has been undermined a bit and moreover extended to the transmitter part of a transceiver. The functionality of the front end can be derived from the characteristics of the signals at its input and output. Figure shows the front end located between the antenna and baseband processing part of a digital receiver. Its input is fed with an analog wide-band signal comprising several channels of different services air interfaces . There are Ni channels of bandwidth Bi of the ith service air interface . Integrating over all services i yields the total bandwidth B of the wide-band signal.
