An improved switched-capacitor bandgap reference with a continuous output voltage of 1.26 V has been implemented with Chartered 0.35-μm 5-V CMOS process. The output offset voltage, induced by non-ideal characteristic...An improved switched-capacitor bandgap reference with a continuous output voltage of 1.26 V has been implemented with Chartered 0.35-μm 5-V CMOS process. The output offset voltage, induced by non-ideal characteristics of operational amplifier and bias current generator, is suppressed by the proposed sample-and-hold circuit and self-bias technique. Experimental results show that the proposed circuit operates properly under a supply voltage varying from 3 to 5 V. The measured temperature coefficient is 112 ppm/℃ and the power supply rejection ratio of output voltage without any filtering capacitor is -40 dB and -33 dB at 100 Hz and 10 MHz, respectively.展开更多
Cartier frequency offset （CFO） estimation is critical for orthogonal frequency-division multiplexing （OFDM） based transmissions. In this paper, we present a low-complexity, blind CFO estimator for OFDM systems wit...Cartier frequency offset （CFO） estimation is critical for orthogonal frequency-division multiplexing （OFDM） based transmissions. In this paper, we present a low-complexity, blind CFO estimator for OFDM systems with constant modulus （CM） signaling. Both single-input single-output （SISO） and multiple-input multiple-output （MIMO） systems are considered. Based on the assumption that the channel keeps constant during estimation, we prove that the CFO can be estimated uniquely and exactly through minimizing the power difference of received data on the same subcarriers between two consecutive OFDM symbols; thus, the identifiability problem is assured. Inspired by the sinusoid-like cost function, curve fitting is utilized to simplify our algorithm. Performance analysis reveals that the proposed estimator is asymptotically unbiased and the mean square error （MSE） exhibits no error floor. We show that this blind scheme can also be applied to a MIMO system. Numerical simulations show that the proposed estimator provides excellent performance compared with existing blind methods.展开更多
This paper develops a Cyclic Prefix(CP)based joint Maximum-Likelihood(ML)estima-tion algorithm of Carrier Frequency Offset(CFO)and Power Delay Profile(PDP)for Multi-InputMulti-Output Orthogonal Frequency Division Mult...This paper develops a Cyclic Prefix(CP)based joint Maximum-Likelihood(ML)estima-tion algorithm of Carrier Frequency Offset(CFO)and Power Delay Profile(PDP)for Multi-InputMulti-Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM)systems.However,theexact solution of the joint ML estimation is very complex since it needs a search over amulti-dimensional domain.Thus a simplified method is proposed to estimate the CFO and the PDPiteratively via the alternating-projection method which could induce the multidimensional searchproblem to a sequence of simple one-dimensional searches.Simulations show that the proposed algo-rithm is more accurate and robust than the existing algorithms.展开更多
For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform ...For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform （FRFT） is proposed. The linear frequency modulation signals superimposed on the data signals are used as the training signals. By performing FRFT on the received signals and searching the peak value of the FRFT results, the receiver can realize timing synchronization and frequency offset acquisition simultaneously. Compared with the existing methods, the proposed algorithm can provide better timing synchronization performance and larger frequency offset acquisition range even under multi-path channels with low signal to noise ratio. Theoretical analysis and simulation results prove this point.展开更多
Filter-bank multicarrier （FBMC） with offset quadrature amplitude modulation （OQAM） is a candidate waveform for future wireless communications due to its advantages over orthogonal frequency division multiplexing ...Filter-bank multicarrier （FBMC） with offset quadrature amplitude modulation （OQAM） is a candidate waveform for future wireless communications due to its advantages over orthogonal frequency division multiplexing （OFDM） systems. However, because of or-thogonality in real field and the presence of imaginary intrinsic interference, channel estimation in FBMC is not as straightforward as OFDM systems especially in multiple antenna scenarios. In this paper, we propose a channel estimation method which employs intrinsic interference cancellation at the transmitter side. The simulation results show that this method has less pilot overhead, less peak to average power ratio （PAPR）, better bit error rate （BER）, and better mean square error （MSE） performance compared to the well-known intrinsic approximation methods （IAM）.展开更多
In orthogonal frequency-division multiplexing （OFDM） systems, the carrier frequency offset （CFO） destroys the orthogonality among subcarriers which degrades system performance. Various CFO estimation methods have ...In orthogonal frequency-division multiplexing （OFDM） systems, the carrier frequency offset （CFO） destroys the orthogonality among subcarriers which degrades system performance. Various CFO estimation methods have been developed to compensate for the CFO at the receiver. This paper describes a novel minimum output variance method for OFDM systems with CFO in additive white Gaussian noise channels. This method utilizes the phase and the amplitude of the received signal and reduces the mean square error of the CFO by about 3 dB compared with the original minimum output variance method.展开更多
基金supported by the National Natural Science Foundation of China(No.60676013)
文摘An improved switched-capacitor bandgap reference with a continuous output voltage of 1.26 V has been implemented with Chartered 0.35-μm 5-V CMOS process. The output offset voltage, induced by non-ideal characteristics of operational amplifier and bias current generator, is suppressed by the proposed sample-and-hold circuit and self-bias technique. Experimental results show that the proposed circuit operates properly under a supply voltage varying from 3 to 5 V. The measured temperature coefficient is 112 ppm/℃ and the power supply rejection ratio of output voltage without any filtering capacitor is -40 dB and -33 dB at 100 Hz and 10 MHz, respectively.
基金Project supported by the Intel Research Council and the Applied Materials Shanghai Research & Development Fund (No. 0507)
文摘Cartier frequency offset （CFO） estimation is critical for orthogonal frequency-division multiplexing （OFDM） based transmissions. In this paper, we present a low-complexity, blind CFO estimator for OFDM systems with constant modulus （CM） signaling. Both single-input single-output （SISO） and multiple-input multiple-output （MIMO） systems are considered. Based on the assumption that the channel keeps constant during estimation, we prove that the CFO can be estimated uniquely and exactly through minimizing the power difference of received data on the same subcarriers between two consecutive OFDM symbols; thus, the identifiability problem is assured. Inspired by the sinusoid-like cost function, curve fitting is utilized to simplify our algorithm. Performance analysis reveals that the proposed estimator is asymptotically unbiased and the mean square error （MSE） exhibits no error floor. We show that this blind scheme can also be applied to a MIMO system. Numerical simulations show that the proposed estimator provides excellent performance compared with existing blind methods.
基金the National Natural Science Foundation of China(No.60496311).
文摘This paper develops a Cyclic Prefix(CP)based joint Maximum-Likelihood(ML)estima-tion algorithm of Carrier Frequency Offset(CFO)and Power Delay Profile(PDP)for Multi-InputMulti-Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM)systems.However,theexact solution of the joint ML estimation is very complex since it needs a search over amulti-dimensional domain.Thus a simplified method is proposed to estimate the CFO and the PDPiteratively via the alternating-projection method which could induce the multidimensional searchproblem to a sequence of simple one-dimensional searches.Simulations show that the proposed algo-rithm is more accurate and robust than the existing algorithms.
基金supported by the National Natural Science Foundation of China(60672047).
文摘For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform （FRFT） is proposed. The linear frequency modulation signals superimposed on the data signals are used as the training signals. By performing FRFT on the received signals and searching the peak value of the FRFT results, the receiver can realize timing synchronization and frequency offset acquisition simultaneously. Compared with the existing methods, the proposed algorithm can provide better timing synchronization performance and larger frequency offset acquisition range even under multi-path channels with low signal to noise ratio. Theoretical analysis and simulation results prove this point.
基金supported by ZTE Industry-Academia-Research Cooperation Funds under Grant No.Surrey-Ref-9953
文摘Filter-bank multicarrier （FBMC） with offset quadrature amplitude modulation （OQAM） is a candidate waveform for future wireless communications due to its advantages over orthogonal frequency division multiplexing （OFDM） systems. However, because of or-thogonality in real field and the presence of imaginary intrinsic interference, channel estimation in FBMC is not as straightforward as OFDM systems especially in multiple antenna scenarios. In this paper, we propose a channel estimation method which employs intrinsic interference cancellation at the transmitter side. The simulation results show that this method has less pilot overhead, less peak to average power ratio （PAPR）, better bit error rate （BER）, and better mean square error （MSE） performance compared to the well-known intrinsic approximation methods （IAM）.
基金Supported by the Major Program of the National Natural Science Foundation of China (No. 60496311) Basic Research Foundation of Tsinghua National Laboratory for Information Sci-ence and Technology (TNList)
文摘In orthogonal frequency-division multiplexing （OFDM） systems, the carrier frequency offset （CFO） destroys the orthogonality among subcarriers which degrades system performance. Various CFO estimation methods have been developed to compensate for the CFO at the receiver. This paper describes a novel minimum output variance method for OFDM systems with CFO in additive white Gaussian noise channels. This method utilizes the phase and the amplitude of the received signal and reduces the mean square error of the CFO by about 3 dB compared with the original minimum output variance method.
