The measurement problem of detecting gravitational waves from binary pulsars

A new method for processing the output signal from a gravitational wave direction finder in the measurement problem of detecting and identifying gravitational waves from binary relativistic astrophysical objects is discussed and studied.     

Use of the maximum probability method for increasing the accuracy of measuring distance by a range finder with frequency modulation of the sounding signal

Analysis of the error for a range finder using the maximum probability method for estimating the range is provided. The effect of noise interference, nonlinearity of the modulation characteristic of the range finder transmitter, parasitic amplitude and phase modulations are evaluated by means of computer simulation. Comparative analysis is given for algorithms of frequency measurement whose use makes it possible to exclude anomalous errors in using the maximum probability method. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 22–26, October, 2006.     

A low-cost laser range finder based on an FMCW-like method

The purpose of this paper is to present the prototype of a low-cost laser range finder. It belongs to the flight time measurement category. In this case, the time of flight is converted into a beat frequency proportional to the distance to be measured. This physical conversion is realized with an optical power modulation of the laser beam by a chirped wave. The experimental set-up is detailed with the main functional blocks. Experimental results are provided and the main possible improvements are discussed     

Crosstalk analysis of 1 m to 10 m laser phase-shift range finder

A heterodyne phase-shift laser range finder has been developed for the measurement of distances of 1 m to 10 m. An analysis of the crosstalk between the current source and the photoelectric receiver of this device permits prediction of the accuracy of the setup. For example, when the amplitude of the crosstalk is proportional to the modulation frequency and for a given photoelectric signal-to-induction ratio of 30 at 10 m, the maximum corresponding error is about 5 cm. To determine the magnitude of the crosstalk, we propose a model taking into account that the amplitude and the phase-shift of the induced signal depend on whether the coupling is inductive or capacitive. Crosstalk modeling shows that very slight inductive or capacitive coupling is sufficient to affect distance measurement     

Measurement of the energy loss in superconducting magnets

A device is described which measures the energy losses in superconducting magnets. It is excited by alternating current, and is based on the use of a Hall probe as a wattmeter. The signal from the probe, proportional to the power of the losses, integrated over a cycle of current change, corresponds to the losses in the magnet. A feature of the device consists in the use of a special measuring magnet and a system for balancing the reactive voltage, so that the losses can be measured in high-power superconducting magnets.     

Gravitational-wave detector as a direction finder for low-frequency gravitational radiation sources from binary relativistic astrophysical objects

The design of a gravitational-wave direction finder for sources of low-frequency gravitational radiation from binary relativistic astrophysical objects is described.     

一种新颖的四天线时空调制通信定位综合化系统

针对通信定位综合一体化的趋势和未来移动通信发展的需要,提出了一种新颖的四天线时空调制技术,设计了一种差分编码非正交四相对空调制通信定位综合化系统,该系统除具有PSK的通信能力外,还能测定用户方位,具有抗多径的潜力,最后给出了信号的调制编码,接收机的解调与载波恢复,方位角估计等关键问题的解决方案,分析了在高斯信道下的差分解调和相干解调的误码率和方位角的测量精度。     

D类功放中数字调制器的研究与实现

数字脉冲宽度调制(Digital Pulse Width Modulation,DPWM)结构简单、稳定性好,是主动声呐D类功放中常用的调制技术,但是它会产生信号失真和电磁干扰问题。针对主动声呐中D类功放的要求,设计了一种新的1.5bitΣ-Δ调制器。该调制器不仅能够改善DPWM存在的信号失真和电磁干扰问题,而且能够解决常规Σ-Δ调制器存在的高开关频率导致的高开关损耗问题。采用现场可编程逻辑门阵列(FPGA)对该调制器进行实现,在全桥D类功放上进行了实验验证。通过1.5bitΣ-Δ调制器和DPWM性能对比,表明该1.5bitΣ-Δ调制器适合主动声呐D类功放的应用。     

A dual modality optical fiber sensor

We propose and demonstrate a fibre optic system based on bi-tapered silica fibre that can simultaneously measure strain and fibre curvature. Both modalities on the signal can be extracted with no measurable crosstalk between them. The experimental signal has a pure phase modulation when strain is applied to the tapered fibre optic section of the sensor and the signal shows only intensity modulation when an un-tapered fibre section is bent. High sensitivity is achieved from the experimental results for strain and bending losses and the estimation of measurement errors is 0.2 and 0.1%, respectively. This system offers low-cost, compactness and it can be adapted for structural health monitoring.     

Effect of external signal on the output power of an oscillator with electron feedback

The effect of an external single-frequency harmonic signal on the output power of an oscillator with electron feedback has been studied by analytical and numerical methods. It is established that an increase in the input signal power leads to sharp growth in the output power of the nonautonomous oscillator. Physical processes that take place in the electron beam with virtual cathode under the action of an external harmonic signal, which leads to velocity modulation in the electron beam entering the interaction space, have been analyzed. The obtained results well agree with the data of previous experimental investigations of the signal gain in a low-voltage vircator.     

Double acousto-optic monochromator of images with tunable width of the transmission function

A new double acousto-optic monochromator (DAOM) based on a paratellurite crystal has been designed and constructed, in which the width of the transmission function can be varied by means of a periodic linear frequency (chirp) modulation of the ultrasonic control signal. The transmission function of the DAOM has been studied for various device parameters, including chirp frequency deviation, chirp modulation period, and control signal power. The proposed DAOM can be effectively used for filtration and analysis of spectral images.     

Phase Recovery in Interferometers by Optothermal Diode Laser Modulation

Abstract

A technique is described for the frequency modulation of a diode laser based on the optothermal effect. It is shown that it is possible to generate the frequency modulation with a minimum of power modulation. A frequency shift of approximately 1 GHz per mW of optothermal pump power was achieved in practice. The power modulation was about 7% of that observed when injection current modulation was used to generate a similar frequency shift. The optothermal frequency modulation technique was applied in a phase recovery scheme for a fibre interferometer based on pseudo-heterodyne signal processing.     

Calculation of Skin Depths and Eddy-Current Power Losses for Magnetic Position Sensors

1. IntroductionIn a quasi-stationary magnetic field, eddy-currelltfrom an alternating-current excitation induces secondary currents and fields between magnetic material and position sensor. The skin depths and eddycurreat losses are also induced in a conductor whenan alternating external magnetic field is applied tothe conductor[1]. For a magnetic position sensort ifthe position of the moving sensor is given, the waveform of the output voltage induced by eddy-currentcan be used as an index to …     

Handheld direction of arrival finder with electronically steerable parasitic array radiator using the reactancedomain MUltiple SIgnal Classification algorithm

Reactance-domain multiple signal classification (RD-MUSIC) is a promising scheme for enabling ESPAR (electronically steerable parasitic array radiator) antennas to accurately estimate the DOAs (directions-of-arrival) of radio waves. The ESPAR antenna is a variable directional antenna designed for battery-operated mobile terminals, and is utilised for handheld DOA finder applications as well as for wireless communication systems. We present some experimental results showing that the RD-MUSIC with a conventional calibration obtains a sharp spectrum for accurate DOA estimation, although the ESPAR antenna is equipped with only a single-port output unlike a conventional array antenna. The results also demonstrate that RD-MUSIC works well even when exploiting fewer beam patterns than the number of antenna elements. Moreover, we have verified that a human body hardly generates any degradation of DOA estimation even holding the DOA finder close to the body. The degradation of DOA estimation because of a human body is kept to less than about 6deg, and removing beam patterns towards directions of reflections from the human body is found to be useful in decreasing the errors. Although the reduction in the number of beams results in reducing the total number of estimated waves, it can mitigate the influence of a human body for actual DOA estimation with the handheld DOA finder.     

基于希尔伯特变换的信号解调算法及其在飞机供电特性参数测试系统中的应用

电压调制幅度、频率调制幅度和畸变频谱是对飞机机载电源系统供电特性参数进行测试时与信号调制相关的重要参数。为了更好地测试这些参数,提出了一种基于希尔伯特变换原理的数字解调算法,可以将采集的幅度或频率调制信号进行解调分析;同时,构建了一套飞机供电特性参数测试系统,将解调程序与硬件设备结合,通过程序控制数据采集卡对机载电源信号采样与解调分析;设计了实验对波形发生器产生的调制信号进行采样与解调,验证了该系统具有良好的效果,可以应用于飞机供电特性参数的测试中。     

A simple method for the evaluation of microwave mixer diodes

A simple method is described for the evaluation of the various microwave mixer diodes which can be used in 9-GHz electron paramagnetic resonance (EPR) spectrometers using magnetic field modulation below 1 kHz. The advantage of this method over other methods is that it is optimized for EPR applications and determines the optimum operating conditions for each microwave diode. This method utilizes a microwave bridge with a reference arm with an attenuator to control the microwave bias power level, and a signal arm where the signal is attenuated, phase shifted, and modulated at the typical magnetic field modulation frequencies. The microwave power from the two arms is recombined and demodulated by the microwave diode. The output of the microwave diode is then recorded with various video loads, microwave bias power, and modulation frequencies. Measurements are performed to determine the effect of the preamplifier that followed the microwave diode on the signal-to-noise ratio (SNR). The recorded spectra are used to determine the SNR, the noise floor, and the 1/f corner frequency. Comparison of these factors for the different types of microwave diodes shows that some Schottky-barrier diodes have noise figures at 1 kHz that are as low as those for tunnel diodes     

一种降低D类功率放大器开关噪声的设计

传统D类功率放大器因特有的开关噪声对水下电子设备的信号接收、通信控制和信号传输等电信号产生很大的干扰,限制了D类功率放大器在水下电子设备中的广泛应用针对这一现象,首先阐明了Σ-Δ调制的D类功率放大器降低开关噪声的原理,然后对传统调制方式和Σ-Δ调制方式的D类功率放大器进行原理分析,并在Simulink软件中进行仿真对比。仿真结果表明,传统D类功率放大器在开关频率处的开关噪声能量高,Σ-Δ调制的D类功率放大器的开关噪声能量分散在一定的带宽内,并且开关噪声能量峰值低于传统D类功率放大器。     

75kW超声波发生器控制信号研究

75kW超声波发生器的控制信号必须满足死区时间稳定,频率可调、稳定,能够间隙激发等要求。采用的是电压驱动型脉宽调制控制芯片TL494CN,其产生方波频率在15~40kHz范围内连续可调,死区时间为3μs。用NE555P产生调制波,该调制波信号与TL494CN产生的频率可调脉冲信号经调制后形成有间隙的方波信号,用于控制功率器件IGBT的驱动电路。从示波器记录的输出波形上可以看出:TL494CN生成的频率可调方波与NE555P产生的调制波经过调制电路后,得到能够间隙发射的控制信号。通过现场试验,该控制信号能够控制IGBT的驱动电路实现大功率超声的激发,且满足大功率超声激发的要求。     

A method of compensating atmospheric background radiation

A method of compensating the atmospheric background and a method of detecting thermal objects on the atmospheric background using infrared thermal direction finders with a wide field of view is described. An algorithm of a two-dimensional spatial filter is developed, which can be realized as software in the video processor of the thermal direction finder. The algorithm enables the process of detecting air targets to be automated and enables their video images to be displayed on the monitor of the monitoring device in binary form.     

Direct bidirectional angle-insensitive imaging of the flow signal intensity in Doppler optical coherence tomography

We introduce a new method, to our knowledge, for direct detection of flow signal intensity by stationary target rejection. In our system, two delay lines are constructed with identical scanning speed and ranging depth. One delay line is used for depth ranging as well as phase modulation, and the other one acts as a full-range retroreflector (FRRR). The signal from this FRRR carries the overall features of local phase modulation, and it is used as the local oscillator for coherent demodulation. With this setup, stationary targets can be rejected at a 4-kHz high-pass cutoff frequency of the filter that follows the demodulator, compared with 20 kHz for conventional fixed-frequency demodulation. This technique features angle insensitivity and provides flow direction as well by implementing standard in-phase and quadrature detection. Besides the direct directional detection of flow signal intensity, flow speed information can be acquired with postprocessing.