A new multiwire proportional chamber with fast single strip readout and individual analog to digital conversion

A new precision MWPC with an active length of 400 mm has been built for the Munich Q3D spectrograph. The readout method uses the individual amplitude signals of narrow cathode strips (3 mm width, 0.5 mm spacing). Each of these signals is converted into a digital word by an individual fast ADC. A newly developed hard wired logic calculates the position of the particle event by the center of gravity method with a dead time of about 108 μs. The position resolution in test measurements simulating particle events was better than 0.1 mm.     

A simple analog division scheme

A technique for analog division of two voltage signals that offers high accuracy (0.5%) and relatively good response, especially when the numerator value is nearly constant, is presented. The proposed method is based on the relation of a signal's frequency to its period. The basic idea is to convert input voltage to frequency (through a voltage-controlled oscillator (VCO)) and then produce an output voltage proportional to the period of this signal. The circuit implementing this method is easy to build and may be used in many instrumentation and control applications where the reciprocal of a voltage is needed. Supporting experimental results and performance measurements are also given     

A Josephson analog limiter circuit

The authors have designed, fabricated and successfully tested a Josephson integrated circuit that is used to limit the range of an analog input signal. The circuit consists of a single Josephson junction with a suppressed critical current. The impedance of this suppressed junction consists of the nonlinear quasiparticle resistance in parallel with the capacitance of the junction. The junction capacitance is used to advantage as one pole of a second-order low-pass filter, the other element of which is a thin-film inductor. This filter can perform the function of a slew-rate-limiting filter, at the input to a high-speed comparator. The authors fabricated individual junctions and measured their suppression characteristics and have found that a 2-μm×4.5 μm junction with a nominal critical current of 170 μA can be suppressed to less than 4 μA of critical current with a 14-mA control current. Complete limiter circuits have been fabricated and tested for both their DC and transient characteristics. Measured DC response is in good agreement with simulation, but parasitic capacitance present in the fabricated devices limited the -3 dB bandwidth to about 3.6 GHz     

A new analog voltage sorter

An analog circuit for comparing and sorting two input voltages is described. Using the circuit as a basic unit, a four-input sorter is designed. A technique to determine which of the four inputs corresponds to (address of the input of) a given output is also presented. The procedure can be extended to design an n-input sorter     

Computer simulation of the transmission of modulated signals through linear analog circuits using fast Fourier transforms

An algorithm is proposed for computing transformations of modulated signals in linear circuits by the spectrum method and by applying fast Fourier transforms. The algorithm computes transformations of oscillations with complex modulation and large angle modulation indexes in analog circuits. The accuracy of the proposed method is discussed. A program is described for analyzing modulated oscillations in linear selective circuits that complements the known electronic circuit simulation programs. Translated from Izmeritel'naya Tekhnika, No. 8, pp. 38–40, August, 1998.     

A cryogenic fast response thermometer

Multipurpose carbon thin film resistance thermometers have been developed for cryogenic use. Carbon was electron beam evaporated onto polycrystalline alumina substrates with copper films as electrical contacts. The thermometers were coated with thin glass layers. The desired electrical resistance of the sensors was obtained with a final heat treatment.Their sensitivity at 4.2 K is approximately 300 Ω K^?1. Between 4.2 and 20 K the film resistance can be expressed as a function of temperature by a usual correlation of the form In R = A₀ + A₁T + A₂ (InT)². These sensors have been developed as separate devices to be soldered or glued onto experiments. Nevertheless, their response is fast; at 4.2 K their thermal relaxation time is better than 1 ms and their thermal delay time is of the order of 70 μs.     

A fast track pattern recognition

An algorithm for fast track pattern recognition is presented. Its main features are an optimized data organization and a conformal mapping to speed up fitting procedures. The code is applied to a generic collider detector. Reconstruction time, track finding efficiencies, and momentum resolution are presented.     

A new adaptive analog test and diagnosis system

This paper presents a low-cost analog test system with diagnosis capabilities. The tester is able to detect faults in any linear circuit by learning a reference circuit behavior in a first step, and comparing this behavior against the output of the circuit under test in a second step. For a faulty circuit, a third step takes place to locate the fault. The diagnosis method consists in injecting probable faults in a mathematical model of the circuit, and later comparing its output with the output of the real faulty circuit. This system has been successfully applied to a case study, a biquad filter. Soft, large, and hard deviations on components, as well as faults in operational amplifiers, were considered. Experimental results have proven the feasibility and efficiency of the proposed test and diagnosis system     

A high speed push-pull analog memory using transfluxors

A two-transfluxor analog memory is described. It uses single coincident-current pulses on separate signal and bais windings to store a flux level analogous to the input signal sample in about 10 μs. An additional winding senses the set flux level and permits further linearization of the storage characteristic by means of negative feedback.     

A wideband analog continuum correlator for radio astronomy

Design details for a 1-GHz bandwidth analog continuum cross-correlator for the Owens Valley Millimeter Array are presented. The correlator uses a pair of microwave mixers fed in phase quadrature to realize a complex multiplier for each baseline in the array. Very fast 180° phase switching is included to reject spurious signals     

A fast Josephson SFQ shift register

A Josephson SFQ (single flux quantum) shift register circuit operating under a two-phase power was designed and tested. The test cell was fabricated using the Nb/AlO_x/Nb junction SNEAP process. The main data latch is DC biased; the data storage is accomplished by the transfer of a single flux quantum in or out of a SQUID (superconducting quantum interference device) superconducting loop. A two-phase sinusoidal clock with offset is used to operate the circuit. Simulations verify that the operating frequency can go beyond 70 GHz, with operating margins exceeding 20%. Preliminary measurements indicate that the circuit operates as intended     

多彩色空间相关分析的人脸识别算法

人脸识别是当前人工智能和模式识别的研究热点,得到了广泛的关注.基于对不同色彩空间数据的分析,论文提出了多彩色空间典型相关分析的人脸识别方法.文中对2维的Contourlet变换特性进行了分析和讨论,利用Contourlet的多尺度,方向性和各向异性等特点,提出了一种基于Contourlet变换的彩色人脸识别算法.算法对原图进行Contourlet分解,对分解得到的低频和高频图像进行cca分析.典型相关分析是一种有效的分析方法,其实际应用十分广泛.低频系数反映图像的轮廓信息,高频系数反映图像的细节信息,使用cca充分利用不同频率的信息,使不同色彩空间的不同分辨率图形的相关性达到最大,得到投影系数,最后,采用决策级最近邻分类器完成人脸识别.在对彩色人脸数据库AR的识别实验中,该算法识别率达到98％以上,与传统算法相比,该算法不仅既有良好的识别结果,而且具有很快的运算速度.     

A fast intelligent data acquisition system

A fast intelligent multiprocessor data acquisition system is described here. The system based on the MC68010 using the VME bus can acquire data via the CAMAC dataway at transfer rates up to 800 Kbytes/s. The system has a user friendly interface which builds the required assembly code needing only the CAMAC FNAs used in the experiment. In addition the system can be easily modified using the standard MC68010 assembly language to handle most preprocessing requirements. The system design will also allow for future expansion to the 32 bit word and faster instruction time of the MC68020. This expansion will allow for transfer rates well over a Mbyte/s.     

A fast method for direction-of-arrival estimation

In many eigenvalue-eigenvector-based direction-of-arrival estimation algorithms, one finds orthogonal basis vectors for the noise subspace. We propose a circulant basis for the noise space which can be calculated more efficiently than an orthogonal basis. The new method for high signal-to-noise ratio (SNR) has a performance similar to the well-known MUSIC algorithm but can be implemented much more efficiently.     

一种快速图像纹理分析算法

针对目前的纹理分析算法普遍存在计算复杂、运行时间过长的缺点,提出了一种新的图像纹理分析算法。该算法利用差分概念定义出图像的差分矩阵和差分直方图,并从差分直方图中提取特征进行图像纹理的相似度度量。由于本算法在考虑人类视觉特性的基础上尽量采用加减运算,因此不但具有与人类视觉特性相联系的特点,更使得算法的运行效率大大提高。使用本算法对brodatz 图像库进行的检索实验表明,该算法在查准率和检索效率上与共生矩阵算法相比分别提高13.9160%和 9.5 倍,具有与传统算法相比更好的检索效果和更高的检索效率。因此该算法可以满足实时性要求较高的场合,弥补了目前算法运行时间长的缺点。     

A simple technique for analog tuning of frequency synthesizers

An analog implementation of the fractional N-phase-locked-loop variable-frequency synthesis technique is presented. In addition to its simplicity, this implementation allows tuning over broad frequency ranges. The synthesizer was developed in response to a need for a compact, low-power, local oscillator for a swept heterodyne, low-frequency, battery-operated, portable spectrum analyzer. The resulting prototype synthesizer was constructed on a 4-in×4-in circuit board using standard CMOS integrated circuits. The total power requirements were +7 V at 8 mA and -7 V at 1 mA when the synthesizer is operated in the 380-580-kHz frequency range. Further reductions in size may be expected from the use of surface mount devices. Spectral data are presented for the prototype circuit serving as the local oscillator in a prototype swept-frequency spectrum analyzer. That is, instead of a spectral analysis of a fixed synthesizer frequency, the synthesizer was swept through a range of frequencies about a stable reference applied to the input of the prototype analyzer. Thus the results are conservative , since they include the effects of noise coupled to the sweep voltage from other circuitry within the prototype analyzer. This method of evaluation demonstrates one of the distinct advantages of this circuit     

A high-speed NDRO analog memory using electrodeposited permalloy wires

An NDRO analog memory was constructed with an electrodeposited Permalloy wire and tested to demonstrate that high speed, low power, and high stability are realized. The interrogation copper wire is wound around the deposited wire, and the wire is driven along the hard axis by a 225-kHz sinusoidal field. The center copper wire, on which Permalloy was deposited, is used for the memory setting and sensing the level. The output signal is a 450-kHz sinusoidal wave, and the amplitude is proportional to the flux level. The flux level was found to be set by means of the pulse field as short as 100 ns. The output signal is quite small, but it is stably amplified using a tuned amplifier because of the definite frequency of the signal. Furthermore, some experiments on operational mode and flux reversal were performed, and the results are discussed.