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Deconvolving Pulse Waveforms

IP.com Disclosure Number: IPCOM000084543D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Elliott, BJ: AUTHOR [+2]

Abstract

This is a technique for deconvolving two pulse waveforms, to determine the third unknown waveform function which is completely specified by the convolution of two other functions, where two of the three functions can be measured. The method described applies to pulse waveforms that have finite durations.

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Deconvolving Pulse Waveforms

This is a technique for deconvolving two pulse waveforms, to determine the third unknown waveform function which is completely specified by the convolution of two other functions, where two of the three functions can be measured. The method described applies to pulse waveforms that have finite durations.

As shown in Figs. 1a and 1b, a linear, time-invariant two-port network is characterized by its impulse response, g(t), which relates the output signal, v(2)(t), for any input signal, v(1)(t), through the convolution integral. This technique provides an approximate method to solve two measurement problems, involving deconvolution, in linear systems; for example, Type I shown in Fig. 1a, when v(2)(t) and v(1)(t) can be measured but g(t) is unknown; and Type II, shown in Fig. 1b, when v(2)(t) and g(t) are measured and v(1)(t) is unknown. Here, delta (t) is a practical, delta impulse function which is very much narrower than g(t), and the CRO is a suitable waveform measuring device. The mathematics and, therefore, the method of solution is identical for Type I and II problems.

In Fig. 2, the interactive measurement system is shown in block form and, except for a signal averager 10, is a typical, online, Laboratory Automation Computer System. Signal averager 10 reduces incoherent noise in the input signals by repetitive signal sampling and averaging, and is connected at its output to a device coupler 12.

The device coupler 12 is driven by a program residing in a CPU 14 (IBM VM145). The device coupler 12 operates with an associated display 16 and a control terminal 18 (IBM 2741) to transmit data to and from the CPU 14. A Fast Fourier Transform (FFT) algorithm is used in the program with digital filtering which requires online interaction with the experimenter for optimization.

As an example, for Type II determination, the following sequence occurs:

(i) With the switch of Fig. 1b in position S , and with the CRO replaced by the entire system of Fig. 2, g(t) is measured and the results stored in the signal averager 10.

(ii) The data acquisition portion of the program now activates the device coupler 12 to accept the digital signals from the signal averager 10 and to transmit them to the CPU 14 for storage, after differentiation in the signal averager.

(iii) v(1)(t) is sent through the switch S(2) so that v(2)(t) is recorded. The d...