GB1272303A - Oscillographs - Google Patents

Abstract

1,272,303. Cathode-ray tube circuits. FUNKWERK ERFURT VEB. 14 Feb., 1969, No. 8117/69. Heading H4T. In a sampling oscilloscope in which a recurrent H.F. waveform is sampled at a lower frequency to provide samples for application to the oscilloscope, frequency distortion of the samples (due to the finite width of the sampling period) is reduced by means of a correction circuit. The distortion is stated to consist of an increasing attenuation of the harmonics in the spectrum of the samples with increasing frequency of the recurrent H.F. waveform and the characteristics of the correction circuit which comprises a highpass filter are determined, when the apparatus is calibrated, from a comparison of the spectrum of the H.F. waveform with the spectrum of the waveform produced by the sampling process the latter spectrum being transposed to the equivalent position on the time scale of the H.F. waveform. Fig. 1, shows one embodiment in which the recurrent H.F. waveform is sampled by means of a switching device 1 which supplies samples to a capacitor 2 and thence via a L.P. filter 3 to the frequency-distortion correction network 4. In alternative arrangements the L.P. filter 3 may be omitted (Fig. 2, not shown), or the capacitor 2 may be omitted (Fig. 3, not shown) or the capacitor 2 may be omitted and the L.F. filter 3 combined with the frequencydistortion correction network 4 to provide a composite unit 5 (Fig. 4, not shown). The invention is stated to allow an increase by a factor of two or three of the upper limit frequency of the recurrent waveform as compared with known arrangements.