By means of analyzing the frequency spectrum characteristics of domestic frequency- shift track signal we propose a technical improvement solution to it based on the orthogonal theory and demodulation technology in mo...By means of analyzing the frequency spectrum characteristics of domestic frequency- shift track signal we propose a technical improvement solution to it based on the orthogonal theory and demodulation technology in modern digital signal processing to guaranteed the solution accomplishes the optimized reception at the receiver, thereby enhance system reliability and quality. At same time we simulated this solution with MATLAB, and implemented it on the vc33 experimental platform of floating- point Digital Signal Processing (DSP).展开更多
电子设备集成度的提高对于音频集成电路生产和测试等环节的要求越来越高,尤其是音频数模转换器(Digital to Analog Converter,DAC),本质上为数模混合信号电路,采用数模混合信号自动化测试设备(Automatic Test Equipment,ATE)价格昂贵,...电子设备集成度的提高对于音频集成电路生产和测试等环节的要求越来越高,尤其是音频数模转换器(Digital to Analog Converter,DAC),本质上为数模混合信号电路,采用数模混合信号自动化测试设备(Automatic Test Equipment,ATE)价格昂贵,而采用传统自动测试仪测试覆盖率低、测试时间长,导致这类电路的测试成本较高且测试产能不足。介绍了一种基于现场可编程门阵列(Field Programmable Gate Array,FPGA)和LabWindows的音频DAC电路测试方案,硬件上用FPGA实现音频测试所需的直接数字频率合成(Direct Digital Frequency Synthesizers,DDFS)模块,软件上通过运用LabWindows自带的采样、加窗、快速傅里叶变换(Fast Fourier Transform,FFT)等数字信号处理函数,快速准确地测试各项模拟参数,并在用户界面(User Interface,UI)显示测试值和后台保存测试数据。展开更多
A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to eval...A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to evaluate and determine the processing capability and then construct the parallel processing array for multi-channel signals according to the restriction of operation timing. Using this method, the design of multi-channel digital receiver may be simplified. Finally, a design example was used to show how to apply this method.展开更多
An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we...An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).展开更多
In the context of next-generation optical access networks beyond 10 G, for high SE and flexible dynamic bandwidth allocation (DBA), the scheme of hybrid 64/16/4QAM-OFDM signal for downlink transmission and hybrid 16/8...In the context of next-generation optical access networks beyond 10 G, for high SE and flexible dynamic bandwidth allocation (DBA), the scheme of hybrid 64/16/4QAM-OFDM signal for downlink transmission and hybrid 16/8/QPSK-OFDM signal for uplink transmission is successfully proposed and experimentally presented in a full-duplex PON based on OFDM system. Here, for the uplink, in order to unit management of the optical line terminal (OLT) and reduce cost, the optical source functioned as the optical subcarrier at optical network units (ONUs) is from OLT in the central station. Moreover, there is an external cavity laser (ECL) with center frequency of 193.2 THz not only employed as optical modulated signal but also acted as LO signal. Our simulation results show that bit error ratio (BER) under hardware detection forward error correction has been successfully gained after 20 km of SSMF transmission. It is observed that the receiver sensitivity of multilevel PSK (M-PSK) is obviously larger than that of the M-QAM in this measurement scheme.展开更多
Optical spectral measurements are crucial for optical sensors and many other applications,but the prevailing methods,such as optical spectrum analysis and tunable laser spectroscopy,often have to make compromises amon...Optical spectral measurements are crucial for optical sensors and many other applications,but the prevailing methods,such as optical spectrum analysis and tunable laser spectroscopy,often have to make compromises among resolution,speed,and accuracy.Optical frequency combs are widely used for metrology of discrete atomic and molecular spectral lines.However,they are usually generated by optical methods and have large comb spacing,which limits the resolution for direct sampling of continuous spectra.To overcome these problems,this paper presents an original method to digitally generate an ultrafine optical frequency comb(UFOFC)as the frequency ruler for spectral measurements.Each comb line provides one sampling point,and the full spectrum can be captured at the same time using coherent detection.For an experimental demonstration,we adopted the inverse fast Fourier transform to generate a UFOFC with a comb spacing of 1.46 MHz over a 10-GHz range and demonstrated its functions using a Mach–Zehnder refractive index sensor.The UFOFC obtains a spectral resolution of 0.01 pm and response time of 0.7 μs;both represent 100-fold improvements over the state of the art and could be further enhanced by several orders of magnitude.The UFOFC presented here could facilitate new label-free sensor applications that require both high resolution and fast speed,such as measuring binding kinetics and single-molecule dynamics.展开更多
文摘By means of analyzing the frequency spectrum characteristics of domestic frequency- shift track signal we propose a technical improvement solution to it based on the orthogonal theory and demodulation technology in modern digital signal processing to guaranteed the solution accomplishes the optimized reception at the receiver, thereby enhance system reliability and quality. At same time we simulated this solution with MATLAB, and implemented it on the vc33 experimental platform of floating- point Digital Signal Processing (DSP).
文摘电子设备集成度的提高对于音频集成电路生产和测试等环节的要求越来越高,尤其是音频数模转换器(Digital to Analog Converter,DAC),本质上为数模混合信号电路,采用数模混合信号自动化测试设备(Automatic Test Equipment,ATE)价格昂贵,而采用传统自动测试仪测试覆盖率低、测试时间长,导致这类电路的测试成本较高且测试产能不足。介绍了一种基于现场可编程门阵列(Field Programmable Gate Array,FPGA)和LabWindows的音频DAC电路测试方案,硬件上用FPGA实现音频测试所需的直接数字频率合成(Direct Digital Frequency Synthesizers,DDFS)模块,软件上通过运用LabWindows自带的采样、加窗、快速傅里叶变换(Fast Fourier Transform,FFT)等数字信号处理函数,快速准确地测试各项模拟参数,并在用户界面(User Interface,UI)显示测试值和后台保存测试数据。
文摘A design method for parallel processing application on multi-channel low-intermediate-frequency(LIF) digital receiver was presented. It is based on the DSP sub-array with a simple topology and operation timing to evaluate and determine the processing capability and then construct the parallel processing array for multi-channel signals according to the restriction of operation timing. Using this method, the design of multi-channel digital receiver may be simplified. Finally, a design example was used to show how to apply this method.
文摘An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).
文摘In the context of next-generation optical access networks beyond 10 G, for high SE and flexible dynamic bandwidth allocation (DBA), the scheme of hybrid 64/16/4QAM-OFDM signal for downlink transmission and hybrid 16/8/QPSK-OFDM signal for uplink transmission is successfully proposed and experimentally presented in a full-duplex PON based on OFDM system. Here, for the uplink, in order to unit management of the optical line terminal (OLT) and reduce cost, the optical source functioned as the optical subcarrier at optical network units (ONUs) is from OLT in the central station. Moreover, there is an external cavity laser (ECL) with center frequency of 193.2 THz not only employed as optical modulated signal but also acted as LO signal. Our simulation results show that bit error ratio (BER) under hardware detection forward error correction has been successfully gained after 20 km of SSMF transmission. It is observed that the receiver sensitivity of multilevel PSK (M-PSK) is obviously larger than that of the M-QAM in this measurement scheme.
基金Zhaohui Li acknowledges the support of the National Basic Research Programme of China(973)(Project No.2012CB315603)National High Technology 863 Research and Development Program of China(Nos.2013AA013300 and 2013AA013403)+5 种基金the Research Fund for the Doctoral Program of Higher Education of China(20124401110003)National Natural Science Foundation of China(NSFC)(Grant No.61435006)the Program for New Century Excellent Talents in University(NCET-12-0679)in ChinaXuming Zhang acknowledges the NSFC(Grant No.61377068)the Hong Kong Research Grant Council(Grant Nos.PolyU 5327/11E and N_PolyU505/13)the Hong Kong Polytechnic University(Grant Nos.G-YN07,4-BCAL and G-YBBE).
文摘Optical spectral measurements are crucial for optical sensors and many other applications,but the prevailing methods,such as optical spectrum analysis and tunable laser spectroscopy,often have to make compromises among resolution,speed,and accuracy.Optical frequency combs are widely used for metrology of discrete atomic and molecular spectral lines.However,they are usually generated by optical methods and have large comb spacing,which limits the resolution for direct sampling of continuous spectra.To overcome these problems,this paper presents an original method to digitally generate an ultrafine optical frequency comb(UFOFC)as the frequency ruler for spectral measurements.Each comb line provides one sampling point,and the full spectrum can be captured at the same time using coherent detection.For an experimental demonstration,we adopted the inverse fast Fourier transform to generate a UFOFC with a comb spacing of 1.46 MHz over a 10-GHz range and demonstrated its functions using a Mach–Zehnder refractive index sensor.The UFOFC obtains a spectral resolution of 0.01 pm and response time of 0.7 μs;both represent 100-fold improvements over the state of the art and could be further enhanced by several orders of magnitude.The UFOFC presented here could facilitate new label-free sensor applications that require both high resolution and fast speed,such as measuring binding kinetics and single-molecule dynamics.
