Dynamics of Frequency Estimation in the Frequency Domain

The possibility of error reduction in frequency estimations with a multipoint interpolated discrete Fourier transformation (DFT) for the Hanning window is described. An estimation of the periodic parameter by the interpolation of the DFT gives the same effect as the reduction of spectrum tails. Sidelobe suppression is obtained at the cost of widening the main lobe, and this increases noise contributions. In this paper, we try to show a tradeoff between the reduction in systematic error of the frequency estimation and the uncertainty of the estimated results due to the interpolated algorithm. The number of interpolated points depends on the noise level and on the mutual positions of the frequency components of the signal.     

Design aspects of focal beams from high-intensity arrays

As the applications of ultrasonic thermal therapies expand, the design of the high-intensity array must address both the energy delivery of the main beam and the character and relevance of off-target beam energy. We simulate the acoustic field performance of a selected set of circular arrays organized by array format, including flat versus curved arrays, periodic versus random arrays, and center void diameter variations. Performance metrics are based on the -3-dB focal main lobe (FML) positioning range, axial grating lobe (AGL) temperatures, and side lobe levels. Using finite-element analysis, we evaluate the relative heating of the FML and the AGLs. All arrays have a maximum diameter of 100λ, with element count ranging from 64 to 1024 and continuous wave frequency of 1.5 MHz. First, we show that a 50% spherical annulus produces focus beam side lobes which decay as a function of lateral distance at nearly 87% of the exponential rate of a full aperture. Second, for the arrays studied, the efficiency of power delivery over the -3-dB focus positioning range for spherical arrays is at least 2-fold greater than for flat arrays; the 256-element case shows a 5-fold advantage for the spherical array. Third, AGL heating can be significant as the focal target is moved to its distal half-intensity depth from the natural focus. Increasing the element count of a randomized array to 256 elements decreases the AGL-to-FML heating ratio to 0.12 at the distal half-intensity depth. Further increases in element count yield modest improvements. A 49% improvement in the AGL-to-peak heating ratio is predicted by using the Sumanaweera spiral element pattern with randomization.     

A method for characterizing waveform recorder errors using thepower spectral distribution

A new approach for analyzing the errors observed in sine wave tests of waveform recorders is presented. The approach involves estimating the power spectral distribution for the residuals observed from a sine wave test. The approach is compared to the more common approach of calculating the Fourier transform of the recorded signal. It is shown that the new approach is easier to interpret quantitatively, and its use is demonstrated on some test data     

Boundary effect free and adaptive discrete signal sinc-interpolation algorithms for signal and image resampling

The problem of digital signal and image resampling with discrete sinc interpolation is addressed. Discrete sine interpolation is theoretically the best one among the digital convolution-based signal resampling methods because it does not distort the signal as defined by its samples and is completely reversible. However, sinc interpolation is frequently not considered in applications because it suffers from boundary effects, tends to produce signal oscillations at the image edges, and has relatively high computational complexity when irregular signal resampling is required. A solution that enables the elimination of these limitations of the discrete sine interpolation is suggested. Two flexible and computationally efficient algorithms for boundary effects free and adaptive discrete sinc interpolation are presented: frame-wise (global) sine interpolation in the discrete cosine transform (DCT) domain and local adaptive sinc interpolation in the DCT domain of a sliding window. The latter offers options not available with other interpolation methods: interpolation with simultaneous signal restoration/enhancement and adaptive interpolation with super resolution.     

一种电能及功率的精确评价方法

目的 介绍了一种用于精确评价正弦交通电电能及功率既简单又实用的方法。方法 使用数据采集系统及正弦波拟合法评价电能及功率参数。结果 与其他方法相比,该方法可同时给出正弦电压及电汉的幅度、频率、相位差、功率和功率因数等参量。结论 该方法指标评价全面,所有指标均可有效溯源到电压、电流和频率这些基本量上。分析了评价过程的误差来源,获得减小其评价误差的方法。其核心技术除了波形拟合外,还采用了一种性能独特的单频数字滤波器技术来减小评价结果的不确定度,并阐述了滤波方法及过程。     

Design and optimisation of a high-frequency EMC wideband horn antenna

A new approach for the design of high-frequency electromagnetic compatibility (EMC) broadband double-ridged horn (DRH) antennas is presented. In this approach, first a conventional DRH antenna at 1-18 GHz frequency band is considered. Using a thorough sensitivity analysis of different structural parameters of the 1-18 GHz DRH antenna, several modifications are applied to this antenna to overcome its deficiencies especially in its radiation pattern at higher frequencies. The final achieved design is then scaled up in the frequency to arrive at a design suitable for higher frequency ranges. A wideband DRH antenna for 18-40 GHz frequency band is then designed using this approach. The lower frequency ratio of 1:2.2 in the new antenna as opposed to the 1:18 ratio in the conventional antenna permits us to choose the best frequency window for the scaling up process. Besides, an optimisation technique is employed to further improve the antenna performance to meet the design goals over the entire new frequency band, that is, to have a single main lobe directed along the horn axis without any deterioration, and to have acceptable broadband gain with the minimum of 10 dB, and voltage standing wave ratio (VSWR) of less than 1.5. The final design which is more compact compared with the other commercial antennas has been used to make a prototype antenna. Measurements show that the built prototype meets the design goals very well     

Ultra-wideband SAW correlator

A surface acoustic wave (SAW) correlator that satisfies FCC bandwidth requirements for ultra-wideband (UWB) operation has been built and tested. The correlator operates within the 3.1 to 10.6 GHz bandwidth region and uses bi-phase shift keying (BPSK) modulation to achieve a spreading of the main lobe to a 25% bandwidth. This device is capable of spreading or de-spreading a UWB signal directly to or from base-band to microwave frequencies.     

Novel portable electrical detection system for DNA SENSOR application

A novel, portable, electrical detection system was constructed for DNA sensor application to detect DNA hybridisation. The read-out circuit consists of an analogue circuit and a digital circuit. The analogue circuit with an IC MAX038 generates a sine wave with a constant frequency (10?kHz), which serves as the input for the DNA sensor. The DNA sensor consists of active and reference sensors. DNA hybridisation between the DNA probe and the target sequences causes changes in the conductance of the conductive membrane (DNA/MWCNTs) on the sensor surface, which lead to changes in the amplitude of the sine wave from the sensor output compared with that of the reference signal output (input sine wave). We used a digital circuit with a microprocessor (PIC33FJ256MC710) to determine the change in the amplitude of the sine wave signal of the sensor. From these digital data, the difference in the amplitudes of the active and reference sensors was calculated and displayed on the liquid crystal display. Measurement results show that the portable electrical detection system can detect DNA target concentrations as low as 0.16?µM. The detection of the amplified polymerase chain reaction sample and the reproducibility of the DNA sensor results were also determined using the designed readout circuit. The proposed electrical detection system is suitable for DNA sensor application.     

调频信号的数字化解调

介绍一种用3参数正弦波拟合算法实现的、绝对收敛的4参数最小二乘正弦波拟合算法，给出了其收敛区间、绝对收敛判据以及实现过程，在此基础上讨论实现正弦载波的调频信号的精确解调问题，使用一个周期的正弦波曲线模型的滑动拟合法，实现了频率调制信号波形的精确解调，在调制信号是方波的情况下，给出了频率解调的仿真结果和其它参数的波动情况；在1个实测调频曲线波形上进行的解调分析，给出了频率调制波形的解调结果，同时，在调制信号也是正弦波的情况下，给出了解调失真的计算方法和结果。本方法是评价载波为正弦波的调频信号的一种优良方法，准确度高、分辨力强，可用于调频信号源及其解调设备的指标评价和计量测试。     

音乐信号分析中常数Q变换的性能研究

由于采用指数分布的频域采样点,常数Q变换(ConstantQTransform—CQT)在音乐信号的音调分析中有着独特的优点。但是常数Q变换的性能究竟如何,还需进行多方面的研究,以便能开发其潜力、完善其不足。对于两种CQT定义下的频率估计准确性问题进行了讨论,给出了频率估计误差的计算公式和给定音节频率分辨率下CQT窗函数长度应满足的关系;通过实验研究了CQT和DFT在多音阶频率检测时的性能以及窗函数对CQT性能的影响。通过和DFT的比较,可以看到CQT在某些方面具有比DFT更好的特性。对于CQT的一些局限性文中也作了简单的评述。     

Wide frequency range sine wave VCO with a tunable inductor andcapacitor

A voltage-controlled oscillator (VCO) with sine wave output has been built using a tunable inductor along with a tunable capacitor to operate at frequencies ranging from 100 kHz to over 20 MHz. The method of tuning the inductor by changing the permeability of its ferrite core and the ability to extend the frequency response of the core are discussed. Dynamic characteristics of the VCO are explained with examples of a parallel and series tank implementation     

非均匀采样条件下残周期正弦波形的最小二乘拟合算法

对一种用三参数正弦波拟合算法实现的四参数最小二乘正弦波拟合算法进行了实验研究。主要针对在极低频率正弦信号测量控制过程中问题比较突出的,以不足一个信号周期且非均匀采样的部分信号波形估计其4个参数的工程问题。提出了一种以局部周期正弦波形实现的四参数拟合方法,其优点是无需先验初值估计。仿真及实验均证明了该方法的有效性和可行性,从而为波形参数测量与控制提供了一种实现方式。     

混沌态杜芬振子与弱正弦信号参量估计

建立了一个对微弱正弦信号参量变化极其敏感的动力学系统.首先对多参量简化杜芬方程进行了改进,采用梅尔尼科夫过程函数讨论了方程的解和微分流形的演化情况;分析了非高斯色噪声对杜芬振子混沌运动行为的影响;进而提出了一种新的非高斯色噪声背景下正弦信号参量估计方法.理论分析和仿真实验都表明,此杜芬振子混沌状态下对任何零均值噪声具有免疫力,对正弦信号参量变化极为敏感.     

Detecting a Weak Sine Wave and Measuring Its Parameters

This paper is concerned with the problem of detecting a weak sine wave and measuring its parameters in the presence of arbitrary gain fluctuations and additive Gaussian noise. The parameters considered are frequency, phase, and signal-to-noise power ratio. Some practical methods are presented for detecting the weak sine wave and measuring its parameters. The methods are simple to implement, insensitive to gain fluctuations, and relatively accurate. The implementations have, inherently, a wide dynamic range.     

A Predictable Subnanosecond Step Generator

Determination of the response of a time domain instrument to a voltage step is preferable to determination in terms of its response to sine waves. Unfortunately the output waveshape of a voltage or current step generator cannot be evaluated as easily as that of a sine wave source. Consequently, investigators rely (or should rely) upon waveform predictability rather than waveform measurement when employing step generators in system characterization. One form of a predictable step generator is discussed that is useful in the subnanosecond to tens of nanoseconds time region after the step edge. A practical realization of this form is given that has predictability to within 1 percent in that time region from 350 picoseconds to 6 nanoseconds after an 80-picosecond rise-time step edge.     

一个通用的频谱误差校正快速算法

建立通用的频谱误差数学模型;得出利用信号频域能量信息反求信号幅值、利用信号频域能量重心信息反求信号频率的频谱误差校正算法。该算法适用于加任意对称窗的情形,且速度快、精度高,其有效性得到了数值仿真的验证。     

The implementation of a digital sine wave oscillator using theTMS320C25: distortion reduction and applications

The implementation of a digital sine wave oscillator using the TMS320C25 digital signal processor (DSP) is described. The system is implemented with the Dalanco Spry model 25 DSP board, and a software system is designed whereby an IBM PC host computer provides control of the waveform generator functions and parameters. Waveforms are generated using the lookup-table (LUT) method. The methods of direct LUT and linear interpolation of missing samples are implemented and compared with a method that uses a trigonometric identity to reduce the harmonic distortion of the sine wave by effectively increasing the table length of the direct LUT method. The results of an experiment performed in the digital domain are presented without consideration of the problem of analog reconstruction. The oscillator can produce a sine wave without the nonuniform sampling distortion associated with fractional addressing, over the range of 7.2 Hz to 58.8 kHz, with a resolution of 7.2 Hz using 384 data words. The trigonometric identity method uses less data memory than other methods for the same distortion levels. Waveforms for the sum of two sine waves, a frequency swept sine wave, amplitude modulation (AM), and frequency modulation (FM) signals are shown as applications of the waveform generator     

Synthesising gene clock with toggle switch and oscillator

The usefulness of a genetic clock lies in its role to stimulate a sequence of logic reactions for sequential biological circuits. A clock signal is a periodic square wave, its amplitude alternates at a steady frequency between fixed minimal and maximal levels. Transition between the minimum and the maximum is instantaneous for an ideal square wave; however, the function is unrealisable in physical bio‐systems. This research develops a new genetic clock generator based on a genetic oscillator, in which, a sine wave generator is adopted as a signal oscillator. It is shown that combination of a genetic oscillator with a toggle switch is able to generate clock signals forming an efficient way to generate a near square wave. In silico study confirms the proposed idea.Inspec keywords: genetics, oscillators, biological techniques, square‐wave generators, switchesOther keywords: toggle switch, genetic clock, logic reaction sequence, sequential biological circuits, clock signal, periodic square wave, physical biosystem, genetic clock generator, sine wave generator, signal oscillator, genetic oscillator     

爆破地震波频率对多自由度弹性体系动力响应的影响分析

通过对一个三自由度弹性体系在垂直方向上分别加载多个不同主频的实测爆破地震波和理想正弦波,使用集中冲量法利用计算机编程求解出各爆破地震波激励下的竖向动力响应,并通过分析该结构体系的各动力响应幅值变化来探讨爆破地震波频率对三自由度弹性体系动力响应的具体影响。计算结果表明,结构的第一自振频率在分析结构各层质点的响应幅值中起主导地位;考虑爆破地震波是一个包含很多频率成分的复杂的振动信号,在分析实测爆破地震波频率对结构动态响应的影响时,除主频外,应同时考虑其它占有相当能量比例的优势频率的影响。     

调相信号的数字化解调

通过单周期正弦波曲线模型的滑动拟合法,获得正弦序列的瞬时频率信息,使用对瞬时频率的积分运算,实现了正弦载波相位调制信号波形的精确解调.在调制信号是方波的情况下,给出了相位解调的仿真结果和其它参数的波动情况;在1个实测调相曲线波形上进行的解调分析,给出了相位调制波形的解调结果;在调制信号也是正弦波的情况下,给出了解调失真的计算方法和结果.本方法用于评价载波为正弦波的调相信号时,具有准确度高、分辨力高的特点,可用于调相信号源及其解调设备的指标评价和计量测试.