Engineering evaluations and studies. Volume 2: Exhibit B, part 1

Ku-band communication system analysis, S-band system investigations, payload communication investigations, shuttle/TDRSS and GSTDN compatibility analysis are discussed

REAL TIME MICROPROCESSOR TECHNIQUES FOR A DIGITAL MULTITRACK TAPE RECORDER

Transport properties of a standard compact - cassette tape system are measured and software techniques devised to configure a low - cost,direct digital recording system. Tape - velocity variation is typically ± 10% of standard speed over tape lengths of 5 µm.with occasional variations of ±40%. Static tape - skew can result due to axial movement of the tape reel when it spools.Dynamic tape skew occurs and is primarily caused by tape - edge curvature with a constant contribution due to the transport mechanism.Spectral skew components range from 0.32 Hz to 8 Hz with magnitude normally within one 10 kbit/ sec- bit cell.The pinch roller works against the friction of the tape guides to cause tape deformation.Average values of tape deformation are 0.67 µm,0.85 µm and 1.08 µm for C60,C90 and C120 tape respectively. Parallel,software encoding / decoding algorithms have been developed for several channel codes.Adaptive software methods permit track data rates up to 3.33 k bits/sec in a rnultitrack system using a simple microcomputer.For a 4 - track system,raw error rates vary from 10ˉ⁷ at 500 bits/sec/track to 10ˉ⁵ at 3.33 kbits/sec/track.Adaptive software reduces skew - induced errors by 50%.A skew - correction technique has been developed and implemented on an 8 - track system at a track data rate of 10 k bits/sec. Real - time error correction gives a theoretical corrected error rate of 10ˉ¹¹for a raw error rate of 10ˉ⁷. Multiple track errors can cause mis - correction and interleaving is advised. Software algorithms have been devised for Reed - Solomon code. With a more powerful microprocessor this code m ay be combined with the above techniques in a layered error-correction scheme. The software techniques developed may be applied to N tracks with an N - bit computer.Recording density may be increased by using thin - film,multitrack heads and a faster computer.British Broadcasting Corporatio

A study of correlation of sequences.

by Wai Ho Mow.Thesis (Ph.D.)--Chinese University of Hong Kong, 1993.Includes bibliographical references (leaves 116-124).Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Spread Spectrum Technique --- p.2Chapter 1.1.1 --- Pulse Compression Radars --- p.3Chapter 1.1.2 --- Spread Spectrum Multiple Access Systems --- p.6Chapter 1.2 --- Definitions and Notations --- p.8Chapter 1.3 --- Organization of this Thesis --- p.12Chapter 2 --- Lower Bounds on Correlation of Sequences --- p.15Chapter 2.1 --- Welch's Lower Bounds and Sarwate's Generalization --- p.16Chapter 2.2 --- A New Construction and Bounds on Odd Correlation --- p.23Chapter 2.3 --- Known Sequence Sets Touching the Correlation Bounds --- p.26Chapter 2.4 --- Remarks on Other Bounds --- p.27Chapter 3 --- Perfect Polyphase Sequences: A Unified Approach --- p.29Chapter 3.1 --- Generalized Bent Functions and Perfect Polyphase Sequences --- p.30Chapter 3.2 --- The General Construction of Chung and Kumar --- p.32Chapter 3.3 --- Classification of Known Constructions ...........； --- p.34Chapter 3.4 --- A Unified Construction --- p.39Chapter 3.5 --- Desired Properties of Sequences --- p.41Chapter 3.6 --- Proof of the Main Theorem --- p.45Chapter 3.7 --- Counting the Number of Perfect Polyphase Sequences --- p.49Chapter 3.8 --- Results of Exhaustive Searches --- p.53Chapter 3.9 --- A New Conjecture and Its Implications --- p.55Chapter 3.10 --- Sets of Perfect Polyphase Sequences --- p.58Chapter 4 --- Aperiodic Autocorrelation of Generalized P3/P4 Codes --- p.61Chapter 4.1 --- Some Famous Polyphase Pulse Compression Codes --- p.62Chapter 4.2 --- Generalized P3/P4 Codes --- p.65Chapter 4.3 --- Asymptotic Peak-to-Side-Peak Ratio --- p.66Chapter 4.4 --- Lower Bounds on Peak-to-Side-Peak Ratio --- p.67Chapter 4.5 --- Even-Odd Transformation and Phase Alphabet --- p.70Chapter 5 --- Upper Bounds on Partial Exponential Sums --- p.77Chapter 5.1 --- Gauss-like Exponential Sums --- p.77Chapter 5.1.1 --- Background --- p.79Chapter 5.1.2 --- Symmetry of gL(m) and hL(m) --- p.80Chapter 5.1.3 --- Characterization on the First Quarter of gL(m) --- p.83Chapter 5.1.4 --- Characterization on the First Quarter of hL(m) --- p.90Chapter 5.1.5 --- Bounds on the Diameters of GL(m) and HL(m) --- p.94Chapter 5.2 --- More General Exponential Sums --- p.98Chapter 5.2.1 --- A Result of van der Corput --- p.99Chapter 6 --- McEliece's Open Problem on Minimax Aperiodic Correlation --- p.102Chapter 6.1 --- Statement of the Problem --- p.102Chapter 6.2 --- A Set of Two Sequences --- p.105Chapter 6.3 --- A Set of K Sequences --- p.110Chapter 7 --- Conclusion --- p.113Bibliography --- p.12

A unified approach to the analysis and design of digital line codes

In most areas of research the variety of possible approaches to analysis and design problems is very large. This is particularly true in the case of digital signal transmission where various conflicting requirements exist (e.g. minimum bandwidth for maximum information capacity and reliability). The lack of universally adopted analysis and evaluation methods is not due to any uncertainties or deficiencies in theoretical fundamentals, rather it is a problem of diversity of criteria and therefore modes of specification that apply. The work presented in the thesis is concerned with the creation and evaluation of a universal algorithm suitable for the assessment of digital codes together with a systematic approach to the comparative evaluation of essential structural and spectral features of coding schemes. The thesis begins with an overview of the basic theoretical principles of line coding as an essential part of the process of channel coding for reliable and efficient digital signal transmission. A general spectral analysis procedure is derived from the finite-state sequential machine model of fixed-length block coders, and is implemented in the form of a computer program. A technique for the conversion of coder rules, given in descriptive form into table and matrix form, suitable for the universal specification format used in the general spectral analysis procedure, is developed. A new method of general classification of codes into categories, according to their complexity levels, is proposed. A modification of the spectral analysis routine into a universal block-code generating scheme is then introduced. The virtually unlimited capabilities for the design and analysis of new code structures is demonstrated. Following from this, a new method for evaluation of the performance of block codes is suggested. It is based on the introduction of an integral parameter, the Information Capacity, which determines the degree of possible spectrum modification for a particular coder specification. Using this method, it is demonstrated how an optimal combination of a code structure, spectral features and information capacity can be achieved. The thesis concludes with a practical example of the application of the generalised analysis procedure, demonstrating the possibility to combine code multiplexing with modification of the spectrum of the line signal. A novel technique, based on the principles of spread spectrum for multichannel transmission, is proposed. It involves a Binary-Multiplexed Coding (BMC) scheme which is implemented in a generalised circuit, the performance of which is investigated and evaluated

Study of modulation techniques for multiple access satellite communications

Multiple access communication utilizing small ground stations for satellite communication modulation - multiplexing technique

Development of an infrared analyzer following the

A radar calibration subsystem for measuring the radar backscattering characteristics of an imaged terrain is described. To achieve the required accuracy for the backscattering coefficient measurement (about 2 dB with 80 percent confidence), the space hardware design includes a means of monitoring the state parameters of the radar. For example, the transmitter output power is sampled and a replica of its output waveform is circulated through the receiver. These are recorded digitally and are used on the ground to determine such radar parameters as the transmitter power and the receiver gain. This part of the data is needed by the ground processor to measure the terrain backscattering characteristics