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Space Electronics and Telemetry, IRE Transactions on

Issue 3 • Date Sept. 1962

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Displaying Results 1 - 10 of 10
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • IRE Professional Group on Space Electronics and Telemetry

    Page(s): nil1
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    Freely Available from IEEE
  • [Breaker page]

    Page(s): nil1
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    Freely Available from IEEE
  • Delay Variations in Telemetry Filters

    Page(s): 199 - 204
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    The significance of filter delay characteristics in telemetry applications is discussed, and fundamental terms are defined. Suggested methods of delay measurement are presented, and experimental results are given. Recommendations are offered regarding filter specifications. View full abstract»

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  • A Telemetering System by Code Modulation - Δ- ΣModulation

    Page(s): 204 - 209
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    A communication system by code modulation is described which incorporates an integration process in the original delta modulation system and is named delta-sigma modulation after its modulation mechanism. It has an advantage over delta modulation in dc level transmission and stability of performance, although both require essentially an equal bandwidth and complexity of circuitry. An experimental telemetering system employing delta-sigma modulation is also described. View full abstract»

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  • Phase-Lock Loop Frequency Acquisition Study

    Page(s): 210 - 227
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    The ability of a phase-lock loop using a proportional plus integral control filter to acquire a noisy signal when the local oscillator is being swept was determined empirically by means of a low-frequency, GEESE1 model of such a system. The effects of the damping factor and natural frequency on the frequency acquisition properties of linear loops (as distinguished from a loop in which the IF signal is limited) are considered in this study. In addition, consideration is given to a loop in which the IF signal is ``hard'' limited and the loop designed to maximize the sweep rate under the constraint that the probability of acquisition is equal to or greater than 90 per cent for a given SNR. The rms phase jitter in the output signal was measured as a method of verifying the standard analytic approach to predicting phase jitter. The results of the study are as follows: 1) The range of damping factors from 0.5 to 0.85 yields near optimum acquisition performance. 2) Although a drop in loop gain produces lower phase jitter for a given (S/N)IF, it degrades the over-all ability of the loop to acquire and track a signal. 3) A ``hard'' limiter in the IF can be effectively used as a gain control to enhance loop performance. 4) Using an empirical formula derived from experimental results, the VCO sweep rate for 90 per cent probability of acquisition can be predicted accurately, given the (SNR)IF and loop parameters. View full abstract»

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  • Message Compression

    Page(s): 228 - 238
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    Two general classes of operations for the purpose of compressing the output of a message source are considered: (1) Entropy-reducing (ER) transformation, and (2) Information-preserving (IP) transformation (redundancy removal). The type (1) transformation, when acceptable, can yield substantial compression gains in telemetry applications while the type (2) transformation can yield substantial gains for certain types of source statistics. A new concept, adaptive coding, is introduced. It is shown that for quasi-stationary source statistics it is possible to obtain estimates of the statistics and to use these subsequently for efficient coding. A general statistical measure for monitoring the efficiency of the adaptive procedure is presented and a decision rule, based on this statistic, for updating the coding is defined. It is shown that the statistical estimates need not be precise since the coding efficiency remains reasonably insensitive to small errors; hence, only violent changes in the source statistics must be detected. A number of configurations for performing adaptive and non-adaptive compression are discussed in detail. Some of these procedures, such as predictive coding, are well known while others are new. In particular, a practical configuration is presented for compressing the output of many sensors which have the statistical structure; no changes in the signal for relatively long time intervals and very rapid changes for relatively short time intervals. It is concluded that this approach has the advantage over variable rate commutation procedures in that short message bursts can always be detected without increasing the communications channel capacity. View full abstract»

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  • Experimental Optimization and Evaluation of Telemetry Systems

    Page(s): 239 - 246
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    A careful laboratory program to experimentally optimize and evaluate four telemetry systems in wide use (FM-FM, PAM-FM, PDM-FM and PCM-FM) has been concluded as part of a general study of problems in the telemetry field. Each of the four systems was implemented in the laboratory and the system under test was modulated by random signal sources typifying actual data. Broad-band random noise was then introduced at the RF and the various system parameters were optimnized to obtain the lowest threshold for stated performance. Having optimized the parameters in this manner, performance against other types of interference was also measured. For each system an accurate error comparator was designed which repetitively sampled the system input and output and compared the samples for error. The information obtained on internal parameter optimization and over-all performance for each system is extremely useful to systems design as well as to evaluation and comparison of the systems. View full abstract»

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  • Contributors

    Page(s): 247 - 248
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  • [Front cover]

    Page(s): c2
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Aims & Scope

This Transactions ceased publication in 1962. The new retitled publication is IEEE Transactions on Aerospace and Electronic Systems.

Full Aims & Scope