Filter Pulse Research Articles

Temporal filtering with time lenses

The problems of spatial diffraction and optical dispersion in the time domain was extended by analogy to optical ultrafast pulse filtering. An analog setup in the 4-f spatial-filter configuration is proposed, and several applications such as the temporal signal convolver or correlator and the joint transform processor are suggested, followed by ways to generate the temporal filter. The implementation aspects and an example of the speed superiority of this approach are also discussed.

Pulse filtering techniques for mercuric iodide gamma ray detectors

The performance of mercuric iodide gamma ray detectors is limited by hole transport properties. Pulse filtering techniques have been developed to circumvent the poor hole collection efficiency and long collection times. Using pulse filtering techniques which compensate for incomplete hole collection, improvements in energy resolution by as much as a factor of 2 has been achieved with detectors of 1–5 mm thickness. For the thickest detectors (∼ 1 cm), electron-only measurement techniques have recently demonstrated significant improvement over standard pulse shaping. A summary of computer and analog techniques which correct pulse amplitudes for incomplete hole collection is presented and a new technique for centimeter-thick detectors is described. Spectral results are presented and the implementation and limitations of the different methods are discussed.

Spectral hole burning and pulse filtering in optically dense samples

The dependence of temporal responses of hole-burning filters on the burning time and the initial optical density is analyzed. Their essentially nonexponential form and, in some cases, nonmonotonic behaviour related to the deviation from the lorentzian holeshape are discussed.

Pulse Filtering for Thick Mercuric Iodide Detectors

Mercuric iodide (HgI/sub 2/) is a semiconductor material of interest as a gamma-ray spectrometer due to its large band gap and high atomic number, properties which allow room temperature operation and provide high gamma-ray cross section. At EG and G Energy Measurements, Inc. (EG and G/EM), single crystals of mercuric iodide are grown by vapor sublimation and fabricated into detectors of 0.2-12.0 mm thickness. Thin detectors ( 10% resolution and peak-to-valley ratios < 2:1. The authors have investigated a number of electronic pulse filtering techniques for thick mercuric iodide detectors and have achieved improved spectral response for detectors of 1-5 mm thickness and gamma ray energies up to 1.5 MeV. Conventional gaussian and gated integration filters were considered as well as more sophisticated filtermore » combinations in order to develop methods of reducing charge measurement errors caused by poor hole collection. When using these techniques, energy resolutions of 3%-6% and peak-to-valley ratios of 5:1 are common. In this paper they discuss these approaches and present results with thick detectors.« less

Use of metric techniques in ESM data processing

The paper describes the use of metric techniques in an electronic support measures (ESM) data processing scheme developed at Smith Associates Consulting System Engineers Limited for the UK Ministry of Defence (Procurement Executive). The ESM data processing scheme takes in digital pulse data describing the radar pulses illuminating an ESM receiver. The output from the scheme is a continuously updated emitter table, which lists the emitters present in the environment and specifies the deduced parameters of these emitters. Metric techniques play an important role at two distinct stages of the scheme: firstly in direction-of-arrival (DOA) RF pulse filtering, and secondly in emitter table updating. In DOA RF filtering, the pulses are processed using two-dimensional cluster analysis. The method ensures that pulses from a single emitter are not separated into different batches, but that pulses from distinct emitters are separated, unless their parameters overlap in both DOA and RF. The same result cannot in general, be achieved using one-dimensional filtering. The scheme uses a computationally efficient method, in which the metric technique is applied to groups of pulses following sequential one-dimensional filterings in DOA and then RF. In emitter table updating, a metric technique is used to ensure that the pulses from an emitter already on the emitter table are correctly associated with that emitter table entry, and are not added as a new emitter seen for the first time. This overcomes the problem that, for some emitters, some of the parameters can change discontinuously when the emitter changes mode. The metric technique ensures that, provided some of the parameters remain approximately constant, the correct association is made.

Modulation Transfer Noise Effects from TDMA Carriers to FDM/FM Carriers in Memoryless Nonlinear Devices

This paper examines modulation transfer noise effects from TDMA carriers to FDM/FM carriers in a common memoryless nonlinear amplifier. The modulation transfer noise consists of discrete as well as continuous spectral components. Three types of discrete components are identified: those due to pulse filtering only, those due to on-off bursting only, and cross terms due to both mechanisms simultaneously. The continuous spectral component of the modulation transfer noise is due to pulse filtering only. A comparison of the relative intensities of all these noise components is also presented.

A Linear D. C. Restorer

This paper introduces a new concept in nuclear pulse filtering, that of using linear active feedback to accomplish a pulse manipulation which until now has been performed only by nonlinear methods. The linear method eliminates threshold effects and extends the circuit application to low level and to highly linear signals, without the inherent increase in noise produced by the nonlinear methods. A linear circuit has been constructed which performs the function of D. C. restoration. That is, pulses which occur randomly in time and have low frequency components which overlap to produce degradation of primary pulse information, may be clarified and separated by the circuit. The action is similar to the basic Robinson restorer except that no threshold or other nonlinearity is involved and no noise need be introduced. The results are otherwise comparable, and time of pulse recovery to 0.01% of signal level may be traded off against reduction of signal amplitude.