A literature search was conducted in an effort to collect and compile as many references on the phase-locked loop as possible. Although not all inclusive, a comprehensive listing of approximately 800 references covering the past two decades of work reported throughout the world are presented. The compilation is given in two parts: first by categories, and then alphabetically by authors.

A bibliography of the theory and application of the phase-lock principle

An analysis is presented of the performance of phaselocked timing extraction circuits for baseband pulse code transmission. The phase error of the extracted timing wave is influenced by the properties of three essential stages in signal processing: prefiltering, nonlinear treatment, and narrow-band filtering. The analysis enables us to calculate quantitatively the quasi-static and the dynamic part of the phase error for arbitrary but specified types of signal processing. This is more than can be done with existing theory in the case of resonant-type timing extraction circuits. Examples are given for practical cases, and conditions for optimum performance are derived. Furthermore, the behavior of such phase-locked circuits in a chain of repeaters is investigated, and in particular, the propagation law for jitter. Byrne's model, as used for resonant-type timing extraction circuits, therefore is generalized. It is shown analytically and experimentally that by proper implementation of the timing extraction circuit, considerable improvement can be obtained as compared with resonant-type circuits.

Analysis of Phase-Locked Timing Extraction Circuits for Pulse Code Transmission

Timing extraction through nonlinearity in the presence of pulse overlaps is studied for baseband PCM or PAM systems. It is shown that the systematic jitter can be reduced by proper choices of nonlinearity, coding scheme, and pulse waveform. Discussions on choice of nonlinearity indicate that square-law rectification is desirable for elimination of jitter sources. This nonlinearity derives a frequency-domain expression for amplitude and phase of the timing wave that separates the effects of pulse pattern and pulse shapes and provides insight to their contributions to timing jitter. Proper choices of coding scheme and pulse waveform reduce amplitude and phase variation in the timing wave. For example, an optimum prefiltering (or correlative coding) reduces amplitude variation to one eighth for bipolar sequence. In the case of symmetrical reshaping by a Bessel (flat delay) filter, the maximum jitter exceeds 20 degrees if the order of a filter is less than ten. An asymmetrical reshaping makes the maximum jitter less than four degrees for the same order of filter. Some features of nonlinearities that approximate square-law rectification are discussed.

Timing Extraction in Baseband Pulse Transmission

A new approach to the jitter accumulation problem in a chain of regenerative repeaters for pulse amplitude modulation systems is described. In each regeneration section the timing circuit consists of a square-law device followed by a bandpass filter with center frequency close to the transmission rate. It is shown that, from the standpoint of jitter generation and propagation, the timing circuit is equivalent to a low-pass filter driven by the sum of the jitter generated in the previous regenerator plus a noise term. This is actually the jitter propagation mechanism suggested in [6] and referred to as Chapman's model. What makes a difference with the results published in [6] is that in our analysis an expression is given for the spectral density of the noise in the equivalent model in terms of system parameters such as pulse shape, bandpass filter mistuning, offset in the triggering level of the pulse generator, etc. In this way the various jitter sources can be qualified and their effects evaluated.

Jitter Accumulation in PAM Systems

Unless proper control is exercised in limiting the amplitude of jitter in future digital networks, serious degradations can arise. The important sources of jitter are identified and described. Trie manner in which jitter accumulates in a digital network is discussed with particular emphasis being given to accumulation along transmission systems. A brief review is given of the current status of jitter studies within international organizations (CCITT and CEPT).† The jitter control and specification philosophy for digital networks and equipments based on the 2048-kbit/s hierarchy is outlined.

Jitter in digital telecommunication networks

This paper describes methods for the simultaneous transmission of information signals and pseudonoise synchronization waveforms in a common bandwidth. For a relatively low level of the pseudonoise signal, a satisfactorily high synchronization accuracy is obtained by means of correlation techniques. Conversely, the information signal is detected with negligible interference due to the synchronization waveform. This permits a new approach to synchronization in speech systems and data transmission. The application to speech systems is quite straightforward. Emphasis is placed on design considerations for narrow-band systems with regard to output signal-to-noise ratio and acquisition performance. In data transmission the method is applied for bit and word synchronization. Thus, no restrictions are imposed on the transmitted data patterns and no inclusion of special synchronization words is required. In addition, the bandwidth of the system is not increased. The high accuracy required for synchronization in data systems is obtained here by a pseudoternary precoding of the transmitted data which is adapted to the spectral properties of the synchronization cross correlator. In this way the influence of the data signal on the received synchronization signal is minimized. Calculations of synchronization accuracy are given which include the effect of transmission noise.

Common Bandwidth Tranmission of Information Signals and Pseudonoise Synchronization Waveforms

This paper describes methods for the reduction of jitter in transmission chains with regenerative repeaters. These methods are based on the application of pattern transformations to the output signals of successive repeaters. As a result, the coherent accumulation of jitter from signal dependent jitter sources is prevented. Instead, the jitter accumulates on a power basis. It is shown that in this way a significant reduction of jitter is obtained. This result is demonstrated by both theoretical data and measurements on an experimental transmission chain which correspond fairly closely. Furthermore, the realization of the pattern transformations by simple coding techniques is presented in detail.

The Reduction of Systematic Jitter in a Transmission Chain with Digital Regenerators

Digital transmission for existing standard FM mobile radio sets is discussed. The transmission properties of such standard sets are presented. Various data pre-encoding techniques and the corresponding decoders are considered and their performances compared, The comparison includes consideration of the radiated FM spectra, the measured bit error rate curves, and the necessary complexity.

L. Zegers

Papers

Common Bandwidth Tranmission of Information Signals and Pseudonoise Synchronization Waveforms

The Reduction of Systematic Jitter in a Transmission Chain with Digital Regenerators

A Comparison of Digital Transmission Techniques for Standard FM Mobile Radio Sets