Browsing International Telemetering Conference Proceedings, Volume 01 (1965) by Issue Date
Now showing items 1-20 of 55
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Conditioning and Recovery of Aircraft Position Signals Through an Existing Data LinkA Signal Data Converter system records aircraft present po t on and altitude data on film and also displays this data in a ground shelter, allowing for real time surveillance by a ground observer. This is accomplished by adapting a unique digital data transmission system to an existing infrared video data link.
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Recent Developments Pertaining to Solid-State S-Band TransmittersThis paper discusses the performance of some recent R. F. power transistors as frequency multipliers and relates this information to their use in solid state V. H. F. and U. H. F. Telemetry Transmitters. The step-recovery diode is - similarly discussed. Both devices are shown to have great promise for ultimately lowering the complexity, size, and price of Solid State S Band and L Band Telemetry Transmitters.
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International Telemetering Conference Proceedings, Volume 01 (1965)International Foundation for Telemetering, 1965-05
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Evaluation of an Expanded FM/FM Baseband StructureAn experimental evaluation program was undertaken to investigate the feasibility of expanding the IRIG (Inter-Range Instrumentation Group) FM/FM baseband. The results of the evaluation indicate that with typical field equipment, three higher-frequency proportional-bandwidth channels can be added to the baseband while maintaining adequate system performance.
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A Low Level Commutator with Field Effect Transistor Signal GatesA low level differential input commutator is described which uses field effect transistors for the signal gates. The commutator was built for airborne applications so that size, weight, and reliability were major considerations as well as electrical performance. Results are compared with commutators using other types of signal gates.
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Design and Performance of a New S-Band TransmitterThis paper describes a telemetry transmitter designed for the 2.2-2.3 Gc band. Design philosophy followed to achieve minimum size, wide deviation capability, high reliability and high efficiency are discussed in detail. The paper presents extensive measured data to indicate achievement of design goals set by IRIG 106-60 and ARTC-34. Construction details of the transmitter are illustrated.
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Frequency Spectrum of an FM/FM SignalSeveral authors have attempted to derive a mathematical model that will describe the frequency spectrum of a FM/FM signal. However, to this author's knowledge, none of the mathematical models that have been published is valid when the carrier is modulated by more than one subcarrier. In this paper an expression for a FM/FM signal is derived that is valid when IRIG specifications are applied. Then this expression is manipulated into a form that will yield the frequency spectrum when the carrier is modulated by any number of subcarriers. Then an illustration of a two subcarrier frequency spectrum is presented.
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F. M. Capture Performance - Characterization and MeasurementThe effects of interference and capture in FM reception are reviewed for the purpose of determining the basis for characterizing and measuring the capture performance of FM receivers. Capture performance criteria and performance measurement techniques are proposed for application to FM telemetry receiver evaluation.
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Design Considerations in Pre-D Receiving and Recording EquipmentDesign factors to be considered in wide band Pre-D recording and playback equipment for usage in a versatile Pre-D system are presented. These design factors are introduced in a discussion of both the down-translator and up-translator. The mechanisms which produce spurious outputs from the up-translator and the effects caused by these spurious outputs are treated in detail. The extension of Pre-D techniques to FM Electronics equipment is covered.
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A New Approach to Effective Digital Filter DesignIn this paper the effect of modifying digital filter weights derived on a least squares error basis through multiplication by certain weighting functions is investigated. It is shown that this approach amounts to adopting frequency resolution as a filter performance criterion, in a manner analogous to resolution in spectral estimates along the lines of Blackman and Tukey. Weight formulation using the method is very simple, and working transfer functions are easily estimated without computation. Simple, effective designs are presented for low, high and band-pass (or band-stop) filters of the "cosine" or in-phase type, for cosine "low low-pass" and "sampling" filters, and for "sine" or quadrature "sampling" filters, as well as differentiators.
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Subminiature Inductive Transducers used with High Carrier FrequenciesThis paper describes the development and construction of subminiature inductive transducers which can be operated with carrier frequencies up to 400 Kcs. Two types have been developed for operation at 150°C which are able to withstand an acceleration of 2000g, and a high-temperature (600°C) transducer is now in the final stage of development. The body of the low-temperature transducer is made of high-temperature epoxy resin, and that of the high-temperature transducer of ceramic material. Iron wire is used as core material to reduce eddy current losses. The dimensions of the transducers are 0.25 inch diameter and 0.5 inch long, and 0.125 inch diameter and 0.25 inch long, including terminations. A linear displacement of the armature material can be measured at distances up to 0.01 inch, and because of the high carrier frequency, the vibration of this armature can be up to 30 Kcs. Both ferrous and non-ferrous armature material can be used for displacement measurement. The inductive transducers have been used to measure piston movement at right angles to the cylinder axis in an internal combustion engine, in conjunction with a lead-out system. Tests using a telemetry system (radio link) are now being carried out. Details of the construction and performance are described and future development discussed. The use of the inductive transducer as a pressure transducer is also mentioned.
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Propagation Characteristics of the Space ChannelA discussion is provided of the propagation phenomena, and their associated disturbances, that have been observed to cause significant degradation of the performance of space instrumentation and communication links.
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Application of a Telemetry System using DSB-AM Sub-CarriersThe advantages of the DSB-AM subcarrier for wideband telemetry requirements have been discussed in previous papers. The purpose of this paper is to consider the specific performance of an FM telemetry r-f link when modulated by a frequency multiplex of DSB subcarriers. The performance is evaluated by constructing an appropriate model of the subcarrier multiplex based on a predicted noise power spectrum at the r-f demodulator output. The model is used to specify the individual subcarrier amplitude values that constitute the baseband signal, which will modulate the FM transmitter. The carrier power required to produce a useful signal-to-noise ratio at the outputs of the individual subcarrier demodulators is considered in general. The relationship between the degree of transmitter deviation, receiver bandwidth and the carrier power is derived. The carrier power required for operation over typical test range distances is determined in terms of the appropriate variables. The performance of two specific examples is calculated to illustrate the use of the several formulae that are derived. The examples also serve to relate and compare the performance of the DSB system configurations to the more traditional applications. Finally, the advantage of using increased r-f bandwidth is discussed.
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Matched Filter Systems in Rising Noise SpectrumsIt is common knowledge that the matched filters for signals in white noise have impulse responses whose time duration is exactly as long as that of the input signal. Nothing can be gained by extending the response of the matched filters to longer than one bit unless (1) the signal source is coded, or (2) the noise spectrum is rising or at least is other than white-Gaussian-ergodic. This paper discusses means of improving bit error rates without coding the source. There are essentially two ways of extending the integration time of the matched filters, each of which offers an improvement in signal-to-noise ratio. The first way is to extend the response directly to more than one bit but constrain the filter to give zero or some small pre-assigned intersymbol crosstalk. The second way is to build matched filters for multiple bits. Both techniques can be used simultaneously; i.e., matched filters can be constructed for bit patterns, and the responses can be extended to longer than the baud to which the filters are matched. Once again this extension is done under the constrain of zero or little crosstalk. In this paper, the matched filters for several examples are expanded in a rapidly converging series, each term of which is identifiable with a known network. For the cases where the shape of the noise is not known analytically, an experimental technique is given for determining sufficient statistics of the noise so that the optimum matched filters can be designed.