D. J. Edwards

Bio: D. J. Edwards is an academic researcher. The author has contributed to research in topics: Phase-locked loop & Transponder. The author has an hindex of 1, co-authored 2 publications receiving 2 citations.

Amplitude modulation and the first-order phase-locked loop

Abstract: The behaviour of a first-order phase-locked loop is critically examined under conditions where it is tracking a carrier corrupted by discontinuous (square-wave) amplitude modulation. The transient response of the system is first derived for the simple case of a PLL without time delay, and a comparison is made with a series of practical results obtained from a first-order loop. The agreement between the predicted response and that observed in practice is found to be extremely good. The theoretical behaviour of the loop is further analysed for the case of a system incorporating time delay. It is shown that such delay is detrimental to the tracking performance of the loop, when it is necessary to track a carrier modulated in the manner outlined above.

Mobile terminal equipment design utilising split-loop phase-lock techniques

Abstract: The design and resultant performance of the terminal equipment in a mobile satellite system is vitally important in respect to the overall cost/performance compromise of the whole system. Improvements in system performance which also result in a reduction of the equipment cost are rare. However, this paper details a significant advance in terminal design, utilizing a novel form of 'split-loop' phase locked receiver/downconverter system to enable an accurate, stable and wide coverage terminal to be realized at a reduced cost. The system has the capability of automatically locking onto any carrier within a complete transponder, and can cope with severe amplitude modulation and fading effects.