S.R. Kharbanda

Bio: S.R. Kharbanda is an academic researcher. The author has contributed to research in topics: Antenna (radio) & Transmitter. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

A method of transmitting sound on the vision carrier of a television system

Abstract: The paper describes a television system in which sound pulses having a constant height and variable width are inserted in the line synchronizing periods. It is claimed that this method of transmission leads to a simplified receiver and that the programme quality is better in the presence of severe interference. Other advantages are that the frequency band-width for transmission is reduced; the method of receiving sound ensures automatic volume control; the sound pulses provide a fixed reference level for automatic volume control on the vision channel; mutual interference between vision and sound often present on two-channel reception is avoided; reduced transmission band-width simplifies the design of the receiving antenna; mutual coupling between the vision and sound antennae at the transmitter is avoided; and the installation and maintenance costs of the sound transmitter are saved. The frequency range of the system operated in conjunction with the pre-war British transmission would be limited to 5 kc/s.

The spectrum of modulated pulses

Abstract: Some methods proposed for evaluating the spectra of modulated pulse trains are discussed. The basic pulse-frequency, -phase, -length and -amplitude modulation systems are defined and the spectrum of a train of rectangular pulses sinusoidally modulated in any one of these ways is derived. Modulation by more than one tone is also considered. It is shown that in none of these methods is there any harmonic distortion or audio crosstalk. Anharmonic distortion arises from sidebands of harmonics of the pulse repetition frequency, and graphs are given to illustrate its magnitude. The formulae are extended to cover non-rectangular pulses, and it is shown that the distortions to be expected are practically the same as for rectangular pulses. The reproduction of transients is briefly examined. It seems that they suffer little distortion in form but that their timing is modified by the pulse modulation, the maximum time-shift being half the pulse repetition period.

Noise problems in pulse communication

Abstract: Formulae for random noise in the audio-frequency output in pulse-communication receivers are given for pulse-length-, pulse-phase- and pulse-frequency-modulation systems in which the received pulses are sliced; they are also given for pulse-amplitude modulation. Noise resulting from random distribution of the i.f. phase at the onset of pulses is also considered. Optimum slicing level giving minimum output noise is evaluated.Signal/noise ratio and threshold formulae are obtained from these data for the pulse-modulation systems and are compared with those for conventional amplitude- and frequency-modulation systems having the same mean or peak power. Final conclusions as to the merits of all the above systems are drawn from graphs of output signal/noise ratio, in which the performance below threshold is also taken into account.

Random noise characteristics of a pulse-length-modulated system of communication

Abstract: The paper deals with a theoretical analysis of the random noise characteristics of a pulse-length-modulated system of communication. The result is demonstrated by two different methods, one of which is rigorous and based on the frequency spectrum of a rectangular pulse, while the other is an approximation based upon calculation of the average value of the pulse waveform, plus noise, integrated over a period of time that is short compared with a cycle of the a.f. cut off frequency.