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: 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: 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: An N-tone ΣΔ converter is obtained by introducing N zeros in the noise transfer function (NTF) while maintaining a flat signal transfer function (STF). N-tone ΣΔ converters are particularly well suited for multi-carrier systems. Like low-pass and band-pass ΣΔ converters, the performance of this converter depends heavily on the resonator characteristics. Non-idealities in the resonator manifest themselves as a deterioration in the signal to noise ratio (SNR). In this paper, we study different implementations of N-tone ΣΔ converters. We look into the various sources of non-idealities in the converter and their impact on system SNR. Using our understanding of the impact of nonidealities, we present a capacitor mismatch insensitive design for N-tone ΣΔ converters.
    International Symposium on Circuits and Systems (ISCAS 2005), 23-26 May 2005, Kobe, Japan; 01/2005