New strategies for low noise, agile PLL frequency synthesis

Phase-Locked Loop based frequency synthesis is an essential technique employed in wireless communication systems for local oscillator generation. The ultimate goal in any design of frequency synthesisers is to generate precise and stable output frequencies with fast switching and minimal spurious and phase noise. The conflict between high resolution and fast switching leads to two separate integer synthesisers to satisfy critical system requirements. This thesis concerns a new sigma-delta fractional-N synthesiser design which is able to be directly modulated at high data rates while simultaneously achieving good noise performance. Measured results from a prototype indicate that fast switching, low noise and spurious free spectra are achieved for most covered frequencies. The phase noise of the unmodulated synthesiser was measured −113 dBc/Hz at 100 kHz offset from the carrier. The intermodulation effect in synthesisers is capable of producing a family of spurious components of identical form to fractional spurs caused in quantisation process. This effect directly introduces high spurs on some channels of the synthesiser output. Numerical and analytic results describing this effect are presented and amplitude and distribution of the resulting fractional spurs are predicted and validated against simulated and measured results. Finally an experimental arrangement, based on a phase compensation technique, is presented demonstrating significant suppression of intermodulation-borne spurs. A new technique, pre-distortion noise shaping, is proposed to dramatically reduce the impact of fractional spurs in fractional-N synthesisers. The key innovation is the introduction in the bitstream generation process of carefully-chosen set of components at identical offset frequencies and amplitudes and in anti-phase with the principal fractional spurs. These signals are used to modify the Σ-Δ noise shaping, so that fractional spurs are effectively cancelled. This approach can be highly effective in improving spectral purity and reduction of spurious components caused by the Σ-Δ modulator, quantisation noise, intermodulation effects and any other circuit factors. The spur cancellation is achieved in the digital part of the synthesiser without introducing additional circuitry. This technique has been convincingly demonstrated by simulated and experimental results

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Space Communications: Theory and Applications. Volume 3: Information Processing and Advanced Techniques. A Bibliography, 1958 - 1963

Annotated bibliography on information processing and advanced communication techniques - theory and applications of space communication

On the multistage design of optimal-NTF ΔΣ modulators-The case of fractional synthesizers

Digital ΔΣ modulators can be conveniently implemented as multi-stage noise shaping (MASH) architectures whenever some power of the first-difference differentiator is acceptable as the noise transfer function (NTF). Yet, other types of NTF can be more performant in some applications. In fact, strategies for a full adaptation of the NTF to the modulator environment have recently been studied. In this work, the possibility of implementing such optimized NTFs with MASH setups is considered. Although stability cannot be guaranteed as in conventional MASH designs, splitting the modulator in stages can still provide advantages. The case of fractional frequency synthesizers is taken as an example. Through the discussion, an empirical invariant on the overall number of output levels required for stable operation is identified

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 14)

This issue of the Index Section contains entries for 3512 patent and applications for patent citations covering the period May 1969 through December 1978. The Index Section contains five indexes --- subject, inventor, source, number, and accession number

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 34)

A subject index is provided for over 4600 patents and patent applications for the period May 1969 through December 1988. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 31)

A subject index is provided for over 4600 patents and patent applications for the period May 1969 through June 1987. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, and NASA accession numbers

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 37)

A subject index is provided for over 4600 patents and patent applications for the period May 1969 through June 1990. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers