Engineering topics
Publications and source records attributed to Gevargiz, John M..
Report presents analysis of three digital-matched-filtering schemes involving weighted integrate-and-dump filters (WDIF's) and considered for use in advanced digital radio receivers.
Method of optimization devised for use in selecting frequencies, powers, modulation indices, and other parameters of two digital-data telemetry channels and coherent turnaround ranging channel of Earth-station/satellite communication system. Also applicable to design of terrestrial communication systems based on similar modulation schemes and present similar design problems.
A simulation algorithm was developed to analyze the performance of the binary phase shift key (BPSK) Costas loop coupled to the symbol sync loop (SSL). Analysis was performed for various signal-to-noise ratios and loop parameters.
This paper presents a simple technique to design a phase-modulated residual carrier communications link for optimum performance. The emphasis is on two data channels which are operated simultaneously with a ranging signal. The data channels employ PCM/PM and PCM/PSK/PM modulation schemes for high and low data rate channels, respectively. The technique proposed here selects the optimum (1) subcarrier frequency to minimize the interference between the two data channels, and (2) modulation indices for optimum balance of power between the two telemetry data channels and the coherent turn around ranging channel. The selected set of optimum modulation indices will allow for the specified bit error rate (BER) degradations in the two data channels. Although this technique is proposed to optimize the performance degradation for two data channels, generalizations can be made for more than two data channels.
The authors present a novel algorithm to design a phase-modulated residual carrier communications system for optimum performance. The algorithm has been developed as an aid in the design of two telemetry data channels operating simultaneously with a turn-around ranging signal. The algorithm provides the selection of an optimum subcarrier frequency and modulation indices for minimizing the mutual interferences among the channels to achieve desired link performance margins. The set of modulation indices provided by this algorithm will also achieve an optimum power division between the carrier, the ranging and the high data rate and low data rate channels. Finally, a software program using this algorithm has been developed for use with personal computers. This program provides the computation of the optimum subcarrier frequencies and modulation indices for a standard case that is recommended by the international Consultative Committee for Space Data Systems.
The authors describe simulation and analytical techniques for predicting the interference durations and protection ratios for deep-space ground stations from satellites in circular orbits. The simulation approach employs the characteristics of the ground station receivers in addition to the satellite specifications to calculate the daily statistics of the interference duration. On the other hand, the analytical method employs the ground station specifications to statistically predict the protection ratios as a function of the number of interference satellites and their associated probabilities. The results presented here can be used for both planning the missions and designing satellite communication links. The results can be also be used by spectrum managers and operations personnel to minimize the risk of harmful interference from satellites in low earth orbit to the deep space frequency band.