Masters Theses

Hiroyuki Iga

Date of Award

12-1987

Degree Type

Thesis

Degree Name

Master of Science

Major

Electrical Engineering

Major Professor

James C. Hung

Abstract

A new hybrid Phase-Locked Loop (PLL) synchronous video detector for a television receiver was developed. It contains a new hybrid PLL using a conventional analog PLL synchronous video detector. It has three modes, namely, the analog PLL mode in the initial step, the hybrid PLL continuous (C) mode in the intermediate step, and the hybrid PLL sample and hold (S/H) mode in the last step. The new detector with the precise sample and hold function eliminates the phase fluctuation caused by the heavy ghost signal with a power ratio to the main signal larger than -15 dB. The ghost signal is a reflected signal by a high building or other large object and results in the double-image interference. Thus, the new detector helps to reduce the ghost signal, enabling the ghost reduction system to function better.

Only the hybrid PLL was analyzed, since the remaining part of the detector can be designed by conventional methods. Design equations were derived from this study, and the results given by these equations were close to those obtained from the computer analysis. FORTRAN and ACSL (Advanced Continuous Simulation Language) were used for the computer analysis.

From a specified set of possible physical conditions and the results obtained through the analysis, a stable and practical hybrid PLL was obtained. The required resolution of the detector's A/D converter was 8 bit/V, and that of its D/A was 16 bit/V. Its output phase jitter for moderate input signal-to-noise ratio (37 dB) was 0.091 deg for the C mode and 0.26 deg for the S/H mode. Its pull-in time for the C mode was 97 ms for 500.0 kHz step frequency change. Its pull-in time for the S/H mode was 1.2 ms for 10.0 kHz step frequency change. Its output phase drift for an input signal-to-noise ratio of 37 dB was 1.0 deg for the S/H mode. This value is considerably smaller than the phase fluctuation of the corresponding analog PLL because of the heavy ghost (delay of 10 μs and phase of 180 deg). This conventional analog PLL has a phase fluctuation of 11.5 deg or 3.6 deg, depending upon the characteristics of the PLL. Improved phase fluctuation makes the detector more practical and satisfactory, especially in eliminating ghost interference.

The parameter values shown in this study are only for one example. However, for any set of given conditions, the suitable parameter values to realize a specific hybrid PLL synchronous video detector can be obtained from the equations derived in this study and the computer analysis.

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