摘要:

An approximate theory of narrow angle diffraction and thin lenses is presented based on the characterization of a lens as a linear FM generator and the diffracted field as the response of a quadratic phase filter. Applications Include optical filtering, contrast improvement, and phase microscopy. The underlying electro-optical analogies lead to a simple development of pulse compression, time scaling, and real time spectral analysis.

ISSN:0272-6343    

DOI:10.1080/02726348908915223

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726348908915224

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726348908915225

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An approach to determining the derivative of a signal which is an exponentially-decaying function of time is presented. The case of a waveform sampled in time is treated. The method is applicable to functions which are complicated combinations of decaying exponentials. Robust behavior in the presence of additive noise is also obtained. It is shown that computing the derivative of the waveform by Fourier transforming it, using the DFT derivative theorem, and taking the inverse Fourier transform yields a much more accurate approximation to the derivative in the presence of noise than does computing the forward difference. A recursive discrete Fourier transform is then used, to permit computing the derivative of a sampled waveform as the samples are taken. A recursive DFT derivative theorem is derived. This is then applied to numerical simulations using a function which is the sum of three unevenly-weighted exponentials with different decay constants, and it is shown that useful results for the derivative are obtained even when the randomly-distributed additive noise has a peak value as high as 0.25 times the peak value of the original waveform. Extensions of the work to obtain a recursive chirp-Z transform and derivative theorems, and applications to resonance extraction, are also presented.

ISSN:0272-6343    

DOI:10.1080/02726348908915226

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A method for automatic correction of the quantization error in time-interval counters is presented. A detailed analysis for Gaussian time-intervals is given for synchronous and asynchronous counting mode, considering the time jitter as well as the bias error inherent in the counter. The usefulness of the method is proved by numerical examples and experimental results.

ISSN:0272-6343    

DOI:10.1080/02726348908915227

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper deals with the development of an airborne platform for measuring transient or broadband CW electromagnetic (EM) fields. The considerations and guidelines [1] useful in designing such a platform are discussed. The EM problem consists of choosing the appropriate sensor type and location on an aircraft such that the scattered fields from the aircraft and the sensor mountings do not significantly couple to the sensor, while measuring the Incident field. These design considerations were applied In specifically designing a nose boom B-dot sensor for the NASA F-106 B aircraft [2]. Sample experimental results [3] with comparisons to calculated Incident fields are also presented.

ISSN:0272-6343    

DOI:10.1080/02726348908915228

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The objective of this paper is to present a methodology for the computation of the response of a multiconductor transmission line terminated by linear networks to an arbitrary excitation. The lines are embedded in multilayered homogeneous lossy dielectric media and have uniform cross sections along their lengths. To check the accuracy of the theoretical results, extensive experimental verification has been carried out.

ISSN:0272-6343    

DOI:10.1080/02726348908915229

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper considers the response of electric- and magnetic-field sensors in terms of spherical modal expansions to identify the electric-and magnetic-dipole terms which are associated with the ideal angular response to an incident plane wave. Considering an idealized spherical resistive sheet sensor, the dipole surface current densities are computed and bandwidth and figure of merit determined to optimize the choice of Rs.

ISSN:0272-6343    

DOI:10.1080/02726348908915230

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor