Conference Paper

N-tone sigma-delta UWB-OFDM transmitter and receiver

Dept. of Electr. & Comput. Eng., Minnesota Univ., USA
DOI: 10.1109/ICASSP.2003.1202566 Conference: Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03). 2003 IEEE International Conference on, Volume: 4
Source: IEEE Xplore

ABSTRACT A new method for generating and detecting the UWB-OFDM signal using a modified sigma-delta modulator is proposed. Unlike narrowband OFDM, the UWB-OFDM spectrum can have gaps between subcarriers. The modified sigma-delta modulator, dubbed N-Tone sigma-delta, introduces N zeros at the frequencies in the quantization noise spectrum. These zeros match the locations of frequencies used by the OFDM system and the quantization noise spectrum fills the gaps in the spectrum of the UWB-OFDM signal. In fact this new structure could be used in other UWB systems anytime we have gaps in the spectrum of the transmitted signal. We describe both the transmitter and receiver structures for UWB-OFDM. We also study the spectrum of the underlying system.

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    ABSTRACT: A new null quantization noise canceling structure designed with the time domain-based interpolation and decimation for the N-tone sigma-delta modulation (SDM) UWB- OFDM transceiver is proposed. The required length of IFFT and FFT processing will not change with the interpolation factor. The bit error rate (BER) for QPSK, 16-QAM and 64-QAM UWB- OFDM transceiver using the 128-tone SDM circuit with the optimum quantization size and additive white Gaussian noise (AWGN) channel are simulated. The null quantization noise floor generated from the 128-tone SDM circuit can be avoided when the proper interpolation factor is chosen. The proposed null quantization noise cancellation structure can greatly reduce the hardware gate count and processing time of the N-tone SDM UWB-OFDM transceiver.
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    ABSTRACT: Abstract—An analysis of the N-tone SDM circuit with a new time domain-based interpolator and decimator structure in the UWB-OFDM transceiver is provided. The variance of null quantization noise generated from the N-tone SDM circuit is derived and employed to set the optimum quantization size. The SQNR of the N-tone SDM circuit is simulated, which is utilized to validate the ouput signal to quantization noise ratio (SQNR) of the N- tone SDM circuit obtained from the analyzed results.
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    ABSTRACT: We construct arithmetic modules for signal processing with sigma-delta modulated signal form which has advantage in signal quality over other pulsed signal forms. In the second part of this paper, multi-input multipliers are presented first. Secondly, dividers and square root function modules with the multiplier on their internal feedback path are constructed. Combined use of the multipliers, dividers, and the square root functions creates various algebraic functions including polynomial and rational functions. Only two bit-manipulations, bit-permutation with sorting networks and bit-reversal with NOT gates, have built up all the algebraic operations on any form of SD modulated signals. These modules, together with transcendental functions presented in the first part of this paper, organize an extensive module library for the sigma-delta domain signal processing. The multiplier output contains noise components which originate from quantization. The noise power can decrease in exchange for circuit complexity. A time-division multiplexing technique based on N-tone sigma-delta modulation is applied to the multipliers for reducing the complexity. Signal processing circuits built of nanometer-scale quantum effect devices must be equipped with fault tolerance of transient device error. By computer simulation of a multiplier built of single-electron tunneling devices, we found that the multiplier decreased its output SNDR from 43 to 27 dB at an OSR of 28 as the device error rate increased from 0 to 10-3. However, the multiplier was never functionally failed during the simulation.
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