Theoretical Fundamentals of Pulse Transmission - II

Impulse Characteristics and Pulse Train Envelopes Transmission Limitations in Symmetrical Systems Transmission Limitations in Asymmetrical Sideband Systems Double vs. Vestigial Sideband Systems Limitation on Channel Capacity by Characteristic Distortion Acknowledgements References 987 991 996 1004 1007 1010 1010 Part I of this paper dealt with various idealized transmission characteristics and with methods of evaluating pulse distortion resulting from various system imperfections. In Part II the resultant transmission impairments or limitations on pidse transmission rates are discussed for systems with lowpass, symmetrical band-pass and asymmetrical band-pass characteristics, and a comparison made of the transmission performance of double and vestigial sideband systems. The limitation on channel capacity imposed by random imperfections in the transmission-frequency characteristic, as compared to random noise, is also discussed. 12. IMPULSE CHARACTERISTICS AND PULSE T R A I N ENVELOPES In pulse modulation systems pulses are transmitted in various combinations to form pulse trains, and at the receiving end the envelope of the pulse train is sampled at regular intervals to determine the amplitudes of the transmitted pulses. As a result of pulse overlaps there may be appreciable distortion of the pulse train envelope, which may cause errors in reception or noise, depending on the type of system. To evaluate transmission impairments, or limitations imposed on transmission capacity to avoid excessive transmission impairments from pulse distortion, it is necessary to establish basic relations between the impulse characteristic of the system and the envelope of the received pulse train.