Magnitude Of Jitter Research Articles

Binaural time discrimination

The least discriminable change in the position of a sound image was measured for pure tone with and without initial interaural delay, as well as for complex tones. The signals were either perfectly regular or jittered. The introduction of jitter allowed the subjects to lateralize equal-amplitude tones beyond 1500 Hz, which has been assumed to represent the limit for binaural phase discrimination. No frequency limit for jittered tones either in a fixed relationship or as binaural beats could be found. The smallest deviation from regularity employed was 0.2 μsec, and under certain conditions it was effective in producing lateralization. With no jitter in one ear, jitter in the other ear was ineffective. For a given high-frequency jittered tone, discrimination improves up to a limit with level and jitter magnitude. Complex tones, jittered and unjittered, show smaller just-noticeable differences for low and medium frequencies. Some other implications of these findings are discussed. A striking similarity between the curves for binaural time discrimination and those for pitch discrimination was found. Subject Classification: [43]65.68, [43]65.62, [43]65.60.

Frequency control using binary rate multipliers for automatic testing on c.w. radar systems

R.F. signals with certain defined characteristics have to be generated for ground testing on f.m. c.w. radar airborne-guidance systems. Normally in flight, two r.f. signals would be received; one direct from the ground transmitter and the other originating at the same transmitter, but reflected from a target. A lowfrequency wide-deviation frequency modulator is applied to the carrier at the ground transmitter. Owing to a difference in the path lengths of the two signals, a difference in phase angle of the modulating signal results, and, owing to the Doppler effect, the carrier frequencies are slightly separated. For testing therefore two r.f. signals with a precise and variable difference frequency have to be generated. Also both signals must be frequency modulated at the same frequency to the same deviation, but with a variable phase angle between the two modulating signals. For this purpose, a study has been made of the behaviour of binary rate multipliers used partly to shift the frequency, and partly to frequency modulate the r.f. carriers. A common crystal oscillator would feed into two b.r.m.s each shifting the carrier by a different amount, and each frequency modulating the shifted carriers with the same deviation. The b.r.m. operates by removing pulses from an uninterrupted pulse train according to the digital address. Thus the mean output frequency is lower than the input, but is contaminated with phase jitter. Jitter magnitude varies considerably with the address pattern, and it increases with the number of address lines. A graph of maximum jitter is given for increasing numbers of address lines up to 13. It isshown how phase jitter may be reduced to an acceptable limit, and how a system to meet the requirements may be designed.

Angular Jitter in Conventional Conical-Scanning, Automatic-Tracking Radar Systems

Four sources of angular jitter in a conventional conical-scanning, automatic-tracking radar are discussed and each is expressed in terms of range and the several system parameters. The total-angular-jitter-versus-range curve is shown to have a characteristic shape exhibiting a certain range interval of optimum tracking. The importance of beamwidth in determining the magnitude of angular jitter is also stressed.