Title :
Novel Direct Digital Synthesizer Design for OFDM Digital Receivers
Author :
Moran, D.R. ; Menoyo, Javier Gismero
Author_Institution :
Dept. of Signals, Syst. & Radiocommun., Univ. Politecnica de Madrid
Abstract :
This paper describes a novel design approach for the DDS (direct digital synthesizer) required to correct the frequency shift in the received signal of a digital OFDM receiver. The traditional phase accumulator has been modified to perform modulus 2N-1 accumulation. This modification provides fine frequency tuning capabilities using a very small sine/cosine look-up-table. Current systems use hundreds or thousands carriers requiring a DDS with very small frequency steps. This requires enormous amounts of memory for the sine/cosine LUT and an accumulator with many bits, limiting the maximum clock frequency. A reduction of required memory of more than 3 orders of magnitude can be achieved while an smaller phase accumulator allows for higher frequency operation. The design can deal also with systems where selectable carrier spacing is used such as DAB (digital audio broadcasting), with a minimal memory resource count increase. The design focuses on FPGA implementation although it may be applied also in an ASIC to achieve lower power and area reduction
Keywords :
OFDM modulation; application specific integrated circuits; direct digital synthesis; field programmable gate arrays; integrated circuit design; radio receivers; table lookup; ASIC; DDS; FPGA implementation; LUT; accumulator; application specific integrated circuit; digital OFDM receiver; direct digital synthesizer; field programmable gate array; frequency shift; orthogonal frequency division multiplexing; sine-cosine look-up-table; Clocks; Demodulation; Digital audio broadcasting; Field programmable gate arrays; Frequency synthesizers; Local oscillators; OFDM modulation; RF signals; Sampling methods; Signal design; Receivers; algorithms; digital audio broadcasting; digital radio; field programmable gate arrays; frequency synthesizers;
Conference_Titel :
Wireless Technology, 2006. The 9th European Conference on
Conference_Location :
Manchester
Print_ISBN :
2-9600551-5-2
DOI :
10.1109/ECWT.2006.280426