A pulse-and-bar waveform generator for testing television links

Among the test signals used for measuring the transmission performance of television links are `sine-squared¿ and `smoothed-bar¿ pulses. The paper gives details of the design of a test-signal generator which, at the line-frequency repetition rate, produces a composite waveform consisting of a sine-squared pulse, a smoothed-bar pulse and a normal line-synchronizing pulse. The sine-squared pulse may have a half-amplitude duration of either T or 2T, as selected by a switch, where 1/2T is the nominal upper frequency of interest in the television system (e.g. 3Mc/s in the British 405-line system). The bar pulse has a duration of approximately one-half of the line period and has transitions of `integrated sine-squared¿ shape. To facilitate precise measurements the generator has been designed with particular emphasis on stability of waveform shape and freedom from jitter. Consideration is also given to analogous test signals for colour-television systems.